White Oaks West Animal Hospital

Current Information about the Avian Influenza virus can be found at the following World Health Organization site:

Reports from Germany of a cat found dead due to a highly pathogenic avian influenza virus infection have fueled concerns about the risk this emerging virus poses to cats and, subsequently, to the people who care for them. Can cats catch the bird flu? These reports, along with recent studies, say "yes." But might it also be possible for cats to get the flu from us- or for humans to get the flu from cats? The short answer is "no." None of the known strains of influenza virus are transmissible between cats and people. But these viruses are very changeable by nature, so the long answer is a bit more complex.

Bird Flu Found to Sicken Cats
Finding raises worries about transmission to humans

by Amanda Gardner, HealthDay Reporter | Sep 02 '04

For the first time, a type of bird influenza has been shown to infect and
sicken house cats, which has some experts worried that there may one day be
a strain of severe flu that can pass easily from human to human and create
a pandemic.

The flu strain in question is the 2003-2004 outbreak in Asia of the H5N1
virus, which caused massive poultry slaughters in eight Asian countries and
also led to at least 34 human infections, at least 23 of which were fatal.
During the outbreak, there were also anecdotal reports of fatal infections
in cats.

The news is startling to some because domestic cats had been thought to be
largely resistant to actually getting ill from influenza A viruses such as
this one, even though they could be infected.

But others said the findings don't point to impending calamity. "We're
still a long way off from saying cats are vitally important in this chain,"
said Dr. Susan McLellan, a tropical medicine and infectious diseases expert
at Tulane University School of Medicine and School of Public Health. This
report also has nothing whatsoever to do with the average North American
house cat, McLellan emphasized -- only cats that spend a lot of time on
farms in Asia with infected birds. McLellan was not involved in the study,
which is reported in the Sept. 3 online issue of Science.

The researchers tested whether domestic cats would become sick if the H5N1
virus was introduced into the airways or by feeding infected chickens to
the cats. The six cats in the study all developed severe lung disease and
transmitted the disease to two additional cats that were living nearby.

When cats were exposed to another virus, H3N2, which most commonly causes
flu in humans, the felines did not get sick.

"The novelty of our study was not so much that this H5N1 virus spreads from
birds to cats, because previous studies have shown that cats can be
infected with other influenza virus strains," said study author Thijs
Kuiken, a veterinary pathologist in the department of virology at Erasmus
Medical Center in The Netherlands. "The novelty is that H5N1 virus causes
disease and can be fatal in cats. In most previous experimental studies,
influenza virus infection did not cause clinical signs or death in cats."

What does this mean for human health?

"First, cats should be considered as a potential source of infection for
humans on farms where poultry are infected with H5N1 virus, and where cats
have access to these poultry or their feces," Kuiken said. "Cats also
should be considered as a potential source of infection for humans if they
have been fed on carcasses of poultry infected with H5N1 virus."

Still, poultry are more likely to transmit the virus to humans than cats,
as cats shed less of the virus, Kuiken added.

On the other hand, because they are mammals, infected cats may provide an
opportunity for the bird virus to adapt to other mammals, including humans.
"The concern about species-to-species transmission [including cats to
humans] is that it increases the risk of developing a virus strain that is
easily transmissible from human to human," Kuiken explained. "It is such a
strain which could trigger the pandemic that many experts have been
predicting."

The scenario experts have been dreading is that two different flu viruses
can exchange chunks of genetic information and make a virus that spreads
from human to human much quicker and easier than one virus that mutates
over time. "The worrisome part is putting two different types of influenza
viruses in the same organisms [for example, a cat], they then may recombine
and we'll get the worst of both," McLellan said.

The chances aren't high, however.

"There was no mutation in the virus. This has probably been happening to
cats for years and nobody bothered to look," McLellan said.

The U.S. Centers for Disease Control and Prevention also has more information on bird flu.

Source: World Health Organisation (WHO), Communicable Disease Surveillance and Response (CSR), Disease Outbreak News, Fri 20 Feb 2004 [edited]

Avian influenza A (H5N1) Virus Infection - WHO Update 28
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Thailand: Reports of infection in domestic cats
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WHO is aware of reports of avian influenza a (H5N1) virus infection in a single household of domestic cats in Thailand. Investigations are under way, and no firm conclusions can be made at present. However, concern is great and several specific questions are being raised about risks to humans in close contact with infected cats and the need for surveillance of disease in cat populations.

Avian influenza A (H5N1) virus infection in 2 out of 3 dead domestic cats was announced today by the Faculty of Veterinary Sciences at Thailand’s Kasetsart University. The animals are part of a single household of 15 cats. Of these, 14 have died. Contact of one cat with dead chickens was observed by the owner. Thailand’s Ministry of Public Health is investigating the incident in cats and is monitoring the health of human contacts. FAO is also contributing expertise.

While conclusions are premature pending the results of these
investigations, confirmation of H5N1 infection in cats is not considered likely to enhance the present risks to human health. Nor is it considered likely to influence the future evolution of the outbreak in humans in any significant way. Several studies have shown that a small number of mammalian species, including pigs, seals, whales, mink, and ferrets, are [also] susceptible to natural infection with influenza viruses that are purely avian in their genetic makeup. Of these species, only the pig has significance for human health. Pigs can be co-infected with both avian and human influenza viruses and can thus serve as the "mixing vessel" for the
mingling of genetic material, possibly resulting in the emergence of a new influenza virus subtype. Most experts agree that pigs played a role in the emergence of pandemic viruses in 1957 and 1968.

Up to now, domestic cats have not been considered susceptible to disease caused by natural infection with influenza viruses. Some older studies, from1970, 1972, and 1981, reported experimental infection of domestic cats under laboratory conditions. Although infection occurred (virus was recovered from the respiratory tract), all of the cats remained healthy. None developed typical symptoms of influenza, including fever, nasal discharge, coughing, or sneezing. These findings are important, in that they strongly suggest that, should additional cats become infected with H5N1, they would not shed large quantities of the virus.

In contrast, avian influenza A (H5N1) virus replicates in the intestines as well as the respiratory tract of birds. In the present outbreak, very large quantities of virus are being excreted in the faeces of infected birds, resulting in widespread contamination of the environment. This wide presence of the H5N1 virus in the environment creates one of the most important risks for human exposure and subsequent infection. Should domestic cats prove to be easily infected with H5N1, which is considered unlikely, their infection is not expected to contribute in a significant way to the presence of H5N1 virus in the environment. Avian influenza viruses, including the specific strain implicated in the present outbreak, lack the receptors needed to infect mammals efficiently. However, the infection of humans observed in this and 2 previous H5N1 outbreaks demonstrates that transmission from birds to mammals can occur despite this lack of receptors. The very small number of human cases - despite abundant and widespread opportunities for exposure and subsequent infection - strongly suggests that transmission of H5N1 from birds to mammals,
including cats as well as humans, is a rare event.

The reported infection of domestic cats with H5N1 is an unusual event in what is an historically unprecedented situation. Results from the investigation undertaken by Thai authorities will shed critical light on this unusual event. Influenza viruses are highly unstable and their behaviour cannot be predicted. Vigilance for suspected cases in various mammalian species is presently high and should be continued. Reporting by veterinarians of suspected or confirmed cases to national authorities, as happened in the present situation, is a key component of this continuing vigilance.

Earlier it was reported that a Tiger in a zoo in Thailand may have died from the avian influenza strain too!

Three pet cats have died of bird flu and a white tiger has been infected by the virus at a zoo in Thailand, an official said Friday, raising concerns about the spread of the avian disease among mammals.

It was unclear whether the virus could spread from felines to humans, but the veterinarian who announced the latest confirmed infections advised people to avoid contact with pet cats in areas with poultry, which are at high risk of catching the disease.

"At this moment we know that felines can get infected for sure," Dr. Teeraphon Sirinaruemit, a veterinarian at Kasetsart University, told a news conference. "It is best for owners not to have direct contact with cats if there are chickens in the neighborhood."

So far, cases in people have been traced largely to direct contact with birds sickened by the H5N1 virus that has decimated poultry stocks through wide swaths of Asia. It has jumped to humans in Thailand and Vietnam, killing 22. The pet cats are the first domesticated mammals known to have contracted the disease in the current outbreak.

World Health Organization viral expert Dr. Prasert Thongcharoen said this development is "very dangerous because pets are very close to humans. Because this disease is new to the world, nobody knows how far it can go," the WHO expert said Thursday, after reports of the cats' possible infections surfaced.

Teeraphon said Friday that the carcasses of the 3 pet cats who died were tested, along with [samples from] a white tiger at the Khao Khiew zoo in Chonburi province near Bangkok. All were found to have the H5N1 virus.

He said the white tiger has since recovered and is in good health. The Khao Khiew zoo is the same one where a clouded leopard died of the bird flu [in January 2004], the first mammal apart from humans to die in this year's outbreak. Teeraphon said lab tests on 3 house cats and the tiger has "confirmed 100 percent identical genetic code to the bird flu virus found in chickens."

Health experts are concerned about the bird flu sickening other animals, in part because that could prompt mutations in the virus that in turn makes it easier to pass among people. That concern holds especially for pigs because of their genetic similarities to humans [see comment below].

Teeraphon said the 3 cats were among 15 owned by a Thai woman in Nakhon Pathom province outside Bangkok. One of them ate a chicken carcass on a farm where there was a bird flu outbreak, he said. The cat disappeared and the remaining 14 became weak, started vomiting, and coughed blood before dying. 3 were sent for necropsy on 11 Feb 2004, which confirmed they had the virus, he said. It was not clear what happened to the remaining 11, but Teeraphon suggested that they had been buried by the owner. The owner is healthy but is being monitored because one of the cats used to sleep in her
bed, he said.

[ProMed Mail Moderator's comments - Dr.Zhiru Guo of the Laboratory of Animal Virology, Veterinary Institute, Changchun University of Agriculture & Animal Sciences, China, comments that the situation should be carefully watched, since after 1st passage through a mammal, transmission to another mammalian species, including humans, may be easier.]