Bovine Trichomoniasis in Wyoming
A 6-Year Review and an
Update for 2005
A look back at the period
since the Trichomonas control program began in Wyoming 2000 reveals some
encouraging results, but also raises some questions. The data presented here
based on results from diagnostic testing at the Wyoming State Veterinary
Laboratory. They do not include numbers from private clinics that perform
in-house analyses.
The table below provides
totals for comparison, and counties credited with highest numbers of bulls found
infected each year.
|
Year |
Animals tested |
Infected |
Worst county |
Infected |
Second worst
county |
Infected |
| |
|
Number |
Percent |
|
Number |
|
Number |
| 2000 |
4604 |
41 |
2.69% |
- |
- |
- |
- |
|
2001 |
6025 |
78 |
1.29% |
Fremont |
49 |
Carbon |
10 |
| 2002 |
5767 |
73 |
1.26% |
Fremont |
34 |
Sheridan |
19 |
|
2003 |
5610 |
46 |
0.82% |
Carbon |
20 |
Sublette |
7 |
| 2004 |
7287 |
72 |
0.99% |
Fremont |
33 |
Sheridan |
12 |
|
2005 |
6776 |
55 |
0.81% |
Fremont |
25 |
Sheridan |
22 |
The most encouraging data suggest that the
incidence of disease is decreasing, slowly but appreciably - the number of
positive tests have been below 1% for three years, whereas at the start of the
program in 2000 the number of positive tests was 2.69%. More questions than
answers have resulted from the smaller aspects of the program, however. Whereas
Fremont County has consistently had more infected bulls than any other, several
other counties produced some spontaneous spikes and dips in numbers of infected
animals. For example, in 2001 Sheridan County tested 1 positive among 201
bulls, whereas in 2002, 19 of 440 were found infected. In 2002, 1 of 863 bulls
in Carbon County was infected, compared to 20 out of 1055 in 2003.
Probably more surprising than any other
example was a record drop in positive bulls in Fremont county in 2003, when only
6 were infected of 1005 tested, compared with 34 of 1666 in 2002 and 33 of 1592
in 2004. Similar examples become visible almost every year, where some infected
bulls are identified in counties that appeared to be free of the disease in
previous years.
Trichomoniasis in WY for 2005 by country
A few questions:
-
What is the basis for year to year
variation in hitherto clean or nearly clean counties in appearance of
infected bulls?
-
Might some bull calves, produced by
chronically infected cows, themselves be chronically infected, and go on to
infect cows when they achieve sufficient age and development to be used for
breeding?
-
Are the rules pertaining to the
shipping and testing of breeding bulls being circumvented?
-
Are bulls that normally inhabit only
private land, and are therefore “immune” to testing requirements being
borrowed/loaned?
-
Is it be possible to eliminate the
causative agent from breeding bovids in Wyoming, under any system of
surveillance?
-
Might it be necessary or useful for
some of the control methods to be tweaked?
Incidentally, the numbers and variations
reviewed here are similar to those pertaining to the testing of out-of-state
bulls, mostly from neighboring states. The animals tested from neighboring
states ranges from 500 - 1500 annually. The percentage of positive animals
ranges from 0.15 - 2.65%. Often these are bulls that are checked prior to
shipping to Wyoming or other states that have trich-control regulations.
Answers to these questions are welcome.
April 8, 2006
Wyoming State Veterinary Laboratory
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