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Are Pen-Reared Quail A Disease Threat To Wild Birds?

by Thomas H. Eleazer, DVM

Introduction by
Jim Evans, Consulting Biologist

Dr. Tom Eleazer received his degree of Veterinary Medicine from the University of Georgia in 1958 and served Clemson University as a veterinary pathologist, studying poultry and game bird diseases for 31 years. Tom is still actively applying his skills as a poultry and game bird disease consultant. In the past he has served as president of the South Carolina Wildlife Federation, served on the advisory board for the Institute of Wildlife and Environmental Toxicology, and also as a member of the Wildlife & Freshwater Fisheries Advisory aaBoard for the South Carolina Wildlife Commission. He was instrumental in the development of the vaccine for “quail pox.” Now let’s hear what he has to say about the question:

Are pen-reared quail a disease threat to wild birds?

This question seems to remain on the mind of some quail managers and sportsmen throughout the Southeast. It comes up anytime landowners are considering the release of pen-reared birds on their property.

My remarks in this article are based on 39 years of experience with game bird and poultry disease diagnosis and research. I have dealt with both pen-reared and wild bird diseases. In 31 of these years I was with the Clemson University Livestock-Poultry Disease Diagnostic Laboratory. During all this time I have yet to see a disease condition in wild bobwhite quail that could be traced to pen-reared birds being released into a wild environment. In the space allotted me in this article, I will address a few diseases that seem to be causing the most concern.

Ulcerative Enteritis (UE)
First, let’s talk about the most common disease of pen-reared bobwhite quail, ulcerative enteritis (UE). This disease can be devastating in pen-reared birds. A study that was funded by the North American Game Bird Association at Mississippi State University showed that several other anaerobic bacteria including some genera of Bacillus could also cause this disease, previously thought to be caused by the bacterium Clostridium colinum. While UE could in all probability be spread by filth, it has been shown that this doesn’t have to be the case. In fact, the causative organisms are carried in the gut of all bobwhite quail. When the birds are stressed, the organisms reproduce, and the bird gets sick. My theory is that UE may well be a part of the natural mortality experienced by wild quail especially during the time of late winter stress. However, I have never been able to prove this, since in the wild sick or weak birds are quickly removed by scavengers.

Quail Pox
Quail pox is another disease that concerns many people. This is a viral disease that seemed to emerge in the late sixties or early seventies. It caused quite a bit of problem for the game bird growers. For a number of years, I have been examining wild quail harvested on a large South Carolina plantation, where there are no records of pen-reared quail ever being released. During the mid-eighties, this investigation revealed the presence of pox lesions in about 6 percent of the specimens. These were the highest levels. Since then the presence of pox lesions has decreased to a background level of plus or minus 1 percent. In a further effort to prove this virus already existed in the environment, disease-free bobwhite quail, raised in isolation, were placed in the field in cages on this and a neighboring plantation. Within two weeks the control birds were showing pox lesions. Therefore, this virus appears already be naturally occurring in the coastal plain. I feel that quail pox poses little or no additional threat to wild birds through the introduction of released quail. It is recommended that all pen-reared quail used in release projects be immunized against quail pox. This not only will prevent pox from being brought in to the wild birds, but will also prevent released birds from contracting pox from any infected native birds.

What about coccidiosis? I have done quite a few checks for internal parasites in both wild and pen-reared birds over the years. I have found that this protozoan exists at low levels in most wild quail populations. Medications are used to control this threat in young pen-reared quail. Healthy, well-managed pen-reared birds are probably less of a coccidiosis threat than their wild counterparts.

Another protozoan named Cryptosporidium causes this disease, and it specifically infects bobwhite quail. In the confinement of a flight pen, it can infect and kill up to 100% of the quail. It is similar to coccidiosis but more severe. As part of an in-depth investigation of avian crytosporidiosis, workers at North Carolina State University conducted studies on the incidence of this disease in wild bobwhite populations. Of 424 samples from wild quail, 3.1% yielded Cryptosporidium oocysts. This was a random sample from a “normal healthy” wild population. This finding appears to tell us that Cryptosporidium is already present at low levels in the environment. With this in mind, I feel that the release of healthy bobwhite quail poses little or no threat to wild populations. This disease can be devastating in pen-reared birds while in confinement, but thankfully it is not common in occurrence.
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