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February 1, 2023

Case History: A juvenile male 7.05 kg Common Raccoon (Procyon lotor) was found dead on a prairie in Wisconsin, USA, in October 2006. Several other juveniles and one adult raccoon had recently been found dead in the same area. Tests for canine distemper and rabies were negative.

Gross Findings: On external examination, the raccoon was unremarkable except for a small amount of liquid fecal staining around the anus. On internal examination, there was abundant subcutaneous, visceral and epicardial fat. The small intestine was flaccid, fluid-filled and thin-walled. The duodenum and the proximal jejunum contained a large quantity of green liquid tinged with blood. There was marked segmental reddening of the serosa of the mid to distal jejunum and proximal ileum (Fig 1A), and strands of fibrin were present on the surface. The mucosa of the distal jejunum and proximal ileum was variably reddened and bloody (Fig 1B) or was covered by a diphtheritic pseudomembrane. Areas covered by the pseudomembrane contained yellow flocculent liquid. Moderate numbers of large roundworms (Baylisascaris procyonis) were present throughout the small intestine.  

Histopathological Findings: A thick mat of bacteria, neutrophils, red blood cells, fibrin, and necrotic cellular debris covers the mucosal surface of the jejunum. There is severe diffuse villar loss and the mucosal epithelium is essentially missing except for the crypts (Fig 1C). The crypts are dilated, lined by flattened epithelium, and contain scant intraluminal necrotic cellular debris and small numbers of neutrophils (Fig 1D).

Photographs and photomicrographs from a Common Raccoon showing lesions from parvovirus
Figure 1. Photographs and photomicrographs from a Common Raccoon (Procyon lotor) found dead on a prairie in Wisconsin, USA. (A) There is abrupt segmental reddening of the serosa of the distal jejunum and proximal ileum (arrows). (B) The mucosa of an affected area of the distal jejunum is reddened and bloody (C). The mucosal surface of the distal jejunum is covered with a thick mat of bacteria and necrotic cellular debris (arrow). There is severe diffuse villar blunting and loss, such that only the dilated crypts remain (asterisk). H&E stain. (D) Dilated crypts are lined by flattened epithelium (arrow) and contain necrotic cellular debris (asterisk). H&E stain.

Morphologic Diagnosis: Acute, severe, locally extensive necrohemorrhagic enteritis with crypt necrosis

Disease: Parvoviral enteritis

Etiology: Raccoon parvovirus (RPV). Multiple strains of RPV have been isolated from wild raccoons. The majority are most closely related to canine parvoviruses 2 and 3 (CPV-2 and CPV-3, respectively), however some group more closely with feline panleukopenia virus.

Distribution: RPV occurs wherever the Common Raccoon is present; this species is native to North America and is introduced in Europe and Asia.

Seasonality: Most common in late spring/early summer due to the presence of susceptible juveniles but can occur year-round.

Host range: By definition, RPV occurs only in the Common Raccoon.

Transmission: RPV is highly infectious and is also environmentally persistent. Direct contact with an infected raccoon or its feces can transmit the virus but is not required for efficient transmission, as the virus can stay infectious in the environment for weeks or even months.

Clinical signs: Clinical signs include bloody diarrhea, vomiting, lethargy, and inappetence. Neurologic signs have also been reported and when present may mimic canine distemper or rabies.

Pathology: Segmental necrohemorrhagic enteritis with crypt necrosis is the hallmark of parvoviral infection in the raccoon. Bacterial septicemia is also commonly present, as bacteria may leak from the compromised intestine. Non-suppurative encephalitis and demyelination have been reported in a juvenile raccoon infected with a canine parvovirus variant (CPV-2a-like virus).

Diagnosis: A presumptive diagnosis may be made based on gross and histopathologic findings. Definitive diagnosis requires a positive PCR test, immunohistochemistry, or virus isolation. A rapid ELISA test for canine parvovirus may be used on raccoon feces in a clinical setting.

Public health concerns:  None known.

Wildlife population impacts: The impact of this disease on the raccoon population has not been described. Because RPVs are diverse and often are very closely related to those in other carnivores, it has been suggested that raccoons may be involved in the transmission of these viruses between species.

Management: None currently recommended for wildlife. Quarantine of incoming raccoons, isolation of sick raccoons, and disinfection of contaminated areas are recommended in rehabilitation facilities.


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