Molecular detection of zoonotic tick-borne pathogens from ticks collected from ruminants in four South African provinces

Ticks are excellent vectors for disease transmission; they are second in importance only to mosquitoes as vectors of human diseases, both infectious and toxic [6]. Apart from being agricultural pests, ticks can also carry pathogens that are transmissible to humans via bites or direct contact with infected animals, causing diseases known as zoonoses [15]. Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato, the causative agents of human granulocytic anaplasmosis (HGA) and Lyme disease (LD), respectively, are common mainly in the U.S. and Europe [8, 22]. Reports of A. phagocytophilum are scarce in Africa, with one published report in Egypt [14]. In South Africa, there is one confirmed case report of the pathogen isolated from whole blood samples of dogs [19]. While information regarding the specific tick vector of B. burgdorferi in South Africa is currently unavailable, it has been suggested that the abundance of tick species in the country would favor establishment of the disease [9]. Previous reports have speculated about the seroprevalence of the bacterium in patients, dogs and horses [10, 40]. Despite reports on these pathogens, their true prevalence has not been properly investigated. Although Coxiella burnetii has been isolated from several arthropods (mainly ticks), the rate of arthropod-borne transmission of Q-fever in people is considered to be low [37]. Q-fever attracts relatively little attention because of the assumed low disease incidence in both humans and animals; however, one of the greater challenges is that it remains asymptomatic [1]. Cattle, sheep and goats are reported as traditional sources of human infection [7]. Although widespread in South Africa, it is far less a cause of disease in humans compared with Rickettsia africae [11]. It has been recently found that several rickettsial species are transmitted in southern Africa, the most common being R. africae [11]. The true reservoir is wide and includes mammals, birds and arthropods, mainly ticks. Cattle, sheep and goats are most commonly identified as sources of human infection, and the disease is prevalent in mostly rural areas worldwide [25], while up to 75% of infected Amblyomma ticks, serve as both reservoirs and vectors [34]. Ehrlichia ruminantium is the causative agent of heartwater disease in cattle, goats and some wild ruminants [4]. It is one of the most important tick-borne pathogens infecting wild and domestic ruminants throughout sub-Saharan Africa [3]. It is generally transmitted by ticks in the genus Amblyomma. In South Africa, the only known vector is A. hebraeum [4], although gene segments have been found, by PCR, in other ticks including Rhipicephalus evertsi evertsi, Hyalomma truncatum and H. marginatum; however, the organism has not been isolated [30]. South Africa is an agro-exporting nation and is mainly dependent on livestock productivity for subsistence according to the Department of Agriculture, Forestry and Fisheries. The country also boasts game reserves, which can be likened to safe havens for ticks, where more often than not, tourists and locals alike fall victim to tick bites and contraction of diseases [13, 35]. Data on the prevalence of these pathogens in ticks would therefore aid in understanding the epidemiology of the diseases they transmit as well as in raising awareness in the veterinary, medical and tourism sectors. In this study, we used PCR to screen for the presence of zoonotic pathogens (A. phagocytophilum, B. burgdorferi, C. burnetii, E. ruminantium and Rickettsia spp.) in ticks collected from various livestock in selected South African provinces.