A long-term study of Neospora caninum infection in a Swedish dairy herd

A longitudinal study was performed in a Swedish dairy herd where Neospora caninum had been isolated from a stillborn calf. Starting in autumn 1994, blood samples from all female animals in the herd were collected once yearly until 1999. The sera were analysed for presence of IgG1 antibodies to N. caninum by the iscom ELISA, and by an avidity ELISA to establish the timing of infection. In addition, data on reproductive performance were compiled. During the study the percentage of seropositive female animals increased from 63% to 87%. In 1994 a large number of young animals tested seropositive although their dams were seronegative, indicating that a transmission of the parasite other than the vertical had recently occurred. Low avidity values supported this assumption. The annual abortion rate increased from a mean of 2% before the initiation of the study to 9% in 1994-1998. During the same time, as judged by the avidity data, a large proportion of the animals shifted from being recently to being chronically infected. The source of the external infection in the herd could not be identified.     

Evaluation of Mycobacterium avium subsp paratuberculosis infection of dairy cows attributable to infection status of the dam

OBJECTIVE: To estimate the extent to which infection with Mycobacterium avium subsp paratuberculosis (MAP) of cows in a large dairy was attributable to the infection status of their dams. DESIGN: Retrospective longitudinal study. ANIMALS: 625 dam-daughter pairs of Holstein cows. PROCEDURE: Serologic test results were compared between cows and their dams. Logistic regression was used to assess whether a cow's serologic status was associated with its dam's serologic status. Infection with MAP attributable to being born to a seropositive dam was estimated for individual cows and for the herd. RESULTS: Cows with seropositive dams were 6.6 times as likely to be seropositive, compared with cows of seronegative dams. For seropositive cows born to seropositive dams, 84.6% of seropositivity was attributable to being born to a seropositive dam and 15.4% to other exposures, including exposure as calves to flush water that contained feces of adult cattle. For the herd as a whole, the seropositive status in 34% of seropositive cows was attributable to being born to a seropositive dam. CONCLUSIONS AND CLINICAL RELEVANCE: For dairy herds that breed seropositive cows, subsequent transmission of MAP to their daughters, either congenitally or via exposure to feces and colostrum of the dam shortly after birth, can contribute substantially to maintaining prevalence of MAP in a herd. Removal of seropositive, clinically unaffected cows and their daughters would be necessary to reduce infection with MAP attributable to congenital or peri-parturient transmission from dam to daughter.     

Pleuropneumonia in swine caused by Haemophilus parahaemolyticus. A study of the epidemiology of the infection

Haemophilus parahaemolyticus infection was studied in a herd with continuous production, i.e., continuous introduction of stock to replace animals delivered for slaughter. None of 30 seronegative pigs contracted the infection when exposed to contact with two pigs that were seropositive after inoculation with H. Parahaemolyticus three weeks earlier. After aerosol infection had been applied in the building an acute outbreak with a morbidity rate of 100 per cent developed in less than 24 hours. Following recovery the majority of the 16 pigs present became seropositive, and when 30 seronegative pigs were introduced 7 weeks later, antibody response occurred in three of them. The persistence of H. parahaemolyticus in pigs that had been infected during the acute outbreak was confirmed at slaughter, in that the organism was re-isolated from the tonsils of 2 of these pigs. Most serum titres persisted for several months, but some animals showed just a transient antibody response.     

Serologic status of pseudorabies virus in growing-finishing pigs in quarantined herds

It has been reported that pseudorabies virus (PRV) stops spreading within growing-finishing sections of a large percentage of infected farrow-to-finish herds. This study was designed to follow the PRV status of growing-finishing pigs in a sample of infected herds. Fifteen infected herds were selected, of which 11 had seropositive finishing pigs and 4 had seronegative finishing pigs. These herds were visited quarterly for one year, and a cross section of growing-finishing pigs was tested for the presence of anti-PRV antibodies. The 4 herds that initially were seronegative remained seronegative, whereas of the 11 herds initially seropositive, 4 remained seropositive, 4 became seronegative, and 3 became temporarily seronegative before becoming seropositive again. Three characteristics serologic profiles were observed: one indicating continued viral spread; one indicating no spread for at least the preceding 3 months; and one indicating that PRV spread had recently ceased in this section of the herd. Results of our study indicated that periodic monitoring of a cross section of the growing-finishing pigs for their PRV serologic status was valuable for determining whether PRV was actively spreading in this section of the herd.     

Neospora caninum infection does not affect the fertility of dairy cows in herds with high incidence of Neospora-associated abortions

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.     

Application of the Neospora caninum IgG avidity ELISA in assessment of chronic reproductive losses after an outbreak of neosporosis in a herd of beef cattle.

Point-source infections are most likely the cause for Neospora caninum-induced abortion outbreaks in cattle, whereas an increased annual abortion rate may be a consequence of vertical transmission. The aims of the present study were to examine the reproductive effects of neosporosis in a beef herd for 3 years, after a point-source outbreak and to use IgG avidity serology to examine the chronicity of infections and patterns of transmission. During the study, 76-78% of animals were seropositive for N. caninum. The pregnancy rate varied from 88% to 94%, without any reduction in the pregnancy rate of seropositive cows compared with seronegative cows. The annual abortion rate was 2.5-5.5%, and all but 1 abortion occurred in seropositive dams. The efficiency of vertical transmission was estimated to be 85%. Several calves, born to seronegative dams, were seropositive at 6-13 months of age, indicating a 22% mean annual rate of horizontal transmission. The mean avidity in seropositive cows increased from 30 during the initial outbreak to 74 after 3 years. The mode of IgG avidity was 21-40 during the initial abortion outbreak, 41-60 after 1 year, and 61-80 after 2 and 3 years. The results reveal high annual rates of both vertical and horizontal transmission of N. caninum in a herd of beef cows and provide further validation on the ability of the N. caninum IgG avidity ELISA to accurately assess the chronicity of infection.     

Quantification of vertical and horizontal transmission of Neospora caninum infection in Dutch dairy herds

Ninety-six of 108 randomly selected Dutch dairy herds had one or more cows with a positive serostatus for N. caninum. In these 96 herds, we have quantified the probabilities of vertical transmission (VT) and horizontal transmission (HT) of N. caninum infection by combining serostatus and pedigree data in 4091 dam-daughter pairs. The probability of animals infected by vertical transmission during pregnancy (Prob(VT)) was calculated as the proportion of seropositive daughters among daughters of seropositive dams. The probability of animals infected by horizontal transmission (Prob(HT)) was the proportion of seropositive daughters among daughters of seronegative dams. These probabilities were calculated after the frequencies of observed dam-daughter combinations were corrected for (1) imperfect test-characteristics, (2) underestimation of horizontal transmission in situations that seronegative dams were horizontally infected after the birth of their daughters and (3) overestimation of vertical transmission in situations that seronegative daughters born from seropositive dams were horizontally infected. The incidence rate for horizontal transmission was calculated based on Prob(HT) and the average age of the animals in these herds. Based on the analysis of dam-daughter serology, Prob(VT) was 61.8% (95% CI: 57.5-66.0%) and Prob(HT) was 3.3% (95% CI: 2.7-3.9%). After adjusting the observed frequencies for imperfect test-characteristics, underestimation of horizontal transmission and overestimation of vertical transmission, Prob(VT) decreased to 44.9% (95% CI: 40.0-49.9%) while Prob(HT) increased to 4.5% (95% CI: 3.9-5.2%). Prob(HT) corresponded with an incidence rate for horizontal transmission of 1.4 (95% CI: 1.2-1.7) infections per 100 cow-years at risk. When stratifying herds for the presence of farm dogs, Prob(HT) was higher (5.5% (95% CI: 4.6-6.4%)) in herds with farm dogs than in herds without farm dogs (2.3% (95% CI: 1.5-3.4%)). When stratifying for within-herd seroprevalence, Prob(HT) was higher (10.3% (95% CI: 8.6-12.2%)) in herds with high (> or =10%) within-herd seroprevalence compared with herds with low (<10%) within-herd seroprevalence (2.0% (95% CI: 1.5-2.6%)). Although there was this relation between Prob(HT) and within-herd seroprevalence (crude OR(PREV) = 5.7 (95% CI: 4.0-7.9)), in herds without farm dogs, this relationship was no longer statistical significant (OR(PREV|DOG-) = 1.9 (95% CI: 0.7-5.5)). It indicated that the association between seroprevalence and Prob(HT) depended largely on the presence of farm dogs. In addition, when looking for the presence of specific age-groups with significantly higher seroprevalence compared with the rest of the herd, there were 7 herds in which two or more horizontally-infected animals were present in specific age-groups. This was an indication of a recent point-source exposure to N. caninum. These results reiterate the current control strategies to apply strict dog-management measures as well as to minimize within-herd seroprevalence by monitoring serostatus of animals.     

Relationships between infection with caprine arthritis encephalitis virus, intramammary bacterial infection and somatic cell counts in dairy goats.

Somatic cell counts, the bacteriological condition of the milk and antibodies against caprine arthritis encephalitis virus (CAEV) were measured monthly throughout lactation in 121 lactating goats of the Murcia-Granada breed in four commercial dairy goat herds. The prevalence of bacterial intramammary infection was 5.6 per cent and the prevalence of CAEV infection was 20.6 per cent. An analysis of variance revealed a significant effect of herd, intramammary infection and the interaction between intramammary infection and CAEV on the somatic cell count. In udder halves free of intramammary infection, the somatic cell counts were significantly lower in seronegative goats than in seropositive goats (P<0.05), but the difference was not significant in udder halves persistently infected by bacteria. There was a significant increase in somatic cell counts due to bacterial intramammary infection (P<0.01) in the seronegative goats, but this effect was not present in the seropositive animals.     

Seroprevalence of Neospora caninum infection following an abortion outbreak in a dairy cattle herd

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.     

Studies on Neospora caninum DNA detection in the oocytes and embryos collected from infected cows

Neosporosis is a major cause of abortion in cattle over the world. One of the methods of preventing vertical transmission within the herd is to avoid breeding replacement heifers from infected dams. Another procedure suggested and recommended by the International Embryo Transfer Society (IETS) is embryo transfer (ET) from infected dams into uninfected recipients. Oocytes and embryos taken from seropositive cows were examined for the presence of Neospora caninum DNA. A modified PCR protocol using Np21 and Np6 primers was applied to detect parasite DNA in the samples. The expected 328 bp product was not obtained in oocytes and/or embryos collected from seropositive dams. The results confirmed that transfer of the embryos from seropositive donors into seronegative recipients is an appropriate method to eliminate vertical transmission of neosporosis in a herd. The present study demonstrated that oocytes and embryos are not exposed to N. caninum in the uterine cavity of seropositive dams.     

Economic considerations for diagnostic and control options for Neospora caninum-induced abortions in endemically infected herds of beef cattle

OBJECTIVE: To compare economic outcome for herds not exposed to Neospora caninum with that for herds with various seroprevalences of N caninum infection and evaluate 3 control strategies. DESIGN: Economic simulation model. SAMPLE POPULATION: Beef herds with various seroprevalences of N caninum infection. PROCEDURE: A 5-year simulation model was used. Control strategies that were evaluated included culling females that fail to calve, selling seropositive females and purchasing seronegative replacements, and excluding the daughters of seropositive dams as potential replacements. RESULTS: For a 5-year period with low prices for feeder calves, endemic N caninum infection decreased mean return to fixed assets by 22.2% when true seroprevalence was 10% and by 29.9% when true seroprevalence was 70%. Percentage decrease in return to fixed assets was less dramatic when a 5-year period with high prices for feeder calves was evaluated. Analysis indicated that 2 control strategies (culling females that fail to give birth to a calf and selling seropositive female cattle and purchasing seronegative replacement female cattle) were not likely to be economically beneficial. The third control strategy (testing the entire herd for N caninum infection and excluding the female offspring of seropositive dams as replacements) appeared to be a reasonable control strategy. CONCLUSIONS AND CLINICAL RELEVANCE: For the assumptions in the model, endemic N caninum infection decreases return to fixed assets for cow-calf herds. Of the potential control strategies evaluated, testing the entire herd for N caninum infection and excluding the daughters of seropositive dams as potential replacements provided the best economic return.)     

The effect of caprine arthritis encephalitis virus infection on production in goats

Three consecutive years of monitoring 248 goats in the same flock, found that the first lactation milk yield was significantly higher in seronegative (578 L) than in seropositive (447 L) animals but this difference disappeared in the subsequent second to fourth lactations. No significant differences were found in the proportions of seronegative and seropositive does in the flock, the percentage of animals culled, the number of offspring, or in the number of cases of udder bacterial infection, irrespective of age.Removal of kids from their dams before suckling and the feeding of pasteurised colostrum resulted in reduced numbers of seropositive animals. Nevertheless, by approximately 24 months of age, 76.9% of these initially seronegative animals were seropositive, a factor that significantly contributed to flock seropositivity. This finding could be attributed to lateral virus transmission from seropositive to seronegative kids because of lack of segregation within the flock.     

Chronic Neospora caninum infection and repeat abortion in dairy cows: a 3-year study

The serological status of Neospora was monitored in animals older than 6 months in a dairy herd with a 3-year history of prevalent N. caninum and N. caninum-associated abortions. The numbers of animals in the herd tested each year of the study period were 259, 222 and 231, respectively. A separate analysis was performed on the 122 animals persisting in the herd for the 3 years. The overall seroprevalence of N. caninum in the herd decreased from 31.7% in the first year to 24.8% in the second year and to 19.9% in the third year of the study, while the overall abortion rate decreased from 20.6% in the first year to 5.5% in the second year, and 9.9% in the third. These decreases occurred in response to control measures adopted from the second year onwards, such as culling Neospora-seropositive aborted animals and inseminating Neospora-seropositive dams with beef bull semen. Of the total number of abortions recorded in seropositive animals, 51% were repeat abortions that occurred in 36.8% of the animals with a previous history of abortion. The initial seroprevalence of Neospora in the 122 animals followed for the 3 years was 18%, increasing to 21.3% in the second and third years. Seroconversion only occurred in four animals during the second and third years of the study and abortion occurred only in seropositive individuals. Of the total number of abortions recorded in the 122 animals, 61.5% were repeat abortions that occurred in 26.7% of the animals with a previous history of abortion. These results indicate that Neospora seropositivity can be very stable through time and N. caninum infected cows can show a high rate of repeat abortions. The present data reinforce the idea that annual serological screening for Neospora can be an effective and rapid method of detecting N. caninum infection, such that control measures can be established at the farm level.     

Patterns of seroconversion to Aujeszky's disease virus in unvaccinated chronically infected Swedish weaner pig-producing herds

This study was carried out in nine unvaccinated Swedish weaner pig-producing herds, ranging in size from 20 to 134 breeding animals, which had experienced a previous outbreak of Aujeszky's disease (AD) and in which seropositive sows were still present. The objective was to quantify the seroconversion rate to Aujeszky's disease virus (ADV) in breeding animals and to find out whether unvaccinated herds could become free from ADV by using only seronegative animals for replacement. Serum samples were initially obtained from all adult pigs in the herds. Animals testing negative, as well as replacement animals, were subsequently tested every second or third month and the herds were followed for 10-28 months. The herd owners were advised to keep seropositive and seronegative animals separate whenever possible and to implement sanitary measures against the reintroduction of the virus into the herds. All herds experienced long consecutive periods (> or = 4 months, median 9 months) without seroconversion. Three herds became free from ADV during the serological study; in two of these herds no seroconversion was observed. In those seven herds where seroconversion occurred, between 9 and 86% of the susceptible pigs became infected. The reinfection was indicative of the reactivation of latent virus in all herds but two, where the reintroduction of the virus was most likely. The pattern of seroconversion was either sporadic, involving not more than three animals at a time, or epidemic, involving a large proportion of the susceptible animals in the herd. Severe clinical outbreaks hit the two largest herds and these only became ADV-free after the conclusion of the study when vaccine was used, which reduced the incidence of seroconversion to zero. The results from the present study show that it is possible for smaller herds to achieve freedom from ADV without any radical control methods, provided that only ADV-free replacement animals are used and the virus is not reintroduced. Moreover, the finding that long periods can elapse without transmission suggests that when infection is discovered in a herd, the risk of massive spread is not necessarily imminent.     

Targeted selective treatment of lungworm infection in an organic dairy herd in Sweden

The effect of targeted selective anthelmintic treatment on the seroprevalence of the lungworm Dictyocaulus viviparus in cattle was investigated. The study was commenced on an organic dairy enterprise in Sweden in November 1998 after the observation of an outbreak dictyocaulosis in the herd, and then continued for almost 3 years. The first year sampling was conducted on a monthly basis and then biannually with the exception of between August and November 2000 when sampling was performed monthly following a second outbreak of dictyocaulosis. Throughout the study, blood samples were examined for specific IgG(1) levels from all animals in the herd that had been grazing for more than 3 months. At the first sampling occasion, 13% out of the 90 blood samples were seropositive. One month later, after targeted selective treatment with eprinomectin (Eprinex), Merial), the whole herd was seronegative. Seroprevalence then gradually increased and 1 year later it returned to levels similar to those observed at the start of the study. At turnout in April 2000, seroprevalence was 1.3% but it then rapidly increased to 28% and 30% in August and September, respectively. This increase was mainly due to an increase in FSG animals of which many were coughing. Consequently, all seropositive animals were injected with ivermectin (Ivomec), Merial) at 0.05 mg/kg body weight in late August 2000. Although all animals recovered, seroprevalence was only reduced to 12% 1 month later. The differences in seroprevalence after both of these anthelmintic treatments were probably attributed to the timing. The first deworming with eprinomectin was conducted in November when the infection already was transient, whereas ivermectin in connection with the second outbreak was injected in a more acute phase of the infection cycle. Infection levels in 2001 were low with seroprevalences of 2.3% and 5.6% in May and September, respectively. These results show that dictyocaulosis in Sweden can be effectively controlled by the use of macrocyclic lactones. However, the infection was not eradicated from the herd despite close monitoring of the seroprevalence and targeted selective treatment of every seropositive animal on two occasions.     

Long-term lack of transmission of Aujeszky's disease virus (ADV) in a chronically infected Swedish weaner pig producing herd

A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation.     

Longitudinal study of hepatitis E virus infection in Spanish farrow-to-finish swine herds

Hepatitis E is a zoonotic disease and is highly prevalent in European swine livestock. There is a need to compare the infection dynamics of hepatitis E virus (HEV) between herds with the same production system and determine the percentage of animals that could arrive infected at slaughter age. Therefore, a longitudinal study was performed in six Spanish farrow-to-finish affected farms. Twenty piglets per farm were monitored from nursery to slaughter. RT-PCR and serology techniques were applied to analyze longitudinally collected sera and/or faecal samples. Liver and bile samples were also taken at the abattoir. Anti-HEV IgM were firstly detected at 7 weeks of age in 5 farms whereas at 13 weeks of age in 1 farm (farm 2). At slaughter age 50–100% of pigs had seroconverted to anti-HEV IgG in the former 5 farms whereas in the other herd only 5% of pigs were IgG seropositive (farm 2). Six out of 96 livers and 5 out of 80 biles analyzed were HEV positive at the abattoir (total percentage of infected animals: 11.5%). All these positive animals had already seroconverted except 2 pigs of farm 2. Hence, pigs can be seronegative at slaughter age being infected during the latest fattening period. Manipulation of HEV-infected livers or other organs from pigs could be considered a possible route of transmission in Spanish abattoirs. This study represents the first longitudinal survey on swine HEV infection dynamics conducted in different herds.     

Antibodies to bovine leukemia virus in a leukosis dairy herd and suggestions for control of the infection.

A closed herd of 765 Holstein-Friesian dairy cattle with a history of multiple cases of leukosis was tested for antibodies to bovine leukemia virus by the bovine leukemia-glycoprotein immunodiffusion test. A total of 355 animals (46.4%) were antibody positive. Prevalence was 60% in the 373 milking cows and 100% in the breeding bulls. Antibodies were present in 59% of newborn calves. Prevalence of antibodies was higher in older animals and cows in second lactation had a higher prevalence than cows in first lactation (72% vs 43%). Proposed control measures in this herd aim at preventing infection of calves, heifers and lactating cows by: 1) separating them into groups negative and positive for bovine leukemia virus antibodies, 2) not allowing calves to receive colstrum or milk from infected cows and 3) by using seronegative bulls for natural breeding tested at three month intervals. Calves should be tested after six months of age. Before this time calves of positive mothers should be treated as being positive.     

Neospora abortions in dairy cattle: diagnosis, mode of transmission and control

AIM: To determine the contribution of Neospora caninum to abortions on a dairy farm in NSW (Australia), determine the mode of transmission and develop and trial a control option for infection. METHODS: Two whole herd bleeds were conducted 12 months apart and the association between serological status and abortion events were calculated for a number of bovine abortifacients. Family trees were constructed for N. caninum seropositive cattle in the herd. Some N. caninum seropositive cows were culled from the herd and no female offspring was retained from seropositive cows. RESULTS: At the first whole-herd bleed in December 2002 a seroprevalence of 10.2% for N. caninum infection was detected. Cows with N. caninum infection were 13 times more likely to abort than uninfected ones. Seventy-five percent of seropositive animals in the herd were related, suggesting a high degree of congenital infection/transmission. Only 15% of infections were likely to be postnatally acquired. Selective culling of seropositive cows and not breeding from them reduced the number of seropositive animals. Only one newly sero-converted cow was detected at the second whole-herd bleed 12 months later. CONCLUSIONS: Seroepidemiological approaches were able to establish a high degree of association between N. caninum infection and low-level abortion in the dairy herd. Vertical transmission of infection was the predominant mode of infection and hence control efforts aimed at selectively culling seropositive animals from the herd were highly successful in reducing the level of infection.     

Outbreak of abortion associated with Neospora caninum infection in a beef herd

Abortion outbreaks caused by infection with Neospora caninum in beef cattle have not been well documented. Neospora caninum infection was confirmed in 4 fetuses that were aborted by cattle in a 350-head beef herd; an additional 58 cattle aborted during the next 2.5 months. Overall, 44.4% (157/354) of the cattle in the herd did not become pregnant or experienced fetal loss during this period. Initially, 81.3% (282/347) of the herd was seropositive for antibodies to N caninum, and seropositive cows were 6.2 times as likely to not be pregnant as were seronegative cows. Other potential causes of abortion were not identified in this herd. Following the outbreak, few cattle in the herd or in a second exposed herd seroconverted, but high antibody titers persisted in most seropositive cattle through the end of the calving season. Evidence of cow-to-fetus transmission of the organism was detected in > 82% of seropositive cows.