Trichomoniasis Continues to Concern South Dakota Farmers and Ranchers

 

Russ Daly, DVM

Extension Veterinarian, South Dakota State University

 

In 2004, South Dakota producers got re-acquainted with Trichomoniasis (or “Trich”).  During 2005, 45 South Dakota herds were found positive for Trich.  Of these, 35 were in the 4 southwestern-most counties of Pennington, Custer, Fall River, and Shannon, but the infection had been diagnosed as far east as Gregory County.  Nine cases were reported in 2006, and 10 in 2007.

 

Trichomoniasis is a venereal disease of cattle caused by a protozoal organism, Tritrichomonas foetus.  The organism is found in the genital tracts of infected cows, and on the penis and in the sheath of the bull (not generally the semen itself).  The disease is spread from bull to bull by breeding an infected cow.  Once infected, bulls--especially older bulls--tend to become chronic carriers.  Cows tend to clear the protozoa from their system within 3 to 4 months post-infection, but immunity is not long-lasting and cows can become re-infected later. 

 

Clinical Signs:

Trichomoniasis causes pregnancy loss in infected cows.  This can show up on pasture in several ways:

  1. Regular returns to heat 21-days post-breeding.  The cow conceives and the embryo dies off within the first 18 days post-breeding.
  2. Irregular and late returns to heat.  This is more common.  The cow conceives and after 50-100 days the embryo dies off and is aborted.  The cow may then cycle normally and breed back if bulls are still present.  Short-term immunity to Trich may result, so these (now late) calves may be then carried to term.
  3. Abortions.  Uncommonly seen, as most calves are aborted in early pregnancy: range conditions usually preclude observation of these.  Later term abortions are possible, but relatively rare.
  4. Tired bulls, due to increased numbers of cows returning to heat.  Trich does not produce any visible clinical signs or lesions in affected bulls or cows.

 

Characteristics of Trich at preg-checking time:

  1. Increased numbers of open cows.  Reports of 50% open cows at preg-check are not unusual.
  2. Increased numbers of late calvers.
  3. Pyometras.  Pus building up in the uterus due to the fetus dying without being expelled.  Relatively uncommon.

 

Diagnosis:

Diagnosis of Trich is confirmed by either: 1) a PCR (polymerase chain reaction) test on a single scraping of the bull’s sheath or penis, or 2) culture of the scraping of the bull’s sheath or penis.  Sensitivity (the chance of the test reading positive in a positive bull) of the PCR test is quite high (98% has been reported), but is very dependent on testing a good quality sample (proper collection technique is crucial).  Sensitivity of cultures is reported to be over 99% when three weekly tests are performed on the same animal. Diagnosis of Trich in cows can be done by taking samples of vaginal mucus for culture.  At least one of the state’s infected herds was diagnosed in the cows first.  In the instances when abortion occurs, the organisms can be found in the fetus in high numbers.

 

Prevention and Control of Trichomoniasis:

There is no effective treatment for Trichomoniasis.  A vaccine is available for use in cows pre-breeding, but it does not clear animals from being carriers.  It should only be considered in those situations where management changes are impossible.   Management practices are by far the most important means of dealing with this disease.

 

Obviously, preventing Trich from entering your herd is of utmost value.  New regulations placed into effect by the South Dakota Animal Industry Board on June 1, 2005, and amended recently (Nov. 2007) underscore the importance of limiting the spread of the disease.  The regulations stipulate:

  • For non-virgin bulls imported into South Dakota, or sold, loaned, or leased within the state, one negative PCR or three weekly negative Trich cultures must be performed prior to movement.
  • Non-pregnant female cows that have had at least one calf must not be sold for breeding purposes.  They can only be sold for feeding or slaughter.

 

The new regulations are extensive, but necessary to protect the reproductive and economic health of the state’s cattle herds.  Other organizations, such as tribal entities, may have their own regulations before bulls can be turned out on grazing lands.

 

Control measures for those herds that are infected include:

·         Cull herd bulls and replace them with virgin bulls each year.

·         Cull all open cows and cows that lose calves during calving.  Only cows with their own calves at side should go to pasture.

·         Consider AI.

 

Additional control measures that all producers should implement:

·         Observe breeding activity on pasture.

·         Keep good records of which bulls and which cows are in which pasture.

·         Avoid communal grazing situations.

·         Maintain fences so that neighboring bulls or cows cannot enter your pasture.

·         Perform pregnancy checking in a timely manner after breeding season.

 

Trichomoniasis has been an economic blow to the herds it has affected, and it appears that it will be around for some time to come.  All of us are responsible for meeting this problem head-on so that the future effects of the disease will be as minimal as possible. 

 

Russ Daly, DVM

Extension Veterinarian

Assistant Professor

Veterinary Science Department

South Dakota State University

Box 2175

Brookings, SD  57007

Phone: 605-688-6589

Fax:  605-688-6003