Parasites of Rattus norvegicus trapped in Durban, eThekwini Municipality, South Africa.

Abstract

have acquired as they spread across the globe. This work narrows the gap in our knowledge of endoparasites carried by Rattus norvegicus in the port city of Durban, South Africa. The study was conducted over a one year period to include the wet and dry seasons, and rodents were trapped at 56 sites across four locations: central business district (CBD), harbour (HBR), informal settlements (IS) and urban/peri-urban (UPU) areas. The city’s Vector Control Division conducted the trapping using custom-made live traps. Three hundred and seventy nine R. norvegicus were caught, plus by-catches of 10 R. rattus and 11 Mastomys natalensis. Rodents were humanely euthanased, blood samples drawn, all ectoparasites collected for a parallel study, various body measurements and mass recorded, then they were dissected, their organs removed and faeces collected. Organs were individually processed, parasites removed and preserved in 70% ethanol prior to identification. Faeces were collected in 10% formal saline for parasite egg and cyst identification. Parasites of public health importance recovered from R. norvegicus were: Trypanosoma lewisi (22.8%) from blood; Moniliformis moniliformis (9.5%), Hymenolepis diminuta (17.2%), H. nana (0.8%) and Gongylonema sp. (25.3%) from the small intestine; Calodium hepaticum (2.6%) from the liver and Angiostrongylus cantonensis (15.3%) from the heart and lungs. Serological testing for Toxoplasma gondii yielded a prevalence of 11.2%. Parasite ova mechanically transmitted in the rodents’ faeces, and a potential infection risk for humans, were Ascaris sp. (4.8%), Taenia sp. (0.3%), Schistosoma mansoni (0.3%), Calodium hepaticum (0.8%), Ascaridia galli (0.5%) and Toxocara sp. (0.3%). Xenopsylla cheopis, Polyplax spinulosa, Laelaps lamborni and L. echidnina were investigated as drivers of T. lewisi infection. Rats infected with T. lewisi and X. cheopis were more prevalent at CBD and HBR, and juveniles were most frequently affected. Trypanosome infections were positively associated with fleas, negatively associated with lice, and not associated with mites. Extrinsic and intrinsic interactions between helminths of the gut were examined and location and rat age were found to be the most significant drivers. The helminths were: Gongylonema neoplasticum, Protospirura muricola, Moniliformis moniliformis, Hymenolepis diminuta, H. nana, Nippostrongylus brasiliensis, Strongyloides spp., Heterakis spumosa, and Syphacia muris. Taenia taeniaformis was most prevalent and abundant at IS, in males, and in rats as they aged. Trichosomoides crassicauda was most prevalent and abundant at CBD, HBR and UPU, in males and in rats as they aged (no pups were infected). Common gut protozoans were identified and reported, as were the eggs voided by rats unrelated to their helminth infections. The city centre offers harbourage and abundant food for rats, and suitable habitats for the successful breeding of arthropod vectors of some of these parasites, making it an area of high transmission and a potential public health risk.