Panleukopenia and Distemper
Dr. John Ellis is a Professor of Microbiology at the University of Saskatchewan's Western College of Veterinary Medicine and a well-known expert on vaccine safety and efficacy. In the following interview, Dr. Ellis gives his thoughts about the recent outbreaks of distemper and feline panleukopenia.
DVMvac.org An alarming story out of Michigan this summer states that hundreds of cats were infected with feline panleukopenia. At least 800 cats died. Distemper outbreaks have also been reported in other areas of the country. Are panleuk and distemper outbreaks becoming more common?
Dr. Ellis In speaking with experts at Michigan State University, the feeling is that the panleuk outbreak in Saginaw may be attributable to a couple of different things: A feral cat population that was unvaccinated and also possibly an apparent lapse in vaccination due to economic reasons. Many of these cats actually were owned or from areas that are economically depressed, so that might have affected routine vaccination.
DVMvac.org Can you explain how the economy of a community can affect whether or not pets are protected from disease?
Dr. Ellis There are probably at least three interpretations for this kind of thing. First of all, there could be the emergence of new or more virulent isolates of those particular pathogens. That's a possibility, although I don't think that it is very likely in this case. Another possibility could be a lapse in vaccination due to economic reasons. A population of feral cats or dogs that aren't vaccinated is a second possibility. And a third possibility could be that, with the new recommendations for protocol change and all the hype on the Internet about over-vaccination, that this could be the leading edge of problems due to lack of herd immunity.
DVMvac.org Do you believe extended protocols will result in pet owners failing to take their pets in for veterinary checkups?
Dr. Ellis I'd like to emphasize that we don't know. It's all speculation at this point, but I think it's an interesting association with all the veterinary schools now recommending essentially three-year protocols for the core vaccines that these apparent outbreaks are emerging. I don't think it's only Michigan. I have heard that other states have had similar problems, with panleukopenia especially. But again, this isn't well documented, unfortunately. That's often the case in veterinary medicine. We just don't have very good documentation of what's happening in the field in terms of the actual disease problems.
DVMvac.org Do the recent panleuk and distemper outbreaks lend support to your argument about the dangers of going to extended vaccine intervals?
Dr. Ellis Well, it certainly could, but I'm not saying it necessarily does. We don't know at this point. It could be a that a similar prevalence of disease has happened along the way and it hasn't been reported, but I don't think something as dramatic as losing 800 cats, apparently to one disease over a relatively short period of time goes without being noticed.
DVMvac.org Are the outbreaks warning signs the veterinary profession should pay attention to?
Dr. Ellis I think they are, yes. From what I can tell, it's made people sit up and take notice which is very different from what's happened in the recent past. If it wasn't different, I think the likelihood that it would be publicized is not that great. If people who are working in shelter environments were experiencing losses that they were used to, I don't think it would have been publicized as much as it has been.
DVMvac.org What do you suggest veterinarians do to ensure their clients receive regular wellness exams?
Dr. Ellis I guess it goes back to what I've been saying all along. The recommendation for annual vaccination seems to work very well. Again, what's forgotten is the frequent disconnect between recommendation and reality; in fact many people didn't come in every year, even though the recommendation for annual vaccination was in force. If we say every three years, then it's easy for people to forget. That's the problem that's been recognized or at least talked about in passing, at least in the background of this debate. I think incidents like the recent outbreaks in Michigan could be evidence that, in fact, it is difficult to get people back in to the clinic. The vaccination of pets may lapse. In addition, I don't think it's only the change in recommendations that could be responsible here. It could be the Internet and the general tendency to forget that the reason we don't have much infectious disease in the developed world where people and animals are routinely vaccinated is because of that, because of routine vaccination.
DVMvac.org Which factors put a cat at risk for feline panleukopenia?
Dr. Ellis Maybe stress, increased stress. For example if, there's a big feral cat population and there's not a lot of food available. There might be increased fighting. Certainly stress is a common co-factor of disease. The levels of stress might change depending on either environmental conditions or the population density in the area; things like that. But again, it's difficult to actually pinpoint something in this case.
DVMvac.org Is there a risk to pet owners from cats that contract panleukopenia virus?
Dr. Ellis No. Although the dog parvo virus did emerge from a small mutational change in the cat virus that allowed it to "jump" to another carnivore host, emergence of a new virus that could infect humans would be unlikely. We wouldn't expect it.
DVMvac.org What treatment is available for cats that are infected with panleuk? Do they have to be euthanized?
Dr. Ellis Really, the only treatment is supportive care, such as fluid therapy, and giving the cat antibiotics to prevent secondary bacterial infections. And really, it's probably not the virus that actually kills the cats. It's bacterial infections. There's significant damage to the GI tract, which allows bacterial products, endotoxins, to get into the system. That's probably actually what kills the cats. And so, if a cat isn't very well cared for to begin with, gets the virus infection, gets damage to the intestine, and isn't given good supportive care, then the likelihood of it dying is greatly increased.
DVMvac.org In regards to distemper, is euthanizing an infected animal the only recourse to protect the general population?
Dr. Ellis There are very few virus infections for which there are specific antiviral drugs. So it's very difficult to treat a viral infection, aside from preventing or trying to prevent secondary bacterial infections. The same thing can be said for distemper. If dogs are raised in germ-free environments and given the distemper virus, they get sick, but they don't become near as sick as they do when they're exposed to secondary infections. Both panleukopenia virus and the distemper virus are classic immunosuppressive agents. So what they do is not only cause direct tissue damage to the various organs in which they grow, but they also suppress the immune response. So, that's part of the whole syndrome; secondary infections.
DVMvac.org In other interviews, you have stated that science to date does not support extended protocols. How do you view the issue now?
Dr. Ellis I think the recent outbreaks of panleuk and distemper may unfortunately be the best documentation for whether a protocol works or not. Whether or not a protocol is going to work in a population has to be tested by history. These incidents could be interpreted to support the idea that the recommendation for annual vaccination is the correct one. In human medicine, there is a huge infrastructure and a lot of human and monetary resources to report disease and associate responses to vaccination efficacy. That's very difficult to do in veterinary medicine. So I think we're left with the alternative, which is essentially to just try it, and if it works, you'll see nothing, no disease, or very little disease. If your protocol doesn't work, then you're going to see disease. Maybe this year's outbreaks are an indication that the new vaccine recommendations - which are being taken up probably increasingly - aren't correct.
DVMvac.org In your opinion, do annual vaccinations remain the gold standard for maintaining optimum pet health?
Dr. Ellis In terms of prevalence and incidence of infectious disease, which has been low in vaccinated populations, the annual vaccination recommendations seem to work at the population level. Whether or not the newer protocols are going to work, I think, is still in question. This year's outbreaks of panleukopenia and distemper might be an indication that maybe it isn't going to work as well as some people thought it would.