Emerging infectious diseases
a model of disease transmission dynamics at the wildlife-livestock interface in Uganda
Emerging infectious diseases are a recurring threat to both human and animal health. Understanding the multiple causes behind the emergence of new diseases is key to the prevention of new and potentially devastating outbreaks. The list of underlying causes is long, including a variety of anthropogenic, environmental, molecular and climatic changes that promote the emergence and spread of disease. Two of these factors are central to the emergence of new diseases and receive special attention in this study. The spread of disease from wildlife to livestock and diseases that spread from animals to humans (zoonoses) are of importance as they implicated in the majority of EID events. This study aims to analyse how one emerging infectious disease (ASF) spreads between different wild and domestic hosts, and thereby provide a model for how disease emergence may occur. The field study is located in the northern parts of Uganda, a hotspot new and emerging viral diseases.
The recent spread of African swine fever to parts of Georgia, Russia and most recently to the Ukraine, has put this disease in the spotlight as a new and emerging threat to animal health in all of Europe. African swine fever is a highly contagious viral hemorrhagic disease of pigs, the causal agent of which is a double stranded DNA virus belonging to the family Asfaviridae. The disease is capable of infecting a number of suids, including warthogs (Phacochoerus aethiopicus and Phacochoerus africanus), bushpigs (Potamochoerus larvatus), the giant forest hog (Hylochoerus meinertzhageni), as well as the European wild boar and domestic pigs (both Sus scrofa). Soft ticks (genus Ornithodoros) act as vectors for the disease, spreading it to suid hosts in a sylvatic cycle. 91 blood samples were collected from domestic pigs. Engorged ticks were collected from 6 warthog dens. These were analysed using real-time PCR for the presence of ASFV. All blood samples extracted from ticks were PCR negative for the virus. This study found one domestic pig that was PCR positive for ASFV, but negative for ASFV antibodies when run on an ELISA. This is an interesting find as it suggests the presence of asymptomatic carriers among domestic pigs, a possible source of new outbreaks. Sequencing of the viral DNA and nucleotide Blast analysis found the virus to be 100% identical to genotype IX which has previously been found to circulate in Uganda.