Full Length Research Paper

Effect of immunomodulation with levamisole on the course and pathogenesis of acute experimental Trypanosoma congolense infection in sheep

Mohammed Bisalla¹*, Sani Adamu¹, Najume Doguwar-Giginya Ibrahim¹, Idris Alao Lawal² and King Akpofure Nelson Esievo¹

¹Department of Pathology and Microbiology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria. Nigeria.

²Department of Parasitology and Entomology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria.

*Corresponding author. E-mail: mbisng@yahoo.com. Tel: +2348028435838.

Accepted 16 January, 2009

The effect of immunomodulation with levamisole on the pathogenesis and course of acute experimental Trypanosoma congolense infection in sheep was studied. Eighteen Yankasa sheep were divided into three groups: Group A- six (T. congolense infected), Group B- seven (T. congolense infected, immunomodulated) and Group C- five (uninfected controls). Groups A and B sheep were each infected with approximately 2×10⁶ trypanosomes. In addition, group B sheep were each administered 2.5 mg/kg levamisole hydrochloride subcutaneously on the day of infection and later weekly throughout the experimental period. Clinical signs, appearance and level of parasitemia, PCV, rectal temperatures, total and differential leukocyte counts and body weights were monitored. Clinical signs observed were pale mucous membranes (anaemia), weakness and rough hair coats which were milder in group B sheep. Group B sheep became parasitemic two days earlier than group A and maintained a higher parasitemia at the first peak. The mean PCV decreased significantly (p<0.001) in groups A and B when compared to the controls. Mean rectal temperature decreased significantly (p<0.001) in the infected groups when compared to the controls. Mean total leukocyte counts increased significantly (p<0.001) in group B when compared to groups A and C. Absolute lymphocyte counts increased significantly in group B (p<0.001) when compared to groups A and C. There was no statistically significant difference (p>0.05) in the absolute values of neutrophils, monocytes and eosinophils in all the groups throughout the experimental period. Also there was no statistically significant difference (p>0.05) in the mean body weights in all the groups. The immunomodulation with levamisole of acute experimental T. congolense infection in sheep appears to have led to an early onset of parasitemia with a leukocytosis and a lymphocytosis.

Key words: Sheep, trypanosomosis, immunomodulation, levamisole.