Trichomoniasis and other STDs in beef cattle (Proceedings)

Trichomoniasis is a sexually transmitted reproductive disease of cattle caused by Tritrichomonas foetus (formally named Trichomonas foetus). There has been a re-emergence of the disease due to increased movement of breeding cattle across the country. The disease is characterized by infertility and early embryonic death. However, most producers do not recognize a problem until cattle are checked for pregnancy. Affected herds may see 40-60% late and open cows. Bulls are asymptomatic carriers of the protozoa that infect the cow during breeding. Infected cows will experience fetal loss and then clear the infection and be able to sustain a pregnancy.

The T. foetus protozoa can live in the cow's reproductive track and the surface of bull's penis. In bulls the protozoa will embed into penile crypts and most infected bulls will become permanent carriers. The bull spreads the disease by mechanical vector during breeding. There are not any treatments for this disease and carrier bulls should be culled for slaughter. There have been some reported instances when young bulls were able to clear the infection. However, as a bull ages the penile crypts become deeper allowing the protozoa to permanently establish itself. Up to 90% of cows will become infected when bred by a carrier bull. Cows will eventually develop a temporary immunity to the organism and maintain a pregnancy. If there is an extended breeding season these cows will be late bred. However, with shorter breeding seasons the cow will not have time to develop immunity and will not be pregnant.

The progression of the disease within a herd is variable depending upon source of the infection and duration of breeding season. Often times the disease is not diagnosed the first year it infects the herd. If an infected open female is added to the herd there would be very little change in reproductive performance. A small percentage of cows may have been infected and became late bred animals. However, one or more bulls likely became infected carriers and will infect all the cows they breed the next year. Subsequently, more bulls will become infected that breeding season. In the third year multiple bulls will be infected and up to half the cows will be open or late bred. If the disease is allowed to persist in the herd pregnancy rates will recover in subsequent years but reproductive performance will never be optimal. Some practitioners report an increased incidence of pyometras in beef cows.

Currently many Western states have experienced increased problems with Trichomoniasis. These states have herds with active infections of T. foetus that are under quarantine. Additionally, all states west of Iowa except for Kansas have some import restrictions for bringing bulls into their states. For most of these states any bull over 24 months of age or any non-virgin bull needs to have a negative T. foetus PCR test within 30 days. However, some states have some more restrictive requirements. Oregon and Arizona require all bulls over 12 months of age to be tested, Utah tests any bull over 9 months and Nevada over 8 months. Colorado has a draft rule that would require bulls over 12 months of age to be tested.

Testing can either be by direct examination of a Pouch test or PCR test. Many states are requiring the PCR test for importation of breeding animals. For bulls the surface of the glans penis is vigorously scraped with a rigid insemination pipette while applying negative pressure with syringe. Bulls need to be sexually rested at least 2 weeks before sampling. After collection the sample should be inoculated into an InPouch TF Pouch with a specific media for T. foetus. The pouch is available from Bio-Med Diagnostics or most veterinary diagnostic laboratories. Do not refrigerate the pouch after inoculation. The pouch can then be incubated for up to 6 days with daily observation under a microscope at 10x. If fecal contamination of the sample occurs T. intestinalis could cause a false positive in the visual interpretation of the the InPouch test. A PCR test can also be run on the sample in an InPouch test for more rapid results. For cows cervical mucus or uterine secretions can be obtained with a pipette positioned in the cervix or vaginal floor.

The PCR test is very sensitive and specific for T. foetus. However, sample collection technique hampers true sensitivity of the diagnostic test. Therefore, for states with a quarantine program bulls most test negative 3 times (2 weeks between tests) to be declared negative. Most bull studs require 6 negative tests before they will collect semen.

Figure 1. Prepucial scraping for T. foetous BonDurant, R.H

Preventing introduction of T. foetous into a herd is the best method to control the disease. Only virgin bulls should be purchased for use in the herd. If virgin bulls are not available bulls should be tested 3 times prior to introducing into the herd. For females virgin or pregnant heifers from reputable sources is recommended. Open cows should not be introduced into the herd. Occasionally (1%) of cows will become infected carriers and still be able to maintain a pregnancy. Producers should maintain adequate fences to prevent neighboring bulls from intermingling with the herd. Avoid communal grazing if possible or require bulls to tested.

If a herd becomes infected the producer will need to initiate an active testing and culling program. All bulls should be tested at least 3 times and positive bulls culled to slaughter. Many states require positive bulls to be identified as slaughter only. Replace bulls with virgin bulls or implement an AI program. Cows should be pregnancy checked and all open and late-bred cows culled, they may be carriers. Implement a 60 day breeding season to decrease potential for transmission of the disease. A vaccine is available for T. foetus. However, vaccination will not clear a herd. Vaccination may limit the duration of the infection in a cow but will not alter the spread within a herd.