IMMUNIZATION OF RABBITS WITH A MIDGUT EXTRACT OF THE HUMAN-BODY LOUSEPEDICULUS-HUMANUS-HUMANUS - THE EFFECT OF INDUCED RESISTANCE ON THE LOUSE POPULATION

Resistance to human body lice, Pediculus humanus humanus L, induced by feeding on rabbits immunized with an extract of louse gut was studied . The mortality of lice fed on immunized rabbits was 73%, significantl y higher than that of lice fed on control rabbits (52%) (P < 0.01). Th e proportion of dead nymphs and female lice with ruptured guts was sig nificantly higher in lice fed on immunized rabbits (P < 0.01). The siz e of the bloodmeal was 35% greater in female lice fed on control rabbi ts than on immunized rabbits. Lice fed on immunized rabbits laid 40% l ess eggs than those fed on the controls, they also demonstrated a sign ificant decrease in the number of eggs per female over time (P < 0.01) . 86% of the eggs laid by lice fed on immunized animals hatched, compa red with 92% hatching of eggs laid by the lice fed on control animals (P < 0.01). With the exception of the first bloodmeal the percentage o f hatched eggs which were laid between any two bloodmeals was signific antly smaller (P < 0.01) in the lice fed on immunized rabbits than in the control group. The first nymphal stage of lice fed on immunized ra bbits took an average of 5.2 days to moult to the second stage, compar ed with 4 days for those fed on control rabbits.