A serological survey of Bacillus anthracis reveals widespread exposure
to the pathogen in free-range and captive lions in Zimbabwe.
Abstract
Numerous unknown factors influence anthrax epidemiology in multi-host
systems, especially at wildlife/livestock/human interfaces. Serology
tests for anti-anthrax antibodies in carnivores are useful tools in
identifying the presence or absence of Bacillus anthracis in a range.
These were employed to ascertain if the disease pattern followed the
recognized high and low risk anthrax zonation in Zimbabwe and also to
establish if anthrax was absent from Hwange National Park in which there
has been no reported outbreaks. African lions (Panthera leo) (n= 114)
drawn from -free-range protected areas and captive game parks located in
recognized high and low risk zones across Zimbabwe were tested for
antibodies to anthrax PA antigen using the ELISA immunoassay. A random
selection of 27 lion sera samples comprising 17 sero-positive and 10
sero-negative sera were further tested in the species-independent toxin
neutralization assay (TNA) in order to validate the former as a
surveillance tool for anthrax in African lions. Using the ELISA-PA
immunoassay, 21.9% (25/114) of the lions tested positive for antibodies
to anthrax. Seropositivity was recorded in all study areas and there was
no significant difference (p= 0.852) in seropositivity between lions in
high and low risk anthrax zones. Also, there was no significant
difference (McNemar’s χ2 = 0.9, p = 0.343) in the proportion of lions
testing positive to anti-PA anthrax antibodies on ELISA-PA immunoassay
compared to the TNA, with fair agreement between the two tests [Kappa
(K) statistic = 0.30; 0.08