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Brace yourself, internet: cats and dogs at risk from new fungus

Brace yourself, a new infection is on the prowl. Ian Nicholson/PA

A new fungal infection may spell doom for LOLcats and cute puppies. Researchers have found a fungus that affects cats, dogs and humans with nasty consequences.

Vanessa Barrs at the University of Sydney and her colleagues have discovered a mould called Aspergillus felis that has already claimed the lives of many cats, a dog and a man.

The world of Aspergillus

Various members of the mould group Aspergillus are widely found. Many of them cause serious diseases in humans and animals, which may be fatal if untreated. The most commonly known member of this group is Aspergillus fumigatus. Its role in causing disease is well-documented.

Spores of these moulds spread aerially. If inhaled by those with weak immune system, they can overcome the body’s defences and start growing inside the nasal passage, sinuses and lungs. The moulds may even spread to the brain and other organs through blood.

The disease caused by some Aspergillus moulds is called aspergillosis. In humans, it may take the form of an allergic response, or the mould may invade and destroy the tissues of the lungs. Spores may also settle into air filled pockets inside lungs and grow into fungal balls, often seen in wild birds. In domestic cats and dogs, this mould invades the nasal cavity and sinuses, causing a condition called fungal rhinosinusitis. Often, it spreads its thread-like projections, known as hyphae, behind the eye and into the brain.

Aspergillosis can be treated with modern anti-fungals. However, the disease caused by other members belonging to species such as felis, lentulus and udagawae may not always be susceptible to modern drugs. This is a cause for worry for public health.

Nasty surprise

Aspergillus fumigatus as seen under a scanning electron microscope. Koichi Makimura

Barrs’s study recently published in the journal PLOS One looked at a variety of cats in Australia and the UK, including purebreds (such as Russian blue, Cornish Rex, Himalayan Persian, Chinchilla Persian, Ragdoll, and Exotic Shorthair) and domestic crossbreds (short hair and long hair). They appeared healthy, but had long-time sniffles and sneezes. On examination they were found to suffer from rhinosinusitis caused by Aspergillus felis. Many of them had a fungal ball growing behind an eye, which pushed that eyeball outwards. Quite a few were severely afflicted beyond hope for recovery and had to be euthanized.

The study also included a dog in Australia and a man in Portugal, both of whom had weakened immunity. Aspergillus felis had invaded the body of the dog causing pain, fever and abnormal heart sounds. In the man, it was growing in the lining of the lung. Both succumbed to the disease.

This mould is different from many others in the Aspergillus group because, as Barrs found, it was able to grow at 45˚C, a relatively high temperature. Barrs compared genetic signatures of Aspergillus felis recovered from its victims to those from other moulds obtained from human infections. These signatures clearly implicated this mould in human and animal diseases. Studying genetic signatures is a good way to track the spread of microbes.

Common azole or polyene antifungal drugs failed to kill the mould, but it did respond to newer echinocandin antifungals. Barrs and her colleagues are keeping an eye on this mould in order to combat it.

For a newly discovered microbe that causes disease, this is good news. In the fight against microbial pathogens, knowledge is power.

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