How does ecological community influence livestock parasite transmission?

Parasitic and vector-borne diseases (VBDs) are a major cause of poor animal health and reduced ruminant livestock productivity worldwide, threatening food security and sustainable livestock production. Potential impacts range from reduced weight of meat or milk produced per acreage in commercial livestock rearing systems, to the complete loss of small herds on resource-poor subsistence smallholdings.
Parasite abundance and VBD transmission models have been developed that can be used to design and improve veterinary intervention programmes or grazing management to minimise disease risk. However, research and model development has largely focussed on intensively managed ruminant livestock systems, where single species are reared on primarily grass monoculture. Less attention has been given to extensive production systems where the livestock host and parasite species of interest are part of a wider ecological community e.g. communal grazing in the UK, and dryland pastoral systems in Southern Africa. In species-diverse environments such as these, the validity of recommended interventions to reduce parasitic infection is unknown. Furthermore, although wildlife present a conflict for many livestock farmers worldwide, recent studies suggest that co-grazing livestock and wildlife may be beneficial, improving forage quality, reducing tick abundance, and removing gastrointestinal nematode larvae from the environment.

Further research is needed to develop intervention strategies for parasite control that take into account community ecology and the potential epidemiological impact of human-wildlife conflict mitigation strategies.
The student will:
1. Characterise community ecology (including mammalian hosts, parasites and vegetation) in and around the Makgadikgadi Pans National Park (MPNP), Botswana, with the support of the CASE partner, Elephants for Africa (EfA).
EfA's longitudinal spatial datasets of mammal species presence in the MPNP will be supplemented with the student's own observations of parasite diversity in the environment and in samples collected non-invasively from mammalian hosts. Additional host-parasite associations will be extracted from the literature and an open database of ~34,000 host-tick associations6 to construct a novel network model of community structure and seasonal shared habitat use7.

2. Predict the impact of community structure and intervention measures on livestock exposure to parasites and, by extension, parasitic/vector-borne disease risk in livestock.
Global sensitivity analysis performed on the network model will identify candidate keystone host species and habitats and community ecology conditions which limit livestock exposure to parasites. Introducing VBD transmission3 to the network model further allows the expected efficacy of potential intervention measures to be predicted.

3. Validate model output using field observations.
Model output and hypotheses developed will be tested in the field by measuring parasite abundance in the environment and intensity of infection in livestock. Potential field sites with a range of community structures can be found within easy reach of the MPNP. For example, some cattle ranches exclude all other large mammal species, apply intensive parasite control strategies and manage vegetation cover by burning, private game reserves often exclude megaherbivores but allow ruminant livestock and wildlife to co-graze, and a range of degrees of wildlife-livestock sympatry can be observed in rural smallholder villages.
Pilot research suggests that in Botswana wildlife-livestock interactions are common, ruminant parasite burdens are high, and the consequences of parasitism for the food security of subsistence farmers are high. Thus parasitism and community ecology can be readily observed and measured. The student will be able to apply and refine skills developed through their DTP training to develop and test their own hypotheses, whilst also generating o