Spironucleus vortens, a possible cause of hole-in-the-head disease in cichlids

Hole-in-the-head disease is recorded in 11 discus Symphysodon discus Heckel, 1840 and 1 angelfish Pterophyllum scalare Lichtenstein, 1823 obtained from local aquarists within the Southwest of the UK. Spironucleus vortens Poynton et al. 1995, was isolated from the kidney, liver, spleen and head lesions of discus showing severe signs of the disease and from the intestines of all fish. The hexamitid was also recorded from the head lesions of the angelfish. The identity of these flagellates was confirmed as S. vortens on the basis of topographical features seen with the aid of SEM. A modified in vitro culture method was successfully developed for the detection, isolation and long-term maintenance of S. vortens. The flagellate was sub-cultured at 3 to 5 d intervals, new media being supplemented with fresh liver from Oreochromis niloticus (Linnaeus, 1757) free from infection. The results are discussed in relation to S. vortens as the causative agent for hole-in-the-head disease following systemic infection via the digestive tract.

Immunological and biochemical analysis of glycosylated surface antigens and lipophosphoglycan of Tritrichomonas foetus

Immunoaffinity-purified TF1.17 adhesin antigen was compared biochemically and antigenically to Tritrichomonas foetus (TF) lipophosphoglycan (LPG) and a soluble glycosylated antigen (SGA) released from T. foetus and implicated in pathogenesis and immunity. The monoclonal antibodies (Mabs TF1.15 and TF1.17) specific for a glycosylated TF1.17 antigen were previously shown to prevent adhesion of the T. foetus parasites to bovine vaginal epithelial cells and to mediate killing by bovine complement. SGA was isolated from T. foetus-conditioned buffer and purified by octyl-Sepharose hydrophobic column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of SGA showed a major SGA1 component (approximately 190 kDa) and a minor SGA2 component (50-70 kDa), which migrated close to TF-LPG and TF1.17. The carbohydrate and lipid compositional analyses of affinity-purified TF1.17 and SGA2 by high-performance liquid chromatography (HPLC) and gas-liquid chromatography revealed the presence of monosaccharides and fatty acids as found in TF-LPG. All antigens contained terminal fucose as determined by alpha-fucosidase digestion followed by HPLC. ELISA and western blots were used to further characterize these glycosylated antigens and to analyze their relationships. The Mabs TF1.15 and TF1.17 reacted very strongly to TF-LPG and SGA2. as well as TF1.17 antigen, indicating that these molecules share common epitopes. These Mabs did not react with the SGA1 component either in ELISA and western blot analyses. Also, the monosaccharide composition of SGA1 was very different from the other three antigen, suggesting SGA1 was different from LPG, SGA2 and TF1.17. Although LPG reacted with Mabs to native TF1.17 antigen, LPG did not induce an immune response in cattle with the same route and adjuvant used to produce strong antibody responses to the native antigen. The latter response suggests that the tightly bound peptide present in the immunoaffinity-purified antigen is necessary for induction of a response to (an) epitope(s) in TF-LPG and TF1.17. Furthermore, vaginal fluid from T. foetus-infected heifers and serum from a cow with a T. foetus-associated pyometra recognized both TF1.17 and TF-LPG in western blots. These results suggest that T. foetus LPG and SGA2 are related to TF1.17 antigen, which was previously shown to play an important role in the pathogenesis and host response in bovine trichomoniasis.

Growth kinetic study of Tetratrichomonas didelphidis isolated from opossum Lutreolina crassicaudata and interaction with a prokaryotic cell

Tetratrichomonas didelphidis is a flagellate protozoan found in the intestine, cecum and colon of opossums, Didelphis marsupialis. This work reports the occurrence of T. didelphidis in another opossum species, Lutreolina crassicaudata. The strain was cultivated in monoxenic culture with Escherichia coli in Diamond (TYM) medium without maltose and with starch solution (trypticase-yeast extract-starch), pH 7.5 at 28 degrees C. The growth kinetic study of T. didelphidis showed a longer time of growth and a higher number of trophozoites when inoculated with E. coli than in axenic cultures, in aerobiosis as well as under anaerobic conditions. Scanning electron microscopy showed that the bacteria adhered throughout the protozoan body and probably evoked endocytic channels, strongly suggesting the existence of endocytosis of rods by T. didelphidis. Our preliminary results suggest that the in vitro culture of T. didelphidis depends on E. coli as a growth-promoting partner, and requires monoxenic cultivation.

Experimental infection with Tritrichomonas suis in heifers

Nine heifers were intravaginally challenged with 9.3x10(6) Tritrichomonas suis reference strains. Vaginal mucus and serum samples were collected weekly 4 weeks post-inoculation. Vaginal mucus was cultured for T. suis and sera was tested by ELISA against whole cell antigens for T. suis and Tritrichomonas foetus. All vaginal mucus cultures were T. suis-negative during the experiment. ELISA values for both antigens were similar and differences were not significant (P>0.05). Positive control serum samples from one heifer vaccinated against T. foetus showed anti-T. suis ELISA values. We concluded that T. suis intravaginal inoculation induced a low level of serum immune response in heifers measured by ELISA and both protozoa probably share a common antigen. However, under the experimental conditions of this trial, colonization of the heifers' genital tract was not possible in any of the nine animals.

Cryptobiosis and its control in North American fishes

Cryptobiosis is caused by the haemoflagellates Cryptobia bullocki and Cryptobia salmositica. These parasites infect food fishes (e.g. flounders, salmon) on both the Atlantic and Pacific coasts of North America and clinical signs of the disease include anaemia, and abdominal distention with ascites. The virulent factor in salmonid cryptobiosis, caused by C. salmositica, is a secretory metalloprotease (200 kDa). Fish mortality may be up to 100% in the absence of treatment, consequently strategies have been developed to protect them from disease/mortality. A single dose of a live vaccine protects fish for at least 2 years, and it is via the production of complement-fixing antibodies, enhanced phagocytosis and cell-mediated cytotoxicity. Inhibition of the parasite's cysteine protease by a monoclonal antibody reduces multiplication, infectivity and survival of the parasite. Consequently, the recombinant cysteine protease (49 kDa) of the parasite will be tested as a potential vaccine. The trypanocidal drug, isometamidium chloride (1.0 mg/kg), is effective (therapeutic and prophylactic) against C. salmositica in chinook salmon. Its efficacy is significantly enhanced if it is conjugated either to a monoclonal antibody or to polyclonal antibodies from immune fish. Selective breeding of Cryptobia-resistant brook charr (innate resistance to infection) is possible, and the resistant factor(s) is controlled by a dominant Mendelian locus. In these resistant charr the parasite is lysed via the alternate pathway of complement activation (innate immunity to infection). There are also Cryptobia-tolerant charr, fish that are susceptible to infection but have no clinical disease (innate resistance to disease). In these fish, one of the natural anti-proteases, alpha2-macroglobulin, neutralises the metalloprotease secreted by C. salmositica. Production of transgenic Cryptobia-tolerant salmon is an option to vaccination and or chemotherapy. Also, transgenic pathogen-tolerant animals may be an alternate strategy against other pathogens where the disease mechanism is similar to cryptobiosis.

The in vitro effects of isometamidium chloride (Samorin) on the piscine hemoflagellate Cryptobia salmositica (Kinetoplastida, Bodonina)

Isometamidium chloride (Samorin) is therapeutic in rainbow trout (Oncorhynchus mykiss) during preclinical and chronic cryptobiosis. However, the toxic mechanism of isometamidium on Cryptobia salmositica has not been elucidated. The objective of the present study was to examine the in vitro effects of isometamidium on C. salmositica. Under in vitro conditions, isometamidium chloride reduced the infectivity of C. salmositica suspended in whole fish blood. It accumulated rapidly in the kinetoplast (within 1 min) and caused disruption and decantenation of kinetoplast DNA. The in vitro cryptobiacidal activity of isometamidium was reduced when parasites were incubated in medium containing serum supplement, suggesting that isometamidium also binds to plasma proteins. Isometamidium altered glycoprotein receptors (epitopes) for antibodies on the surface of C. salmositica and thus protected some of the parasites from lysis by complement-fixing antibodies. In vitro oxygen consumption and carbon dioxide production decreased in drug-exposed C. salmositica, with increased products of glycolysis, i.e., lactate and pyruvate, after exposure to isometamidium. This suggests that some C. salmositica switched from aerobic respiration to glycolysis when the mitochondrion was damaged by isometamidium.

Therapeutic and prophylactic effects of isometamidium chloride (Samorin) against the hemoflagellate Cryptobia salmositica in chinook salmon (Oncorhynchus tshawytscha) and the effects of the drug on uninfected rainbow trout (O. mykiss)

A series of compounds (triphenylmethanes, thiazines, xanthenes, benzidines, phenanthridiniums, napthalamines, and diamidines) were screened for in vitro toxicity against Cryptobia salmositica. Isometamidium chloride (Samorin) was cryptobiacidal at low concentrations and was examined for therapeutic and prophylactic activities against C. salmositica in chinook salmon (Oncorhynchus tshawytscha). An intramuscular dose (1.0 mg/kg) of Samorin 3 weeks post-infection significantly reduced the parasitemia in adult chinook. A higher dose (2.5 mg/kg) eliminated the infection in 30% of adult fish and parasitemias were significantly reduced in the remaining infected fish. Juvenile chinook treated with 1.0 mg Samorin/kg at 2-3 weeks post-infection survived, while 100% of untreated control fish died from cryptobiosis. The high dose (2.5 mg/kg) was lethal to small fish (98.93 +/- 12.09 g) and 50% died within 24 h of treatment, while all large fish (168.38 +/- 13.87 g) survived. Samorin (1.0 mg/kg) did not affect growth, food consumption, complement, or hematocrit values in uninfected rainbow trout (O. mykiss).

Comparison of growth rates of Tritrichomonas foetus isolates from various geographic regions using three different culture media

The growth rates of 16 isolates of Tritrichomonas foetus from three distinct geographic regions were investigated in modified Diamond's medium, liver infusion broth medium and a commercially available culture kit. While some differences in growth characteristics were detected for different isolates and in the three different media, all isolates grew. Trichomonads reached peak concentrations from an initial concentration of 10(4) trichomonads/ml on Days 2, 3 and 4 in modified Diamond's medium, on Days 2-6 (excluding CAPTF102) in the commercial culture kit and on Days 2-7 in liver infusion broth medium. Viable parasites were detectable for longer periods in liver infusion broth medium and the commercial culture kit than in Diamond's medium. Peak concentrations for isolates tended to be higher in modified Diamond's medium than in liver infusion broth medium or the commercial culture kit. Results show that these three media are suitable for the growth of all 16 T. foetus isolates from three continents and suggest that these media could be used effectively throughout the world.

Pentatrichomonas hominis infection in four kittens

Four purebred domestic cats examined because of diarrhea were found to have Pentatrichomonas hominis, a rarely reported trichomonad parasite, in their feces. Treatment with a combination of metronidazole and enrofloxacin tended to improve consistency of the feces, whereas treatment with metronidazole alone reduced the number of P hominis trophozoites in fecal smears but did not necessarily result in an improvement in clinical signs. Two cats were euthanatized. Necropsy revealed lymphoplasmacytic enterocolitis with eosinophils and eosinophilic globular leukocytes, neutrophils in the mucosa of the colon and within intraluminal contents of the cecum, and P hominis trophozoites in intraluminal contents of the colon and cecum.

Tritrichomonas foetus extracellular cysteine proteinase cleavage of bovine IgG2 allotypes

Bovine trichomoniasis is a sexually transmitted disease associated with reproductive failure. Systemic immunization results in protective IgG antibodies in uterine and vaginal secretions. Because bovine IgG2 is a better opsonin than IgG1, it is potentially important in defense. Yet, Tritrichomonas foetus extracellular cysteine proteinase (TFECP) cleaves bovine IgG2, evading protective IgG2 responses. Variations in resistance of the 2 IgG2 allotypes to digestion may explain inherited differences in protection. To address this hypothesis, TFECP was incubated with both IgG2 allotypes at different concentrations and times. The digestion products were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, stained, and quantitated by image analysis. IgG2a was digested faster by TFECP than IgG2b. Differences in the sizes and numbers of digestion products were observed, but the presence of bands the size of Fc and Fd fragments indicated that both allotypes were cleaved at the hinge. Cysteine in the digestion mixture reduced the antibody molecules and increased the rate of digestion, but IgG2a was still more susceptible to cleavage than IgG2b in the absence of cysteine. Thus, not only reduced H chains can be cleaved by cysteine proteinase secreted by T. foetus but also intact functional antibody molecules. Because parasites may evade protective antibody responses by cleaving IgG2, animals with the more resistant IgG2b allotype may be better protected by immunization than animals with the more readily digested IgG2a allotype.

In vitro studies on optimal requirements for the growth of Spironucleus vortens, an intestinal parasite of the freshwater angelfish

Spironucleus vortens were cultivated in either an artificial medium at different temperatures, or in medium at various pH conditions or supplemented with different bile concentrations at 25 degrees C. Temperature, pH and bile requirements for the optimal growth of the parasite were determined. Parasites multiplied quickly at 28 and 31 degrees C and reached maximum numbers on Day 4 of cultivation, whereafter they did not survive. At 25 degrees C, parasites survived longer than those at 28 and 31 degrees C with no difference in multiplication rate during the exponential phase. The longest survival period was seen at 22 degrees C, although the growth rate of the parasite was not as high as those at 25 degrees C. At a higher temperature of 37 degrees C, no parasites were observed alive after the second day of cultivation. Optimal pH range for the parasite's growth was 6.5 to 7.5, with the highest cell number at pH 7.5. Parasites survived longest (15 d) at pH 6.0, although the maximum number of cells was lower than those at the optimal pH. Parasites were dead within 24 h at pH levels above 8.5 or below 5.5. All cultures supplemented with either bovine or fish bile yielded numbers of parasites lower than cultures with no bile. In addition, parasite growth was significantly suppressed in medium supplemented with higher concentrations of bile. These results indicate that the optimal condition for the in vitro cultivation of S. vortens is 25 degrees C and pH 6.5 to 7.5 without supplementation with bile.

Massive infestation by Amyloodinium ocellatum (Dinoflagellida) of fish in a highly saline lake, Salton Sea, California, USA

Persistent fish infestation by the parasitic dinoflagellate Amyloodinium ocellatum was found at a highly saline lake, Salton Sea, California, USA. The seasonal dynamics of the infestation of young tilapia was traced in 1997-1998. First appearing in May, it became maximal in June-August, decreased in October and was not detectable in November. Outbreak of the infestation and subsequent mortality of young fish was registered at the Sea at a water temperature and salinity of 40 degrees C and 46 ppt, respectively. Some aspects of the ultrastructure of parasitic trophonts of A. ocellatum and their location on the fish from different size groups are considered. The interactions of parasitological and environmental factors and their combined effect upon fish from the Salton Sea are discussed.

Efficacy of various chemotherapeutic agents on the growth of Spironucleus vortens, an intestinal parasite of the freshwater angelfish

Seven chemotherapeutic agents (dimetridazole, metronidazole, pyrimethamine, albendazole, fenbendazole, mebendazole and magnesium sulfate) were examined for growth inhibition on the cultivation of Spironucleus vortens. Dimetridazole and metronidazole were effective in inhibiting the parasite's growth. At concentrations of 1 microgram ml-1 or higher, both dramatically decreased numbers of parasites. At 24 h exposure, 33% of parasites were inhibited when exposed to dimetridazole or metronidazole at concentrations of 2 and 4 micrograms ml-1, respectively. Dimetridazole at 4 micrograms ml-1 or higher concentrations decreased the number of organisms to 50% or less after 48 h exposure. During the same period of time, the numbers of parasites decreased to 50% or less when exposed to metronidazole at 6 micrograms ml-1 or higher. Pyrimethamine at concentrations of 1 to 10 micrograms ml-1 was not effective in inhibiting the parasite's growth. Albendazole and fenbendazole at concentrations of 0.1 and 0.5 microgram ml-1 were similar in inhibiting the growth of the organism. Both compounds suppressed parasite growth at concentrations of 1.0 microgram ml-1 or higher after 24 h exposure. Mebendazole inhibited the parasite's growth at concentrations of 0.5 microgram ml-1 or higher. At 72 h exposure, 45 to 50% of the parasites were inhibited when exposed to mebendazole at concentrations higher than 0.5 microgram ml-1. Magnesium sulfate at concentrations of 70 mg ml-1 or higher also suppressed the growth of parasites after 24 h exposure. These results indicate that dimetridazole, metronidazole and mebendazole are the most effective chemotherapeutic agents in vitro at inhibiting the growth of S. vortens.

The therapeutic use of isometamidium chloride against Cryptobia salmositica in rainbow trout Oncorhynchus mykiss

Rainbow trout Oncorhynchus mykiss injected intramuscularly with isometamidium chloride (0.01 or 0.1 mg kg-1) at 3 wk post-infection and given a booster 2 wk later had significantly lower parasitaemias than infected controls. Packed cell volume increased after treatment and remained higher than in infected controls. The concentration of isometamidium in plasma was highest at 2 wk after injection and then declined. An intramuscular dose of 1.0 mg kg-1 of isometamidium chloride at 1, 2 and 3 wk postinfection (preclinical) significantly reduced the parasitaemia in rainbow trout 2 wk after treatment. A booster at 9 wk postinfection (chronic disease phase) reduced the parasitaemia further in all fish. The packed cell volume in these fish was higher than in infected controls. Treatment at 5, 6, and 7 wk postinfection (acute disease) had no effects and parasitaemias in treated fish were higher than in infected controls; also, anti-Cryptobia salmositica antibodies and titres of complement-fixing antibody were higher in these than in infected controls. Incubation of immune plasma or complement with isometamidium for 3 h did not affect the lytic titres of complement-fixing antibodies nor rainbow trout complement.

Demonstration of Tritrichomonas foetus in the external genitalia and of specific antibodies in preputial secretions of naturally infected bulls

Portions of penis and prepuce were collected from 24 bulls with current or recent Tritrichomonas foetus infection. Epididymides were collected from seven of the bulls, and seminal vesicles and prostate were collected from four. Following immunohistochemical staining with two monoclonal antibodies (34.7C4.4 and TF1.15) prepared against T. foetus surface antigens, trichomonads were identified in sections from 15 of the bulls. Organisms were most often located in penile crypts in the midshaft and caudal regions and less often in preputial crypts. Trichomonads were not observed in sections from other genitalia or in subepithelial tissue. T. foetus antigen, however, was present in the cytoplasm of some epithelial cells and the cytoplasm of some mononuclear cells in subepithelial lymphoid aggregates and follicles. Preputial smegma was collected from 16 T. foetus-infected bulls and from 16 control bulls with negative T. foetus cultures. Preputial antibody levels to TF1.17, a surface antigen of T. foetus, were determined by an enzyme-linked immunosorbent assay. Preputial secretions from infected bulls contained specific antibody of each isotype and subisotype tested. IgG1 responses were the greatest, IgM and IgA responses were approximately equal, and IgG2 responses were low. Each isotype and subisotype response in infected bulls was significantly greater than that in the controls. These results confirm previous speculation concerning anatomical sites of infection and suggest that parasite antigen can be taken up and processed locally, resulting in deposition of specific IgG1, IgG2, IgA, and IgM antibodies in the preputial cavity.

Administration of diminazene aceturate or imidocarb dipropionate for treatment of cytauxzoonosis in cats

Bobcats (Lynx rufus) are the reservoir hosts for Cytauxzoon felis, the causative agent of cytauxzoonosis. Cytauxzoonosis is a highly fatal tickborne blood protozoal disease of domestic and exotic cats. Treatment of clinically affected cats has generally been unrewarding. In our report, 6 of 7 cats had signs of illness and laboratory findings indicative of cytauxzoonosis and were successfully treated with 2 i.m. injections of diminazene aceturate or imidocarb dipropionate (2 mg/kg [0.9 mg/lb] of body weight, each). One cat died after the first injection of diminazene. Additional treatment with isotonic fluids i.v. and heparin s.c. were used as supportive care for dehydration and disseminated intravascular coagulation that were detected by laboratory testing between diminazene or imidocarb treatments. Atropine was effective in recovery and preventing adverse reactions associated with imidocarb treatment of 1 cat.

Host-parasite interaction in bovine infection with Tritrichomonas foetus

Tritrichomonas foetus is a parasite of particular veterinary importance causing bovine tritrichomonosis, a sexually transmitted disease leading to infertility and abortion. The present review summarizes the current knowledge on potential mechanisms of pathogenicity of T. foetus, the immunology of host-parasite interaction in bovine tritrichomonosis, and the experimental model systems of this parasitic disease.

Comparison of two sampling tools for diagnosis of Tritrichomonas foetus in bulls and clinical interpretation of culture results

OBJECTIVE

To compare sensitivity for diagnosing Tritrichomonas foetus infection in bulls using 2 sampling tools and to calculate negative predictive values for infection.

DESIGN

Randomized clinical trial.

ANIMALS

30 Bos taurus bulls naturally or experimentally infected with T foetus.

PROCEDURE

Preputial scrapings were obtained once/wk for 6 weeks using an artificial insemination pipette and a metal brush; which tool was used first for each bull was randomly determined. Samples were collected first from the left side of the prepuce and then from the right side and placed in commercially available transport media chi 2 Values and confidence limits were adjusted for effect of clustering of results by bull.

RESULTS

Significant differences in sensitivity of results were not found between samples collected using the brush or pipette. Using the pipette, sensitivity was estimated to be 91.6% (95% confidence interval, 84.3 to 95.7%); negative predictive values ranged from 41 to 99% for prevalence of infection of 90 to 5%, respectively. Sensitivity was 88.8% for first sample obtained and 96.1% for second sample obtained.

CONCLUSIONS AND CLINICAL RELEVANCE

Collection of preputial scrapings with an artificial insemination pipette or a metal brush and use of a commercially available culture system can provide a sensitive diagnostic test for T foetus infection in bulls. Calculated negative predictive values indicated that 1 or 2 tests would suffice in most clinical situations. For bulls from herds in which T foetus is endemic, 2 to 4 tests/bull may be required to ensure that each bull is not infected.

Hematologic effects of cytauxzoonosis in Florida panthers and Texas cougars in Florida

Cytauxzoon felis is a long-recognized hemoparasite of free-ranging Florida panthers (Puma concolor coryi), but its prevalence and effect on the population has not been assessed. Red blood cell indices and white blood cell counts were compared between infected and noninfected Florida panthers and Texas cougars (Puma concolor stanleyana) from 1983-1997 in Florida (USA). The prevalence of cytauxzoonosis for both populations was 39% (11/28) for Texas cougars, 35% for Florida panthers (22/63) and 36% overall. Thirteen hematologic parameters were compared between C. felis positive and negative panthers and cougars. Florida panthers had significantly lower mean cell hemoglobin count (MCHC) and higher white blood cell (WBC), neutrophil, monocyte and eosinophil counts (P < or = 0.05) than Texas cougars. Infected Florida panthers had significantly lower mean cell hemoglobin (MCH) and monocyte counts and higher neutrophil and eosinophil counts than infected Texas cougars. Although statistically significant differences were measured for hematologic parameters in C. felis positive panthers and cougars, biologically significant differences were not likely because values were generally within expected reference ranges for healthy animals. Cytauxzoonosis does not appear to have a negative effect on the hematologic parameters of chronically infected panthers and cougars. Potential transient changes during initial infection were not evaluated.

Characterization of antigenic proteins from Tritrichomonas foetus recognized by antibodies in rabbit serum, bovine serum and bovine cervicovaginal mucus

Tritrichomonas foetus is an obligate parasite of the bovine urogenital tract and is recognized as 1 of the more common infectious agents causing decreased reproductive efficiency in beef cattle. Infections result in reproductive failure and produce considerable economic loss. Vaccination of heifers with vaccines containing T. foetus induces elevated serological responses to many T. foetus antigens, decreases the rate and/or length of infection with T. foetus, and decreases fetal loss caused by infection. Because T. foetus infections are usually limited to lumen and mucosal surfaces of the reproductive tract, it has been assumed that protection from infection and abortion is partially mediated by immunoglobulins in the uterus and vagina. The objective of this study was to identify and characterize specific antigens of T. foetus that show promise for use in a recombinant vaccine that will generate a protective mucosal immune response in cattle. Surface proteins were identified by using polyclonal rabbit anti-trichomonal sera eluted from paraformaldehyde-fixed cells. Analyses of these proteins, utilizing mucosal antibodies from vaccinated and convalescent cows, have identified proteins involved in generating a local immune response. Western immunoblot analysis indicates that these proteins are well conserved and are excellent candidates for incorporation into a recombinant vaccine.

Prevalence of Tritrichomonas fetus in a bull population and effect on production in a large cow-calf enterprise

OBJECTIVE

To determine prevalence of infection with tritrichomonas fetus in a bull population; assess influence of age, breed, and grouping; assess effects on measures of cow performance (pregnancy rate, weaning percentage, weaning weight); and estimate test sensitivity.

DESIGN

Epidemiologic study.

ANIMALS

1,383 bulls and records for 28,471 cows bred by these bulls in the immediate past breeding season.

PROCEDURE

Bulls in 11 cattle units on a large ranch were tested for T fetus colonization by vigorous preputial scraping and protozoologic culture until no newly infected bulls were identified. Bull infection prevalence within units was calculated and correlated to production measurements reported for each cattle unit.

RESULTS

Mean prevalence of T fetus-infected bulls was 11.9% (range, 0 to 35.9%). Significant difference was detected between mean age of infected bulls (5.5 years) and noninfected bulls (3.9 years). Difference in prevalence among breeds was found, although other factors may have influenced this finding. Cow performance measurements (weaning percentage, mean weaning weight, and adjusted mean weaning weight/exposed cow) for cows exposed by breeding to bull groups with the highest prevalence of infection (35.9%) were significantly different from mean values for the entire study population. Test sensitivity for this study (73%) was less than that reported in other studies.

CLINICAL IMPLICATIONS

T fetus infection in a natural service beef herd has an adverse impact on several production measures: Severity of impact is related to prevalence of infection in the bull population, where prevalence is bull age and population dependent.