EFFECTS OF EXOGENOUS REPRODUCTIVE HORMONES ON HAEMONCHUS-CONTORTUS POPULATIONS IN LAMBS

The potential roles of 2 reproductive hormones, prolactin and prostagl andin, in the regulation of nematode growth, fecundity, and survival i n lambs were examined in 2 experiments. In the first experiment, prola ctin (25 IU/lamb) was administered to 3 groups of lambs at 1-wk interv als during each of the first 3 wk of patency of Haemonchus contortus i nfections, respectively. Fecundity (eggs/female/day) and total daily e gg production were significantly higher in the group treated with prol actin during week 2 of patency. Male worms were significantly longer, and female worms were significantly shorter after each weekly treatmen t with prolactin. In experiment 2, a prostaglandin F-2 alpha. analogue , BOVILENE(R) (0.25 mg/lamb), was injected daily with or without exoge nous prolactin (25 IU/lamb) throughout the first 3 wk of patency, the period of highest egg production. BOVILENE treatment resulted in decre ased survival of both adult male and female worms and increased fecal egg concentrations, as estimated on a daily basis throughout this peri od. The interactions of BOVILENE with prolactin were negative relative to total daily egg production and worm growth at the terminus of the experiment (day 42 postinoculation). Additive or synergistic effects o f prolactin and BOVILENE were not evident relative to fecundity. Decre ased survival of worms from treatment with this potent prostaglandin a nalogue alone is intriguing for parasite control applications.