Infection by the warble fly Przhevalskiana silenus Brauer, 1858, in the Italian goats. An update up to 1988.

This paper is a review of the work done at the University of Bari on the goat warble fly Przhevalskiana silenus Brauer, 1858. It reports data concerning taxonomy, biology, and epidemiology of the goat warble fly, as well as therapy against the infection. Grunin in 1962, and later Madel in 1969, were the first researchers to reach the conclusion that the three species of Przhevalskiana up to then recognized--namely P. silenus, P. aegagri, and P. crossii--should be unified in just one--Przhevalskiana silenus. The genetical studies conducted by us on the third instar larvae with the use of 9 gene-enzyme systems confirmed the assumption that P. silenus is the only species which parasitizes goats. Studies were conducted on the external life-cycle of the parasite with the purpose of elucidating the relationship existing among time of dropping, length of time needed for adults to emerge from pupae, and temperature of the environment. Both total sum of temperature and length of time seem to play an important role in determining the duration of the pupal stage. Epidemiological data derived from a two-year survey carried out in six infected groups of goats are also reported. The interrelationship existing among prevalence, mean intensity, variance, variance/mean rate, and parameter K of the negative binomial are presented. It appears that age, parameter K, and variance of infection intensity are closely related. A trial experiment was also carried out to evaluate the efficacy of ivermectin against a natural infection with P. silenus larvae. A single subcutaneous injection of 1% ivermectin was given, at doses of 50, 100 or 200 micrograms/kg b.w. The drug was found to be fully effective at all three doses.