Abstract:

Rift Valley fever virus (RVF) is an emerging zoonotic disease that cycles between wildlife, livestock, and people in Africa, causing significant loss. It is spread primarily by mosquitoes and emergence in Europe and North America is a risk. Current literature has focused on correlating large epidemics of RVF with weather events. However, little attention has been given to the underlying mechanisms driving epidemics and persistence, such as transmission from mosquitoes to wildlife. It is unclear how RVF virus persists during the inter-epidemic periods, but there are two potential nonexclusive explanations for RVF virus persistence: 1) RVF is maintained in the mosquito population via vertical transmission, or 2) RVF circulates undetected in some wildlife reservoir population. We designed and analyzed a mathematical model for the dynamics of RVF to address the role of free-living African buffalo in Kruger National Park in the persistence of RVF. We found that a combination of vertical transmission and circulation in an alternate reservoir is the most likely explanation of persistence of RVF in Kruger. Bovine tuberculosis (BTB) is an invasive bacterial disease also recently infecting African buffalo. We extend the RVF model to examine immune-mediated interactions between chronic BTB and RVF outbreaks on a population level. We hypothesize that BTB can facilitate infection with RVF in buffalo, resulting in larger outbreaks. We also highlight the mathematical challenges posed by the study.