Host, vector, and parasite dynamics: exploring intrinsic and extrinsic factors shaping tick-borne filarial nematode...

Tick-borne filarial nematodes are a complex and understudied group of parasites that rely on ticks for transmission in vertebrates. This review examines how intrinsic and extrinsic factors may influence the successful transmission of filarial nematodes in tick vectors, drawing insights from extensively studied haematophagous dipteran vector systems. We explore how different tick life stages contribute to potential nematode transmission to the host and the influence of abiotic factors on nematode survival and development within ticks. Understanding nematode life stage periodicity and enhancement phenomena in tick-borne filarial systems is equally important for determining transmission dynamics and co-infection patterns. Also important to nematode transmission are vertebrate host movement and tick feeding patterns, which create opportunities for parasite exchange across ecological environments. Knowledge gaps include the physical and molecular mechanisms of transmission, the potential influence of tick genetic variation on vector competence, immune responses across different tick-filarial associations, and epidemiological studies of host and tick patterns of nematode infection. Comprehensive empirical data are also needed to model transmission patterns, including temperature and humidity thresholds for nematode development and survival, field-based tick infection rates, and how tick immune responses affect these processes. Understanding these factors requires integrating expertise from multiple disciplines and adopting an ecosystem-based perspective that considers the interconnected nature of vertebrate hosts, vectors, and environment in the transmission of filarial nematodes.