Increased risk of abortion following Neospora caninum abortion outbreaks: a retrospective and prospective cohort study in four dairy herds

Explosive abortion outbreaks in 4 Dutch dairy herds during 1992 to 1994 are reported. In 50 of 51 fetuses submitted during the first 3 wk of the outbreaks characteristic histological lesions compatible for infection with Neospora caninum were seen. Diagnosis of infection was confirmed by immunohistochemistry in 40 fetuses (78%). No evidence for other abortifacients was found. The abortion risk of the herds was investigated in a prospective and retrospective cohort study. The prospective study showed that cows aborting during the outbreaks and N. caninum seropositive nonaborting cows had a two- to three-fold increased risk of abortion compared with N. caninum seronegative cows. Retrospective examination showed that seropositive nonaborting cows had an increased risk of abortion before the outbreaks, which may indicate that these animals were infected with N. caninum prior to the outbreaks. It is concluded that serostatus can be used for selective culling of cows to decrease future risk of abortion in dairy herds.     

Neospora caninum infection does not affect early pregnancy in dairy cattle

This study was designed to evaluate the relationship between Neospora caninum infection prior to pregnancy, as determined through maternal serology, and the subsequent occurrence of abortion in dairy cattle. Special emphasis was placed on pregnancy losses in the first trimester of pregnancy. Neospora caninum antibodies were analyzed by commercial ELISA in 2773 pregnant animals (2022 parous cows and 751 heifers) from six herds. The mean seroprevalence of antibodies to N. caninum in the herds was 15.1% (n = 419). From gestation Day 34 to the 90th day of pregnancy, there were 183 abortions (6.6% of all pregnancies) (23 in Neospora positive animals). After 90 days of pregnancy, the number of abortions was 146 (5.3%); 126 occurring during the second and 20 during the third trimester of pregnancy (105 in Neospora positive animals). Multiple logistic regression analyses were performed on data from each animal using abortion before or after 90 days of pregnancy as the dependent variable, and Neospora positivity, herd, pregnancy season, and parity (parous or nonparous) as independent factors. No significant effects of Neospora positivity and herd were found on the abortion rate before 90 days of pregnancy. Based on the odds ratio, the abortion rate was 4 times higher (P < 0.0001) in animals that became pregnant in the warm than in the cool period, and 3.7 times higher (P < 0.0001) in parous than in nonparous animals. Neospora positivity was the only variable included in the logistic regression model for abortions occurring after 90 days of pregnancy. Seropositivity in an animal increased the probability of abortion by an odds ratio of 18.9 (P < 0.0001; 95% confidence interval 12.9-27.8). Season, parity, and herd showed no effect. The results of the present study suggest that chronic N. caninum infection prior to pregnancy appears not to affect the early fetal period, but does have a significant abortive effect after 90 days of gestation.     

Early postabortion recovery of Neospora-infected lactating dairy cows

This study was designed to assess the reproductive performance of Neospora caninum–infected dairy cows (Bos taurus) after abortion. The population examined was composed of 92 aborting cows subsequently subjected to at least one artificial insemination (AI) attempt. Of these animals, 68 were N. caninum seropositive and 24 were seronegative. Only animals producing at least 25 kg milk at the estrus after abortion were inseminated. Normal uterine involution was verified at first AI after abortion in cows showing estrous signs within 30 d of abortion. Of the 92 aborting cows, 73 (79.3%) became pregnant after abortion: 57 (83.8%) and 16 (66.7%) of the N. caninum seropositive and seronegative cows, respectively. The factors days of gestation and lactation number at abortion failed to differ between the two Neospora serostatus groups, based on Student's t-test or Kruskal-Wallis tests, respectively. The interval from abortion to first AI, the number of AIs necessary for an animal to become pregnant, and the interval from abortion to next pregnancy in cows becoming pregnant were lower for the N. caninum–seropositive than for the N. caninum–seronegative cows (P < 0.0001). Logistic regression analysis indicated no significant effects of herd, lactation number, days of gestation at abortion, and the interval from abortion to AI on the likelihood of pregnancy at first AI after abortion. Based on the odds ratio, Neospora-seropositive cows were 6.22 times more likely to become pregnant at first AI after abortion compared with their seronegative partners. Fifty-three of the Neospora-seropositive cows (78%) were inseminated within 30 d after abortion and 26 (49%) became pregnant, whereas only one seronegative cow (4.2%) was ready for insemination within this 30-d period and remained open after first AI. These results indicate that Neospora-infected cows suffering abortion can be inseminated with a likelihood of high fertility within the first month of abortion. We recommend checking that uterine involution is normal early after abortion in N. caninum–seropositive cows.     

Plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations during gestation in Neospora-infected dairy cows

The aim of this study was to determine whether plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations in pregnancy are affected by persistent Neospora caninum infection in dairy cows. The data analyzed were derived from 22 multiparous cows: 16 N. caninum-seropositive and 6 N. caninum-seronegative animals (used as controls). Three of the 16 seropositive cows aborted during the study period and the corresponding data were analyzed separately. Pregnancy diagnoses were performed on day 40 post-insemination by transrectal ultrasound, and by palpation per rectum on days 90, 120, 150, 180 and 210. Blood samples were collected from each animal immediately before each pregnancy diagnosis, and then at parturition or at the time of abortion detection. Plasma was tested for antibodies against N. caninum and PAG-1 concentrations were determined by radioimmunoassay. In non-aborting animals, the effects of neosporosis (seropositive versus seronegative), N. caninum antibody levels, semen providing bull, sex of the newborn, and day of gestation on PAG-1 concentrations were evaluated by GLM repeated measures analysis of variance. The effect of the gestation period (first half versus second half) on the N. caninum antibody titer was established by the Student's t-test in seropositive cows. A significant positive effect of gestation day on PAG-1 concentrations was observed (d.f.=6; F=12.6; P<0.0001). For all cows, PAG-1 concentrations increased steadily during the course of gestation, with peak concentrations recorded at parturition. Neosporosis (P=0.493), N. caninum antibody levels (P=0.921), sex of the newborn (P=0.856) and semen providing bull (P=0.087) had no effect on plasma PAG-1 concentration. There was a significant 52% increase (P<0.0001) in N. caninum antibody titers during the second half of gestation compared to the first half. The fates of the three aborting cows were abortion on gestation day 215 in one, and fetus mummification diagnosed on gestation days 180 and 210, respectively, in the remaining two cows. A luteolytic dose of prostaglandin was applied 30 days after mummification diagnosis in these last two cows, and fetus expulsion was detected on days 215 and 250, respectively. Two of the aborted fetuses were submitted to laboratory analysis and the presence of N. caninum was confirmed by specific PCR. In the cows with a mummified fetus, PAG-1 concentrations were low or undetectable when the diagnosis was made. These findings suggest that N. caninum infection has no effect on placental function in chronically infected, cows not suffering abortion, while PAG-1 measurements in aborting animals provide a useful indication of feto-placental status.     

Transplacental transmission and abortion in cows administered Neospora caninum oocysts

Neospora caninum infection is a common cause of bovine abortion. One method by which cattle can acquire infection is through ingestion of oocysts; however, this has not yet been proved to cause transplacental infection or abortion. In this study, 19 cows, pregnant between 70 and 176 days, were administered 1500 to 115,000 oocysts through an esophageal tube. Seventeen of the cows became seropositive, indicating acquisition of infection, whereas 8 negative control cows remained seronegative (P < 0.001). Offspring were examined using serology, histology, immunohistochemistry, parasite isolation, and polymerase chain reaction (PCR). Six offspring were infected and 1 of them was aborted. The aborted fetus had typical lesions and positive immunohistochemistry and PCR for N. caninum. All 6 cows with infected offspring had continuously rising antibody titers, whereas 10 of 11 infected cows with uninfected offspring had falling titers after an early apex. The risk of transplacental transmission was increased by later exposure times during gestation and by the dose of oocysts (P < 0.01 for the 2 combined variables). The lowest dose of oocysts, when administered after the 160th day of gestation, caused transplacental infection in 1 of 2 animals. This study demonstrates that infection with N. caninum oocysts can cause transplacental transmission and abortion in cattle.     

Effect of neosporosis on productive and reproductive performance of dairy cattle in Costa Rica

A cross-sectional study was conducted to assess the effect of neosporosis on productive and reproductive parameters in dairy cows. Cows (n=2743) from 94 farms located in the most important dairy areas in Costa Rica were used in the study. The size of the herds ranged from 32 to 379 females (mean=110, median=125). An indirect ELISA was used to determine the serostatus of the cows towards Neospora caninum. The effect of neosporosis on milk production was analysed by a mixed linear model. In addition, the effects on calving interval (days) and calving to conception interval (days) were analysed by survival analysis. The risk of abortion in relation to N. caninum serostatus was assessed by logistic regression, with herd as a random effect. Overall, 1185 of 2743 cows (43.3%) were seropositive for Neospora. Eighty-nine of 94 (94.7%) farms were classified as Neospora-seropositive. It was estimated that cows seronegative to Neospora produced an additional 84.7L of milk (P=0.6). Serostatus did not have a significant effect on the length of the calving interval in the Cox proportional hazard survival analysis (Hazard ratio=1.2, 95% CI: 0.9, 1.4). The logistic regression model had a weak positive association between serostatus and abortion (OR 1.7, 95% CI: 0.8, 3.9), but did not show a strong association between serostatus and the number of services per conception (OR=0.95, 95% CI: 0.7, 1.3). In conclusion, there were no significant effects of Neospora serostatus on production and reproductive performance in this study.     

Abortion risk in progeny of cows after a Neospora caninum epidemic

A study was done of the descendants of cows from 4 dairy herds in which there had been N. caninum abortion outbreaks. Precolostral antibodies to N. caninum were demonstrated in 34 of 50 (68%) F1 calves and in 14 of 17 (82%) F2 calves from cows that aborted during the outbreaks. In 214 F1 progeny, N. caninum seroprevalence was nearly 50%, and there was a significant association between serostatus of the offspring and serostatus of dams. These observations indicated that congenital infection was an important mode of transmission after abortion outbreaks in these herds. A total of 52 abortions was recorded in 293 pregnancies of F1 progeny cows (1 to 3 pregnancies per animal). It was found that seropositive F1 cows had a three-fold increased abortion risk compared with seronegative F1 cows. In 2 of 10 abortions in seronegative cows evidence for N. caninum infection was found, suggesting that a low level of postnatal infection may also have occurred. It is concluded that N. caninum-infected calves should not be used as replacement stock, to decrease the future risk of abortion in dairy herds.     

Seroprevalence of Neospora caninum and Brucella abortus in dairy cattle herds with high abortion rates

The protozoan Neospora caninum and the bacterium Brucella abortus are well-recognized causes of abortion in dairy cattle. Serum samples (n = 240) from aborting (n = 141) and at-risk (n = 99) animals from 5 herds with high abortion rates in Punjab Province, Pakistan, were tested for antibodies to N. caninum using monoclonal antibody-based ELISA and for antibodies to B. abortus using the serum agglutination test. Antibodies to N. caninum and B. abortus were detected in 105 (43.8%) and 135 (56.3%) cattle, respectively. Prevalences of antibodies to N. caninum and B. abortus were higher in aborting cows (46.8% and 76.6%, P < 0.05) than in animals at risk (39.4% and 27.3%, P > 0.05). Sixty-six animals (27.5%) were seropositive to both N. caninum and B. abortus , and results showed no significant difference (P > 0.05) with respect to geographical district, breed, and age. This is the first report of N. caninum infection among dairy cattle herds in Pakistan.     

Serological diagnosis of neosporosis in a herd of dairy cattle in southern Brazil.

Neospora caninum-specific antibodies were detected in 60 of 172 (34.8%) dairy cattle by enzyme-linked immunosorbent assay (ELISA) in a herd from Parana State, Brazil. The seropositive animals included 47 of 126 (37.3%) adult cows, 7 of 29 (24%) heifers (1-2 yr), 4 of 15 (27%) heifers (5 mo-1 yr), and 2 precolostral samples. Data collected over a 9-yr follow-up period revealed that the proportion of pregnancies ending in abortion was 20% (31/154) among ELISA seropositive cows and 8% (15/193) among seronegative cows. The farm recorded 46 abortions, of which 31 (67.3%) were from seropositive cows. All sera positive by ELISA (n = 60) and sera from cows (n = 11) that were ELISA-negative but that had aborted were tested by the indirect fluorescent antibody test (IFAT) at dilutions from 1:25 to 1:200. All sera from ELISA-positive cows (n = 47) had an IFAT titer of 1:25:35 (74%) of these sera were also seropositive at a dilution of 1:200 (IFAT). Cows seropositive by ELISA had a 4-fold increased risk of having aborted at least once, compared to ELISA-seronegative cows. This association was statistically significant (P = 0.0016). The attributable fraction for this association indicated that approximately 76% of the risk for a cow having a history of abortion was attributable to seroconversion to N. caninum.     

Canine and bovine Neospora caninum control sera examined for cross-reactivity using Neospora caninum and Neospora hughesi indirect fluorescent antibody tests

Neospora caninum is a well known protozoan parasite of domestic and wild animals. Neospora hughesi is a closely related protozoan with an unknown life cycle, host range, and infection prevalence. Many serologic surveys of N. caninum have been performed without consideration of potential cross-reactions with N. hughesi, which could confound results. The aim of this study was to investigate whether postexposure sera from animals experimentally infected with N. caninum exhibit significant reactivity differences when tested using N. caninum and N. hughesi Immunofluorescent Antibody Tests (IFAT). Pre- and postinfection serum samples from 10 dogs, 20 calves, and 17 cows were tested by dual IFATs. All pre-exposure samples for N. caninum tested seronegative for both organisms. All postexposure samples that were seropositive for N. caninum were also positive for N. hughesi, although N. hughesi antibody titers were usually 1 dilution lower (P < 0.02). Serologic surveys for N. caninum may be confounded by cross-reacting titers with N. hughesi, but true positive N. caninum antibody titers are greater than, or equal to, cross-reacting N. hughesi antibody titers.     

Significance of Neospora caninum in British dairy cattle determined by estimation of seroprevalence in normally calving cattle and aborting cattle

A case control study was conducted to evaluate the significance of Neospora caninum infections in cattle in England and Wales. The prevalence of N. caninum in normally calving cattle (the control group; n = 418) and aborting cattle (n = 633) was estimated using a commercial antibody-detection ELISA. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and Leptospira hardjo were also obtained by serology. The prevalence of N. caninum was significantly higher (P < 0.0001) in the aborting group (18%; 95% confidence interval: 15%, 21%) than in the control group (6%; 95% confidence interval: 4%, 8%); the latter is the first estimate, to date, of the national seroprevalence of N. caninum in dairy cattle in England and Wales. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and L. hardjo were not found to be higher in the aborting cattle than in the control group. With N. caninum, a strong association between seropositivity and abortion was found, with seropositive cows being 3.5-times more likely to abort than seronegative cows (odds ratio = 3.49; 95% confidence interval: 2.16, 5.69). Furthermore, 12.5% of abortions in dairy cattle in England and Wales may be attributable to N. caninum, as indicated by estimation of the population aetiological fraction.     

Evidence of post-natal transmission of Neospora caninum in Dutch dairy herds

Eighteen dairy herds with neosporosis-associated abortions were analysed for antibodies against Neospora caninum. Blood samples of all cows, heifers and calves were collected on the same day for each farm. A total of 2430 heads of cattle were examined. For each herd, the seropositive and seronegative animals were plotted against month of birth. Analysis of seroprevalence in relation to age showed an equal distribution of seropositives in all age-groups in 10 herds. In contrast, in eight herds an age-group could be identified which had a significantly higher seroprevalence than the other animals in the herd. Most seropositive animals in the high seroprevalence age-groups had either seronegative dams or seronegative offspring, whereas there was a strong relationship between the serostatus of dams and offspring in the other animals in the herd. Aborting animals were mainly part of the high seroprevalence age-group. These findings strongly indicate a post-natal infection of the animals in the high seroprevalence age-groups, probably due to a point source exposure to N. caninum.     

Neospora caninum infections in bovine foetuses and dairy cows with abortions in Argentina

Antibodies to Neospora caninum were measured in bovine foetuses, dairy cows and beef cows in Argentina using the IFAT, the N. caninum agglutination test, and the recombinant NCDG1 and NCDG2 ELISA. Serum antibodies (IFAT titre 1:80) were found in 20 of 82 (24.4%) dairy cow foetuses and one of 22 (4.5%) beef cow foetuses. Microscopic lesions suggestive of neosporosis were seen in brains of seven of eight foetuses with IFAT titres of 1:80. Antibodies (IFAT) were found in 122 of 189 (64.5%) dairy cows that aborted. Serum antibody titres (IFAT) of 189 dairy cows that aborted were: < 1:25 (67 cows), 1:25 (four cows), 1:50 (16 cows), 1:200 (seven cows), 1:> or = 800 (95 cows). Of the 87 sera with IFAT titres of < or = 1:50, 57 had no antibodies in 1:40 dilution and 30 had titres of 1:40 in the N. caninum agglutination test. Thus, sera from at least 56 dairy cows which had aborted were seronegative both in the N. caninum agglutination test and the IFAT. The distribution of positive and negative sera was similar when measured by ELISA, except that, depending on cut-off titre, the ELISA indicated a greater number of seropositive cows that were negative by the IFAT and N. caninum agglutination test. These results suggest that transplacental transmission of N. caninum in dairy cows in Argentina is frequent.     

Dynamics of heat shock protein 70 concentrations in peripheral blood lymphocyte lysates during pregnancy in lactating Holstein-Friesian cows

The aim of this study was to characterize the dynamics of the concentrations of heat shock protein 70 kDa (HSP70) in peripheral blood lymphocytes of lactating Holstein-Friesian dairy cows (Bos taurus) during pregnancy. The detection of pregnancy was carried out and blood samples collected on Days 40, 90, 120, 150, 180, and 210 of gestation from 46 cows (11 primiparous and 35 pluriparous, 34 seropositive and 12 seronegative to Neospora caninum). Peripheral blood lymphocytes were isolated by density gradient centrifugation. Serologic analysis of Neospora infection and determinations of HSP70 concentrations in lymphocyte lysates were carried out using commercial enzyme-linked immunosorbent assay kits. Climate variables were monitored using on-farm data loggers. Heat shock protein 70 concentrations increased in lymphocytes as gestation progressed, particularly in primiparous cows, with no effect from Neospora infection, climate variables, milk production, semen-providing bull, or outcome of gestation (singletons or twins). Our results show that HSP70 concentrations increased in lymphocytes as gestation progressed and were not affected by stressful factors, such as milk production, heat stress, chronic infection (neosporosis), or twin pregnancies.     

Seroprevalence of Neospora caninum antibodies in dogs in India

Neospora caninum is one of most important causes of abortion in cattle worldwide, and dogs are an important risk factor for N. caninum infection in cattle. Antibodies to N. caninum were determined in 184 (126 rural, 58 urban) dogs from the Punjab State, India, using commercial monoclonal antibody-based competitive ELISA and found in 16.8% of the animals. The prevalence of N. caninum antibodies was significantly higher in rural dogs (21.4%, 27 of 126) than city dogs (6.9%, 4 of 58). To our knowledge this is the first report of N. caninum infection in canines from India.     

Serological survey of Neospora caninum infection in cattle herds from Western Romania

Serum samples from 376 randomly selected adult cattle, from 25 farms located in 3 counties (Arad, Bihor, and Timi?) from western Romania, were sampled for Neospora caninum antibodies using a commercial ELISA-kit. Seroprevalence values and risk factors for neosporosis (cow age, breed, herd size, farming system, previous abortion, and number of farm dogs) were examined using a generalized linear mixed model with a binomial distribution. Overall, the seroprevalence of N. caninum was 27.7% (104/376) with a prevalence of 27.9% (24/86) in Arad, 26.9% (25/93) in Bihor, and 27.9% (55/197) in Timi?. Of 25 cattle herds, 23 were seropositive with a prevalence ranging from 10.0 to 52.2%. No correlation was found between N. caninum seropositivity and age, breed, herd size, breeding system, and previous abortion. The number of farm dogs was the only factor (P(Wald) = 0.03) positively associated with seroprevalence in cows and can be considered the risk factor in the acquiring of infection. The present work is the first regarding serological evidence of N. caninum infection in cattle from western Romania.     

Prevention of vertical transmission of Neospora caninum in C57BL/6 mice vaccinated with Brucella abortus strain RB51 expressing N. caninum protective antigens

Bovine abortions caused by the apicomplexan parasite Neospora caninum have been responsible for severe economic losses to the cattle industry. Infected cows either experience abortion or transmit the parasite transplacentally at a rate of up to 95%. Neospora caninum vaccines that can prevent vertical transmission and ensure disruption in the life cycle of the parasite greatly aid in the management of neosporosis in the cattle industry. Brucella abortus strain RB51, a commercially available vaccine for bovine brucellosis, can also be used as a vector to express plasmid-encoded proteins from other pathogens. Neospora caninum protective antigens MIC1, MIC3, GRA2, GRA6 and SRS2 were expressed in strain RB51. Female C57BL/6 mice were vaccinated with a recombinant strain RB51 expressing N. caninum antigen or irradiated tachyzoites, boosted 4 weeks later and then bred. Antigen-specific IgG, IFN-gamma and IL-10 were detected in vaccinated pregnant mice. Vaccinated mice were challenged with 5 x 10(6)N. caninum tachyzoites between days 11-13 of pregnancy. Brain tissue was collected from pups 3 weeks after birth and examined for the presence of N. caninum by real-time PCR. The RB51-MIC3, RB51-GRA6, irradiated tachyzoite vaccine, pooled strain RB51-Neospora vaccine, RB51-MIC1 and RB51-SRS2 vaccines elicited approximately 6-38% protection against vertical transmission. However, the differences in parasite burden in brain tissue of pups from the control and vaccinated groups were highly significant for all groups. Thus, B. abortus strain RB51 expressing the specific N. caninum antigens induced substantial protection against vertical transmission of N. caninum in mice.     

Detection of Neospora caninum in the semen and blood of naturally infected bulls

A prospective study was designed to investigate the presence of Neospora caninum in semen and blood of eight bulls seropositive to N. caninum using nested-PCR procedures. Positive semen and blood samples were bioassayed in a BALB/c nu/nu mouse model. Specific anti-N. caninum serological and interferon-gamma (IFN-gamma) responses were also studied. In parallel, five seronegative bulls acted as non-infected controls. All bulls were located in a collaborating AI centre and monitored for 22 weeks. Six of eight seropositive bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. In all positive semen samples, we consistently found Neospora-DNA in the cell fraction and not in seminal plasma. Parasite load, as determined by a real-time PCR in nested-PCR positive semen samples, ranged from 1 to 10 parasites/ml. We found no association between the presence of N. caninum DNA in semen and blood. N. caninum could not be detected in the BALB/c nu/nu mice inoculated with PCR-positive semen or blood samples. Specific IgG antibody levels in seropositive bulls fluctuated over time, at times falling below cut-off level. The response was predominantly IgG2, with significant differences compared to control bulls (P < 0.05). The overall mean specific IFN-gamma response in seropositive bulls was also higher than those observed in the control group (P < 0.05), although extensive variation in individual responses was observed among bulls and over time. No significant association was found between bulls showing Neospora DNA in semen, blood, or both, and specific IgG, IgG1, IgG2, IgM and IgA levels or IFN-gamma response. This study is the first to report the presence of Neospora DNA in semen and blood of naturally-infected bulls. Our observations indicate intermittent presence of N. caninum in blood and semen and shedding in semen in low numbers.     

Occasional detection of Neospora caninum DNA in frozen extended semen from naturally infected bulls

Recently, the presence of Neospora caninum DNA in semen from naturally infected bulls was reported. In the present work, the presence and quantification of N. caninum by PCR techniques in frozen extended semen straws from naturally infected bulls was investigated. A total of 20 seropositive and five seronegative bulls raised for reproductive purposes in an AI centre were used. Ten extended semen straws from each bull obtained at different time-points during the previous 2 years were selected for Neospora testing. Eight of the seropositive bulls (40%) studied showed at least one positive straw to N. caninum DNA and 14 of their 180 semen straws examined (7.8%) were found to be positive. In all positive samples, N. caninum DNA was consistently detected in the cell fraction and not in the seminal plasma. However, the parasite number in each positive straw was under the detection level of real-time PCR. In parallel, 10 semen straws from each of the five seronegative bulls were also analyzed by the nested-PCR and no N. caninum DNA products were obtained. In order to check the consistent presence of N. caninum in a positive semen batch, three additional semen straws from the same batch of each positive straw from three seropositive bulls were analyzed but N. caninum DNA was only detected in one straw from one bull. In conclusion, we report the sporadic detection of N. caninum DNA in semen straws of naturally infected bulls but the low frequency of contaminated semen straws and the low parasite load observed indicate a minor chance of bovine neosporosis transmission by AI.     

Review of Neospora caninum and neosporosis in animals

Neospora caninum is a coccidian parasite of animals. It is a major pathogen for cattle and dogs and it occasionally causes clinical infections in horses, goats, sheep, and deer. Domestic dogs are the only known definitive hosts for N. caninum. It is one of the most efficiently transmitted parasite of cattle and up to 90% of cattle in some herds are infected. Transplacental transmission is considered the major route of transmission of N. caninum in cattle. Neospora caninum is a major cause of abortion in cattle in many countries. To elicit protective immunity against abortion in cows that already harbor a latent infection is a major problem. This paper reviews information on biology, diagnosis, epidemiology and control of neosporosis in animals.