Waterbird Movements, Parasitology & Epidemiology
Pathogens have a high relevance for conservation, particularly in small protected areas, small or endangered populations, and/or localities in which anthropogenic influences are high. Conservation areas in Africa often occur in close proximity to agricultural systems; and in many countries, areas that have high conservation significance are also used for grazing by cattle, donkeys and goats. Many important pathogens of mammals and birds are carried by ectoparasites (such as ticks, fleas, and tsetse flies).
The community dynamics of most pathogens and parasites are dependent on both their host communities and on their immediate biophysical environment. The close proximity of wild animals, domestic animals and humans in Africa raises many interesting questions from both theoretical and applied perspectives. For example: Does environmental modification (tree felling, heavy grazing, controlled burning, and so forth) affect ectoparasite numbers and hence the prevalence of pathogens in the human population? Do more diverse host communities harbour more diverse pathogen communities, and what would be the implications of such a conclusion for the management of disease in wild populations? Are there thresholds in ectoparasite abundance that dictate the likelihood of disease outbreaks occurring? Are there thresholds in host occurrences that dictate the abundance of ectoparasites? And how would such thresholds be influenced by changes in stocking densities and the species composition of large mammals and birds?
Given the relevance of ectoparasites as vectors of disease, one would expect that many of these questions would have been investigated in detail. In general, however, the spatial dynamics of ectoparasites are poorly understood. There has been relatively little spatially-explicit research on parasites, and few studies have crossed traditional disciplinary boundaries to integrate perspectives from landscape and community ecology, biogeography, veterinary science, and medicine. It is only recently that ecologists have started to develop a food web and community ecology perspective on host-parasite-pathogen relationships, and even more recently that the field of veterinary conservation science has started to gain recognition.
Within this program area, we are using water-associated birds as models from which to understand some of the complex interrelationships between landscape heterogeneity, wetland dynamics, the movements of waterfowl, the bird communities in which our study species occur, and the occurrences of pathogens and parasites.
The Percy FitzPatrick Institute of African Ornithology, in partnership with the Onderstepoort Veterinary Institute and the Wildlife Conservation Society, led the implementation of the southern African component of the USAID-funded GAINS (Global Avian Influenza Network for Surveillance) initiative from 2007-2009. During this time we undertook a regional study of the distributions and movements of ducks and the prevalence of avian influenza viruses in wild duck populations in five sites spread across South Africa (Strandfontein in the Cape, and Barberspan in Northern Province), Mozambique (still under evaluation; potentially Gorongosa and Lake Chuali), Botswana (Makgadikgadi Pans and Lake Ngami), and Zimbabwe (Lake Chivero and Lake Manyame, near Harare). The primary aims of the project were twofold: first, to document the prevalence of influenza viruses (i.e., including but not limited to H5 strains) in wild duck populations in southern Africa; and second, to obtain a better understanding of the regional movement patterns of wild water birds. We sampled and ringed close to 5,000 birds during this period; a list of related publications can be found on Graeme's home page. Although we have ended our influenza sampling efforts for the time being, we are still tracking Egyptian geese using GPS telemetry, collecting data on bird numbers and movements from study sites in coastal plains of Kwazulu-Natal, and working on the fundamentals of the ecology of water-associated birds and their parasties and pathogens.
Building on the GAINS data, which included blood samples from each captured bird, Fitztitute PhD student Sharon Okanga worked on understanding spatial and temporal patterns in avian malaria occurrences in the Western Cape. Dominic Henry is focusing on environmental influences on waterbird movements and foraging behaviours in Kwazulu-Natal; and Chevonne Reynolds has recently started a PhD on understanding how waterfowl may function as mobile links, dispersing propagules between wetlands.
Our influenza work would not have been possible without close collaboration with the ARC-Onderstepoort Verinary Institute and particularly Drs Celia Abolnik (now at the University of Pretoria) and Marco Romito. Our malaria research has likewise been greatly facilitated by the molecular skills of Dr Jeffrey Peters from Wright State University, USA. We also have active collaborations with CIRAD, particularly Drs. Alexandre Caron (Harare) and Nicolas Gaidet (Montpellier).