Ticks (Acari : Ixodidae) associated with wild herbivorous mammals in South Africa

Abstract

The Republic of South Africa is rich in the species of large and small wild herbivores and ixodid ticks that infest them and the domestic livestock within its borders. The primary objective of this study was to determine the species composition and actual size of the tick burdens of a variety of small and large herbivorous animals in several localities in South Africa. To this end a total of 95 wild herbivores ranging in size from hares to giraffes and belonging to 25 species were examined at 20 various localities in South Africa. The survey localities in alphabetical sequence were the Addo Elephant National Park, “Bucklands” farm, the Eastern Shores Nature Reserve, the Hluhluwe Nature Reserve, the Karoo National Park, the Kgalagadi Transfrontier Park, a farm at Kirkwood, eight localities within the Kruger National Park, the Mountain Zebra National Park, the Tembe Elephant Reserve, the Thomas Baines Nature Reserve, the Umfolozi Nature Reserve, and the West Coast National Park. Sampling took place between 1982 and 1996. The animal species surveyed were giraffe, Giraffa camelopardalis; African buffalo, Syncerus caffer; eland Taurotragus oryx; Burchell’s zebra, Equus burchelli; black wildbeest, Connochaetes gnou; blue wildbeest, Connochaetes taurinus; tsessebe, Damaliscus lunatus; Lichtenstein’s hartebeest, Sigmoceros lichtensteinii; bontebok, Damalisus pygargus dorcas; red hartebeest, Alcelaphus buselaphus; nyala, Tragelaphus angasii; bushbuck, Tragelaphus scriptus; greater kudu, Tragelaphus strepsiceros; gemsbok, Oryx gazella; springbok, Antidorcas marsupialis; grey rhebok, Pelea capreolus; mountain reedbuck, Redunca fulvorufula; boer goats, Capra hircus; a domestic calf, Bos sp.; suni, Neotragus moschatus; steenbok, Raphicerus campestris; rock hyrax, Procavia capensis; cape ground squirrels, Xerus inauris; scrub hares, Lepus saxatilis; and Smith’s red rock rabbits, Pronolagus rupestris. Ticks were collected from the survey animals after they had been killed by a process of soaking in a tick-detaching agent followed by scrubbing and sieving, or by careful scrutiny after the animals had been chemically immobilized. Thirty ixodid tick species, namely Amblyomma hebraeum, Amblyomma marmoreum, Rhipicephalus (Boophilus) decoloratus, Haemaphysalis parmata, Haemaphysalis silacea, Hyalomma glabrum, Hyalomma marginatum rufipes, Hyalomma truncatum, Ixodes rubicundus, Ixodes pilosus group, Margaropus winthemi, Rhipicephalus appendiculatus, Rhipicephalus arnoldi, Rhipicephalus capensis, Rhipicephalus distinctus, Rhipicephalus evertsi evertsi, Rhipicephalus exophthalmos, Rhipicephalus follis, Rhipicephalus glabroscutatum, Rhipicephalus gertrudae, Rhipicephalus kochi, Rhipicephalus maculatus, Rhipicephalus muehlensi, Rhipicephalus neumanni, Rhipicephalus sp. near pravus, Rhipicephalus theileri, Rhipicephalus simus, Rhipicephalus zambeziensis, and an unidentified Ixodes and Rhipicephalus species were recovered from the animals. All the tick species recovered in this study have been tabulated according to their distributions within the climatic zone of the Republic of South Africa. A total of 64 of the abovementioned herbivores ranging in size from medium to very large, belonging to 15 various species were examined in 11 national parks, or nature reserves or farms during 1982 - 1996. The tick species infesting the medium and small-sized animals were to some extent similar to those of very large animals. The medium-sized survey animals mostly harboured A. hebraeum, R. (B.) decoloratus, R. appendiculatus, R. evertsi evertsi and R. glabroscutatum whereas the tick burdens of the very large antelopes consisted mostly of A. hebraeum, R. (B.) decoloratus, R. appendiculatus, R. maculatus and R. muehlensi. The very large hosts harboured proportionately more adult ticks than the smaller animals which harboured proportionately more immature ticks. An interesting finding was the recovery of Rhipicephalus sp. near R. pravus from giraffes in the north-eastern Mpumalanga province and these very closely resembled the true R. pravus which occurs in East Africa. A further objective of this study was to make an inventory of the ixodid tick species infesting wild animals in three of the western, semi-arid nature reserves in South Africa. To this end the tick burdens of a total of 45 animals in the Karoo National Park, the Kgalagadi Transfrontier Park and the West Coast National Park were determined. Fourteen ixodid tick species were recovered, of which H. truncatum, R. exophthalmos and R. glabroscutatum were commonly present in two reserves and the remaining species each only in one reserve. H. truncatum, R. capensis and R. glabroscutatum were the most numerous of the ticks recovered, and eland were the most heavily infested with the former two species and gemsbok and mountain reedbuck with R. glabroscutatum. Nine very small antelopes, six of which were steenbok and three were sunis and to my knowledge whose total tick burdens had never before been determined were also examined. The steenbok were examined in three nature reserves and harboured nine tick species and the sunis were examined in a fourth reserve and were infested with eight tick species. The steenbok and sunis were generally infested with the immature stages of the same tick species that infest larger animals in the same geographic regions. In addition the sunis harboured H. parmata, which in South Africa is present only in the eastern and north-eastern coastal and adjacent areas of KwaZulu-Natal Province. They were also infested with R. kochi, which in South Africa occurs only in the far north-east of the KwaZulu-Natal and Limpopo Provinces. A further objective of the study was to assess the host status of African buffaloes for the one-host tick R. (B.) decoloratus. To this end the R. (B.) decoloratus burdens of ten buffaloes examined in three north-eastern KwaZulu-Natal Province (KZN) nature reserves were compared with those of medium-sized to large antelope species in these reserves and in the southern Kruger National Park (KNP), Mpumalanga Province. The R. (B.) decoloratus burdens of the buffaloes were considerably smaller than those of the antelopes in the KNP, but not those in the KZN reserves. The life-stage structure of the R. (B.) decoloratus populations on the buffaloes, in which larvae predominated, was closer to that of this tick on blue wildebeest, a tick-resistant animal, than to that on other antelopes. A single buffalo examined in the KNP was not infested with R. (B.) decoloratus, whereas a giraffe, examined at the same locality and time, harboured a small number of ticks. In a nature reserve in Mpumalanga Province adjacent to the KNP, two immobilized buffaloes, from which only adult ticks were collected, were not infested with R. (B.) decoloratus, whereas greater kudus, examined during the same time of year in the KNP harboured large numbers of adult ticks of this species. African buffaloes would thus appear to be resistant to infestation with R. (B.) decoloratus, and this resistance is expressed as the prevention of the majority of tick larvae from developing to nymphs.