Amblyomma Hebraeum Research Articles

Ascaris lumbricoides and ticks associated with sensitization to galactose α1,3-galactose and elicitation of the alpha-gal syndrome

IgE to galactose alpha-1,3 galactose (alpha-gal) causes alpha-gal syndrome (delayed anaphylaxis after ingestion of mammalian meat). Development of sensitization has been attributed to tick bites; however, the possible role of other parasites has not been well studied. Our aims were to assess the presence, relative abundances, and site of localization of alpha-gal-containing proteins in common ectoparasites and endoparasites endemic in an area of high prevalence of alpha-gal syndrome, as well as to investigate the ability of ascaris antigens to elicit a reaction in a humanized rat basophil invitro sensitization model. Levels of total IgE, Ascaris-specific IgE, and alpha-gal IgE were measured in sera from patients with challenge-proven alpha-gal syndrome and from controls without allergy. The presence, concentration, and localization of alpha-gal in parasites were assessed by ELISA, Western blotting, and immunohistochemistry. The ability of Ascaris lumbricoides antigen to elicit IgE-dependent reactivity was demonstrated by using the RS-ATL8 basophil reporter system. Alpha-gal IgE level correlated with A lumbricoides-specific IgE level. Alpha-gal protein at 70 to 130 kDa was detected in A lumbricoides at concentrations higher than those found in Rhipicephalus evertsi and Amblyomma hebraeum ticks. Immunohistochemistry was used to localize alpha-gal in tick salivary acini and the helminth gut. Non-alpha-gal-containing A lumbricoides antigens activated RS-ATL8 basophils primed with serum from subjects with alpha-gal syndrome. We demonstrated the presence, relative abundances, and site of localization of alpha-gal-containing proteins in parasites. The activation of RS-ATL8 IgE reporter cells primed with serum from subjects with alpha-gal syndrome on exposure to non-alpha-gal-containing Alumbricoides proteins indicates a possible role of exposure to A lumbricoides in alpha-gal sensitization and clinical reactivity.

A Pilot Study on the Microbiome of Amblyomma hebraeum Tick Stages Infected and Non-Infected with Rickettsia africae.

Variation in tick microbiota may affect pathogen acquisition and transmission but for many vector species, including Amblyomma hebraeum, components and determinants of the microbiome are unidentified. This pilot study aimed to determine baseline microbial community within A. hebraeum nymphs infected- and non-infected with Rickettsia africae from the environment, and within adult ticks infected- and non-infected with R. africae collected from cattle sampled from two locations in the Eastern Cape province of South Africa. Adult A. hebraeum ticks (N = 13) and A. hebraeum nymph (N = 15) preliminary screened for R. africae were randomly selected and subjected to Illumina sequencing targeting the v3–v4 hypervariable regions of the 16S rRNA gene. No significant difference in microbial community composition, as well as rarefied OTU richness and diversity were detected between adults and nymphs. Nymphs showed a higher richness of bacterial taxa indicating blood-feeding could have resulted in loss of microbial diversity during the moulting stage from nymph to adult. Core OTUs that were in at least 50% of nymphs and adults negative and positive for Rickettsia at 1% minimum relative abundance were Rickettsia, Coxiella and Ruminococcaceae UCG-005 with a single genus Arsenophonus occurring only in nymphs negative for Rickettsia. Ehrlichia spp. was present in only four nymphal ticks positive for Rickettsia. Interestingly, Rickettsia aeschlimannii was found in one nymph and one adult, indicating the first ever detection of the species in A. hebraeum. Furthermore, A. hebraeum harboured a Coxiella-like endosymbiont, which should be investigated further as Coxiella may affect the viability and transmission of other organisms.

Knowledge, attitudes and practices on African tick bite fever of rural livestock communities living in a livestock-wildlife interface area in the Eastern Cape Province of South Africa

BackgroundAfrican tick bite fever (ATBF) caused by Rickettsia africae and transmitted by Amblyomma spp. ticks is one of the zoonotic tick-borne fevers from the spotted fever group (SFG) of rickettsiae, which is an emerging global health concern. There is paucity of information regarding the occurrence and awareness of the disease in endemic rural livestock farming communities living in livestock-wildlife interface areas in South Africa.MethodsThe purpose of the study was to assess the level of knowledge, attitudes and practices on ticks and ATBF infection from a community living in livestock-wildlife interface areas in South Africa. A focus group discussion (FGD) was carried out followed by verbal administration of a standardized semi-structured questionnaire a month later to 38 rural livestock farmers (23 from Caquba area and 15 from Lucingweni area where A. hebraeum was absent). An FGD was conducted in Caquba (situated at the livestock-wildlife interface where Amblyomma hebraeum was prevalent on cattle and infected with Rickettsia africae) in the O.R. Tambo district of the Eastern Cape province of South Africa.ResultsResults from the FGD and questionnaire survey showed that participants from the two rural communities were not aware of ATBF and were not aware that ticks are vectors of the disease. Respondents from Caquba reported of having frequent exposure to tick bites (91.3%, 21/23) specifically from the anthropophilic A. hebrauem which they were able to identify as Qwelagqibe in IsiXhosa (their vernacular). Thirteen out of 15 (86.7%) of respondents from Lucingweni reported that they had never been bitten by ticks, which corresponded with the absence of A. hebraeum from their locality as evidenced from results of a concurrent study on prevalence of ticks on livestock in the area. Both communities confirmed to being “very concerned” of tick bites and we presume this was more related to the localized wounds from the bites than to the diseases transmitted by the ticks.ConclusionsWe recommend future studies encompassing seroprevalence of ATBF in Caquba and other communities at risk in South Africa including establishing surveillance systems to monitor the seasonal infection rates in ticks, cattle and humans.

Spatial clustering of fourteen tick species across districts of Zimbabwe

BackgroundTicks transmit several diseases that result in high morbidity and mortality in livestock. Tick-borne diseases are an economic burden that negatively affect livestock production, cost countries billions of dollars through vaccine procurement and other disease management efforts. Thus, understanding the spatial distribution of tick hotspots is critical for identifying potential areas of high tick-borne disease transmission and setting up priority areas for targeted tick disease management. In this study, optimised hotspot analysis was applied to detect hotspots and coldspots of 14 common tick species in Zimbabwe. Data on the spatial distribution of tick species were obtained from the Epidemiology Unit of the Division of Veterinary Field Services of Zimbabwe.ResultsA total of 55,133 ticks were collected with Rhipicephalus decoloratus being the most common species (28.7%), followed by Amblyomma hebraeum (20.6%), and Rhipicephalus sanguineus sensu lato (0.06%) being the least common species. Results also showed that tick hotspots are species-specific with particular tick species occupying defined localities in the country. For instance, Amblyomma variegatum, Rhipicephalus appendiculatus, Rhipicephalus decoloratus, Rhipicephalus compostus, Rhipicephalus microplus, Rhipicephalus pravus, and Rhipicephalus simus were concentrated in the north and north eastern districts of the country. In contrast, Amblyomma hebraeum, Hyalomma rufipes, Hyalomma trancatum and Rhipicephalus evertsi evertsi were prevalent in the southern districts of Zimbabwe.ConclusionThe occurrence of broadly similar hotspots of several tick species in different districts suggests presence of spatial overlaps in the niche of the tick species. As ticks are vectors of several tick-borne diseases, there is high likelihood of multiple disease transmission in the same geographic region. This study is the first in Zimbabwe to demonstrate unique spatial patterns in the distribution of several tick species across the country. The results of this study provide an important opportunity for the development of spatially-targeted tick-borne disease management strategies.

Some gastrointestinal nematodes and ixodid ticks shared by several wildlife species in the Kruger National Park, South Africa.

Parasite surveys were conducted for 1–2 years in the Kruger National Park (KNP), South Africa on blue wildebeest, impalas, greater kudus, common warthogs and scrub hares. The host associations of some of the gastrointestinal nematode species infecting ≥60% of at least one of the five host species, were determined. These were Agriostomum gorgonis, Cooperia acutispiculum, Cooperia connochaeti, Cooperia hungi, Cooperia neitzi, Cooperioides hamiltoni, Gaigeria pachyscelis, Haemonchus bedfordi, Haemonchus krugeri, Haemonchus vegliai, Impalaia tuberculata, Longistrongylus sabie, Strongyloides papillosus, Trichostrongylus deflexus and Trichostrongylus thomasi. Although the prevalence of Trichostrongylus falculatus did not exceed 50% in any host species, it was present in all five hosts. Nematodes in the KNP range from those exhibiting strict host associations to generalists. Nematode-host associations may be determined by host feeding patterns and habitat use. Eight ixodid tick species were commonly collected from the same animals and in 2–3 year long surveys from plains zebras and helmeted guinea fowls: Amblyomma hebraeum, Amblyomma marmoreum, Hyalomma truncatum, Rhipicephalus appendiculatus, Rhipicephalus decoloratus, Rhipicephalus evertsi evertsi, Rhipicephalus simus and Rhipicephalus zambeziensis. Host specificity was less pronounced in ixodid tick species than in nematodes and the immature stages of five tick species infested all host species examined.

Prevalence of serum antibodies of tick-borne diseases and the presence of Rhipicephalus microplus in communal grazing cattle in the north-eastern region of the Eastern Cape Province of South Africa.

A survey to determine the prevalence of tick-borne diseases (TBDs) and ticks infesting cattle was conducted in the communal areas of the north-eastern region of the Eastern Cape Province (ECP) between January 2019 and October 2019. Tick counts, packed cell volume (PCV), body condition scores (BCS), and serological test for TBDs were seasonally conducted in communally grazed cattle (n = 240) in Joe Gqabi district in two local municipalities (Elundini and Senqu). A standard indirect fluorescent antibody test (IFAT) was used to determine antibodies to Babesia bigemina, Babesia bovis, and Ehrlichia ruminantium and indirect enzyme-linked immunosorbent assay (ELISA) was employed for antibodies to Anaplasma marginale detection. The highest tick loads were observed on cattle during the hot-wet and post-rainy seasons and lowest during the cool-dry season. The E. ruminantium prevalence in Elundini was 16% and 14% in post-rainy and hot-dry seasons respectively and 15% at Senqu during the post-rainy season. B. bigemina prevalence was highest at Elundini (18%) and Senqu (16%) during the post-rainy season and hot-wet season respectively. Cattle BCS was negatively correlated with E. ruminantium (P < 0.01; r = - 0.203), B. bovis (P < 0.01; r = - 0.125), and A. marginale (P < 0.01; r = - 0.122) seroprevalence. The PCV was negatively correlated with B. bigemina (P < 0.01; r = - 0.138) seroprevalence. On the other hand, E. ruminantium was positively correlated with Amblyomma hebraeum (P < 0.05; r = 0.112) infestation, while B. bovis (P < 0.05; r = 0.134) and B. bigemina (P < 0.05; r = 0.188) were positively correlated with Rhipicephalus microplus infestation, and B. bigemina (P < 0.05; r = 0.077) was positively correlated with Rhipicephalus decoloratus infestation. Our study reports for the first time the presence of R. microplus in the study area. Further research is, however, needed to better understand seroprevalence and the transmission mode of TBDs to cattle so that effective disease control measures can be developed.

A preliminary study on the Monthly dynamics of cattle tick infestation in Sokoto, north western Nigeria

The distribution and monthly dynamics of bovine ixodids in Sokoto Township and environs were recorded between Jan 2009 and Dec 2010. Monthly tick collections were performed on 400 animals from which a total of 12, 296 ticks were collected. Ticks from each cattle were collected separately using a pair of blunt forceps, into labelled universal bottles containing 70% ethanol into which 5% glycerine was added to keep specimens better preserved. On each label, the location, breed of the animal, number of ticks and date of collection were recorded. In the laboratory, Ticks were placed into petri dishes, counted, examined and identified with the aid of a dissecting stereoscope based on morphological Characteristics and aided by the use of standard keys according to Hoogstraal (1956) and Walker et al. (2003). These include Hyalomma truncatum (15.5%), Hyalomma dromedarii (13.3%), Boophilus decolaratus (11.3%) Amblyomma variegatum (10.6%), Hy. impeltatum, (10.1%), Hy. rufipes (9.4%), Hy. impressum (7.4%), Boophilus annulatus (4.4%), B. geigyi (4.3%), Rhipicephalus sanguineus (4.1%) Amblyomma hebraeum (3.4%), Rh. evertsi (2.6%), A. pomposum (2.0%), Rh. lunulatus (1%) and Rh. senegalensis (0.5%). Hyalomma. truncatum, Hy. impeltatum, Hy. Impress B. annulatus, A. hebraeum, A. pomposum, Rh. lunulatus and Rh. senegalensis were recorded for the first time in the Study area. The distribution and dynamics of cattle ixodid ticks has not been hitherto chronicled in the study area.

Genomic Profiling for Piroplasms in Feeding Ixodid Ticks in the Eastern Cape, South Africa.

Importation of tick-infected animals and the uncontrollable migration of birds and wild animals across borders can lead to geographical expansion and redistribution of ticks and pathogen vectors, thus leading to the emergence and re-emergence of tick-borne diseases in humans and animals. Comparatively, little is known about the occurrence of piroplasms in ixodid ticks in the Eastern Cape, South Africa, thus necessitating this study, which is aimed at detecting piroplasms (Theileria and Babesia) from feeding tick samples collected from cattle, sheep, and goats in selected sites in the Eastern Cape, South Africa. A total of 1200 feeding ixodid ticks collected from farm animals at selected homesteads were first subjected to molecular identification using mitochondrial 12S ribosomal RNA (rRNA) gene by PCR and were further tested for the presence of piroplasms through amplification of the 18S rRNA gene via nested-PCR followed by sequencing of the PCR products. The results indicated that 853 (71.1%) corresponded to the genus Rhipicephalus, 335 (27.9%) corresponded to genus Amblyomma, and 12 (1%) corresponded to genus Haemaphysalis. Amblyomma hebraeum and Rhipicephalus appendiculatus were the most common identified ticks from this study. The 18S rRNA nested-PCR revealed that 44 (3.7%) samples were confirmed positive for Theileria. A homology search for the generated sequences revealed a high percentage identity of 98–98.9% similarity to T. buffeli, T. orientalis, and T. sergenti in the GenBank. Based on the results obtained herein, we conclude that there is a big diversity of Theileria species; therefore, we suggest that this research should cover more geographical areas in order to reveal the true prevalence of this pathogen in the studied area because this will be a great step in the possible prevention of an outbreak that could have devastating effects on livestock production and human health in both the studied areas and South Africa at large.

A comparison of the cuticular properties of argasid and ixodid ticks: Ornithodoros moubata (Argasidae) vs. Amblyomma hebraeum and Ixodes pacificus (Ixodidae)

Ticks (Chelicerata, Ixodida) are blood-feeding ectoparasites believed to have evolved at least about 120 millions of years ago and found worldwide. However, many aspects of their unique life cycle and anatomy, including their mechanical properties, remain to be understood. Here, we compared the mechanical properties of the cuticle of the argasid tick Ornithodoros moubata to those of two species of ixodid tick, Amblyomma hebraeum and Ixodes pacificus that we explored in our earlier studies of the tick exoskeleton. Significant differences were expected given the substantial difference in life cycle, including a five-fold increase during the repeated adult blood meal for female O. moubata vs. 70- to 120-fold during the single feeding of the adult female A. hebraeum and I. pacificus. We demonstrate here that the layered structure and mechanical properties (stiffness and viscosity) of the cuticle show minor differences, but the difference in cuticle thickness is substantial. Ductility is lost during feeding; reduced pH restores ductility. Previous work suggests that this occurs in vivo in engorged ixodid ticks; there is no evidence of this occurring in vivo in O. moubata. Thinning of cuticle in O. moubata fed females is consistent with the predicted stretch of cuticle due to the blood meal; there is no evidence of cuticle synthesis during the short feeding period. Dimensional analysis suggests that the soft feel of argasid ticks is related to cuticle thickness, not cuticle stiffness. Relative to argasid ticks, the hard ixodid ticks accommodate a ca. 20-fold higher size of blood meal by starting with a thicker cuticle and growing much additional cuticle during engorgement.

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.

Resistance of ticks on cattle to amitraz in Zimbabwe.

Resistance of one host and three host ticks on cattle to amitraz was studied using samples from five diptanks in the Domboshawa Communal Land Area of Zimbabwe. A random tick profile and a questionnaire survey on the tick control practices of the area were also carried out. Engorged Rhipicephalus (Boophilus) decoloratus, Rhipicephalus appendiculatus and Amblyomma hebraeum females were randomly collected from cattle presented for dipping at the 5 diptanks and were allowed to oviposit separately at T: 28°C and RH: 85-95%. Larvae obtained were tested for resistance against various amitraz concentrations (1-0.0078125%) using the Larval Packet Test (LPT) and were compared with susceptible reference strains of R. (B.) decoloratus (Makuti strain, 2017), R. appendiculatus (Lake Chivero strain, 2015) and A. hebraeum (Lake Mutirikwi strain, 2017). The most abundant tick species were R. (B.) decoloratus (27.2%), Hyalomma rufipes (20.0%), H. truncatum (16.0%), R. appendiculatus (12.0%) and R. evertsi evertsi (11.9%). Amblyomma hebraeum (8.6%) and A. variegatum (1.8%) were the least common in the collection; this suggests that they were not well established in Domboshawa. Low amitraz resistance (RL = I) was detected only in R. (B.) decoloratus at 2 of the 5 diptanks. In the future, decentralised tick control due to inadequate and inconsistent supply of acaricides could introduce a number of factors which could contribute towards resistance development.

Genetic diversity of Ehrlichia ruminantium field strains from selected farms in South Africa.

Heartwater is a tick-borne disease caused by the intracellular rickettsial parasite Ehrlichia ruminantium and transmitted by Amblyomma hebraeum ticks. Heartwater is problematic in endemic areas because it causes high mortality in ruminants and leads to economic losses that threaten productivity and food security. This may indicate that there is augmented genetic diversity in the field, which may result in isolates that are more virulent than the Ball3 and Welgevonden isolates. The genetic diversity of E. ruminantium was investigated in this study, focussing on the pCS20 gene region and four polymorphic open reading frames (ORFs) identified by subtractive hybridisation. The 16S ribosomal ribonucleic acid gene confirmed E. ruminantium in brain, blood and tick genomic deoxyribonucleic acid samples (n = 3792) collected from 122 farms that were randomly selected from seven provinces of South Africa where heartwater is endemic. The conserved E. ruminantium pCS20 quantitative polymerase chain reaction (qPCR) assay was used to scan all collected field samples. A total of 433 samples tested positive with the qPCR using the pCS20 gene region, of which 167 were sequenced. The known stocks and field samples were analysed, and phylogenetic trees were generated from consensus sequences. A total of 25 new clades were identified; of these, nine isolates from infected blood could be propagated in cell cultures. These clades were not geographically confined to a certain area but were distributed amongst heartwater-endemic areas in South Africa. Thus, the knowledge of strain diversity of E. ruminantium is essential for control of heartwater and provides a basis for further vaccine development.

Investigation of Ixodidae ticks infesting camels at slaughterhouse and its potential role in transmitting Coxiella burnetii in Egypt

Coxiella burnetii is an important pathogen because of its wide host range, low infectious dose, stability in the environment, and capability for aerosol dispersion. The aim of this work was to investigate the potential role of hard ticks found on camels in transmitting Coxiella burnetii. A total number of adult hard ticks (n.370) were collected from 181 imported camels brought for slaughter in Cairo, Egypt, in which all examined camels were infested (100%). Ticks were identified using a stereomicroscope then screened for the presence of C. burnetii by PCR. Most camels were infested with Hyalomma dromedarii (n.171, 94.5 %) whereas other species were less prevalent, including Amblyomma hebraeum (n.19, 10.5 %), Rhipicephalus pulchellus (n.11, 6.1 %), H. anatolicum anatolicum (n.9, 5%), A. variegatum (n.8, 4.4 %) and A. gemma (n.4, 2.2 %). It is important to note that A. variegatum, A. gemma and R. pulchellus are rarely identified in Egypt, despite the higher prevalence in countries where camels came from. Four out of the six identified ixodid tick species yielded positive results for C. burnetii with an overall prevalence of 5.4 %, while prevalence of the other tick species was 6.6 %, 5.6 %, 5.3 % and 3.6 % for H. dromedarii, A. variegatum, H. anatolicum anatolicum and R. pulchellus respectively.The current study identified a wide array of hard tick species found on camels and highlights the potential role of such ticks in transmitting C. burnetii.

Amblyomma hebraeum is the predominant tick species on goats in the Mnisi Community Area of Mpumalanga Province South Africa and is co-infected with Ehrlichia ruminantium and Rickettsia africae

BackgroundIn sub-Saharan Africa, Amblyomma ticks are vectors of heartwater disease in domestic ruminants, caused by the rickettsial pathogen Ehrlichia ruminantium. Immature tick stages often bite humans, whereby they act as vectors of tick-bite fever caused by Rickettsia africae. Moreover, Amblyomma ticks cause damage to livestock due to their feeding behaviour. In South Africa, we studied the abundance of Amblyomma hebraeum ticks on goats of emerging farmers in Mpumalanga Province. A selected number of A. hebraeum nymphs and adult ticks was tested for co-infection with E. ruminantium and R. africae.MethodsA total of 630 indigenous goats, belonging to farmers in the Mnisi Community area, were examined for ticks in 2013 and 2014. All ticks were identified, and a selected number was tested by PCR with reverse line blot hybridisation.ResultsIn total, 13,132 ticks were collected from goats distributed over 17 different households. Amblyomma hebraeum was the predominant species, followed by R. microplus. Rhipicephalus appendiculatus, R. simus and R. zambeziensis were also identified. Amblyomma hebraeum was present throughout the year, with peak activity of adults in summer (November) and nymphs in winter (July). The ratio between adults and nymphs ranged from 1:2.7 in summer to 1:55.1 in winter. The mean prevalence of infection for E. ruminantium by PCR/RLB in adult ticks was 17.4% (31/178), whereas 15.7% (28/178) were infected with R. africae. In pooled nymphs, 28.4% were infected with E. ruminantium and 38.8% carried R. africae infection. Co-infections of E. ruminantium and R. africae in adult and pooled nymphal ticks were 3.9% (7/178) and 10% (14.9), respectively. Lameness of goats due to predilection of ticks for the interdigital space of their feet was observed in 89% of the households.ConclusionsGoats act as important alternative hosts for cattle ticks, which underscored the necessity to include goats in control programs. It is suggested to use acaricide-impregnated leg-bands as a sustainable method to kill ticks and prevent lameness in goats. The challenge of goats by considerable numbers of E. ruminantium-infected ticks is a major obstacle for upgrading the indigenous goat breeds. Humans may be at risk to contract tick-bite fever in this area.

The influence of host dispersal on the gene flow and genetic diversity of generalist and specialist ectoparasites

The dispersal and subsequent gene flow within parasite species is the result of a complex interaction between parasite life history, host life history and abiotic environmental factors. To gain more insights into the drivers responsible for parasite dispersal, COI mtDNA genetic data derived from six southern African generalist parasite species, including fleas, mites and ticks were compared with four specialist species from the same geographic region. Generalist tick species represented by Amblyomma hebraeum, Hyalomma truncatum and H. rufipes all occur temporarily on highly mobile ungulate hosts and showed high levels of haplotypic genetic diversity and high levels of dispersal with an average intraspecific global F st (population differentiation index) value of 0.27 (±0.13). Generalist parasites, such as fleas, Listropsylla agrippinae and Chiastopsylla rossi, and one mite species, Laelaps muricola, that are all semi-permanent on the host and restricted to less mobile hosts species, showed a similar high level of genetic diversity, but an intermediate average F st value of 0.67 (±0.11). Highly specialised semi-permanent parasites, such as the mite L. giganteus and the permanent lice Polyplax praomydis, Hoplopleura patersoni and P. arvicanthis recorded the lowest level of genetic diversity and a low level of gene flow among geographic sampling localities with an average F st value of 0.95 (±0.05). This study provides strong support for the Specialist Generalist Variation Hypothesis (SGVH) and highlights the role that host dispersal and host specialisation by parasites play in the dispersal and evolution of ectoparasites.

Phylogenetic profiling for zoonotic Ehrlichia spp. from ixodid ticks in the Eastern Cape, South Africa.

Ticks are obligate hematophagous parasite of vertebrate that transmit a range of pathogenic microorganisms that can cause diseases in livestock and humans. The range of tick-borne disease causative agents infecting domestic animals and humans has recently increased. Several significant zoonotic tick-borne diseases such as ehrlichiosis among others are on the increase worldwide. This study was designed to investigate the occurrence of zoonotic Ehrlichia spp. from samples collected from livestock in selected communities in the Eastern Cape Province, South Africa. Tick samples were manually collected from domesticated animals in selected homesteads. The ticks were morphologically identified to species and tested for Ehrlichia infection via polymerase chain reaction (PCR), using genus-specific disulphide bond formation protein (dsbA) gene primers. This was followed by sequence analysis of amplicons and phylogeny. Of the 1,200 ticks collected, Amblyomma hebraeum was most prevalent (n=335; 27.9%), followed by Rhipicephalus appendiculatus (n=274; 22.8%), Rhipicephalus decoloratus; (n=224; 18.7%) and Rhipicephalus eversti eversti (n=200, 16.7%). Ehrlichia DNA was detected in 19/1,200 (1.6%) of the screened DNA samples. A homology search of the generated sequences revealed a high percentage of identity between 95% and 98% with other homologous dsbA gene sequences of other Ehrlichia species in GenBank. Phylogenetic analysis showed that the obtained sequences clustered unambiguously with other Ehrlichia sequences from different geographical regions of the world. We concluded that Ehrlichial pathogens are vectored by the ticks collected from domesticated animals in the study areas, thus suggesting concern for public health, as some of the recovered pathogens are zoonotic in nature and could pose serious public health risk through human exposure to tick bites.

Scrotal tick damage as a cause of infertility in communal bulls in Moretele, South Africa.

Calving rate in communal cattle influences both food security and socio-economics in rural households. A previous study indicated that scrotal damage caused by ticks could affect the fertility of communal bulls and reduce the annual calving rate. The objectives of the study were to investigate the annual calving rate in communal herds by counting calves during herd visits, perform breeding soundness examinations on bulls and identify adult ticks attached to their genitalia. This prospective longitudinal survey was based on participatory rural appraisal. Calving rates were estimated in cows (n = 2398) from 100 randomly selected communal herds in Moretele over 12 months in 2013, during routine visits by animal health technicians. Randomly selected bulls (n = 50) from these herds were tested for Brucella abortus, Trichomonas foetus and Campylobacter fetus subspecies venerealis. The calving rate was 35.86% (0.359). The mean scrotal circumference was 37.63 ± 3.42 cm. Total sperm motility was 78.73 ± 35.73%; progressive sperm motility was 27.39 ± 15.81% and non-progressive sperm motility was 51.34 ± 19.92%. Thirty-five of the 38 bulls examined for breeding soundness exhibited severe scrotal and preputial lesions caused by the adult ticks Amblyomma hebraeum and Hyalomma rufipes. Tick control methods used included spraying (n = 20), pour-on (n = 11), no control (n = 1) and various (n = 18). It was concluded that in Moretele genital tick damage had a more serious impact on the fertility of communal bulls than contagious diseases. Targeted acaricidal spot treatment of the genitalia of communal bulls to prevent infestation is recommended, as tick control strategies used by farmers appeared to be inadequate.

Vitellogenin Receptor as a Target for Tick Control: A Mini-Review.

While much effort has been put into understanding vitellogenesis in insects and other organisms, much less is known of this process in ticks. There are several steps that facilitate yolk formation in developing oocytes of which the vitellogenin receptor (VgR) is a key component. The tick VgR binds vitellogenin (Vg) circulating in the hemolymph to initiate receptor-mediated endocytosis and its transformation into vitellin (Vn). The conversion of Vg into Vn, the final form of the yolk protein, occurs inside oocytes of the female tick ovary. Vn is critical to tick embryos since it serves as the nutritional source for their development, survival, and reproduction. Recent studies also suggest that pathogenic microbes, i.e., Babesia spp., that rely on ticks for propagation and dissemination likely “hitchhike” onto Vg molecules as they enter developing oocytes through the VgR. Suppressing VgR messenger RNA synthesis via RNA interference (RNAi) completely blocked Babesia spp. transmission into developing tick oocytes, thereby inhibiting vertical transmission of these pathogenic microbes from female to eggs. To date, VgRs from only four tick species, Dermacentor variabilis, Rhipicephalus microplus, Amblyomma hebraeum, and Haemaphysalis longicornis, have been fully sequenced and characterized. In contrast, many more VgRs have been described in various insect species. VgR is a critical component in egg formation and maturation that can serve as a precise target for tick control. However, additional research will help identify unique residues within the receptor that are specific to ticks or other arthropod disease vectors while avoiding cross-reactivity with non-target species. Detailed knowledge of the molecular structure and functional role of tick VgRs will enable development of novel vaccines to control ticks and tick-borne diseases.

Genetic characterization of tick-borne pathogens in ticks infesting cattle and sheep from three South African provinces

Ticks are involved in the transmission of many public health and veterinary important pathogens. Although tick-borne pathogens are widely distributed in South Africa, information on tick-pathogen relationship needs to be updated particularly using modern molecular techniques. This study used PCR and sequencing to confirm the identity of the tick species collected from cattle and sheep from KwaZulu-Natal, Free State and Eastern Cape. Furthermore, presence of Babesia spp., Theileria spp., Anaplasma marginale, Rickettsia spp., Ehrlichia ruminantium and Coxiella burnetii was detected from tick DNA using species-specific PCR or nested PCRs. The study samples consisted of 390 adult ticks (male and female) which were pooled according to species, host animal and sampling site (three ticks per pool) for DNA extraction. The PCR results revealed that out of 130 tick DNA pools, 30 (23.1%) were positive for at least one pathogen. The most frequent pathogen was C. burnetii (9.2%), followed by Rickettsia spp. (7.7%), A. marginale (3.8%), T. mutans (3.1%), T. taurotragi (2.3%) and E. ruminantium (1.5%). The highest prevalence of pathogens was observed in ticks collected from cattle in Eastern Cape (16/42) and the lowest was in ticks obtained from sheep in Free State (1/21). Infected ticks were identified as Rhipicephalus evertsi evertsi (n = 13), R. appendiculatus (n = 3), R. decoloratus (n = 7) and Amblyomma hebraeum (n = 7). Coinfection with two pathogens was found in 21% of pathogen-positive pools. Analysis of Theileria taurotragi 18S rRNA, T. mutans 18S rRNA, C. burnetii htpB, Rickettsia spp. gltA, Rickettsia spp. ompA, E. ruminantium pCS20 and A. marginale Msp5 sequences showed that the pathogens detected in this study were genetically related to isolates previously reported in Africa. These findings provide important information on distribution of ticks and tick-borne pathogens of ruminants and will contribute in the formulation of future control strategies in South Africa.

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.