Publications (3)3.98 Total impact
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Article: The ecology of influenza A viruses in wild birds in southern Africa.
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ABSTRACT: Avian influenza viruses (AIVs) are pathogens of global concern, but there has been little previous research on avian influenza in southern Africa and almost nothing is known about the dynamics of AIVs in the region. We counted, captured and sampled birds regularly at five sites, two in South Africa (Barberspan and Strandfontein) and one in each of Botswana (Lake Ngami), Mozambique (Lake Chuali) and Zimbabwe (Lakes Manyame and Chivero) between March 2007 and May 2009. The South African and Zimbabwean sites were visited every 2 months and the sites in Botswana and Mozambique every 4 months. During each visit we undertook 5-7 days of standardised bird counts followed by 5-10 days of capturing and sampling water-associated birds. We sampled 4,977 birds of 165 different species and completed 2,503 half-hour point counts. We found 125 positive rRT-PCR cases of avian influenza across all sites. Two viruses (H1N8 and H3N8) were isolated and additional H5, H6 and H7 strains were identified. We did not positively identify any highly pathogenic H5N1. Overall viral prevalence (2.51%) was similar to the lower range of European values, considerable spatial and temporal variation occurred in viral prevalence, and there was no detectable influence of the annual influx of Palearctic migrants. Although waterbirds appear to be the primary viral carriers, passerines may link wild birds and poultry. While influenza cycles are probably driven by the bird movements that result from rainfall patterns, the epidemiology of avian influenza in wild birds in the subregion is complex and there appears to be the possibility for viral transmission throughout the year.EcoHealth 04/2011; 8(1):4-13. · 1.70 Impact Factor -
Article: Phenotypic flexibility of a southern African duck Alopochen aegyptiaca during moult: do northern hemisphere paradigms apply?
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ABSTRACT: Phenotypic flexibility during moult has never been explored in austral nomadic ducks. We investigated whether the body condition, organ (pectoral muscle, gizzard, liver and heart) mass and flight-feather growth Egyptian geese Alopochen aegyptiaca in southern Africa show phenotypic flexibility over their 53-day period of flightless moult. Changes in body mass and condition were examined in Egyptian geese caught at Barberspan and Strandfontein in South Africa. Mean daily change in primary feather length was calculated for moulting geese and birds were dissected for pectoral muscle and internal organ assessment. Mean body mass and condition varied significantly during moult. Body mass and condition started to decrease soon after flight feathers were dropped and continued to do so until the new feathers were at least two-thirds grown, after which birds started to regain body mass and condition. Non-moulting geese had large pectoral muscles, accounting for at least 26% of total body mass. Once moult started, pectoral muscle mass decreased and continued to do so until the flight feathers were at least one-third grown, after which pectoral muscle mass started to increase. The regeneration of pectoral muscles during moult started before birds started to gain overall body mass. Gizzard mass started to increase soon after the onset of moult, reaching a maximum when the flight feathers were two-thirds grown, after which gizzard mass again decreased. Liver mass increased significantly as moult progressed, but heart mass remained constant throughout moult. Flight feather growth was initially rapid, but slowed towards the completion of moult. Our results show that Egyptian geese exhibit a significant level of phenotypic flexibility when they moult. We interpret the phenotypic changes that we observed as an adaptive strategy to minimize the duration of the flightless period. Moulting Egyptian geese in South Africa undergo more substantial phenotypic changes than those reported for ducks in the northern hemisphere.Journal of Avian Biology 08/2010; 41(5):558 - 564. · 2.28 Impact Factor -
Article: Wild Bird Movements and Avian Influenza Risk Mapping in Southern Africa
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ABSTRACT: "Global analyses of the potential for avian influenza transmission by wild birds have ignored key characteristics of the southern African avifauna. Although southern Africa hosts a variety of migratory, Holarctic-breeding wading birds and shorebirds, the documented prevalence of avian influenza in these species is low. The primary natural carriers of influenza viruses in the northern hemisphere are the anatids, i.e., ducks. In contrast to Palearctic-breeding species, most southern African anatids do not undertake predictable annual migrations and do not follow migratory flyways. Here we present a simple, spatially explicit risk analysis for avian influenza transmission by wild ducks in southern Africa. We developed a risk value for each of 16 southern African anatid species and summed risk estimates at a quarter-degree cell resolution for the entire subregion using data from the Southern African Bird Atlas. We then quantified environmental risks for South Africa at the same resolution. Combining these two risk values produced a simple risk map for avian influenza in South Africa, based on the best currently available data. The areas with the highest risk values were those near the two largest cities, Johannesburg and Cape Town, although parts of Kwazulu-Natal and the Eastern Cape also had high-risk scores. Our approach is simple, but has the virtue that it could be readily applied in other relatively low-data areas in which similar assessments are needed; and it provides a first quantitative assessment for decision makers in the subregion."
