H5N1 in cats
8 March 2006
At the end of February 2006 highly pathogenic avian influenza (HPAI), caused by the H5N1 virus was detected in a domestic cat found dead on the northern island of Ruegen, Germany. Since mid-February, over 100 birds have died on this island and tests confirmed H5N1 infection. Also in Asia, cats and other felidae have been occasionally found to be infected with H5N1 since the start of the poultry epidemic in 2003. Experimental studies have shown that the domestic cat can become infected with the virus and that cat to cat transmission is possible in principle. The virus causes respiratory disease which can lead to death in all cat species. Serological studies in several Asian countries suggest that dogs may also contract the H5N1 infection. Countries in Europe have advised owners of pets living near H5N1 wild bird foci to keep cats indoors and dogs on a leash when taken for a walk.
These recent events lead to many questions by the public and pet owners to which the veterinary profession has to respond. In addition, there may be exposure of pet owners and veterinarians. For example, when animals infected with H5N1 (eg birds, dogs and cats) are brought to the veterinary clinic. Important are also the contribution veterinary practitioners can make in the surveillance of the disease for the presence of the H5N1 infection.
This section provides information for the general public and professionals about the risk of cats contracting H5N1 virus and the role of cats in the spread of avian influenza H5N1.
During a H5N1 outbreak in poultry in 1997 in Hong Kong, the first clinical human cases of this sub-type were reported with several fatalities. From the end of 2003 to date (March 2006) 173 people have been confirmed infected with the H5N1 virus of which 93 have died. Except for 1 case, human-to-human transmission has probably not occurred. Although H5N1 is relatively common to wild birds and poultry, humans and other mammals are also at risk of HPAI infection. Highly pathogenic avian influenza in poultry is of growing concern due to the current geographic extent comprising Asia, Africa and Europe showing potential for pandemic spread. The virus is highly contagious and already over 200 million domestic birds have either been culled or died of the disease. Table 1 shows the timeline for avian influenza in cats and other felidae.
|Timeline of (H5N1) avian influenza in cats and other felidae (and civets)
|1970s & 1980s
||Research revealed that infection of domestic cats with influenza A subtypes H3N2 from humans, H7N3 from a turkey, and H7N7 from a harbor seal (Phoc vitulina) produces transient virus excretion and a temporary increase in body temperature but did not induce any other clinical signs of disease.
||Two leopards and two tigers died at a zoo in Thailand after feeding on chicken carcasses. Investigation confirmed H5N1 in tissue samples from all 4 animals. This was the first report of influenza causing disease and death in big cats.
||Research shows that domestic cats experimentally
infected with H5N1 develop severe disease and can spread
infection to other cats.
||A H5N1 outbreak in zoo tigers in Thailand reportedly
fed on chicken carcasses. Eventually, 147 out of the
population of 441 tigers died or had to euthanized for
animal welfare reasons.
||Tests on three civets that died late June 2005 in
Viet Nam revealed H5N1, marking the first infection
of this species with the virus. These endangered Owston’s
palm civets were raised in captivity; source of infection
is still unknown.
October 05 February 06
||FAO field veterinarians report unusual high cat mortality
in Iraq and Indonesia in the vicinity of H5N1 outbreaks
28 February 2006
||H5N1 confirmed in a cat on the Baltic Sea island
of Ruegen (Germany). Over 100 wild birds had been found
dead on the island during previous weeks.
Role of cats in virus transmission
Research has shown that domestic cats may die from H5N1 virus. Also horizontal transmission has been proven. However, it is unlikely that cats play a role in the natural transmission cycle of H5N1 viruses. Cat infections occasionally occur in association with H5N1 outbreaks in domestic or wild birds, e.g. when cats feed on infected birds. Experimental/infected cats shed the virus via the respiratory and intestinal tract, and may therefore transmit the virus to other cats. Naturally infected cats are thus in theory, able to spread the virus.
In areas where H5N1 Infected wild birds are reported it can not be excluded that cats become infected. Although most wild birds infected are waterfowl, not normally the species cats interact with, H5N1 is potentially infectious to numerous other bird species and it can not be ruled out that passerines or pigeons which do interact with cats get infected.
In areas where poultry is infected with H5N1 there is a risk that cats become infected with H5N1 through contact with infected poultry or their faeces. Anecdotal reports support the notion that contact with infected poultry (faeces and eating infected carcasses) forms a source of infection for cats. Cats probably have little or no contribution to the spread of the disease because the number of infected poultry is much higher than the number of infected cats; poultry shed much more virus than cats. Nevertheless, cats may play a role in the spread of the virus to other animals. Report to the local veterinary authority any evidence of significant animal mortality both wild and domestic.
Theoretically there is a possibility that cats transmit infection to humans. However, given the risk that cats become infected with HPAI is low, the risk to human infection is therefore limited.
The role of stray cats
Due to their greater mobility, stray cats could spread the disease into new areas. If infected, stray cats may become a source of contamination to poultry and mammals, including humans.
The role of other mammals
The ability of catching the H5N1 virus is not restricted to cats. Reports show infection in tigers, leopards and civets. Also dogs and pigs may become infected with the virus. Given the broad host spectrum of the H5N1virus, the possibility that also other wild or domesticated mammals including seals, mustelidae or furbearing animals, become infected by contacting infected animals is present. All carnivores could become infected through eating infected poultry or infected wild birds.
Areas where H5N1 HPAI has been diagnosed or is suspected in poultry or wild birds:
- Report to the local veterinary authority any evidence of significant bird mortality both wild and domestic.
- Be especially vigilant for any dead or sick cats and report such findings to the local veterinarian.
- Make sure contact between cats and wild birds or poultry (or their faeces) is avoided and/or keep cats inside.
- If cats bring a sick or dead bird inside the house, put on plastic gloves and dispense of the bird in plastic bags for collection by local veterinary animal handlers.
- Keep stray cats outside the house and avoid contact with them.
- If cats show breathing problems or nasal discharge, a veterinarian should be consulted.
- Do not touch or handle any sick-looking or dead cat (or other animal) and report to the authorities.
- Wash hands with water and soap regularly and especially after handling animals and cleaning their litter boxes or coming in contact with faeces or saliva.
- Dogs can only be taken outside the premises if kept restraint.
- Do not feed any water birds.
- Disinfect (e.g. with bleach 2-3 %) cages or other hardware in which sick animals have been transported or been in contact.
- Wash animal blankets with soap or any other commercial detergent.