Transmission dynamics of Bartonella in invasive Rattus from South Africa

Abstract

Bartonellosis encompasses a broad range of diseases and clinical symptoms caused by bacteria of the species-rich genus, Bartonella. Three discrete species have been identified in Rattus from South Africa, of which one, B. elizabethae has known zoonotic potential. Brettschneider et al. (2012) developed a model to study the dynamics of Bartonella transmission related to host and ectoparasite vector aspects. However, the model was based on limited data for a number of crucial biological parameters and was unable to fully explain the differential infection rates observed in invasive rats. The present study attempts to obtain empirical estimates for key biological parameters that had to be estimated for that model, based on general rodent data, rather than Rattus-specific data. This was achieved using a molecular approach in which gltA and nuoG gene amplification was used to assess Bartonella prevalence in invasive Rattus, their associated ectoparasites and in, foetuses of Bartonella-positive pregnant female rats. Results revealed a Bartonella genome prevalence of 70.2% in pregnant females and 55.2% in foetuses. Similar Bartonella species were isolated from Rattus mothers and their foetuses, confirming vertical transmission of this bacterium in this rodent genus for the first time. A total of 1400 Rattus-associated ectoparasites (mites, ticks, flies and lice) were collected and identified morphologically. Molecular screening of a subset n=108 of Xenopsylla brasiliensis and X. cheopis fleas and Haemaphysalis elliptica ticks recovered a Bartonella genome prevalence of 84.3% in fleas and 0% in ticks. The corresponding Bartonella prevalence for the Rattus hosts from which the ectoparasites were obtained, was 54.1%. Two rodent-associated Bartonella species with known zoonotic potential were identified in this study, namely B. elizabethae and B. tribocorum. The results of this study can be used to: (i) further refine the epidemiological mathematical model developed by Brettschneider et al (2012), (ii) contribute to the existing body of knowledge on Bartonella infections in Africa, and (iii) assist medical, veterinary, municipal, conservation, and agricultural authorities in formulating suitable management strategies associated with problem rodent pests.