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The pathological effects of infections of Dispharynx nasuta (Nematoda : spiruroidea) on the blue grouse Dendragapus obscurus (Say) Jensen, Doris Nestler

Abstract

The pathological effects of infections of Dlspharynx nasuta (Nematoda: Acuariidae) on confined, experiment ally-infected chicks of the blue grouse, Dendragapus obscurus, have been studied. The severity of the infection was found to be directly proportional to the number of worms present and the youth of the host. The development of the lesion produced at the site of infection, the proventriculus of the host, is described and its papillomatous nature confirmed. The previously unknown developmental stages of D. nasuta in the avian host are described and related both to the formation of the lesion and to the disease process. The growth of infected birds, expressed as gain in weight, was less than that of the controls although food intake studies indicated that the amount of food eaten by both groups was comparable. Calcium and phosphorus analyses on bones gave no indication that the mineral metabolism of infected birds was affected although their bones broke more readily than those of the controls. Development of the Juvenal feathers which appear from 3 to 5 weeks of age may be severely retarded. These observations suggest that the protein metabolism of the host is impaired. The numbers of hemocytes of infected grouse fluctuate greatly and show two critical low periods. The first, occurring immediately after infection, can be correlated with the invasion of the larvae and possibly to a substance secreted by them. The second occurs 2 to 3 weeks after initial infection and can be correlated with local irritation and hemorrhages and perhaps the moult of the larvae. Chronic hematological symptoms are anemia and leucocytosis. The latter is characterized by heterophil ia, eosinophilopenia, lymphocytosis of small forms and lymphopenia of the larger forms. The presence of circulating antibodies for D. nasuta was not demonstrated with the techniques used. The evidence suggests that the host tissue reaction may be an allergic response. Several ecological questions concerning the survival of D. nasuta during the winter months, temperature for larval development in the intermediate host, longevity of adult D. nasuta in the definitive host, infection and reinfection of adult blue grouse, are considered. In the laboratory, infections of 16 and 22 worms, administered to the host before 2 weeks of age, were fatal. Results of these experiments indicate that D. nasuta is a debilitating pathogen which may prove fatal and, may act as a controlling factor of natural grouse populations.

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