October 2010
From the State Vet's Office

Emerging Zoonotic Diseases


“Get that out of your mouth, Son. You don’t have any idea where that might have been.” Did you ever hear that order given when you were a small child? You would have if you had grown up around my house. It’s not that my parents were germophobes. They just understood disease-causing germs could be carried on objects other people had handled like pennies and other loose change or the toys in the nursery at church or even my thumb on occasions.

The same line of thinking would occasionally result in such urgent instructions as, “Take that rat outside NOW and get rid of it and wash your hands with soap” or “Don’t let that dog lick you in the face. You don’t know what he’s been eating.” That advice, along with “Wash your hands” had pretty much covered basic sanitary practices that would at least minimize a lot of illnesses we could have suffered had the advice gone unheeded. Animals have always had some role in many human diseases.

Emerging diseases are those that have never been known to exist before or those that have existed for a while, but all at once begin to cause a significant amount of illnesses. A disease like leprosy would be considered a re-emerging disease if we began to see large outbreaks of it, especially in some place like North America. Emerging diseases are particularly troubling because there is often no natural immunity nor is there a vaccine against the disease readily available. Back in the late 1970s and early 1980s, canine parvo virus was an emerging animal disease that turned the dog world on its side. While parvo is not a virus that can affect humans or even animals outside the canine family, it made its appearance on the scene and devastated the dog populations.

 Where did the disease come from? Nobody really knows but it is widely speculated it came from a mutated cat virus, feline panleucopenia. Emerging diseases often occur when an established and familiar virus mutates so it can infect and cause disease in species other than its normal host.

A zoonotic disease is one that normally exists in animals but can also infect humans. The disease organism doesn’t even necessarily have to make the host animal sick. Let’s go back to leprosy. The bacillis organism causing leprosy has been found to live in armadillos. This is usually not a problem and only rarely have there been documented cases of human leprosy that were likely associated with close exposure to the pesky animals.

There is also some suggestion that eating undercooked armadillo meat has lead to the human disease…..do people actually eat armadillo? Rabies, salmonella, E. coli, West Nile virus (WNV) and Eastern Equine Encephalitis are all examples of zoonotic diseases.

I am concerned with emerging zoonotic diseases for two reasons. First, I am concerned because I am a human, which could leave me on the unpleasant end of these diseases. Second, and most importantly, my job affords me the ability to affect many of these diseases as they occur on the animal level. We have public health personnel who actually deal with the diseases as they affect humans. Our State Public Health Veterinarian, Dr. Dee Jones, is very involved with diseases and prevention in such diseases as rabies, WNV and other zoonotic diseases from the human side.
 
We at the Department of Agriculture and Industries play an important role using our veterinary diagnostic laboratories for surveillance and early diagnosis of zoonotic diseases as they occur in animals. Some examples of these diseases include WNV, psitticosis in birds, avian influenza (bird flu) and many other diseases making their way from the animal ranks into humans. One such disease is leptospirosis. Lepto, as we refer to it, is accounting for an increasing number of human cases. We have, for years, vaccinated cattle and even dogs against lepto.

Bird flu, the SARS virus, the H1N1 (so called swine flu) and WNV are all examples of emerging zoonotic diseases. In fact since the 1950s, zoonotic diseases have caused about 65 percent of what are considered to be emerging diseases. Other diseases have been traced back to animal origin, although they are not considered to be zoonotic because they do not infect or cause disease animals. The HIV (human immunodeficiency virus) causes AIDS, a disease that came on the scene in a big way in 1981. It was long speculated the virus came from monkeys. Finally, a group of international researchers found the virus in a group of chimpanzees in Africa. It is believed the cross-over to humans occurred when humans hunted the chimpanzees for meat and were exposed to their blood.

The point I want to make is that we have likely not seen the last new disease that will appear on the scene sometime in the future. And there is a good chance it may be a zoonotic disease. In a time when world travel is almost as common as the house fly and people are choosing more exotic animals as pets (remember the giant Gambian rats causing monkey pox), we have not heard the last of emerging zoonotic diseases.

We veterinarians play a role in identifying and containing those diseases at the animal level. Many parasites common in dogs and cats are zoonotic. So even if you do not catch and eat wild birds or eat road kill, when your veterinarian suggests you deworm your pet, go ahead and do it. On the regulatory level we are continually carrying on surveillance activities and enforcing regulations keeping zoonotic diseases on the proper side of the fence.

I wish I could tell you I do things to protect people from diseases caused by chimpanzees and armidillos, but they are outside my realm of responsibility. However, I would offer this bit of unofficial advice: if you are going to eat armadillo or chimpanzee, wear gloves when you prepare them and cook them WELL DONE..... EXTREMELY WELL DONE!!!!