Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 1994
Publication Date: N/A
Interpretive Summary: Major sources of infective larvae of parasitic diseases of sheep occur nonrandomly throughout the year. Spring rise, or periparturient egg rise, refers to the massive increase in fecal nematode egg production in ewes near, or after, parturition. The mechanism that signals the reproductive status of the host to the gastrointestinal parasite is unknown. This research examined the effects of administering systematically two reproductive hormones, prolactin and prostaglandin, on various aspects of experimental stomach worm infections in lambs. Prolactin increased nematode egg production during week 2 of the infection. Bovalene, a prostaglandin analogue increased survivorship of the parasites. No apparent interaction occurred with these two hormones. Further knowledge on the mechanism of action of prolactin on fecundity and Bovalene on survivorship would provide avenues of drug development and husbandry to minimize parasite transmission.
Technical Abstract: Regulation of periparturient nematode egg rise in sheep can not be studied outside the host. Experiments were designed in lambs to examine the potential roles of two reproductive hormones, prostaglandin and prolactin, in the regulation of nematode growth, fecundity and survivorship. in the first experiment, prolactin (25 I.U./lamb/day) was administered to lambs during each of the first three weeks of patency of Haemonchus contortus infections. During week 1 of patency, fecundity (eggs/female/day) was significantly higher in the prolactin-treatment group. However, total daily egg concentration was highest in this group during week 2 of patency. In the second experiment, a prostaglandin analogue, Bovalene, was injected daily with or without exogenous prolactin throughout the first three weeks of patency. Bovalene decreased survivorship of both adult male and female worms and increased fecal egg concentrations throughtout patency. Additive or synergistic effects of prolactin and Bovalene were not evident from this experiment.