Applications of nucleic acid probes in veterinary infectious diseases

Exploring viral diversity and metagenomics in livestock: insights into disease emergence and spillover risks in cattle

Cattle have a significant impact on human societies in terms of both economics and health. Viral infections pose a relevant problem as they directly or indirectly disrupt the balance within cattle populations. This has negative consequences at the economic level for producers and territories, and also jeopardizes human health through the transmission of zoonotic diseases that can escalate into outbreaks or pandemics. To establish prevention strategies and control measures at various levels (animal, farm, region, or global), it is crucial to identify the viral agents present in animals. Various techniques, including virus isolation, serological tests, and molecular techniques like PCR, are typically employed for this purpose. However, these techniques have two major drawbacks: they are ineffective for non-culturable viruses, and they only detect a small fraction of the viruses present. In contrast, metagenomics offers a promising approach by providing a comprehensive and unbiased analysis for detecting all viruses in a given sample. It has the potential to identify rare or novel infectious agents promptly and establish a baseline of healthy animals. Nevertheless, the routine application of viral metagenomics for epidemiological surveillance and diagnostics faces challenges related to socioeconomic variables, such as resource availability and space dedicated to metagenomics, as well as the lack of standardized protocols and resulting heterogeneity in presenting results. This review aims to provide an overview of the current knowledge and prospects for using viral metagenomics to detect and identify viruses in cattle raised for livestock, while discussing the epidemiological and clinical implications.

Leptospirosis genital incidental en machos Bubalus bubalis del estado Portuguesa, Venezuela

La leptospirosis constituye una importante causa de infertilidad en bóvidos. En Bubalus bubalis, Leptospira spp. infecta el tejido renal, así como los órganos sexuales, por lo que puede excretarse, tanto en orina como en semen. Solo un número limitado de estudios en todo el mundo han investigado la seroprevalencia de la enfermedad en machos bovinos y los riesgos reproductivos relacionados con la eliminación del patógeno en el semen. Se reportan aquí los resultados de la evaluación serológica, microbiológica, seminal e histopatológica de machos bufalinos adultos del municipio Esteller, estado Portuguesa, Venezuela, infectados naturalmente con Leptospira spp. Se evaluaron 17 búfalos mestizos Murrah de 40 meses de edad, previo al beneficio, con 500 kilos de peso promedio, no vacunados, a los cuales se les tomaron muestra de suero sanguíneo, orina, semen y se midió circunferencia escrotal junto a otros parámetros reproductivos. Exclusivamente 15 animales mostraron títulos entre 50 y 200 en la MAT, exclusivamente para L. hebdomadis. Los 2 animales negativos a MAT resultaron positivos en cultivo bacteriológico de orina o semen a Leptospira spp. De 6 animales beneficiados, MAT y bacteriológicamente positivos a leptospira en semen y orina, se extrajeron riñones, testículos y epidídimos para examen histopatológico. De epidídimos y riñónes se aislaron Leptospira spp., no así de testículos. Sin embargo, el diagnóstico histopatológico en testículo y epidídimo indicó degeneración de células seminíferas compatible con infección bacteriana. El riñón presentó nefritis intersticial crónica. Hubo disminución en el promedio de la circunferencia escrotal, baja intención de monta, baja concentración espermática, ausencia de ondas, pocos espermatozoides móviles, baja motilidad espermática y más de 30 % de mortalidad espermática de las muestras de semen evaluadas, indicando baja calidad del eyaculado. Las anomalías seminales mayores y menores superaron las escalas recomendadas para la especie. Se reportan aquí resultados exclusivos de búfalos machos infectados individualmente con L. hebdomadis, excretada por orina y semen, responsable de afectar el tracto reproductivo de manera incidental, ocasionando daños espermáticos, del epidídimo y daño renal, en una explotación mixta arrocera, con presencia de roedores, potenciales transmisores de la leptospirosis.

USO DE ESTREPTOMICINA NA ELIMINAÇÃO DA LEPTOSPIRÚRIA EM TOUROS (BOS TAURUS INDICUS) NATURALMENTE INFECTADOS PELO SOROVAR HARDJO

RESUMO O objetivo desse trabalho foi verificar a ação de marcas diferentes de estreptomicinas polivalentes para o tratamento da leptospirose bovina em dose única (25 mg de estreptomicina por kg de peso corpóreo). O trabalho foi realizado com 14 touros adultos sorologicamente reagentes para Leptospira interrogans sorovar Hardjo, com título mínimo de 800 e com cultivo positivo. Os animais foram separados em 2 grupos de acordo com a marca da estreptomicina utilizada no tratamento, grupo 1: estreptomicina A e grupo 2: estreptomicina B. Os bovinos controles não receberam nenhum tratamento. Foram obtidas amostras de sangue e urina dos animais tratados e controles nos dias -1, 0, 1, 2, 3, 5, 10, 15 e 25; considerando-se o dia do tratamento como dia 0. Na urina dos bovinos tratados e controle foi realizada a reação em cadeia da polimerase (PCR) e isolamento com inoculação em hamsters. Observou-se que a estreptomicina da marca A, em dose única de 25 mg/kg de peso corpóreo, conseguiu eliminar a leptospirúria no grupo de touros após 24h do tratamento. Já no grupo de touros tratados com a estreptomicina da marca B, foi constatado a leptospirúria entre 48h e 72h, após o tratamento. Em ambos os grupos tratados, a resposta sorológica apresentou uma variação da queda dos níveis dos títulos de anticorpos aglutinantes, sendo que embora a estreptomicina A tenha aparentemente apresentado um melhor desempenho quando comparada com as médias geométricas dos títulos do grupo tratado com a estreptomicina B as médias não diferiram entre si pelo Teste de Tukey (P > 0,05). Nos bovinos tratados a leptospirúria foi intermitente e a média geométrica dos títulos foi menor que a média geométrica dos títulos dos bovinos controles. A diferença do efeito da ação das diferentes marcas de estreptomicina está possivelmente na qualidade da matéria prima produzida pelos laboratórios.

Comparison of dot blot hybridization, polymerase chain reaction, and virus isolation for detection of bovine herpesvirus-1 (BHV-1) in artificially infected bovine semen

Bovine semen samples spiked with bovine herpesvirus 1 (BHV-1) were used to compare dot blot hybridization, polymerase chain reaction (PCR), and virus isolation for detection of BHV-1 in bovine semen. The PCR amplification used primers targeting the BHV-1 thymidine kinase gene and a nucleic acid releasing cocktail (GeneReleaser); the PCR product was used as the DNA probe in dot blot hybridization; virus isolation was done in primary bovine fetal testis (BFT) cell cultures. Semen diluted 1:20 in tissue culture medium had the least cytotoxicity and inhibition of viral cytopathic effects in BFT cells, allowing detection of 1 TCID50/100 microL of BHV-1 suspension by virus isolation. The presence of foreign DNA such as bovine sperm DNA or salmon sperm DNA increased the sensitivity of dot blot hybridization in detecting BHV-1, allowing detection of 20,000 TCID50/100 microL of neat semen. The inhibition of PCR amplification of BHV-1 DNA in bovine semen was eliminated by diluting the samples 1:20 in tissue culture medium. The best PCR amplification was obtained when semen was diluted 1:20 and when a reaction buffer of pH 9.0, with 1.0 mM MgCl2 was used. Under these conditions, the PCR followed by ethidium bromide staining of agarose gels could detect 1 TCID20/100 microL of sample, whereas PCR followed by Southern blot hybridization could detect 0.01 TCID50/100 microL of sample.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of the mode of sampling on BHV-1 detection in infected cattle by dot-blot hybridization

The BHV-1 genome in nasal swabs and washings was detected by dot-blot hybridization using the 32P-pUR-1 probe (1.8 kb EcoRI-HindIII random fragment of BHV-1 DNA ligated into the pUC-9 plasmid) as early as on day 1 after the experimental infection of cattle. In dependence on the sampling method, differences were observed in the maximum of hybridization signals. During nasal swab analyses maximum amounts of BHV-1 differed in the individual samples (day 1-3). Hybridization signals obtained at the analysis of BHV-1 DNA nasal washings did not vary but showed a continuous maximum on day 2 after infection. Nasal washings proved to be more advantageous for detection of the BHV-1 genome by the hybridization technique.

Application of the polymerase chain reaction (PCR) in veterinary diagnostic virology

The polymerase chain reaction has become an important diagnostic tool for the veterinary virologist. Conventional methods for detecting viral diseases can be laborious or ineffective. In many cases PCR can provide a rapid and accurate test. In this article we explain the basic principles of PCR and supply a reference list of its uses in diagnostic veterinary virology.