Worldwide comparison between the potential distribution of Rhipicephalus microplus (Acari: Ixodidae) under climate change scenarios

Tick-borne pathogens from ruminant ticks in a Mediterranean ecosystem from Eastern Spain

Vector-borne diseases represent various sicknesses that are increasingly significant in human and veterinary health. Among the zoonotic agents transmitted by ticks, infections caused by the intracellular pathogens from the Anaplasmataceae family and piroplasmids (Babesia/Theileria spp.) are particularly notable due to the substantial economic losses they cause in the livestock sector. A study was carried out to assess the prevalence of these pathogens in ticks from ruminants in the province of Valencia (Eastern Iberian Peninsula). Between 2019 and 2022, 1674 ticks were collected from 163 domestic and wild ruminants. The tick species were identified using molecular and morphological features and included Rhipicephalus spp. (Rhipicephalus bursa and Rhipicephalus sanguineus) (88.7%), Haemaphysalis sulcata (5.9%), Ixodes ricinus (3.6%) and Dermacentor marginatum (1.2%). The Spanish ibex (Capra pyrenaica) was found to be at greater risk of infestation by Haemaphysalis compared to other ruminants. Polimerase Chain Reaction (PCR) analysis was performed on 108 individual ticks from different hosts, with 16.7% testing positive for members of the Anaplasmataceae family and 39.8% for Theileria spp. Sequencing of 10 positive samples from each pathogen group revealed the presence of Anaplasma ovis, Anaplasma platys, Ehrlichia spp., Theileria ovis and Theileria capreoli. No Anaplasma phagocytophilum or Babesia spp. were detected. Further research is essential for improved management of ticks and the diseases they transmit in the study area.

Nanocarriers of natural and synthetic ixodicides, new alternatives against Rhipicephalus microplus (Acari: Ixodidae): A review

In many countries, economic activities such as agriculture and livestock farming are fundamental pillars of the economy. However, the cattle tick Rhipicephalus microplus poses a serious threat to livestock production systems, leading to significant economic losses. The most employed control method is the use of chemical ixodicides; nonetheless, their application is associated with several drawbacks, including environmental pollution, risks to human and animal health, and the development of resistant tick populations. These issues highlight the urgent need for sustainable, low-impact alternatives that can effectively mitigate resistance. Natural products have been extensively studied for their ixodicidal properties, as they interfere with various biological processes in ticks. Despite their potential, the practical application of these compounds faces several limitations. In this context, nanotechnology has emerged as a promising approach for the control of R. microplus, particularly using nanocarriers to deliver both natural compounds and synthetic ixodicidal agents. The use of polymeric nanoparticles (NPs), lipid-based NPs, and nanoemulsions as controlled-release systems offer several advantages. These include maintaining ixodicidal efficacy at lower concentrations, enhancing the stability and bioavailability of active compounds, and improving their penetration across biological barriers. As a result, nanocarrier-based delivery systems can increase treatment effectiveness while minimizing adverse effects. This review explores the current findings on the use of nanocarriers for delivering natural and synthetic ixodicidals against R. microplus, emphasizing their interactions, mechanisms of action, and effectiveness. Furthermore, it discusses the main challenges and future perspectives in this innovative and rapidly evolving field.

Metarhizium anisopliae and diatomaceous earth for the control of Rhipicephalus microplus ticks: laboratory and field trials

The aim of this research was to assess the efficacy of Metarhizium anisopliae (Ma) and diatomaceous earth (De), both individually and in combination, for the control of Rhipicephalus microplus ticks under laboratory and field conditions. In vitro experiments involved testing four concentrations of Ma (25%, 50%, 75%, and 100%), four concentrations of De (25%, 50%, 75%, and 100%), and three combination treatments (Ma25De75, Ma50De50, Ma75De25), alongside a control treatment of sterile distilled water with 0.1% (v/v) Tween 80, to evaluate their impact on R. microplus larvae. Laboratory trial results demonstrated that the application of Ma at 25% and 50%, as well as De at all concentrations, and the three combination treatments, led to a larval mortality exceeding 97% over a seven-day period. In contrast, individual treatments with Ma100 and Ma75 resulted in approximately 50% larval mortality. Subsequent field evaluations focused on Ma25De75 and Ma50De50 treatments for adult tick control. The application of Ma25De75 and Ma50De50 exhibited progressive increases in efficacy, reaching 97% and 88%, respectively, 21 days post-application. After the second application, efficacy further improved to 100% and 94.8% for Ma25De75 and Ma50De50, respectively. In conclusion, Ma25 and Ma50, along with all concentrations of De, proved to be effective options for controlling R. microplus larvae. Furthermore, a potential synergistic effect between M. anisopliae conidia and De was observed, demonstrating high efficacy rates of 100% in vitro for larvae and 88% to 100% in the field for adult R. microplus tick control.

A reverse vaccinology approach identified novel recombinant tick proteins with protective efficacy against Rhipicephalus microplus infestation

The cattle tick, Rhipicephalus microplus, causes significant economic losses to the cattle industry. Tick control is predominately achieved via pesticide applications. However, alternative control methods such as vaccines are needed due to the tick's capacity to quickly develop pesticide resistance and to combat tick-borne diseases. We used an in silico reverse vaccinology approach to evaluate and rank open reading frames (ORFs) from the tick's transcriptome for their potential use as anti-R. microplus vaccine antigens. We manually annotated the 200 highest ranked antigens and selected 10 transcript ORFs as vaccine antigen candidates for expression in Pichia pastoris or insect cells. Six of the ten candidate antigens could be successfully expressed and purified in vitro as recombinant proteins with > 1 mg quantity. RT-PCR confirmed the expression of all six transcripts in tick RNA. However, only three of the six transcripts' corresponding ORFs could be confirmed as present in tick tissue protein extracts. Only four of the six vaccine candidate antigens were successfully expressed and purified in sufficient quantity (> 10 mg) for immunogenicity and efficacy trials in cattle. These four were designated BI-TS002, BI-TS004, BI-TS008, and BI-TS009 and sufficient annotation existed that showed sequence similarity to serine‑rich adhesin for platelets, glycine-rich cell wall structural membrane protein, SWM-1 tick serine protease inhibitor, and venom-like dermonecrotic toxins from ticks and spiders, respectively. Cattle immunized with BI-TS004, BI-TS008 and BI-TS009 yielded a statistically significant difference in antibody response post-immunization. This difference was noted on Days 42, 56, 70, and 84 post-immunization for BI-TS008 and BI-TS009, but only on Day 56 for BI-TS004. BI-TS008 and BI-TS009, were formulated with adjuvant and cattle stall tests conducted over a 175 day period to evaluate efficacy against R. microplus infestations. Both an adjuvant only negative control group and a positive control group using the commercially available GAVAC anti-tick vaccine were used. Efficacy was determined by comparing number of engorged adult female ticks, total egg mass weight, and egg hatchability produced from the immunized group to corresponding data from the adjuvant only negative control group. Thus, effects on engorged adult tick number, reproductive capacity, and fertility were measured. Both initial (designated Phase 1 and calculated from tick collections of Days 60-94 days post-first immunization) and long-term (designated Phase 2 and calculated from tick collections of Days 152-175 post-first immunization) efficacies were determined. The overall Phase 1 trial efficacies of BI-TS008, BI-TS009, and GAVAC were 68.3 %, 48.5 %, and 70.7 %, respectively. The overall Phase 2 trial efficacies of BI-TS008, BI-TS009, and GAVAC were 64.4 %, -30.1 %, and 45.1 %, respectively.

Effect of an altitudinal gradient on the morphology, molecular identification and distribution of Rhipicephalus linnaei in Veracruz, Mexico

Studies of morphological and genetic variation in vector populations across environmental gradients can help researchers to estimate species' responses to climate change scenarios and the potential risk of disease-causing pathogen expansion, which impacts negatively on human health. In this study, we analysed the effect of altitudinal gradients on the phenotypic response of the hard tick of medical and veterinary importance, Rhipicephalus sanguineus sensu lato (s.l.). Specimens of R. sanguineus s.l. were collected from host animals in one of Mexico's regions with high climatic heterogeneity (Veracruz), and geometric morphometric theory was employed to assess the response of three morphological characters to the altitudinal gradient. Additionally, genetic similarity data were provided, and ecological niche models were used to project the climatic distribution in the region. Our results demonstrate that the shape and size of ticks respond to altitude. Molecular identification indicate that all analysed samples correspond to the tropical lineage recently named Rhipicephalus linnaei. According to ecological niche models, the mean annual temperature contributes significantly to the spatial distribution of this tick species, with areas of higher suitability in the mountainous region. These changes in morphological structure and the presence of ticks at higher altitudinal gradients suggest that R. linnaei has a high potential for adaptation. Due to the variability of ecosystems in the state of Veracruz, our results could be valuable in assessing the response of this tick in a changing environment, aiding in predicting future scenarios in the distribution and abundance of this species.