Regional seroprevalence of bluetongue virus in cattle in Illinois and western Indiana

OBJECTIVE: To estimate seroprevalence of bluetongue virus (BTV) and the geographic distribution of seropositive cattle herds in Illinois and western Indiana. SAMPLE POPULATION: 10,585 serum samples obtained from cattle in 60 herds during 3 transmission seasons (2000 through 2002). PROCEDURES: In a longitudinal study, serum samples were tested for BTV antibodies by use of a competitive ELISA. Four geographic zones were created by use of mean minimum January temperature. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone, age of cattle, herd type, and transmission season. RESULTS: Overall, BTV antibodies were detected in 156 (1.5%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 1.49%, 0.97%, and 2.18%, respectively. Risk of being seropositive for BTV was associated with geographic zone and age. Seroprevalence increased progressively from northern to southern zones, with no evidence of BTV infection in the northernmost zone. In the southernmost zone, annual seroprevalence ranged from 8.65% to 11.00%. Adult cattle were 2.35 times as likely as juvenile cattle to be seropositive. CONCLUSIONS AND CLINICAL RELEVANCE: Overall seroprevalence was lower than has been reported for Illinois cattle. Bluetongue virus antibodies were distributed heterogeneously in this region. Only in the southernmost zone was seroprevalence consistently > 2%. Regionalization of BTV risk based on state borders does not account for such variability. Serologic data could be combined with landscape, climate, and vector data to develop predictive models of BTV risk within transitional regions of the United States.     

Pestivirus infections in Norway. Serological investigations in cattle, sheep and pigs.

Serum samples from 1,133 dairy cows (187 herds), 3,712 ewes (103 flocks) and 1,317 adult pigs (877 herds), were tested for neutralizing antibodies against the NADL strain of bovine virus diarrhoea virus. The prevalence rate of seropositive animals was 18.5% in cattle, 4.5% in sheep and 2.2% in pigs, such seroreactors being found in 28% of the cattle herds and 18% of the sheep flocks. In all three species the rate showed considerable herd and geographical variation. In cattle the seroreactor rate was similar in herds with normal reproduction and in 62 herds with problems of repeat breeding. Of 31 pig sera containing antibodies against the NADL strain, 27 were also positive in a neutralization test for antibodies against swine fever virus (Baker strain). However, all sera showed a higher titre of antibodies against the bovine strain than against the swine fever virus. It was concluded that the immune response of the pigs had been induced by ruminant pestivirus, and not by swine fever virus.     

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.     

No evidence of bluetongue virus in Switzerland

We report the results of the first survey for antibody against bluetongue virus (BTV) that was conducted in Switzerland in the year 2003. In a nationwide cross-sectional study with partial verification, 2437 cattle sera collected from 507 herds were analysed using competitive enzyme-linked immunosorbent assays (c-ELISA). To adjust for misclassification, 158 sera, including 86 that were recorded equivocal in Switzerland, were sent to the Office Internationale des Epizooties designated regional reference laboratory in the UK for confirmation. No BTV antibody was detected in any of these samples, confirming the absence of BTV from Switzerland in 2003. The specificity of the c-ELISA used in Switzerland for individual Swiss cattle was calculated to be 96.5%. The mean herd sensitivity achieved in our survey ranged from 78.9% to 98.8% depending on the with-in herd prevalence and test sensitivity used for the calculations. The cumulated confidence level achieved with the survey based on a minimal expected prevalence of 2%, was 99.99% and therefore it was concluded that there was no evidence of BTV circulation in Switzerland in 2003.     

Prevalence of trichinosis in southern Louisiana swine

After an outbreak of human trichinosis in Louisiana involving 45 cases and 1 death in 1979 and 1980, a survey of pigs killed in 21 selected small slaughterhouses in southwestern Louisiana was conducted from November 1980 to September 1981. The sera from 1,225 pigs were examined for trichinella antibodies using an enzyme-linked immunosorbent assay (ELISA); 1,223 diaphragms were subjected to peptic digestion and examined for the presence of Trichinella spiralis larvae. One diaphragm (0.08%) was found to contain T spiralis (26 larvae/g of muscle) and 4 of the slaughterhouse sera were positive (0.33% seroprevalence). Pigs in 52 herds throughout the state were also tested for ELISA antibodies. The ELISA-positive pigs were not found among the 267 pigs tested from the 52 herds.     

Neutralizing antibody responses to bluetongue and epizootic hemorrhagic disease virus serotypes in beef cattle

Blood samples were obtained from sentinel beef cattle at monthly intervals, and the sera were tested for antibodies, using a bluetongue virus (BTV) immunodiffusion test (IDT) and virus-neutralization test (VNT), for 5 BTV serotypes (2, 10, 11, 13, and 17) and 2 epizootic hemorrhagic disease virus (EHDV) serotypes (1 and 2). The cattle tested were transported from Tennessee to Texas in 1984 and 1985. All cattle were seronegative by the BTV IDT at the initial bleeding in Texas in 1984 and 1985. In 1984, 16 of 40 (40%) cattle seroconverted as assessed by results of the BTV IDT. In the 16 seropositive cattle in 1984, neutralizing antibodies were detected to BTV serotypes 10 (n = 7), 11 (n = 3), and 17 (n = 11), and EHDV serotypes 1 (n = 1) and 2 (n = 7). In 1984, no cattle seroconverted to BTV-2 or BTV-13. In 1985, 10 of 36 (27.8%) cattle seroconverted as assessed by results of the IDT. Of the 10 seropositive cattle in 1985, neutralizing antibodies were detected to BTV serotypes 10 (n = 10), 11 (n = 10), 13 (n = 7), and 17 (n = 5), and EHDV serotypes 1 (n = 1) and 2 (n = 7). In 1985, no cattle seroconverted to BTV-2. Clinical diseases attributable to BTV or EHDV was not detected in these cattle in 1984 or 1985.     

Trichinella spiralis infection induces β-actin co-localized with thymosin β4

A serological survey for Neospora caninum and Besnoitia besnoiti was carried out in beef and dairy cattle in South Australia. Serum samples of dairy cattle (n=133) from 9 properties and tank milk samples from a further 122 dairy herds were tested. An additional 810 sera from beef cattle from 51 properties were also tested. Testing at the individual animal level by IDEXX NEOSPORA X2 Ab test ELISA revealed a low prevalence of N. caninum antibodies of only 2.7% (95% CI; 1.6-3.7%) sera positive, as did the milk testing that showed 2.5% (95% CI; 1.4-3.6%) of tank milks being positive. At the herd level, 29.4% (95% CI; 16.9-41.9%) of beef, and 44.4% (95% CI; 12.0-76.9%) of dairy cattle herds showed serum antibodies. The highest within-herd prevalence in beef was 20% and 25%in dairy, which explains the low herd prevalence in dairy detected by bulk milk testing. Testing for B. besnoiti antibodies by PrioCHECK(?) Besnoitia Ab 2.0 ELISA initially identified 18.4% (95% CI: 15.8-21.0%) of 869 individual cattle sera as positive by ELISA at the manufacturer's suggested cut-off threshold (15 PP). Additional tests by immunoblot and IFAT, however, could not confirm any of the ELISA results. The use of a higher (40 PP) threshold in the ELISA is suggested to improve specificity. There is thus no evidence of B. besnoiti infection in South Australian cattle.     

Seroprevalence of antibodies against bluetongue virus in animals imported to Poland from EU countries

The aim of this study was to determine the seroprevalence of BTV-specific antibodies in animals imported to Poland from EU countries after 15 June 2006. From 1 January 2007 to 22 January 2008, a total of 10719 samples of sera collected from cattle, goats and fallow deer were tested. Sera were screened using the highly sensitive and specific c-ELISA test and positive results were confirmed by the AGID assay. Out of 10719 sera, 30 (0.28% of the total number of samples) were found to be positive in both tests applied. All of 21 seropositive cattle specimens were imported to Poland from Germany whereas 9 seropositive fallow deer were of Dutch origin. In conclusion, it can be stated that because BTV situation in Europe is getting worse, implemented surveillance studies should be continued to monitor the actual BT status in Poland.     

Comparison of three serological tests in the diagnosis of Brucella infection in unvaccinated cattle in Eritrea

Three serological methods, the Rose-Bengal test (RBT), the complement-fixation test (CFT) and an indirect enzyme-linked immunosorbent assay (I-ELISA) were compared for the detection of Brucella-infected animals in unvaccinated cattle herds in Eritrea. In this study, 71 herds first were classified as positive or negative for Brucella infection on the basis of at least one animal being seropositive by RBT and CFT. All the 159 RBT-positive samples from the 26 seropositive herds and 214 RBT-negative samples randomly selected from the seropositive herds and from the 45 negative herds were tested further by CFT and I-ELISA. Using the ELISA titer as main predictor, and incorporating the RBT results, a logistic model was built to predict the CFT-negative or -positive status of individual sera and to estimate sensitivity and specificity. Whilst the ELISA titers (< or =20) accurately predicted all the negative sera in herds that were also negative by the CFT, the number of seropositive animals was higher by ELISA in herds that had positive animals. Serum samples which give higher degrees of agglutination with the RBT need not be re-tested with CFT; consideration of the seropositive status of a herd should be taken into consideration on defining the cut-off optical density readings for ELISA.     

Control and eradication programme of enzootic bovine leucosis (EBL) from selected dairy herds in Turkey

Serum samples of 15,909 cattle from 31 dairy herds located in various regions of Turkey were tested for the presence of antibodies against bovine leucosis virus (BLV) using Agar Gel Immuno-diffusion technique (AGID). 48.3% (15/31) of the herds had seropositive animals and positivity rates were detected from 0.5-34.4% in these herds. In an EBL control/eradication programme all seropositive animals were culled in the infected herds. Thereafter, a total of 74,347 sera were tested for the presence of BLV specific antibodies. The serological results and detail of EBL control/eradication programme were shown in this paper.     

Prevalence and geographic distribution of bovine viral diarrhoea (BVD) infection in Finland 1993-1997

Bulk milk samples from every herd supplying milk to dairies in Finland were examined for the presence of antibodies to BVD virus (BVDV) annually during 1993-1997. The highest prevalence, 0.99% in 1994, declined to 0.37% in 1996; however, this favourable trend appeared to discontinue in 1997, where the prevalence remained at 0.41%. In 1993, sera of all individual animals from bulk milk antibody-positive herds were examined for the presence of these antibodies. Since 1994, only sera of animals from herds with a bulk milk absorbance reading greater than 0.250 in the EIA test were examined individually. Three geographic foci of BVDV antibody-positive dairy herds were resolved in 1994, one in the north-western, another in the eastern and a diffuse third in the southern part of Finland. A distinct limiting of the spread was apparent in 1997. Beef cattle were also studied during 1993-1997; in 1993 breeding units, in 1994 mainly beef suckler herds and in 1995-1997 serum samples of beef animals at slaughter were examined for the presence of antibodies to BVDV. The prevalence of seropositive herds in 1993 and 1994 was 30.2% and 3.2%, respectively, while the prevalence among slaughter animals ranged 0.8-1.6%. Seronegative animals in herds with > 50% of seropositive animals were examined for the presence of BVD-virus. A total of 40 dairy herds and two beef herds with viraemic (persistently infected, PI) animals was encountered during 1993-1997. A comprehensive control programme and a more specific, cooperatively funded eradication programme for dairy cattle were launched in 1994. These programmes most probably contributed to the decline in prevalence during 1994-1996.     

Bovine leukaemia virus infection in New Zealand cattle

Bovine Leukaemia Virus (BLV) infection in New Zealand cattle was investigated. In a national survey of 5000 sera from 500 herds, BLV antibody was not detected. An additional 1062 sera from 140 herds were tested and 3 sera were positive. In the herd of origin of one of these 3 sera, 22.6% of cattle were serologically positive for BLV. Where cases of bovine lymphosarcoma had been diagnosed, 38 of 39 herds tested were negative for BLV antibody. Within the remaining herd, 36% of cows tested were serologically-positive. BLV was isolated from 2 serologically positive cows in this herd.     

Bovine leukaemia virus infection in New Zealand cattle

Bovine Leukaemia Virus (BLV) infection in New Zealand cattle was investigated. In a national survey of 5000 sera from 500 herds, BLV antibody was not detected. An additional 1062 sera from 140 herds were tested and 3 sera were positive. In the herd of origin of one of these 3 sera, 22.6% of cattle were serologically positive for BLV. Where cases of bovine lymphosarcoma had been diagnosed, 38 of 39 herds tested were negative for BLV antibody. Within the remaining herd, 36% of cows tested were serologically-positive. BLV was isolated from 2 serologically positive cows in this herd.     

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.     

Epizootiologic study of bluetongue: virologic and serologic results

Heparinized blood and serum samples were obtained from 1,295 ruminants in herds or flocks with bluetongue virus (BTV) infection in 4 western states. Submissions were from herds or flocks with clinical bluetongue (BT), as well as from animals on premises with no history of BT disease. Insects, including Culicoides variipennis, were collected in areas enzootic for BT disease. Viral isolations were in 10-day-old embryonating chicken eggs that were then adapted to Vero cells for serotyping. Sera were tested from group-specific antibody to BTV by the micro agar gel precipitin (AGP) test. Viral isolations were from cattle (81), sheep (122), goats (9), antelope (2), and C varipennis (5). There were 7 isolates of serotype 120, 114 of serotype 11, 42 of serotype 13, and 56 of serotype 17. In herds or flocks from which BTV was isolated, 51% of cattle, 56% of sheep, 21% of goats, and 52% of antelope had AGP antibodies. Virus was isolated from 43% of the cattle and 23% of the sheep that had no demonstrable evidence of AGP antibodies. Viral isolations were seasonal, occurring from August until December. Approximately 30% of the herds or flocks from which virus was isolated had more than one serotype of virus causing infection.     

Risk factors for Brucella spp. infection In dairy cattle farms in Asmara, State of Eritrea

A cross-sectional study was conducted to identify risk factors for herd infection by Brucella spp. in dairy cattle in the suburbs of Asmara, Eritrea. Data were collected from 64 herds, randomly selected from a total of 99 herds with a minimum herd size of 9 cows. A questionnaire was used to gather data on management, hygiene and herd structure. Serum samples collected from all pregnant heifers, cows and bulls, were screened for Brucella infection by the Rose Bengal test (RBT), and all RBT-positive sera re-tested with the complement-fixation test (CFT) for confirmation. A seropositive herd was defined as one in which at least one animal tested positive in the CFT. There were 23 (36%) positive herds among the 64 studied. Both multiple logistic and multiple betabinomial regression modeling were used to analyze the data. Mixed-breed herds, compared to single (exotic)-breed herds, were found to be independently associated with increased herd seroprevalence (OR=5.2, 95% confidence interval 1.4–18.7) in the multiple logistic model with the herd infection status as the dependent variable. The importance of this variable was supported by the multiple betabinomial regression model (OR=3.3, 1.4–7.6) with animal-level prevalence within herd as the outcome variable. Both models also revealed the presence of a negative association between seropositivity and cattle stocking density.     

Neospora caninum seroprevalence in dairy cattle in central Thailand

The seroprevalence, in dairy cattle, of antibodies to Neospora caninum, the relationship between seropositivity and age (heifer versus cow), the relationship of herd infection with herd size and the relationship of herd infection with the presence of dogs on the farm were studied. The study involved 549 cows and 82 dogs in 59 dairy herds in Nakhon Pathom, Thailand. A competitive enzyme-linked immunosorbent assay (cELISA) with NC-specific monoclonal antibody was used to detect the NC antibodies in the sera. Individual and herd seroprevalence of NC were 5.5% (30/549) and 34% (20/59), respectively. No significant relationships between NC seropositivity with the age of the cows (heifer versus cow; P > 0.05) and between herd infection and the presence of dogs on the farm (P > 0.05) were found. Herd size significantly affected herd infection (P < 0.05) with higher infection in large than small herds (> or = 21 versus < or = 20 cows). Of 12 cows with a history of abortion, one was seropositive to NC. The seroprevalence of NC antibodies in dogs was 1.2% (1/82). This is the first NC seroprevalence study in dogs in Thailand. It was concluded that Neospora infection was more common at the herd level rather than the individual level in Thailand and the presence of dogs on the farm was not related to the level of herd infection. Caution should be taken in the interpretation of serological tests from the farm dogs.     

An estimated prevalence of Johne's disease in a subpopulation of Alabama beef cattle.

The objective of this study was to estimate the overall prevalence of animals that were infected with Mycobacterium avium ssp. paratuberculosis in a subpopulation of Alabama beef cattle. This was determined using a commercial enzyme-linked immunosorbent assay (ELISA) for the detection of M. avium ssp. paratuberculosis-specific antibodies in serum. Serum was collected from 79 herds that were participating in the Alabama Brucellosis Certification program. A total of 2,073 beef cattle were randomly tested by selecting 30 animals per herd in herds greater than 30 and selecting all animals in herds 30 and less for testing. It has been estimated that the commercial ELISA test used has a 60% sensitivity and a 97% specificity. Of the 79 herds tested, 29 herds were seronegative, 24 herds had 1-2 positive animals, and 26 herds had 3 or more seropositive animals. The average number of infected animals per positive herd was 3.3. In addition, a calculated minimum of 53.5% of the herds were identified as Johne's positive herds with a 95% confidence level. Of the total number of animals tested, 8.0% (166/2,073) of them were positive by the ELISA. After adjustments for test sensitivity and specificity and the proportion of animals sampled per herd, the true prevalence was calculated to be 8.75%. These data suggest that approximately 50% of the herds are infected with M. avium ssp. Paratuberculosis, and the overall prevalence of infection in Alabama beef cattle is approximately 8%, which correlates with other previously published regional estimates.     

Seroprevalence and associated risk factors of neosporosis in beef and dairy cattle in Italy

A cross-sectional serological survey for Neospora caninum was carried out on beef and dairy cattle in southern and northern Italy. A total of 111 herds and 1140 animals were tested using an ELISA assay (CHEKIT-Neospora) to detect anti-N. caninum antibodies. Management and individual data were collected and analysed both by linear and logistic multiple-regression models in order to find good predictors of the cattle seroprevalence and anti-N. caninum antibody level. At least one seropositive animal was found in 49 herds (44.1%), of which 31 (39.7%) from southern Italy and 18 (54.5%) from northern Italy. A total of 126 head of cattle (11%) were found to be seropositive and the seroprevalence was lower in southern (8.7%) than in northern Italy (16%). One of the best predictors of neosporosis seroprevalence in this study was the practice of self-rearing replacement heifers. Further risk factors were linked to higher stocking density, i.e. animals farmed in large herds and with no summer or permanent grazing practices were more likely to be seropositive than others. Farms with two or more dogs had higher herd seropositivity than farms with one or no dogs and this factor interacted significantly with the farm size and presence of poultry. Among individual characteristics, seropositivity was higher in animals sampled in mid- or late-pregnancy compared to animals either in early pregnancy or not pregnant. There was a significant interaction between the factors for pregnancy status and grazing practices. None of the epidemiological data recorded was a good predictor of the anti-N. caninum antibody level.     

Seroprevalence survey for Anaplasma card-test reactors in Louisiana,U.S.A., cattle

During 1982–1984 a total of 274 herds, or 11 175 cattle, throughout the State of Louisiana in south central U.S.A. were bled and their serum stored in a serum bank at −40°C; nine of these herds were bled twice. Using the rapid-card agglutination test these sera were tested for Anaplasma antibodies and the overall seroprevalence was 5.64% of the beef cattle seropositive and 4.27% of the dairy cattle.