Prevalence Of Seropositive Animals Research Articles

Epidemiological situation of Equine Infectious Anemia in the state of Paraná, Brazil

To assist decision making regarding the National Equine Health Program in the state of Paraná, a study was conducted to estimate the prevalence of infected farms and seropositive animals for Equine Infectious Anemia (EIA) and also identify possible risk factors for the disease. The state was divided into three regions, within which about 300 farms were randomly selected. On the selected farms, a minimum number of animals aged 6 months or older were examined to characterize them as infected or free of EIA. In the sampled farms, an epidemiological questionnaire was applied to investigate possible associations between the disease and its characteristics, including sanitary practices and livestock management. The test used was the Agar Gel Immunodiffusion Test. A total of 2818 equids from 889 farms were tested. In the state, the prevalence of infected farms was 1.55% [0.92; 3.00] and the prevalence of seropositive animals was 0.55% [0.27; 1.00]. Introduction of equids showed an association with EIA (OR=5.5 [1.9; 15.9]). Paraná equine owners should be alerted to the need to observe health precautions regarding EIA when introducing animals to their herd. In 2018, the sensitivity of the Surveillance System for EIA in Paraná was only 1.36%, probably insufficient to change the endemic balance of the disease, therefore, needs to be re-evaluated involving in the process all public and private agents interested in the subject.

Retrospective benefit-cost analysis of bovine brucellosis control in the state of Mato Grosso, Brazil.

From 2001, due to the launching of the National Program for the Control and Eradication of Brucellosis and Tuberculosis, Brazil began a series of studies aimed at the epidemiological characterization of bovine brucellosis in its federative units. In the state of Mato Grosso, studies conducted in 2003 and 2014 showed a reduction in the prevalence of infected herds from 41.2 % to 24 % and in the prevalence of seropositive animals from 10.2 % to 5.1 %. These results stemmed from the efficient heifer vaccination program with S19 implemented by the state. From this scenario, the present study quantified and compared the benefits and costs of bovine brucellosis control in the state through a financial analysis. When considering private and public costs, the Net Present Value (NPV) was estimated at US$ 37.5 million, the Internal Rate of Return (IRR) was calculated at 31 %, and the Benefit-Cost Ratio (BCR) was 2.3. When considering only the private costs, the NPV was US$ 51.3 million, the IRR was 46 % and the BCR was 3.43, indicating that the cattle producer in Mato Grosso had a return of US$ 3.43 for each US$ 1.00 invested. Therefore, the bovine brucellosis control actions carried out in the state of Mato Grosso between 2003 and 2014 were highly advantageous from the economic point of view. The most rational way to continue decreasing bovine brucellosis prevalences at low cost in the state is to maintain the heifer vaccination program, using the RB51 vaccine in addition to S19.

Retrospective Serosurvey of Three Porcine Coronaviruses among the Wild Boar (Sus scrofa) Population in the Campania Region of Italy.

The growing interest in porcine coronaviruses (CoVs) is due to both their negative effect on the swine industry and their propensity to mutate and overcome host barriers. Since information on CoVs in wild boar (Sus scrofa) is limited, especially in Italy, a serosurvey was conducted to assess the epidemiologic situation in the Campania region and to clarify the role of wild boar as reservoirs for enteric (porcine epidemic diarrhea virus [PEDV], transmissible gastroenteritis virus [TGEV]) and respiratory (respiratory coronavirus [PRCV]) swine CoVs. During the 2016-17 hunting season, serum samples were collected from 444 wild boars and tested for antibodies to enteric (PEDV, TGEV) and respiratory (PRCV) porcine CoVs by enzyme-linked immunosorbent assay. The highest seroprevalence in wild boars was for PEDV, with a positivity of 3.83% (95% confidence interval [CI] 2.05-5.6), whereas very low seroprevalences were found for TGEV and PRCV (0.67% positivity; 95% CI 0-1.44 in both cases). There was no statistical association between seropositivity to CoVs, sex, and location, whereas the prevalence of seropositive animals was positively correlated with young age (0-12 mo old). Our data confirm the presence of CoVs in wild boars in the Campania region. Our data are in agreement with the results of similar studies from other European countries, which attribute a minor role to wild boar in the transmission of these infections to domestic pigs. Our results suggest that continuous serologic surveys are necessary to monitor wild animals and detect emerging threats to livestock and humans.

Effect of vaccination on the apparent prevalence of bovine brucellosis in the state of Tocantins, Brazil

A cross-sectional study on the epidemiological situation of bovine brucellosis was carried out in the state of Tocantins to evaluate the effectiveness of its vaccination program. The state was divided into five regions, and a predetermined number of farms was randomly selected in each one. Females aged 24 months or older were randomly selected in each farm and diagnosed with brucellosis by serial serology (AAT and 2-ME). A total of 6,846 animals from 756 farms were examined. The prevalence of seropositive herds in the state was 6.42% [CI95%: 4.76-8.62], and the prevalence of seropositive animals was 2.21% [CI95%: 1.05-4.01]. The prevalence of seropositive herds was homogeneously distributed among regions. The 2002/2003 study estimated the prevalence of seropositive herds in the state to be 21.22% [CI95%: 19.33-23.11]. In conclusion, the vaccination program implemented in Tocantins, reaching vaccination coverage above 70% as of 2010, significantly reduced the prevalence of seropositive herds. Thus, continuing the vaccination program in the state is recommended, preferably increasing the quality of the processes involved, from commercialization to inoculation in animals, since immunization remains the most effective means to reduce the prevalence of brucellosis. In addition, animal replacement remains a major risk factor for bovine brucellosis in Tocantins since 20022003; therefore, the state must implement a strong health education program explaining to farmers the importance of testing animals for brucellosis before introducing them into their herds.

Prevalence and risk factors to <i>Leptospira</i> sp. infection in dogs attended at veterinary clinics in João Pessoa, Paraíba State, Northeastern Brazil

The aim of this study was to determine the prevalence and risk factors associated with Leptospira sp. in dogs attended at veterinary clinics in the city of João Pessoa, State of Paraíba, Northeast Brazil. A total of 384 blood samples from dogs from 34 veterinary clinics were used from April 2015 to May 2016. The diagnosis of Leptospira sp. was carried out through Microscopic Agglutination Test (MAT), using a collection of 20 pathogenic antigens and adopting a 1: 100 dilution as cutoff point. An epidemiological questionnaire was applied to the owners of the animals to obtain data to be used in the analysis of risk factors. The prevalence of seropositive animals was 11.7% (45/384), with reactions for serogroups Icterohaemorrhagiae (62.3%), Grippotyphosa (22.2%), Canicola (13.3%), Djasiman 2%) and Pomona (2.2%). The following risk factors were identified: age from 49 to 72 months (odds ratio = 2.74), Age > 72 months (odds ratio = 3.22), and monthly cleaning of the environment where the animals are kept (odds ratio = 10,70). It is concluded that dogs attended at veterinary clinics in João Pessoa are exposed to infection by Leptospira sp., with predominance of serogroups kept by wild animals, and it is suggested that the periodic cleaning of the environment where the animals are kept.

Prevalence of Coxiella burnetii antibodies in bulk milk and blood serum and associations with reproductive indices in cow dairy herds of Central and Northern Greece

For the first time in Greece, we investigated the prevalence of Coxiella burnetii antibodies in milk and sera from dairy cattle herds located at central and northern parts of the country. Eighty herds were initially voluntary enrolled in the study and a bulk milk sample from each farm was assayed by ELISA for C burnetii antibodies. According to antibody titre, herds were classified into 5 categories: negative and grades 1,2,3 and 4 (ascending scale). To assess the prevalence within farms, two herds from each category were selected and blood samples were collected for antibody assessment. In these herds, some reproductive indices were compared between farms; in addition, comparisons were made in paired seropositive and seronegative animals from one grade 3 herd. Twenty three herds (35%) were found positive, 21 being in categories 3 and 4. The prevalence of seropositive animals between herds varied from 4.9 to 46.3%, even from farms initially characterized as negative, some positive animals were detected. Between farms, no differences were detected in the abortion rate or in the mean number of artificial inseminations (AI) per pregnancy. Some differences were found in other reproductive indices that were impossible to be biologically interpreted under the light of C. burnetii level of infection. From the results presented here, we infer that C. burnetii infection is likely asymptomatic in dairy cows causing minimal -if any- economic losses to farmers. However, since the disease is a zoonotic one, its spread can easily occur, a systematic surveillance, in all ruminant species, for the restriction or eradication of the disease should be undertaken in national level.

Short communication: Correlation between within-herd antibody-prevalence and bulk tank milk antibody levels to Mycobacterium avium ssp. paratuberculosis using 2 commercial immunoassays

The objective of this study was to determine the correlation between the results obtained with the ELISA technique for antibodies to Mycobacterium avium ssp. paratuberculosis in serum and bulk tank milk at the herd level. For this purpose, 203 samples of bulk tank milk were analyzed with 2 commercial ELISA from dairy herds with a prevalence of seropositive animals that was also determined. In regard to the reference test (results in blood serum), the sensitivity of the bulk tank milk test to detect high-positive herds (≥10% seroprevalence) ranged from 85.7 to 71.4%. The specificity to detect herds with no seropositive animals ranged from 70.5 to 53%. In a quantitative approach, Pearson correlation coefficients, reported as a measure of the linear association between herd seroprevalences and transformed optical density values recorded in bulk tank milk, were 0.39 and 0.54 for the studied ELISA. Although the test results were relatively fairly correlated with the within-herd prevalence, the practical utility of bulk tank milk testing for Mycobacterium avium ssp. paratuberculosis seems limited, especially regarding specificity.

Herd-level prevalence and risk factors for bovine viral diarrhea virus infection in cattle in the State of Paraíba, Northeastern Brazil

Serological surveys based on a planned sampling on bovine viral diarrhea virus (BVDV) infection in Brazilian cattle herds are scarce. A cross-sectional study was carried out to determine herd- and animal-level seroprevalences and to identify risk factors associated with herd-level seroprevalence for BVDV infection in the State of Paraíba, Northeastern Brazil, from September 2012 to January 2013. The state was divided into three sampling strata, and for each stratum, the prevalence of herds infected with BVDV and the prevalence of seropositive animals was estimated by a two-stage sampling survey. In total, 2443 animals were sampled from 478 herds. A virus-neutralization test was used for BVDV antibody detection. A herd was considered positive when at least one seropositive animal was detected. The herd- and animal-level prevalences in the State of Paraíba were 65.5% (95% confidence interval (CI) = 61.1-69.7%) and 39.1% (95% CI = 33.1-45.6%), respectively. The frequency of seropositive animals per herd ranged from 10 to 100% (median of 50%). The risk factors identified were as follows: more than six calves aged ≤12 months (odds ratio (OR) = 3.72; 95% CI = 2.08-6.66), animal purchasing (OR = 1.66; 95% CI = 1.08-2.55), pasture rental (OR = 2.15; 95% CI = 1.35-3.55), and presence of veterinary assistance (OR = 2.04; 95% CI = 1.10-3.79). Our findings suggest that the implementation of control and prevention measures among farmers, with the aim of preventing dissemination of the agent in the herds, is necessary. Special attention should be given to addressing the identified risk factors, such as sanitary control prior to animal purchasing and to discourage the pasture rental, as well as to encourage the vaccination in the herds.

Canine visceral leishmaniasis in an urban setting of Southeastern Brazil: an ecological study involving spatial analysis.

BackgroundThe physical characteristics of the environment influence the composition, distribution and behavior of the vectors and mammalian hosts involved in the transmission of visceral leishmaniasis (VL), thereby affecting the epidemiology of the disease. In Brazil, urbanization of human VL is a recent phenomenon and represents an issue of particular concern to local health authorities. The present study aimed to establish the degree of spatial dependency between canine and human VL in the municipality of Divinópolis, Minas Gerais, Brazil, and to identify priority risk areas in which stricter control measures should be implemented.MethodsThe selected canine population comprised 3,652 dogs distributed within 11 strata and 1,247 urban blocks. Serum samples were collected between March 2013 and February 2014. Serodiagnosis of dogs was performed using the enzyme-linked immunosorbent assay and the indirect fluorescent-antibody test. The blocks sampled for canine VL and the addresses of the 16 confirmed cases of human VL notified in Divinópolis during the period 2007–2013 were georeferenced. Spatial analysis of the data was performed using Kernel density estimation, Ripley’s bivariate K-function and directional distribution methods.ResultsThe overall prevalence of seropositive animals was 4.63% (range 3.95 - 5.31) (n =169) and varied in different strata between 0.9 (range 0.0 - 1.91) and 8.73% (range 5.65 - 11.81). A positive spatial dependency was detected between human and canine VL in which the occurrence of human cases of the disease tended to concentrate in locations that were close to areas with a higher incidence of canine VL. The priority risk area could be clearly distinguished from Kernel density estimation and standard deviational ellipse plots in which the human VL ellipse was totally enclosed within the canine VL ellipse.ConclusionsThe results presented herein will enable the Municipal Health Office of Divinópolis to devise a more effective management plan for human VL in which specific strategies would be applied to areas presenting different levels of risk. This spatial evaluation of leishmaniasis model could be applied in other urban areas of Brazil.

Canine visceral leishmaniasis in an urban setting of Southeastern Brazil: an ecological study involving spatial analysis

The physical characteristics of the environment influence the composition, distribution and behavior of the vectors and mammalian hosts involved in the transmission of visceral leishmaniasis (VL), thereby affecting the epidemiology of the disease. In Brazil, urbanization of human VL is a recent phenomenon and represents an issue of particular concern to local health authorities. The present study aimed to establish the degree of spatial dependency between canine and human VL in the municipality of Divinópolis, Minas Gerais, Brazil, and to identify priority risk areas in which stricter control measures should be implemented. The selected canine population comprised 3,652 dogs distributed within 11 strata and 1,247 urban blocks. Serum samples were collected between March 2013 and February 2014. Serodiagnosis of dogs was performed using the enzyme-linked immunosorbent assay and the indirect fluorescent-antibody test. The blocks sampled for canine VL and the addresses of the 16 confirmed cases of human VL notified in Divinópolis during the period 2007-2013 were georeferenced. Spatial analysis of the data was performed using Kernel density estimation, Ripley’s bivariate K-function and directional distribution methods. The overall prevalence of seropositive animals was 4.63% (range 3.95 - 5.31) (n =169) and varied in different strata between 0.9 (range 0.0 - 1.91) and 8.73% (range 5.65 - 11.81). A positive spatial dependency was detected between human and canine VL in which the occurrence of human cases of the disease tended to concentrate in locations that were close to areas with a higher incidence of canine VL. The priority risk area could be clearly distinguished from Kernel density estimation and standard deviational ellipse plots in which the human VL ellipse was totally enclosed within the canine VL ellipse. The results presented herein will enable the Municipal Health Office of Divinópolis to devise a more effective management plan for human VL in which specific strategies would be applied to areas presenting different levels of risk. This spatial evaluation of leishmaniasis model could be applied in other urban areas of Brazil.

Bovine viral diarrhea virus

The aim of the present study was to establish a relationship between the results obtained using the enzyme-linked immunosorbent assay (ELISA) technique for antibodies in blood serum and milk at herd level. For this purpose, 325 samples of bulk tank milk were analyzed with 4 antibody ELISAs from dairy herds with a prevalence of seropositive animals; seroprevalence was also evaluated. Data were arranged to analyze the sensitivity of the bulk tank milk test to detect herds with high risk of active infection (>65% seroprevalence) and the specificity to detect those with very few (<5%) or no (0%) seropositive animals, respectively. The sensitivity values ranged from 0.92 to 0.70 and the specificity from 0.83 to 0.54 to detect free herds (0% seroprevalence) and from 0.88 to 0.77 to detect herds with <5% of seropositive animals. In a quantitative approach, Pearson correlation coefficients, reported as a measure of linear association between herd seroprevalence and transformed optical density values recorded in bulk tank milk, ranged from 0.71 to 0.86. According to these results, the 4 antibody ELISAs would be valid tests for carrying out a herd classification program using milk samples.

Toxoplasma gondii in Switzerland: A Serosurvey Based on Meat Juice Analysis of Slaughtered Pigs, Wild Boar, Sheep and Cattle

Toxoplasmosis is one of the most important zoonotic diseases worldwide and is caused by the protozoan Toxoplasma gondii. Besides vertical infection during pregnancy, humans can get infected post-natally either by peroral uptake of sporulated Toxoplasma oocysts or by ingestion of tissue cysts upon consumption of raw or undercooked meat. The aim of this study was to approximate the risk of human infection via meat consumption by estimating the seroprevalence of T. gondii in slaughtered animals in Switzerland and to compare data with prevalences assessed 10 years ago. The study included pigs, cattle, sheep and wild boar of different age groups and housing conditions whenever possible and applicable. A P-30-ELISA was used to detect T. gondii-specific antibodies and to determine seroprevalences in meat juice of slaughtered animals. A total of 270 domestic pigs (120 adults, 50 finishing, 100 free-ranging animals), 150 wild boars, 250 sheep (150 adults, 100 lambs) and 406 cattle (47 calves, 129 heifers, 100 bulls, 130 adult cows) were tested. Seropositivity increased with the age of the assessed animals. Independent of the age-group, the overall seroprevalence was lowest in wild boars (6.7%), followed by pigs (23.3%), cattle (45.6%) and sheep (61.6%), respectively. Conventional fattening pigs and free-ranging pigs surprisingly had comparable seroprevalences (14.0% and 13.0%, respectively). Unlike in other European countries, where generally a decrease in the number of seropositive animals had been observed, we found that the prevalence of seropositive animals, when compared with that of 10 years ago, had increased for most species/age groups. Conclusively, the results demonstrated a high seroprevalence of T. gondii in animals slaughtered for meat production and revealed that increasing age of the animals is a more important risk factor than housing conditions in Switzerland.

The first outbreak of brucellosis in the region of Sabac

In Serbia brucellosis is a primary disease of the animals in the southern parts of the country. The aim of this study was to describe the first outbreak of human and animal brucellosis in the region of Sabac, Serbia. An epidemiological investigation was conducted to identify a source of outbreak and the ways of transmission of brucellosis infection in human population. A descriptive and analytical epidemiological methods (cohort study) were used. Additional data included monthly reports of the infectious diseases from the Institutes of Public Health and data from the Veterinary Specialistic Institute in Sabac. The serological tests for human brucellosis cases were performed in the Laboratory of the Military Medical Academy; laboratory confirmation of animal brucellosis cases was obtained from the reference laboratory of the Faculty of Veterinary Medicine, Belgrade. Twelve cases of brucellosis were recorded from February 9 to September 1, 2004. Total attack rate was 8.1% (7.5% of males, 14.2% of females). Relative risk (RR) of milk consumption was 8.9 (95% confidence interval: 1.63-13.38), and RR for direct contact with animals was 14 (95% confidence interval: 3.5-55.6). The prevalence of seropositive animals in 33 villages of the Macva region accounted for 0.8%. Regarding animal species, sheep were predominant--264 (95.7%). Out of a total number of seropositive animals, ELISA results were positive in 228 (88.7%) of them. As contact epidemics generally last longer, it is probable that the implemented measures of outbreak control did reduce the length of their duration.

TESTING THE PREVALENCE OF BVDV INFECTION IN LARGE AND SMALL CATTLE HERDS IN SOUTH BACKA AND SREM DISTRICT

Bovine viral diarrhoea (BVD) is a worldwide viral cattle disease. Percentage of seropositive animals, especially in the countries with intensive cattle breeding ranges from 60-90%. This infection on our epizootiology area, as well as on area in our surrounding, was for the first time described by OEuriåkoviñ et al. (1966) based on clinical pictures and pathomorphological findings. This was proved by antibody detection by Cvetnić et al. (1968). In the last few years a large number of serology examination was done on the presence of BVDV infection in our area. In 2004 an examination on virus neutralisation antibodies in sera of breeding dairy cattle older than 6 months was carried for the purpose of determining the prevalence of BVDV infection in large and small herds in Southern Bačka and Srem districts. There were 7577 sera samples from small herds, out of which 3457 were from Southern Bačka (26.31% out of total population in all 9 municipalities), and there were 4120 samples from Srem district (25.17% out of total population in all 8 municipalities). The examination included the animals from all settlements (156). From large cattle herds there were 3019 sera samples, out of which 2721 were from 18 large farms in Southern Baåka (38.65% out of total population), and 298 from 4 large farms in Srem district (29.22% out of total population). This examination encompassed animals from 22 large farms on this area. Virus neutralisation test (VN) was carried out according to the standard procedure described in ’’Manual of Diagnostic Tests and Vaccines for Terrestrial Animals’’ Office International des Epizooties (2004) with slight modifications. For test NADL strain of BVD virus and MDBK cell culture were used. The sera were examined in double dilution from 1:2 to 1:512. Virus neutralisation antibodies for NADL strain BVDV were detected in 1833 (24.19%) in the samples from small herds. Out of this number there were 1082 (31.30%) seropositive animals from Southern Baåka and 751 (18.53%) from Srem district. The largest number of seropositive animals in Southern Baåka district were detected in Titel municipality (68.07%) and the lowest in Bački Petrovac municipality (6.63%). In Srem district the largest number of seropositive animals was in Beoåin municipality (34.16%) and the lowest in Irig municipality (7.62%). When comparing all the settlements, the percentage of BVDV seropositive animals ranged from 0% (i.e. settlements with no seropositive animals) up to 86.67% (Krnjeãevci). Virus neutralisation antibodies for BVDV NADL strain were detected in 1667 (55.22%) samples from large cattle herds. Out of this number there were 1500 (55.13%) seropositive animals from Southern Bačka, and 167 (56.04%) seropositive animals from Srem district. The prevalence of seropositive animals in large herds from Southern Baåka district ranged from0%(5 large herds) up to 96.61%. High prevalence (70%) was detected in 7 out of 18 examined herds. The prevalence of seropositive animals originating from large herds in Srem district ranged from 0% (1 large herd) to 96.96%. High prevalence (70%) was detected in 2 out of 4 examined herds. Detected variation in the percentage of seropositive animals in some areas and herds most probably is the result of animal origin and management on the farms, i.e. movement of animals with introduction of new animals into a herd, what also means that the virus enters into a herd and outbreaks of BVDV infection occur. The titre ofVNantibodies in a certain number of animals, especially on certain areas and in some herds ranged up to 1:512 and even more, what was a clear indication of current or recent presence of persistently infected animals in these herds. High percentage of seropositive animals (70%) in 9 large herds most probably is the result of uncontrolled animal movement, entering of BVD virus and frequent outbreaks of BVDV infections in these herds, but this also indicates probable presence of persistently infected animals in the herds. The obtained results point on high prevalence of BVD infection in the examined area. This prevalence is not equal, what point on existence of areas where the infection is not present, or is present only sporadically.

Soroprevalência e fatores de risco para a língua azul em carneiros das mesorregiões do Sertão e da Borborema, semi-árido do Estado da Paraíba, Brasil

Neste estudo foi determinada a prevalência de anticorpos contra o vírus da língua azul em carneiros das mesorregiões do Sertão e da Borborema, semi-árido do Estado da Paraíba, bem como foram identificados os fatores de risco associados à infecção. A amostragem foi delineada para a determinação da prevalência de propriedades positivas (focos) e de animais soropositivos por mesorregião. Foi realizada uma seleção aleatória de unidades primárias, composta por 189 propriedades no Sertão e 100 propriedades na Borborema. Dentro das unidades primárias, foram amostrados todos os carneiros (unidades secundárias), resultando em 321 animais no Sertão e 185 na Borborema. Na ocasião da coleta, foi aplicado um questionário epidemiológico por propriedade. Para o diagnóstico sorológico, foi utilizada a prova de imunodifusão em gel de ágar (IDGA), com antígeno produzido na Escola de Veterinária da Universidade Federal de Minas Gerais). Uma propriedade foi considerada foco quando apresentou pelo menos um animal soropositivo. Na mesorregião do Sertão, as prevalências de focos e de animais soropositivos foram de 11,6% [7,8% - 17,1%] e 8,4% [5,7% - 12,3%], respectivamente. Na mesorregião da Borborema, a prevalência de focos foi de 0,0% [0,0% - 3,6%] e a prevalência de animais soropositivos foi de 0,0% [0,0% - 2,0%]. Os fatores de risco associados à língua azul foram a não realização de higiene das instalações (OR = 5,51) e a vermifugação dos animais duas a quatro vezes ao ano (OR = 4,44).

Seroprevalence of bvdv in cattle of different ages on 17 dairy farms in western England

Seroprevalence of <scp>bvdv</scp> in cattle of different ages on 17 dairy farms in western England

A simple, rapid and reliable enzyme-linked immunosorbent assay for the detection of bovine virus diarrhoea virus (BVDV) specific antibodies in cattle serum, plasma and bulk milk

To detect Bovine Virus Diarrhoea Virus (BVDV)-specific antibodies in cattle serum, plasma and bulk milk, a simple, reliable and rapid blocking ELISA ("Ceditest") has been developed using two monoclonal antibodies ("WB112" and "WB103") directed to different highly conserved epitopes on the non-structural peptide NS3 of pestiviruses. The test can be performed at high reproducibility using undiluted samples. In testing 1000 field serum samples, the ELISA showed a specificity and a sensitivity relative to the virus neutralization test of 99% and 98%, respectively. The blocking ELISA is able to detect specific antibodies in serum obtained 12 days after an acute infection and in serum of vaccinated and challenged animals. A frequency distribution diagram, obtained by testing almost 1800 random Dutch field serum samples, showed a clear separation between a negative population (maximum frequency of the % inhibition at −5%) and a positive population (maximum frequency of the % inhibition at 95%). Based on these data, the prevalence of seropositive animals was 65% (95% confidence interval: 63%–67%). By exchanging plasma- and bulk milk samples between two laboratories (The Netherlands and Denmark), a good overall agreement was found between results obtained with the Ceditest and those obtained with the Danish blocking ELISA as used in the Danish BVDV eradication programme. The results indicate that BVDV infections can reliably be diagnosed by the Ceditest ELISA and that the test is suitable for use in large scale screening and eradication programmes.

Prevalence of bovine virus diarrhoea virus infection in Belgian white blue cattle in Southern Belgium

SummaryA study was conducted in Southern Belgium to determine the prevalence of bovine viral diarrhoea virus (BVDV) infection in Belgian White Blue herds. Blood samples were taken from 9685 cattle, representing all the stock on 61 farms, by local veterinarians to screen for persistently infected animals and to determine their serological status against BVDV. Some of the herds (42.5%) were selected because of a prior positive diagnosis of BVDV or on the grounds of suspicion of BVD. A capture enzyme‐linked immunosorbent assay (ELISA) was used to test for antigen. The prevalence of persistently infected animals was 0.75% overall and 1.46% in the 27 herds with at least one persistently infected animal. The prevalence of seropositive animals was determined with a competitive antibody ELISA and was found to be 65.5% for the animals as a whole but 53.8% for the herds without positively infected animals and 76.6% for the herds with at least one such animal. All the herds contained seropositive animals.

Études épidémiologiques sur la dermatophilose dans les Antilles

Dermatophilosis is one of the most important diseases of domestic ruminants in the Caribbean islands where the clinical disease has been shown to be associated with the presence of the tick Amblyomma variegatum. Seroepidemiological studies were conducted to clarify the epidemiology of the disease in the region with a particular attention paid to the role of A. variegatum. A bank of 1300 cattle sera from the Lesser Antilles was screened by ELISA for the presence of antibodies to Dermatophilus congolensis. It appeared that seropositive animals do exist in islands non infested by A. variegatum and where dermatophilosis is never or seldom seen. Moreover, there was no significant difference in prevalence of seropositive animals between tick-infested and non infested areas of Martinique and Saint Lucia, 2 islands partly infested by the tick, and where dermatophilosis is only seen in tick-infested areas. Prevalence was low in small islands with a dry climate. This confirms experimental data showing that A. variegatum is not necessary for the transmission of D. congolensis which is widespread in most of the islands. High concentrations of prostaglandin E2 (between 151 and 377 ng/ml) and prostacyclin (between 124 and 134 ng/ml) found in the saliva of females A. variegatum strongly suggest that the tick could favour the development of the lesions through an immunomodulating activity of its saliva. However, despite some success in reproducing dermatophilosis on goats simultaneously infested with adult A. variegatum and scarified with Dermatophilus, no difference was observed between naturally resistant Creole cattle and very susceptible Brahman animals using the same model. The lesions of dermatophilosis remained very mild on animals of both breeds.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of bovine virus diarrhoea (BVD) in 19 Danish dairy herds and estimation of incidence of infection in early pregnancy

A survey of all cattle in 19 Danish dairy herds with unknown status of bovine virus diarrhoea virus (BVDV) infection showed that 1.4% of the animals were persistently infected with BVDV. Persistently infected animals were detected in ten herds (53%), in numbers varying from one to ten animals per herd. The prevalence of neutralizing antibody-seropositive animals in herds with one or more persistently infected animals was 87%, whereas the prevalence in herds without persistently infected animals was 43%. Seropositive animals were found in all herds. There was a logarithmic relationship between age and prevalence of seropositive animals. The the-oretical risk of fetal infections occurring during the first 3 months of pregnancy was estimated to be 3.3%, close to the observed prevalence (2.9%) of persistently infected animals less than 1 year of age.