Biological and Biochemical Bases of Pesticides Resistance in Rhipicephalus (Boophilus) microplus

Several arthropod species are important vectors of pathogens that cause disease in humans, animals, and plants, including protozoa, nematodes, bacteria, and viruses. Arthropods are also pests competing with humans for food and parasitize farm animals, decreasing their productivity. Historically, arthropod pests and disease vectors affecting public health, crop yields, and livestock production have been managed through the intensive use of pesticides. The widespread use of pesticides is a major problem because most of the economically important arthropod species have developed resistance to currently used pesticides. The impact of pesticide resistance is multifactorial and involves losses due to the heavy use of pesticides, environmental pollution, decreased profitability, food contamination, and public health problems due to pesticide exposure. An indirect consequence of pesticide resistance is the mortality caused by arthropod-borne diseases such as dengue and malaria in humans and babesiosis and anaplasmosis in cattle. The understanding of molecular mechanisms and adaptations to resistance in arthropods is an important issue. However, the molecular mechanisms of pesticide resistance remain to be fully understood. Understanding of resistance mechanisms will contribute significantly to improve integrated managements programs and to discover new targets for vaccine development to mitigate the effects of pesticide-resistant arthropods on agriculture and public health

Integrated Management of the Cattle Tick <em>Rhipicephalus (Boophilus) microplus</em> (Acari: Ixodidae) and the Acaricide Resistance Mitigation

Resistance to insecticides is one of the major obstacles to the control of agricultural pests, as well as species important to human and veterinary health. The World Health Organization has called insecticide resistance “the great little obstacle against vector-borne diseases”. Rhipicephalus (Boophilus) microplus is one of the most important vector, transmitting diseases to cattle such as anaplasmosis and babesiosis. These diseases cause great economic losses that significantly increased because of the appearance of tick populations resistant to acaricides, as a result of the intensive use of pesticides. Resistance to ixodicides in Latin America is a growing problem, since control of disease-transmitting ticks, depends heavily on the use of pesticides. In Mexico, the resistance of R. microplus to organophosphate compounds, pyrethroids, and recently amidines, has been detected in some areas, affected by multiple acaricide resistance to the three families of ixodicides. The cattle tick R. microplus in addition to the great ecological impact represents the most expensive pest for livestock in Mexico, since the producers are directly affected by this tick, due to the decrease in the production of meat, milk and damage to the skin, as well as the indirect damage, such as the transmission of diseases, including Anaplasmosis and Babesiosis, which, in turn, represents a serious limitation for the introduction of specialized cattle in endemic areas. Therefore, the use of integrated management programs is a mandatory issue that should be implemented in all those areas affected by this parasite

Boophilus microplus: biological and molecular aspects of acaricide resistance and their impact on animal health

[ES]: La aplicación de ixodicidas durante mucho tiempo ha sido la alternativa de elección para el control de la garrapata Boophilus microplus, sin embargo, actualmente el uso de los ixodicidas tiene una eficacia limitada en la reducción de las infestaciones debido al desarrollo de poblaciones de garrapatas resistes. La resistencia a ixodicidas es un problema creciente que necesita ser atendido, por que en este momento está afectando la competitividad de la ganadería y la economía de miles de productores en México. La solución de este problema requiere de la implementación de programas de investigación que coadyuven a dilucidar los mecanismos moleculares de la resistencia con el fin de encontrar nuevos blancos moleculares para el diagnóstico y para el desarrollo de vacunas recombinantes. El uso reciente de nuevas herramientas genómicas y los enfoques de genética reversa, son una extraordinaria herramienta que podría ayudar en el descubrimiento de nuevos genes de interés diagnóstico ó imunoprofiláctico, contribuyendo así al mejoramiento de las estrategias de control de garrapatas y los programas de mitigación de la resistencia a ixodicidas. El propósito de esta revisión es compilar diferentes tópicos actuales relacionados con la biología de las garrapatas, resistencia a los ixodicidas, y las perspectivas de la investigación genómica en la garrapata Boophilus microplus, iniciando con algunas consideraciones biológicas y moleculares acerca de la nueva clasificación de este ectoparásito, hasta el análisis de la resistencia a los ixodicidas, su impacto en la industria ganadera en México y la aplicación de la genómica en la solución de problemas asociados con el control de las garrapatas mediante el diseño de nuevos métodos diagnósticos así como el desarrollo de vacunas contra garrapatas.[EN]: The application of Ixodicides has been considered for a long time the alternative for control of the cattle tick Boophilus microplus, however, its use is currently limited in reducing tick infestations, due to the appearance of resistant field tick populations. Ixodicide resistance is a growing problem that needs to be attended, because, it is currently affecting the competitiveness of the Mexican cattle industry in general and in particular the income of cattle producers. The solution to this problem needs to increase the budget dedicated to basic research in order to elucidate the molecular mechanisms of ixodicide resistance leading to the discovery of new molecular targets for ixodicide resistance detection and recombinant vaccine development. The recent use of new genomic tools, as well as reverse genetics approaches, will provide an extraordinary contribution to the improvement of tick control strategies and ixodicide resistance mitigation programs. The aim of the present review is to make a compilation of different topics related with acaricide resistance in the cattle tick Boophilus microplus, starting with some biological and molecular considerations on its new classification, to the analysis of ixodicide resistance, its impact on the Mexican cattle industry and the perspective of the genomic research in order to solve the problems associated to tick control, new diagnostic tools and development of tick vaccines.Al Consejo Nacional de Ciencia y Tecnología por la beca otorgada a la MC Delia Inés Domínguez García inscrita en el programa doctoral de Ciencias Biológicas y de la Salud de la Universidad Autónoma Metropolitana. Este trabajo fue parcialmente financiado por el proyecto 90195 del programa de CONACYT de apoyos complementarios otorgado a Dr. Rodrigo Rosario Cruz.Peer Reviewe

Evaluación post-vacunal de la población de garrapatas Rhipicephalus (Boophilus) microplus en un rancho de Iguala Guerrero, México

El estudio se llevó a cabo en un rancho de doble propósito de Iguala Guerrero, México. Antes de iniciar el estudio se colectaron aproximadamente 30 garrapatas completamente ingurgitadas a las que se les realizó un ensayo toxicológico mediante la prueba de paquete de larvas para determinar la susceptibilidad a los plaguicidas convencionales (piretroides, fosforados y amitraz). Los bovinos fueron previamente tratados con ivermectina. Se seleccionaron 20 bovinos los cuales fueron monitoreados cada 15 días con el fin de cuantificar el número de garrapatas en cada lote. Los anticuerpos se incrementaron significativamente a partir de la segunda dosis del inmunógeno y el número de garrapatas por animal en el rancho se mantuvo significativamente bajo durante 7 meses, dos meses por el efecto del inmunógeno y 5 probablemente por la significativa disminución de las garrapatas en el potrero. Los programas de control integral de garrapatas deben incluir el uso alternado de vacunas y pesticidas, con la finalidad de disminuir el uso de pesticidas, la contaminación ambiental y la lecha y carne destinadas para consumo humano

Frecuencia e identificación molecular de Cryptosporidium spp en becerras lactantes mantenidas en confinamiento en Aguascalientes, México

In order to determine the frequency of Cryptosporidium spp and to identify the species or genotype of oocysts found in confined, suckling lactating calves in Aguascalientes, Mexico dairies, fecal samples were collected from 8-14-d old-calves in eight different dairies. Samples were smeared, Kinyoun-stained and subjected to nested PCR in order to amplify parasite's 18S rRNA region (830 bp). Positive samples were cloned on a pGEM-T vector then sequenced. Frequency of animals positive to Cryptosporidium spp by microscopy was 75 % (95/126), with a 25 to 100 % range among dairies, even though, using molecular techniques the frequency of positive animals was 67 % (85/126), with a 20 to 100 % range among dairies. All other samples were negative to both tests. All samples sequenced had a 100 % homology with the 18S rRNA region of C. parvum. Results confirm the relevance of C. parvum as a major etiology of cryptosporidiosis in suckling dairy calves and show its broad distribution in the area. Given that C. parvum is a zoonotic species, calf managers should be considered as broadly exposed to the infection.Con el objeto de determinar la frecuencia de Cryptosporidium spp, y realizar la identificación de especie o genotipo de los ooquistes encontrados, en becerras lactantes mantenidas en confinamiento en establos lecheros de Aguascalientes, México, se tomaron muestras de excremento de 126 becerras de 8 a 14 días de edad provenientes de ocho establos, las cuales fueron procesadas mediante frotis fecal teñido con Kinyoun y por PCR anidada para amplificar la región 18S rARN del parásito (830 pb), las muestras positivas fueron clonadas en un vector pGEM-T y secuenciadas. La frecuencia de animales positivos a Cryptosporidium spp por microscopía fue de 75 % (95/126), con una escala entre establos de 25 a 100 %, en tanto que por técnicas moleculares fue de 67 % (85/126), con escala entre establos de 20 a 100 %, el resto de las muestras fueron negativas en ambas pruebas. Todas las muestras secuenciadas tuvieron una homología del 100 % con la región 18S rARN de C. parvum. Estos resultados confirman la importancia de C. parvum como principal agente de la criptosporidiosis en becerras lactantes y demuestra su amplia distribución en la zona, debido a que C. parvum es una especie zoonótica, debe de considerarse que las personas que manejan a las becerras se encuentran ampliamente expuestas a la infección

Potential economic impact assessment for cattle parasites in Mexico. Review

Las pérdidas económicas causadas por parásitos del bovino en México se calcularon anualmente. Los principales factores considerados para esta evaluación incluyeron el número total de animales a riesgo, los posibles efectos dañinos del parasitismo sobre la producción de leche o ganancia de peso, y los decomisos de subproductos pecuarios. Las pérdidas económicas fueron estimadas en dólares americanos (US$) y se basaron en las pérdidas del rendimiento productivo de animales no tratados. Estas estimaciones reflejan los principales efectos de seis parásitos o grupos de parásitos sobre la producción bovina. El impacto económico potencial (millones de dólares) fue: nematodos gastrointestinales US$ 445.10; coccidias (Eimeria spp.) US$23.78; duelas del hígado (Fasciola hepatica) US$ 130.91; garrapatas (Rhipicephalus microplus) US$573.61; mosca de los cuernos (Haematobia irritans) US$ 231.67; y mosca de los establos (Stomoxys calcitrans) US$6.79. En general, las pérdidas anuales causadas por los seis principales parásitos del bovino en México se estimaron en US$ 1.41 mil millones. Considerando que la población bovina nacional en 2013 fue de 32.40 millones de bovinos, la pérdida anual estimada fue de US$43.57 por animal. Se hace mención de las limitaciones que tienen el uso de algunas referencias para las estimaciones, particularmente cuando se extrapolan situaciones locales a una escala nacional. Sin embargo, el resultado general obtenido en este estudio demuestra la magnitud e importancia del parasitismo en el ganado de México y los desafíos para maximizar la rentabilidad de la industria ganadera sin recurrir al uso de estrategias de control integrado sustentable de parásitos. ABSTRACT Here, economic losses caused by cattle parasites in Mexico were estimated on an annual basis. The main factors taken into consideration for this assessment included the total number of animals at risk, potential detrimental effects of parasitism on milk production or weight gain, and records of condemnation on livestock byproducts. Estimates in US dollars (US$) were based on reported yield losses in untreated animals. These estimates reflect the major effects on cattle productivity of six parasites, or parasite group. The potential economic impact (US$millions) was: gastrointestinal nematodes US$ 445.10; coccidia (Eimeria spp.) US$23.78; liver fluke (Fasciola hepatica) US$ 130.91; cattle tick (Rhipicephalus microplus) US$573.61; horn fly (Haematobia irritans) US$ 231.67; and stable fly (Stomoxys calcitrans) US$6.79. Overall, the yearly economic loss due to the six major parasites of cattle in Mexico was estimated to be US$ 1.41 billion. Considering that the national cattle herd registered in 2013 included 32.40 million head, the estimated yearly loss per head was US$ 43.57. The limitations of some of the baseline studies used to develop these estimates, particularly when extrapolated from local situations to a national scale, are acknowledged. However, the general picture obtained from the present effort demonstrates the magnitude and importance of cattle parasitism in Mexico and the challenges to maximize profitability by the livestock industry without adapting sustainable and integrated parasite control strategies

In Vitro Evaluation of Essential Oils and Saturated Fatty Acids for Repellency against the Old-World Sand Fly, Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae)

The sand fly, Phlebotomus papatasi (Scopoli, 1786), is a major vector for Leishmania major in the Middle East, which has impacted human health and US military operations in the area, demonstrating the need to develop effective sand fly control and repellent options. Here, we report the results of spatial repellency and avoidance experiments in a static air olfactometer using the female P. papatasi testing essential oils of Lippia graveolens (Mexican oregano), Pimenta dioica (allspice), Amyris balsamifera (amyris), Nepeta cataria (catnip), Mentha piperita (peppermint), and Melaleuca alternifolia (tea tree); the 9–12 carbon saturated fatty acids (nonanoic acid, decanoic acid, undecanoic acid, and dodecanoic acid); and the synthetic repellents DEET and IR3535. The materials applied at 1% exhibited varying activity levels but were not significantly different in mean repellency and avoidance from DEET and IR3535, except in regards to nonanoic acid. Some materials, particularly nonanoic and undecanoic acids, produced sand fly mortality. The observed trends in mean repellency over exposure time included the following: (1) P. dioica oil, M. alternifolia oil, decanoic acid, undecanoic acid, DEET, and IR3535 exhibited increasing mean repellency over time; (2) oils of N. cataria, A. balsamifera, M. piperita, and dodecanoic acid exhibited relatively constant mean repellency over time; and (3) L. graveolens oil and nonanoic acid exhibited a general decrease in mean repellent activity over time. These studies identified the essential oils of N. cataria and A. balsamifera as effective spatial repellents at reduced concentrations compared to those of DEET. Additional research is required to elucidate the modes of action and potential synergism of repellents and essential oil components for enhanced repellency activity.This article is published as Temeyer, Kevin B., Kristie G. Schlechte, Joel R. Coats, Charles L. Cantrell, Rodrigo Rosario-Cruz, Kimberly H. Lohmeyer, Adalberto A. Pérez de León, and Andrew Y. Li. 2024. "In Vitro Evaluation of Essential Oils and Saturated Fatty Acids for Repellency against the Old-World Sand Fly, Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae)" Insects 15, no. 3: 155. https://doi.org/10.3390/insects15030155. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Variants in toll-like receptor 9 gene influence susceptibility to tuberculosis in a Mexican population

Background: The control of Mycobacterium tuberculosis (Mtb) infection begins with the recognition of mycobacterial structural components by toll like receptors (TLRs) and other pattern recognition receptors. Our objective was to determine the influence of TLRs polymorphisms in the susceptibility to develop tuberculosis (TB) in Amerindian individuals from a rural area of Oaxaca, Mexico with high TB incidence. Methods: We carried out a case–control association community based study, genotyping 12 polymorphisms of TLR2, TLR4, TLR6 and TLR9 genes in 90 patients with confirmed pulmonary TB and 90 unrelated exposed but asymptomatic household contacts. Results: We found a significant increase in the frequency of the allele A of the TLR9 gene polymorphism rs352139 (A>G) in the group of TB patients (g.f. = 0.522) when compared with controls (g.f. = 0.383), (Pcorr = 0.01, OR = 1.75). Under the recessive model (A/G + A/A vs G/G) this polymorphism was also significantly associated with TB (Pcorr = 0.01, OR= 2.37). The association of the SNP rs352139 was statistically significant after adjustment by age, gender and comorbidities by regression logistic analysis (Dominant model: p value = 0.016, OR = 2.31; Additive model: p value = 0.023, OR = 1.68). The haplotype GAA of TLR9 SNPs was also associated with TB susceptibility (Pcorr = 0.02). Differences in the genotype or allele frequencies of TLR2, TLR4 and TLR6 polymorphisms between TB patients and healthy contacts were not detected. Conclusions: Our study suggests that the allele A of the intronic polymorphism rs352139 on TLR9 gene might contribute to the risk of developing TB in Mexican Amerindians

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