Date of Award

2010

Document Type

Master Thesis

Degree Name

Masters of Science (Research)

Department

Biological Sciences

First Advisor

Dr. Helen O'Shea

Abstract

Enteric viruses, such as canine parvovirus (CPV) and canine coronavirus (CCoV), are a major cause of gastroenteritis in dogs. More serious clinical symptoms occur in young pups, or when both of these viruses infect an animal simultaneously. Caliciviruses and rotaviruses can also cause gastroenteritis in dogs, but these viruses, while causing significant problems in other animal species and humans, are considered to be less significant pathogens of canines. However, on occasion, these viruses have been reported to produce severe clinical symptoms such as vomiting, haemorrhagic enteritis and severe dehydration.

Many viral vaccines for canines are formulated using old vaccine viral strains which, in some cases, warrant updating, as a result of the emergence of more virulent strains. The original CPV-2 strain is still employed in commercial vaccines, despite the fact that this strain was entirely replaced by its variant types, CPV-2a, 2b and 2c, shortly after its emergence. Currently, all coronavirus vaccines are based on the CCoV-Il strain. However, it has been shown that the level of cross-reactivity between CCoV-I and II is limited. There are currently no commercial vaccines available for the prevention of rotavirus and calicivirus infection, as these viruses are not regarded as a significant problem in canines.

Canine parvovirus: In this study, the occurrence of CPV in the Irish canine population was investigated. Two hundred and fifty canine faecal samples were collected from a wide variety of groups, including clinically ill dogs, guide dogs, hunting dogs, greyhounds and stray dogs. Samples were taken from both clinically ill (n=40) and healthy dogs (n=210), collected from 2008 to 2009. Seven parvovirus strains were identified in symptomatic Irish pups, aged between 2 and 15 months, by polymerase chain reaction (PCR) analysis. A fragment of the VP2 gene was analysed using PCR, restriction fragment length polymorphism (RFLP) analysis and DNA sequence analysis. Sequence analysis characterized three strains as CPV-2a, while four others were characterized as CPV-2b. None of the isolates were characterized as CPV-2c, this CPV type remains undetected in Ireland to date.

Canine coronavirus: Two hundred and fifty canine faecal samples, from the same sample pool, were tested for the presence of canine coronavirus. Three samples (1.2%) tested positive for coronavirus (CoV) by RT-PCR detection. Following sequence analysis, two of the strains (AVC3/09/lre and AVC2/09/lre) were characterized as CCoV-ll, and one strain (PH4/09/lre) was characterized as CCoV-l. All strains were isolated from clinically ill dogs, from the age of three months to eight years. Canine parvovirus (CPV) was also identified in the sample from which the CCoV-1 strain was isolated. This is the first report of both CCoV- I and II in Ireland.

Rotavirus and calicivirus: All faecal samples were screened for the presence of rotavirus, via RT-PCR amplification of the VP7 gene, and for calicivirus, via RT-PCR amplification of a region the RNA polymerase complex. However, none of the samples tested positive for either of these viruses.

This study was undertaken to investigate the prevalence of enteric viruses in the canine population in southern Ireland. This is the first report of CPV and CCoV in Ireland. Continued surveillance is required to facilitate detection of changes in circulating strains, also to determine vaccine efficacy and improve available prophylactic measures.

Access Level

info:eu-repo/semantics/openAccess

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