Exposure of Tribolium confusum to thio-TEPA, and its effect upon development of Hymenolepis diminuta cysticercoids

Abstract

Flour beetles, Tribolium confusum, were exposed to concentrations of thio-TEPA equivalent to 10, 20, 40, and 80 mg/sq ft for either 1, 2, or 3 hours. The exposures were made at varying times over a 3-week period from 6 days before the beetles were infected with the eggs of Hymenolepis diminuta, to 15 days after the beetles were infected. When the cysticercoids are more than 6 days old, exposure of the vectors to thio-TEPA has no significant effect on their development, irrespective of both the strength and length of time of exposure. The mortality of cysticercoids up to 3 days old is high and depends on the strength of thio-TEPA and the age of the cysticercoids. Exposure of the beetles 72 hours or more before infection resulted in no significant decrease in the number of cysticercoids developing. Exposure 48 hours or less before infection resulted in a highly significant ( p < 0.001) reduction in the number of cysticercoids which developed. There is a 5-day period corresponding to 2 days prior to infection until 3 days after infection, during which exposure of the vectors to thio-TEPA causes up to 100% mortality of the cysticercoids. Within this period there is some evidence that the strength of the thio-TEPA deposit is also significant. Irrespective of length of exposure time or strength of chemosterilant deposit, those cysticercoids that managed to develop were also capable of establishing themselves in the definitive host and of reaching maturity.