Spatial Parasitology and Epidemiology

Coordinator

Prof. Graeme Cumming

Overview

Pathogens have a high relevance for conservation, particularly in small protected areas, small or endangered populations, 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 working on understanding some of the complex interrelationships between landscape heterogeneity, wetland dynamics, the movements of water birds, 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 WCS, led the implementation of the southern African component of the USAID-funded GAINS 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. Although we have ended our sampling efforts for the time being, individuals of two species (Red-Billed Teal and Egyptian Geese) are still being tracked using GPS telemetry; and we are still collecting some core data on bird numbers at Barberspan and Strandfontein.

We are now shifting into analytical mode, with our remaining samples being analysed and a mound of data to work through. The results of the study will contribute to a regional and global understanding of the potential role of wild birds in the epidemiology of avian influenzas, as well as shedding light on patterns of duck movements through the year and the causes of nomadism in duck populations in semi-arid areas. Building on our GAINS data, which included blood samples from each captured bird, Fitztitute PhD student Sharon Okanga and postdoc Felix Nchu are starting to work on understanding spatial and temporal patterns in avian malaria occurrences in the Western Cape. Click here for more information about SA-GAINS.

Moult and Movement Ecology of Southern African Waterfowl, with a particular emphasis on Egyptian Geese

Research Team: Mduduzi Ndlovu, Graeme Cumming & Phil Hockey

Although there is extensive literature about the biology of many Anatidae, little is known about the body condition dynamics, dispersal distances, movement patterns and moult biology of the Egyptian Goose. The Egyptian Goose is one of the most abundant and wide-spread Anatidae in southern Africa (Hockey et al. 2005), with a wide habitat tolerance and an increasing population (Mangnall & Crowe 2002).

Research in the northern hemisphere suggests that wild birds that frequently associate with other species, like the Egyptian Geese, may be likely vectors of avian influenza (FAO 2005). Currently the Egyptian Goose is being implicated in the spread of low-pathogenic avian influenza virus in the Western Cape between the ostrich farms and the wild duck populations (Sinclair et al 2006). The movements of wild ducks in South Africa are not well understood and ornithological programmes like SAFRING are currently unable to reveal the detailed movement patterns of nomadic duck species (Thomas 2007). Therefore, fine-resolution research centred on understanding the movements of Egyptian Geese as they relate to environmental variation will also contribute to the modelling of regional avian influenza transmission dynamics.

The lack of synchrony in life history stages among Egyptian Geese across the region makes it difficult to understand their responses to environmental variation (Geldenhuys 1975; Dean 1978; Colahan 1984; Hockey et al. 2005). Is the lack of synchrony a survival strategy, or a direct response to variations in the local environment? This research will attempt to unite behaviour, ecology, moult biology and movement into a broad-scale assessment of the responses of Egyptian Geese to environmental variation.

SAFRING data indicate that the dispersal distances travelled by Egyptian Goose range from just a few kilometres to over 1000 km in less than a year. Little is known as to which proportions of the population undertake short-and long-distance dispersal, and whether or not dispersal relates to any physical environmental variation.

The objectives of this study are as follows:

• To investigate how body condition, moult and population abundance of Egyptian Geese are related to annual environmental variations in photoperiod, rainfall and temperature;

• Using telemetry and colour rings, to determine the movement patterns and dispersal distances of Egyptian Geese banded at the study sites.

For more information on the research project and how you can help, click here.

Ecological processes regulating the distribution of vector-borne blood parasites of waterbirds inhabiting natural and artificial wetlands in the Western Cape Province of South Africa.

Research Team: Felix Nchu, Graeme Cumming, Phil Hockey

This research will help us understand the role of human induced environmental factors on the distribution and abundance of avian blood parasites. Funding for this research is provided by DST/NRF Centre of Excellence at the Percy FitzPatrick Institute.

The influences of host community, urbanization and water quality on avian malaria ecology in South African passerines

Research Team: Sharon Okanga, Graeme Cumming, Phil Hockey

The study aims to investigate the incidence, prevalence of avian malaria and the factors driving avian malaria infection patterns in one or more common passerines in relation to factors pertinent to land cover change, aridity and host community composition. Birds act as one of the predominant hosts for zoonoses. Their high mobility enables them to transfer diseases over a large range and between a wide diversity of hosts. It is hoped that increasing contributions to the knowledge of avian disease ecology in Africa, and mechanisms driving transmission, will help with educational and conservation efforts ongoing within the country and continent wide. This research is funded through the Centre of Excellence.