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The protozoan, Tritrichomonas foetus (TF), has been recognized as a cause of bovine infertility for more than 100 years (Skirrow and BonDurant, 1988). As an obligate parasite of the bovine reproductive tract its control and eradication seems achievable (Harding, 1950). However, this disease continues to trouble US cattle producers and a recent epidemic in the Western US has lead to increased interest in research and regulatory efforts (Cima, 2009).
Outbreak investigations were carried out on three Nebraska ranches to assess the efficiency of currently available diagnostic tests, culture, gel polymerase chain reaction (PCR), and real time PCR (rtPCR), in identifying TF infected bulls in known TF infected herds with the following objectives:
(1) to compare the agreement of the three assays for classifying the status of individual preputial specimens.
(2) to compare the agreement of the three assays in identifying TF infected bulls based on three sequential samples.
(3) to correlate cow herd pregnancy percentages with TF herd bull prevalence.
Comparisons of diagnostic tests were conducted using Cohen’s Kappa statistic and McNemar’s paired sample Chi square test p values. Simple linear regression was used to assess the relationship between non-pregnancy percentages and prevalence of TF positive bulls.
No significant differences between culture and gel PCR for individual specimen and bull TF classification were found. Real time PCR had a high rate of apparent false positives relative to culture and gel PCR for individual specimen and bull TF classification. However, all assays required multiple, sequential specimens to adequately identify all TF infected bulls in the study herds. Cow non-pregnancy rates correlated linearly with TF positive bull prevalence.
These studies indicate similar diagnostic assay performance for culture, gel PCR, and real time PCR which suggests opportunities for improved TF control may be found by focusing on pre-analytical aspects of diagnostic TF detection such as consistent bull identification, optimization of specimen collection techniques, and pre-incubation specimen handling factors.
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