284 PARASITES OF THE DOMESTIC ANIMALS 



United States. The nodules are due to the larvae which live embedded in 

 the connective tissue of the submocosa, to which they at once penetrate 

 after being taken up by the host. According to Marmotel, after six to 

 seven months of development in this location, they pass to the intes- 

 tinal lumen where they become sexually mature and the female, after cop- 

 ulation, deposits her eggs. The eggs pass from the host animal with the 

 feces and promptly hatch if they meet with favorable conditions of heat 

 and moisture. The further development outside of a host is not known. 



Natural infection probably takes place by food and water from wet 

 marshy pastures. If it occurs during August and September the larvae 

 will pass from the nodules into the intestinal lumen during March and 

 April, here attaining maturity and copulating in July and August. 



Post-mortem Appearance. — The nodules are most commonly found 

 in the wall of the cecum and colon, but they may occur in the small 

 intestine and at times on the liver and other abdominal organs. They 

 may be isolated, but are frequently massed in hundreds and thousands. 

 In size they vary from that of a pinhead to that of a pea, or they maj^ 

 be considerably larger. Their color varies from blackish in the smaller 

 ones to grayish white in the larger. The connective tissue capsule of 

 the nodule is thick, and, as the nodule increases in size, it becomes filled 

 with a greenish cheesy or purulent material, later becoming calcareous. 

 Only the younger noclules contain the larvae. 



Symptoms. — Light infestations, with the presence of a few nodules, 

 are not, as a rule, accompanied by perceptible symptoms, the condition 

 in such cases being observed only after slaughtering. Relative to their 

 degree, heavier invasions may be accompanied by diarrhea without a 

 considerable loss of condition, or the diarrhea may be im controllable and 

 accompanied by progressive emaciation and anaemia. Such cases usually 

 terminate fatally after a course of two or three months, the animal 

 succumbing in a state of coma. The effect of the invasion will depend 

 considerably upon the age and vitality of the animals infested. 



Importance. — The fact that many slaughtered sheep that were ap- 

 parently perfectly healthy show these nodules tends to lead to the im- 

 pression that they are of little importance and has perhaps caused them 

 to be overlooked as a primary cause of death. Cases of nodular disease 

 submitted to the laboratory of the Pennsylvania Bureau of Ani- 

 mal Industry indicate that the disease may assume an enzootic char- 

 acter of severe type occasioning numerous losses. Usually where 

 there is high mortality there is heavy infestation with large areas of 

 massed nodules, though there are several factors which render this un- 

 necessary to a fatal termination. Lighter invasions may have this 

 result when by worms with a relatively high degree of virulence; when 

 the invaded animal has a low degree of resistance, or when other worms 

 are present to contribute to the morbid effect. Furthermore, these 



