Abstract
BackgroundEthiopia, particularly in the Northwest region, is affected by both tsetse and non-tsetse fly transmitted trypanosomosis, with significant impact on livestock productivity. The aim of this study was to determine and compare clinical findings and haematological values between experimental infections induced by Trypanosoma vivax isolates from areas of either transmission mode. Sixteen young (aged between 6 and 12 months) Zebu cattle (Bos indicus), purchased from a trypanosome-free area and confirmed to be trypanosome-negative, were randomly assigned into four groups of four animals. Groups 1, 2 and 3 were infected with an isolate from a tsetse infested or one of two isolates from a non-tsetse infested area, and group 4 was a non-infected control. All animals in the infected groups were inoculated intravenously with 2 × 106 trypanosomes from donor animals. The experimental animals were monitored for eight consecutive weeks post infection for clinical signs, parasitaemia and haematological changes in packed cell volume (PCV), haemoglobin concentration (Hgb), total red blood cell (RBC) and white blood cell (WBC) counts, differential WBC count and blood indices (mean corpuscular volume [MCV], mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration).ResultsInfection was characterized by reduced feed intake, weakness, pyrexia, parasitaemia, rough hair coat, enlarged prescapular lymph nodes, lacrimation, weight loss, pallor mucus membrane and dehydration. Body weight loss in all infected groups was significantly higher than in the non-infected control. Similarly, body weight loss was higher (P < 0.001) in animals infected with the tsetse infested isolate than with the non-tsetse infested isolates. The mean PCV, Hgb, total RBC and WBC counts were lower (P < 0.001), and mean MCV was higher (P = 0.01) in all infected groups than in non-infected control animals at different time points during the study period. Except for minor variations in haematological values, the overall changes were similar in all infected groups.ConclusionClinical signs and significant reduction in haematological values in the infected groups indicated the pathogenicity of the T. vivax parasites. Pathogenicity of T. vivax from the non-tsetse infested area can be considered as nearly as important as that of its counterpart derived from the tsetse infested area.
Highlights
Trypanosomosis is a parasitic disease caused by different species of flagellated protozoa belonging to the genus Trypanosoma which inhabit the blood, various body tissues and fluids of vertebrate hosts
Clinical findings and appearance of parasitaemia All the infected cattle developed clinical trypanosomosis, which was characterized by a variety of clinical signs
The temperature of infected animals started rising from the post infection day (PID) 4, coincident with the appearance of parasitaemia, and fluctuated throughout the study period (Fig. 1b)
Summary
Trypanosomosis is a parasitic disease caused by different species of flagellated protozoa belonging to the genus Trypanosoma which inhabit the blood, various body tissues and fluids of vertebrate hosts. T. vivax presents a short and simple life cycle in contrast with T. brucei and, to a lesser extent, with T. congolense [5] This simpler life cycle is thought to have enabled T. vivax to adapt to different vectors and hosts, possibly explaining why it has emerged rapidly in South America and non-tsetse infested regions of Africa [6, 7]. T. vivax is distributed in both tsetse infested and non-tsetse infested areas, while T. congolense is restricted to tsetse infested areas Both species of trypanosome affect a large number of domestic animals, and mainly cattle, which are integral to crop production in Ethiopia. In the Northwest region, is affected by both tsetse and non-tsetse fly transmitted trypanosomosis, with significant impact on livestock productivity. The experimental animals were monitored for eight consecutive weeks post infection for clinical signs, parasitaemia and haematological changes in packed cell volume (PCV), haemoglobin concentration (Hgb), total red blood cell (RBC) and white blood cell (WBC) counts, differential WBC count and blood indices (mean corpuscular volume [MCV], mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration)
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