Detection of bovine trichomoniasis with a specific DNA probe and PCR amplification system

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.

What is known about Tritrichomonas foetus infection in cats?

Tritrichomonas foetus is a parasite that has been definitively identified as an agent of trichomonosis, a disease characterized by chronic diarrhea. T. foetus colonizes portions of the feline large intestine, and manifests as chronic and recurrent diarrhea with mucus and fresh blood, which is often unresponsive to common drugs. Diagnosis of a trichomonad infection is made by either the demonstration of the trophozoite on a direct fecal smear, fecal culture and subsequent microscopic examination of the parasite, or extraction of DNA in feces and amplification by the use of molecular tools. T. foetus is commonly misidentified as other flagellate protozoa such as Giardia duodenalis and Pentatrichomonas hominis. Without proper treatment, the diarrhea may resolve spontaneously in months to years, but cats can remain carriers of the parasite. This paper intends to serve as a source of information for investigators and veterinarians, reviewing the most important aspects of feline trichomonosis, such as trichomonad history, biology, clinical manifestations, pathogenesis, world distribution, risk factors, diagnosis, and treatment.

Trichomonas

The most widely known trichomonad in veterinary medicine is Tritrichomonas foetus. It is the etiologic agent of bovine tritrichomonosis, a sexually transmitted disease in extensively managed herds throughout many geographic regions worldwide. The same trichomonad species is also regarded as the causative agent of chronic diarrhea in the domestic cat, although more recent studies observed molecular differences between bovine- and feline-derived T. foetus. Trichomonosis in cats has a worldwide distribution and is mainly present among cats from high-density housing environments. Other trichomonads are found as inhabitants of the gastrointestinal tract in birds, such as Trichomonas gallinae. Particularly, Columbiformes, Falconiformes, Strigiformes, and wild Passeriformes can be severely affected by avian trichomonads. Diagnosis of trichomonosis is often complicated by the fragility of the parasite. To ensure valid test results, it is essential to collect and handle specimens in the right way prior to analysis. Cultivation tests, the specific amplification of parasites, or a combination of both test methods is the most efficient and most commonly used way to diagnose trichomonosis in animals. Bovine tritrichomonosis is mainly controlled by the identification and withdrawal of infected animals from bovine herds. The control of feline and avian trichomonosis relies mainly on preventive measures.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Trichomonosis

Trichomonosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of trichomonosis to be listed, Article 9 for the categorisation of trichomonosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to trichomonosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, trichomonosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in sections 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for trichomonosis according to Article 8(3) criteria is cattle as susceptible and reservoir.

Detection of Tritrichomonas Foetus by Polymerase Chain Reaction in Cultured Isolates, Cervicovaginal Mucus, and Formalin-Fixed Tissues from iNfected Heifers and Fetuses

A rapid, reliable polymerase chain reaction (PCR) assay, originally developed for definitive laboratory identification of the bovine venereal pathogen Tritrichomonas foetus from cultures of male reproductive tract fluids, was used for testing the following: 1) cultured, geographically disparate trichomonad isolates, 2) formalin-fixed tissues from infected heifers and naturally infected fetuses, and 3) cervicovaginal mucus (CVM) from experimentally infected females. In 12 of 12 Western Hemisphere isolates of pathogenic T. foetus (isolated from outbreaks of clinical trichomoniasis or from screening surveys) and in 1 of 1 American Type Culture Collection strain of Tritrichomonas suis, PCR yielded a positive result, i.e., a 347—base pair amplicon in the 5.8S ribosomal RNA and internal transcribed spacer (5.8S—ITS) region of the genome, whereas cultures of Trichomonas vaginalis and Trichomonas gallinae did not produce a PCR product. The PCR assay was also positive in formalin-fixed, paraffin-embedded endometrial samples from 4 of 4 experimentally infected heifers, as well as in archived tissues from 2 of 2 T. foetus—infected aborted bovine fetuses that were submitted to the diagnostic laboratory from a natural outbreak. It was negative in fixed, embedded uterine tissues of 2 of 2 uninfected virgin heifers used as negative controls and in archived fixed gut tissue of a T. gallinae—infected pigeon. In another experiment, CVM aspirated from 4 of 4 experimentally infected heifers in the fifth or sixth postinfection week yielded a positive PCR product of the expected size, whereas CVM from 2 of 2 controls were PCR negative. Pending validation in larger clinical studies, the PCR assay for the 5.8S—ITS coding region of the T. foetus genome offers the prospect of definitive identification of this agent directly from CVM or from formalin-fixed tissues or when false-positive culture results are suspected.

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.

Evaluation of effects of high incubation temperatures on results of protozoal culture and real-time PCR testing for Tritrichomonas foetus inoculated in a commercially available self-contained culture media system

OBJECTIVE

To evaluate effects of high incubation temperatures on results of protozoal culture and real-time PCR testing for Tritrichomonas foetus inoculated in a commercially available self-contained culture media system.

DESIGN

In vitro experimental study.

SAMPLE

2 strains of T foetus (1 field isolate from the University of California-Davis and 1 field isolate from the Texas Veterinary Medical Diagnostic Laboratory).

PROCEDURES

2 sets of 36 dual-chamber media pouches were inoculated with T foetus (36 sample pouches/strain) and incubated at temperatures of 37.0°C (98.6°F), 46.1°C (115.0°F), or 54.4°C (130.0°F) for 1, 3, 6, or 24 hours. Six uninoculated media samples in pouches stored at 37.0°C for the entire treatment period were used as negative controls. Pouches were removed from incubators and stored at 22.2°C (72.0°F) until all treatments were complete. Samples were submitted to a diagnostic laboratory for protozoal culture and real-time PCR testing.

RESULTS

T foetus was detectable microscopically in inoculated pouches incubated at 37.0°C regardless of exposure time, whereas those incubated at 46.1°C yielded T foetus after 1 and 3 hours only, and those incubated at 54.4°C yielded T foetus after 1 hour only. Testing via real-time PCR assay yielded positive results for all inoculated media samples and negative results for all uninoculated control samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Samples collected into the self-contained culture media system for T foetus testing via culture alone should be protected from high temperatures. Realtime PCR amplification may be a more reliable method for identification of the organism if storage and transport temperatures cannot be controlled.

[Primers design and optimization of PCR and nested-PCR assays for the specific detection of Tritrichomonas foetus]

Tritrichomonas foetus is a pathogenic protozoan that causes a venereal disease in cattle known as bovine genital tricomonosis. In spite of the efficacy to recognize the target genomic DNA, the protocols so far developed for the diagnosis of this organism by PCR promote some inespecific amplifications or they are unable to discriminate T. foetus against other species within the genus. The objective of this study was to assess and optimize PCR and nested-PCR assays for the specific diagnosis of T. foetus, using novel primers selected from the alignment of sequences of the genes 18S rRNA, 5.8S rRNA, 28S rRNA and of the internal transcribed spacers of the rDNA (ITS1 and ITS2). A pair of primers was constructed for the genus-specific amplification of a 648 bp fragment and two others to amplify T. foetus species-specific fragments of 343 and 429 bp. No cross amplification was observed against Bos taurus genomic DNA neither against the DNA of usual bovine genital pathogens. Both, single and nested-PCR assays, presented analytical sensitivity to detect at least two T. foetus organisms.

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.

Improved detection of Tritrichomonas foetus in bovine diagnostic specimens using a novel probe-based real time PCR assay

A Tritrichomonas foetus-specific 5' Taq nuclease assay using a 3' minor groove binder-DNA probe (TaqMan MGB) targeting conserved regions of the internal transcribed spacer-1 (ITS-1) was developed and compared to established diagnostic procedures. Specificity of the assay was evaluated using bovine venereal microflora and a range of related trichomonad species. Assay sensitivity was evaluated with log(10) dilutions of known numbers of cells, and compared to that for microscopy following culture (InPouch TF test kit) and the conventional TFR3-TFR4 PCR assay. The 5' Taq nuclease assay detected a single cell per assay from smegma or mucus which was 2500-fold or 250-fold more sensitive than microscopy following selective culture from smegma or mucus respectively, and 500-fold more sensitive than culture followed by conventional PCR assay. The sensitivity of the conventional PCR assay was comparable to the 5' Taq nuclease assay when testing purified DNA extracted from clinical specimens, whereas the 5' Taq nuclease assay sensitivity improved using crude cell lysates, which were not suitable as template for the conventional PCR assay. Urine was evaluated as a diagnostic specimen providing improved and equivalent levels of T. foetus detection in spiked urine by both microscopy following culture and direct 5' Taq nuclease detection, respectively, compared with smegma and mucus, however inconclusive results were obtained with urine samples from the field study. Diagnostic specimens (n=159) were collected from herds with culture positive animals and of the 14 animals positive by 5' Taq nuclease assay, 3 were confirmed by selective culture/microscopy detection (Fisher's exact test P<0.001). The 5' Taq nuclease assay described here demonstrated superior sensitivity to traditional culture/microscopy and offers advantages over the application of conventional PCR for the detection of T. foetus in clinical samples.

PCR detection of Tritrichomonas foetus in preputial bull fluid without prior DNA isolation

Tritrichomonosis is a widespread, economically important venereal disease caused by Tritrichomonas foetus. The traditional diagnosis of this disease, which causes infertility and abortion in cattle, is based on the culture of the parasite. This process is time consuming, has low sensitivity, and is prone to contamination with intestinal or coprophilic trichomonadid protozoa, resulting in false positive diagnostics of T. foetus. In order to avoid the shortcomings of the traditional method, we developed a simple PCR assay based on TFR3 and TFR4 primers, which does not require parasite culturing. The sensitivity of the PCR assay resulted comparable to that of the classical method, being able to detect as few as five T. foetus parasites. In addition the method is highly specific. The analysis of preputial fluid washing samples showed that 58 out of 203 samples were positive by both, the PCR and the culture method (+/+), 9 samples were positive by PCR and negative by the traditional method (+/-) and only one sample resulted negative by PCR and negative by culture (-/+). The samples for the PCR assay can be stored for a week at 4 degrees C or 72h at room temperature. In summary, our study demonstrated that the PCR assay is an effective method for the diagnosis of T. foetus from preputial samples, and that it compares advantageously to the classical method.

An improved molecular assay for Tritrichomonas foetus

Tritrichomonas foetus (T. foetus) is the causative agent of bovine trichomonosis, a sexually transmitted disease leading to abortion (from 1 to 8 months gestation), infertility, and occasional pyometra. The annual losses to the U.S. beef industry are estimated to be in the hundreds of millions of dollars. Currently, the "gold standard" diagnostic test for trichomonosis in most countries is the cultivation of live organisms from reproductive secretions. The cultured organisms can then be followed by PCR assays with primers that amplify T. foetus to the exclusion of all other trichomonad species. Thus, negative results present as null data, indistinguishable from failed PCR amplification during T. foetus specific amplification. Our newly developed assay improves previously developed PCR based techniques by using diagnostic size variants from within the internal transcribed spacer 1 (ITS1) region that is between the 18S rRNA and 5.8S rRNA subunits. This new PCR assay amplifies trichomonad DNA from a variety of genera and positively identifies the causative agent in the bovine trichomonad infection. This approach eliminates false negatives found in some current assays as well as identifying the causative agent of trichomonad infection. Additionally, our assay incorporates a fluorescently labeled primer enabling high sensitivity and rapid assessment of the specific trichomonad species. Moreover, electrophoretic separation of amplified samples can be outsourced, thus eliminating the need for diagnostic laboratories to purchase expensive analysis equipment.

Evaluation of a PCR test for the diagnosis of Tritrichomonas foetus infection in bulls: effects of sample collection method, storage and transport medium on the test

The objectives of this study were to determine the detection limit of a PCR test for Tritrichomonas foetus, to investigate the effect of sampling method, guanidinium thiocyanate (GuSCN), and sample storage, and to confirm the accuracy of the test on field samples. Serial 10-fold dilutions of culture material were used to determine the detection limit. For the sample handling trial, five positive bulls were sampled by sheath washing and scraping on six occasions over a period of 18 days (n=29 samples) and eight control bulls were sampled three, four or six times (n=28 samples). Samples were cultured, while portions with and without GuSCN were subjected to DNA extraction within 6h, after 30 h and after 5 days at 4 degrees C. PCR and agarose gel electrophoresis was performed. A two-tailed chi-square test was used to test for differences between treatments. The PCR assay showed a specificity of 98%. Its sensitivity declined with storage time, from 90% at 6h to 31% at 5 days. Sampling method and GuSCN had no effect on test sensitivity. The detection limit of the assay was 100 organisms. Parallel testing of 193 field samples gave complete agreement between culture and PCR results.

Single-tube nested PCR for detection of tritrichomonas foetus in feline feces

Tritrichomonas foetus, a venereal pathogen of cattle, was recently identified as an inhabitant of the large intestine in young domestic cats with chronic diarrhea. Recognition of the infection in cats has been mired by unfamiliarity with T. foetus in cats as well as misdiagnosis of the organisms as Pentatrichomonas hominis or Giardia sp. when visualized by light microscopy. The diagnosis of T. foetus presently depends on the demonstration of live organisms by direct microscopic examination of fresh feces or by fecal culturing. As T. foetus organisms are fastidious and fragile, routine flotation techniques and delayed examination and refrigeration of feces are anticipated to preclude the diagnosis in numerous cases. The objective of this study was to develop a sensitive and specific PCR test for the diagnosis of feline T. foetus infection. A single-tube nested PCR was designed and optimized for the detection of T. foetus in feline feces by using a combination of novel (TFITS-F and TFITS-R) and previously described (TFR3 and TFR4) primers. The PCR is based on the amplification of a conserved portion of the T. foetus internal transcribed spacer (ITS) region (ITS1 and ITS2) and the 5.8S rRNA gene. The absolute detection limit of the single-tube nested PCR was 1 organism, while the practical detection limit was 10 organisms per 200 mg of feces. Specificity was examined by using P. hominis, Giardia lamblia, and feline genomic DNA. Our results demonstrate that the single-tube nested PCR is ideally suited for (i) diagnostic testing of feline fecal samples that are found negative by direct microscopy and culturing and (ii) definitive identification of microscopically observable or cultivated organisms.

An improved polymerase chain reaction assay for the detection of Tritrichomonas foetus in cattle

An improved polymerase chain reaction test has been developed to detect Tritrichomonas foetus, the causative agent of trichomoniasis in cattle. The test amplifies a region of the 5.8S ribosomal RNA gene of T. foetus, and it is simple, sensitive, and specific when compared with traditional methods to examine field samples.

Application of a PCR assay to enhance the detection and identification of Tritrichomonas foetus in cultured preputial samples

The traditional diagnostic test for Tritrichomonas foetus involves collection of preputial or vaginal samples followed by culture in a growth media and microscopic examination. Recently, polymerase chain reaction (PCR) techniques have been described for use as a diagnostic assay. The objective of this study was to evaluate a previously described PCR assay for detecting T. foetus in cultured preputial material. The detection limits of the assay for T. foetus organisms in a growth medium, in samples prepared from washing microscope slides, and in preputial material cultured in a growth medium were determined. Preputial samples were collected from 13 bulls uninfected with T. foetus. The PCR assay was able to detect 5 T. foetus organisms in the growth medium and the cultured preputial material. Amplification products were obtained from samples prepared from washes of microscope slides containing as few as 3 visualized organisms. The PCR assay was able to detect organisms in culture at a lower concentration than was possible by direct microscopic examination. This low detection limit may allow the PCR assay to be used to enhance the sensitivity of the current diagnostic test. In addition, the assay could be used to confirm the identification of T. foetus organisms observed by direct microscopic examination when other confirmation techniques, such as staining and phase microscopy, are not practical.

Effects of temperature on the survival of Tritrichomonas foetus in transport, Diamond's and InPouch TF media

The abilities of two isolates of Tritrichomonas foetus to survive and replicate in transport and Diamond's medium or in the InPouch TF system (Bio-Med Diagnostics) when exposed to different temperatures for different periods were determined in a series of experiments. Tubes containing thioglycollate transport medium or pouches were inoculated with 4000 to 5000 organisms and kept for up to seven days at 37 degrees C, 22 degrees C, 4 degrees C, or -20 degrees C. When the holding time had elapsed, the numbers of motile T foetus were counted. Samples in transport medium were transferred to Diamond's medium, and both the pouches and tubes containing Diamond's medium were incubated at 37 degrees C. The cultures were examined and counted four or five times during the 10 to 14 day culture period. The sensitivity of the test under the different conditions, expressed as the number of positive cultures/the total number of samples x 100, varied from zero to 100 per cent depending upon the combination of variables considered. In each medium, with both isolates of T foetus, all samples kept for up to four days at 22 degrees C or 37 degrees C were positive. All cultures of samples kept more than five days at 4 degrees C were negative. No positive cultures were detected when samples were kept more than three hours at -20 degrees C. The day on which the cultures reached mean peak concentration varied with the temperature at which the samples had been kept before they were cultured.

Genetic variance of Trichomonas vaginalis isolates by Southern hybridization

In the present study, genomic DNAs were purified from Korean isolates (KT8, KT6, KT-Kim and KT-Lee) and foreign strains (CDC85, IR78 and NYH 286) of Trichomonas vaginalis, and hybridized with a probe based on the repetitive sequence cloned from T. vaginalis to observe the genetic differences. By Southern hybridization, all isolates of T. vaginalis except the NYH286 strain had 11 bands. Therefore all isolates examined were distinguishable into 3 groups according to their banding patterns; i) KT8, KT6 and KT-Kim isolates had 11 identical bands such as 1 kb, 1.2 kb, 1.6 kb, 1.9 kb, 2.3 kb, 2.7 kb, 3.2 kb, 3.4 kb, 3.8 kb, 4.9 kb and 6.0 kb. ii) The metronidazole-resistant IR78 strain had the same bands as KT-Lee isolate at bands of 1 kb, 1.2 kb, 1.6 kb, 1.8 kb, 2.1 kb, 2.5 kb, 2.7 kb, 2.9 kb, 3.4 kb, 5.0 kb and 6.0 kb. Bands of CDC85, metronidazole-resistant strain, were similar to those of IR78 and KT-Lee, except that 3.2 kb replaced 2.9 kb. iii) NYH286 particularly had 12 bands and band patterns were similar to IR78 with a few exceptions as follows: i) 6.2 kb in place of 6.0 kb, ii) 2.0 kb and 2.2 kb instead of 2.1 kb. Through the results obtained, genetic variance of T. vaginalis isolates was demonstrated by Southern hybridization.

Detection of Tritrichomonas foetus by PCR and DNA enzyme immunoassay based on rRNA gene unit sequences

Tritrichomonas foetus is the causative agent of bovine tritrichomonosis, a sexually transmitted disease leading to infertility and abortion. Diagnosis is hampered by putative contamination of samples with intestinal or coprophilic trichomonadid protozoa which might be mistaken for T. foetus. Therefore, we developed a PCR test optimized for applicability in routine diagnosis. Amplification is based upon primers TFR3 and TFR4 directed to the rRNA gene units of T. foetus. In order to avoid potential carryover contamination by products of previous amplification reactions, conditions were adapted to the use of the uracil DNA glycosylase system. Furthermore, documentation and interpretation of results were facilitated by including a DNA enzyme immunoassay for the detection of amplification products. Specificity was confirmed with genomic material from different related trichomonadid protozoa. The high sensitivity of the test allowed the detection of a single T. foetus organism in diagnostic culture medium or about 50 parasites per ml of preputial washing fluid. The present methods are thus proposed as (i) confirmatory tests for microscopic diagnosis following diagnostic in vitro cultivation and (ii) a direct T. foetus screening test with diagnostic samples.

Pathogenesis, diagnosis, and management of trichomoniasis in cattle

Trichomoniasis is a disease of the pregnancy, but apparently not of either the cow or the bull, except in the case of postcoital pyometra. Its self-limiting nature in the cow and chronic nature in the bull mean that a positive diagnosis for the herd can more easily be obtained from bulls than from cows. Incubation of preputial scrapings or washings (or pyometritic fluid, if available) in a selective growth medium such as the InPouch system is the diagnostic method of choice. The diagnosis is based on identification of the morphology and characteristic rolling motility of the trichomonad. "High tech" molecular approaches may eventually offer greater diagnostic sensitivity than can culture methods, but currently they are no more accurate. In addition, serologic screening of the female herd (but interestingly, not the bulls) may become possible and may allow the practitioner to at least determine whether exposure has occurred in an unvaccinated herd. Control in an infected herd involves no pharmacologic treatment but rather culling of infected bulls, retention of younger, culture-negative bulls, and segregation of the female herd by reproductive status.

PCR-based study of conserved and variable DNA sequences of Tritrichomonas foetus isolates from Saskatchewan, Canada

The protozoan parasite Tritrichomonas foetus causes infertility and spontaneous abortion in cattle. In Saskatchewan, Canada, the culture prevalence of trichomonads was 65 of 1,048 (6%) among 1,048 bulls tested within a 1-year period ending in April 1994. Saskatchewan was previously thought to be free of the parasite. To confirm the culture results, possible T. foetus DNA presence was determined by the PCR. All of the 16 culture-positive isolates tested were PCR positive by a single-band test, but one PCR product was weak. DNA fingerprinting by both T17 PCR and randomly amplified polymorphic DNA PCR revealed genetic variation or polymorphism among the T. foetus isolates. T17 PCR also revealed conserved loci that distinguished these T. foetus isolates from Trichomonas vaginalis, from a variety of other protozoa, and from prokaryotes. TCO-1 PCR, a PCR test designed to sample DNA sequence homologous to the 5' flank of a highly conserved cell division control gene, detected genetic polymorphism at low stringency and a conserved, single locus at higher stringency. These findings suggested that T. foetus isolates exhibit both conserved genetic loci and polymorphic loci detectable by independent PCR methods. Both conserved and polymorphic genetic loci may prove useful for improved clinical diagnosis of T. foetus. The polymorphic loci detected by PCR suggested either a long history of infection or multiple lines of T. foetus infection in Saskatchewan. Polymorphic loci detected by PCR may provide data for epidemiologic studies of T. foetus.

Bovine vaginal antibody responses to immunoaffinity-purified surface antigen of Tritrichomonas foetus

Bovine trichomoniasis is a prevalent sexually transmitted disease of cattle caused by the protozoan Tritrichomonas foetus. Currently, diagnosis is most often made by culture. In order to provide a faster immunodiagnostic approach, a specific enzyme-linked immunosorbent assay (ELISA) was investigated. A protective surface antigen (TF1.17 antigen) of T. foetus was immunoaffinity purified and used in an ELISA to detect antibodies in vaginal mucus from heifers inoculated with T. foetus. In preliminary studies, antibodies of the immunoglobulin A (IgA) isotype were detected in mucus from all experimentally infected heifers which were tested at 6 weeks postinoculation, whereas IgG1 and IgG2 were not. In addition, IgA responses detected in postinoculation samples were all greater than those detected in preinoculation samples, unlike those detected by a whole-cell antigen ELISA. For these two reasons, IgA antibodies appeared to be useful diagnostically. Further investigation of IgA antibodies used vaginal mucus collected weekly from heifers inoculated intravaginally with 10(2), 10(4), or 10(6) T. foetus organisms. Heifers with positive cultures for T. foetus had similar IgA responses to TF1.17 antigen over the 10 weeks of infection regardless of the initial inoculum dose. This indicates that if the dose is sufficient to establish infection, the magnitude and duration of the immune response are no longer dependent on dose. All of the infected animals receiving all dosages responded with high absorbance values in the IgA anti-TF1.17 antigen ELISA by 6 weeks postinoculation, and all absorbance values remained high at 10 weeks. To determine the duration of the IgA response, four other heifers inoculated with 7 x 10(6) T. foetus organisms were studied through 24 weeks postinoculation. IgA antibody responses to TF1.17 antigen were still high at 24 weeks, even though some heifers cleared the infection several weeks earlier. These results indicate that experimentally infected heifers produced detectable long-lasting IgA responses to TF1.17 antigen in vaginal mucus, which may be useful in a herd test for the diagnosis of bovine trichomoniasis.

Applications of DNA amplification techniques in veterinary diagnostics

An overview of the principles of the polymerase chain reaction, ligase chain reaction, self-sustained sequence replication and Q beta replicase is given. The application of these methods for the diagnosis of veterinary infectious and hereditary diseases as well as for other diagnostic purposes is discussed and comprehensive tables of reported assays are provided. Specific areas where these DNA-based amplification methods provide substantial advantages over traditional approaches are also highlighted. With regard to PCR-based assays for the detection of viral pathogens, this article is an update of a previous review by Belák and Ballagi-Pordány (1993).

Protozoal causes of reproductive failure in domestic ruminants

Protozoan parasites are a significant cause of abortion and infertility in domestic ruminants. Toxoplasma gondii, a widespread cause of abortion in sheep and goats, and Sarcocystis spp., which cause a common, frequently asymptomatic infection of domestic ruminants, both have a two-host life cycle. Carnivorous definitive hosts spread the infection through their feces and domestic ruminants are intermediate hosts. A similar, recently recognized protozoa, Neospora sp., has emerged as an important cause of reproductive disease, especially as an abortifacient in dairy cattle. Neospora is presumed to also have a two-host life cycle, although the definitive host(s) has not been identified. The venereally transmitted Tritrichomonas foetus is an important cause of pregnancy loss in naturally bred cattle throughout the world. In the absence of effective methods for vaccination or treatment, control of these parasites is based on management procedures to reduce infection and transmission.