Improvements in Tritrichomonas foetus molecular testing

Time and temperature stability of Tritrichomonas foetus in phosphate-buffered saline as evaluated by a reverse transcription real-time PCR assay and field analysis

Tritrichomonas foetus (TF) is a significant reproductive pathogen of cattle, and sample collection, handling, transport, and testing are significant hurdles to surveillance programs. Recent methods have been developed that allow for the direct detection of TF using a reverse transcription real-time PCR (direct RT-qPCR) approach. To evaluate these methods, a comparative analysis was conducted to assess the technical performance of this assay with a commercially available real-time PCR (qPCR) assay. In addition, the evaluation of two types of collection media (PBS and TF transport tube) was conducted that evaluated sample stability from 0 to 3 days when stored at 4°C or 25°C. Extended incubation times for PBS media were also evaluated (5, 7, and 14 days) at both refrigeration and frozen temperatures to evaluate the effect of extended transport time on samples. Limits of detection (LODs), dynamic range, and RNA stability were assessed using lab-cultured TF spiked into samples of normal bovine smegma collected in PBS or TF transport media, and performance was assessed on field samples collected in parallel. 100% agreement was found between direct RT-qPCR and qPCR at 10 parasites/extraction and a LOD of 1 parasite/extraction. Differences in detection were not observed in either collection media when incubated at either temperatures for up to 3 days of incubation. In addition, the extended incubation experiments indicate that samples containing 10 parasites/extraction can be detected at 4°C for 5 days with a mean Cq 26.34 (95% CI: 23.11–29.58) and detected at −20°C for 7 or 14 days, with a mean Cq 29.55 (95% CI: 27.73–31.37). A significant decrease in detectable RNA was observed in samples containing <10 parasites/extraction at −20°C for 14 days, which should be considered for long-term storage. In summary, direct RT-qPCR was found to be equivalent or superior to qPCR and PBS was not significantly different from TF transport media. The findings of the current study allows for more flexibility during sample collection and transport and ultimately enhancement of TF surveillance programs.

Detection of Tritrichomonas foetus by RT-rtPCR in pooled bovine preputial washings

Trichomonosis is a venereal disease of cattle caused by the protozoan Tritrichomonas foetus. T. foetus infection in cattle herds can be economically costly for cattle producers; therefore, testing is important for detection of the agent. Given that bulls are considered to be subclinical carriers of T. foetus, it is important to detect T. foetus infection prior to movement and/or breeding season. We have described previously the development of an updated set of PCR primers and probes that offer increased sensitivity of T. foetus detection in preputial washings collected in PBS by utilizing reverse-transcription real-time PCR (RT-rtPCR) that targets the 5.8S ribosomal RNA of the T. foetus organism. Here, we report improvements in the updated RT-rtPCR reagents as well as the evaluation of testing of pooled preputial washings. We found that up to 5 preputial washings can be pooled, similar to routine testing practices (InPouch culture), without reducing the sensitivity of detection of T. foetus.

Molecular prevalence and phylogenetic confirmation of bovine trichomoniasis in aborted cows in Iraq

Background and Aim

Bovine trichomoniasis, caused by Tritrichomonas foetus, is a venereal disease that is distributed in many countries, including Iraq. Compared with other abortive infectious diseases, prevalence of T. foetus is expected to be relatively low in the field by veterinarians. This study aimed to estimate the prevalence of T. foetus in aborted cows by conventional polymerase chain reaction (PCR) and phylogenetic analysis of local T. foetus isolates was documented in the National Center for Biotechnology Information as the first sequenced isolates from Iraq.

Materials and Methods

Vaginal fluids were collected from 62 aborted cows and examined by PCR. Data were reported for the following parameters: Vital signs (body temperature and respiratory and pulse rates), age (<4, 4-8, and >8 years), reproductive health status (premature calving, embryonic death, pyometra, and healthy newborn), breed (pure or crossbred), type of breeding (natural or artificial), bull-to-cow ratio (1:<10, 1:10-20, and 1:>20), contact of cow with bull(s) from other farmers (yes or no), and contact with stray animals (dogs and cats).

Results

A total of 20.97% of aborted cows were positive for T. foetus. Phylogenetic analysis for 10 positive local T. foetus isolates demonstrated high identity with the Thai (MN560972.2) and Chinese (MH115435.1) isolates, with an identity range of 98.8%-99.5% and 98.6%-99.3%, respectively. Clinical data showed that the vital signs differed insignificantly between cows positive and negative for T. foetus. Prevalence and risk of infection increased significantly in <4-year-old, early calving, embryonic death, crossbred, and naturally inseminated cows that had direct contact with bulls from other farmers, and contact with stray animals. Fetal pneumonia and death of premature calves were significant among positive aborted fetuses.

Conclusion

Tritrichomonas foetus is highly prevalent in aborted cows in Iraq and phylogenetic analysis demonstrated an identity between the local and global isolates, that is, Thai and Chinese, of cats.

Molecular detection of Tritrichomonas foetus in bovine samples: a novel real-time polymerase chain reaction (PCR) assay targeting EF1-alpha-Tf1 and a comparative study of published PCR techniques

The parasite T. foetus causes trichomonosis in cattle but is generally asymptomatic in males. Thus, many bulls carrying the disease go unnoticed, making the detection of T. foetus in bulls an important aspect for its control. Due to drawbacks posed by its cultivation, PCR is a preferred option for diagnostic laboratories. Most published PCR protocols target the genomic region compring the 18S, 5.8S, and 28S rRNA genes and internal transcribed spacers 1 and 2 (rRNA-ITS region), homologous to that of other Tritrichomonas species. There is minimal information on alternative genetic targets and no comparative studies have been published. We compared a protocol based on the microsatellite TfRE (called H94) and five protocols based on the rRNA-ITS region (called M06, M15, G02, G05, and N02). We also designed and evaluated a novel PCR-based assay on the EF1-alpha-Tf1 gene (called V21). The analytical sensitivity and specificity assays for the PCR protocols were performed according to the World Organisation for Animal Health (OIE) directives and the comparative study was performed with a widely used PCR (M06) on clinical samples from 466 breeding bulls. V21 showed a high degree of agreement with our reference M06 (kappa = 0.967), as well as M15 (kappa = 0.958), G05 (kappa = 0.948), and H94 (kappa = 0.986). Protocols H94 and V21 appear to be good approaches for confirming clinical cases in preputial bull samples when genomic regions alternative to rRNA-ITS are required. By contrast, N02 gave false negatives and G02 false positives.

Investigation of Tritrichomonas foetus in cryopreserved bovine semen by culture and polymerase chain reaction

ABSTRACT Bovine Trichomoniasis (BT) is an infectious disease caused by Tritrichomonas foetus that can be transmitted either sexually or by fomites. In males, the disease is asymptomatic and permanent. T. foetus has been detected in semen samples where it is able to remain viable even when frozen. The objective of this study was to investigate the presence of T. foetus in 27 samples of commercial frozen bovine semen by culture and Polymerase Chain Reaction (PCR). Samples were thawed in water at 37°C. Part of the samples was inoculated in a test tube containing Diamond’s medium and incubated at 35°C. Growth was evaluated every 24 hours via direct examination under a microscope. The other part was placed in an Eppendorf tube and frozen for later molecular analysis. After 10 days of culture, all samples were negative for T. foetus. The Quick-DNA Miniprep Kit (Zymo Research) without proteinase K was used for DNA extraction. The primers used in PCR were TRF3 and TRF4. PCR results were negative for all samples. In conclusion, bovine semen samples were negative for T. foetus in both diagnostic methods, according to the adopted methodology.