Indirect ELISA (iELISA) standardization for the diagnosis of bovine enzootic leukosis / Padronização de um ELISA indireto (iELISA) para diagnóstico da leucose enzoótica bovina

Enzootic bovine leukosis (EBL) is an infectious disease caused by bovine leukemia virus (BLV) that affects cattle worldwide. Agar gel immunodiffusion (AGID) was the reference test for EBL diagnosis for many years, but enzyme-linked immunosorbent assay (ELISA) showed higher sensitivity, was faster to perform, and resulted in an objective reading. However, the importation of ELISA kits is lengthy and expensive, and currently, no AGID kits are available in Brazil. The aim of this work was to standardize an indirect ELISA (iELISA) for EBL diagnosis using BLV antigens produced in Tadarida brasiliensis lung (Tb1Lu) cells, which are Bovine viral diarrhea virus (BVDV) free, unlike fetal lamb kidney (FLK) cells, currently used for this purpose. Following standardization, iELISA results were compared with those obtained by AGID and the commercial Chekit Leucose-Serum ELISA. Compared to AGID, iELISA had 94,44% sensitivity, 75.68% specificity, 79.10% positive predictive value (PPV) and 93.30% negative predictive value (NPV), with 84% concordance and a Kappa index of 0.699. Compared to the Chekit Leucose-Serum ELISA, iELISA showed 92.60% sensitivity, 87.09% specificity, 90.27% PPV and 90,00% NPV, with 90.27% concordance and a Kappa index of 0.801. Taking into account the high agreement with the traditional tests and the absence of non-specific reactions with BVDV, the developed assay could be used as diagnostic method to control EBL in Brazil.(AU)

A leucose enzoótica bovina (LEB) é uma doença infecciosa natural dos bovinos com distribuição mundial causada pelo "bovine leukemia virus" (BLV). A imunodifusão em gel de ágar (IDGA) foi considerada por muitos anos o teste de eleição, porém ensaios imunoenzimáticos (ELISA) apresentam sensibilidade mais elevada e leitura mais rápida e objetiva. No entanto, a importação de kits de ELISA é um processo dispendioso e demorado, e atualmente não há kits de IDGA comercialmente disponíveis no Brasil. Desta forma, o objetivo deste trabalho foi padronizar um ELISA indireto (iELISA) para diagnóstico da LEB utilizando antígenos produzidos a partir do cultivo do BLV em linhagem celular Tadarida brasiliensis "lung" (Tb1Lu) livre de "bovine viral diarrhea virus" (BVDV), diferentemente do que acontece com as linhagens "fetal lamb kidney" (FLK) atualmente utilizadas na produção desses antígenos para uso em ensaios sorológicos. Após a padronização do iELISA, os resultados foram comparados com aqueles obtidos por IDGA e pelo ELISA comercial "Chekit Leucose-Serum". Comparado ao IDGA, o iELISA apresentou 94,44% de sensibilidade, 75,68% de especificidade, valor preditivo positivo (VPP) de 79,1% e valor preditivo negativo (VPN) de 93,3%, com concordância entre os testes de 84% e o índice Kappa 0,699. Quando comparado ao ELISA "Chekit Leucose-Serum", o iELISA apresentou sensibilidade de 92,6%, especificidade de 87,09%, VPP de 90,27% e VPN de 90%, com concordância de 90,27% e o índice Kappa 0,801. Portanto, devido à alta concordância com os testes tradicionais e ausência da ocorrência de reações inespecíficas com BVDV, o ensaio desenvolvido pode ser utilizado como ferramenta diagnóstica para o controle da LEB no Brasil.(AU)

Ocorrência do vírus da artrite encefalite caprina (CAEV) em cabras leiteiras produzidas em sistema intensivo confinado no estado de Minas Gerais / Occurrence of caprine arthritis encephalitis virus (CAEV) in dairy goats produced in an intensive confined system in the state of Minas Gerais, Brazil

Objetivou-se no estudo identificar a ocorrência de infecção pelo vírus da artrite encefalite caprina (CAEV) em propriedades produtoras de leite caprino com sistema intensivo no estado de Minas Gerais. Foram avaliadas cinco propriedades, localizadas em cidades distintas, totalizando 1072 animais, sendo 48 machos e 1024 fêmeas de diferentes faixas etárias, das raças Toggenburg, Alpina e Saanen. O método de diagnóstico utilizado foi o de imunodifusão em ágar gel (IDGA), para detecção de anticorpos anti-CAEV, por ser o diagnóstico preconizado pela Organização Mundial de Saúde Animal (OIE). A ocorrência de anticorpos anti-CAEV nas propriedades estudadas foi de 49,5% (531/1072), entretanto a mesma variou de acordo com a propriedade. Foram observados os seguintes resultados por propriedade: propriedade 1 = 69,6% (156/224); propriedade 2 = 41,5% (47/113); propriedade 3 = 40,3% (63/156); propriedade 4 = 24,6% (18/73) e propriedade 5 = 48,8% (247/506). Do total de machos avaliados, 14,5% (7/48) apresentaram sorologia positiva. De acordo com os resultados, uma alta ocorrência de animais soropositivos foi identificada no estado de Minas Gerais, o qual possui um dos maiores rebanhos de cabras leiteiras do Brasil. Portanto, salienta-se a necessidade de se adotar medidas estratégias sanitárias para o controle da CAE, como a realização de exames rotineiros nas propriedades e a separação de animais infectados dos sadios. A exclusão de reprodutores positivos nas propriedades também é uma medida de controle, pois já foi demonstrado que estes são fontes de infecção importantes.(AU)

The objective of the present study was to identify the occurrence of caprine arthritis encephalitis virus (CAEV) infection in dairy goat farms with intensive system in Minas Gerais State. Five properties were evaluated, totaling 1072 animals, being 48 males and 1024 females of different ages and breeds (Toggenburg, Saanen and Alpine). The diagnostic method used was the agar gel immunodiffusion (AGID) test, to detect antibodies anti-CAEV, which is the diagnostic test recommended by World Organization for Animal Health - OIE. The occurrence of anti-CAEV antibodies in the properties was 49.5% (531/1072), however varied according to the farm. The anti-CAEV antibodies detection varied according to the property: Farm 1 = 69.6% (156/224); farm 2 = 41.5% (47/113); farm 3 = 40.3% (63/156); farm 4 = 24.6% (18/73) and farm 5 = 48.8% (247/506). Of the total sampled males, 14.5% (7/48) were serologically positive. According to the results, there is a high occurrence rate of CAEV-seropositive animals in Minas Gerais, which has one of the largest Brazilian dairy goat herds. Therefore, it is essential to adopt strategies for CAE control, such as a routine of diagnostics tests in the properties and the separation of healthy from infected goats. The elimination of positive breeding goats in the properties is also a measure of control, because it has been shown that these are an important route of CAEV transmission in dairy farms.(AU)

Identification of virulence factors by multiplex PCR in Escherichia coli isolated from calves in Minas Gerais, Brazil.

In this study, multiplex PCR was employed to investigate the virulence factors of Escherichia coli strains isolated from 60-day-old calves. Faecal samples were collected from 54 calves at 12 dairy farms in the state of Minas Gerais, Brazil. A total of 156 isolates were obtained after culture and microbiological isolation and were tested by multiplex PCR for the presence of genes encoding toxins (Stx1, Stx2 and STa) and adherence factors (intimin, F41 and F5). Seventy of 156 isolates were positive for at least one virulence factor: ten (14.3 %) from diarrhoeic animals and 60 (85.7 %) from healthy calves. The virulence markers identified were: Stx1 (82.8 %), eae (24.3 %), F41 (11.4 %), F5 (10 %), STa (4.28 %) and Stx2 (4 %). In diarrhoeic animals, Stx1 (70 %) and F41 (30 %) were identified, while Stx1 (83.3 %), eae (28.3 %), F41 (8.3 %), F5 (11.6 %), STa (5 %) and Stx2 (1.6 %) were detected in isolates from healthy calves. Mixed infections with pathotypes Shiga toxin-producing E. coli (STEC)/enteropathogenic E. coli, STEC/enterohaemorrhagic E. coli and STEC/other (eae/F5, Stx1/STa) were detected in five healthy calves. Pathogenic E. coli were identified in 59.26 % of all calves and on 75 % of the dairy farms studied, not only in diarrhoeic (five of six) but also in healthy calves (27 of 48), which demonstrates the importance of this agent in the aetiology of diarrhoea in calves in the state of Minas Gerais.

Orbivirus infections in collared peccaries (Tayassu tajacu) in southeastern Brazil.

We surveyed 49 free-living collared peccaries (Pecari tajacu) in Brazil for antibodies against bluetongue virus (BTV) and porcine circovirus 2 (PCV2). Antibodies against BTV were detected in 19/49 (39%) samples. All samples were negative for PCV2. The importance of antibodies to BTV in collared peccaries remains to be determined.

Distribution of antibodies against porcine circovirus type-2 (PCV2) in single site and multi-site farrow-to-finish farms in Brazil.

A comparative serologic study was performed in seven single site (SS) farrow-to-finish farms and four multi-site (MS) farrow-to-finish farms, with or without post-weaning multisystemic wasting syndrome (PMWS). In each farm, 30 blood samples were collected for each category of the production cycle: sows, farrowing crate, nursery, grower pigs, and finishing pigs. Sera were evaluated for the presence of antibodies to porcine circovirus type-2 (PCV2) via immunoperoxidase monolayer assay. Serologic profiles for PCV2 were different between SS and MS farms. Seroconversion following the decline in maternal antibodies occurred at a later stage on SS farms (grower pigs) than MS farms (nursery pigs). MS farms tended to have lower antibody titers than SS farms in the categories of sow, piglet, and nursery, while higher antibody titers were found in grower pigs. Characterization of serologic profiles for different farms may provide important information for the adoption of vaccination programs.