Trichomoniasis in cattle herds increasing
Published on -3/15/2014, 12:07 PM
Trichomoniasis, or commonly referred to as trich, is a veneral disease of cattle caused by a single-celled protozoan parasite. Trich causes infertility, open cows and abortions in cows and heifers.
The protozoan organism lives in the microscopic folds of the skin that line the bull's penis and internal sheath. In the cow or heifer, the organism lives in the cavity of the vagina and uterus until her immune system eventually destroys it. That destruction process (immunity) might not occur for between three and 20 weeks. Also, the immunity is short-lived, so a cow or heifer can become infected again by an infected bull.
How is trich transmitted? Trich only can be spread during the breeding act, and can be carried by male or female. The disease can be spread from cow to cow by a bull. So it is nearly always a disease of cattle that are naturally bred, as opposed to artificially inseminated cattle. It very rarely can be transmitted by contaminated semen or AI equipment. Carrier bulls show no outward signs of infection. Older bulls more than 4 years of age are of most concern.
The cow, after having been infected at breeding, rarely might show a subtle, mild vaginal discharge one to three weeks later. This occurs in 5 to 15 percent of infected females. A fetal loss at 50 to 70 days of gestation is common among infected females, the fetus is small at this time, only about 1 inch in diameter, so you rarely will see the cleanings or aborted fetus. So there are no outward signs the bulls, cows, or heifers are infected.
What is the primary sign that your herd is infected with trich? It is a prolonged, drawn-out calving season, with a disappointing total calf crop or a high open rate at pregnancy check. The first year or two of infection in your herd might be very low, but in following years, it will increase to being more noticeable by fewer calves on the ground and more open females. The immunity lasts two to six months, and females will be susceptible to re-infection late during this breeding season or the next. Less than 1 percent of females can become chronic carriers.
Is there a treatment for trich? There is no legal treatment for either males or females; known infected bulls should be sold for slaughter only.
How can I tell if my herd has trich? In spite of the fact bulls don't show any signs, the organism is easier to find in bulls than in cows, because bulls become "carriers" while cows eventually shed the infection. Bulls need to be sexually rested for at least 14 days prior to testing. A PCR (polymerase chain reaction) test can be collected by a veterinarian and sent to a veterinarian diagnostic lab. The sample must arrive in the lab within 72 hours of collection. The test is looking for the trich DNA.
How does trich enter a herd? Several possible ways -- purchase of infected animals by buying non-virgin bulls that have not been tested for trich or open bred cows. It also can be spread if your cows come into contact with infected animals, such as the neighbor's bull in your pasture or your infected animals in a neighbor's pasture.
How do I prevent trich in my herd? Trich test every bull before each breeding season. This can be easily done when semen is checked or evaluated during a breeding soundness exam. Maintaining a young bull battery is advisable, and cull all open cows and heifers. Biosecurity is never perfect. Keeping your herd separate or isolated from others is best.
In 2013, the Kansas Veterinary Diagnostic Lab tested 6,900 samples for trich, which resulted in 0.7-percent positive, or 25 new herds became positive for trich in Kansas. This doesn't sound like much; however, in 2012, 17 new herds tested positive for trich, and in 2011, 14 new herds were tested positive. Bottom line: It is increasing throughout the state. The northwest to northcentral region of Kansas appears to be the epicenter of trich.
Stacy Campbell is agriculture Extension agent in Ellis County.