February 15, 2009

 

 One-health wonders - February 15, 2009

 
 
posted February 1, 2009
 
Dr. Thomas G. Ksiazek
Dr. Thomas G. Ksiazek
 

Thomas G. Ksiazek, DVM, PhD, has seen some of the deadliest diseases on the planet.

As chief of the Special Pathogens Branch at the Centers for Disease Control and Prevention, Dr. Ksiazek led the agency's research of Rift Valley fever, Ebola, Marburg, arenaviruses and hantaviruses, severe acute respiratory syndrome virus, Nipah, and other viruses that cause severe disease in humans or livestock.

Shortly after graduating from the Kansas State University College of Veterinary Medicine, Dr. Ksiazek joined the Air Force, beginning a decades-long public health career that included a stint as head of the Rapid Diagnosis Department at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland. He's participated in efforts to control outbreaks of disease in Asia, Africa, and North and South America.

Dr. Ksiazek recently retired from the CDC for a job in academia: he's joined the faculty at the Galveston National Laboratory at The University of Texas Medical Branch.

How has your veterinary training helped your public health work?

I spent 21 years in the military, so all of my formal training in public health came after veterinary school. I was an Air Force officer for 13 years, and they had programs that sent folks back to graduate school, so the first set of training I did culminated in a master's degree in virology, particularly arthropod-borne viruses, and that got me started in a career interested not so much in veterinary problems but human health problems. I'd attribute a lot of that as direction from the (Defense Department's) use of veterinarians for public health or the health of operational troops. I did several tours of duty in Southeast Asia looking at arthropod-borne viruses and their impact on human populations. The ecology of these viruses often involves vertebrate animals so that the training of the veterinarian does fit in with that very well. Veterinarians employ their knowledge about animal populations, animal husbandry, and how people depend on animals, along with the human aspects. That's a real advantage.  

You've dealt with a number of "hot" pathogens around the world, including the Ugandan strain of the Ebola virus. What has your experience taught you about zoonotic diseases?

There are lots of "new" pathogens that aren't necessarily new. We find out about them in various ways, such as improving health systems in the developing world. These pathogens are not being created de novo; they're out there, and maybe we're identifying them at an increased rate. Most of these diseases come not necessarily from domestic species, although some incidents we've been involved in often involve (the pathogens) moving out of nature into a domestic species, and then becoming more of a risk to the human population. A good example of that would be Nipah virus in Malaysia. It naturally exists in bat (flying fox) populations but occasionally gets into other species. The outbreak in Malaysia had to do with this becoming a contagious disease among pigs. SARS has a sort of similar aspect to it where, again, a virus that appears now to have come from bat populations got transferred into wild species that were being raised for commercial purposes—raccoon dogs and civets—and then that got transferred, via the restaurant trade, into the human population.  

Contact with these pathogens increases as travel in the developing world increases. More and more people can travel from areas where, in the past, they probably would have lived their entire lives in larger cities that are connected to the rest of the world by airline flights. I can be in Atlanta or Galveston within less than a day from some of these remote sites. Ecotourism is another issue. It puts people in a situation where not only can these diseases occur but they can also be transferred to more populous areas where they can cause problems in large cities.  

Does this worry you?

There is a lot of concern about intentional introductions via bioterrorism, but history is pretty clear there are plenty of other naturally occurring problems out there. My tendency is to emphasize these naturally occurring events and that we invest in those and not spend all of our efforts and resources on biodefense programs. Pointed examples would include the large economic crises brought on by AIDS and SARS. These are real international security issues that result from naturally emerging threats rather than those brought about by our political adversaries.  

Why was the CDC's Special Pathogens Branch created?

In the 1970s, Lassa virus, Machupo virus, and other pathogens were the real-life equivalent to "The Andromeda Strain," which was a media event prevalent at the time. As a result, the government decided to make an investment in a team of scientists that could find out more about these pathogens, develop a knowledge base on them, and have special laboratory facilities that could support that knowledge base. Special laboratories were created to deal safely with these pathogens. On the civilian side, this work was carried on in Atlanta while the biodefense part was carried on at Fort Detrick.  

The question in the military and Special Pathogens Branch was how do you learn more about these high-hazard pathogens? It can be done in a couple of ways; in endemic situations, you can establish a field station and work with local health authorities trying to gain more in-depth understanding of the pathogen and its ecology. Then there's the emergence of new infections of some impact; when this happens, you provide assistance in epidemic situations. Both situations have been extremely profitable in learning more about the diseases and their natural maintenance. When you consider this era of bioterrorism, what we know about these diseases and threat agents largely comes from research by those at Detrick and Special Pathogens. They're not the only folks who do it, but they're among the most prominent and most successful.  

Given your decades of researching emerging infectious diseases, first for the DOD and then the CDC, what can you say about veterinary medicine's role in biosecurity?

There are aspects of veterinary medicine tied to agriculture security. Some diseases, if they were introduced into our livestock populations, would cut off our ability to trade with the rest of the world or greatly diminish our trading ability. That's where the primary focus is. Many of these diseases are zoonotic and may emerge in pet, wildlife, or zoo populations. West Nile virus encephalitis is a good example of this. Veterinarians are well-prepared and uniquely placed to deal with many of these circumstances.  

Do you feel it's necessary for more veterinarians to be involved in less traditional career fields, specifically virology and the epidemiology of vector-borne diseases?

I do. My career is more public-health oriented. I elected to go into the military; but, looking back on my career, I certainly employed my veterinary education. It was a benefit to the military, but it's helped me carry on in a career beyond the time I spent in the military—the public health arena, government, and now academia.  

Do you have any opinions about how to encourage more veterinarians into these areas?

Organizations like the AVMA should continue spotlighting how some folks contribute to public health, and that may help raise awareness. Field exercises where we're helping with epidemics—those types of exposures often turn people's career direction considerably. So opportunities for people to go abroad are key. There are opportunities for people to take short-term training experiences during their time at veterinary school, at the CDC, and other places where they can get a look at public health. More traditionally, veterinarians have been involved in activities like meat inspection. That's an important role, but it's not terribly exciting compared to some of the other aspects of public health.