Comparative Infectivity and Pathogenicity of Kano and Sokoto (Northern Nigeria) Isolates of Trypanosoma Evansi in Rabbits

Abstract

The present study was aimed at comparing the infectivity and pathogenicity of two isolates of Trypanosoma evansi in experimentally infected rabbits. Three groups each of five crossbred rabbits, two of which were challenged with approximately 2 x 106 T evansi of the Kano (KT) and Sokoto (ST) isolates, respectively, while the third group was the uninfected control (UC). The rabbits were monitored for parasitaemia, rectal temperature, clinical signs and changes in the packed cell volume (PCV), total leukocyte count and total plasma protein during the course of the infection. Impression smears of the brain, liver, lungs, heart, spleen, kidney, adrenal gland, bone marrow and aqueous humour were made, stained with Giemsa and examined for the presence of trypanosomes. The result revealed that all the infected rabbits developed intermittent fever and parasitaemia, with mean pre-patent periods of 3.6±1.8 and 7.8±3.1 days for the KT and ST groups, respectively. There was a decrease in mean PCV of the infected groups compared with the control. The KT group had the lowest PCV throughout the study compared with the ST and UC groups. There was a significant inverse correlation (r = -0.7262, P < 0.05) between parasitaemia and the PCV in the KT group, but not in the ST group (r = -0.6070, P > 0.05). Leukocytosis was higher in the ST group compared with the KT group all through the study, and was significantly higher (P < 0.05) at days 11 and 18 post infection. Trypanosomes were observed in 56% of the organ impression smears from the KT group as against 11% in the ST isolate. Both isolates were infective to the rabbits, but the KT isolate appears to be more virulent than the ST isolate.

Keywords: Trypanosoma evansi isolates, pathogenicity, rabbits, Northern Nigeria