Bovine Demodicosis: Prevalence, Clinico-pathological and Diagnostic Study

摘要

A National survey of bovine demodicosis was conducted in five States in the Sudan during vaccination campaigns and in abattoirs. The total number of cattle surveyed was 48,000. Among the total number of animals surveyed, 16,608 cattle had skin lesions of demodectic mange. Visible lesions were encountered among 14,562 cattle (87.7 %), while the remaining 2,046 animals (12.3 %) had palpable lesions. Five forms of skin lesions were recognized, namely; papules, nodules and papules, nodules and few pustules, pustules and few nodules or pustules and crust-covered lesions. The lesions were confined to certain parts of the body or generalized. Infected cattle had decreased total RBC, PCV and Hb, and their red cell indices showed that they had anaemia of the normocytic normochromic type. Moreover, they had an absolute increase in the WBC, marked eosinophilia and moderate neutrophilia. Demodex bovis mites were isolated from the infected purulent material expressed from skin lesions. The mites and associated primary pathogenic bacteria and secondary invading organisms caused distension of the hair follicles forming bladder-like cysts and resulted in a marked destruction of the hides. Liberation of the contents of the cysts in the surrounding tissue produced a typical granulomatous reaction. The central core of the infection composed of mites, bacteria and purulent exudate was infiltrated by neutrophils and a few eosinophils; surrounded by lymphocytes, plasma cells, macrophages, epithelioid and giant cells, and proliferation of connective tissue. The giant cells destroyed, engulfed and digested the bacteria and the mites, resulting in healing of the lesions as judged by the progressive proliferation of connective tissue and degeneration of the granulomas.