PATHOGENICITY OF TRYPANOSOMA VIVAX ISOLATES FROM TSETSE AND NON-TSETSE INFESTED AREAS OF NORTHWEST ETHIOPIA IN EXPERIMENTALLY INFECTED CALVES: BIOCHEMICAL, CYTOKINE AND CLINICO-PATHOLOGICAL EXAMINATION
No Thumbnail Available
Date
2014-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Trypanosomosis is a protozoan disease of animals and humans in sub-Saharan Africa. In Ethiopia, particularly the northwest region is affected by both tsetse and non-tsetse transmitted trypanosomosis. The objectives of the present study were to determine biochemical changes, cytokine responses and clinicopathological findings and compare differences in virulence of Trypanosoma vivax infection between tsetse and non-tsetse infested areas of northwest Ethiopia. Sixteen calves were experimentally infected with T. vivax isolates from tsetse and tsetse free area of selected sites which was originally isolated from naturally infected cattle to study the hematological, biochemical, histopathological and major cytokine alterations during the evolution of the disease. The animals were divided in four groups, TT, NT1, NT2 and NIC, each consisting of four infected (TT, NT1 and NT2) and four (NIC) control animals, respectively. The animals were kept in strict hygienic conditions and on a zero grazing schedule. Animals of group TT, NT1 and NT2 were exposed to 1 x 106trypanosome/ml (2ml of blood) intravenously. The course of the experimental infection was followed up to 11 weeks. Non-infected control animals demonstrated a progressive and significantly higher weight gain (16.3% or 12kg at the end of the study period) compared to infected groups (P<0.001). Hematological analyses of the infected calves revealed a marked decline in hemoglobin (P<0.001) and packed-cell volume (P<0.001). In addition there was a significant difference in Hgb values between TT and NT2 (P<0.013); in PCV values between TT and NT1 (P<0.024); TT and NT2 (P<0.001). Biochemical analyses showed decreased serum albumin (P<0.001), serum cholesterol (P<0.001), glucose (P<0.001) values and increased AST (P<0.05), ALT (P<0.001) and ALP (P>0.05) values in all challenged groups following infection as compared to the control. On the other hand, serum total protein (P>0.05) showed decrease in the mean values at early stage of infection and start to increase throughout the experiment in all groups. There was no significant decrease in mean glucose values between TT and NT1 (P>0.05), but there was significant decrease among TT and NT2 (P<0.001). However, there was no significant decrease in mean
2
values of albumin, cholesterol and total protein between TT and NT1; TT and NT2. There was significant increase in values of AST between TT and NT1 (P<0.05); no significant increase between TT and NT2 (P>0.05). In addition, there was no significant increase in mean values of ALT and ALP between TT and NT1; TT and NT2. In this study cytokine assays also showed an increase in the production of TNF- α, IFN- γ, IL-10 and IL-12 except for group NT1 for all cytokine assayed. There was significant increase in IFN- γ between TT and NT2 (P<0.001), TT and non-infected control (P<0.001). Moreover there was significant increase in the values of IL-10, IFN γ and IL-12 between TT and NIC (P<0.001); TT and NT1 (P<0.001); TT and NT2 (P<0.001). At necropsy, infected calves showed enlarged and hemorrhagic spleen; swollen, edematous and enlargement of prescapular lymph nodes; pneumonic and emphysematous lung; liver was enlarged, edematous with rounded edge. However, the post mortem examination of the animal in the control group did not reveal any significant gross lesions. The histopathological examination also conform the presence of significant abnormalities on major organs characterized by lymphoid hyperplasia in the white and red pulp of the spleen, interstitial pneumonia, zonal sever hepatic necrosis, tubulo-interstitial nephritis, multifocal myocarditis, meningoencephalitis, lymphoid hyperplasia in lymph node and mononuclear cell infiltration. In conclusion T. vivax isolates from both areas showed a variety of virulence factors leading to the development of acute clinical signs, reduction of PCV, decrease in biochemical values as well as increase in serum enzymes. In addition excessive secretion of cytokines, gross pathological lesion and histopathological abnormalities on major organs in the infected groups are manifestations of pathogenicity. However, the occurrence of parasitaemia and clinical signs were earlier in the NT groups compared to TT group. Therefore, equal attention is required for the control of trypanosomosis in both tsetse and non-tsetse infested areas of northwest Ethiopia.
Description
Keywords
Calves, Experimental infection, Pathogenicity, T. vivax, North West Ethiopia