tag:theconversation.com,2011:/global/topics/roundworms-2820/articlesRoundworms – The Conversation2023-08-29T03:58:29Ztag:theconversation.com,2011:article/2124372023-08-29T03:58:29Z2023-08-29T03:58:29ZFinding a live brain worm is rare. 4 ways to protect yourself from more common parasites<p><a href="https://www.theguardian.com/australia-news/2023/aug/28/live-worm-living-womans-brain-australia-depression-forgetfulness">News reports</a> this morning describe how shocked doctors removed a live worm from a woman’s brain in a Canberra hospital last year. The woman had previously been admitted to hospital with stomach symptoms, dry cough and night sweats and months later experienced depression and forgetfulness that led to a brain scan. </p>
<p>In the <a href="https://wwwnc.cdc.gov/eid/article/29/9/23-0351_article">case study</a> published in Emerging Infectious Diseases journal, doctors describe removing the live 8cm-long nematode (roundworm) from the brain of the 64-year-old woman who was immunosuppressed. The worm was identified as <em>O. robertsi</em> which is native to Australia, where it lives on carpet pythons. The woman may have come into contact with worm eggs via snake faeces while foraging for Warrigal greens to eat.</p>
<p>It’s important to note this is an extremely rare event and headlines about brain worms can be alarming. But there are more common parasites which can infect your body and brain. And there are ways you can minimise your risks of being infected with one. </p>
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<h2>Common parasites and how they get in</h2>
<p>Parasitic infection is extremely common. Arguably the most widespread type is pinworm (<em>Enterobius vermicularis</em> also called threadworm), which is thought to be present in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6522669/">over a billion people</a> worldwide, especially children. Pinworms grow to around 1cm in length and are specific to human hosts. They cause intense bottom itching and get passed from person-to-person. It’s a myth that you can get it from pets.</p>
<p><a href="https://www.cdc.gov/parasites/giardia/pathogen.html#:%7E:text=Giardia%20duodenalis%20is%20a%20protozoan,Giard%20of%20Paris%20and%20Dr.">Giardia</a> (<em>Giardia duodenalis</em>) is also very common and can contaminate food, water and surfaces. This water-borne parasite is associated with poor sanitation and causes stomach symptoms like diarrhoea, cramps, bloating, nausea and fatigue. Giardia cysts (little sacs of immature parasite) spread disease and are passed out in faeces, where they can remain viable in the environment for months before being consumed by someone else. They can also be ingested via foods (such as sheep meat) that is raw or undercooked.</p>
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Read more:
<a href="https://theconversation.com/health-check-the-low-down-on-worms-and-how-to-get-rid-of-them-36486">Health check: the low-down on 'worms' and how to get rid of them</a>
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<p><a href="https://www.cdc.gov/dpdx/hookworm/index.html">Two types</a> of hookworm – <em>Necator americanis</em> and <em>Ancylostoma duadonale</em> – are found in soil. Only <em>Ancylostoma duodenale</em> is an issue in Australia and is typically found in <a href="https://www.cdc.gov/dpdx/hookworm/index.html">remote communities</a>. </p>
<p>When a person is infected (usually via barefeet or contaminated footwear) these worms enter the bloodstream and then hit the lungs. From the bronchi in the upper lungs, they are swallowed with secretions. Once in the gut and small bowel they can <a href="https://www.who.int/news-room/fact-sheets/detail/soil-transmitted-helminth-infections#:%7E:text=Transmission,these%20eggs%20contaminate%20the%20soil.">cause anaemia</a> (low iron). This is because they are consuming nutrients and affecting iron absorption. They also release an anticoagulant that stops the human host’s blood clotting and causes tiny amounts of blood loss. </p>
<p>Fortunately, these very common parasites do not infect the brain. </p>
<p>Across the world, it’s estimated <a href="https://pubmed.ncbi.nlm.nih.gov/22491772/">30–50% of people</a> are infected with <em>Toxoplasma</em>. Most people will be asymptomatic but many carry the <a href="https://theconversation.com/one-in-three-people-are-infected-with-toxoplasma-parasite-and-the-clue-could-be-in-our-eyes-182418">signs of infection</a>. </p>
<p>The parasites can remain in the body for years as tiny tissue cysts. These cysts can be found in brain, heart and muscle. Infants can be born with serious eye or brain damage if their mothers are infected during pregnancy. People with compromised immunity – such as from AIDS or cancer treatment – are also at risk of illness from infection via pet cats or uncooked meat. </p>
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<a href="https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="person pats cat" src="https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/545183/original/file-20230829-21-sm0791.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Toxoplasmosis can be transmitted by cats.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hand-woman-petting-brown-cat-outside-1166422114">Shutterstock</a></span>
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Read more:
<a href="https://theconversation.com/one-in-three-people-are-infected-with-toxoplasma-parasite-and-the-clue-could-be-in-our-eyes-182418">One in three people are infected with _Toxoplasma_ parasite – and the clue could be in our eyes</a>
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<h2>Then there are tapeworms and amoebas</h2>
<p>Tapeworms can infect different parts of the body including the brain. This is called <a href="https://www.cdc.gov/parasites/resources/pdf/npis_in_us_neurocysticercosis.pdf">neurocysticercosis</a> and is the leading cause of epilepsy worldwide. Neurocysticercosis is uncommon in the Western world and infection is usually via eating pork that is uncooked or prepared by someone who is infected with tapeworm (<em>Taenia solium</em>). It is more likely in locations where pigs have contact with human faeces via sewerage or waterways. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="brain scan" src="https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=755&fit=crop&dpr=1 600w, https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=755&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=755&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=949&fit=crop&dpr=1 754w, https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=949&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/545182/original/file-20230829-17-vqey6e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=949&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A brain scan of someone infected with pork tapeworm.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/brain-ct-cysticercosis-larva-pork-tapeworm-1619246149">Shutterstock</a></span>
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<p>Tapeworm larvae can infect muscle and soft tissue. Brain tissue can provide a home for larvae because it is soft and easy to get to via blood vessels. Brain infection can cause headaches, dizziness, seizures, cognitive impairment and even dementia, due to an increase in <a href="https://www.cdc.gov/parasites/cysticercosis/gen_info/faqs.html">cerebral spinal fluid pressure</a>.</p>
<p><em><a href="https://www.cdc.gov/parasites/naegleria/general.html">Naegleria fowleri</a></em> is an amoeba found in lakes, rivers and springs in warm climates including <a href="https://www.sahealth.sa.gov.au/wps/wcm/connect/public+content/sa+health+internet/public+health/water+quality/naegleria+fowleri#:%7E:text=How%20common%20are%20Naegleria%20fowleri,frequently%20found%20in%20the%20environment.">in Australia</a>. People swimming in infected waters can have the parasite enter their body through the nose. It then travels to the brain and destroys brain tissue. The condition is <a href="https://www.cdc.gov/parasites/naegleria/general.html#:%7E:text=Top%20of%20Page-,What%20is%20the%20death%20rate%20for%20an%20infected%20person%20who,States%20from%201962%20to%202022.">almost always fatal</a>.</p>
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Read more:
<a href="https://theconversation.com/what-are-parasites-and-how-do-they-make-us-sick-121489">What are parasites and how do they make us sick?</a>
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<h2>Yikes! 4 ways to avoid parasitic infection</h2>
<p>That all sounds very scary. And we know being infected by a snake parasite is very rare – finding one alive in someone’s brain is even rarer. But parasites are all around us. To minimise your risk of infection you can:</p>
<p><strong>1.</strong> avoid undercooked or raw pork. Freezing meat first may reduce risks (though home freezers <a href="https://www.cdc.gov/parasites/trichinellosis/prevent.html">may not get cold enough</a>) and it must be cooked to a <a href="https://www.sciencedirect.com/science/article/pii/S0924224418301560#:%7E:text=and%20time%20conditions.-,Cooking%20at%20core%20temperature%2060%E2%80%9375%20%C2%B0C%20for%2015,relied%20upon%20in%20home%20situations.">high internal temperature</a>. Avoid pork if you are travelling in places with poor sanitation</p>
<p><strong>2.</strong> avoid jumping or diving into warm fresh bodies of water, especially if they are known to carry <em>Naegleria fowleri</em>. Although only a <a href="https://www.cdc.gov/parasites/naegleria/graphs.html">handful of cases</a> are reported each year, you should assume it’s present </p>
<p><strong>3.</strong> practise good <a href="https://www.cdc.gov/handwashing/when-how-handwashing.html#:%7E:text=Follow%20Five%20Steps%20to%20Wash%20Your%20Hands%20the%20Right%20Way&text=Wet%20your%20hands%20with%20clean,for%20at%20least%2020%20seconds.">hand hygiene</a> to reduce the risk of rare and common infections. That means washing hands thoroughly and often, using soap, scrubbing for at least 20 seconds, rinsing and drying well. Clip and clean under fingernails regularly</p>
<p><strong>4.</strong> to avoid soil-borne parasites wear shoes outside, especially in rural and remote regions, wash shoes and leave them outside.</p><img src="https://counter.theconversation.com/content/212437/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vincent Ho does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Headlines about brain worms can be alarming. There are much more common parasites which can infect your body and brain and ways you can minimise your risks of being infected with one.Vincent Ho, Associate Professor and clinical academic gastroenterologist, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1475782020-11-11T19:19:33Z2020-11-11T19:19:33ZCurious Kids: Do worms have blood? And if so, what colour is it?<figure><img src="https://images.theconversation.com/files/368765/original/file-20201111-13-x5fk9i.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5742%2C3785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock </span></span></figcaption></figure><blockquote>
<p><strong>Do worms have blood, and if they do, what colour is it? Momo Bice, aged 9, Carlton</strong></p>
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<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Momo. Well, the short answer to your question is: yes. Many worms do have blood, and it is either colourless or pink, or red, or even green! But to answer your question properly, first we need to decide what type of worm we are talking about. </p>
<p>There are lots of different sorts of worms. Generally, a worm is any long, thin animal that does not have a backbone, but scientifically we recognise three types of worms: flatworms, roundworms and segmented worms. Worms live in the sea, in sand and soil. Some live inside plants or animals, and we call them parasites.</p>
<p>So let’s look at what blood you might find inside these different types of worms. </p>
<figure class="align-center ">
<img alt="Segmented worm" src="https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368787/original/file-20201111-15-1jhwpuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Worms live in sea, sand soil, or – if we’re unlucky – even inside us.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>The three worm types</h2>
<p><strong>Flatworms:</strong> These include tapeworms, which are parasites (meaning they live on a host organism), and planaria, which live in ponds and lakes. These animals are so flat they don’t even need blood. They absorb oxygen through their skin and it spreads directly to every cell in their body. As a result they are pretty much colourless, or whitish.</p>
<p><strong>Roundworms:</strong> Also called nematodes, these worms are mainly found in soil. Roundworms can also live as parasites in humans, causing really <a href="https://theconversation.com/with-fewer-resources-were-finding-clever-ways-to-map-river-blindness-in-africa-32126">nasty</a> <a href="https://www.cdc.gov/parasites/toxocariasis/gen_info/faqs.htm">effects</a> such as blindness and brain defects. One large roundworm that lives in the intestines of humans can grow to more than <a href="https://www.cdc.gov/parasites/ascariasis/biology.html">35 centimetres</a> – that’s longer than a standard ruler!</p>
<p>As the name suggests, roundworms are tube-shaped. Their body cavity contains fluid that delivers oxygen to its organs. But this fluid is not called blood, because it does not circulate around the body.</p>
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Read more:
<a href="https://theconversation.com/what-are-parasites-and-how-do-they-make-us-sick-121489">What are parasites and how do they make us sick?</a>
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<p>Most roundworm species are very small, and so can diffuse oxygen through their skin to all parts of their body. But very large roundworms can’t do this as easily, especially when they live inside animals where there is not much oxygen. These large worms use an oxygen-carrying molecule called haemoglobin – more on that in a minute.</p>
<p><strong>Segmented worms:</strong> These worms include earthworms, leeches and marine worms. Also known as annelids, the bodies of segmented worms are divided by grooves into a series of segments. Most have circulatory systems – that is, blood vessels and a heart that pumps blood around the body. </p>
<figure class="align-center ">
<img alt="A flatworm" src="https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368777/original/file-20201111-19-u1jv20.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flatworms have no body cavity.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>So what colour is the blood?</h2>
<p>The <a href="https://biomolecules101.wordpress.com/2020/01/17/oxygen-transport-proteins-the-colors-of-blood/">colour of blood</a> in any animal is determined by the molecule that carries oxygen and other gases in and out of the body. If the molecule uses iron to carry the oxygen, then the blood is usually red. If it uses copper, the blood is usually blue. But these molecules can also be green and pink. </p>
<p>All these colours except blue are found in worms. Haemoglobin is the most common oxygen-carrying molecule, including in worms. Haemoglobin contains iron, which means most worm blood – including that of earthworms and leeches – is red. </p>
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Read more:
<a href="https://theconversation.com/curious-kids-why-do-leeches-suck-our-blood-117316">Curious Kids: why do leeches suck our blood?</a>
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<p>Some segmented worms use a different oxygen-carrying molecule called <a href="https://doi.org/10.1098/rspb.1926.0008">chlorocruorin</a>. The blood of these worms can be either green or red.</p>
<p>One group of segmented marine worms has pink blood. This is because the molecule that carries the oxygen is a type of blood pigment, known as <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/hemerythrin">hemerythrin</a>, which is described as pink or purple.</p>
<p>A few species of segmented worms don’t have any oxygen-carrying molecules at all, so their blood is colourless.</p>
<p>So, the answer to your question is that all segmented worms have blood, while roundworms and flatworms do not. The blood colour depends on the molecule that carries oxygen in that worm. And most worms have red blood, just like us! </p>
<figure class="align-center ">
<img alt="Child's hands holding worms and soil" src="https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368776/original/file-20201111-21-1c1giiu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">There are three worm types, and not all have blood.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/147578/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Sandeman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Pink blood, green blood, or no blood at all – when it comes to what’s inside a worm’s body, the answer is more complicated – and fascinating – than you’d think.Mark Sandeman, Honorary Professor, Federation University AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/479492015-09-25T04:32:34Z2015-09-25T04:32:34ZAll you need to know about the space travelling nematode: a worm like no other<figure><img src="https://images.theconversation.com/files/95892/original/image-20150923-2614-jk2ady.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nematodes play an important role in all biological systems. </span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Nematodes are tiny little creatures that could one day be our space pioneers telling us whether or not we can settle on other planets. They are one of the multicellular organisms that can claim to have been into outer space, and then to have successfully returned to earth.</p>
<p>The reason they are chosen for missions into space is that they are model organisms. Their complete genome sequence is known, and the effect of space travel on their DNA can easily be determined. They have travelled on several space missions, mostly in orbit around the earth. In 2003, they managed to be the sole survivors of the Columbia flight that crashed in Texas, when they succeeded in making it back to earth <a href="http://news.bbc.co.uk/2/hi/science/nature/2992123.stm">alive.</a></p>
<p>In future they will be <a href="http://www.nasa.gov/mission_pages/station/research/experiments/1081.html">sent</a> on unmanned missions to the moon or Mars to determine the effect on their DNA and to establish whether humans would be able to survive such a flight.</p>
<p>But way before they are considered as explorers, let us examine the role nematodes play here on our own planet. </p>
<h2>What they are and why they matter</h2>
<p>Nematodes are the subject of many fields of study. They are mostly cylindrical and wormlike. They can vary in size from a few millimetres to 8 metres - that’s the length of 1 000 earthworms laid end-to-end. They can be divided into three groups depending on their habitat - parasites on vertebrates, free living nematodes or plant-parasitic nematodes.</p>
<p>Most people have never heard of nematodes. But they can recall disturbing pictures from the internet of parasites in humans or animals that are mostly from the tropics. They may not even know it, but these are nematodes.</p>
<p>Nematodes can be regarded as animals, generally called round worms. There are males and females. Physically both possess a head and a tail. The female of the species possesses a vulva, whereas the male possesses spicula, both for the purpose of reproduction. Their main aim on earth, as seen from the human perspective, is to succeed in hiding from detection - and to breed in enormous quantities to secure their own <a href="http://www.pml-nematode.org.uk/nematodes/">survival</a>.</p>
<p>These small creatures play an important role in all biological systems, especially in the soil where they perform a strategic function as part of an important ecosystem service to keep soil healthy. They do this by limiting insect, bacterial and fungal populations. They also often act as predators of their own kin.</p>
<p>Nematodes play a pivotal role in the control of weeds by moving above ground in a thin film of water and infecting vast quantities of seeds. This effectively prevents the weeds from <a href="http://www.bioone.org/doi/pdf/10.1653/0015-4040%282003%29086%5B0138%3AAONTEE%5D2.0.CO%3B2">germinating</a>.</p>
<p>The physical limitations of nematodes, such as their basic, wormlike body equipped with a hydrostatic skeleton without any appendices, does not stop them inhabiting every niche on earth. This ranges from parasiting warm as well as cold-blooded vertebrates, to living in vinegar and in the mats under the taps of beer casks. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=920&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=920&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=920&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1156&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1156&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95812/original/image-20150923-32019-w4ejqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1156&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nematodes feeding on a plant root.</span>
<span class="attribution"><span class="source">AP Malan</span></span>
</figcaption>
</figure>
<p>They are believed to have originated in the <a href="http://phys.org/news/2011-04-outlines-mysterious-evolution-nematodes-.html">sea</a>, and they still always need to be close to water to feed and breed. But their need for water is also their Achilles heel, and it is about one of the only things that prevents them from taking over the world. In some cases nematodes have developed ingenious ways of overcoming dry spells, and they can be brought back to life, as it were, in a seemingly miraculous way when water becomes available. </p>
<h2>Resilient beyond belief</h2>
<p>Nematodes are on record for being able to be revived after 32 years in wheat seeds stored in a <a href="http://bionames.org/bionames-archive/issn/0018-0130/40/272.pdf">refrigerator</a>. </p>
<p>But be warned if you want to learn more about these creatures and heed the <a href="http://nematode.unl.edu/cobbyak.htm">words</a> of <a href="http://entnemdept.ufl.edu/nguyen/FLNEM/HISTORY/cobb_bio.htm">N.A. Cobb</a>, the father of Nematology: </p>
<blockquote>
<p>If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognisable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes and oceans represented by a thin film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites.</p>
</blockquote>
<p>Despite a great many people knowing very little about nematodes, scientifically they’re one of the most dominant model organisms that are used in a whole range of research. Most scientists are familiar with at least one member of the nematode family, the <a href="https://cbs.umn.edu/cgc/what-c-elegans">Caenorhabidits elegans</a>. They are used in the study of <a href="http://www.wormbook.org/chapters/www_evoldevnematode/evoldevnematode.html">embryogenesis</a> within the field of genetics. Embryogenesis starts with the fertilised egg and its development to a worm, which in the case of <em>C. elegans</em> takes about 1000 somatic cells with a short life cycle of three days.</p>
<p>Nematodes can be both good and bad. They can be a menace to agriculture, such as the plant-parasitic nematodes that damage the roots of food crops lowering yields. Or they can be used to our advantage to biologically control insects, to control slugs and weeds, and to measure the health of soil.</p><img src="https://counter.theconversation.com/content/47949/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pia Addison receives funding from the NRF, HortGro Science, Winetech, CRI, SATI and SASRI. </span></em></p><p class="fine-print"><em><span>Antoinette Paula Malan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There is much more than just parasitic features when it comes to nematodes: these tiny creatures are vital to ecosystems.Antoinette Paula Malan, Researcher in Nematology, Parasitology, Systematics, Stellenbosch UniversityPia Addison, Senior Lecturer in Insect Diversity, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/364862015-02-23T03:52:33Z2015-02-23T03:52:33ZHealth check: the low-down on ‘worms’ and how to get rid of them<figure><img src="https://images.theconversation.com/files/72718/original/image-20150223-21924-b5aztw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Threadworm infection is common but it's often asymptomatic. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/10789705@N05/5268243488">Ayaka Darkly/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>Intestinal worms (or helminths) are multicellular parasites that live inside the gut. When mature, they can <a href="http://www.ncbi.nlm.nih.gov/books/NBK8282/">generally be seen</a> with the naked eye. </p>
<p>In developing countries with poor sanitation, the most common intestinal worms are transmitted through contaminated soil. The main culprits belong to the <a href="http://www.us.elsevierhealth.com/infectious-disease/manson-tropical-diseases-expert-consult/9781416044703/">roundworm subgroup</a> and include threadworm, large roundworms, whipworms and hookworms.</p>
<p>In Australia, threadworm (or pinworm) is the most common intestinal worm. These worms hatch out of eggs swallowed by the host. But don’t worry: they’re relatively harmless and easily treated. </p>
<h2>Soil-transmitted worms</h2>
<p>A large proportion of the world’s population is infected with soil-transmitted worms. The large human roundworm, <em><a href="http://www.ncbi.nlm.nih.gov/pubmed/20934531">Ascaris lumbricoides</a></em>, is thought to infect one-sixth of the world’s population. The worm can grow to as long as 35 centimetres. </p>
<p>Soil-transmitted intestinal worms can produce a wide range of symptoms including diarrhoea, abdominal pain, lethargy and weakness. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=505&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=505&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=505&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=634&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=634&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72041/original/image-20150215-13186-18ogsh4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=634&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The large human roundworm in a segment of small bowel.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Ascaris_lumbricoides_(Round_worm).JPG">Wikimedia</a></span>
</figcaption>
</figure>
<p>These infections can cause malnutrition and poor growth. Hookworms and whipworms in particular <a href="http://www.ncbi.nlm.nih.gov/pubmed/16679166">can cause</a> anaemia, making children feel weak and tired. <a href="http://www.ncbi.nlm.nih.gov/pubmed/18289159">Some experts</a> believe these worms can also lead to poor performance at school.</p>
<p>Large roundworms, whipworms and hookworms worms are <a href="http://www.ncbi.nlm.nih.gov/pubmed/11681147">uncommon</a> in urban Australia but rural Indigenous communities have relatively high rates. They’re also seen occasionally in overseas travellers. </p>
<h2>Threadworm</h2>
<p>Threadworm (<em>Enterobius vermicularis</em>) is <a href="http://ideas.health.vic.gov.au/bluebook/pinworm.asp">very common</a> in Australian children; the prevalence is estimated to be between 10% and 50% in some groups. </p>
<p>Threadworms can grow up to 13 millimetres long and look like small threads of white cotton, hence the name. They attach themselves to the lining of the large intestine. Adult worms can sometimes be seen in feces or eggs may cling to the skin around the anus. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72716/original/image-20150223-21920-111avle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Threadworms can grow to 13 mm long.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-14313955/stock-photo-adult-pinworms.html?src=GYzD__3T1EzJiIl1u8sLNg-1-3&ws=1">Sebastian Kaulitzki/Shutterstock</a></span>
</figcaption>
</figure>
<p>Threadworm infections are often asymptomatic. When symptoms do occur they <a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcpdf.nsf/ByPDF/Worms_pinworms/$File/Worms_pinworms.pdf">can include</a> an itchy bottom, particularly at night, reduced appetite and feeling mildly unwell or irritable. In young girls, inflammation can occur around the vagina. </p>
<p>Threadworm can be diagnosed in children using the <a href="http://www.rch.org.au/kidsinfo/fact_sheets/Threadworms/">sticky tape test</a> using a kit from your general practitioner. This test is best done in the morning prior to a bath, as worms can migrate during resting periods. </p>
<p>The test involves separating the buttocks and applying a piece of sticky transparent tape to the area just outside of the anus and between the buttocks. The tape is stuck on the skin, then removed and placed onto a glass slide provided in the kit. The doctor will then examine the slide for worms or worm eggs. </p>
<h2>Transmission</h2>
<p>Threadworm infection <a href="http://web.stanford.edu/group/parasites/ParaSites2006/Enterobius/transmission.htm">usually occurs</a> by ingesting infectious eggs. Threadworms rely on the itchiness in the anal skin region to transmit their eggs: children tend to scratch their bottom at night and catch the eggs under their fingernails, which they then put in their mouth. So nail biting, poor hygiene or inadequate hand washing contributes to the spread of threadworm. </p>
<p>Children can easily spread the infection to other family members by transferring eggs to bed linen and bathroom fixtures. In the right conditions, eggs can survive for several days.</p>
<p>Humans cannot contract threadworm from animals. But since animals can be carriers of other intestinal worms, it’s a good idea to regularly deworm pets. </p>
<h2>Treatment</h2>
<p>The <a href="http://www.tg.org.au/index.php?sectionid=71">most commonly used</a> anti-worm products to treat intestinal worms (threadworms, roundworms and hookworms) are <a href="http://livertox.nih.gov/Pyrantel.htm">pyrantel</a>, <a href="http://www.mayoclinic.org/drugs-supplements/albendazole-oral-route/description/drg-20061505">albendazole</a> or <a href="http://www.mayoclinic.org/drugs-supplements/mebendazole-oral-route/description/drg-20064631">mebendazole</a>. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72717/original/image-20150223-21907-5vlbed.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hand washing can stop worms spreading.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-185605919/stock-photo-handwashing.html?src=lrY9alWSxXJHUnJIAd-o0A-1-11&ws=1">Balkonsky/Shutterstock</a></span>
</figcaption>
</figure>
<p>All of these medications are equally effective for threadworm, however albendazole requires a medical prescription. </p>
<p>These anti-worm products only treat the adult threadworms currently residing in the intestines; they don’t treat the eggs or immature worms, which can cause reinfection. </p>
<p>That’s why it’s important to treat the entire family at the same time and to check two weeks after the initial dose in case a second dose of treatment is required. </p>
<p>The role of regular deworming is <a href="http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000371.pub4/abstract;jsessionid=66CB60F91A4EBF00473C48E950FD6C64.f02t03">controversial</a>. Internationally, the World Health Organization <a href="http://whqlibdoc.who.int/publications/2006/9241547103_eng.pdf">recommends</a> annual treatment in areas where soil-transmitted intestinal worms (excluding threadworm) affect 20% to 50% of the population. </p>
<p>But there’s no reason why asymptomatic families in Australia would need regular deworming.</p><img src="https://counter.theconversation.com/content/36486/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vincent Ho does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Intestinal worms (or helminths) are multicellular parasites that live inside the gut. When mature, they can generally be seen with the naked eye. In developing countries with poor sanitation, the most…Vincent Ho, Lecturer and clinical academic gastroenterologist, Western Sydney UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/141632013-05-20T02:52:50Z2013-05-20T02:52:50ZAnimals in research: C. elegans (roundworm)<figure><img src="https://images.theconversation.com/files/23629/original/h7nbx4z5-1368415165.jpg?ixlib=rb-1.1.0&rect=0%2C111%2C800%2C377&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These little worms are very powerful model organisms, revealing important lessons about human biology.</span> <span class="attribution"><span class="source">Niharb</span></span></figcaption></figure><p><strong>Our series, Animals in Research, profiles the top organisms used for science experimentation. Here, we look at <em>Caenorhabditis elegans</em> – a roundworm.</strong></p>
<p>When you think of a worm, what do you see? For some it’s the squeamish thought of treading on one in bare feet after rain; for others it’s the periodical doses of dewormer for the family pet. Perhaps it’s even the slimy tubes that happily munch through the compost.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=509&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=509&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=509&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=640&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=640&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23633/original/kybzfxcc-1368418075.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=640&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">C. elegans.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>Well, now you can add “medical research star” to your list. One species of worm - <em><a href="http://en.wikipedia.org/wiki/Caenorhabditis_elegans">Caenorhabditis elegans</a></em> - has contributed more to medical science in the past few decades than you might think possible.</p>
<p>Some 50 years ago, South African biologist <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/2002/brenner.html">Sydney Brenner</a> made the bold claim that solutions to the important problems in molecular biology were inevitable and that the time had come to tackle more complex questions in other fields of biology. </p>
<p>He identified development and the nervous system as the next big challenges.</p>
<p>Critical advances in molecular biology, including an understanding of how DNA is copied, had been made possible in part by the use of simple experimental systems such as <a href="http://www.phages.org/PhageInfo.html">bacteriophage</a> (a kind of virus that infects bacteria). </p>
<p>With this background, Brenner went in search of a model organism that would be suitable for studies of development and the nervous system. </p>
<p>A small animal that could be easily cultivated and that had a short life cycle would be required. Ultimately, Brenner alighted on a nematode (<a href="http://nematode.unl.edu/wormgen.htm">roundworm</a>) called <em>Caenorhabditis elegans</em>.</p>
<p>Measuring only 1mm, growing readily on simple agar plates with bacteria for food, and taking only three days to develop from an egg to a fertile <a href="http://en.wikipedia.org/wiki/Hermaphrodite">hermaphrodite</a> adult, the nematode fitted the bill.</p>
<p>More commonly referred to simply as “the worm”, Brenner’s model organism of choice is now the subject of research in hundreds of laboratories around the globe, including, at my count, at least ten labs in Australia. </p>
<p>In each of these worm labs, researchers study animals derived from a <a href="http://blog.wellcome.ac.uk/2011/01/18/not-so-wild-thing/">single sample</a> that was taken from mushroom compost in Bristol in the UK in the 1950s. </p>
<h2>The elegant worm</h2>
<p>From these humble beginnings, the worm has afforded us notable insights in many areas of biology.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=869&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=869&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=869&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1092&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1092&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23627/original/7rgc6qqn-1368414475.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1092&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Head of an adult C. elegans. Red staining reveals environmentally exposed neurons, while the blue allows visualisation of all neurons.</span>
<span class="attribution"><span class="source">Carl Zeiss Microscopy</span></span>
</figcaption>
</figure>
<p>In line with Brenner’s aspirations, <em>C. elegans</em> has proved to be an excellent tool for studying development. </p>
<p>Remarkably, every worm grows in essentially the same way – from a single cell, the fertilised egg, to an adult, with precisely 959 <a href="http://www.biology-online.org/dictionary/Somatic_cells">somatic cells</a>. </p>
<p>The worm is transparent, so these cells can be observed using light microscopy. </p>
<p>Through painstaking work requiring several years at the microscope, British biologist <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/2002/sulston-autobio.html">John Sulston</a> meticulously mapped the process of worm development, documenting the timing and direction of every cell division. </p>
<p>This cell lineage is a vital tool that enables researchers to answer questions about how development is controlled at the level of a single cell.</p>
<p>The worm has also lived up to the hope of providing insight into the workings of the nervous system. </p>
<p>Unlike our nervous system, which contains many billions of neurons, the worm has <a href="http://www.wormatlas.org/ver1/MoW_built0.92/nervous_system.html">only 302 neurons</a>. </p>
<p>Neurons are complex cells, which extend long processes and communicate between themselves, and with other cell types, via synapses. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C1278%2C421&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C1278%2C421&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=197&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=197&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=197&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=248&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=248&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23626/original/7thzd2hx-1368414366.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=248&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Adult C. elegans.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>After sectioning the worm into about 20,000 slices, American biologist <a href="https://directory.engr.wisc.edu/bme/faculty/white_john">John White</a> and colleagues used electron microscopy to build a picture of all worm neurons, their processes and their 8,000 synapses, providing us with a complete wiring diagram of this relatively simply nervous system. </p>
<p>As with the developmental cell lineage, this neuronal wiring diagram is an important tool in enabling researchers to address many interesting questions relating to neuronal development and function.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23628/original/grnnbz9f-1368415068.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Worm home sweet home.</span>
<span class="attribution"><span class="source">Niharb</span></span>
</figcaption>
</figure>
<h2>Different strains</h2>
<p>Despite the worm’s simplicity and the many obvious differences between worms and humans, if you look at what is going on inside our cells, we in fact have much in common. Take, for example, <a href="https://en.wikipedia.org/wiki/Programmed_cell_death">programmed cell death</a> – the death of some of an organism’s cells as part of its natural development.</p>
<p>This process is vital for normal development but also plays an important role in <a href="https://theconversation.com/explainer-what-is-cancer-1673">cancer</a>. </p>
<p><a href="http://www.sciencedirect.com/science/article/pii/0092867486900048">Seminal discoveries</a> about programmed cell death were made using <em>C. elegans</em> as a model system and earned Brenner, Sulston and <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/2002/horvitz-autobio.html">Robert Horvitz</a> the Nobel Prize in Physiology or Medicine in 2002.</p>
<p>Another major discovery made using <em>C. elegans</em> was that of <a href="http://ts-si.org/files/NatureMelloFirePaper.pdf">RNA interference</a>, gene silencing by double-stranded RNA. For this, Americans <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/2006/mello.html">Craig Mello</a> and <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/2006/fire.html">Andrew Fire</a> were awarded the Nobel Prize in Physiology or Medicine in 2006. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=910&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=910&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=910&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1144&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1144&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23630/original/v66nwkwk-1368415545.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1144&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Axon degeneration in C. elegans.</span>
<span class="attribution"><span class="source">TheJCB</span></span>
</figcaption>
</figure>
<p>Then, in 2008, American worm researcher <a href="http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2008/chalfie.html">Martin Chalfie</a> shared in the Nobel Prize in Chemistry for his contribution to the development of green fluorescent protein as a tool for visualising biological structures in living organisms.</p>
<p>Aside from these seminal Nobel-winning discoveries, research using <em>C. elegans</em> continues to yield new information in diverse areas of biology such as <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=elegans+AND+behavior">behaviour</a>, <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=elegans+AND+metabolism">metabolism</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=elegans+AND+aging">ageing</a>, to name but a few. </p>
<p>Many resources are shared among the worm research community, facilitating these endeavours. </p>
<p>These include an extensive collection of worm strains carrying mutations in particular genes and bacterial strains that can be fed to worms to reduce the function of any gene of interest by RNA interference. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=559&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=559&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23782/original/vyhf3d43-1368578043.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=559&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">C. elegans, going about their business on a petri dish.</span>
<span class="attribution"><span class="source">Slavica Berber</span></span>
</figcaption>
</figure>
<p>Since <a href="http://www.ncbi.nlm.nih.gov/pubmed/10767309">around 40%</a> of the genes implicated in human disease have equivalents in worms, these tools also make it possible to learn more about the underlying mechanisms of many diseases by examining the function of the related gene in the worm. </p>
<p>It is also straightforward to introduce new genes into <em>C. elegans</em>, including those from humans. </p>
<p>This approach has, for example, been used to create worm models for studying <a href="http://www.ncbi.nlm.nih.gov/pubmed/15977988">Alzheimer’s disease</a>. </p>
<p>Such disease models can further be exploited to screen for drugs which may ultimately be used to treat human disease.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=143&fit=crop&dpr=1 600w, https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=143&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=143&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=179&fit=crop&dpr=1 754w, https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=179&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/23793/original/965vzmb4-1368581022.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=179&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">C. elegans anatomy.</span>
<span class="attribution"><span class="source">Hannah Nicholas</span></span>
</figcaption>
</figure>
<p>Through the past 50 years <em>C. elegans</em> has proved to be a very powerful model organism, revealing to us important lessons about our own biology. </p>
<p>The collaborative spirit that characterises the <em>C. elegans</em> research community, which is epitomised in the publication of <a href="http://www.wormbook.org/wbg/">The Worm Breeders Gazette</a>, a newsletter for sharing results and techniques, will ensure that the next half century in worm world is equally productive.</p>
<p><strong>To read more in the Animals in Research series, follow the links below:</strong></p>
<p><strong><a href="https://theconversation.com/animals-in-research-drosophila-the-fruit-fly-13571"><em>Drosophila melanogaster</em> (the fruit fly)</a></strong><br>
<strong><a href="https://theconversation.com/animals-in-research-zebrafish-13804"><em>Danio rerio</em> (zebrafish)</a></strong></p><img src="https://counter.theconversation.com/content/14163/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah Nicholas receives funding from the National Health and Medical Research Council.</span></em></p>Our series, Animals in Research, profiles the top organisms used for science experimentation. Here, we look at Caenorhabditis elegans – a roundworm. When you think of a worm, what do you see? For some…Hannah Nicholas, Lecturer in Molecular Biology, University of SydneyLicensed as Creative Commons – attribution, no derivatives.