Differential nested patterns of Anaplasma marginale and Coxiella-like endosymbiont across Rhipicephalus microplus ontogeny.

Understanding the intricate ecological interactions within the microbiome of arthropod vectors is crucial for elucidating disease transmission dynamics and developing effective control strategies. In this study, we investigated the ecological roles of Coxiella-like endosymbiont (CLE) and Anaplasma marginale across larval, nymphal, and adult stages of Rhipicephalus microplus. We hypothesized that CLE would show a stable, nested pattern reflecting co-evolution with the tick host, while A. marginale would exhibit a more dynamic, non-nested pattern influenced by environmental factors and host immune responses. Our findings revealed a stable, nested pattern characteristic of co-evolutionary mutualism for CLE, occurring in all developmental stages of the tick. Conversely, A. marginale exhibited variable occurrence but exerted significant influence on microbial community structure, challenging our initial hypotheses of its non-nested dynamics. Furthermore, in silico removal of both microbes from the co-occurrence networks altered network topology, underscoring their central roles in the R. microplus microbiome. Notably, competitive interactions between CLE and A. marginale were observed in nymphal network, potentially reflecting the impact of CLE on the pathogen transstadial-transmission. These findings shed light on the complex ecological dynamics within tick microbiomes and have implications for disease management strategies.

Efficacy of the Vaccine Candidate Based on the P0 Peptide against Dermacentor nitens and Ixodes ricinus Ticks.

The control of ticks through vaccination offers a sustainable alternative to the use of chemicals that cause contamination and the selection of resistant tick strains. However, only a limited number of anti-tick vaccines have reached commercial realization. In this sense, an antigen effective against different tick species is a desirable target for developing such vaccines. A peptide derived from the tick P0 protein (pP0) conjugated to a carrier protein has been demonstrated to be effective against the Rhipicephalus microplus, Rhipicephalus sanguineus, and Amblyomma mixtum tick species. The aim of this work was to assess the efficacy of this peptide when conjugated to the Bm86 protein against Dermacentor nitens and Ixodes ricinus ticks. An RNAi experiment using P0 dsRNA from I. ricinus showed a dramatic reduction in the feeding of injected female ticks on guinea pigs. In the follow-up vaccination experiments, rabbits were immunized with the pP0-Bm86 conjugate and challenged simultaneously with larvae, nymphs, and the adults of I. ricinus ticks. In the same way, horses were immunized with the pP0-Bm86 conjugate and challenged with D. nitens larva. The pP0-Bm86 conjugate showed efficacies of 63% and 55% against I. ricinus and D. nitens ticks, respectively. These results, combined with previous reports of efficacy for this conjugate, show the promising potential for its development as a broad-spectrum anti-tick vaccine.

Morphological and molecular characterization supporting Amblyomma mixtum presence in Cuba.

Amblyomma cajennense Fabricius, 1787 (Acari: Ixodidae) is a widely distributed tick taxon. Recent studies have reassessed this taxon as a complex of six species. Amblyomma mixtum Koch, 1844 has been suggested by some authors as the only species of this complex that is present in Cuba. Other authors have pointed a niche overlapping for A. mixtum and A. cajennense s.s. in the country. Detailed taxonomic studies on the Cuban species belonging to this complex are needed in order to evaluate their current distribution according to the recent classification. This study aimed to characterize Cuban populations from the A. cajennense complex by using tick samples obtained from 3 occidental provinces and 1 central province of the country. Morphological identification and measurements of the main relevant taxonomic structures were conducted by using Scanning Electron Microscopy. Phylogenetic analyzes were carried out with 16S ribosomal RNA, internal transcribed spacer 2 and the subunit I of mitochondrial cytochrome c oxidase gene sequences. The results of these studies demonstrated that all samples belonged to the species A. mixtum (Koch, 1844). This study constitutes the first molecular characterization of this Amblyomma species in Cuba. Further studies will be necessary in order to corroborate if A. cajennense s.s. is also present in the island.

High efficacy of a 20 amino acid peptide of the acidic ribosomal protein P0 against the cattle tick, Rhipicephalus microplus.

Current strategies to control cattle ticks use integrated control programs (ICP) that include vaccination. Reduction in the use of chemicals and in the cost of tick control, the delay or elimination of acaricide resistance and the decreasing of environmental pollution are the advantages of using these programs. This integrated program is potentially applicable to all genotypes of chemical resistant ticks. However, the problem here is to improve the efficacy of anti-tick vaccines. The P0 protein is a structural component of the ribosome of all organisms. We have identified an immunogenic region of ribosomal protein P0 from Rhipicephalus spp. ticks that is not very conserved compared to the orthologous protein in their hosts. A synthetic 20 amino acid peptide from this sequence was effective as a vaccine against Rhipicephalus sanguineus infestations in an immunization and challenge experiment using rabbits. In this paper, the same peptide used as vaccine against the cattle tick Rhipicephalus Boophilus microplus shows a significant diminution in the number of engorged females recovered, in the weight of females and the weight of egg masses. The number of eggs hatched was also significantly reduced for the vaccinated group, with an overall effectivity for the antigen pP0 of 96%. These results, together with the conserved sequence of the P0 peptide among ticks, suggest that this antigen could be a good broad spectrum vaccine candidate. It would be expected to be active against many species of ticks and thus has promise in an ICP for effective control of ticks and thereby to improve the efficiency and productivity of the livestock industry.

A novel tick antigen shows high vaccine efficacy against the dog tick, Rhipicephalus sanguineus.

Ticks are acaridae ectoparasites that, while taking a blood meal, can transmit viruses, bacteria, protozoa and filarial nematodes, which cause a variety of human and animal illnesses. The use of chemical pesticides constitutes the primary measure for control of these ectoparasites. However, the intensive use of these chemicals has drawbacks such as the contamination of food, environmental pollution and development of resistance by ectoparasites. Vaccination is considered a promising alternative for controlling infestations by ectoparasites. Although emerging tick proteins have been identified recently, and have been proposed as potential targets for generating protective molecules, only a limited number of them have been evaluated in vaccine trials. More than 80 proteins are found in eukaryotic ribosomes. The protein P0 is essential for the assembly of the 60S ribosomal subunit. We have identified an immunogenic region of the ribosomal protein P0 from Rhipicephalus sp. ticks that is not very conserved compared to host P0. The efficacy of a 20 amino acid synthetic peptide from this sequence was assayed as a vaccine antigen against Rhipicephalus sanguineus infestations in an immunization and challenge experiment on rabbits. A remarkable diminution in the viability of newly molted nymphs from larvae fed on vaccinated rabbits was observed. The number of adults and the number of eggs hatching were significantly reduced, with an overall efficacy of 90%. Our results demonstrated that immunization with an immunogenic peptide of tick protein P0 greatly reduced survival of ticks, suggesting that it has promise as an effective tick control agent.