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Medycyna Weterynaryjna
|
2010
|
tom 66
|
nr 07
s.439-443,rys.,fot.,tab.,bibliogr.
Hepatitis A virus (HAV) is the most common cause of hepatitis in humans all over the world. Non-enveloped HAV is classified to the Picornaviridae family. The virus is highly resistant to physico-chemical factors. The genome contains the single-strand RNA encoding a long polyprotein. This polyprotein is used to form four structural and seven non-structural proteins in the post translating process. All polyprotein cleavage sites have not been identified, yet infection with HAV frequently occurs through the consumption of contaminated food or water. The disease is often asymptomatic in young children. In older children and adults different clinical symptoms may be observed, from mild (without jaundice) to severe liver failure. In many regions of the world the disease occurs endemically and in developed countries outbreaks and epidemics are noted. Inactivated vaccines are used in specific protection.
Hepatitis E virus (HEV) is a hepatovirus causing infections in humans and in many animal species. According to the current knowledge, HEV strains have been classified in the genus Orthohepevirus, family Hepeviridae, which encompasses strains belonging to one of seven virus genotypes. Genotypes 1 and 2 have only been found in humans, while genotypes 3 and 4 have been detected in humans, pigs, deer, rabbits and mongoose. The other HEV genotypes infect wild animals. However, the full spectrum of animal species being the natural reservoir of HEV has not been fully recognized. The clinical course of hepatitis in animals is asymptomatic, and infections do not cause significant losses in animal farming. Unlike in animals, infections in humans, and especially in pregnant women, can cause serious health problems. The identification of new virus strains in the animal reservoir and the possibility of transmission of some animal HEV strains to humans make the issue of public health protection and food safety even more important. This article provides an overview of data on the prevalence of HEV infections in animals and their impact on human and animal health.
The epidemic human gastroenteritis can be caused by different factors, including viruses. The World Health Organization reports the increase of foodborne and waterborne disease outbreaks as a result of the contamination of food and water by viruses, especially noroviruses. Norovirus (NoV) are classified in the Caliciviridae family, Norovirus genus. The genome contains a linear positive-sense, single-stranded RNA. Noroviruses are classified into 5 genogroups (GI-GV), and 31 genotypes: 8 GI, 19 GII, 2 GIII, 1 GIV and 1GV. The human noroviruses belong to GI, GII and GIV. Genetic analysis of norovirus strains has revealed nucleotide and amino acid mutations as well as the existence of recombination between strains. The intragenotype and intragenogroup recombination was recognized most frequently, but intergenogroup recombination was also identified in the last years. Recombination between human and animal strains has not yet been identified. The variants of NoVs GII.4 emerged to be the predominant strains in human populations as a result of norovirus evolution.
Myxomatosis is a highly infectious viral disease of rabbits. Myxoma virus (MYXV) is not pathogenic to other animal species except for rabbits and hares. In Poland, outbreaks of myxomatosis mainly occur on small-scale size rabbit farms in which specific immunoprophylaxis is not carried out. A typical nodular form of the disease is characterized by swelling and large myxomas over the whole body as well as by lung infection which is associated with atypical myxomatosis. However, differences in the virulence of MYXV strains are observed. They arise from a better adaptation of the virus to the rabbit host and they may also be related to the modulation of cellular response by infected animals. In fact, the changes observed in the MYXV genome do not result in the emergence of other novel virus strains than those currently circulating in the rabbit population. In addition, all previously detected strains are characterized by high phylogenetic relatedness.
Rotavirus gastroenteritis has been recognized as the most important cause of acute diarrhea in children between 6 months and two-years-of-age in industrialized countries. Rotaviruses are classified as a genus within Reoviridae family and have a characteristic wheel-like shape. The concentric icosahedral viral capsid, 60-70 nm in diameter, is made up of two protein layers and encloses 11 segments of genomic double-stranded RNA. Each segment of RNA represents one gene that encodes a virus-specific protein. Rotaviruses also contain the spike protein VP4 and a major capsid component, VP7, both of which are responsible for their entry into a cell. Natural infection reduces the incidence and severity of subsequent episodes, rotavirus diarrhea might be controlled through vaccination. Serotype-specific immunity may play a role in protection from the disease.
Noroviruses are the most frequent etiological factor of non-bacterial human gastroenteritis. Contaminated bivalve molluscs, especially oysters and mussels, are the most frequent source of infections. Shellfish are filter feeders. As they filter and clean the water, they simultaneously concentrate and accumulate viruses. Human (HuNoVs: genogrup I - GI and genogrup II - GII), porcine (PoNoV - GII.11, GII.18, GII.19) and bovine noroviruses (BoNoV - GIII) have been detected in bivalve molluscs. The stability of NoVs in the environment is high. Adequate heat treatment inactivates these viruses, but inactivation crucially depends on the time and temperature of such a treatment. Gastroenteritis outbreaks caused by viruses follow a pattern of winter seasonality between January and April. An increased number of foodborne viral outbreaks following the consumption of contaminated bivalve molluscs has been noted in recent years.
In this paper we describe recently occurring outbreaks of European brown hare syndrome (EBHS) in a captive hare population. The aim of our study was to evaluate the phylogenetic position of detected Polish strains compared to other European strains of EBHSV. Investigations were undertaken in hares from different provinces of Poland. Liver or spleen samples were tested for viral RNA using the RT-nested PCR method and the products were subsequently sequenced. The genetic analysis was based on the fragment of gene encoding viral capsid protein; it revealed a high homology and close relationship between Polish and European EBHSV strains isolated between 2001 and 2011.
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