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Erythrocyte surface and free serum sialic acid concentrations were determined during experimental Trypanosoma vivax infection in cattle. All infected calves developed mild trypanosomiasis, with significant decreases in mean packed cell volume occurring 15, 16, 20, 22 and 24 days after infection. The anaemia was preceded by significant decreases in mean erythrocyte surface sialic acid concentrations on days 7, 13 and 14, with yet another significant decrease on day 31 after infection. These decreases in erythrocyte surface sialic acid concentrations coincided with the parasitaemic waves. Free serum sialic acid concentration, however, showed an increase, though non-significantly, on day 8, which coincided with both a decrease in erythrocyte surface sialic acid and the initial parasitaemic wave. It is postulated that the early anaemia observed in infected animals may be attributable to the activities of the circulating trypanosomes which produce neuraminidase which, in turn, cleaves off surface sialic acid, thus rendering the erythrocyte more prone to phagocytosis by the recticuloendothelial system.

The course of trypanosomiasis was observed over a period of 68 days in eight red sokoto goats experimentally infected with Trypanosoma vivax strain Y58. The goats developed parasitaemia five days after infection; the intensity of parasitaemia varied within and between individual goats. The course of the disease was acute, subacute or chronic. Anaemia was the principal clinicopathological feature of the disease. The rate of development of anaemia was not related to the degree of parasitaemia. Other clinical signs included emaciation, weakness, rough hair coat, profuse lacrimation and development of corneal opacity. Bone marrow of infected goats showed marked erythroid hyperplasia. Erythrophagocytosis and haemosiderosis in the bone marrow, liver and spleen were the principal histopathogical features in infected goats.

The variations with age in serum iron concentration and iron-binding capacity in zebu cattle were investigated. Serum iron concentration was lower in calves from birth to four weeks of age than in older cattle. Total iron-binding capacity decreased while percentage saturation increased with advancing age.