A comparison of manual and carbon dioxide trap sampling of Ornithodoros soft ticks from warthog resting sites in South Africa

Background: In East and Southern Africa, the African swine fever (ASF) virus is maintained in an ancient sylvatic cycle involving warthogs (Phacochoerus spp.) and Ornithodoros soft ticks inhabiting warthog burrows. Although carbon dioxide (CO2) traps have previously been used to collect ticks from pigsties in Portugal, this method has never been tested in the context of the ASF sylvatic cycle in Africa. As warthogs adapt their resting site preferences in response to different levels of habitat transformation, our study aimed to evaluate the effectiveness of CO 2 traps versus traditional manual collection of soft ticks inhabiting two warthog resting sites: warthog burrows (natural) and house decks (anthropogenic). Methods: The study was performed in Mjejane Game Reserve, a wildlife conservancy adjacent to the Kruger National Park in South Africa. Sixty-one warthog resting sites (31 natural burrows and 30 house decks) were sampled to compare Ornithodoros tick numbers using manual and CO2 trap methods during wet (summer) and dry (winter) seasons. Results: The number of ticks collected with CO2 traps (n = 2024) was significantly higher than those collected with the manual method (n = 885, P < 0.001) for both resting site types. Moreover, the number of ticks collected using CO2 traps from house decks (n = 1399) was significantly higher (P < 0.001) compared to burrows (n = 625). There were no differences in the number of ticks collected between seasons. Our results suggest that CO2 traps are highly efficient for collecting Ornithodoros ticks from the two warthog resting site types evaluated in our study area. They also confirm that warthogs can adapt to different levels of habitat transformation and human presence. Conclusions: The standardised use of the CO2 trap method facilitates investigations on the distribution of tick-related ASF cycles in sub-Saharan Africa and improves our understanding of the eco-epidemiology of ASF and other Ornithodoros tick-borne diseases.