Schistosoma (schistosomus) canine fetusKeywords: schistosoma, canine, fetus.
Schistosoma literally means "split body". The adjective schistosomus describes the noun schistosoma. The term schistosoma reflexus is often used incorrectly because the body wall is not reflected in all cases of schistosoma. In fact, other than in cattle, schistosoma reflexus is comparatively rare.
During the formation of the embryo, it folds inward on its ventral surface, as shown in this video. That process forms the gut from the endoderm. The umbilical cord is formed and the yolk sac, depleted in the process. On rare occasions, closure of the peritoneal cavity at the umbilicus is not complete. This allows the intestines and other viscera to lie free in the amnion.
The image below shows a case of schistosoma with evisceration in a canine fetus.
Schistosoma has been described in many mammals, including humans. Affected fetuses may live until term or be born live; usually by cesarean section. The condition has been particularly well described in cattle where it is indeed one of schistosoma reflexus; a cause of dystocia.
Schistosoma is thought to be heritable; at least in some cases. Indeed, abnormal karyotypes have been demonstrated in some cases in various species. In one report, an entire litter of puppies was affected, reflecting either a chromosomal or epigenetic etiology. However, its not clear to this author if the condition is always to be regarded as heritable and as a basis on which to cull animals from breeding programs. Clearly more knowledge is required in this regard.
Atasever, A. et al. 2015.A case of report Schistosoma reflexum in the 12 fetuses of Belgian Malinois dog. Kafkas Üniversitesi Veteriner Fakültesi Dergisi. 21: 937-941
Ozalp, G.R. 2011. A case of schistosoma reflexum in a cat with chromosomal aberrations. Reprod. Domestic Animals. 46: 373-376