Occurrence of tick-borne haemoparasites in selected South African wild rodent species in the Mnisi Communal area

Abstract

In 2013, a disease survey of people in the Mnisi community, Bushbuckridge, Mpumalanga, South Africa revealed a surprisingly high level of exposure to tick bite fever, Bartonella, Q fever and leptospirosis. This indicated the need to educate the community about ectoparasites, exposure to rodents and general hygiene. In addition, the potential contribution of rodent pathogen transmission to human febrile illnesses is considered a public health concern and warrants further investigation. Most human tick-borne diseases are considered emerging diseases because the number of reported cases annually is increasing. This is probably due to ecological changes, increased awareness and an increased number of susceptible individuals in the global population. Conservation efforts have increased numbers and ranges of host animals which maintain the infected tick population and humans are increasingly encroaching into tick dense areas. Thus, humans are more exposed to tick-borne infectious diseases. Increased awareness by doctors and the public has also contributed to the increased reporting of human tick-borne disease. With major medical advancements, there is an increased proportion of the population that is more susceptible to these infectious diseases. Vector-borne parasitic zoonoses are an important aspect of a constantly changing world because they are also constantly adapting to their new circumstances. Infectious organisms can change virulence, hosts and vectors. These diseases are, therefore, very much a part of the future. With new advances in molecular biology, detection of infectious diseases is constantly improving. The economic impact and losses due to vector-borne diseases are wide and felt at both the human health and animal health levels. Losses occur due to the cost of human illness, deaths, reduced animal production and costs to control or prevent disease. In developing countries where animals are relied on for work, transportation and nutrition, the losses are more profound. The order Rodentia is the most abundant and diversified order. Rodents are distributed all over the world except for Antarctica. They often live in close contact with humans, their farm animals and their pets. Rodents pose a threat to humans in several ways. Not only do they act as reservoirs for infectious diseases and serve as hosts for vectors, they also compete globally with us for food, causing serious pre-harvest damage to cereals every year. Examples of rodent-borne human illnesses include rickettsiosis, babesiosis, human granulocytic anaplasmosis, leptospirosis, bartonellosis, tick-borne relapsing fever, Lyme disease and Q fever. More information about these diseases and their impact on public health in an African context is needed. This mini dissertation is divided into two parts. The first is a narrative literature review on what is known about the common rodent-borne bacterial and parasitic pathogens which have an important impact on public health and their relevance in Africa. The current knowledge is described and recommendations for further research are given. The second part is a laboratory project which focused on determining the incidence of selected tickborne pathogens found in wild rodent species in the Mnisi community, a livestock-wildlifehuman interface area in South Africa. Forty wild rodent blood samples underwent a broadbased screening approach using reverse line blot (RLB) hybridization and a more specific approach using quantitative real-time PCR (qPCR) techniques.