The influence of temperature and simulated transport conditions of diagnostic samples on real-time polymerase chain reaction for the detection of Tritrichomonas foetus DNA

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.

Improvements in Tritrichomonas foetus molecular testing

Bovine trichomoniasis is a sexually transmitted disease that results in infertility, abortion, and calf age variability. To date, management strategies include testing for Tritrichomonas foetus and culling of infected males. Challenges associated with testing include cost of culture medium, time and labor burden of sample incubation and processing, and adverse effects of bacterial growth on detection sensitivity. To overcome these challenges, we developed a direct reverse-transcription quantitative real-time PCR (direct RT-qPCR) utilizing smegma, eliminating the use of culture medium. In an analysis of 166 field samples (56 positives and 110 negatives as determined using microscopic reading of cultures as the reference test), the direct RT-qPCR exhibited 100% diagnostic sensitivity and 100% specificity, whereas the currently employed qPCR (culture qPCR), which utilizes cultured samples, exhibited 95% diagnostic sensitivity and 100% specificity. Agreement between direct RT-qPCR and culture qPCR was 98%. Moreover, direct RT-qPCR identified 3 more positive samples and exhibited lower quantification cycle (Cq) values among positives by culture reading than did culture qPCR (direct RT-qPCR Cq range = 14.6-32.3 vs. culture qPCR Cq range = 18.7-37.4). The direct RT-qPCR enables simplified sample collection, elimination of culture medium, faster results, applicability in cows, and lower cost than culture qPCR.

Prevalence of Tritrichomonas foetus in tennessee bulls

The prevalence of bovine trichomonosis (BT) in TN bulls was estimated through both active screening of bulls and review of previous laboratory records. During the active bull screening, preputial smegma specimens were collected from 458 TN beef bulls at 2 cattle slaughterhouses and 2 stockyards, which serve most beef bulls in TN, between March 2014 and June 2015. Each specimen was cultured for Tritrichomonas foetus (T. foetus) as well as evaluated microscopically every other day for seven days for any protozoa resembling T. foetus. An aliquot of the culture media from each specimen was used for DNA extraction and subsequent qPCR testing. Two specimens were considered suspect on microscopic evaluation, but all specimens were negative for T. foetus on qPCR. This suggests that the 2 specimens were most likely contaminated by fecal trichomonads. Retrospectively, 1979 T. foetus test records from 2 major TN diagnostic laboratories were reviewed between October 2013 and September 2016. True prevalence of BT in TN beef bulls was estimated at <0.01% from the laboratory records, although the county prevalence differed in 2 TN counties (Marshal: 0.09% and Bedford: 0.5%). Overall, the prevalence of BT in TN is low, and the current screening efforts to help control BT disease in TN are acceptable. Future efforts should focus on educating cattle stakeholders on the importance of optimal specimen collection and handling as well as routine testing for BT before cattle movement. In addition, cattle producers should be reminded of leading risk factors associated with BT in cattle.

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.

Sensitivity of a real-time polymerase chain reaction for Tritrichomonas fetus in direct individual and pooled preputial samples

The objective of this study was to evaluate the sensitivity of a commercially available real-time polymerase chain reaction (PCR) test for the detection of Tritrichomonas fetus in individual and pooled direct preputial samples. Two samples were collected and processed once a week from nine T. fetus-infected bulls (n = 121) and placed into either an InPouch TF or 2 mL of PBS. Preputial samples were also collected into both media and PBS from 1016 other bulls. All pouches were cultured and evaluated as per manufacturer's instructions. The prepuce samples collected directly into PBS were individually evaluated using real-time PCR by a commercial diagnostic laboratory. Direct preputial samples were then randomly divided for pooling into groups of 5 and 10 samples, ensuring that every pool had one sample from a known infected bull before testing using real-time PCR. Sensitivity was estimated for culture and real-time PCR of the 121 direct and culture-enriched individual samples from nine infected bulls. There were no differences (P = 0.12) among the sensitivity estimates for culture, 95.0% (95% confidence interval [CI]: 89.6%-97.7%); real-time PCR of culture-enriched samples, 95.9% (95% CI: 90.7-98.2); and direct preputial samples, 90.1% (95% CI: 83.5-94.2). There was also no significant difference (P = 0.08) between the sensitivity of real-time PCR for direct preputial samples in 110 pools of 5 (83.6%, 95% CI: 75.6-89.4) or 10 samples (77.3%, 95% CI: 68.6-84.1). The use of three sequential direct samples, collected in PBS at weekly intervals and tested by real-time PCR, increased the sensitivity to 100% for pools of 5 and 96% for pools of 10. In conclusion, direct preputial samples collected in PBS and tested by real-time PCR individually have comparable sensitivity to culture and real-time PCR in enriched samples. The use of pooled direct preputial samples appears to be relatively sensitive. However, this strategy requires repeated sampling to optimize sensitivity. Real-time PCR testing of preputial samples collected directly into PBS with the option of pooling would decrease the cost associated with screening bulls, and increase the feasibility of large epidemiological studies and active surveillance.

Molecular determination of Tritrichomonas spp. in aborted bovine foetuses in Eastern Anatolian Region of Turkey

Tritrichomonas foetus is the causative agent of venereal trichomonosis in cattle causing infertility, pyometra and abortions. The objectives of this study were to determine the positivity rate of Tritrichomonas spp. in abomasal content of aborted foetuses from Eastern Anatolian Region of Turkey, using staining, culture and PCR methods and to present the isolates found in the region. A total of 246 abomasal content of aborted foetuses were tested and 14 of 246 (5.7%) were Tritrichomonas spp. positive only by polymerase chain reaction (PCR). Positivity was not attained by staining or culture method. Four of the positive samples in PCR were confirmed to be T. foetus by sequencing of the amplified 5.8S rRNA gene and flanking ITS regions. Nucleotide sequences of TR-Erzurum T. foetus isolates have been entered into the GenBank sequence database under accession numbers KC236423 through KC236426. This preliminary study suggests that future studies are needed on the systematic relationships and epidemiology of T. foetus isolates in the region.