Does Melatonin Trigger Hypobiosis?
In temperate climates, barber pole worms enter a period of inactivity (arrested development) during the late fall and early winter. Melatonin, with its release having a direct relationship to length of night, is highest during this period. Combining melatonin’s relationship to the seasons, along with research demonstrating that melatonin can inhibit locomotion in parasites such as Caenorhabditis elegans, it was predicted that melatonin is the cue for Haemonchus contortus to enter hypobiosis.
University of Maine researchers designed an experiment to test the hypothesis that melatonin is the cue for H. contortus to enter hypobiosis. Effects of melatonin levels on development of H. contortus were determined by manually deworming and inoculating 16 adult Icelandic ewes, followed by twice-daily doses of 5 mg of melatonin for three weeks. FEC, body condition scores (BCS), and FAMACHA© scores were determined every three to four days during the experiment.
While administration of melatonin increased melatonin levels, it had no effect on the other parameters measured. Due to inadequate parasite colonization of ewes during inoculation, the researchers were unable to prove or test their hypothesis.