Role of potential reservoir hosts and flea vectors in plague epidemiology in eastern Zambia

PhD ThesisThis thesis is prepared according to “Published manuscripts” format of the Sokoine University of Agriculture. This thesis discusses the role of potential plague reservoirs and their flea-vectors in the plague epidemiology in eastern Zambia. The goal was to identify and describe roles domestic pigs, goats and sheep, and rodents with their fleas play in maintaining and transmitting the plague pathogen, Yersinia pestis. Plasminogen activator gene (pla) of Y. pestis was successfully identified in fleas and rodents, and Immunoglobulin G (IgG) antibodies against Fraction 1 antigen (Fra1)of Y. pestis, were detected in serum samples from the domestic animals using conventional Polymerase Chain reaction (c-PCR) and indirect Enzyme-linked Immunosorbent Assay (i-ELISA), respectively. Quantitative and qualitative approaches were applied using open and close ended questionnaires by individual respondents and focus group discussion (FGD) to obtain data on human and animal activities in relation to plague disease. The findings indicate that hunting, transportation and preparation or handling of infected animals or their materials predispose humans to plague pathogens and risk of acquiring the disease. The dissertation comprised five publications. The first paper published in the Journal of Medical Entomology, presents the roles domestic pigs, small ruminants, rodents and their fleas, play in the epidemiology of plague in Sinda district in eastern Zambia. This presents the first published literature on plague in pigs and small ruminants and demonstrated the naturally occurring IgG antibodies against Fra1 antigen. The second paper, published in Tropical Doctor presents the findings in Nyimba district after a suspected plague outbreak, where pla gene and IgG antibodies were detected in fleas, and pigs, goats and rodents respectively. The third paper published in the Journal of Zoonotic diseases is a review paper which identified factors that precipitated the spread of plague between 1914 and 2014 in Zambia. The fourth paper published in the American Journal of Tropical Medicine and Hygiene and identified risk factors associated with plague epidemiology. The fifth paper has been submitted to BMC Microbiology Journal, revealed that pla gene of Y. pestis circulating among different hosts in the two districts were closely related to Antiqua (1.ANT) biovar.INTRA-ACP mobility schem