Why should we care about parasites?
Parasites are a part of life as a wild animal, right? Could they really be contributing to population level declines in quail? The answer is: yes, they could, but we do not know for sure if this is the case in quail. The truth is that disease as a regulatory factor in wildlife populations has long been ignored for reasons that most cannot adequately explain. Even as far back as 1933, Aldo Leopold, remarked in his book Game Management that “the role of disease in wild-life conservation has probably been radically underestimated.” In populations where disease has been investigated as a potential limiting factor, the results have been surprisingly conclusive. The most famous example of this is the work done by Dr. Peter Hudson and his colleagues on red grouse in Scotland. They were able to prove that parasitic cecal worms were driving population fluctuations in red grouse. Dr. Hudson and his team developed an effective method of delivering anthelmintics (e.g. de-wormer) to the grouse that removed the parasite. Once the parasite was removed from the equation, the grouse populations remained stable and began to increase.
All this should not be construed to say that habitat, predators, and environmental factors do not matter. There is a tipping point for parasite levels, and if too high they can decrease survivability in wildlife. For example, in poor habitat, parasites can have a disproportionally greater impact on animal mortality than in good habitats because animals with higher parasite loads may be more susceptible to predation or less able to cope with environmental extremes such as severe winter weather or record-breaking drought.
What are we going to do about parasites?
Current research, funded by the Texas A&M AgriLife Extension Service and the Rolling Plains Quail Research Foundation, has two goals: 1) determine the effect of parasites on bobwhite behavior and health and 2) develop an effective field treatment for parasites. It may seem counterintuitive to look for a parasite treatment before there is hard evidence that parasites are indeed detrimental to quail populations. However, given the information gathered thus far, and the dire situation of quail populations, some researchers and concerned sportsmen alike feel the two situations need to be addressed concurrently.
The eyeworm parasite is a rather insidious organism. Due to a combination of its life cycle and biology, developing a cure is not going to be easy. Quail are thought to pick up the parasite by eating insects, which are the intermediate hosts carrying the eyeworm larvae. Once the insect is in the bird’s crop, the eyeworm exits and makes its way to the eye—this process may take as little as 15 minutes. Once it is established in the eye, the worm begins feeding on blood where it grows and develops into a mature worm that sheds eggs. These eggs are washed down the bird’s esophagus with tears and eventually eliminated with the bird’s feces, whereupon an insect (most likely roaches or grasshoppers) ingests the feces containing the eggs and the process begins all over again.
Domestic chickens that have eyeworms are treated by applying ivermectin or another similar anthelmintic directly into the eye with an eyedropper. The treatment is very effective, but can you imagine trying to first trap all the quail on a ranch and treat them only to have them go right out and re-infect themselves immediately by eating a grasshopper? Developing a medicated feed that could be distributed will be the most desirable way to deliver the treatment. These studies are currently underway at Dr. Kendall’s Wildlife Toxicology Lab at Texas Tech University. Other options for a treatment plan may include targeting the intermediate host or a different stage of the eyeworm life cycle. The research is in the early stages, but as it progresses we will update you.