PARTICIPATION OF TICKS IN THE INFECTIOUS CYCLE OF CANINE VISCERAL LEISHMANIASIS,IN TERESINA,PIAUí, BRAZIL

In this study, we detected Leishmania spp. infection in R. sanguineus collected from dogs that were naturally infected with L. (L.) infantum. We examined 35 dogs of both sexes and unknown ages. The infected dogs were serologically positive by the immunofluorescence antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA), and Quick Test-DPP (Dual Path Platform), as well as parasitological examination of a positive skin biopsy or sternal bone marrow aspiration. Ten negative dogs were included as controls. The ticks that infested these dogs were collected in pools of 10 adult females per animal. The PCR was performed with specific primers for Leishmania spp., which amplified a 720-bp fragment. Of the 35 analyzed samples, a product was observed in eight samples (8/35; 22.9%). We conclude that the presence of parasite DNA suggests that ticks participate in the zoonotic cycle of canine visceral leishmaniasis, in the city of Teresina, Piauí.     

Efficacy of Hyalomma scupense (Hd86) antigen against Hyalomma excavatum and H. scupense tick infestations in cattle

The Rhipicephalus microplus recombinant Bm86-based tick vaccines have shown their efficacy for the control of several Hyalomma cattle ticks genera, namely H. dromedarii and H. anatolicum. However, H. scupense species, the most important tick in North Africa has never been studied. Vaccination trials using either a recombinant Bm86-based vaccine or a recombinant Hd86-based vaccine (the Bm86 ortholog in H. scupense) were conducted in cattle against immature and adult H. scupense ticks and adult H. excavatum ticks. The results showed a 59.19% reduction in the number of scupense nymphs engorging on Hd86 vaccinated cattle. However, cattle vaccination with Bm86 or Hd86 did not have an effect on H. scupense or H. excavatum adult ticks infestations. These results showed that Hd86 vaccines are selectively effective against H. scupense immature instars and emphasize on an integrated anti-tick vaccine control in North Africa.     

Peripheral cellular and humoral responses to infestation with the cattle tick Rhipicephalus microplus in Santa Gertrudis cattle

Resistance to cattle tick infestation in single‐host ticks is primarily manifested against the larval stage and results in the immature tick failing to attach successfully and obtain a meal. This study was conducted to identify immune responses that characterize the tick‐resistant phenotype in cattle. Thirty‐five tick‐naïve Santa Gertrudis heifers were used in this study, thirty of which were artificially infested for thirteen weeks with tick larvae while five animals remained at a tick‐free quarantine property to serve as a control group. Following thirteen weeks of tick infestation, the animals in this trial exhibited highly divergent tick‐resistant phenotypes. Blood samples collected throughout the trial were used to measure peripheral immune parameters: haematology, the percentage of cellular subsets comprising the peripheral blood mononuclear cell (PBMC) population, tick‐specific IgG₁ and IgG₂ antibody titres, IgG1 avidity for tick antigens and the ability of PBMC to recognize and proliferate in response to stimulation with tick antigens in vitro. The tick‐susceptible cattle developed significantly higher tick‐specific IgG₁ antibody titres compared to the tick‐resistant animals. These results suggest that the heightened antibody response either does not play a role in resistance or might contribute to increased susceptibility to infestation.     

Local immune response to larvae of Rhipicephalus microplus in Santa Gertrudis cattle

This study investigated the local immune response at larval attachment sites in Santa Gertrudis cattle with low and high levels of tick resistance. Skin samples with tick larvae attached were collected from Santa Gertrudis cattle at the end of a period of 25 weekly infestations, when the animals manifested highly divergent tick‐resistant phenotypes. There was a tendency for more CD3⁺, CD4⁺, CD8⁺, CD25⁺, γδ T cells and neutrophils to concentrate at larval tick attachment site in susceptible cattle than in resistant cattle but the differences were significant only for γδ T cells and CD4⁺ cells. Most of the cattle developed intra‐epidermal vesicles at the larval attachment site but the predominant cell within or around the vesicles was the neutrophil in susceptible animals and eosinophil in the resistant animals. The monoclonal antibodies (mAbs) specific for CD45 and CD45 RO antigens reacted with skin leucocytes from a higher number of susceptible cattle than resistant cattle. Our data suggest that some of the cellular responses mounted at larval attachment site are not involved in tick protection. The mAbs specific for CD45 and CD45 RO directly, or a test for CD45 genotype might be developed as markers of tick susceptibility or resistance.     

Serial analysis of gene expression in the southern cattle tick following acaricide treatment of larvae from organophosphate resistant and susceptible strains

Organophosphate resistant and susceptible tick larvae from laboratory strains of the southern cattle tick, Rhipicephalus (Boophilus) microplus were exposed to low doses of the organophosphate (OP) acaricide, coumaphos. Serial analysis of gene expression (SAGE) was used to analyse differential gene expression in response to OP treatment and to compare the responses of OP-treated and -untreated resistant and susceptible tick larvae. An R. microplus Gene Index was used as an EST database to identify genes which corresponded to SAGE tags whose abundance changed in response to acaricide exposure. Relative quantitative RT-PCR was used to confirm the differential expression results from the SAGE experiments. Of particular interest is a SAGE tag which corresponds to a cytochrome P450-like EST in the Gene Index which was more abundant in untreated OP resistant larvae compared to untreated OP susceptible larvae. This SAGE tag was also more abundant in OP resistant larvae treated with OP compared to OP susceptible larvae treated with OP.     

Cloning and characterization of Rhipicephalus appendiculatus voraxinα and its effect as anti-tick vaccine

Male tick-derived voraxinα and voraxinβ, a pair of testicular proteins, are transferred to female via copulation to stimulate female blood feeding in the tick Amblyomma hebraeum (A. hebraeum). Immunized animals with recombinant (r-)voraxinα and voraxinβ have been shown as highly resistant to the tick infestation. In this study, we describe the cloning and characterization of voraxinα homologue from the tick Rhipicephalus appendiculatus (R. appendiculatus), the major vector for East Coast fever in Eastern Africa. The sequence analysis of the R. appendiculatus voraxinα indicated that the deduced amino acid sequence had high similarity with voraxinα of the tick A. hebraeum and Dermacentor variabilis, suggesting that voraxinα is conserved in different tick genera. Quantitative RT-PCR and Western blotting analysis showed that male voraxinα was predominantly expressed in testis and its expression was induced by blood feeding. R. appendiculatus voraxinα was not secreted into the host during tick feeding and was detected in mated female hemolymph as measured by Western blotting. Preliminary vaccination of rabbits with r-voraxinα elicited the humoral immunity and conferred protective immunity against female ticks, resulting in the reduced fed weight. These results suggest that r-voraxinα could be a good candidate as anti-tick vaccine.     

Genetic analysis of ticks belonging to the Rhipicephalus sanguineus group in Latin America

Phylogenetic analyses based on mitochondrial 16S rDNA sequences were generated from Rhipicephalus sanguineus group specimens collected in 29 localities among 9 Latin-American countries, plus ticks collected in South Africa, Spain, and Italy. Sequences from Latin America generated six different haplotypes (A, B, C, D, E, and F). Phylogenetic analyses generated trees that segregated our tick sequences into two distinct clades: one is represented by haplotypes A–C, and South African R. sanguineus and Rhipicephalus turanicus ticks; the second clade is represented by haplotypes D–F, and European R. sanguineus and R. turanicus ticks. When haplotypes A–F are plotted in the Latin America map according to their geographical coordinates, it is clearly seen that haplotypes D–F are restricted to the southern portion of this continent, whereas haplotypes A–C are distributed in areas between northern Mexico and Brazil (except for the extreme south of this last country, where haplotype E was present). Hence, our phylogenetic analyses separated New World specimens of R. sanguineus into two distinct clades, one represented by tropical and subtropical populations (haplotypes A–C), here designated as the ‘tropical’ species. On the other hand, haplotypes D–F are here designated as the ‘temperate’ species because of their distribution in the southern portion of South America. Until recently, it was assumed that the R. sanguineus group was represented by a single species in the New World, namely R. sanguineus. While the present results coupled with recent studies support the presence of at least two species under the taxon R. sanguineus in the New World, they also show that even in the Old World, the taxon R. sanguineus might be represented by more than one species, since our phylogenetic analysis segregated European and South African R. sanguineus ticks into two distinct clades. The same can be applied for Spanish and South African R. turanicus.     

Bovine anaplasmosis and tick‐borne pathogens in cattle of the Galapagos Islands

A cross‐sectional study was conducted to determine the species of Anaplasma spp. and estimate its prevalence in cattle of the three main cattle‐producing Galapagos Islands (Santa Cruz, San Cristóbal and Isabela) using indirect PCR assays, genetic sequencing and ELISA . Ticks were also collected from cattle and scanned for 47 tick‐borne pathogens in a 48 × 48 real‐time PCR chip. A mixed effects logistic regression was performed to identify potential risk factors explaining Anaplasma infection in cattle. A. phagocytophilum was not detected in any of the tested animals. Genetic sequencing allowed detection of A. platys ‐like strains in 11 (36.7%) of the 30 Anaplasma spp.‐positive samples analysed. A. marginale was widespread in the three islands with a global between‐herd prevalence of 100% [89; 100]_95%CI and a median within‐herd prevalence of 93%. A significant association was found between A. marginale infection and age with higher odds of being positive for adults (OR = 3.3 [1.2; 9.9]_{95% Bootstrap CI} ). All collected ticks were identified as Rhipicephalus microplus. A. marginale , Babesia bigemina , Borrelia theileri and Francisella ‐like endosymbiont were detected in tick pools. These results show that the Galapagos Islands are endemic for A. marginale .     

The Emergence of Theileria parva in Jonglei State,South Sudan: Confirmation Using Molecular and Serological Diagnostic Tools

A cross‐sectional survey was carried out in four counties of Jonglei State, South Sudan, between May and June 2012 to determine the distribution and northern limit of Theileria parva, the causative agent of East Coast fever in cattle, and its tick vector Rhipicephalus appendiculatus, as a prerequisite to the deployment of relevant control strategies. A total of 1636 ticks, 386 serum samples and 399 blood samples were collected from indigenous, apparently healthy, cattle of different age groups. Tick species were identified morphologically, and the identity of R. appendiculatus was confirmed by DNA barcoding. Overall, the T. parva infection rate in R. appendiculatus was 25% as shown by nested PCR. ELISA was used to assess antibodies to T. parva, and the overall seroprevalence was 22.8%. PCR of the blood samples showed 55 (13.8%) were positive for T. parva. This is the first molecular confirmation of T. parva DNA in areas north of Juba, where it was previously known and established. The northern limit of T. parva was determined as N⁰06.17.792, about 242 Km north from Juba. Implication of this limit on the epidemiology and control of ECF is discussed.