Brucellosis is a disease of socio-economic and zoonotic importance worldwide. In animals it is associated with the ingestion of feed that is contaminated with cyetic material from aborting herd-mates, while in humans it is associated with the consumption of unpasteurised milk and dairy products from infected animals. It may also be acquired from contact with infected material of animal origin by farmers, veterinarians, and abattoir and laboratory workers. Brucellosis was first reported in South Africa in the late nineteenth century. It is still present in the country today, with reported annual losses of at least R 300 million, and a national annual incidence of 5 000 cases in humans. The global incidence of human brucellosis is about half a million infections annually. As the incidence of human brucellosis is directly associated with prevalence in animals, control of animal brucellosis is emphasised. Veterinary control is compromised by the chronic nature and the variable incubation period of the disease, with an estimated up to 15% of cattle in infected herds aborting before sero-conversion. Latency, which involves about 5% of calves born from infected dams, is also problematic as these infected animals often test seronegative, only to seroconvert in the peri-parturient period, thus allowing opportunity for disease spread within and between herds before diagnosis is made. In addition, the currently used serological tests are at times unable to distinguish brucellosis from cross-reacting antibodies from other infections or brucellosis vaccines. x It was the objective of this study to investigate, under South African conditions, the value of the brucellin skin test (BST) in improving the sensitivity and specificity of the currently used serological tests. It has proved a valuable additional test in diagnosing early and latent infections as well as in differentiating brucellosis from cross-reacting organisms in unvaccinated cattle in Europe. The study also evaluated the benefit of replacing some of the currently used serological assays with the fluorescence polarisation assay (FPA). The FPA, a rapid and homogenous serological test with only a few operational steps, has been validated and is in current use in Canada. The study was carried out in Mpumalanga Province, on herds selected to reflect prevailing South African farming conditions. These herds were divided into certified Brucella abortus-negative herds (608 head) for the estimation of BST specificity, and confirmed B. abortus-infected herds (845 head) for the estimation of BST sensitivity. The results obtained indicated the BST had a specificity of 99.18%, and a relative sensitivity of 42.86%. However, 65.38% of BST-positive animals were negative on serology. When the high specificity is considered, together with the experiences of other researchers who found that the skin test became positive earlier than serological tests, these animals may be assumed infected. It is concluded that the BST is a valuable addition to the panel of diagnostic tests currently used to identify infected herds and individuals in South Africa. The FPA, with a relative sensitivity of 93.65% and a specificity of 98.85%, can potentially be of use as a screening test under South African conditions. / Dissertation (MSc)--University of Pretoria, 2012. / gm2014 / Veterinary Tropical Diseases / unrestricted

O vírus da diarreia viral bovina (BVDV) é responsável por diferentes síndromes que afetam principalmente bovinos em todo o mundo, causando grandes perdas econômicas. A principal medida de controle desta infecção é a detecção e retirada dos animais persistentemente infectados (PI) do rebanho. O presente trabalho analisou a infecção persistente por este vírus em um rebanho bovino de gado de corte, vacinado com vacina inativada contra BVDV tipo 1 e localizado no Município de Viamão, Rio Grande do Sul, de novembro de 2007 a maio de 2009. Para a triagem de animais PI, amostras de soro, sangue com EDTA e fragmentos de orelhas foram coletadas principalmente de animais com idade entre 2-3 meses. Os testes utilizados compreenderam o isolamento viral, a transcrição reversa seguida da reação em cadeia da polimerase (RT-PCR), a imuno-histoquímica (IHQ) e a sorologia pelo ensaio imunoenzimático (ELISA). De 1300 animais da propriedade, coletou-se 179 amostras e em 6 se identificou a infecção persistente pelo BVDV tipo 2 não citopático (ncp). Os principais sinais clínicos verificados na propriedade englobavam nascimento de bezerros fracos, grande número de animais com retardo no crescimento e catarata congênita uni e bilateral. As principais lesões observadas em 5 animais necropsiados consistiam de aumento dos linfonodos mesentéricos, evidenciação das placas de Peyer e em um animal verificou-se pododermatite com lesões crostosas no plano nasal e na região periocular. Os achados microscópicos caracterizavam-se principalmente por infiltrado mononuclear na lâmina própria do intestino delgado e rarefação linfoide com infiltrado histiocitário nos centrofoliculares de linfonodos e nas placas de Peyer. A demonstração do antígeno viral nos 5 animais avaliados ocorreu principalmente em: queratinócitos da epiderme , no epitélio de folículos pilosos e células dendríticas da derme de orelhas e pele; histiócitos e em linfócitos dos linfonodos; células foliculares da tireoide; no citoplasma de neurônios e em menor escala, em células da micróglia no córtex cerebral e no hipocampo. A análise de pools de soro de animais suspeitos pelo RT-PCR em conjunto com a avaliação imuno-histoquímica de biópsia de orelhas mostraram bons resultados e podem ser úteis como método de triagem de infecções persistentes em rebanhos, inclusive em animais menores de 6 meses de idade por não sofrerem interferência de anticorpos maternos. A retirada e eliminação dos animais PI surtiram efeitos positivos na propriedade, entretanto novas coletas devem ser realizadas em 2010. / Bovine viral diarrhea virus (BVDV) is responsible for different syndromes that affect mainly cattle worldwide, causing important economic losses. The main control measure for this infection is the detection and removal of all persistently animals infected (PI) from the herd. This study examined the persistent infection for this virus in a beef cattle herd, vaccinated with killed vaccine against BVDV type 1, located in the county of Viamão, Rio Grande do Sul, southern Brazil, from november 2007 to may 2009. For the screening of PI animals, serum, blood with EDTA and fragments of ears were collected mainly from animals aged between 2-3 months. Tests used were viral isolation, reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry (IHC) and serology by enzyme linked immunosorbent assay (ELISA). From 1300 animals, 179 samples were collected and 6 were identified as persistent infected for BVDV type 2 non-cytopathic (ncp). The most important clinical signs observed on the farm were birth of weak calves, many animals with growth retardation and unilateral or bilateral cataract. The main gross lesions observed at the necropsy of 5 animals were enlargement of mesenteric lymph nodes and Peyer's patches, and in one case, pododermatitis with crusted lesions on nasal planum and periocular region. The microscopic findings were characterized mostly by mononuclear infiltrate in the lamina propria primarily in small intestine and lymphoid depletion with histiocytic infiltrate in follicular centers of lymph nodes and Peyer's patches. In 5 animals evaluated the viral antigen was more frequently demonstrated in epidermal keratinocytes, epithelium of hair follicles and dendritic cells of the dermis of the ears and skin, histiocytes and lymphocytes in lymph nodes, thyroid follicular cells, in the cytoplasm of neurons and to a lesser extent, in glial cells in the cerebral cortex and hippocampus. The analysis of pools of serum from animals suspected by RT-PCR together with immunohistochemical analysis of ears biopsy showed good results and can be useful as screening method for persistent infections in cattle, including animals under 6 months age, because they not suffer interference from maternal antibodies. The removal and elimination of PI animals had positive effects on the property, however new collection should be carried out in 2010.

O vírus da diarreia viral bovina (BVDV) é responsável por diferentes síndromes que afetam principalmente bovinos em todo o mundo, causando grandes perdas econômicas. A principal medida de controle desta infecção é a detecção e retirada dos animais persistentemente infectados (PI) do rebanho. O presente trabalho analisou a infecção persistente por este vírus em um rebanho bovino de gado de corte, vacinado com vacina inativada contra BVDV tipo 1 e localizado no Município de Viamão, Rio Grande do Sul, de novembro de 2007 a maio de 2009. Para a triagem de animais PI, amostras de soro, sangue com EDTA e fragmentos de orelhas foram coletadas principalmente de animais com idade entre 2-3 meses. Os testes utilizados compreenderam o isolamento viral, a transcrição reversa seguida da reação em cadeia da polimerase (RT-PCR), a imuno-histoquímica (IHQ) e a sorologia pelo ensaio imunoenzimático (ELISA). De 1300 animais da propriedade, coletou-se 179 amostras e em 6 se identificou a infecção persistente pelo BVDV tipo 2 não citopático (ncp). Os principais sinais clínicos verificados na propriedade englobavam nascimento de bezerros fracos, grande número de animais com retardo no crescimento e catarata congênita uni e bilateral. As principais lesões observadas em 5 animais necropsiados consistiam de aumento dos linfonodos mesentéricos, evidenciação das placas de Peyer e em um animal verificou-se pododermatite com lesões crostosas no plano nasal e na região periocular. Os achados microscópicos caracterizavam-se principalmente por infiltrado mononuclear na lâmina própria do intestino delgado e rarefação linfoide com infiltrado histiocitário nos centrofoliculares de linfonodos e nas placas de Peyer. A demonstração do antígeno viral nos 5 animais avaliados ocorreu principalmente em: queratinócitos da epiderme , no epitélio de folículos pilosos e células dendríticas da derme de orelhas e pele; histiócitos e em linfócitos dos linfonodos; células foliculares da tireoide; no citoplasma de neurônios e em menor escala, em células da micróglia no córtex cerebral e no hipocampo. A análise de pools de soro de animais suspeitos pelo RT-PCR em conjunto com a avaliação imuno-histoquímica de biópsia de orelhas mostraram bons resultados e podem ser úteis como método de triagem de infecções persistentes em rebanhos, inclusive em animais menores de 6 meses de idade por não sofrerem interferência de anticorpos maternos. A retirada e eliminação dos animais PI surtiram efeitos positivos na propriedade, entretanto novas coletas devem ser realizadas em 2010. / Bovine viral diarrhea virus (BVDV) is responsible for different syndromes that affect mainly cattle worldwide, causing important economic losses. The main control measure for this infection is the detection and removal of all persistently animals infected (PI) from the herd. This study examined the persistent infection for this virus in a beef cattle herd, vaccinated with killed vaccine against BVDV type 1, located in the county of Viamão, Rio Grande do Sul, southern Brazil, from november 2007 to may 2009. For the screening of PI animals, serum, blood with EDTA and fragments of ears were collected mainly from animals aged between 2-3 months. Tests used were viral isolation, reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry (IHC) and serology by enzyme linked immunosorbent assay (ELISA). From 1300 animals, 179 samples were collected and 6 were identified as persistent infected for BVDV type 2 non-cytopathic (ncp). The most important clinical signs observed on the farm were birth of weak calves, many animals with growth retardation and unilateral or bilateral cataract. The main gross lesions observed at the necropsy of 5 animals were enlargement of mesenteric lymph nodes and Peyer's patches, and in one case, pododermatitis with crusted lesions on nasal planum and periocular region. The microscopic findings were characterized mostly by mononuclear infiltrate in the lamina propria primarily in small intestine and lymphoid depletion with histiocytic infiltrate in follicular centers of lymph nodes and Peyer's patches. In 5 animals evaluated the viral antigen was more frequently demonstrated in epidermal keratinocytes, epithelium of hair follicles and dendritic cells of the dermis of the ears and skin, histiocytes and lymphocytes in lymph nodes, thyroid follicular cells, in the cytoplasm of neurons and to a lesser extent, in glial cells in the cerebral cortex and hippocampus. The analysis of pools of serum from animals suspected by RT-PCR together with immunohistochemical analysis of ears biopsy showed good results and can be useful as screening method for persistent infections in cattle, including animals under 6 months age, because they not suffer interference from maternal antibodies. The removal and elimination of PI animals had positive effects on the property, however new collection should be carried out in 2010.

O vírus da diarreia viral bovina (BVDV) é responsável por diferentes síndromes que afetam principalmente bovinos em todo o mundo, causando grandes perdas econômicas. A principal medida de controle desta infecção é a detecção e retirada dos animais persistentemente infectados (PI) do rebanho. O presente trabalho analisou a infecção persistente por este vírus em um rebanho bovino de gado de corte, vacinado com vacina inativada contra BVDV tipo 1 e localizado no Município de Viamão, Rio Grande do Sul, de novembro de 2007 a maio de 2009. Para a triagem de animais PI, amostras de soro, sangue com EDTA e fragmentos de orelhas foram coletadas principalmente de animais com idade entre 2-3 meses. Os testes utilizados compreenderam o isolamento viral, a transcrição reversa seguida da reação em cadeia da polimerase (RT-PCR), a imuno-histoquímica (IHQ) e a sorologia pelo ensaio imunoenzimático (ELISA). De 1300 animais da propriedade, coletou-se 179 amostras e em 6 se identificou a infecção persistente pelo BVDV tipo 2 não citopático (ncp). Os principais sinais clínicos verificados na propriedade englobavam nascimento de bezerros fracos, grande número de animais com retardo no crescimento e catarata congênita uni e bilateral. As principais lesões observadas em 5 animais necropsiados consistiam de aumento dos linfonodos mesentéricos, evidenciação das placas de Peyer e em um animal verificou-se pododermatite com lesões crostosas no plano nasal e na região periocular. Os achados microscópicos caracterizavam-se principalmente por infiltrado mononuclear na lâmina própria do intestino delgado e rarefação linfoide com infiltrado histiocitário nos centrofoliculares de linfonodos e nas placas de Peyer. A demonstração do antígeno viral nos 5 animais avaliados ocorreu principalmente em: queratinócitos da epiderme , no epitélio de folículos pilosos e células dendríticas da derme de orelhas e pele; histiócitos e em linfócitos dos linfonodos; células foliculares da tireoide; no citoplasma de neurônios e em menor escala, em células da micróglia no córtex cerebral e no hipocampo. A análise de pools de soro de animais suspeitos pelo RT-PCR em conjunto com a avaliação imuno-histoquímica de biópsia de orelhas mostraram bons resultados e podem ser úteis como método de triagem de infecções persistentes em rebanhos, inclusive em animais menores de 6 meses de idade por não sofrerem interferência de anticorpos maternos. A retirada e eliminação dos animais PI surtiram efeitos positivos na propriedade, entretanto novas coletas devem ser realizadas em 2010. / Bovine viral diarrhea virus (BVDV) is responsible for different syndromes that affect mainly cattle worldwide, causing important economic losses. The main control measure for this infection is the detection and removal of all persistently animals infected (PI) from the herd. This study examined the persistent infection for this virus in a beef cattle herd, vaccinated with killed vaccine against BVDV type 1, located in the county of Viamão, Rio Grande do Sul, southern Brazil, from november 2007 to may 2009. For the screening of PI animals, serum, blood with EDTA and fragments of ears were collected mainly from animals aged between 2-3 months. Tests used were viral isolation, reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry (IHC) and serology by enzyme linked immunosorbent assay (ELISA). From 1300 animals, 179 samples were collected and 6 were identified as persistent infected for BVDV type 2 non-cytopathic (ncp). The most important clinical signs observed on the farm were birth of weak calves, many animals with growth retardation and unilateral or bilateral cataract. The main gross lesions observed at the necropsy of 5 animals were enlargement of mesenteric lymph nodes and Peyer's patches, and in one case, pododermatitis with crusted lesions on nasal planum and periocular region. The microscopic findings were characterized mostly by mononuclear infiltrate in the lamina propria primarily in small intestine and lymphoid depletion with histiocytic infiltrate in follicular centers of lymph nodes and Peyer's patches. In 5 animals evaluated the viral antigen was more frequently demonstrated in epidermal keratinocytes, epithelium of hair follicles and dendritic cells of the dermis of the ears and skin, histiocytes and lymphocytes in lymph nodes, thyroid follicular cells, in the cytoplasm of neurons and to a lesser extent, in glial cells in the cerebral cortex and hippocampus. The analysis of pools of serum from animals suspected by RT-PCR together with immunohistochemical analysis of ears biopsy showed good results and can be useful as screening method for persistent infections in cattle, including animals under 6 months age, because they not suffer interference from maternal antibodies. The removal and elimination of PI animals had positive effects on the property, however new collection should be carried out in 2010.