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Grazing management through pasture rotation has been mentioned as a viable alternative for the control of Rhipicephalus microplus; however, there is limited information on rotational grazing at field level. The objectives of this research were (1) to evaluate the effect of rotational grazing with 30 and 45 days of pasture rest and continuous grazing (without rest) on R. microplus tick loads in Brahman heifers and its most common crosses with Holstein; (2) to know the parasite dynamics of R. microplus under the three grazing systems in the humid tropics of Mexico; and (3) to determine the effect of the treatments on the characteristics of the pastures (availability of forage biomass, plant height, and soil cover). The experiment was carried out for 1 year from April 2022 to March 2023, with three grazing treatments: Treatments 1 and 2 considered rotational grazing with 30 (RT30) and 45 days of rest (RT45), respectively, and Treatment 3 as continuous grazing (CT00). Thirty calves from 8 to 12 months of initial age were distributed in each treatment (n = 10). Every 14 days, the number of engorged and semiengorged female ticks in cattle was determined. Concomitantly, the region's temperature, relative humidity, and rainfall were recorded, as well as the agronomic characteristics of the pasture. Rotational grazing animals with 30 days of rest had the highest number of ticks, while grazing animals with 45 days of rest had the least. Tick load dynamics among groups did not correlate with climatic variables (p > 0.05). The height and grass cover presented significant changes due to grazing (p < 0.05), which could influence the tick cycle by the exposure of the soil, modifying the microclimatic conditions and consequently harming the survival and development of R. microplus in the evaluated systems. The negative effect of rotational grazing on the nonparasitic phase of R. microplus deserves further studies. [ABSTRACT FROM AUTHOR]

The use of entomopathogenic fungi (EF) is a promising alternative for the control of Rhipicephalus microplus, an important tick affecting cattle globally. This study aimed to evaluate the effect of ultraviolet irradiation (UV) exposure on the percentage of conidia germination and number of colony-forming units of eight strains of Metarhizium anisopliae (MaV55, MaV35, MaV31, MaV25, MaV13, Ma08, MaV05, and MaV02). The UV (UV-A and UV-A+B) irradiation was carried out with an ultraviolet radiation emission lamp. The conidia of each strain were exposed to the UV irradiation treatments for 3 h. MaV25, MaV08, MaV05, MaV13, and MaV31 showed higher tolerance to UV-A radiation exposure, as assessed by conidia germination. UV-A+B radiation decreased the germination percentage of all the M. anisopliae strains. The eight evaluated strains showed good tolerance to UV-A radiation, as assessed by the development of colony-forming units (CFU). UV-A+B radiation did not significantly affect (p > 0.05) the count of the CFU of six of the M. anisopliae strains evaluated (MaV35, MaV13, MaV08, MaV05, MaV31, and MaV02). The novel findings of the UV-tolerant M. anisopliae strains may potentially improve the effectiveness of EF under environmental conditions. Integral research under real tropical conditions is advised to evaluate the effectiveness of the EF strains. [ABSTRACT FROM AUTHOR]

Nematophagous fungi (NF) form part of the soil microbiota and are natural enemies of nematodes, helping to regulate nematode populations. A verticillate NF isolated from soil from Tepalcingo, Mexico, was morphologically and molecularly characterised. This fungus was cultured in two different liquid media—Czapek-Dox broth (CzDoxB) and sweet potato dextrose broth (SPDB)—for 21 days. The ovicidal (OA) and larvicidal (LA) activities of fungal liquid culture filtrates (LCFs) were assessed in 96-well microtitre plates at different concentrations against Haemonchus contortus after 48 h. The morphological and molecular identification revealed the presence of Lecanicillium psalliotae. Additionally, the groups of compounds associated with nematocidal activity were determined from a qualitative chemical profile (QCP) using different reagents. The highest OA of the LCFs was obtained at 25 mg/mL from SPDB and CzDoxB and amounted to 97.2 and 99.06%, respectively. Meanwhile, the highest LA recorded with these LCFs at 100 mg/mL was 54.27% and 96.8%, respectively. The QCP revealed the presence of alkaloids and tannins in both LCFs that have previously been associated with nematocidal activity. Lecanicillium psalliotae exerted an important effect on H. contortus and could be of significance in future studies focused on the control and prevention of haemonchosis in small ruminants. [ABSTRACT FROM AUTHOR]

Rhipicephalus microplus economically impacts cattle production in tropical and subtropical countries. Application of acaricides constitutes the major control method; however, inadequate use has increased resistant tick populations, resulting in environmental and cattle product contamination. Anti-tick vaccines based on the Bm86 antigen are an environmentally friendly, safe, and economically sustainable alternative for controlling R. microplus infestations. Nevertheless, variable efficacy has been experienced against different geographic tick strains. Herein, we evaluated the efficacy of a conserved polypeptide Bm86 derived from a Mexican R. microplus strain previously characterized. Twelve cows were assigned to three experimental groups and immunized with three doses of the polypeptide Bm86 (pBm86), adjuvant/saline alone, and Bm86 antigen (control +), respectively. Specific IgG antibody levels were measured by ELISA and confirmed by Western blot. In addition, the reproductive performance of naturally infested R. microplus was also determined. The more affected parameter was the adult female tick number, with a reduction of 44% by the pBm86 compared to the controls (p < 0.05), showing a vaccine efficacy of 58%. Anti-pBm86 IgG antibodies were immunogenic and capable of recognizing the native Bm86 protein in the eggs, larvae, and guts of R. microplus. The negative correlation between antibody levels and the reduction of naturally tick-infested cattle suggested that the effect of the polypeptide Bm86 was attributed to the antibody response in immunized cattle. In conclusion, the polypeptide Bm86 showed a specific immune response in cattle and conferred protection against R. microplus in a Mexican tropical region. These findings support further experiments with this antigen to demonstrate its effectiveness as a regional vaccine. [ABSTRACT FROM AUTHOR]

Haemonchus contortus (Hc) is an important parasitic nematode of small ruminants. In this study we assembled the transcriptome of Hc as a model to contribute to the knowledge about the profile of the differential gene expression between two Mexican Hc strains under different anthelmintic resistance statuses, one susceptible and the other resistant to ivermectin (IVMs and IVMr, respectively), in order to improve and/or to have new strategies of control and diagnosis. The transcript sequence reads were assembled and annotated. Overall, ~127 Mbp were assembled and distributed into 77,422 transcript sequences, and 4394 transcripts of the de novo transcriptome were matched base on at least one of the following criteria: (1) Phylum Nemathelminthes and Platyhelminthes, important for animal health care, and (2) ≥55% of sequence identity with other organisms. The gene ontology (GO) enrichment analysis (GOEA) was performed to study the level of gene regulation to IVMr and IVMs strains using Log Fold Change (LFC) filtering values ≥ 1 and ≥ 2. The upregulated-displayed genes obtained via GOEA were: 1993 (for LFC ≥ 1) and 1241 (for LFC ≥ 2) in IVMr and 1929 (for LFC ≥ 1) and 835 (for LFC ≥ 2) in IVMs. The enriched GO terms upregulated per category identified the intracellular structure, intracellular membrane-bounded organelle and integral component of the cell membrane as some principal cellular components. Meanwhile, efflux transmembrane transporter activity, ABC-type xenobiotic transporter activity and ATPase-coupled transmembrane transporter activity were associated with molecular function. Responses to nematicide activity, pharyngeal pumping and positive regulation of synaptic assembly were classified as biological processes that might be involved in events related to the anthelmintic resistance (AR) and nematode biology. The filtering analysis of both LFC values showed similar genes related to AR. This study deepens our knowledge about the mechanisms behind the processes of H. contortus in order to help in tool production and to facilitate the reduction of AR and promote the development of other control strategies, such as anthelmintic drug targets and vaccines. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the annual dynamic population of Boophilus microplus in two cattle genotypes. The study was carried out in Martinez de la Torre, Veracruz, Mexico (tropical humid region). Twenty steers of 10 months of age, 185 kg of body weight and naturally infested with B. microplus ticks were used. Two groups of 10 animals were used according to their genotype (¾ Bos taurus [½ Holstein, ¼ Simmental, ¼ Zebu], and ½ Bos taurus [½ Holstein, ½ Zebu]). Animals grazed together in a pasture of five hectares. No ixodicidal treatment was used during the experiment. The number of B. microplus female ticks (> 4.5 mm length) was assessed every 28 days. Temperature (T), relative humidity (RH) and pluvial precipitation (PP) were registered during the study. The U Mann Whitney test was used to analyze differences between both animal genotypes (P < 0.05). Correlations between the number of B. microplus of both genotypes, PP accumulated and average of T (minimum and maximum) regis tered four weeks prior measurement were determined. Throughout the studied period, tick infestation in both animal genotypes was registered. The genotype ¾ Bos taurus had higher B. microplus infestation in nine of the 12 evaluated months (P < 0.05). PP accumulated and minimum T were correlated with the number of ticks in both genotypes. Natural infestation of Boophilus microplus Canestrini, 1887 (Acari: Ixodidae) in two cattle genotypes in the humid tropic of Veracruz, Mexico. [ABSTRACT FROM AUTHOR]

El objetivo del presente estudio fue determinar la dinámica poblacional anual de Boophilus microplus en dos genotipos de ganado bovino. El estudio se realizó en Martínez de la Torre, Veracruz, México (región trópico húmeda). Se utilizaron 20 toretes de diez meses de edad y 185 kg de peso, infestados naturalmente con garrapatas B. microplus. Se formaron dos grupos de diez animales cada uno, según el genotipo (¾ Bos taurus [½ Holstein, ¼ Simmental, ¼ Cebú] y ½ Bos taurus [½ Holstein, ½ Cebú]). Los animales pastaron juntos en una superficie de cinco hectáreas y durante el estudio no recibieron tratamientos ixodicidas. En todos los animales, cada 28 días se registró el número de garrapatas B. microplus hembras ( > 4.5 mm de longitud). Se registró la temperatura (T), humedad relativa (HR) y precipitación pluvial (PP), durante el tiempo que duró el experimento. Se utilizó la prueba de U Mann Whitney para analizar diferencias entre los dos genotipos de animales (P < 0.05). Se correlacionó el número de B. microplus en ambos genotipos, con la PP acumulada y los promedios de T (mínima-máxima) registrados durante cuatro semanas previas a cada medición. Durante todo el periodo estudiado se registraron infestaciones de garrapatas en ambos genotipos de animales. El genotipo ¾ Bos taurus tuvo mayor infestación de B. microplus en nueve de los 12 meses evaluados (P < 0.05). La PP acumulada y la T mínima se correlacionaron con el número de garrapatas en los dos genotipos. [ABSTRACT FROM AUTHOR]