Species richness and adaptation of the invasive cattle tick, Rhipicephalus microplus (Acari: Ixodidae) on camps grazed by sheep in the Eastern Cape Province, South Africa.

The seasonal dynamics and distribution of ticks play a pivotal role in the epidemiology of tick-borne diseases. The objective of this study was to establish the seasonal abundance and species richness of questing ixodid ticks on Amathole Montane Grassland camps grazed by sheep. Ticks questing for hosts were collected monthly for a period of three years by dragging flannel strips attached to a wooden spar over the vegetation. At each occasion, six replicate drag-samples were made in camps grazed by sheep. Of the questing ticks (n = 14 891) collected from the vegetation, the most abundant larvae were those of Rhipicephalus microplus (95.04%) followed by Rhipicephalus appendiculatus (2.32%), Rhipicephalus evertsi (1.56%), Rhipicephalus decoloratus (1.03%), Rhipicephalus simus (0.03) and Amblyomma hebraeum (0.02%). Comparing the two Rhipicephalus (Boophilus) spp., R. microplus (98.9%) outcompete the indigenous tick, R. decoloratus (1.1%). The R. microplus larvae were significantly higher (P < 0.05) in 2015 (2.11±0.108), 2016 (2.02 ± 0.076) and 2017 (1.94±0.075) during spring than any other season. There were no significant differences (P ˃ 0.05) from R. appendiculatus questing ticks collected in autumn (0.27±0.007; 0.30±0.052) and spring (0.33±0.007; 0.20±0.052) for 2015 and 2016, respectively. The study showed that the cattle tick, R. microplus adapted very well on host species, in this case sheep, and encroached to areas that were too cold for its adaptation.

Prevalence and tick loads in Nguni cattle reared in different environmental conditions across four provinces of South Africa.

Background and Aim: In tropical and subtropical countries, ixodid ticks are among livestock's most economically important ectoparasites. Although Nguni cattle from South Africa have adapted to harsh environments, it is unknown whether they will be resistant to ticks, and the diseases carried by ticks under various climatic conditions. Therefore, this study aimed to compare tick load and estimate the prevalence of different tick species among Nguni cattle under different environmental conditions. Materials and Methods: Tick counts were conducted monthly under natural challenges over 2 years on 586 Nguni cattle located at ARC-Roodeplaat and Loskop farms (warmer climate), Mukhuthali Nguni Community and the University of Fort Hare farms (cooler climate). The generalized linear model procedure of the Statistical Analysis System was used to analyze the data. It fitted the location (farm), sex, year, month or season, and animal age as covariates. Results: The tick species (relative prevalence) observed were as follows: Amblyomma hebraeum (42%), Rhipicephalus evertsi (22%), Rhipicephalus (Boophilus) spp. (16%), Rhipicephalus appendiculatus (11%), Hyalomma marginatum (5%), and Rhipicephalus simus (4%). Tick infestation was significantly affected by location, season, year, month of the tick counting and age of the animal. Loskop farm had the highest tick count (m = 30.69) and showed the largest variation in tick count. Compared to the other seasons, higher tick counts were seen during the hot-dry (September-November) and hot-wet (December-February) seasons. A. hebraeum was the dominant tick species across all four farms, followed by R. evertsi. The perianal region (under the tail head), the perineum and the belly body locations were the most preferred tick attachment sites. Conclusion: These results provide useful information for developing appropriate control strategies for ticks and tick-borne diseases in these provinces of South Africa. Further work must investigate the feasibility of genetic improvement for tick resistance.

Modelling the adsorption of natural organic matter on Ag (111) surface: Insights from dispersion corrected density functional theory calculations.

Understanding the nature of the interactions between natural organic matter (NOM) and engineered nanoparticles (ENPs) is of crucial importance in understanding the fate and behaviour of engineered nanoparticles in the environment. In the present study, dispersion-corrected density functional theory (DFT-D) has been used to elucidate the molecule-surface interactions of higher molecular weight (HMW) NOM ambiguously present in the aquatic systems, namely: humic acid (HA), fulvic acid (FA) and protein Cryptochrome (Cry) on Ag (111) surface. Investigations were done in the gas phase and to mimic real biological environment, water has been used as a solvent within the conductor-like screening model (COSMO) framework. The calculated adsorption energies for HA, FA and Cry on Ag (111) surface were -27.90 (-18.45) kcal/mol, -38.28 (-18.68) kcal/mol and -143.89 (-150.82) kcal/mol respectively in the gas (solvent) phase and the equilibrium distances between the surface and HA, FA and Cry molecules were 1.87 (2.18) Å, 2.31(2.31) Å and 1.91 (1.70) Å respectively in the gas (solvent) phase. In both gas and water phase Cry showed stronger adsorption which means it has a stronger interaction with Ag (111) surface compared to HA and FA. The results for adsorption energy, solvation energy, isosurface of charge deformation difference, total density of state and partial density of states indicated that indeed these chosen adsorbates do interact with the surface and are favourable on Ag (111) surface. In terms of charge transfer, one of many calculated descriptors in this study, electrophilicity (ω) concur that charge transfer will take place from the adsorbates to Ag (111) surface.

In search of the Rhipicephalus (Boophilus) microplus in the western-central regions of the Eastern Cape Province, South Africa.

The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an economically important tick that parasitises cattle and is found on other host species if they graze with cattle. The R. (B.) microplus is a highly adapted tick species prevalent in tropical and subtropical regions of the world. In Africa, it has expanded its range and was reported to supersede the native tick, R. (B.) decoloratus. The objective of the study was to determine the distribution of R. (B.) microplus under different ecological zones in the western-central regions of Eastern Cape Province. Engorged adult blue ticks were collected monthly from 360 randomly selected cattle and free living ticks from six replicate drags of the vegetation over a period of 1 year at Bedford Dry Grassland (BDG), Kowie Thicket (KT) and Bhisho Thornveld (BT). A special attention was paid to the lower perineum, neck, dewlap and ventral body parts which are the preferred sites for blue ticks during sampling. In this study, 9 species of ticks which grouped under 5 genera were identified. The identified species of ticks were Amblyomma hebraeum, Haemaphysalis elliptica, Hyalomma rufipes, Ixodes pilosus, R. (B.) decoloratus, R. appendiculatus, R. evertsi evertsi, R. follis and R. simus. Only adult R. (B.) decoloratus (n = 8090) ticks were collected from cattle between April 2016 and March 2017. A total of 4382 females and 3708 males of R. (B.) decoloratus were recovered during the survey. Of the ticks (n = 2885) collected from the vegetation, R. (B.) decoloratus was the most abundant species with a relative prevalence of 58.16%, followed by R. appendiculatus (18.37%) and R. evertsi evertsi (16.90%). Least abundant ticks were H. rufipes (2.98%), A. hebraeum (2.46%), H. elliptica (0.38%), R. follis (0.34%), I. pilosus (0.24%) and R. simus (0.17%). The distribution of R. (B.) decoloratus ticks differ significantly (P < 0.05) among the vegetation types. Significantly more (P < 0.05) engorged R. (B.) decoloratus were collected in KT during summer season (1.39 ± 0.063 females and 1.30 ± 0.063 males) compared to other vegetation types. The R. (B.) decoloratus larvae were significantly higher (P < 0.05) in BT (20.56±1.154) and KT (18.50±1.154) vegetation types during the spring season. R. (B.) microplus was not found in the present study, signifying that it is not yet established in western-central regions of the Eastern Cape Province and as such, continuous monitoring would be advisable.

Ecological preferences and seasonal dynamics of ticks (Acari: Ixodidae) on and off bovine hosts in the Eastern Cape Province, South Africa.

A total of 31,425 ticks were collected from 10 cattle and also from six drag-samples during the 12-month study period. Adult ticks were removed from the right hand side of each animal and all instars of ticks were placed in containers filled with 70% ethanol. Based on morphological traits, 10 tick species were identified: Rhipicephalus (Boophilus) decoloratus (32.5%), R. evertsi evertsi (18.8%), R. appendiculatus (17.3%), Amblyomma hebraeum (16.3%), R. simus (7.7%), Ixodes pilosus (3.8%), Hyalomma rufipes (3.5%), R. follis (0.08%), Haemaphysalis elliptica (0.04%), H. silacea (0.02%). The southern African yellow dog tick, H. elliptica, was only found on vegetation. The agro-ecological zones differ significantly in tick species and their distribution. The A. hebraeum and R. evertsi evertsi counts were higher in Kowie Thicket (KT) during summer season (2.05 ± 0.01 and 1.00 ± 0.09, respectively) compared to Bedford Dry Grassland (BDG) and Bhisho Thornveld (BT) veld types. In all vegetation types, R. appendiculatus had higher counts in KT in spring (0.91 ± 0.08), summer (0.78 ± 0.08) and winter (0.78 ± 0.08). Rhipicephalus (Boophilus) decoloratus was more frequent in the BT (1.78 ± 0.11) during the summer season. BDG had lower tick infestation with R. evertsi evertsi being the most frequent species in summer. No H. rufipes was collected in the KT. Of epidemiological interest, R. (B.) microplus was absent in the study area which needs further investigation. Within the context of this study, we found agro-ecological differences and seasonal variations to have influence on tick species distribution.

Displacement of Rhipicephalus decoloratus by Rhipicephalus microplus (Acari: Ixodidae) in the Eastern Cape Province, South Africa.

The objective of the study was to establish to what extent the native tick species Rhipicephalus decoloratus has been displaced by the invasive introduced tick, Rhipicephalus microplus at two communally grazed areas in the Eastern Cape Province, South Africa. To this end ticks were collected monthly from five cattle over a period of 2 years and from 10 drag-samples of the vegetation over a period of 1 year at each locality. Whereas 10 years previously only R. decoloratus and no R. microplus had been recorded in the vicinity of the two sites, R. microplus now comprised the bulk of collections at both. Furthermore, significantly more R. microplus were collected from cattle at both localities during the 2nd year of the survey than during the 1st. In addition to 83 instances of intraspecific coupling, there were 17 instances of R. microplus males coupled with R. decoloratus females. Collections made from cattle and goats on two farms close to the study sites revealed that R. microplus was present on both host species and that it significantly outnumbered R. decoloratus on one of the farms. Rhipicephalus decoloratus and R. microplus larvae as well as larvae exhibiting characteristics of both species were collected from the vegetation.

Species composition and geographic distribution of ticks infesting cattle, goats and dogs in a temperate and in a subtropical region of south-east Africa.

The species and distribution of ticks infesting cattle, goats and dogs in the eastern region of the Eastern Cape Province, South Africa and Maputo Province, Mozambique were determined from collections made from these animals at 72 localities in the former region and 30 in the latter. Eleven ixodid and one argasid species were recovered in the Eastern Cape Province and 15 ixodid species in Maputo Province. The most common ticks infesting cattle and goats in both provinces were Amblyomma hebraeum, Rhipicephalus (Boophilus) microplus, Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi. The dominant species on dogs were Haemaphysalis elliptica and Rhipicephalus simus. The geographic distributions of the major species and some of the minor species in both regions were plotted. The partial or complete displacement of the indigenous tick Rhipicephalus (Boophilus) decoloratus by the introduced species R. (B.) microplus was a major feature of both surveys.

The prevalence and distribution of Argas walkerae (Acari: Argasidae) in the eastern region of the Eastern Cape Province, South Africa.

The prevalence and geographic distribution of the fowl tampan, Argas walkerae Kaiser & Hoogstraal, 1969 was determined in the eastern region of the Eastern Cape Province, South Africa by inspecting two fowl houses in the vicinity of each of 72 randomly selected communal cattle dip-tanks. Tampans were collected from 102 (70.8%) of the 144 fowl houses in the neighbourhood of 57 (79.2%) of the 72 selected dip-tanks, and the localities of the collections were mapped. Argas walkerae was present in fowl houses from the warm coastal regions of the Indian Ocean in the south to the cold and mountainous Drakensberg in the north-east of the Province. Taking into account the probable sensitivity of the sampling method, it is estimated that A. walkerae is likely to be present in fowl houses belonging to between 74 and 84% of communities making use of cattle dip-tanks in the eastern region of the Eastern Cape Province, and that when it is present, between 64 and 75% of fowl houses will be infested. The geographic distribution of A. walkerae seemed to be more strongly associated with the presence of fowls and fowl houses containing raw or processed wood in their structure than with climate.

Goats as alternative hosts of cattle ticks.

The objective of this study was to compare the presence on goats and cattle of adult ticks that usually infest cattle. To this end ticks collected from sets of five goats were compared with those collected from sets of five cattle at 72 communal dip-tanks in the eastern region of the Eastern Cape Province. Amblyomma hebraeum was present on goats at 25 and on cattle at 39 dip-tanks, and a total of 61 goats and 138 cattle were infested. Adult Rhipicephalus (Boophilus) microplus was present on goats at 48 and on cattle at 69 dip-tanks, and a total of 113 goats and 242 cattle were infested. The lengths of 84 of 148 female R. (Boophilus) microplus collected from the goats exceeded 5 mm or more, indicating that they could successfully engorge on these animals. The differences between the proportions of dip-tanks at which A. hebraeum or R. (Boophilus) microplus was present on goats and cattle and also between the proportions of goats and cattle that were infested were significant (Chi-square test, P < 0.01). Adult Rhipicephalus appendiculatus was present on goats at 70 and on cattle at 67 dip-tanks, and a total of 296 goats and 271 cattle were infested. The proportion of dip-tanks at which cattle were infested did not differ significantly from the proportion of tanks at which goats were infested (Fischer's exact probability test, P = 0.44), but the proportion of infested cattle was significantly lower than the proportion of infested goats (Chi-square test, P < 0.05). Adult Rhipicephalus evertsi evertsi was present on goats and cattle at all 72 sampling localities, and a total of 334 goats and 316 cattle were infested. The proportion of infested cattle was significantly lower than the proportion of infested goats (Chi-square test, P < 0.05). These results underscore the necessity of including goats in any tick control programme designed for cattle at the same locality.

Ixodid ticks on dogs in the eastern region of the Eastern Cape Province, South Africa.

The objective of this study was to determine the species composition and geographic distribution of ixodid ticks infesting domestic dogs in the eastern region of the Eastern Cape Province. Seventy-two communal cattle dip-tanks within this region were randomly selected as survey localities and their geographic coordinates recorded. In addition to ticks that were collected from five cattle and five goats at each of the dip-tanks, ticks were also collected from five dogs whenever possible. No dogs were available at 19 dip-tanks and no ticks were collected from dogs at 13 dip-tanks, while ticks were collected from 132 of 200 dogs at 40 dip-tanks. Eight ixodid tick species were collected from these dogs, and Haemaphysalis leachi followed by Rhipicephalus appendiculatus and Rhipicephalus simus were present on dogs at the largest number of dip-tanks. Seven dogs were simultaneously infested with three tick species and one with four species. The geographic distributions of Amblyomma hebraeum, H. leachi, R. appendiculatus and R. simus recovered from the dogs lay within the ranges previously reported for these ticks.