Naturally acquired antibodies to <i>Bacillus anthracis</i> protective antigen in vultures of southern Africa

Abstract

TURNBULLP, P.C.B. DIEKMANNM,M., KILIAN, J.W., VERSFELDW, W.,DE VOS, V., ARNTZENL, L.,WOLTER, K., BARTELS, P. &amp; KOTZE, A. 2008.N aturally acquired antibodies to Bacillusa nthracisp rotective antigeni n vultureso f southern Africa. Onderstepoort Journal of Veterinary Research, T5:95-102 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 immunosorbenats say( ELISA)f or antibodiesto 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 hole and the other groups (P &lt; 0.001) and no significant difference between the South African and control groups (P &gt; 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 coprotheress, six out of ten Whitebacked Vultures, Gyps africanus, and one out of three Lappet-faced Vultures, Aegypiust racheliotus, 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. lt 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.

The ecology of Bacillus anthracis

“…In Argentina Saggese et al (2007) recovered spores from 1/14 cloacal swab samples from Chimango caracaras (Milvago chimango). In general scavengers are fairly resistant to infection but cases are seen (Edebes, 1976;Hugh-Jones and de Vos, 2002;Kraneveld and Mansjoer, 1941) and antibodies noted, e.g., in lions (Turnbull et al, 1989), and in three species of northern Namibian vultures (Turnbull et al, 2008a).…”

“…If sporulation times are prolonged there is increasing risk of vegetative cell non-survival intervening. For example Turnbull et al (2008a) quotes a water table bath experiment in which he and his colleagues successfully held three B. anthracis strains on agar slants at 12°C but they required up to 2 weeks before sporulating; two other strains failed to sporulate. None grew, sporulated, or survived at 9°C.…”

“…While the oral minimum infective oral dose is largely unknown for wildlife species it was noted (de Vos, 1990;de Vos and Scheepers, 1996) that while 100-250 spores parenterally administered consistently killed kudu in the Kruger National Park, the oral LD 50 with same strain was approximately 15 million spores. In healthy unstressed sheep, horses and cattle the lethal oral dose is of the order of 1.5-5 Â 10 8 spores; parenterally the minimum dose for sheep is 75 spores, killing in 108 h, but only 36 h with 55,000 spores (Turnbull et al, 2008a).…”

“…The reality is that such sites are truly extraordinarily rare, though well documented, and probably merely reflect extremely high initial spore counts. For practical purposes B. anthracis is better perceived as an obligate pathogen with the motto ''sporulate or die" (Turnbull et al, 2008a).…”

Differentiation of Springtime Vegetation Indices Associated with Summer Anthrax Epizootics in West Texas, USA, Deer

“…Anthrax spotters also relied on turkey vultures, Cathartes aura, circling overhead to find additional carcasses. This is an effective method for locating carcasses (Turnbull et al, 2010). Ranch management staff provided total deer population estimates from 1995 to 2010 derived from state-regulated spotlight counts (Jester and Dillard, 2010) and helicopter surveys.…”