Molecular epidemiology of animal virus diseases

Viral infection detection using metagenomics technology in six poultry farms of eastern China

With rapidly increasing animal pathogen surveillance requirements, new technologies are needed for a comprehensive understanding of the roles of pathogens in the occurrence and development of animal diseases. We applied metagenomic technology to avian virus surveillance to study the main viruses infecting six poultry farms in two provinces in eastern China. Cloacal/throat double swabs were collected from 60 birds at each farm according to a random sampling method. The results showed that the method could simultaneously detect major viruses infecting farms, including avian influenza virus, infectious bronchitis virus, Newcastle disease virus, rotavirus G, duck hepatitis B virus, and avian leukemia virus subgroup J in several farms. The test results were consistent with the results from traditional polymerase chain reaction (PCR) or reverse transcription-PCR analyses. Five H9N2 and one H3N8 avian influenza viruses were detected at the farms and were identified as low pathogenic avian influenza viruses according to HA cleavage sites analysis. One detected Newcastle disease virus was classified as Class II genotype I and avirulent type according to F0 cleavage sites analysis. Three avian infectious bronchitis viruses were identified as 4/91, CK/CH/LSC/99I and TC07-2 genotypes by phylogenetic analysis of S1 genes. The viral infection surveillance method using metagenomics technology enables the monitoring of multiple viral infections, which allows the detection of main infectious viruses.

CARACTERIZAÇÃO GENÉTICA E DISTRIBUIÇÃO GEOGRÁFICA DO VÍRUS RÁBICO ISOLADO DE BOVINOS NO ESTADO DE MATO GROSSO, BRASIL

RESUMO Foram caracterizados, geneticamente e geograficamente, o sequenciamento parcial da nucleoproteína (gene N) de 53 isolados do vírus da raiva (VR) originários do Estado de Mato Grosso, Brasil. Os isolados de bovinos, que se encontravam no grupo do VR relacionado a morcegos hematófagos, foram posteriormente subdivididos em sete subgrupos genéticos. Estes subgrupos foram distribuídos em regiões de terras planas, com alguns subgrupos separados por formações de pequenas montanhas e hidrografia. Estes resultados indicam que a raiva em bovinos é derivada de diversas variantes regionalmente definidas, o que sugere que sua distribuição geográfica está relacionada as populações de morcegos hematófagos.

Use of molecular epidemiology in veterinary practice

Molecular epidemiology is a relatively new branch of epidemiology that uses molecular biology methods to study health and disease in populations. This article gives an introduction to molecular epidemiologic terminology and methodology and its usefulness in large animal medicine and veterinary public health. Applications in source tracing and vaccine studies and insights into transmission dynamics, host specificity, and niche adaptation of infectious organisms are presented. Examples are drawn from a variety of diseases, organisms, and host species and range from the global level to the individual-animal level.

A survey for BVDV antibodies in cattle farms in Slovakia and genetic typing of BVDV isolates from imported animals

A serological survey for bovine viral diarrhoea virus (BVDV) antibodies on a collection of 1295 serum samples obtained from 6-12 months old cattle originating from 45 farms in Slovakia was carried out. On 13 farms more than 90% of the examined animals were seropositive, on 14 farms 71-90% seroprevalence was observed, on 13 farms only 50-70% animals were found to be positive for BVDV antibodies, while the remaining 5 farms showed fewer than 50% seropositive animals. The average incidence of BVDV antibodies (around 70%) was similar as determined 30 years ago. Of 84 serum samples from seronegative animals originating from 14 farms in which 70-98% seropositivity was observed, six were positive in Ag-BVDV ELISA indicating persistently infected (PI) cattle. On a farm to which animals were imported from abroad, a BVD outbreak was observed. Of 110 animals tested, four were positive in Ag-ELISA indicating the presence of PI cattle on this farm. Genetic typing of two isolates from imported animals performed by RT-PCR (324/326 primers from 5'-UTR), sequencing of PCR products and computer-assisted phylogenetic analysis revealed that they belong to BVDV-1 h group.

Recent developments in the epidemiology of virus diseases

There is continual variation in viral epidemics regarding clinical symptoms, duration and disappearance, and the emergence of new diseases. This can be observed in both human and animal diseases. This evolution of virus diseases is mainly related to three factors: aetiological agent, host and environment. As far as genetic alterations of the virus are concerned, two major mechanisms are involved: mutations such as recombination and reassortment; and selection for resistance or susceptibility. This review focuses on the epidemiology of newly emerged virus diseases in man and animals, such as acquired immunodeficiency syndrome, haemorraghic fevers, bovine spongiform encephalopathy, canine haemorraghic disease and respiratory syndrome in horses.

Recent developments in the epidemiology of virus diseases and BSE

There is a continuous change in viral epidemics with respect to clinical symptoms, their duration or disappearance and the emergence of new diseases. This can be observed both in human and animal diseases. This evolution of virus diseases is mainly related to three factors: etiological agent, host and environment. As far as genetic alterations of the virus are concerned, two major mechanisms are involved: 1) mutations such as recombination and reassortment; 2) selection for resistance or susceptibility. The epidemiology of newly emerged virus diseases in man and animals, such as AIDS and hemorrhagic fevers, and bovine spongiform encephalopathy (BSE), canine hemorrhagic gastroenteritis or respiratory syndrome in horses will be discussed.

Molecular epidemiology of rabies virus isolates from Israel and other middle- and Near-Eastern countries

A total of 226 isolates of rabies virus from different areas of Israel, including three human isolates and one sample from South Lebanon were identified between 1993 and 1998 by direct immunofluorescence using monoclonal antibodies to the viral nucleoprotein (N). An epidemiological survey based on nucleotide sequence analysis of 328 bp from the C terminus of the N coding region and the noncoding region between the nucleoprotein and the phosphoprotein (NS gene) was performed. Phylogenetic analysis of the isolates from Israel showed that they were related geographically, but not according to host species. Five variants, related groups distributed among four geographical regions, were identified. In each region, rabies virus was isolated from more than one animal species. A comparison of the sequence analysis of rabies virus samples from the rest of world revealed a 2-nucleotide change that distinguished the Middle East variants from the rest.