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1.
An outbreak of Neospora caninum-associated abortion occurred in a South Carolina dairy wherein greater than 10% of the herd aborted over a 4-month period. Of the total number of cows at mid-late gestation, nearly 40% (28/71) aborted while the remaining 60% (43/71) gave birth to normal calves. Immunohistochemical examination of brain tissue from a subset of aborted fetuses confirmed N. caninum as the causative agent of abortion in these animals. A variety of serological assays, including indirect fluorescence antibody test (IFAT), recombinant enzyme-linked immunosorbent assay (rELISA), ISCOM-ELISA, avidity ELISA, and Neospora agglutination test (NAT), were used to evaluate sera collected during the outbreak from 240 cows for antibodies to N. caninum. IFAT and ISCOM-ELISA testing showed that nearly 80% of the dairy cows had antibodies to N. caninum. NAT and rELISA had similar levels of seropositivity relative to IFAT and ISCOM-ELISA, but the percentage of positive sera was dependent on the cut-off value chosen. As indicated by kappa coefficient statistical analysis, ISCOM-ELISA and IFAT exhibited the highest level of agreement in identifying N. caninum-positive and -negative cows. A decrease in the percentage of seropositive cows as determined by ISCOM-ELISA and IFAT with increasing cow age was noted. However, no significant difference was observed between cow age and abortion status. In addition to these tests, an avidity ELISA was performed on all sera with high (> or =0.4) ISCOM-ELISA readings. Avidity index (AI) increased with time post-abortion suggesting that most abortions were due to recent N. caninum infection. Of the cows at risk for abortion, the mean serological AI of aborting cows was significantly lower (P<0.05) than mean serological AI of non-aborting cows.  相似文献   

2.
OBJECTIVE: To investigate the seroprevalence of Neospora caninum infection in a commercial dairy cattle herd, 15 months after detection of an abortion outbreak. PROCEDURE: Sera from the whole herd (n = 266) were examined for N caninum antibodies by indirect fluorescent antibody test (IFAT) and immunoblot analysis. Herd records were reviewed to collate serological results with abortion history, proximity to calving, and pedigree data. RESULTS: The seroprevalence of N caninum infection was 24% (63/266) for IFAT titre > or = 160, 29% (78/266) for immunoblot positive (+ve), and 31% (82/266) for IFAT > or = 160 and/or immunoblot +ve; 94% (59/63) of animals with IFAT > or = 160 were immunoblot +ve. The association between seropositivity (IFAT > or = 160 and/or immunoblot +ve) and history of abortion was highly significant (P < 0.001); the seroprevalence was 86% (18/21) in aborting cows, compared with 30% (50/164) in non-aborting animals. The abortion rate for seropositive cows was 26% (18/68) compared with 3% (3/117) for seronegative animals. IFAT titres of infected cows were higher within 2 months of calving than at other times (P < 0.001). The association between seropositivity in dams and daughters was highly significant (P = 0.009). CONCLUSIONS: The abortions were associated with N caninum infection and there was evidence of reactivation of latent infection close to calving and congenital transmission of infection. Immunodominant antigens identified by immunoblots may prove useful for improved diagnostic tests.  相似文献   

3.
A serological survey for antibodies against Neospora caninum in aborting cattle was carried out in the Czech Republic. Serum samples from 463 aborting dairy cows originated from 137 farms from different parts of the Czech Republic were tested for presence of N. caninum antibodies by use of an enzyme-linked immunosorbent assay (ELISA) and an indirect fluorescent antibody test (IFAT). Antibodies (> or = 1:640) to N. caninum were found in 18 (3.9%) of 463 aborting cows. Farm prevalence in aborting cows was 12.4% (17/137). The antibody titres of cows were 1:200 (9 cows), 1:640 (7 cows), 1:1280 (3 cows), 1:2560 (3 cows), 1:5120 (3 cows), 1:10,240 (2 cows) and 1:20,480 (0 cow). A case-control study was conducted to estimate the association of N. caninum infection and abortion. For this 407 serum samples were collected from cows on five dairy farms with repeated occurrence of endemic and sporadic abortion of unidentified etiology. These samples were obtained from aborting cattle (n=44) and normally calving cattle (control group; n=363) and tested for N. caninum antibodies by an immunofluorescent antibody test (IFAT). Overall, 3.19% (13/407) of cows sampled had positive N. caninum fluorescence with a cut-off titre of 1:200. The prevalence of N. caninum was significantly higher (P<0.05) in the aborting group (13.64%; 95% confidence interval (CI): 5.2, 27.4) than in the control group (1.93%; 95% CI: 0.8, 3.9). A strong association between seropositivity and abortion was found, with seropositive cows being eight times more likely to abort than seronegative cows (odds ratio=8; 95% CI: 2.6, 25.1). This first report on the serological prevalence of N. caninum in cows in the Czech Republic verified a strong association between N. caninum infection and abortions in five dairy farms. Thus, the neosporosis should be considered in differential diagnosis of bovine abortion.  相似文献   

4.
Prevalence of antibodies to Neospora caninum was determined in a cross-sectional consensus survey of 1029 bovines in a dairy herd with endemic Neospora-induced abortion. Sera were screened by indirect fluorescent antibody test (IFAT). The prevalence of N. caninum antibody in the IFAT was 17.9% in 107 neonates, 26.2% in 233 yearling heifers and steers, 39.07% in 218 mature heifers, and 26.9% in 465 milking cows. Serologic reactivity was associated with production grouping on the farm with the greatest risk of serologic reactivity appearing in the yearling and mature heifers. There was an increasing risk of serologic reactivity with increasing age only in the parity one and greater animals in the herd. Castrated males were at half the risk of similarly aged females of possessing antibodies to N. caninum. There was no clear relationship between the serologic status of dams and offspring.  相似文献   

5.
OBJECTIVE: To examine the relationship between exposure to Neospora caninum and abortion in dairy cows during their first, second, third, and fourth or later lactations and to establish the main mode of transmission in female calves from birth until their first pregnancy was terminated by abortion or parturition. DESIGN: Prospective observational study. ANIMALS: 460 Holstein cows and 79 female calves. PROCEDURE: Cows were classified as seropositive or seronegative to N caninum within 7 days after calving; incidence of abortion was compared between groups during different lactations. Blood samples were collected from female calves before ingestion of colostrum and every 6 months until their first pregnancy was terminated by abortion or parturition; number of seropositive calves was compared between seropositive and seronegative dams. RESULTS: During the first pregnancy of their second lactation, risk of abortion for seropositive cows was 2.8 times that of seronegative cows. Among 10 calves born to seropositive cows, 4 were classified as seropositive at birth and thereafter. Among 69 calves born to seronegative cows, all were classified as seronegative at birth; 67 calves remained seronegative thereafter. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to N caninum alone was not significantly associated with abortion in cows during the first, third, and fourth or later lactations. Seropositive cows that have aborted previously may have subsequent abortions attributable to N caninum. Congenital infection was the main mode of N caninum transmission in a cohort of female calves.  相似文献   

6.
A dairy herd experienced an abortion epidemic during which 43 per cent of the cows at risk aborted. Neospora caninum infection was demonstrated in four of six fetuses suitable for examination and the group of at-risk cows that aborted had significantly higher N. caninum antibody concentrations than the at-risk cows that delivered a live calf at term (P<0.001). The antibody concentrations in the cow herd were significantly higher than in the youngstock (P<0.001), and the concentrations in the youngstock increased significantly (P<0.001) with age. When seven months to a year old, the calves born at term to the at-risk cows had significantly higher (P=0.007) antibody concentrations than age-matched calves born before the epidemic. At the time of the epidemic, there was a significant increase in the antibody levels of the herd that was not consistent with vertical infection alone, indicating that there appeared to have been a sudden large increase in the incidence of horizontal postnatal transmission of N. caninum to the cow herd, or to the surviving offspring of the at-risk cows, or to both of these groups.  相似文献   

7.
AIM: To monitor pregnancy in a group of rising 2-year-old dairy heifers on a farm on which abortion due to Neospora caninum was known to occur in previous years. METHODS: A prospective cohort study group of 164 rising 2-year-old heifers was pregnancy-tested and blood-sampled at 4-5-week intervals throughout gestation. Sera were tested for antibodies to N. caninum at 3-4-month intervals, using an enzyme-linked immunosorbent assay (ELISA). When loss of pregnancy was detected, an N. caninum indirect fluorescent antibody test (IFAT) was conducted retrospectively on stored sera collected the month before abortion, the month abortion was detected, and for the following 2 months, from heifers that aborted. All fetal and placental material detected following abortion was subjected to gross post-mortem and histopathological examination. RESULTS: Eleven of 18 (61%) heifers that were seropositive and 4/146 (3%) heifers that were seronegative to N. caninum by ELISA, aborted. The relative risk for abortion among ELISA-positive heifers was 23.6. Abortion occurred predominantly between Days 120 and 152 gestation among the ELISA-positive heifers and throughout gestation among the ELISA-negative heifers. IFAT titres rose around the time of abortion in most of the heifers that were previously seropositive by ELISA, but dropped rapidly again in post-abortion samples. IFAT titres among 4/6 ELISA-positive heifers that did not abort increased, but later in gestation than the time other heifers aborted. IFAT titres remained negative in heifers that aborted that were ELISA negative. CONCLUSIONS: Heifers that were seropositive to N. caninum by ELISA had a much greater risk of abortion than seronegative heifers. Most seropositive heifers showed evidence of a reactivation of infection during pregnancy. High (> or =1:2,000) N. caninum IFAT titres also occurred in non-aborting heifers. CLINICAL RELEVANCE: Culling of replacement heifers seropositive to N. caninum may be a cost-effective strategy for minimising risk of abortion. Pregnancy testing heifers before 5 months gestation may overestimate the number that calve in N. caninum-infected herds, but would assist in documenting the occurrence of abortion. Reliance on a high (>1:2,000) IFAT titre to rule-in N. caninum as a cause of abortion is likely to produce false-positive results.  相似文献   

8.
A Neospora caninum IgG avidity ELISA was carried out on the basis of a somatic N. caninum tachyzoite antigen. The test was validated using experimentally infected calves, where a clear maturation of the IgG avidity over time could be demonstrated. At a maximum of 82 days after infection (d.p.i.), all animals showed antibody avidities ranging above 35%, and respective sera were thus defined as highly avid.Sera of 103 naturally infected seropositive cows with abortion (N. caninum association was provided by a N. caninum PCR-positivity of the fetus in 40 cases) and 139 seropositive animals without abortion history were concurrently examined. Significantly lower avidities were observed in aborting cows when compared to animals without abortion problems (P<0.01). While the avidity of sera collected before abortion remained practically constant until abortion, a significant increase of avidity could be observed in samples collected weeks to months after abortion (P<0.01).The avidities of non-aborting animals from farms with or without abortion problems did not differ significantly with time and were mainly located in the high avidity area. These data indicate that low avidities are not necessarily linked to recent N. caninum infection but can also be an indicator for increased abortion risk in cattle.  相似文献   

9.
There is an evidence that the epidemiology of neosporosis differs in dairy and beef cattle, such that beef cattle carry a lower risk of abortion. The aim of the present study was to establish whether artificial insemination using semen from beef bulls could reduce the risk of abortion in dairy cows seropositive for the Neospora caninum parasite. Our study was based on yearly serological screening for neosporosis and on the confirmation of Neospora infection in aborted fetuses in two high-producing dairy herds with a mean 28% seroprevalence of N. caninum antibodies. The study population comprised of 273 pregnancies in seropositive animals: 156 pregnancies monitored after insemination using Holstein-Friesian semen and 117 after insemination using beef bull semen. Abortion rates for these animals were 28.2% (77 of 273), 34.6% (54 of 156) and 19.7% (23 of 117). Logistic regression analysis indicated no significant effects of lactation number and previous abortion on the abortion rate. Based on the odds ratio, a 1-unit increase in the Neospora antibody titre yielded a 1.01-fold increase in the abortion rate. The likelihood of abortion was two times higher for cows in one of the two herds and 2.8 times lower (one of 0.36) for pregnant cows inseminated with beef bull semen rather than Holstein-Friesian semen. Our results indicate that the use of beef bull semen can reduce the risk of abortion in dairy cows, and suggest that annual screening for neosporosis, specifically the antibody titre to the protozoan, could be an useful predictor of abortion risk in reproductive health programmes.  相似文献   

10.
A clinical trial was undertaken to assess the efficacy of Bovilis(?) Neoguard, a killed Neospora caninum tachyzoite vaccine on 5 commercial dairy farms in New Zealand with a history of Neospora-associated abortion. Cattle were enrolled in the trial at 30-60 days of gestation and randomly allocated to treatment or control groups. Treatment consisted of 5 mL doses of Bovilis Neoguard administered subcutaneously at enrolment then 4 weeks later. Isotonic saline was administered to the control group. Of 2246 cattle enrolled in the trial, 10.7% of cows and 12.6% of heifers were seropositive to N. caninum. Sampling of a randomly selected proportion of enrolled animals 6 weeks after the second treatment showed that 188/232 (81.0%) vaccinated with Bovilis(?) Neoguard had seroconverted, while 11/130 (8.5%) cows and 10/36 (27.8%) heifers in the control group had seroconverted. Forty-eight vaccinated and 63 control animals aborted. On one farm 12.5% of control animals and 6.1% of vaccinated animals aborted (vaccine efficacy 0.61; p=0.03). On another farm with a high level of abortion 8.4% of control animals and 8.7% of vaccinates aborted. On the remaining 3 farms fewer abortions occurred than expected. A modified Poisson regression approach was used to calculate relative risks for abortion and vertical transmission. Overall vaccine efficacy was 0.25 (p=0.12). Heifer replacement calves from the animals enrolled in the trial were sampled for antibodies to N. caninum at 6-9 months of age. Fourteen of 17 calves from vaccinated, seropositive cows were seropositive as were 13/23 calves from seropositive cows in the control group. The interaction between dam serostatus and treatment group was significant (p=0.05) with vaccination increasing the risk of vertical transmission. It was concluded that vaccination after conception prevented 61% abortions in one of five herds and that vaccination may have increased the risk of early embryonic death.  相似文献   

11.
In vitro isolation and characterization of bovine Neospora caninum in Korea   总被引：5，自引：0，他引：5  
The brains of nine aborted bovine fetuses and two newborn calves born from dams suspected to be infected with Neospora caninum were homogenized and inoculated into Vero cells. All fetuses and calves were from cows determined as seropositive to N. caninum by an IFA test. Sera and thoracic fluids of all fetuses and calves also revealed high antibody titer to N. caninum by IFAT ranging from 1:800 to 1:3200. N. caninum was isolated from the brains of one aborted fetus and one newborn calf when the brain homogenates were grown continuously in Vero cell culture. N. caninum tachyzoites, giemsa-positive, were first observed on Days 45 and 56 postinoculation in the newborn calf and the aborted fetus, respectively. The isolates (KBA-1 and KBA-2) were morphologically and ultrastructurally similar to previously published Neospora isolates. The isolated parasites were confirmed as N. caninum by means of the antigenic reactivities, immunostaining, PCR and southern blotting, and electron microscopy.  相似文献   

12.
AIM: To describe the kinetics of serological titres after an abortion outbreak in April-May 1995 due to Neospora caninum affected 17 dairy cows in a herd of 320. METHODS: Thirty-five cows, that had either aborted, carried mummified calves, were not pregnant or calved normally were: bled several times at regular intervals and the sera tested for Neospora antibodies in the indirect fluorescence antibody test (IFAT). RESULTS: Maximal IFAT titres of up to 1:4000 occurred within 6 weeks of the abortion outbreak, decreased over the next 2 months to < or = 1:200 and remained at this level until the next scheduled bleed a further 2 months later. A rise in titres was subsequently observed in the cows that had aborted or were not pregnant (at the time of the abortions) or had carried mummified foetuses. Seroconversion was also observed in some of the control cows, which had, up until then, remained seronegative. A dog and cat in contact with the cows in the herd investigated were, however, negative in the IFAT. CONCLUSIONS: Maximal serological titres in Neospora abortions are observed within weeks of the abortion event and then quickly return to very low levels. Subsequently, a recrudescence of titres can be observed in infected cows during the next pregnancy, without it being associated with repeat abortions.  相似文献   

13.
Postnatal neosporosis in dairy cattle in northeast Thailand   总被引：4，自引：0，他引：4  
A total of 83 dairy cows in Loei Province (Muang) and Nong Bua Lamphu (NBL) Province, northeast Thailand were sampled three times within 6 months in 1998 and their sera were examined for antibodies to Neospora caninum at a dilution of 1:100 in the indirect fluorescent antibody test (IFAT). In Muang the seroprevalence of N. caninum was 37.5% (June), 60% (August), and 62.5% (November). In NBL the prevalence was 50% (August) and 70% (November). In both areas abortions were observed between 1 and 3 months after the introduction of these cattle from another area. Nine of 14 and seven of 17 calves were descendants of seropositive dams, of which only two calves from Muang and two calves from NBL were positive for N. caninum antibodies. These findings suggest postnatal N. caninum transmission.  相似文献   

14.
The possible direct relationship between climate variations and abortion in Neospora caninum-infected cows has not been studied. The objective of this study was to determine whether climate changes could be a risk factor for abortion in N. caninum-infected cows, and was based on yearly serological screening for neosporosis and on the confirmation of N. caninum infection on aborted fetuses in two high-producing dairy herds with a mean 27% seroprevalence of N. caninum antibodies. The final population study was comprised of 357 pregnancies in seropositive animals. Logistic regression analysis indicated no significant effects of herd, N. caninum antibody titre, climate variables during the first and third trimesters of gestation, mean and maximum temperature-humidity index values during the second trimester of gestation, and previous abortion on the abortion rate. Based on the odds ratio, a 1-unit increase in lactation number yielded a 0.85-fold decrease in the abortion rate. The likelihood of abortion was 1.9 times (1/0.54) lower for pregnant cows inseminated with beef bull semen compared with Holstein-Friesian bull semen. The likelihood of abortion decreased significant and progressively by factors of 0.5, 0.41 and 0.3 for the respective classes 40-49, 30-39 and <30 rainfall mm during the second trimester of gestation (using the class >or=60 rainfall mm as reference). As a general conclusion, it seems that increased rainfall in a dry environment can compromise the success of gestation in N. caninum-infected cows. Attempts should therefore be made to reduce environment effects during the second trimester of gestation, a period in which the immune response of cows is diminished.  相似文献   

15.
Progesterone has been reported to reduce Th1 responses during pregnancy. Thus, given that an excessive Th1 response could lead to abortion in Neospora-infected dairy cows, we hypothesized a reduction in abortion risk following progesterone supplementation during the mid-gestation period in these animals. Seropositive animals were assigned on day 120 of gestation to a Control (n=33) or Treatment (n=34) group. Treatment consisted of progesterone supplementation by fitting a progesterone releasing intravaginal device containing 1.55g of progesterone for 28 days. Mean Neospora caninum antibody titres tested by ELISA on days 40, 90 and 120 of gestation were used to classify the cows as showing high (> or =30 units) or low (<30 units) titration. Abortion rate showed a significant increase (P<0.01) in the Treatment group (35%) compared to the Control (9%). Using logistic regression procedures, there was a significant (P<0.0001) interaction between progesterone treatment and antibody titration. Progesterone-treated cows with a high antibody titre showed a likelihood of abortion 14.3 times higher than those not treated, while in cows with low antibody titres, exogenous progesterone had not effect. Our results do not support our starting hypothesis and suggest that progesterone supplementation in cows with high N. caninum antibody titres increases the risk of abortion possibly by affecting cell-mediated immune responses.  相似文献   

16.
This present study, was designed to establish whether Neospora caninum infection affects the fertility of high-producing dairy cows, and was based on yearly serological screening for neosporosis and on the confirmation of N. caninum infection in aborted foetuses. Assessment was made of 7518 artificial inseminations (AI) (applied to parous cows) performed in three herds. Of these inseminations, 2540 (33.8%) resulted in pregnancy; 34% of which corresponded to seronegative cows (2226 of 6556 AI performed in seronegative cows) and 32.6% to seropositive animals (314 of 962). Abortion occurred in 97 (30.1%) of the 314 pregnancies recorded in dams seropositive for N. caninum, while only 93 (4.2%) of the 2226 pregnancies in seronegative animals ended in abortion. Logistic regression analysis indicated no significant effects of N. caninum antibody titre, days in milk and milk production at insemination on fertility. Factors found to affect fertility were herd, season of insemination, lactation and insemination number, semen-providing bull and AI technician. Our results indicate that N. caninum infection does not affect the fertility of high-producing dairy cows.  相似文献   

17.
The protozoan parasite Neospora caninum and bovine virus diarrhoea virus (BVDV) are recognized as important causes of bovine abortion and congenital disease worldwide. In this study, serological investigations were performed to estimate the prevalence of N. caninum infection in Swedish dairy cattle, to assess to what extent it may affect abortion rates, and to determine possible effects of coinfection with BVDV. The overall N. caninum seroprevalence in Swedish dairy cows was estimated at 2% (16/780), and the BVDV seroprevalence was 32% (249/780). Among aborting cows from herds with abortion problems, 7% (26/378) had antibodies to N. caninum and 42% (153/378) to BVDV. Seventeen of the N. caninum positive animals also had antibodies to BVDV. There was a statistically significant (P = 0.013) association between presence of antibodies to N. caninum and BVDV. In a case-control study comprising sera from cows in herds without recognized abortion problems, 6% (5/89) and 1% (1/89) of sera from aborting and non-aborting cows, respectively, had antibodies to N. caninum. Two of the N. caninum seropositive aborting cows also had antibodies to BVDV. These results confirm that N. caninum infection is associated with bovine abortion in Sweden and also indicate that there might be concurrent effects of N. caninum and BVDV. It is concluded that Swedish dairy cows have a low prevalence of N. caninum infection which is favourable in relation to possible future control programmes.  相似文献   

18.
The protozoa Neospora caninum is an important cause of bovine abortion world-wide. The objective of this survey was to determine the distribution pattern of infectious abortion in Southern Brazil with special reference to N. caninum infection. A total of 161 bovine aborted fetuses from 149 farms were analysed during a 1.5 year period. The cause of abortion was identified in 51.5% of cases. Overall, 23% (37/161) of the fetuses were considered to be infected with N. caninum. Bacterial infection accounted for 17.4% (28/161) of cases, fungal infection for 3.1% (5/161) of cases and viral aetiology for 1.8% (3/161). Six fetuses had concurrent infection with N. caninum and Leptospira spp. Data from 111 fetuses and the respective aborted cows were analysed to investigate the association between previous abortion and current N. caninum infection. The prevalence of N. caninum-infected fetuses from cows with and without a history of previous abortion was 44% (11/25) and 24.4% (21/86), respectively. Cows aborting a N. caninum-infected fetuses were 2.4 times more likely to have aborted previously than cows aborting for other reasons (95% CI of odds ratio=0.9-6.8, P=0.06).  相似文献   

19.
Forty-six aborted bovine fetuses submitted to the Faculty of Veterinary, Department of Clinical Pathology, Universidade Federal do Rio Grande do Sul, were examined histopathologically. Non-suppurative inflammation was observed mainly in the brain and heart of 22 fetuses. Brain lesions consisted primarily of mononuclear inflammatory cell infiltrates with occasional foci of necrosis. Protozoa that reacted with Neospora caninum antisera were seen in 18 of the 22 (81.8%) brain specimens from fetuses with encephalitis. Blood samples collected from 223 Holstein cows on five dairy herds were tested for N. caninum antibodies by an immunofluorescent antibody technique. These samples were obtained from aborting cattle and normally calving cattle (control group). Overall, 11.2% of cows sampled had N. caninum antibodies at a dilution of 1:200. Seroprevalence was higher (P = 0.0053) in aborting (23.3%) than in non-aborting cows (8.3%). Association between seropositivity to N. caninum and abortion was found, with seropositive cows being 3.3 times more likely to abort than seronegative cows (OR = 3.33; 95% CI: 1.38, 8.062). Additionally, N. caninum antibodies were detected in sera from seven cows that had aborted fetuses with lesions suggestive of protozoal infection. These results suggest that N. caninum is an important cause of abortion in dairy cattle in Rio Grande do Sul State, Brazil.  相似文献   

20.
In a dairy herd experiencing an abortion outbreak, 49% of the 119 cows were positive for Neospora caninum antibodies and the remaining 51% were seronegative. Using immunohistochemical analysis of foetal brain tissue, Neospora cysts and bradyzoite clusters were identified in two of the 15 aborted foetuses submitted for testing. Other agents that commonly cause abortions were not found. These results, coupled with neurological clinical symptoms in new-born calves, implicated N. caninum as the major cause of abortions in this dairy herd. This is the first report that associates N. caninum infection with bovine abortions in Portugal.  相似文献   

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