A retrospective histopathological survey of capillariasis in raccoons (Procyon lotor) from Oregon

A 2-yr retrospective survey (1995-1998) of 63 adult raccoons (Procyon lotor) from Oregon, northwestern United States, was conducted by histopathological examination of various tissues. An overall prevalence of capillariasis was recorded in 52% of the raccoons. Highest prevalence of nematodes (29/30, 97.7%) was present in the anal sacs, where variable numbers of nematodes, their ova, and extensive diffuse inflammatory cellular infiltrate were evident. Lesser numbers of nematodes were also seen in the mucosa of the anterior alimentary tract (mouth 2/63, tongue 10/62, esophagus 2/63) and in the urinary bladder (7/63). However, at these sites, there was a paucity of inflammatory infiltrate. The findings of this study indicate that capillariasis of the anal sacs is commonly seen in free-ranging raccoons in Oregon, and the infection is essentially subclinical because only 1 case of anal sac impaction has been reported. Measurements of the nematode and their ova from the anal sacs indicate that it is most likely a new capillariid species, which to date has not been fully described in raccoons. It is speculated that the high prevalence of anal sac infection by a Capillaria sp. in Oregon raccoons may also be true for raccoons in other parts of North America and in parts of Europe and Asia where this species has been introduced.