Collection of free-living nymphs and adults of Amblyomma hebraeum (Acari: Ixodidae) with pheromone/carbon dioxide traps at 5 different ecological sites in heartwater endemic regions of South Africa

Tick Diversity and Distribution of Hard (Ixodidae) Cattle Ticks in South Africa

Ticks are amongst the important ectoparasites where livestock are concerned, as they adversely affect the animals through bloodsucking. In tropical and subtropical countries, they transmit pathogens such as babesiosis, theileriosis, ehrlichiosis, and anaplasmosis in cattle, causing a reduction in production rate and significant concomitant economic losses. Ticks affect 80% of the cattle population across the world, with an estimated economic loss of USD 20–30 billion per year. In South Africa, economic losses in the livestock industry caused by ticks and tick-borne diseases are estimated to exceed USD 33 million per year (ZAR 500 million). There are seven major genera of ixodid ticks in Southern Africa (i.e., Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus). The environment in which a tick lives is made up of all the various biological and abiotic factors that are either necessary or unnecessary for its life. The areas where various ticks have been found have been documented in many publications. Using these data, maps of possible species’ habitats can be made. Historical records on tick distribution may be incorrect due to identification mistakes or a change in the tick’s name. All the sources used to generate the maps for this review were unpublished and came from a wide range of sources. To identify tick species and the accompanying microbial ecosystems, researchers are increasingly adopting tick identification methods including 16S and 18S rDNA gene sequencing. Indeed, little is known about the genetic alterations that give important traits, including the predilection for tick hosts, transmission, and acaricide resistance. Opportunities for exploring these changes in tick populations and subpopulations are provided by advancements in omics technologies. The literature on the variety of ixodid ticks, their direct and indirect effects, and control methods in South Africa is compiled in this review.

Genetic diversity of Rickettsia africae isolates from Amblyomma hebraeum and blood from cattle in the Eastern Cape province of South Africa

Rickettsia africae is a re-emerging tick-borne pathogen causing African tick bite fever (ATBF) in humans. Amblyomma variegatum is the principal vector in most sub-Sahara African countries, whereas in South Africa it is A. hebraeum. Reports of high genetic heterogeneity among R. africae isolates in southern Africa have prompted the need for molecular investigations of isolates form South Africa. Therefore, this study aimed to determine the prevalence and genetic diversity of R. africae in A. hebraeum collected from cattle, grazing pasture, as well as from blood of cattle in the Eastern Cape Province of South Africa. Amblyomma hebraeum and blood from cattle were screened by PCR and the gltA, ompA, ompB, sca4, and 17kDa genes were sequenced for R. africae from samples collected from Caquba in Port St. Johns along the coastal region in the Eastern Cape province of South Africa. The overall proportion of adult A. hebraeum that were positive for the gltA and ompA genes was 0.63 (108/180). The overall proportion of nymphs positive for the gltA and ompA genes was 0.62 (23/37) and 0.22 (20/90) from cattle blood. A positive R. africae infection was inferred by analysis of 26 sequences of the ompA, gltA, ompB, 17kDa and sca4 genes. Neighbour-joining and Maximum Likelihood analysis revealed that the study isolates were closely related to R. africae isolates from South Africa deposited in GenBank, forming a clade that was separate from north, east and west African strains. This study provides new information on the epidemiology and phylogeny of R. africae isolated from A. hebraeum ticks in the Eastern Cape province of South Africa. The heterogeneity observed between R. africae isolates from South Africa deposited in GenBank and R. africae isolates from Africa retrieved from Genbank highlight the importance of differentiation and tracking of the genetic movement among R. africae isolates in southern Africa for the better characterisation of ATBF cases, especially in rural communities and travellers visiting the region.

Olfactory responses of Amblyomma maculatum to rumen fluid and other odourants that attract blood-seeking arthropods

Amblyomma maculatum Koch (Ixodida: Ixodidae) has emerged as a significant vector of human and companion animal diseases in the U.S.A. When expanding in range, A. maculatum can be difficult to collect in the field and control on livestock. A novel method is needed to improve the field collection of A. maculatum, as well as to control their effects as ectoparasites of livestock and companion animals. The present study aimed to test the effects of known volatiles on the activation and selection choices of A. maculatum in a laboratory-based Y-tube assay and field-based assays. Although the majority of adult A. maculatum were activated to move by five of the seven semiochemicals tested, only rumen fluid significantly attracted ticks to make a selection in the Y-tube apparatus. Rumen fluid attracted the most A. maculatum in the laboratory, with 56% (84/150) making it to the rumen Y-tube arm, although the results were not replicated in semi-field experiments. These studies highlight the need for continued work to identify attractants for tick vectors that will assist field collections. These attractants could also be incorporated into management strategies that lead to prevention technologies to reduce tick burdens on cattle or in risk areas of humans.

Multi-scale patterns of tick occupancy and abundance across an agricultural landscape in southern Africa

Land use influences the prevalence and distribution of ticks due to the intimate relationship of ticks with their environment. This relationship occurs because land use alters two essential tick requirements: vertebrate hosts for blood meals and a suitable microclimate when off-host. Given the risks to human and animal health associated with pathogens transmitted by ticks, there is an ongoing need to understand the impact of environmental drivers on tick distributions. Here, we assessed how landscape features, neighborhood effects, and edges influenced tick occupancy and abundance across an agricultural landscape in southern Africa. We found that Rhipicephalus appendiculatus and Rhipicephalus simus increased in abundance closer to protected savanna, while Haemaphysalis elliptica increased in abundance closer to human habitation. The composition of the landscape surrounding savanna patches also differentially influenced the occupancy of each tick species; H. elliptica was more likely to be found in savanna patches surrounded by subsistence agriculture while R. appendiculatus and R. simus were more likely to be found in savanna surrounded by sugarcane monocultures. At the local scale we found that R. appendiculatus and R. simus avoided savanna edges. The availability of hosts and variation in vegetation structure between commercial agriculture, subsistence agriculture, and savanna likely drove the distribution of ticks at the landscape scale. Understanding how anthropogenic land use influences where ticks occur is useful for land use planning and for assessing public and animal health risks associated with ticks and tick-borne diseases.

The first detection of Amblyomma hebraeum (Acarina: Ixodidae) in Iran

Amblyomma hebraeum (Koch, 1844), has been already reported from along the coast of South Africa, eastern Swaziland, southern Mozambique, eastern Botswana, and in southern and eastern regions of Zimbabwe. The aim of this study was to determine the ecto-parasites and the harmful arthropods of wildlife animals, collected from cages of Shiraz zoo in Fars province, southern Iran, in 2016. Accordingly, the Ticks collected from the white camels were identified as Amblyomma hebraeum. This species which was collected from white camel of Fars province, is reported for the first time from Iran. The presence of A. hebraeum poses a serious threat to the livestock industry in Iran and there is need to investigate the presence of this species in Iranian livestock.

The dynamics of questing ticks collected for 164 consecutive months off the vegetation of two landscape zones in the Kruger National Park (1988–2002). Part I. Total ticks, Amblyomma hebraeum and Rhipicephalus decoloratus

Despite a large number of studies on tick biology, there is limited information on long- term changes in tick populations. This study thus aimed to assess the long-term population dynamics of questing ixodid ticks in two landscape zones of the Kruger National Park (KNP). Questing ixodid ticks were collected in the KNP from August 1988 to March 2002 by monthly dragging of the vegetation in three habitats (grassland, woodland and gully) at two sites (Nhlowa Road and Skukuza). Findings pertaining to total tick numbers and Amblyomma hebraeum and Rhipicephalus decoloratus specifically are presented here. Fourteen tick species were collected, as well as four others that could be identified only to generic level. More ticks (211 569 vs 125 810) were collected at Nhlowa Road than at Skukuza. Larvae were the most commonly collected stage of all the major tick species. A. hebraeum was the most commonly collected tick (63.6%) at Nhlowa Road, whereas R. decoloratus accounted for 15.3% of the ticks collected there. At Skukuza, 31.6% and 27.1% of the collected ticks were R. decoloratus and A. hebraeum respectively. Most A. hebraeum larvae were collected in summer and the fewest in winter and early spring, mostly in woodland and least often in grassland habitats. Most R. decoloratus larvae were collected in spring and the fewest in autumn and winter, and were more frequently collected in woodland and grassland than in gullies. The largest collections of most tick species were made during the early 1990s, while numbers were lowest in the mid-1990s after a drought during 1991 and 1992 and then increased towards the late 1990s, followed by a final decrease. The changes in tick numbers over time probably reflect differences in their host communities at the two sites and the effect of climatic conditions on both hosts and free-living ticks. The population dynamics of questing ticks reflect a complex interaction between ticks, their hosts and the environment.

Attachment kinetics of the adult tick Amblyomma variegatum to cattle

At the beginning of the 1999 rainy season, three traditional cattle herds were monitored for 48 days while grazing in the bushy savannah of southwestern Burkina Faso. Cattle in each herd were caught on several occasions each day and the attached ticks were counted. This confirmed that Amblyomma variegatum Fabricius (Acari: Ixodidae) adults picked up in the pastures mainly attach to the interdigital areas (87% of the 791 ticks captured), and reach the predilection sites later (chest and udder/inguinal area) when the animals lie down. As many females as males attached to the hosts, but the seasonal distribution was very heterogeneous, with only a few females attaching as long as the humidity rate remained low. It is suggested that this prevents eggs from being laid when conditions are not optimal for their survival and that of the larvae. Ticks attached all day but the number picked up hourly and daily varied greatly according to their density on the pasture. As a general trend, confirmed by another study carried out in 2005, the number of ticks picked up daily increased from less than one tick/animal/day, before the onset of the rainy season, to 6.5 (+/- 1.5) ticks/animal/day on average during the infestation peak, which lasted 6-8 weeks, until early or mid-July. The number then decreased to less than one tick/animal/day from the end of July onwards. The infestation on the predilection sites followed the same trend, with a daily tick burden increase of three to five A. variegatum adults, depending on herd and year, during the infestation peak.