Variation in the susceptibility of 6 Strains of Mouse to Infection with Trypanosoma evansi

Abstract

The mouse inocuIation test MI is generally considered the most sensitive method for the detection of T.evansi in blood from infected animals. However, the effect that strain of mouse used may have on the sensitivity of the test is not known. It was investigated in this study. Forty mice from each of 4 inbred strains (BALB/c, DPJ, CBA/CaH and C57BL/6J) and 2 outbred strains (ARC and Quackenbush) were inoculated in groups of ten, by intraperitoneal injection, with 0.3ml of bovine blood containing 1000, 125, 25 or 0 T. evansi per ml. Mortality was monitored twice daily and parasitaemia score was recorded every 2-3 days for 21 days. Totals of 96%, 100% and 95% of the mice from all strains developed detectable parasitaemia when inoculated with blood containing 1000, 125, or 25 T. Evansi per ml of blood respectively. CBA/CaH mice survived significantly longer (11.6 days) than Quackenbush, BALB/c and C57BL/6J mice (8.8, 8.2 and 8.8 days respectively) inoculated with blood containing 125 T. Evansi per ml (P<0.05). However, there was no measurable difference in duration of survival of mice from different strains when inoculated with blood containing 1000 or 125 T. evansi per ml. It was concluded that the choice of mouse strain for use in MI test is unimportant and that practical considerations such as coIour and robustness are more important in deciding on an appropriate strain. Of the six strains evaluated, the BALB/c strain was considered the strain of choice as it was the most robust, is readily available in laboratory colonies and, being white, identifying marks made on the coat with hair dye were easy to visualise.