Survival of Pasteurella Tularensis in Flea Larvae

The results obtained indicate that if larval Nosopsyllus fasciatus imbibe viable tularaemia bacteria, a significant number of the organisms survive for up to 3 days. Xenopsylla cheopis larvae fed on dried blood, in which Pasteurella tularensis survives poorly, ingest few viable bacteria. No P. tularensis was detected in larval X. cheopis after 24 hr. Adults or pupae of both N. fasciatus and X. cheopis, which metamorphosed from flea larvae fed respectively on liquid and dried blood containing P. tularensis, did not produce tularaemia when macerated and inoculated into mice. The rate at which imbibed P. tularensis is lost in larvae is not necessarily the same in nature. Unless, however, naturally occurring P. tularensis are very specially adapted in this respect, the results indicate that even if N. fasciatus larvae imbibe P. tularensis this would have little or no epidemiological significance.