Not particularly. These are fairly rare phenomena in cats. But, on this episode of avian influenza which has been continuing since November 2021, there have been some contaminations of mammals in the world. There hadn’t been a chat on this episode yet but it already happened in 2006, but not in France. On the other hand, the virus currently circulating in birds has been the source of contamination of mammals in the world, in particular otters, foxes, seals, minks, some bears… These are mammals which have had close contact with sick poultry, who captured them and who were able to breathe droppings dust on this occasion.
Is this how the virus spreads?
Yes, it is not by ingestion but by inhalation that the virus is transmitted. And, generally, carnivorous animals sniff before eating. When an animal consumes a sick or dying animal, it may breathe in dust from droppings under the feathers or respiratory droplets ejected by the poultry. In birds, we do not speak of bird flu because it is a systemic infection, not just a respiratory one. All organs are infected. The virus is excreted through the respiratory system of birds but also heavily through droppings. It is for this reason that there are large quantities of viruses emitted into the environment because as much as the respiratory droplets disperse easily, as much as the droppings remain on the ground, can dry out, create dust… Moreover, with the temperatures In current times, the virus survives for almost two months in the droppings. When a herd is slaughtered, the slurry and manure is kept for two months before spreading it, so as to inactivate the virus, especially in winter. The virus inactivates faster with high temperatures.
How was this cat infected?
The virus is the same as that which had contaminated the ducks of the neighboring farm. The cat could have been in contact with the ducks but also with the same environmental source that contaminated the ducks, a wild bird for example.
The multiplication of this virus in a mammal can lead to the selection of mutants, better adapted to the internal temperature of these mammals. The virus isolated from the infected cat presented two mutations, one of which (2) indicates the adaptation of the replication temperature of the virus. In birds, the influenza virus multiplies at 40°, the temperature of the respiratory tree of birds. But with this mutation, the virus can multiply at 35°, the temperature of the respiratory tract of mammals. The virus probably mutated in the cat or the latter “recovered” viruses that had already mutated in ducks or a wild bird.
What symptoms was he showing?
The cat showed symptoms of severe encephalitis, enough for her suffering to be cut short. We found the influenza virus in his cerebrospinal fluid, which leaves no doubt about the cause of the disease.
But how can a mammal be contaminated?
Virus receptors in birds and in mammals are different. But contamination of mammals with this influenza virus is possible because there are some bird virus receptors that are found in the lungs of mammals, not on the bronchi. Generally, influenza viruses attach themselves to the bronchi, but there are also receptors in the alveoli of the lungs. Contamination comes from fine contaminated dust that is inhaled and goes to the pulmonary alveoli. The virus can then attach and multiply. This can give quite serious cases of pneumonia. In mammals, with the virus currently circulating, it has been found that these are often nervous symptoms. It is a systemic infection with a virus that passes through the bloodstream before infecting nerve tissue.
What precautions should you take to avoid contamination of your cat?
When you know that there are contaminated poultry or birds in your environment, cats must be isolated as much as possible from sources of contamination. In particular when you live next to a farm, but also when you live near a place where mortality has been observed in wildlife, where mortality is currently quite high, especially of black-headed gulls. Since last week, for example, most of the departments in the Paris basin crossed by the Seine have been affected. They are probably birds brought up from Normandy, along the course of the Seine. All it takes is a storm for seabirds to go up along the rivers to protect themselves, which happens very frequently in Brittany, for example. It is therefore necessary to avoid that cats come into contact with dead or dying birds.
Do you advise cat owners to vaccinate them?
There is no vaccination against this virus for cats. And it’s a very rare phenomenon, just imagine the number of cats in France who are in contact with birds…
Can an infected cat infect another cat?
There is little risk of this happening. In the specific case of the Deux-Sèvres cat, there was also another cat and a dog, not sick, in the house. Samples taken by veterinarians have been sent to us. The first PCR results are negative. They are not carriers of the virus, which is very reassuring with regard to contagiousness. Generally, there is no interhuman contagion between mammals with this type of virus.
Can cats transmit the virus to humans?
We have not seen any serious or even symptomatic cases in humans in Europe. There have been positive cases without symptoms in Spain with people who had picked up dead birds without protection. More recently, a girl was infected before falling seriously ill in Ecuador. We remain cautious because we could have cases with people massively exposed to contaminated dust. But, generally, when an avian influenza virus is transmitted to a mammal or to humans, human-to-human transmission is not good, or even non-existent. First, because the virus is found in the lungs and not in the bronchi, so it is less excreted by the respiratory route; then because it is a virus which is still very little adapted to mammals so it will not be very contagious. The infection can be serious, but it always comes from contact with sick poultry, and not from subsequent human-to-human transmission.
How do you know if a cat is infected?
If this can be seen by respiratory symptoms, in all observations of mammals, brain lesions have been found, which are very painful. It is a virus that will reach the brain and, in all cases, behavioral changes have been observed. The cat may be completely dejected or very nervous, aggressive… But, once again, there is nothing to worry about, it is not a frequent contamination in cats. There are only precautions to take when there are sick birds in its immediate environment. However, the probability of contamination is very low.
Are the risks important for humans?
When you are a mammal, including humans, and you are exposed to this virus, you can have cases of contamination due to these random mutations. Hence the importance of protecting yourself when handling these birds, in particular by wearing a respiratory mask to avoid inhaling fine particles containing the virus. This particularly concerns people exposed to contaminated birds: breeders, slaughter teams for these contaminated birds, people who collect dead birds, including volunteers from various NGOs, agents from the French Office for Biodiversity , veterinarians…
(1) National Food Safety Agency.
(2) Mutation of an amino acid on the PB2 protein of the virus at position E627K.
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