ORIGINAL RESEARCH

 

Naturally acquired antibodies to Bacillus anthracis protective antigen in vultures of southern Africa

 

 

P.C.B. Turnbull^I; M. Diekmann^II; J.W. Kilian^III; W. Versfeld^III; V. De Vos^IV; L. Arntzen^V; K. Wolter^VI; P. Bartels^VII; A. Kotze^VII

^IArjemptur Technology Ltd, Bldg 227, Science Park, Down, SP4 0JQ, United Kingdom
^IIRare and Endangered Species Trust, Otjiwarongo, Namibia
^IIIEtosha Ecological Institute, Okaukuejo, Namibia
^IVP.O. Box 14724, Nelspruit, South Africa
^VNational Institute for Communicable Diseases, Private Bag X4, Sandringham, 2131 South Africa
^VIVulture Programme, Rhino and Lion Wildlife Conservation NPO, Nyoka Ridge, Magaliesburg, South Africa
^VIINational Zoological Gardens of SA, Pretoria, South Africa
^VIIIUniversity of the Free State, Bloemfontein, South Africa

 

 

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ABSTRACT

Sera from 19 wild caught vultures in northern Namibia and 15 (12 wild caught and three captive bred but with minimal histories) in North West Province, South Africa, were examined by an enzyme-linked immunosorbent assay (ELISA) for antibodies to the Bacillus anthracis toxin protective antigen (PA). As assessed from the baseline established with a control group of ten captive reared vultures with well-documented histories, elevated titres were found in 12 of the 19 (63 %) wild caught Namibian birds as compared with none of the 15 South African ones. There was a highly significant difference between the Namibian group as a whole and the other groups (P < 0.001) and no significant difference between the South African and control groups (P > 0.05). Numbers in the Namibian group were too small to determine any significances in species-, sex- or age-related differences within the raw data showing elevated titres in four out of six Cape Vultures, Gyps coprotheres, six out of ten White-backed Vultures, Gyps africanus, and one out of three Lappet-faced Vultures, Aegypius tracheliotus, or in five of six males versus three of seven females, and ten of 15 adults versus one of four juveniles. The results are in line with the available data on the incidence of anthrax in northern Namibia and South Africa and the likely contact of the vultures tested with anthrax carcasses. It is not known whether elevated titre indicates infection per se in vultures or absorption of incompletely digested epitopes of the toxin or both. The results are discussed in relation to distances travelled by vultures as determined by new tracking techniques, how serology can reveal anthrax activity in an area and the issue of the role of vultures in transmission of anthrax.

Keywords: Antibodies, anthrax, Bacillus anthracis, serology, vultures

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Accepted for publication date 2008-Editor

 

 

* Author to whom correspondence is to be directed. E-mail: peterturnbull@tesco.net