Prevalence pattern and biology of Sarcocystis capracanis infection in the Egyptian goats: a light and ultrastructural study.

Cysts of Sarcocystis capracanis obtained from infected goats were examined to clarify the effect of the parasite on the host. Muscle tissues from fresh oesophagus, tongue, diaphragm and skeletal muscles of 680 goats were slaughtered in the main abattoir of Cairo, Egypt and they were examined microscopically for Sarcocystis infection for the first time in Egypt. 540 out of 680 (79.4%) of examined goats were found to be infected with Sarcocystis sp. The infection was recorded firstly by light microscopy as spindle shaped cysts embedded in the muscle tissues. The validity of this species as S. capracanis was confirmed by means of ultrastructural characteristics of the primary cyst wall which revealed the presence of thick-radially striated wall with finger like projections, underlined by a thick layer of ground substance enclosing the developing metrocytes and merozoites that usually contain nearly all the structures of the apical complex and fill the interior cavity of the cyst. The cyst cavity is divided by many septa extending from the ground substance and producing large number of chambers. An experimental infection using the highly infected muscles was carried out to determine the final host, which is dog. Smears of intestinal epithelium were taken to examine the endogenous stages (gamogony and sporogony) by means of light microscopy. These stages were mainly observed as to infect the lamina propria of the posterior third of the small intestine. Gamogony and zygote formation (fertilization) occurred 2-8 days post infection, while sporulation took place within the final host 13-15 days and sporocysts were passed within faeces of the infected puppies at that time. The prepatent period of S. capracanis was 12-15 days, while the patent period was extended to 37 days. In goats, infection with S. capracanis led to the loss of weight, anaemia, abortion and even death in cases of heavy infection. While bleeding, watery faeces filled with mucous on 5th and 8th day p.i. as well as intestinal lesions are the pathogenic effects occurred in puppies after experimental infection.