Pathogenesis of Canine Parvovirus Enteritis: The Importance of Viremia

Abstract

Abstract. The clinical signs, hematologic changes, serum and fecal virus titers, specific antibody production and the occurrence of histologic lesions were studied in 22 nine-week-old seronegative beagle dogs inoculated by the oral and intravenous route with canine parvovirus. Approximately 30% of the dogs had clinical signs of pyrexia, depression, vomiting, and diarrhea irrespective of the route of inoculation. Events in the dogs inoculated intravenously preceded those in dogs inoculated orally by approximately two days. Only one dog died. Lymphopenia was the most consistent hematologic change. Viremia always preceded the initiation of fecal virus shedding. Viral titers in the serum and feces were significantly greater in symptomatic dogs compared to asymptomatic dogs. Termination of the plasma viremia coincided with the onset of the humoral immune response, but viremia persisted one day longer in symptomatic dogs. The severity of lymphoid tissue and intestinal infection, assessed by tissue immunofluorescence and histology, was also greater in symptomatic dogs. The severity of intestinal disease was highly correlated with the magnitude and duration of viremia.The clinical signs, clinicopathologic and pathologic changes in fatal cases of naturally occurring canine parvovirus enteritis have been well-do~umented.~~~.Fatal cases are characterized by leukopenia and extensive necrosis of intestinal gland epithelium and lymphoid tissues. Although subclinical infection with canine parvovirus is less wellcharacterized, serologic evidence and limited epidemiologic s t~d i e s '~. ' ' ,~~ suggest that canine parvovirus infection more frequently results in subclinical than fatal disease. Similarly, experimental canine parvovirus enteritis infrequently results in severe clinical disease. Severe illness has been experimentally produced by intravenod5 and by oronasal and intraga~tric'.~~ inoculation of puppies. In the later clinical signs occurred only in dogs vaccinated with a mixed vaccine five days prior to canine parvovirus inoculation. Factors associated with the variation in the severity of the enteric disease in both the experimental and the natural setting have not been identified.This study was undertaken to determine the pathogenesis of experimental canine parvovirus enteritis and to identify factors associated with its variable severity. Materials and MethodsEighteen conventional and ten specific pathogen free seronegative nine-week-old beagle dogs were housed in individual 10. 13. 14. 16. 18.21.23.25.26.28.30.32.39.4l cages within isolation units, fed commercial dry dog food, and provided water ad libitum.Following a 12-hour fast, seven conventional and four specific pathogen free dogs were inoculated orally, and an equal number intravenously with I O5 tissue culture infective doses (TCID5,J of canine parvovirus. Four conventional and two specific pathogen free dogs were uninoculated controls. Rectal temperatures and clinical signs were recorded daily.Blood and fecal samples were collected daily for three days ...

Purified Feline and Canine Transferrin Receptors Reveal Complex Interactions with the Capsids of Canine and Feline Parvoviruses That Correspond to Their Host Ranges

“…However, there is obviously not a simple relationship between feline TfR inactivation and cat infection, as the soluble feline TfR also inhibited FPV binding and infection of cells. Explanations would be that FPV circulates in a cell-associated form in cats, while CPV-2 circulates as a free viremia (as it does in dogs) and therefore is readily inactivated (11,43,62). However, the comparative pathogenesis of the different viruses is not sufficiently well understood to allow us to determine the mechanisms involved.…”

Clinical Effects of the Recombinant Feline Interferon-.OMEGA. on Experimental Parvovirus Infection in Beagle Dogs.

“…In the present experiments, rFeIFN-ω was administered on day 4 after virus inoculation when CPV-2 replication has already spread resulting in cytological effects on germinal epithelium of the intestinal crypts and in the appearance of enteritis [15,17,18]. The ameliorating effect of treatment of CPV-2-infected dogs with rFeIFN-ω, therefore, appears to be due to not only its antiviral activity, but to other functions of IFNs, such as enhancement of immune systems in vivo.…”

“…Meunier et al [18] reported that 10 5 TCID 50 of CPV caused clinical signs in about 30% of infected beagle dogs. In the present experiments, inoculation of 10 7 TCID 50 of CPV-2 (cc 238 strain) induce clinical symptoms in all exposed SPF animals, although the severity of symptoms were milder than natural disease.…”

Fatal Coronavirus Infection in Puppies following Canine Parvovirus 2b Infection

“…Alterations of the intestinal villi were typical of CCV infection S 1,8,9 however, basophilic intranuclear inclusion bodies in crypt epithelial cells, as well as necrosis and depletion of lymphoid tissue, are characteristic findings in CPV but not CCV infections. 4,11 Those findings notwithstanding, cells still infected by CPV-2b would not be expected to persist 3 weeks after the initial infection, 11 and CPV-2b was not demonstrated in the pups' feces by HA or the IFAT. Furthermore, experimental studies on CPV-2b pathogenesis in pups failed to reveal virus, or viral DNA in tissues Ͼ6 days after oronasal infection by virus isolation or in situ DNA hybridization methods (D. Peters, unpublished data).…”