Schistosomiasis japonica

Abstract

Dogs were infected with the cercaria of Schistosoma japonicum either by subcutaneous injection or by immersing the dogs in infected water. Eggs were first recovered from the feces of one heavily infected dog on the twenty-seventh day after infection, and from other dogs at various intervals up to about forty days. The dogs were sacrificed at various intervals after the appearance of eggs in the feces, from the twenty-eighth to the seventy-seventh day. Portions of intestine were excised, often while the dog was still alive under ether anesthesia, and were fixed in Zenker's solution or 10 per cent formalin. Blocks were embedded in paraffin and sections were stained with hematoxylin and eosin. From five dogs, killed on the 28th, 33rd, 40th, 63rd and 65th days after infection serial sections were cut from the blocks of tissue which showed the most intense pathology. I wish to emphasize here two features of the pathology which have not been described previously.

1. The earliest position of deposited eggs. On the twenty-eighth day after infection nearly all the deposited eggs were in the stroma of the mucosa; a few were in the submucosa. The eggs were in large or small groups containing up to 200 eggs in one group. The eggs of each group usually radiated out into the mucosa from a single point in the submucosa, and in many cases it could be seen that all the eggs were within distended venules and copillaries. They often extended nearly to the surface epithelium of the mucosa.

Male and female worms, always in copula, were found in distended veins in the submucosa. At this early stage there was no hemorrhage into the tissues and practically no tissue reaction about the deposited eggs.