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Information Sheet
Avian Influenza, Can It Infect Our Pets?

Can avian flu infect our pets?

There have been recent reports in the press about European cats becoming infected with bird flu. This has led to worry and panic among pet cat owners regarding their own health and the health of their companion animals. Although the current epidemic of bird flu in Asia and Europe is of concern it is not necessary to begin relinquishing our pets to shelters or for shelters to depopulate their animals. This article gives some basic background and the latest information on the current controversy regarding bird flu and pets. It also gives some basic advice to minimize spread of this virus in our pets and in shelters should this disease come to North America.

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 two 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 infection of domestic cats with avian influenza type A (H5N1) has been documented over the last few years both experimentally and "in the field" [1-3] . It has been further confirmed that domestic cats can be infected by eating infected birds, and that infected cats can spread infection to other cats, most likely through feces, urine, and secretions from the respiratory tract. In fact, cats are not the only mammal being infected with avian influenza. The science magazine Nature has learned that large numbers of domestic dogs tested in a Thai district may also be infected with the H5N1 strain of avian flu. So far, researchers at Bangkok's Chulalongkorn University have isolated the virus from at least one of the dogs [4] . There is no evidence at this time that dogs become sick or transmit avian influenza.

It may also be that cats and dogs getting infected with avian flu is not a new phenomenon. We are only now realizing it because of the scientific scrutiny imposed by the current epidemic. In January H5N1 was found in a kitten near a poultry outbreak in West Java. The virus from the kitten is closely related to recent H5N1 strains isolated from humans in Indonesia: it shares genetic changes found in human strains that are not present in samples from birds. But scientists may just be learning what already common knowledge among Indonesian villagers is. Apparently, locals have an onomatopoeic name for bird flu "that sounds like 'plop', the sound of a chicken hitting the ground when it falls out of a tree. They also have a name for the cat form of avian flu -- 'aaargh plop' -- because cats make a screaming noise before they fall out of the tree" [5] .

Influenza and ferrets

Ferrets are an excellent mammalian host for studies of influenza virus pathogenicity and host immunity, and the manifestations of influenza virus infection in ferrets closely resemble those in humans [6] . Studies have shown that H5N1 viruses that have been isolated from humans can cause severe disease in ferrets including lethargy, diarrhea, neurological signs and death [7] . Other researchers have demonstrated that there has been an increase in virulence of the 2004 human H5N1 isolates in ferrets compared with the 1997 human isolates and with the 2003 and 2004 avian isolates studied [8] .

It is therefore important for shelters to consider all their mammals and birds to be at risk should avian influenza be found in North America; in fact ferrets may be even more susceptible. Therefore, it is imperative to remember that control measures as outlined below be instituted for all species.

Tamiflu and other antivirals

There are basically two kinds of antiviral medications available that have shown efficacy against influenza viruses. These include the now well known neuramidase inhibitor oseltamivir (Tamiflu). There has been much discussion in the press regarding the use, disuse and stockpiling of this drug with several agencies raising red flags against indiscriminate use. Several reports of emerging resistance to Tamiflu have been published which should inspire us to devise pandemic strategies that do not favor the development of oseltamivir-resistant strains [9, 10] . Improper use of personal stockpiles of oseltamivir may promote resistance, thereby lessening the usefulness of our frontline defense against influenza, and should be strongly discouraged [11] . We must be careful that we do not expose circulating influenza to these drugs in such a way as to facilitate the selection of resistant viruses [11] . This includes not using this drug in domestic animals where it has not been shown to have any effect. Use of these drugs either for prophylaxis or treatment is highly discouraged in any shelter situation as it is unlikely to confer any benefit to the shelter population and could cause irreparable harm in being able to use antivirals in future human epidemics.

Clinical signs in cats and how to prevent infection if bird flu comes to N. America

Clinical signs of influenza virus infection in cats has only been seen in the laboratory or in wild felids infected in a zoo in Thailand [12] . In these instances the cats, tigers and leopards showed typical "flu-like" signs including fever, lethargy, protrusion of the third eyelid, conjunctivitis, and labored breathing/respiratory distress [13] . At necropsy lesions consistent with viral infection were seen in many tissues. At this time avian influenza type A (H5N1) has not been reported in North America. Therefore, any upper respiratory signs in a cat which are very common in shelters will not be caused by this influenza virus but rather by the more usual feline viruses and bacteria. In ferrets symptoms can also include GI signs such as diarrhea [7] .

While North America is still avian-flu-free it is prudent to begin thinking about preventative measures in our cats (and dogs) especially in shelters. Common sense dictates that cats, dogs and ferrets should be housed away from other species especially birds. This potential infectious disease is yet another reason to advocate keeping cats indoors so that they cannot come into contact with infected birds. It is also important to feed only cooked (whether home made or commercial) foods and to dissuade future adopters from raw food diets (especially poultry). It will also be especially important for shelters that treat or house wildlife specifically waterfowl. These birds housed separately from mammals as well as pet birds and personnel that handle them should not handle mammalian species without washing hands and changing gowns. However, should there be an outbreak of influenza here it is likely that treatment or housing of wild birds will be discouraged in shelters. A European health agency as recently published their recommendations for pet owners in areas where H5N1 avian influenza has been confirmed in wild birds. They also advise that stray cats and dogs found dead not be touched and that sick or dead pets that might have had contact with infected wild birds be inspected or have a necropsy performed by a veterinarian [14] .

There are many zoonotic diseases that shelter dogs and cats could potentially transmit to humans. It is imperative that we not forget about some of these conditions as these are much more likely to cause problems than the threat of influenza. These common infections include intestinal parasites, external parasites and gastrointestinal flora e.g. salmonella. Good hygiene and infectious disease management is always of prime importance in shelters and good protocols will go a long way in containing any future influenza problems.

Summary of recommendations for prevention of avian influenza in pets and shelters

At this time the current Asian strain of avian influenza H5N1 has not been reported in North America. In the case that this virus does appear on this continent, the following will be advised:

DO NOW

Ensure that good sanitation and disinfection protocols are in place and that products effective against influenza virus are in use in all areas of the shelter.
Remember that current upper respiratory infections in shelters are NOT avian influenza. This will probably be true even if the avian flu epidemic comes to these shores.
Stay informed and keep abreast of current, well documented information and publications about avian influenza. Be careful of unverified reports and panic-mongering on the internet.
Institute good rodent control as mice can be infected with influenza viruses.

BEGIN IF AVIAN INFLUENZA IS IN NORTH AMERICA

Keep pet cats indoors to prevent direct contact with potentially infected wild birds. It appears that cats become infected by eating these birds not e.g. via "wind blown virus".
Do not keep poultry at shelters.
Keep dogs on a leash to avoid contact with dead birds.
Do not feed pets raw food especially poultry.
Do not allow pet birds to come into contact with wild birds - consider alternatives to outdoor aviaries.
Keep ferrets indoors and do not house them with cats in shelters.
For shelters doing wildlife rehabilitation make sure there is no contact between them and domestic animals either directly or via fomites.
Do not touch dead cats that may have come into contact with wild birds. Have their carcasses inspected by a veterinarian or according to prevailing government regulations.
Temporarily reconsider feral TNR programs if avian influenza is being found in your area.

References

1. Rimmelzwaan, G.F., et al., Influenza A Virus (H5N1) Infection in Cats Causes Systemic Disease with Potential Novel Routes of Virus Spread within and between Hosts. 2006. Am J Path. 168 (1): p. 176-183.

2. Songserm T, A.A., Jam-on R, Sae-Heng N, Meemak N, Pariyothorn N, et al. , , and Avian influenza H5N1 in naturally infected domestic cat. . Emerg Infect Dis Apr. 2006. 12 (4).

3. Kuiken, T., et al., Avian H5N1 Influenza in Cats. 2004. Science 306 (5694): p. 241.

4. Butler, D., Thai dogs carry bird-flu virus, but will they spread it? Nature, 2006. 439 (7078): p. 773-773.

5. Butler, D., Can cats spread avian flu? Nature, 2006. 440 (7081): p. 135-135.

6. Zitzow, L.A., et al., Pathogenesis of Avian Influenza A (H5N1) Viruses in Ferrets. 2002. J Virol. 76 (9): p. 4420-4429.

7. Govorkova, E.A., et al., Lethality to Ferrets of H5N1 Influenza Viruses Isolated from Humans and Poultry in 2004. 2005. J Virol. 79 (4): p. 2191-2198.

8. Maines, T.R., et al., Avian Influenza (H5N1) Viruses Isolated from Humans in Asia in 2004 Exhibit Increased Virulence in Mammals. 2005. J Virol. 79 (18): p. 11788-11800.

9. Kiso, M., et al., Resistant influenza A viruses in children treated with oseltamivir: descriptive study. The Lancet. 364 (9436): p. 759-765.

10. de Jong, M.D., et al., Oseltamivir Resistance during Treatment of Influenza A (H5N1) Infection. 2005. New Eng J Med. 353 (25): p. 2667-2672.

11. Moscona, A., Oseltamivir Resistance -- Disabling Our Influenza Defenses. 2005. New Eng J Med. 353 (25): p. 2633-2636.

12. Keawcharoen J, O.K., Kuiken T, Fouchier RAM, Amonsin A, Payungporn S, et al., and Avian influenza H5N1 in tigers and leopards. Emerg Infect Dis. Dec.2004. 10 (12).

13. Thanawongnuwech R, A.A., Tantilertcharoen R, Damrongwatanapokin S, Theamboonlers A, Payungporn S, et al. , Probable tiger-to-tiger transmission of avian influenza H5N1. Emerg Infect Dis. May 2005 11 (5).