Spread of Tritrichomonas foetus in beef bulls in an infected herd

Not gone but forgotten: Tritrichomonas foetus in extensively-managed bulls from Australia's Northern Territory

Bovine trichomonosis, caused by infection with the protozoan parasite Tritrichomonas foetus, is globally recognised as a cause of reproductive failure in cattle. Maintained in clinically normal bulls, T. foetus infection results in infertility and abortion in infected cows. In Australia’s Northern Territory (NT), logistical limitations associated with extensive livestock production inhibit wide-scale testing and diagnosis, allowing the parasite to persist undetected. In the present study, T. foetus was detected in 18/109 preputial cultures collected from bulls on a property in the NT with a history of low birth rates and reproductive failure using real-time PCR testing. Of the T. foetus-positive samples, 13/18 were genotyped using the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S rDNA unit. Selected samples were further characterised using the protein-coding genes of cysteine proteases (CP-1, 2, 4–9) and cytosolic malate dehydrogenase 1 (MDH-1) to determine if the isolates were ‘bovineʼ, ‘felineʼ or ‘Southern Africaʼ genotypes. All samples were 100% identical to the T. foetus ‘bovine’ genotype across all markers. This is the first reported case of trichomonosis in Australian cattle since 1988 and is a reminder that T. foetus should be considered whenever reproductive failure occurs in extensive cattle systems.

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The first published case of bovine trichomonosis in Australia since 1988.

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Extensive genotyping of two isolates using 10 divergent markers.

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Isolates were determined to be 100% homologous with the Tritrichomonas foetus ‘bovine’ genotype.

Review of Diagnostic Procedures and Approaches to Infectious Causes of Reproductive Failures of Cattle in Australia and New Zealand

Infectious causes of reproductive failure in cattle are important in Australia and New Zealand, where strict biosecurity protocols are in place to prevent the introduction and spread of new diseases. Neospora caninum ranks highly as an important cause of reproductive wastage along with fungal and bacterial infections. Brucella, a leading cause of abortion elsewhere in the world, is foreign, following successful programs to control and eradicate the disease. Leptospirosis in cattle is largely controlled by vaccination, while Campylobacter and Tritrichomonas infections occur at low rates. In both countries, Bovine Viral Diarrhea virus (BVDV) infection rates as the second most economically important disease of cattle and one that also has an effect on reproduction. Effective disease control strategies require rapid diagnoses at diagnostic laboratories. To facilitate this process, this review will discuss the infectious causes of reproductive losses present in both countries, their clinical presentation and an effective pathway to a diagnosis.

Tritrichomonas foetus Prevention and Control in Cattle

Bovine trichomoniasis has been recognized as a pathogen of the bovine reproductive tract for nearly 100 years. Although characteristics of the causative organism, Tritrichomonas foetus lend to control and there are examples of disease eradication, cattle producers are still faced with this disease. This article highlights the clinical presentation, magnitude of effect, risk factors, epidemiology, and sample collection and suggests applications in developing herd-level control measures for beef cattle producers including testing strategies for control, testing strategies for surveillance, strategies to eliminate trichomoniasis from infected herds, and strategies for prevention in uninfected herds.

Selected diseases and conditions associated with bovine conceptus loss in the first trimester

The outcomes of insults to the bovine conceptus depend on the predilection of the insulting agent for the gravid reproductive tract, the virulence of the insult, and the developmental maturity/immune competence of the conceptus at the time of the insult. Agents that are lethal at one time during gestation may be harmless at another, or may have completely different effects (some not so harmless) at different gestational ages. This review discusses some of the known physical-mechanical, physiological, and infectious causes of first trimester bovine conceptus losses, including three infectious agents that have been the subject of recent studies for their potential to transmit disease via embryo transfer.

Tritrichomonas foetus

Tritrichomonas foetus is a venereal disease of cattle that has a clear pattern of adverse reproductive sequela in the affected female, with a carrier state in the bull in which he shows no outward signs. Given sexual rest and symptomatic treatment, the female returns to reproductive viability. In contrast, the male remains infective and is a risk to other female contacts. Prevention of the disease relies on excluding infected males and females from the population of susceptible cattle. Control of this disease requires a plan to identify, isolate, and treat infected females, and eliminate or cull infected males. Improvements in culture technique and the application of newer methods, such as polymerase chain reaction, enhance the likelihood of detecting infected animals.

Development of a simulation model to evaluate the effect of vaccination against Tritrichomonas foetus on reproductive efficiency in beef herds

OBJECTIVE

To develop a model to evaluate the effect of vaccination against Tritrichomonas foetus on reproductive efficiency in beef herds.

SAMPLE POPULATION

A beef herd of 300 cows and 12 bulls (8 bulls < or = 3 years old and 4 bulls > 3 years old).

PROCEDURE

The model was developed by use of data for various risk factors and vaccine efficacy. The reference herd was considered to be one in which T. foetus had been diagnosed and bulls were tested for T. foetus before the breeding season. Five thousand iterations were run for each of 13 simulations, with each simulation representing a separate combination of risk factors.

RESULTS

In all simulations, vaccination resulted in significantly higher calving incidence than nonvaccination. Shared grazing was found to be the most significant risk factor for a decrease in calving incidence attributable to T. foetus infection, followed in importance by lack of testing before the breeding season and a higher proportion of old bulls. Combinations of risk factors contributed to a loss of income of up to 22%, some of which could be blunted by vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE

Highest calving incidence is achieved when all bulls are tested for T. foetus before the breeding season and all bulls with positive culture results are culled. Avoiding all risk factors is better than vaccinating, but when this is not feasible for a given herd, the results of this simulation indicate that proper vaccination can decrease economic losses attributable to abortions caused by T. foetus.

Prevalence of bovine venereal disease in the Victoria River District of the Northern Territory: likely economic effects and practicable control measures

Area prevalences of bovine Campylobacteriosis and Trichomoniasis in the Victoria River District (VRD) of the Northern Territory were determined by a survey of bulls. Eighty-seven percent of herds were infected with Campylobacteriosis and 65.6 percent were infected with Trichomoniasis. The levels of infection recorded are likely to be causing significant reductions in reproductive rates. Control of Campylobacteriosis is unlikely to be practicable on a district basis, but in some herds it may be possible to implement control measures in select groups subject to good stock control. Trichomoniasis control measures are generally not implementable in the VRD management situation. Computer modelling suggests that control measures are unlikely to be profitable in commercial herds. There is a need for field investigations to confirm this.

Immunisation of bulls against trichomoniasis

Studies into the immunisation of bulls against infection with Tritrichomonas foetus showed that subcutaneous administration of vaccines containing killed cells of T foetus in a mineral oil adjuvant prevented the eliminated genital infection in most bulls up to the age of 5 years. Immunisation did not effectively prevent or cure infection in bulls older than 5.5 years.