The H5N1 avian flu outbreak in cats in Poland seems to be slowing down but the cause is still under investigation. While outbreaks often die out on their own (sometimes because of what we do, sometimes despite what we do), it’s still important to figure out what happened, to help understand the disease and ideally prevent future problems.

It seems like the number of confirmed cases has stayed at 16 and I’ve received fewer anecdotal reports from people in Poland about new sick cats. Clear information is still fairly sparse (and my lack of Polish fluency doesn’t help) but there have been reports implicating food as the source of H5N1 infection in these cats. I mused about possible sources of the virus in this outbreak last week, and a food link was on the list, but I assumed it was #2 or #3 on the depth chart).

A few pertinent things have been reported from different sources:

The same or very similar H5N1 strain was found in multiple cats from different areas.

• That would be consistent with a point source exposure such as food, but could also be because there’s a single dominant strain of the virus that different cats were exposed to through other routes over a short period of time.

H5N1 was found in 1 of 5 samples of raw poultry diets from affected households

• That’s a critical finding. Most importantly, they found more than just viral RNA (which could be dead virus) – they were able to isolate the whole virus, meaning it was in a viable state in the diet.
• This adds a lot of weight to the food-source hypothesis, but since it’s retrospective and so far just 1 food sample tested positive, it’s not definitive.

For me, a key question remains: Did all of the cats receive the same diet?

That’s a very basic component of the epidemiological investigation that should be easy to sort out, but unfortunately laboratory components of outbreak investigations often move faster than boots-on-the-ground epi / info collection. If all the cats got the same diet and contamination of at least some samples of that diet can be demonstrated, that’s a pretty solid presumptive link, especially for the affected indoor cats. It’s a bit trickier in outdoor cats because of other potential sources (e.g. birds), and more details about the genomics of the locally circulating virus strains is needed to help sort that out. Ultimately, we’re often left with “most likely” cause, versus “Eureka! We’ve nailed the diagnosis!”

So, hopefully we’ll get more details soon but we have to move food up to the top of the list for potential sources in this outbreak for the moment. That raises a few more obvious questions:

Should cats be fed raw poultry?

There are various issues with raw diets and this just adds another dynamic. Without knowing more about the food that’s been implicated here, it’s hard to say too much.

The risks from typical commercial diets prepared from poultry that’s deemed safe for human consumption (the poultry, not the pet food) is very low. Since H5N1 infections on poultry farms are usually pretty obvious (lots of sick and dead birds very quickly), it’s unlikely that infected poultry from commercial operations would make it into pet food manufactured by a reputable company.

If there are pet food diets that do not use typical “human-grade” poultry, the risks could be higher. If poultry from infected farms is (presumably illegally) being diverted to dodgy pet food companies, risks from those would be even higher.

If people are making their own raw diets, the origin of the birds/meat is the key. Poultry purchased at grocery stores should be exceptionally low risk. Other sources (e.g. live birds or meat from small outdoor operations) could pose much greater risks. The less scrutiny and transparency about the poultry sources, the greater the concerns.

The safest way to avoid food safety concerns from raw diets is to avoid them, cook them, or use a product that’s at least high pressure pasteurized (there’s no guarantee the HPP process eliminates all pathogens in the food, but it should at least greatly reduce pathogen levels).

So, at this point, I’d avoid feeding raw poultry to pets if there’s not complete confidence in the source, especially in areas where H5N1 is active in birds. I’d stick with products from companies with strict (and transparent and adhered to) rules about their sources, that use commercially reared poultry and that have a proper food safety program.

Are there related food safety concerns for people?

More information about poultry sources that are linked to this outbreak is critical. If food was a source, was it the same poultry that’s eaten by people, or was it from some other pathway? That’s a big question.

That said, fortunately people don’t tend to (deliberately) eat raw poultry. Cooking will eliminate any influenza virus (and a lot of other pathogens) in the meat. However, there’s always some risk of exposure to foodborne pathogens from improper handling and cooking (that’s how we get things like Salmonella) and H5N1 can survive on meat for at least a few days. So, we can’t ignore the risk entirely.

The risks would be lowest (and approaching negligible) from poultry sold in grocery stores. The risks would be highest from live market-sourced birds where there’s no information about the health status of the flock. There are gradations in between, but overall, the less the confidence in the health status of the flock, the greater the risk of contamination of the birds and the products made from them.

Cooking poultry properly, prevention of cross contamination and good kitchen hygiene (including hand washing) would greatly reduce any risks, even in the unlikely event contaminated poultry was present.