The eyeworm parasite found in quail (Oxyspirura petrowi) has been all over the print media lately.
Although it is the most publicized, it is not the only type of potentially
harmful parasite found in quail. Currently, there are a number of different
research projects ongoing at the Caesar Kleberg Wildlife Research Institute
(CKWRI) at Texas A&M University-Kingsville and the Wildlife Toxicology
Laboratory at The Institute of Human and Environmental Health (TIEHH) at Texas
Tech University concerning all types of parasites in both bobwhite and scaled
quail. Based on the preliminary findings from these studies concern is growing
in the quail community about the role parasites may be playing in quail
decline. That is why Texas A&M AgriLife Extension Service funded a Texas
Tech University project in the Wildlife Toxicology Laboratory through the Texas
Quail Decline Initiative. This project is investigating the feasibility of
using anthelmintics to treat parasites in bobwhite quail.
History of O. petrowi in Bobwhites (in a nutshell)
Given the recent attention, it may seem like quail eyeworms
are new to science, but actually they are not.
Eyeworms infect many other species of gallinaceous birds (e.g. pheasants
and prairie chickens) and they are found in domestic chickens as well (granted
it is a different species in chickens: Oxyspirura
mansoni, but there are many similarities).
O. petrowi species of eyeworms
were first described by a Russian scientist in 1929. Later in the 1960s, A.S. Jackson the
well-known TPWD biologist identified the parasite in a small sample of bobwhite
quail harvested from Cottle County, Texas. Since then few questions have been answered on
eyeworms in wild bobwhite; it is a “glaring intellectual void [that] extends
well beyond the borders of Texas.”3
A 2007 small scale project on the Rolling Plains Quail
Research Ranch and a nearby ranch in Fisher County documented that eyeworms
were indeed still present in bobwhite quail4. In fact, 57% of the
quail collected for that study were infected with eyeworms; this intriguing
result obviously warranted further investigation and so further parasite
research was included as part of a much larger disease study, “Operation
Idiopathic Decline” (OID), funded by the Rolling Plains Quail Research
Foundation. Quail collected from all
across the Rolling Plains in Texas and Oklahoma during 2011, 2012, and 2013
were found to be infected with parasites.
Then the questions became: 1) should we care and 2) what do we do about
it? Current research is in the “what do
we do about it” phase, including the project funded by Texas A&M AgriLife
Extension Service.
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| Eyeworm found in dead bobwhite quail in Roberts County. |
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.
In Summary
After decades of quail research, we are truly in uncharted
territory when it comes to disease research and we are on the tip of the
proverbial iceberg. There is a world of data left to gather and interpret but
the potential for turning around the quail decline as a result of it is very
real. This is an exciting time to be
involved in quail research!
If you want to learn more about the current status of Dr. Kendall's research, join us this Friday, January 16th at the Dallas Convention Center. For more information, follow this link: http://today.agrilife.org/2014/12/10/distinguished-lectureship-in-quail-management-set-jan-16-in-dallas/