How does vector maternal ecology influence the spread of disease in live-bearing tsetse flies?
Supervisor: Dr Sinead English
Potential co-supervisors: Professor Mike Bonsall (Oxford), Dr Lee Haines (LSTM), Professor John Hargrove (University of Stellenbosch)
Predictive models of vector-borne disease depend on an understanding of relevant vector biology, but the evolutionary ecology of many arthropod vectors – particularly in the wild – is often poorly characterized. In particular, in spite of a wealth of evolutionary theoretical models and empirical studies on how mothers can influence their offspring's survival and fitness, how these processes interact with disease spread in insect vectors is not known. The tsetse fly, which transmit trypanosomes, is the ideal model to study these effects. This vector has extraordinary maternal investment: unlike most other flies, tsetse fly mothers give birth to live, single young that weigh more and contain more fat than their mothers. Until recently, it has been difficult to sample heavily pregnant female flies in the wild, as they do not approach traps. The use of artificial warthog burrows enables the capture of such females and can bring new insights on the link between maternal and offspring traits in the wild. Similarly, most studies in the laboratory have not explicitly considered maternal age effects on offspring physiology – which is surprising, as they are relatively long-lived.
This PhD project will exploit new field methods and a rich laboratory resource, where females are kept in separate trays according to their age, to address how maternal age and nutrition influence offspring immunity in wild and captive tsetse flies.
What the student will be doing:
The student will conduct fieldwork in the Zambezi Valley in Zimbabwe, sampling flies with the artificial burrows method to measure maternal age and nutrition, offspring sex, size, fat content and infection status. The student will also conduct experiments on tsetse flies in the Liverpool School of Tropical Medicine colony, manipulating maternal nutrition across a range of ages, to examine the interplay between these factors and their effect on offspring size and immunity. Immunity can be tested directly by feeding flies with trypanosome-infected blood meals and measuring their subsequent immune status. Together, this PhD project will contribute to our understanding of an important disease vector with a fascinating ecology.