In this PSI Seminar, Dr Helen Esser, Wageningen University will present ‘From local to continental: how vector ecology shapes tick‑borne disease emergence in Europe.’ The session will be hosted by PSI and chaired by Marieke de Swart. The seminar will take place on Tuesday, 17 February 2026 from 15.00 to 16.30. Following the seminar, tea and cake will be provided, along with an opportunity to network with attendees.

About the speaker
Helen Esser is an assistant professor at the Wildlife Ecology and Conservation Group at Wageningen University & Research, the Netherlands. Esser is a disease ecologist whose research examines how environmental change, such as biodiversity loss and land-use change, alters host-vector interactions and creates conditions for pathogen emergence. By combining field studies with ecological modelling, she studies the mechanisms that drive the emergence of wildlife and vector-borne diseases.

Seminar outline
The ecology of arthropod vectors, such as ticks and mosquitoes, plays a crucial yet often underappreciated role in the emergence and spread of zoonotic pathogens. In many vector-borne disease systems, transmission is highly uneven: a minority of hosts account for most new infections.

Tick borne encephalitis virus (TBEV), medically the most important arbovirus in Europe, is a clear example. Its persistence depends on ticks feeding in close proximity on the same rodent, even when that rodent is immune.
This so-called co-feeding transmission occurs on only a small fraction of rodents and was historically associated with specific climatic conditions. Nevertheless, TBEV has recently expanded into parts of northwestern Europe previously considered climatically unsuitable, including England. The ecological conditions promoting TBEV transmission in these new areas of emergence remain poorly understood.