Validation of the Infectra-Kit in Malaria Transmission Studies Using Plasmodium Berghei

摘要

Pre-clinical transmission assays are essential for proof-of-concept for transmission blocking strategies but are hazardous to laboratory personnel and animal hosts as it entails exposure of live rodents to infected vectors. Conventional transmission assay methods include the use of anesthesia (associated with undesired side effects). In addition, animal handlers risk being bitten by experimental animals and vectors during anesthesia due to a lack of safe and effective alternatives. Robustness of rodent to vector transmission was determined by comparing the number of oocysts. Vector-to-rodent transmission was determined by measuring parasitemia, gametocytemia, changes in body weight and survival time. A completely randomized design was used in this study. Rodent-to-vector transmission was analyzed by log linear model. Fecundity, gametocytemia, parasitaemia and changes in body weight were analyzed by regression analysis. Survival times were analyzed Kaplan-Meier method for determination of survival distribution function. Rank test of homogeneity were used to determine the effect of restraining method infection on survival times. There was no significant difference (p<0.001) in fecundity of mosquitoes fed on anesthetized mice; 122±22.1 eggs compared to INFECTRA-Kit group with 110±14.1 eggs. Oocyst production increased gradually though not significantly (p<0.001) in both groups of mice with the number of mosquitoes. The INFECTRA-Kit group increased from 2.7%±0.3 (1 mosquito) to 9.3%±0.3 (6 mosquitoes), the conventional group was 3.7%±0.3 to 8.6%±0.3 (6 mosquitoes). Parasitemia progression was characterized by two waves in INFECTRA-Kit and three waves in the conventional group. The highest parasitaemia peak was 22% attained on 22dpi for the INFECTRA-Kit and 17.8% attained on 26 dpi for the conventional group. Gametocytes were detected on 16 dpi in both groups and thereafter increased significantly (p<0.001) with dpi. In the INFECTRA-Kit group, gametocytemia was represented by two oscillations while the conventional group was three cycles with peak gametocytes increasing with each subsequent peak. Disease progression was higher and survival times shorter with INFECTRA-Kit than with anesthetized mice and there was no significant difference (p<0.05) between the two methods in body weight and gametocytemia. INFECTRA-Kit is equivalent to that of anesthesia method but more advantageous given the more ethical and humane treatment of animals.