In touch with the dead: Disease implications of conspecific carcass visitation and contact

Indirect transmission of diseases in wildlife is complex and poorly understood despite its significance in disease dynamics and predictive modeling. Carcasses of infected hosts can persist on the landscape as infectious sources, as shown in African swine fever (ASF), leading to outbreak persistence and spread. Yet little work has quantified the rate at which carcasses are contacted by conspecifics or the local ecological factors that may impact contact. We used wild pigs (Sus scrofa) to evaluate the probability of conspecific carcass visitation and contact, and to assess how local variables influenced these probabilities. Using camera-traps, we monitored 89 wild pig carcasses across 225.1 km² from March - May 2023 in Texas, U.S.A. Of the 89 carcasses, 63 (70.1%) were visited by conspecifics, and of those, 55 (87.3%) were directly contacted. Visitation was influenced by non-pig scavengers, days post-mortem, and previous wild pig activity at carcasses; while contact was impacted by days post-mortem, maximum temperature, and carcass origin (local vs. foreign). The probability of visitation exhibited a unimodal relationship with days post-mortem, peaking at 0.042 on day 28. In contrast, the probability of contact increased with days post-mortem. As a result, the predicted probability of at least one wild pig contact with a carcass plateaued at 46% on day 47. Foreign carcasses were 7.5 times more likely to be contacted than local carcasses. Our findings show that wild pig carcasses remain epidemiologically relevant for weeks post-mortem, highlighting their potential importance in disease transmission and persistence. Delayed removal and local decontamination of carcasses could be effective strategies to reduce transmission risks.