Canine trypanosomosis: Clinical observations and morphological pathology associated with natural infection of Trypanosoma congolense in exotic breeds of dog in Abeokuta, Nigeria

Abstract

Clinical and pathological aspects of canine trypanosomosis were determined in naturally infected dogs presented to the Veterinary Teaching Hospital, Federal University of Agriculture, Abeokuta, at different times between 2012 and 2013. The breeds, sexes, ages and body weights of the dogs were recorded.  Clinical signs were observed. Blood samples were collected to determine their packed cell volumes  (PCVs) and parasitaemia. Post-mortem examinations were carried out on 6 dogs that died of the disease and tissue samples were collected and fixed in 10% buffered formalin for histopathology. Trypanosoma species was characterized using polymerase chain reaction. Trypansoma species detected by microscopy was confirmed as T. congolense savannah sub-type by PCR. Clinically, the dogs were anorexic, lethargic and showed lymphadenopathy. Their body temperatures ranged from 40-41.6oC,  Respiratory rates were 28-34/minute, 4 out of 6 cases examined at post-mortem showed epistaxis. The gross lesions were pale mucous membranes, severe pulmonary congestions, haemorrhages and oedema (4/6), marked hydrothorax measuring 1-2 litres (5/6), misshapen heart with petechial and ecchymotic haemorrhages in the epicardium (4/6), severely enlarged and icteric livers and splenomegaly. The intestinal mucous membranes were haemorrhagic (2/6), the kidneys were pale and the testes were haemorrhagic (2/6). Microscopic lesions were severe pulmonary congestion, haemorrhages, oedema and infiltration by inflammatory cells, severe haemorrhagic myocarditis, hyperplastic lymphodenopathy, varying degree of degeneration and necrosis with inflammatory reactions in the lungs, hearts, livers,  spleens and kidneys. The liver sinusoids were dilated and the hepatocytes show varying degree of fatty change. In some cases, hepatocytes were atrophic. In all the six cases, Trypanosome species were characterized as T. congolense savannah type. The pathogenicity of trypanosomes in dogs was discussed.

Keywords: trypanosomosis, clinical signs, parasitaemia, pathology, dogs. rhodesense.