Inclusion of Anti-Tick Vaccines into an Integrated Tick Management Program in Mexico: A Public Policy Challenge.

Acaricides are the most widely used method to control the cattle tick Rhipicephalus microplus. However, its use increases production costs, contaminates food and the environment, and directly affects animal and human health. The intensive use of chemical control has resulted in the selection of genes associated with resistance to acaricides, and consumers are increasingly less tolerant of food contamination. This scenario has increased the interest of different research groups around the world for anti-tick vaccine development, in order to reduce the environmental impact, the presence of residues in food, and the harmful effects on animal and human health. There is enough evidence that vaccination with tick antigens induces protection against tick infestations, reducing tick populations and acaricide treatments. Despite the need for an anti-tick vaccine in Mexico, vaccination against ticks has been limited to one vaccine that is used in some regions. The aim of this review is to contribute to the discussion on tick control issues and provide a reference for readers interested in the importance of using anti-tick vaccines encouraging concerted action on the part of Mexican animal health authorities, livestock organizations, cattle producers, and academics. Therefore, it is suggested that an anti-tick vaccine should be included as a part of an integrated tick management program in Mexico.

A One Health Epidemiological Approach for Understanding Ticks and Tick-Borne Pathogens.

Background: The control and prevention of ticks and tick borne diseases (TBDs) is often difficult, since it is necessary to disrupt a complex transmission cycle, involving ticks and vertebrate hosts, which interact in a changing environment, driven by constant environmental and ecological changes. Our view is that factors driving the spread of R. microplus are complex and intrinsically interconnected, something that has often been ignored in control strategies. Results: The aim of this review is to analyze the importance of the epidemiological surveillance of ticks and tick-borne diseases (TTBDs) for Public Health, with the One Health approach; emphasizing the knowledge, importance, and distribution of TTBDs. Conclusions: The key points for surveillance, and raising the scope and limitations of surveillance programs, to delay the emergence of acaricide resistance, to reduce toxic residues in food for human consumption and to protect animal, human, and environmental health, from a One Health perspective will require calling producers, veterinarians, academics, pharmaceutical industry, and decision makers to join efforts in order to mitigate the effects of ticks and TBDs affecting the cattle industry in Mexico.

Identification of immunogenic proteins from ovarian tissue and recognized in larval extracts of Rhipicephalus (Boophilus) microplus, through an immunoproteomic approach.

Rhipicephalus (Boophilus) microplus ticks are obligatory hematophagous ectoparasites of cattle and act as vectors for disease-causing microorganisms. Conventional tick control is based on the use of chemical acaricides; however, their uncontrolled use has increased tSresistant tick populations, as well as food and environmental contamination. Alternative immunological tick control has shown to be partially effective. The only anti-tick vaccine commercially available at present in the world is based on intestinal Bm86 protein, and shows a variable effectiveness depending on tick strains or geographic isolates. Therefore, there is a need to characterize new antigens in order to improve immunological protection. The aim of this work was to identify immunogenic proteins from ovarian tissue extracts of R. microplus, after cattle immunization. Results showed that ovarian proteins complexed with the adjuvant Montanide ISA 50 V generated a strong humoral response on vaccinated cattle. IgG levels peaked at fourth post-immunization week and remained high until the end of the experiment. 1D and 2D SDS-PAGE-Western blot assays with sera from immunized cattle recognized several ovarian proteins. Reactive bands were cut and analyzed by LC-MS/MS. They were identified as Vitellogenin, Vitellogenin-2 precursor and Yolk Cathepsin. Our findings along with bioinformatic analysis indicate that R. microplus has several Vitellogenin members, which are proteolytically processed to generate multiple polypeptide fragments. This apparent complexity of vitellogenic tick molecular targets gives the opportunity to explore their potential usefulness as vaccine candidates but, at the same time, imposes a challenge on the selection of the appropriate set of antigens.

Molecular survey of pyrethroid resistance mechanisms in Mexican field populations of Rhipicephalus (Boophilus) microplus.

Susceptibility to synthetic pyrethroids (SP s) and the role of two major resistance mechanisms were evaluated in Mexican Rhipicephalus microplus tick populations. Larval packet test (LPT), knock-down (kdr) PCR allele-specific assay (PASA) and esterase activity assays were conducted in tick populations for cypermethrin, flumethrin and deltamethrin. Esterase activity did not have a significant correlation with SP s resistance. However a significant correlation (p < 0.01) was found between the presence of the sodium channel mutation, and resistance to SP s as measured by PASA and LPT respectively. Just over half the populations (16/28) were cross-resistant to flumethrin, deltamethrin and cypermethrine, 21.4% of the samples (6/28) were susceptible to all of the three pyrethroids 10.7 of the samples (3/28) were resistant to flumethrin, 3.4 of the samples (1/28) were resistant to deltamethrin only and 7.1% (2/28) were resistant to flumethrin and deltamethrin. The presence of the kdr mutation correlates with resistance to the SP s as a class. Target site insensitivity is the major mechanism of resistance to SP s in Mexican R. microplus field strains, involving the presence of a sodium channel mutation, however, esterase-based, other mutations or combination of mechanisms can also occur.

Genetic basis and impact of tick acaricide resistance.

Acaricide resistance in Boophilus microplus has been studied for the last 20 years from the toxicology, metabolic and genomic points of view, however, only few methods for molecular detection of resistance have been developed. Despite the relatively poor sensitivity for resistance detection, bioassays remain the method of choice for susceptibility evaluation of tick populations, based on their toxicological response after exposure to acaricides. Metabolic detoxification of acaricides is known to be mediated by multigene- families of enzymes such as GST, Esterases and Mixed Function Oxidases (cytochrome P450). In addition, target site insensitivity has been studied on the sodium channel and acetylcholinesterase genes. The use of genomics to understand acaricide resistance in B. microplus will play a major role in unraveling the molecular mechanisms of resistance. Advances in genomics, will accelerate the development of new diagnostic and immunoprophylactic tools based on new vaccine candidates, and new molecular targets for acaricide resistance detection and improvement of strategies for the control of ticks and tick-borne diseases in tropical and subtropical areas of Mexico.