The SARS-CoV-2 coronavirus, which causes the disease COVID-19, appears to be zoonotic, having transferred to humans from wild animals. Diseases can also pass from wildlife to pets, zoo animals and companion animals, including a small number of dogs and cats that have contracted COVID-19. This phenomenon of one non-human species passing one disease to another can be called spillover. Those animals do not need to be in direct contact with each other for spillover to occur. On July 25 and 31 last year, health officials confirmed highly pathogenic avian influenza A(H5N1) infections at two cat shelters in Seoul, South Korea. A team of researchers analyzed this outbreak and published a summary in Nature Communications, along with suggestions for controlling future cross-species disease transmission.
“The outbreak of influenza A(H5N1) in cat shelters in South Korea, together with the increasing number of reports of influenza A(H5N1) infection in mammals, suggests the need to improve the effectiveness of surveillance and prevention to infectious disease in any setting where a group of potentially susceptible animals is kept in close contact,” they wrote. “This is particularly important for groups of animals not normally covered by regulatory efforts aimed at maintaining or improving animal health and welfare standards. These animal groups can not only provide environments for cross-species viral transmission, promoting zoonotic risk, but can also serve as sentinels for detecting such events, in thus offering opportunities to assess and subsequently mitigate such risk.”
H5N1 avian flu can spread and kill people. Between 2003 and 2023, the World Health Organization received 882 reports of human infection with H5N1 bird flu in 23 countries. Of these, 461 cases were fatal. Interspecies transmission of diseases can also be fatal for animals.
South Korean bird flu outbreak in shelter cats
In a case last year at one of the cat shelters in South Korea, 38 out of 40 infected cats died within a month. The shelter cats are all kept indoors, so it seems unlikely that wild birds spread the pathogen to the cats. Instead, the virus can spread to cats through their food. South Korea’s Ministry of Agriculture, Food and Rural Affairs (MAFRA) investigators discovered the influenza A(H5N1) virus in cat food from one of the shelters. The cat foods are Balanced Duck and Balanced Chicken produced by Nature’s Raw at its facility in Gimpo, west of Seoul. The Ministry said the company had failed to follow the necessary sterilization measures since May 25 due to equipment malfunction. MAFRA officials then ordered a recall of all batches of cat food deemed at risk of harboring the virus. About 13,200 units have been sold to 286 pet owners. However, these pet owners reported no signs of infection in their cats.
The virus may have entered the cat food stream during a virus outbreak in South Korean poultry, including duck, farms that lasted until April 2023. Although it seems likely that these farm infections were may be the source of the virus that infected cats , the authors of the Nature paper noted that there is no definitive evidence released by MAFRA. It is also not known if cats also spread the virus to each other, or if the disease always comes from cat food.
No person who came into contact with the cats tested positive for avian influenza. Although cats can carry highly pathogenic avian influenza, epidemiologists believe that cats are not an important vector for the disease and do not play a major role in the transmission of avian influenza to humans or others. more animals.
Avian influenza infection of cats
Avian influenza or bird flu spreads naturally among wild aquatic birds around the world and can infect domestic poultry and other bird and animal species, according to the World Health Organization. Highly pathogenic avian influenza is a subtype of the virus. It can cause severe illness and high mortality in domestic poultry and wild birds. Viruses can devastate poultry industries and have economic impacts due to trade restrictions. Some varieties, including H5N1, can cross species barriers and can cause serious disease in mammals.
In June, Poland’s IHR National Focal Point notified the World Health Organization of the unusual death of cats across the country, suspected to be caused by highly pathogenic avian influenza. As of July 11, 47 samples were tested from 46 cats and one captive caracal. Twenty-five samples tested positive for H5N1 avian influenza. Fourteen cats were euthanized. An additional 11 died with the last death reported on June 30. Some cats developed severe symptoms, such as difficulty breathing, bloody diarrhea and neurological signs. Some of the cats quickly deteriorated and died. In total, 20 cats had neurological signs, 19 had respiratory signs and 17 had both signs.
Surveillance and control of disease spillover in domestic cats and dogs
Outbreaks of H5N1 avian influenza in shelter cats are rare. The fact that the cats were in one place may have been a major reason why the disease was discovered as the culprit, the study authors wrote. In individual households, a cat infected with avian flu may have been diagnosed with another, more common disease. Multiple cats suffering from the same disease are easier to observe in a shelter. Also in a home, the virus would not have the opportunity to spread to different animals, if that ever happened.
Considering the outbreak of avian influenza A(H5N1) in South Korea, scientists have made suggestions to prevent future disease outbreaks and reduce zoonotic potential.
1. Require animal shelters to systematically record adverse animal health events at the individual animal and group level. In outbreak situations, pet shelters should also record environmental factors (eg access to/from wildlife, and introduction of new animals) and husbandry conditions (eg food and water sources ).
“In the event of cross-species viral transmission, this information will help to better understand the source of the infection and thus inform the implementation of prevention and control measures,” the scientists wrote. “Such recording skills seem to be lacking in these particular settings, in stark contrast to conventional livestock farming where recording is routinely done.
2. Training shelter staff to report any unusual clinical signs or trends in the health of shelter animals. Animal health authorities need to clearly define reporting criteria and ensure that shelter staff are familiar with those criteria.
3. The potential of undercooked poultry to transmit avian influenza justifies banning or limiting the feeding of raw meat to animals kept for unusual production purposes, such as animal shelters and fur farms , and those in non-agricultural environments. These restrictions may reduce the risk of cross-species transmission of influenza A(H5N1) virus and other viruses.
4. Continue discussing how to implement measures to prevent and control cross-species viral transmission.
“It is important to involve all relevant stakeholders in this discussion, especially the staff of the aforementioned animal settings, as their understanding of the implications of animal husbandry for animal and human health is may be lower than those involved in conventional livestock farming,” they wrote.
