Systemic Besnoitiosis in a Juvenile Roe Deer (Capreolus capreolus)

Herein, we report the first incidence of systemic besnoitiosis in a male juvenile
roe deer Capreolus capreolus. The animal was found dead in an area where bovine
besnoitiosis is endemic and showed cachexia and multiple skin erosions in the
metacarpal and metatarsal areas. Moreover, round and elevated white structures
suggestive of Besnoitia spp. tissue cysts were also present. Twenty-eight tissue
samples from different anatomical locations were collected for microscopic lesion
and parasite detection through histopathology and PCR. Immunohistochemistry
was performed to confirm Besnoitia-positive reaction in the tissue cysts. In addition,
the identity of Besnoitia spp. in PCR-positive tissue samples was also investigated
using microsatellite (MS) markers, and the comparison of protein
disulphide isomerase gene sequences (BbPDI) of B. besnoiti and B. tarandi isolated
from cattle and reindeer, respectively. Besnoitia cysts were detected in the
skin (several parts), respiratory and upper digestive tracts, eyes, kidney, liver, testicle,
cardiac muscle and lymphoid tissue. Remarkably, the presence of tissue cysts
in the brain confirmed the capacity of Besnoitia spp. to form tissue cysts in the
central nervous system (CNS). Finally, the Besnoitia species detected showed the
same MS genotype as B. besnoiti, and BbPDI sequences from roe deer and two
B. besnoiti isolates were genetically identical throughout multiple sequence alignment.
Thus, for the first time, there is evidence that roe deer might act as an intermediate
host of B. besnoiti. Further molecular analyses and parasite isolations are
needed to corroborate these findings.