Results and Discussion
Clinical symptoms and pathological
lesion s
General lethargy, reduced food intake, and loose stools were among the
symptoms observed in the two pangolins examined in the present study.
Furthermore, whereas electrolyte disturbance was observed, there was no
evidence of leucopenia. The pangolins died naturally at 4-6 days
post-rescue, with post-mortem examinations revealing apparent congestion
and hemorrhage in the intestinal tract, thickened intestinal walls, and
necrosis of the mucosal tissue (Fig. 1A). Histopathological
observations, performed to determine lesions associated with CPV-induced
diarrhea, revealed intensive injury to the mucosal layer of the small
intestine to be a prominent feature, particularly the necrosis and
shedding of intestinal mucosal intraepithelial cells and glands, which
were observed in all parts of the small intestine (Fig. 1 B and C).
Moreover, the submucosal layers were found to be characterized by
inflammatory infiltrates, comprising
primarily neutrophils and scattered
lymphocytes. In addition, we observed a reduction in the number of
lymphocytes in the spleen. The detection of bacteria in rectal tissues
provided evidence to indicate the probable occurrence of secondary
bacterial infection. In contrast, there was no indication of
histopathological changes in the heart, liver, lungs, or kidneys.
Immunohistochemical analyses were performed to determine the
localization of CPV antigen in the intestinal system of the CPV-infected
pangolins, representative high-magnification images of which are
presented in Fig 1. D and E. CPV antigens were detected in the
duodenum, jejunum, and ileum,
although not in the mesenteric
lymph nodes, with strong HRP
signals being observed in the crypt region and vicinity of inflamed
cells. These pathological changes in CPV-infected
pangolins are similar to those previously described in CPV-infected
dogs, in which hemorrhagic
enteritis and crypt neurosis are prominent features
(Pollock, 1982).
Moreover, consistent with our observations of histopathological lesions,
the crypt was established to be the major CPV antigen-positive region
(Fig. 1). These pathological changes are consistent with those
previously reported by Wang et al. (2020), thereby indicating that that
CPV-2 targets and replicates within in the intestinal tract cells of
animals in the order Pholidota.