Distribution and ecology of economically important ticks on cattle, with special reference to the Eastern Cape Province, South Africa and Namibia

[摘要] ENGLISH SUMMARY: Ticks (Acari: Ixodidae) are parasites of major economic and medical importance that transmit a multitude of pathogenic organisms affecting domestic animals globally and in South Africa. High tick infestations are associated with skin damage, tick worry, reduced growth and milk production, transmission of tick-borne pathogens and mortalities. The aims of the study were to: (1) investigate the effect of vegetation type (Albany Coastal Belt, Amathole Montane Grassland, Bhisho Thornveld and Great Fish Thicket) on the tick species composition and diversity on cattle and on the vegetation on communal farms in the south-west region of the Eastern Cape Province (ECP), (2) obtain baseline data on the perceptions of cattle farmers with regard to ticks, tick-borne diseases (TBDs) and the management practices being used on communal farms in the ECP and (3) record the geographic distribution of an alien invasive tick, Rhipicephalus microplus and the closely related endemic species Rhipicephalus decolaratus in the environmentally less optimal south-western and north-western regions of South Africa and in Namibia. The study was conducted at two scales: local (ECP) and regional (South Africa and Namibia). At a local scale, ticks were collected from cattle (adult and calves) and from the vegetation from five localities in each of four vegetation types. Ticks were removed from one-side of each animal (n = 1000) and replicated drag-sampling was performed at each locality, to record the ticks on vegetation. In addition, at each locality five cattle owners were randomly selected to participate in a questionnaire study. Face-to face interviews were carried. A total of 100 individual questionnaires were completed (25 in each of the four vegetation types). At a regional scale, ticks were collected through active tick removal from cattle and by passive citizen-science approach where tick samples were provided by private cattle farmers solicited via social media. Cattle (n = 415) were examined in the Western-, Eastern- and Northern Cape and Free State Province in South Africa and in Namibia (n = 18). About 20 212 ticks belonging to 12 species were collected from adult cattle, calves and on vegetation at the 20 communal localities. Vegetation type did not consistently affect tick abundance, species richness or species composition, though there were differences in the abundance of individual tick species. The abundance of R. e. evertsi was significantly higher on cattle in Thornveld and Thicket compared to Coastal belt and Grassland, while A. hebreaum was significantly more abundant on the vegetation in Coastal belt compared to Thornveld and absent in Grassland. The effect of individual villages on tick infestations was more important than vegetation types. Tick abundance and species richness was higher on adult cattle compared to calves. In terms of farmer perceptions, significantly more respondents confirmed that adult animals were more affected by ticks compared to calves. All of the respondents identified redwater as the commonest TBDs, followed by gallsickness (90%) and heartwater (43%). For the geographic distribution of R. microplus, a total of 8 408 Rhipicephalus (Boophilus) spp. ticks were recovered from cattle in SA. R. microplus extended its range to new areas for the first time in the Northern Cape Province and the western regions of the Eastern- and Western Cape Provinces. In Namibia, R. microplus was recorded for the first time with 142 adult R. microplus collected from 20 cattle on four farms, whereas R. decoloratus was present on all 18 of the survey farms in Namibia. Evident from the study is that the concern of communal cattle farmers in the ECP about ticks and TBDs is supported with field-based studies. The patterns of tick infestation observed in the present study seems to be the result of a combination of factors that include amongst others the uncontrolled movement of cattle within SA and between SA and Namibia, the development of acariside resistance and the highly adaptable nature of the invasive Asiatic tick.

[发布机构] Stellenbosch University