FIP rages. Avian flu outbreaks among cats are few, but hint at increasing vulnerability of mammals to bird diseases
NICOSIA, Cyprus; WARSAW, Poland; HELSINKI Finland––Potentially catastrophic disease outbreaks hitting cats in Cyprus and Poland, and farmed foxes in Finland, have epidemiologists worried about emerging mutant strains of feline infectious peritonitis, a coronavirus best known as FIP, also called “cat COVID,” only affecting cats, and high pathogenic avian influenza [HPAI] H5N1, a bird ailment which does not normally affect mammals.
Infectious outbreaks rare among cats
Neither disease hits humans, but the appearance of the bird flu HPAI H5N1 in carnivorous mammals is potentially a step toward a mutation that could affect humans.
The FIP and HPAI-H5N1 outbreaks are unrelated and geographically far removed from each other.
Outdoor cats, however, tend to hunt alone and have little contact with each other. Therefore, cats relatively seldom become vectors for diseases either rapidly moving among other cats or jumping to other species. That two such outbreaks are occurring at the same time appears to have no particular significance, yet is unusual.
Epidemic FIP never before reported
Epidemic FIP, never before reported, has already killed 300,000 cats in Cyprus in 2023, Daily Telegraph global health security correspondent Sarah Newey reported on July 11, 2023.
“Experts have warned that “many cats” could die if the virus circulating in Cyprus makes its way to Britain,” Newey wrote.
Cyprus, “sometimes called the “island of cats,” according to Newey, “ is home to the earliest evidence of the cat’s domestication. But there is mounting unease about the threat posed by cat Covid, which does not infect humans, but is mostly fatal if left untreated in felines.”
“An alarming increase in FIP cases started in the capital city of Nicosia in January 2023 and spread throughout the whole island within three to four months,” Pancyprian Veterinary Association vice president Demetris Epaminondas told Newey.
“First outbreak of this extent”
“In a recent blog post, he added that this is the first ‘outbreak of this extent’ ever reported,” Newey paraphrased, “with previous FIP clusters generally restricted to catteries. Symptoms include fever, abdominal swelling, energy loss, and sometimes even increased hostility. The virus generally affects kittens and young cats.”
University of Edinburgh feline veterinary medical specialist Danièlle Gunn-Moore told that an FIP outbreak as big as that in Cyprus “has never been seen in living or reported history.”
“There is already some evidence – albeit anecdotal – that it may already be in Turkey, Lebanon and potentially Israel,” Gunn-Moore said. “If this virus gets to the United Kingdom it could cause many of our cats to die. It would be heart-breaking. We must take this seriously.”
Tests are underway, Newey said, to determine if the Cyprus strain is a new and more deadly form of FIP. Alternatively, most of the Cyprus cat population, believed to have been around one million before the outbreak began, may not have been previously exposed to FIP, and might therefore have been exceptionally vulnerable.
If this is the case, though, it is surprising. Archaeological evidence indicates that cats have been domesticated on Cyprus for about 9,500 years, about 1,500 years predating the domestication of cats in Egypt, while Cyprus is a common destination of retirees, many of whom bring pet cats with them from all over Europe.
Currently Cyprus is home to about 156,000 foreign nationals, including about 25,000 British expatriates.
The official FIP death toll, Newey reported, is only 107 cats, but that includes only cats whose remains have actually been tested for FIP.
No drugs, no vaccines
The estimate of 300,000 cats deceased came from Dinos Ayiomamitis, head of Cats PAWS Cyprus and vice-president of Cyprus Voice for Animals, Newey said.
The antiviral drugs remdesivir, GS-441524, and molnupiravir are effective against FIP, Newey added, but are expensive, and molnupiravir, the cheapest of the three, is not authorized for import into Cyprus as a veterinary drug.
Gunn-Moore urged that an FIP vaccine be developed for use in Cyprus. Nasally administered FIP vaccines have in fact long been available, but are difficult to administer, especially to cats who are not used to being handled, are not effective in cats who have already been infected, and are not generally recommended by the Cornell Feline Health Center.
“Cause for concern”
The discovery of HPAI-HN1 in cats in Poland and farmed blue foxes in Finland was not entirely a surprise, but “The growing number of infections by HPAI viruses in mammals that have
been reported since April 2022 is cause for concern,” posted Program for Monitoring Emerging Diseases [ProMED] wildlife disease moderator Pablo Beldomenico.
“The evolution of variants capable of mammal-to-mammal transmission would dramatically
worsen the epidemiological scenario,” Beldomenico warned, “with serious consequences such as conservation impact for the mammalian species implicated and being a step closer to human-to-human transmission.
“The vast majority of the HPAI H5N1 cases detected in mammals involved carnivores,” Beldomenico explained. “There have been reports in red foxes and bush dogs, and now arctic foxes, bobcats and mountain lions, skunks, raccoons, bears, otters and minks, and seals and sea lions.”
The common denominator among all of these species, of seven different families, is that they are predator/scavengers who sometimes consume migratory waterfowl: ducks, geese, and swans, all of whom mingle inside the Arctic Circle in summer, sharing avian flu strains, then disperse around the world in winter.
Domestic cats and farmed foxes, however, have relatively little opportunity to either hunt or scavenge migratory waterfowl. And even if domestic cats and farmed foxes did have the opportunity, most adult migratory waterfowl are too big to be within their prey range.
Nonetheless, the Finnish Food Authority reported on July 14, 2023, “An avian influenza infection has been detected in blue foxes in Kaustinen, Central Ostrobothnia. It is the same highly pathogenic H5N1 virus type that has caused several mass deaths of wild birds recently.
“In addition, animals from four other fur farms in South and Central Ostrobothnia have been found to have influenza virus,” the Finnish Food Authority said, “the more detailed typing of which is still ongoing.
“Avian influenza has not previously been detected in farmed fur animals in Finland. In wild foxes, on the other hand, the infection has been detected twice in Finland,” the Finnish Food Authority added.
Because HPAI H5N1 is not believed likely to spread from mammal to mammal, ProMED explained, “Infection with avian influenza in fur animals does not cause any restrictions imposed on the farm by the animal health authority.”
The Finnish Food Authority told the World Organization for Animal Health that of the 3,500 foxes housed at the farm in Kaustinen, Central Ostrobothnia, only three actually died from HPAI H5N1. The farm also housed 1,500 raccoon dogs, also called tanuki.
Black-headed gulls seen near the farm were somewhat plausibly named as the immediate suspects for infecting the foxes, since HPAI H5N1 was known to be attacking black-headed gulls in northeastern Italy.
However, both foxes and tanuki are farmed in close confinement within roofed sheds, inaccessible to either gulls or any other wild birds.
Another avenue for infection would be that migratory waterfowl passed HPAI H5N1 to domestic waterfowl, whose offal was fed to the farmed foxes after their meat was processed for human consumption.
HPAI H5N1 in cats
HPAI H5N1 infections in domestic cats were first reported by the Polish National Veterinary Institute on July 3, 2023. Nine cats in all were infected, in Poznań, Gdańsk, Gdynia, Sopot,, and Lublin.
“The H5N1 avian influenza viruses from cats analyzed so far originate from a single, unidentified source,” the Polish National Veterinary Institute said, “related to the H5N1 viruses circulating in wild birds in recent weeks in Poland.”
Three more infected cats were found by July 7, 2023, the Polish National Veterinary Institute indicated, but the European Centre for Disease Prevention & Control reported that “On 5 Jul 2023, Polish authorities informed ECDC that a total of 45 samples from sick or dead cats were tested, of which 24 were positive for influenza A(H5N1) virus.”
Increased exposure to humans
Meanwhile the outbreak of HPAI H5N1 among black-headed gulls in northeastern Italy spread to five dogs and a cat at a rural poultry farm in the province of Brescia.
Wrote Beldomenico, “Information about HPAI H5N1 in domestic cats and other felids has been gradually accumulating since 2004. Recent cases in France, the USA, Italy and Poland may be indicative of much wider, not-yet-detected and published dissemination of the virus in wild,
farmed and pet animals.
“The latter may lead to increased exposure of non-rural, general public, susceptible human populations to a virus whose high pathogenicity has already been recorded in several mammalian species.”
“Food is one likely route of transmission”
Updated the Polish National Veterinary Institute, in a communique relayed by ProMED, “With regard to the transmission of HPAI H5N1 virus from birds to domestic cats, food is one of the likely routes of transmission of the pathogen.
“This is indicated by: (a) the sudden appearance of the virus in both indoor and outdoor cats in different parts of the country; (b) no outbreaks of infection with cat-to-cat transmission;
(c) analysis of the genome sequence of the virus taken from the cat showed no drastic changes compared to the reference sequences, suggesting the emergence of a new strain of influenza virus effectively infecting cats; d) the sequence similarity of viruses that have been isolated from cats in different parts of Poland is very high, which suggests a single source of infection; and (e) discussions with cat owners have suggested raw meat may be the source.
“To test this theory initially,” the Polish National Veterinary Institute said, “we asked the owners of sick cats to submit samples of the meat they ate. As a result, we received five meat
samples for testing and conducted molecular tests for the presence of the virus.
“The analysis showed that one of the five samples contained the virus.
“Although it cannot be ruled out that the virus found its way into the meat samples later, or even the meat was contaminated by the owners with the virus developing in the cat’s body,” the Polish National Veterinary Institute said, “it is also possible that the raw meat was the source of infection.
“This would not be surprising,” the Polish National Veterinary Institute concluded, “because in 2007 a case of contamination of frozen duck meat with the H5N1 virus was reported, which caused outbreaks of the disease in Germany.”
As with the infection of the farmed foxes in Finland, a likely avenue for infection of Polish cats would be that migratory waterfowl passed HPAI H5N1 to domestic poultry, whose offal was processed into cat food following slaughter for human consumption.
Commented ProMED animal health and zoonoses moderator Arnon Shimshony on July 20, 2023, after the arrival of additional data from the Polish National Veterinary Institute, “Out of 61 cats from numerous locations in Poland tested since June 10, 2023, 33 domestic cats and one captive privately owned caracal were found infected by a similar genotype of HPAI H5N1 virus, which was identified also from a single
“One suggested scenario is penetration of the virus into the animal food chain. Though the event seems to have peaked, no effort should be spared to fully accomplish the event’s investigation, hopefully excluding the said concerning scenario.
“Conclusions and suggested updating of the control and testing requirements upon the slaughter and marketing of raw poultry meat should cover also the general food chain, to prevent direct exposure of consumers to HPAI.”
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