Parvovirus
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Parvo is a highly contagious disease causes by the small, nonenveloped, single-stranded DNA virus canine parvovirus (CPV). It is designated as CPV type-2 to distinguish it from an unrelated parvovirus (Truyen et al, 1996). It is also thought to have originated from feline panleukemia virus (FPV) or a very closely related carnivore parvovirus of wild canids like foxes and mink (Kaur et al, 2015; Bird and Tappin, 2013). It was first recognized worldwide in 1978 and has since become the most common cause of viral enteritis in dogs (Truyen et al, 1996; Sutton et al, 2013; Bird and Tappin, 2013).Since its emergence, it has evolved into three antigenic strains known as CPV2a, CPV2b, and CPV2c.
Canine parvovirus can affect any dog of any age, breed, or sex, but puppies between six weeks to six months are susceptable to infection (Shah et al, 2013). Dogs can get infected when they come into contact with the feces of other canines that were infected with the virus and rare transplacental infection has also been reported (Bird and Tappin, 2013). After infection, viral replication occurs in the rapidly dividing cells of the intestinal crypt epithelium, bone marrow, and myocardium (Bird and Tappin, 2013). Viral destruction of intestinal crypts results in villous collapse, intestinal bleeding and secondary infections, especially with enteric gram-negative bacteria (Bird and Tappin, 2013). Damage to bone marrow can lead to neutropenia; which contributes to the risk of secondary infections (Bird and Tappin, 2013). Puppies infected as a result of transplacental infection, or are infected before they are eight weeks old, may develop myocarditis due to damage as the result of viral replication in the myocardium (Bird and Tappin, 2013).
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The commonly observed clinical signs of parvovirus infection are vomiting, diarrhea, anorexia, and depression (Shah et al, 2013; Bird and Tappin, 2013). Because leukopenia is commonly associated with parvoviral infection, a look at a dog's white blood cell count can suggest parvovirrus infection. But since Salmonellosis, or any other overwhelming infection, can cause similar haematological findings; other tests should be done to confirm parvovirus infection. Parvoviral ELISA antigen snap tests are often used to detect CPV in faeces of infected dogs. One study showed the test's ability to detect the different strains of parvovirus present (Bird and Tappin, 2013). ELISA results may be negative if the assay is performed early in the disease course as viral shedding is low at this stage and tests should be repeated in dogs that continue to show signs and maintain a clinical suspicion of CPV enteritis.
For information of the prevention and treatment of parvovirus click here.
References:
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Truyen UWE, Evermann JF, Vieler E, Parrish CR. Evolution of Canine Parvovirus Involved Loss and Gain of Feline Host Range. Virology, 1996; 215:186-189.
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Kaur G, Chandra M, Dwivedi PN, Sharma NS. Isolation of Canine parvovirus with a view to identify the prevalent serotype on the basis of partial sequence analysis. Veterinary World. 2015; 8(1): 52-56.
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Bird L, Tappin S. Canine parvovirus: where are we in the 21st Century?. Companion Animal. 2013; 18(4): 142-146.
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Sutton D, Vinberg C, Gustafsson A, Pearce J, Greenwood N. Canine parvovirus type 2c identified from an outbreak of severe gastroenteritis in a litter in Sweden. Acta Veterinaria Scandinavica. 2013; 55(1): 64-69.
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Shah SA, Sood NK, Wani N, Gupta K, Singh A. Haemato-biochemical changes in canine parvoviral infection. Indian J. Vet. Pathol. 2013; 37(2): 131-133.