Trichomoniasis of the Reproductive Tract

DATUS M. HAMMOND, PAUL R. FITZGERALD, AND J. LEGRANDE SHUPE.

ONE OF THE SERIOUS reproductive troubles in cattle, trichomoniasis, is transmitted by bulls. It causes temporary infertility in females and occasionally abortion. The disease is widespread.

Trichomoniasis is due to a microscopic, one-celled animal, Tritrichomonas (Trichomonas) foetus. It occurs in both dairy and beef cattle. In dairy herds, losses result from reduced milk production, reduced calf crop, interference with the breeding programs, and the necessity of treating or slaughtering infected bulls and some infected females. The losses are similar in beef herds except, of course, for those relating to milk production.

TRICHOMONADS, the causal organisms, occur in the sheath of bulls. Rarely are they in the deeper parts of the reproductive tract. Once a bull is infected he usually (but not always) retains the infection for the rest of his life.

The infected bull deposits the trichomonads in the vagina of the heifer or cow. Trichomonads usually multiply in the vagina until about 3 weeks after the service that initiated the infection.

Frequently a heifer returns to heat (oestrus) at about that time or within the following 10 days. After oestrus, trichomonads partly or completely disappear from the vagina. Several days before the next oestrus they are again present in larger numbers; after oestrus, another decrease in numbers or complete disappearance occurs. This pattern continues until the end of the infection, usually 3 to 4 months after its beginning.

Trichomonads enter the uterus from the vagina, perhaps before the fertilized egg enters it or soon thereafter.

Trichomonads in the uterus usually cause death of the fertilized egg or of the later stages in its development as embryo or fetus.

If pregnancy is interrupted in its earlier stages, the fertilized egg or embryo disintegrates and, except for a possible delay in oestrus, there is no indication that a pregnancy has occurred. If pregnancy is interrupted at a later stage, the dead fetus usually is discharged. That may not be noticed, however, because abortions caused by trichomoniasis usually occur relatively early in pregnancy. Occasionally in infected females pregnancies are not interrupted.

Sometimes the infection in the uterus persists longer than the usual 3 to 4 months. Pus frequently accumulates in the uterus in such cases, a condition called pyometra. The pus, which contains numerous trichomonads, may be discharged at intervals or may continue to accumulate in the uterus for several months. It is typical that the heifer or cow does not come in heat and appears to be pregnant. The occurrence of pyometra is associated with interruption of pregnancy without abortion and without regression (waning) of the corpus luteum. These cases usually require treatment by a veterinarian.

A heifer or cow that has recovered from an infection may be resistant to a second infection. If she is bred to an infected bull, she may not become infected or may develop only a slight infection that will not interfere with pregnancy. This resistance, however, varies considerably in degree and duration among different females. Reinfections are more likely to be associated with recognizable abortions, pyometras, and uninterrupted pregnancies than are the original infections.

Studies made by Department of Agriculture scientists at Beltsville and analyzed by David E. Bartlett showed that 70 percent of 29 original infections and 21 reinfections resulted in apparent early interruption of pregnancy, with little or no disturbance of the estrual cycle. Pyometra occurred in 10 percent of the cases, abortion in 4 percent, and normal pregnancies in 12 percent.

M. Vandeplassche and coworkers at the Veterinary Medical School at Ghent, Belgium, found, however, that trichomonads did not enter the uterus from the vagina until 25 or more days after service and that interruption of pregnancy usually occurred 2 months or more after service. Differences in strains of trichomonads may be a factor in such apparent differences in the course of infection.

SYMPTOMS include slight reddening and swelling of the vulva and walls of the vagina. The discharge from the vagina is somewhat greater in quantity and more watery than usual. Some degree of irregularity in heat periods may occur.

Some investigators have reported that infected bulls show inflammation of the penis and lining of the sheath, but others have stated that little or no inflammation occurs.

None of the symptoms in males or females is distinctive or consistent enough to have practical value in diagnosis.

TRANSMISSION is nearly always by breeding. Heifers and cows become infected by being bred to an infected bull. Bulls become infected by breeding infected females. Herds usually become infected by introduction into the herd of infected females or an infected bull or by intercourse between animals within the herd and infected animals outside of the herd.

Ninety to loo percent of heifers and cows that have not developed resistance to infection as a result of previous infection become infected when bred to an infected bull. Some bulls have a natural resistance to infection, but infected bulls usually do not develop resistance.

Heifers and cows sometimes become infected in ways other than by breeding, but there is no evidence to indicate that this is of any practical importance.

Species of trichomonads living in other domestic animals are able to multiply in the vagina or uterus of the cow if experimentally introduced into those organs. Such experiments have been done with trichomonads cultured from the nose, stomach, and cecum of pigs.

Presence of the trichomonads in some cases was associated with apparent failure of the heifer to settle or with interruption of pregnancy when the trichomonads were inoculated into the uterus of a pregnant heifer.

These findings indicate the importance of obtaining more information about the relations of T. foetus to other trichomonads of domestic animals.

ARTIFICIAL INSEMINATION may be a means of transmitting trichomoniasis. Trichomonads can survive at least as long as sperm at the temperatures and in the diluting agents used for storing semen. The antibiotics, such as penicillin and streptomycin, and sulfa drugs that are frequently added to the diluting agent have no apparent effect on the trichomonads at the concentrations used.

Infected bulls have been found in a relatively high proportion of artificial insemination centers examined. Dr. Bartlett and his coworkers at the University of Minnesota found that 23 of 168 bulls in 5 artificial insemination organizations were infected. Infected bulls also have been found in artificial insemination centers in several other States.

Observations of scientists at the University of Minnesota and the Utah State Agricultural College indicate that the rate of transmission of trichomoniasis by artificial insemination is low. The investigators at Ghent, however, found that the rate of transmission was not much lower in artificial insemination than in natural breeding.

The spread by artificial insemination probably occurs often enough to be a serious problem. In order to prevent such transmission, each bull used in an artificial insemination center should be examined at the time he is brought into the center and at intervals of 6 months or a year thereafter. When infected bulls are discovered, they should be eliminated from further use unless successfully treated.

DIAGNOSIS involves finding trichomonads in suspected animals. Trichomoniasis may be suspected in herds in which more than the normal number of services are required to settle heifers and cows. In addition, early abortions and cases of pyometra may occur but perhaps are not noticed. Trichomoniasis is more likely to be present if natural service is used than if artificial insemination is employed.

The breeding record of a herd suspected of having trichomoniasis should be examined carefully to determine which animals are most likely to give positive results. If one or more bulls have been used and are available, it is best to examine them first. It is usually easier to find trichomonads, if present, in bulls than in heifers and cows, because trichomonads are always present in the sheath of an infected bull.