Abstract
Exposure and immunity to generalist pathogens differ among host species and vary across spatial scales. Anthrax, caused by a multi-host bacterial pathogen, Bacillus anthracis, is enzootic in Kruger National Park (KNP), South Africa and Etosha National Park (ENP), Namibia. These parks share many of the same potential host species, yet the main anthrax host in one (greater kudu (Tragelaphus strepsiceros) in KNP and plains zebra (Equus quagga) in ENP) is only a minor host in the other. We investigated species and spatial patterns in anthrax mortalities, B. anthracis exposure, and the ability to neutralize the anthrax lethal toxin to determine if observed host mortality differences between locations could be attributed to population-level variation in pathogen exposure and/or immune response. Using serum collected from zebra and kudu in high and low incidence areas of each park (18- 20 samples/species/area), we estimated pathogen exposure from anti-protective antigen (PA) antibody response using enzyme-linked immunosorbent assay (ELISA) and lethal toxin neutralization with a toxin neutralization assay (TNA). Serological evidence of pathogen exposure followed mortality patterns within each system (kudus: 95% positive in KNP versus 40% in ENP; zebras: 83% positive in ENP versus 63% in KNP). Animals in the high-incidence area of KNP had higher anti-PA responses than those in the low-incidence area, but there were no significant differences in exposure by area within ENP. Toxin neutralizing ability was higher for host populations with lower exposure prevalence, i.e., higher in ENP kudus and KNP zebras than their conspecifics in the other park. These results indicate that host species differ in their exposure to and adaptive immunity against B. anthracis in the two parks. These patterns may be due to environmental differences such as vegetation, rainfall patterns, landscape or forage availability between these systems and their interplay with host behavior (foraging or other risky behaviors), resulting in differences in exposure frequency and dose, and hence immune response.
Highlights
Disease dynamics may be shaped by the spatial structure of hostpathogen encounter rates, and how the frequency or dose of pathogen exposure affects host susceptibility and immunity to infection [1]
Of the anthrax mortalities observed in Etosha National Park (ENP), the highest number was recorded in the central region (90.4%), followed by 7.4% in the eastern and 2.1% in the western regions
Results of this study suggest that immune responses against multihost pathogens are influenced by several factors, which can be missed from a narrow focus of a single system or species
Summary
Disease dynamics may be shaped by the spatial structure of hostpathogen encounter rates, and how the frequency or dose of pathogen exposure affects host susceptibility and immunity to infection [1]. Anthrax is caused by the grampositive, capsule- and endospore-forming Bacillus anthracis bacterium This pathogen must kill its animal host in a bid to further spread. The resulting endospores can survive in the soil for years until uptake (normally ingestion) by another susceptible host, within which the spores cross the epithelium and can germinate forming vegetative cells. This germination, followed by further propagation and an increase in cells producing toxins [10, 11], leads to the death of the host [12]. The detection of specific antibodies in serum from live animals can, provide information on previous exposure to the pathogen
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
