Cecilia Pumpelly, a student at University of Georgia, worked with Dr. Andy Davis to evaluate transmission mode of a nematode parasite infecting beetles.
Abstract: Within the estimated one million species of nematodes, there are just as many variations in life cycles. While parasitic nematodes rely on their host for primary development, many will exit their host and enter a free-living adult stage before completing their transmission cycle. One such nematode, Chondronema passali, can be found by the hundreds in the hemocoel cavity of horned passalus beetles, Odontotaenius disjunctus. Previous research finds no presence of adult nematodes within the beetle, yet few persist in the burrow debris. This experiment seeks to find the mode by which C. passali exits the beetle to identify the overall transmission mode. Four main tests were conducted on nematode survival rates in 1) burrow debris of ovipositioning female beetles, 2) media commonly found in the burrow, 3) injured or euthanized beetles, and 4) beetle feces. Fourth stage juvenile nematodes were collected from dissected beetles and assessed according to an activity framework. Here we show that adult nematodes were not recovered from the burrow debris of ovipositioning beetles nor the body cavity of injured or necrotic beetles, and juvenile nematodes were unable to survive for more than two hours in any tested medium. However, additional research is needed to clarify the role of feces in transmission, as the adult beetles perform trophallaxis to feed larvae, providing a possible avenue for adult nematodes to be recovered in the burrow. Consideration of a dead-end or intermediate host relationship with a large, hardwood-dwelling mammal is also necessary.
