Clinico-pathological and pathomorphological observations in trypanosoma vivax infection cattle

During infection with T. vivax (strain Y 58) four stages can be distinguished: (a) A prepatent period of about 1 week. (b) An acute or fulminating disease characterized by an almost continuous, fluctuating parasitaemia, a decrease of the number of thrombocytes, blood serotonin level, packed cell volume (PCV) and Hb, serum albumin and γ-globulin fractions, a low serum total lipid content and an initial rise with subsequent decrease of the blood bradykinin level. (c) A critical stage of about 4–5 weeks post infection (pi) during which the animal may develop a progressive parasitaemia and may die from disseminated intravascular coagulation. At necropsy microthrombi were a consistent and most significant observation. Accompanying features were oedema and haemorrhages in the various tissues, pulmonary oedema and lobular infarction, patches of necrosis in liver, spleen and adrenals and nephrotic changes in the kidneys. Perivascular mononuclear infiltrates, resulting in local granuloma formation (heart liver), were a constant feature. Related biochemical changes were an increase of the blood urea and serum lactate dehydrogenase levels. (d) A post-critical stage characterized by an ameliorating condition, periods with no or few trypanosomes in the peripheral blood alternating with relatively high peaks of parasitaemia. This was associated with increased blood bradykinin levels, an increase of the PCV and Hb, serum albumin and γ-globulin fractions, number of thrombocytes and blood serotonin level. A return to normal values of the serum total lipids was observed at this stage. Despite this clinical recovery of the animals, at necropsy (on days 90, 98, and 99 pi) there was a moderate to massive histiocyte-lymphocyte-plasma cellular infiltration of the heart, which led to cardiac insufficiency in two heifers.The rise of the d-amino laevulinic acid dehydratase levels of erythrocytes during the decline of the PCV and Hb values is an indication for the production of many young erythrocytes and thereby for the haemolytic nature of the anaemia.