IntroductionTrichomonads are a common parasite of many vertebrate and invertebrate species. Recent evidence points to a potential zoonosis aspect to infection but mostly it is transmited within a host species from one individual to anotherd (Maritz et al., 2014). In humans, the CDC describes how this is the most common form of venereal disease but produce few symptoms in humans although there can be some impact on the new born fetus whose mother was infected.
Potential transmission routes of Trichomades. The boxes represent specific speices of trichomades identified. Solid lines represent known transmission and dashed lines represent theoretical transmission. Original figure legend From Maritz et al., 2014. Cattle Trichomoniasis is a venereal disease of cattle which causes devastating economic losses in infected herds because of reduced calving rates or increased length of calving season. Trichomoniasis has been recognized in all major cattle-producing countries during the past 100 years. Because most infected animals do not show any symptoms, the first sign of trouble may be a lower than normal calving rate in herds using natural breeding. In 1990, a random survey of California beef herds showed that more than 15% of the herds had at least one infected bull. The organism that causes Trichomoniasis in cattle is related to the protozoa Trichomonas vaginalis that causes a similar venereal disease in humans. The incidence of Trichomoniasis in humans is quite high with over 7.4 million new cases each year. Another similiar organism also causes Trichomoniasis in birds but this infection is primarily a skin and lung infection. The evidence shown above in the figure and reviewed by Maritz et al., 2014 is very suggestive of a much more widespread zoonotic infection rate potential for disease outcomes than previously realized. The protozoa Tritrichomonas foetus,which causes Trichomoniasis in cattle, is a motile protozoan with a pyriform body, three anterior flagella, one posterior flagellum and an undulating membrane along the body. (It is one third larger than the head of a bovine sperm). It is transmitted by sexual contact between animals. The most common scenario for herd infection is the introduction of a mature bull into a herd that is either infected or quickly becomes infected after breeding an infected cow and passes the organism on to other cows in the herd. The bull is the most important link in this disease since he is most likely to become chronically infected. T. foetus lives in the microscopic folds of the skin that lines the bull’s penis and sheath (prepucial crypts) but does not cause any symptoms. As a bulls matures, the number of folds increases which increases the area to support the disease organisms and increases the likelihood of chronic infection. Young bulls (less than 4 years) have poor development of prepucial crypts and are less likely to harbor T. foetus. Once a bull has become infected, treatment is usually not effective or practical. T. foetus can be found in the vagina, cervix and uterus of an infected cow causing vulvovaginites, cervicitis, endometritis or pyometra. However, the symptoms are usually so mild that they are undetected. The infection lasts until the immune system destroys the protozoa, which may take 3-20 weeks. An infected cow usually reabsorbs or aborts the fetus at 40-60 days. The acquired immunity is of short duration but may allow the cow to become pregnant from a subsequent breeding, leading to a longer calving season. T. foetus does not effect fertilization but causes either early embryonic death or interferes with the uterus environment so that it cannot support fetal development. Suspected infected cows should be isolated from the herd until testing can be done. Sexual rest will allow the cow to overcome the infection although this may be economically unfeasible. Diagnosis The definitive diagnosis of Trichomoniasis depends on a positive culture from the prepucial smegma of the bull or cervical mucous of the cow. The most effective way of testing a herd is to test all breeding bulls once after 1-2 weeks of sexual rest (80-90% chance of finding the disease if it is present). Repeat testing for 3 consecutive weeks is the preferred method giving a 99% confidence in diagnosis. Treatment and Control Since this disease is difficult to detect and treat, control by using sound management is the key to prevention. There is a vaccine available but it is not a cure, only decreases shedding of the protozoa in females until the disease clears on its own. The vaccine has not been shown efficacious for bulls. Management practices such as use of artificial insemination, purchasing virgin bull and heifer replacements and testing of all mature animals introduced into the herd is critical. Bulls should be replaced after they reach 4 years of age and a pre-breeding season testing program of herd bulls implemented. Most importantly, observation of excessive repeat breeding or uterine infections at the time of pregnancy detection must be investigated. California Agricultural Technology Institute, 1994;Trichomoniasis Colorado Department of Ag Publication, Trichomoniasis University of Florida Extension - Trichomoniasis Centers for Disease Control and Prevention, STD, Trichomoniasis |
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