Contributing Editor Jordan Schaul looks at the “hype” surrounding the recent epidemic of swine flu, its ecology, and nomenclature system, and the perception concerning emerging influenza strains in the context of domestic and exotic animal species.
As a zoo aficionado, and professional, I’m always concerned that novel strains of influenza—those infecting people, but of animal origin—will give some of my favorite zoo animals with domestic cousins a bad reputation.
Take the red river hog of West Africa’s Congolian forests or the African pygmy goose of the sub-Sarharan region. These charismatic species, which happen to be of African descent, are popular among zoo patrons, but are also potential hosts and “vectors” of influenza, just like their domestic relatives.
Although North American zoo populations are monitored and extremely healthy, the news of swine or avian flu tends to keep people at bay. When you hear of an outbreak of swine or avian flu or another novel flu strain, you may, albeit unwarranted, be reluctant to visit your local zoo. However, zoological parks are closely monitored. In fact, there is an Avian Influenza Surveillance System coordinated by epidemiologists with USDA Animal Care and the Zoo Animal Health Network (ZAHN). They work together to prepare for the risk of highly pathogenic avian influenza.
“The goals of the program are to:
• conduct active surveillance of avian influenza in zoos (surveillance);
• provide the zoological community with an Outbreak Management Plan to assist State and Federal regulatory officials with handling of an outbreak of highly pathogenic avian influenza H5N1 on zoo grounds (outbreak management);
• provide an updated Vaccination Plan for zoological specimens should an appropriate vaccine be identified for use in zoos (vaccination).
• facilitate dialogue between individual zoological institutions and appropriate State and Federal regulatory veterinarians, who would work together to manage an avian influenza outbreak.”
The recent discovery of seal flu this year set somewhat of a precedence. Novel flu strains may emerge in unexpected wildlife populations presenting possible risks to animals and people that were otherwise unanticipated.
I joke that in an effort to avoid catching the flu this season, I’m convinced that you should avoid touching anybody or anything. That’s easy enough, right?
Rather than review the standard nomenclature for Orthomyxoviridae or read influenza epidemic updates online—neither of which you probably do—you could learn how to properly don and remove latex gloves, wash your hands and avoid contact with all birds and mammals, including other people. Oh, and don’t forget a flu shot. Perhaps then, we won’t have to pick on swine, and certainly a host of land-based avifauna and a number of other miscellaneous species.
Influenza really becomes dangerous when transmission occurs between people—when you are dealing with a highly contagious and potentially “pathogenic” strain. However, this divergent group of viruses are zoonotic, that is transmissable between animals and people, and often emerge in animal species, where they mix and jump from host species to host species.
Global climate change and continued encroachment on wild habitat exacerbates the dangers of emerging viral diseases like novel flu strains. Both of these factors potentially place wild and domestic animal reservoirs of disease in a precarious situation as there are implications for how we handle known infected populations of animals. They also place humans at great risk.
Flu strains are endemic in wild populations of birds and mammals, where they may in fact, cause few signs of disease. But as with other zoonotic agents, these pathogens may find their way into domestic populations where exposure to people is high, transmission of disease more likely, and the pathogenicity of the disease more severe. As is often the case, we have no other choice, but to cull numbers of animals to protect other animals and people from becoming infected.
In the case of influenza, things get a little more complicated. Host species essentially become mixing vats, and as mentioned the disease agent may jump from one animal species host to another. With influenza, which is comprised of a group of segmented RNA viruses, an infection with mixed strains can lead to genetic reassortment, a special kind of antigenic shift, which translates into an exchange of genetic material. The new reassortant strain shares properties of parental strains. For example, the 2009 swine flu (H1N1) was the result of a triple reassortment and contained a mix of swine, avian and human influenza genetic sequences and caused a pandemic outbreak.
Influenza A viruses are classified by the antigens on the surface of the viral disease particles themselves. An antigen is what induces an antibody response by a host’s immune system. For all intents and purposes, influenza A and B are most important to people as they cause seasonal epidemics.
Where Influenza A is classified by its surface glycoproteins into subtypes, which have multiple strains and potential to produce more, Influenza B is the only member of its genus. Like Influenza A, it also has in multiple strains and potential to develop into more strains through a process known as antigenic drift.
The Influenza C virus is the only member in the genus and rarely causes flu in humans. Although it may cause disease like genera represented by types A and B, the symptoms or signs, in the case of animals are usually mild. Influenza C is known to infect both humans and suids (pigs).
Wild bird populations are thought to be the natural reservoirs of Influenza A viruses. These viruses have commonly infected domestic animals including poultry, horses, pigs, a number of other mammal species and humans. Infections in livestock are particularly noteworthy because of the exposure humans have to these animal populations.
Influenza B, like C is the only “species” of its respective genus, and so far has been reported in humans and seals.
For an update on this recent outbreak of swine flu, please read this Associated Press report.