A longitudinal study of Neospora caninum infection on a dairy farm in New Zealand

A 600-cow New Zealand dairy herd experienced an abortion storm in 1997 and was monitored (blood sampling at about 3-month intervals) from May 1997 until January 1999. Abortion risk reached 9% in 1997 and was highest in heifers at 19%. The abortion risk decreased in 1998 to 3.2% (still somewhat higher than during the years prior to the outbreak). The serological reaction pattern for Neospora caninum showed an association with abortion risk only around the time of the 1997 outbreak when seropositive cows were 4.2 times more likely to abort than negative ones. Over the whole study period, only 27% of cows that were sampled on all nine visits always tested negative. Offspring from dams which had positive tests for Neospora caninum were 2.4 times more likely to abort than those from dams testing consistently negative. Controlling for age and breed, seropositive cows produced more milk than those that were consistently negative. Infection might have been present endemically within this herd prior to the epidemic, but in 1997 an additional factor appeared to have triggered the outbreak.     

Herd-level risk factors for Neospora caninum seroprevalence in dairy farms in southern Brazil

A cross-sectional study was used to test the relationship between herd seroprevalence to Neospora caninum and various potential herd-level risk factors in 60 dairy farms located in two distinct regions in southern Brazil. Thirty farms were randomly selected from within each region. A questionnaire was designed to summarize each farm's production system as it might relate to N. caninum transmission. The questionnaire contained 105 closed questions relating to general characteristics of the farms, farm facilities, management, source of food and water, herd health, environment and biosecurity, which included questions relevant to N. caninum transmission, including presence and number of dogs and other animals, purchase of animals and contact with man. Serum samples were collected from 40% of animals in each farm and N. caninum antibodies were detected by immunofluorescent antibody test (IFAT). The association between potential risk factors and the probability of an animal being seropositive was modeled using a generalized estimation equations (GEE) logistic regression model. The model accounted for multilevel correlation of data from multiple animals within herds. The mean (+/-S.D.) number of animals in the 60 herds was 64.5 (+/-45.6), ranging from 20 to 280 females. Blood samples were collected from 1549 animals. The size of the farms varied from 4 to 100 ha (mean 30.1+/-25.9 ha). At least one dog was found in 57 of the 60 dairy farms (95%). The mean number of dogs was 3.1 (+/-1.9), ranging from 0 to 10. All females were raised on pasture. For all cattle sampled, N. caninum seroprevalence was 17.8%. Overall, 93.3% of herds (56/60) had at least one seropositive animal identified. Four variables were significantly associated with N. caninum sero-response in the 57 dairy farms, which were included in the final multivariable model: the number of dogs on the farm, farm area (hectares), feeding pooled sources of colostrum and region. The odds of a cow being seropositive increased 1.13 times for each additional dog present on the farm (P=0.021). Cattle from farms that fed calves colostrum pooled from multiple cows had 1.79 times greater odds for being seropositive for N. caninum (P<0.003). The probability of being seropositive was inverse to the area of the farms, such that cattle had 0.92 times the odds to be seropositive (P=0.014) for each additional 10 ha of farmland. Finally, cattle from farms in region one had 0.71 times the odds to be seropositive than cattle from region two (P=0.035). Results of this study suggest that several risk factors may explain why dairy cattle in Brazil may become exposed to N. caninum. However, further investigation of these factors is necessary because the purpose of this study was to refine and generate hypotheses on N. caninum transmission.     

A longitudinal study of seroprevalence and seroconversion of Neospora caninum infection in dairy cattle in northeast Thailand

A long-term study was carried out in 11 dairy herds in the Khon Kaen province of northeast Thailand between August 2001 and November 2004. The objective was to investigate seroprevalence dynamics of Neospora caninum infection in the herds and to demonstrate patterns of seroconversion in individual cattle. Each herd was visited once a year, in total four times, and sera from cattle > 3 months of age and farm dogs as well as a sample from the bulk milk were collected. All samples were analysed for presence of specific antibodies by an N. caninum iscom ELISA. The overall percentage of antibody-positive cattle was constant and varied only between 10 and 13% over the 4 years, but the variation in within-herd seroprevalence between herds was substantial. Two herds had > or = 20% seropositive animals at all samplings and consistently high bulk milk OD, whereas two herds had no seropositive animal at the last two samplings and low bulk milk OD. Five herds had a decreasing trend of within-herd seroprevalence, whereas the remaining six herds had a higher portion of test-positive individuals at the end of the study. A total of 424 individuals were sampled more than once; 344 (81%) and 32 (8%) were consistently antibody-negative and antibody-positive, respectively. The proportions of animals that changed from being seronegative to seropositive and from being seropositive to seronegative between the years were 3.9-4.6% and 19-39%, respectively. Apparent vertical and horizontal transmission rates were 58% (95% CI; 44-71%) and 5% (95% CI; 3-7%), respectively. In conclusion, the overall percentage of N. caninum antibody-positive cattle was constant over the years, but the within-herd seroprevalence varied substantially between the herds. Seroconversions were likely to occur in individual cattle although most animals had consistent serological status throughout the study.     

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.     

Neospora caninum infection in three dogs

Infection with Neospora caninum in three young dogs is described. The predominant clinical signs were lower motor neuron deficits of the pelvic limbs, bladder and rectum. In two cases there was liver infection and dysfunction. The younger dogs had an acute onset rapidly progressive syndrome. The older dog had a similar but more chronic course. The diagnosis was confirmed by an immunofluorescence antibody test. The parasite is sensitive to clindamycin and trimethoprim/sulphonamide preparations, however the prognosis for return to function is poor especially if muscle contracture has occurred.     

Presence of Neospora caninum specific antibodies in three dairy farms in Georgia and two in Texas

Neospora caninum is known to cause abortion in cattle. This study demonstrated the presence of specific IgG to Neospora in milk and serum samples obtained from three dairy farms in Georgia and two in Texas. Samples from four hundred fourteen dairy cows were examined using a western blot assay of which 362 were milk and 87 were serum. Samples with antibodies to Neospora were identified in 32.1% (105/327) of the examined animals in Georgia, whereas in Texas it was identified in 10.3% (9/87). Positive Georgia samples were found in 24.4% from farm A (28/115), 21.6% from farm B (30/139), and 64.4% from farm C (47/73). In Texas, 13.5% (7/52) of animals in farm D and 5.71% (2/35) from farm E also had specific antibodies to Neospora. The number of animals from Georgia dairy farms with antibodies to Neospora was significantly higher than the Texas dairy farms. This may be related to the age of the animals examined in this study (more than 2 years old). Antibodies present in sera had excellent agreement with the antibodies present in milk. Collection of milk samples for serological testing is easier and less invasive than obtaining bovine sera, therefore offering an alternative for animal testing.     

Epidemiology and impact of Neospora caninum infection in three Queensland tropical dairy herds

This study investigated the epidemiology of Neospora caninum in three tropical dairy herds in North Queensland, Australia. All animals in the herds were bled, and the sera were tested by ELISA for N. caninum antibodies. Herd records were examined, and the number of calves carried to term and the number of abortions which occurred over the lifetime of each animal were recorded to determine the abortion rate for each animal. Pedigrees were constructed for two of the herds to investigate whether vertical transmission was occurring. The seroprevalence of N. caninum ranged from 23% to 34%. The abortion rate in seropositive animals was significantly (p < 0.001) higher than in seronegative animals in all three herds (12-20.1% cf. 3.6-7%). Overall, the probability of a calf being seropositive was 3.5 times higher when the dam was also seropositive than when the dam was seronegative. Subsequent selective breeding employed by one herd reduced the N. caninum seroprevalence from 23% to 5% over a 9-year period. This study shows that N. caninum infection is prevalent in North Queensland dairy cattle, and both post-natal infection and vertical transmission are common.     

Seroepidemiological study of Neospora caninum infection in dogs found in dairy farms and urban areas of Aguascalientes, Mexico

The objective of this study was to describe the seroepidemiology of Neospora caninum infection in dogs in close contact with dairy cattle and dogs from urban areas of Aguascalientes, Mexico, as well as to estimate the possible association between age, gender and size of these groups and seroprevalence. Sera were obtained from samples of 152 dogs in dairy farms and 116 in the urban area, and were subjected to ELISA test. General seroprevalence reached 32%, while the seroprevalence in farm dogs (41%) was significantly higher than in dogs from the urban area (20%) (p<0.05). Regarding age groups, general seroprevalence was greater among dogs between 11 and 15 years of age (67%) remaining equal between males and females (32 and 31%, respectively). Nevertheless, females resident in farms had a higher seroprevalence (42%) than female resident in the urban area. Regarding size, large-sized animals had greater seroprevalence in farms (58%), while in the urban area medium-sized animals were those that had the highest seroprevalence (27%). It was found that dairy farm dogs had a higher risk of infection (OR=2.79; p=0.0004), and that in said group, the age range from <1 to 5 years of age was identified as a risk factor (OR=3.11, p=0.001).     

Risk factors of Neospora caninum infection in dogs and cats in dairy farms in Western Thailand

The objectives of this study were to investigate the risk factors of Neospora caninum infection in dogs and cats found in dairy herds in western Thailand. A case-control study was conducted in dairy herds in three western provinces including Nakhon Pathom, Ratchaburi and Kanchanaburi. Blood samples of pets from 14 positive dairy herds and 26 herds from negative neighbouring farms which were randomly selected, in total blood samples from dogs and cats from 40 herds were collected and examined for antibodies against N. caninum infections using competitive ELISA and indirect fluorescent antibody test (IFAT). No seropositive cats were found. Of the 38 positive dogs, four (10.5%) were seropositive to N. caninum, which was higher than the proportion of seropositive in the negative herd population (one of 76, 1.3%). The higher proportion of seropositive farm dogs as compared with neighbouring dogs tended to be significant (P = 0.055).     

Epidemiological investigations of abortions due to Neospora caninum on Swiss dairy farms

Abortions apparently due to Neospora caninum in two Swiss dairy herds were investigated by means of a PCR and ELISA, and other potential causes were eliminated. In addition, a case-control study of 24 case herds and 24 control herds indicated that N caninum-associated abortions were more likely to occur in herds with antibodies to Coxiella burnetii (with an odds ratio [OR] of 3.38 with a 95 per cent confidence interval [CI] of 1.82 to 6.22), whereas the likelihood was less in herds with antibodies to Leptospira species (OR 0.34,95 per cent CI 0.13 to 0.75), or in herds with antibodies to bovine viral diarrhoea (BVD) virus (OR 0.75,95 per cent CI 0.56 to 1.00), or Chlamydia psittaci (OR 0.18,95 per cent CI 0.09 to 0.35), or in herds in which BVD virus had been isolated from an aborted fetus (OR 0.11,95 per cent CI 0.02 to 0-58).     

Frequency of infection by Neospora caninum in wild rodents associated with dairy farms in Aguascalientes,Mexico

The purpose of this study was to detect the presence of Neospora caninum in tissues from wild rodents associated with dairy farms in Aguascalientes, Mexico. Individuals from Mus musculus, Rattus novergicus and Spermophilus variegatus were caught in dairy farms with history of positive status to N. caninum. A total of 33 rodents were caught from which samples were taken of brain, spinal cord, liver and heart and were tested with nested PCR and Immunohistochemistry (IHC). Results obtained with PCR showed that M. musculus had 77% (10/13) positive samples to N. caninum, S. variegatus had 71% (10/14) and R. novergicus had 50% (3/6). The results obtained with IHC showed that 15% (2/13) of M. musculus individuals were positive, while 43% (6/14) of S. variegatus and 33% (2/6) R. novergicus were also positive. This is the first report of the presence of N. caninum in S. variegatus.     

Seroprevalence of Neospora caninum in dairy cattle in Bahia, Brazil.

Sera collected from 447 dairy cattle on 14 dairy farms were tested for Neospora caninum antibodies by use of an immunofluorescent antibody technique. Positive reactions with titres > or =1:200 were found in 63 (14.09%) of animals. Neospora positive sera were also tested for Toxoplasma gondii antibodies by using a commercial latex agglutination test. Antibodies to T. gondii were detected in 3 (4.76%) of 63 N. caninum positive sera. These results indicate that N. caninum infection is widespread among dairy cattle in Bahia state.     

Neospora caninum infection in an aborted bovine foetus in Brazil

Abstract

Extract

Neospora caninum is an apicomplexan protozoan parasite first reported in dogs (Bjerkås et al., 1984 Bjerkås, I, Mohn, SF and Presthus, J. 1984. Unidentified cyst-forming sporozoan causing encephalomyelitis and myositis in dogs. Zeitschrift für Parasitenk, 70: 271–274. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Dubey et al., 1988a Dubey, JP, Carpenter, JL, Speer, CA, Topper, MJ and Uggla, A. 1988a. Newly recognized fatal protozoan disease of dogs. Journal of the American Veterinary Medical Association, 192: 1269–1285. [PubMed], [Web of Science ®] , [Google Scholar], Dubey et al., 1988b Dubey, JP, Hattel, AL, Lindsay, DS and Topper, MJ. 1988b. Neonatal Neospora caninum infection in dogs: Isolation of the causative agent and experimental transmission. Journal of the American Veterinary Medical Association, 193: 1259–1263.  [Google Scholar]) and subsequently recognised as a cause of bovine abortion (Dubey and Lindsay, 1993 Dubey, JP and Lindsay, DS. 1993. Neosporosis. Parasitology Today, 9: 452–458.  [Google Scholar]). Natural N. caninum infections have been reported in other animal species including the goat, sheep, horse and deer (Dubey and Lindsay, 1996 Dubey, JP and Lindsay, DS. 1996. A review of Neospora caninum and neosporosis. Veterinary Parasitology, 67: 1–59. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). The dog was recently identified as definitive host of the parasite (McAllister et al., 1998 McAllister, MM, Dubey, JP, Lindsay, DS, Jolley, WR, Wills, RA and McGuire, AM. 1998. Dogs are definitive hosts of Neosporu caninum. International Journal for Parasitology, 28: 1473–1478. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). Neospora caninum has a worldwide distribution (Barber et al., 1995 Barber, JS, Holmdahl, OJM, Owen, MR, Uggla, A and Trees, AJ. 1995. Characterization of the first European isolate of Neosporu caninum (Dubey, Carpenter,Speer, Topper and Uggla). Parasitology, 111: 563–568.  [Google Scholar]; Duivenvoorden, 1995 Duivenvoorden, J. 1995. Neospora abortions in eastern Ontario dairy herds. Canadian Veterinary Journal, 36: 623–623.  [Google Scholar]; Jardine and Wells, 1995 Jardine, JE and Wells, BH. 1995. Bovine neosporosis in Zimbabwe. Veterinary Record, 137: 223–223.  [Google Scholar]; Stenlund et al., 1997 Stenlund, S, Bjorkman, C, Holmdahl, OJM, Kindahl, H and Uggla, A. 1997. Characterization of a Swedish bovine isolate of Neospora caninum. Parasitology Research, 83: 214–219.  [Google Scholar]; Thornton et al., 1991 Thornton, RN, Thompson, EJ and Dubey, JP. 1991. Neospora abortion in New Zealand cattle. New Zealand Veterinary Journal, 39: 129–133. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]; Umemura et al., 1992 Umemura, T, Shiraki, K, Morita, T, Shimada, A, Haritani, M, Kobayashi, M and Yamagata, S. 1992. Neosporosis in a dog: The first case report in Japan. Journal of the Veterinary Medical Science, 54: 157–159.  [Google Scholar]) but the presence of N. caninum in Brazil has not been confirmed.     

Survey of Neospora caninum infection by nested PCR in aborted fetuses from dairy farms in Aguascalientes, Mexico

The aim of this study was to determine by nested PCR probe the presence of Neospora caninum in fetal brain tissue from aborted dairy fetuses in Aguascalientes, a state in the central part of Mexico. Forty-four fetal brains from eight dairy farms were analyzed using single tube nested PCR probe with primers NF1, NS2, NR1 and SR1, with histopathology as the reference technique. From the 44 bovine fetuses studied, 35 (80%) were diagnosed as being infected by N. caninum using PCR probe and 20 (45%) were considered positive by histopathology, because they had lesions suggestive of bovine neosporosis. Fair agreement was observed (31%) between both probes. The age of aborting cows ranged from 1.6 to 2.9-year-old in 17 (49%) of the positive cases diagnosed by PCR. Gestational ages of aborted fetuses ranged from <3 to 9 months, with average of 5.6 months, and no statistical significant difference was observed when ages of infected and no infected fetuses were compared (P > 0.05). The frequency of N. caninum positive cases observed could be considered to be higher than other areas of Mexico and other countries.     

Epidemiological and financial considerations for the control of Neospora caninum on Swiss dairy farms

Neospora caninum is widely recognized as one of the most important abortifacients in cattle and causes substantial financial losses to bovine livestock production. This study aimed to calculate the losses caused by N. caninum on Swiss dairy farms and to evaluate the efficacy and profitability of the control strategies culling, not breeding replacements and chemotherapy of calves on farm level. Three different farm sizes with high, medium and low herd prevalences were defined. Epidemiological and financial models were used to simulate the effect of control strategies on the prevalence over time and to perform a cost-benefit analysis. The median annual losses on farm level ranged between CHF 3094.- (= Euro 1875; 60 dairy cattle, high prevalence) and CHF 134.- (= Euro 81; 15 dairy cattle, low prevalence). Culling of animals that had any abortion or a N. caninum abortion, or not breeding replacements from such animals, respectively, were neither effective nor profitable. Only the strategy "not breeding replacements from N. caninum seropositive cows" on farms with a high prevalence was financially attractive. The strategy "chemotherapy of calves" should be re-evaluated as soon as new data regarding the efficacy of treatment and a corresponding protocol have been scientifically validated.     

Factors associated with infection by Neospora caninum in dogs in Brazil

From August 2006 to 2008, 411 dogs in northeastern Brazil were evaluated for seropositivity to Neospora caninum. The dogs were clinically examined, and their owners were interviewed about the conditions in which the animals were maintained in order to assess the factors associated with infection by this parasite. A serum sample was taken from each dog for serological examination in an indirect fluorescent antibody test for N. caninum. The Yates' Chi-square test or Fisher's exact test was used to select the variables for the multivariate logistic regression model. Seropositivity was detected in 9.26% of dogs. The seropositivity rates of dogs from different environments were 2.6% (4/156) in urban areas, 13.1% (28/214) in peri-urban areas, and 14.6% (6/41) in rural areas. Factors associated with seropositivity for N. caninum were the following: contact with other dogs, access to food outside the home and residing in the peri-urban or rural environments (p<0.05). Results of this study confirm that dogs in urban, rural and peri-urban areas of northeastern Brazil are exposed to N. caninum. Control measures to prevent infection of dogs in the studied region should be focused primarily on preventing access to potential sources of infection, which include environments with other dogs, bovines, and other small intermediate hosts, such as birds and rodents.     

Factors associated with seroprevalence of Neospora caninum in dairy cattle in southeastern Brazil

Neosporosis is an infectious disease caused by Neospora caninum, an obligate intracellular cyst-forming protozoan considered a major cause of miscarriage in dairy cattle in many parts of the world. This cross-sectional study evaluated the relationship between reproductive abnormalities and seropositivity to N. caninum in 1,204 dairy cows from 40 farms located in the state of Minas Gerais, southeastern Brazil. Producers were interviewed, and blood samples were collected to perform indirect immunofluorescence tests (IFAT 1:200). Association between reproductive abnormalities and seropositivity in cattle was evaluated with generalized estimating equations. The true herd-level seroprevalence of N. caninum was 95 % (83.3–99.1), while the individual-level true seroprevalence was 21.6 % (19.2–24.2). Several reproductive abnormalities were significantly associated with seropositivity to N. caninum: occurrence of repeated estrus (p?=?0.02; OR?=?3.84; 95 % CI?=?1.239–11.893), repeated miscarriages (p?=?0.001; OR?=?2.54; 95 % CI?=?1.423–5.402), and temporary anestrus (p?=?0.001; OR?=?3.44; 95 % CI?=?1.976–5.994). Furthermore, loose dogs (p?=?0.041; OR?=?2.20; 95 % CI?=?1.033–4.672) when fed raw meat (p?=?0.001; OR?=?1.91; 95 % CI?=?1.443–2.519) are risk factors for N. caninum infection. We observed that seropositivity to N. caninum in cattle increases risk of miscarriage by almost twice throughout the reproductive life of cows (p?=?0.004; OR?=?1.978; 95 % CI?=?1.249–3.131). Serologic evidence in this study indicates that N. caninum infection is widely distributed among dairy herds and significantly associated with reproductive disorders, especially miscarriage, repeated estrus, and temporary anestrus.     

Seroprevalence of Neospora caninum infection in dairy and beef cattle in Paraguay

Seroprevalence of Neospora caninum in 879 beef and dairy cattle in different locations of Paraguay was determined by an ELISA. In the survey, 262 (29.8%) cattle were positive to N. caninum, and animals with anti-Neospora antibody titre were observed in all the locations tested in the country. Serum samples taken from a herd that exhibited persistent abortion had the highest percentage of animals being positive to the parasite (17/30, 56.7%). In the same herd, abortion was significantly more likely in animals with high anti-Neospora antibody titre. Immunoblot analysis demonstrated that the banding pattern from positive Paraguayan cattle was similar to that seen with the positive control sample. In conclusion, N. caninum infection is present among Paraguayan beef and dairy cattle, and it may be an important cause of bovine abortion in Paraguay.