- A ProMED-mail post www.promedmail.org ProMED-mail, a
program of the International Society for Infectious Diseases www.isid.org
- Date: 7 Jul 2003 From: ProMED-mail <firstname.lastname@example.org>
Source: Wisconsin Dept of Natural Resources Official release [edited]
- Contacts: Wisconsin Department of Natural Resources
Tom Hauge (608) 266-2193
- Researchers continuing to examine the results of the
chronic wasting disease (CWD) sampling effort during the 2002 Wisconsin
hunting seasons report the data indicates older bucks have a higher prevalence
of the fatal brain disease and the disease is not uniformly distributed
within the infected area.
- "We examined the data from nearly 2000 adult deer
within the area where CWD is most prevalent. For yearling deer, we found
CWD at equal levels in male and female yearlings, 3.2 percent and 3.6 percent,
respectively," said Dr. Mike Samuel, lead CWD researcher with the
U.S. Geological Survey (USGS) Cooperative Wildlife Research Center, housed
at the University of Wisconsin. "But when the deer in our sample reach
3 years of age, males are showing double the prevalence -- 16.3 percent
in males compared to 8.1 percent in the females. This is similar to information
reported from Colorado earlier this year."
- As for distribution of the disease across the landscape,
testing of the deer removed from the intensive harvest zone last year show
a core area in Dane and Iowa counties where the disease was found in about
7 percent of the deer.
- "This kind of concentrated disease pattern is consistent
with our understanding about CWD and what we know about the home range
and social behavior of white-tailed deer," Dr. Samuel said. "It
is not surprising to find a disease concentration given the social nature
of deer. Studies have found female white-tailed deer often occupy about
a 1-square mile area during their entire life and tend to live near related
females. Once a disease gets started, the infection would tend to spread
outward somewhat similar to ripples on a pond."
- Tom Hauge, director of the DNR Bureau of Wildlife Management,
said the results suggest several possibilities about how the disease is
transmitted that, with further analysis, may help identify new ways to
manage the disease.
- "As DNR Secretary Hassett voiced before a national
review panel earlier this spring, we intend to 'learn and adapt' our CWD
control efforts as new information points the way", Hauge said. "The
identification of the high CWD concentration area will help us communicate
with the landowners and hunters in that area. Wisconsin will not be successful
in controlling this disease without their help."
- Dr. Samuel said that researches on the CWD Taskforce
had expected that the prevalence of the disease would increase with age
in both sexes because older animals have been exposed for a longer period
of time. The USGS Cooperative Wildlife Research Center is one of several
CWD Taskforce partners, which also includes the USGS National Wildlife
Health Center in Madison, sharing in new research on CWD.
- "What is interesting in these results is the increasing
prevalence of infection found in adult males compared to females, indicating
that males have a higher risk of infection than females," Dr. Samuel
- Hauge said the CWD Taskforce has several research efforts
underway or about to start up that look at the transmission question.
- "We have more to learn about what factors cause
the increased infection in males," Hauge said. "For instance,
if environmental transmission plays a role in spread of the disease, then
it follows that males, who have larger home ranges than females, would
logically experience more exposure. Another scenario that needs more investigation
is the potential of females transmitting CWD to males during the breeding
season. Once again, males cover a lot of ground during the breeding season
and contact many different females physically as well as through urine
scenting or other behaviors. A third possibility might be male-to-male
transmission in the bachelor groups that form in late winter to mid summer."
- While the data indicates that older bucks are more likely
to be infected than does, Hauge said, researchers do not think that killing
just all the older mature bucks would solve the problem.
- "CWD is also present in other, more common, segments
of the population. From a disease management viewpoint, the priority is
to reduce the overall population numbers and reduce the opportunity for
animals to animal contact. Landowners and hunters can really help control
this disease by maximizing the harvest of does on their lands in the infected
area," Hauge said.
- Researchers are also interested in learning more about
both female-to-female and male-female transmission. Samuel notes that female
deer form genetically-related matrilineal groups, and these groups tend
to exclude female deer from other matrilineal groups. Interaction between
related females within a social group is much more intense than between
individuals from unrelated groups.
- Multi-agency research studies involving the DNR, USGS,
and University of Wisconsin-Madison have already been initiated to better
understand how CWD might be transmitted within and among related groups
of females and among males and females during the breeding season.
- "We have a large and valuable database from last
year's surveillance effort thanks to the great cooperation of landowners
and hunters. We plan to use it to learn as much as we can about CWD,"
- -- ProMED-mail
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