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The objective of the study was to determine the parasitological and immuneresponse in horses naturally re-infected with gastrointestinal nematodes (GIN) after an-thelmintic treatment in the humid tropic of Mexico. The study was conducted in Tenosique,Tabasco, Mexico. A total of 30 horses were sampled monthly for nine months. Fecal sampleswere obtained to determine the number of nematode eggs per gram (EPG) of feces. Stoolcultures were performed to obtain and identify infective larvae (L3) genera. Blood sampleswere also obtained to determine the packed cell volume (PCV), the total plasma protein(TPP), and the differential leukocyte count (DLC). Serum enzyme-linked immunosorbentassays (ELISA) were performed to determine IgA levels against adult cyathostomins andStrongylusnematode antigen. The analyses considered the age and gender of the horses,and the season (Cold, rainy and dry). The number of EPG and TPP were higher in females(1224±1269 and 7.6±0.6 gdL−1, respectively) than males (623±671 and 7.4±0.5gdL−1, respectively), and no differences were observed with animal age (p > 0.05). Thenumber of EPG increased in the rainy season. The main nematodes involved were of thesubfamily Cyathostominae (97.4%) and to a lesser degree of speciesStrongylus equinus,S.edentatus,S. vulgaris, andOxyuris equii. The season affected the leukocytes, neutrophils,and lymphocytes counts but not eosinophils. Variables such as gender, animal age, andenvironmental conditions are important elements for a diagnosis of GIN and the applicationof treatments for its control., El objetivo fue determinar la respuesta parasitológica e inmune en caballos rein-fectados naturalmente con nematodos gastrointestinales (NGI) posterior a la desparasitaciónen el trópico húmedo de México. El estudio se realizó en Tenosique, Tabasco, México. Seutilizaron 30 caballos muestreados mensualmente durante nueve meses. Se determinó elnúmero de huevos por gramo de heces (HPG). Se realizaron coprocultivos para obtenere identificar larvas infectivas (L3). Se obtuvieron muestras de sangre para determinar elvolumen celular aglomerado (VCA), proteína plasmática (PPT) y el conteo diferencial deleucocitos (CDL). Se realizaron ensayos de inmuno absorción enzimática (ELISA) en sueropara determinar los niveles de IgA contra antígenos de Ciatostómidos y deStrongylus. Losanálisis consideraron la edad y el género, también se estudió la época (fría, lluviosa y seca).El número de HPG y PPT fueron más altos en las hembras (1224±1269 y 7.6±0.6 gdL−1,respectivamente) que en los machos (623±671 y 7.4±0.5 gdL−1, respectivamente), y nose observaron diferencias con la edad del animal (p > 0.05). El número de HPG aumentó enla temporada de lluvias. Los principales nematodos fueron de la subfamilia Cyathostominae(97.4%) y en menor grado las especiesStrongylus equinus,S. edentatus,S. vulgaris, yOxyuris equii. La época afectó el conteo de leucocitos, neutrófilos y linfocitos, pero noeosinófilos. Las variables como el género, edad animal y las condiciones ambientales sonelementos a considerar para un diagnóstico de NGI y la aplicación de tratamientos para sucontro.

Ivermectin (IVM) is an anthelmintic compound commonly used off-label in mules due to its broad-spectrum of activity. Despite the general use of IVM in mules with the same dose and route of administration licensed for horses, significant pharmacokinetic differences might exist between horses and mules, as already observed for donkeys. The aim of the present study was to evaluate the pharmacokinetic profile and anthelmintic efficacy of an oral paste of IVM in mules naturally infected with cyathostomins. Fifteen adult mules with fecal egg counts (FEC) ≥200 eggs per gram (EPG), with exclusive presence of cyathostomins, were included in the study. All mules were orally treated with IVM according to the manufacturer's recommended horse dosage (200 µg/kg body weight). FECs were performed before (day-10 and day-3) and after treatment at days 14 and 28 by using a modified McMaster method. The FEC reduction (FECR%) was also calculated. Blood samples were collected from five animals at various times between 0.5 h up to 30 days post treatment to determine pharmacokinetic parameters. The maximum IVM serum concentration (Cmax) was 42.31 ± 10.20 ng/mL and was achieved at 16.80 ± 9.96 hours post-treatment (Tmax), area under the curve (AUC) was 135.56 ± 43.71 ng × day/mL. FECR% remained high (>95%) until the 28th day.

Ivermectin (IVM) is an anthelmintic compound commonly used off-label in mules due to its broad-spectrum of activity. Despite the general use of IVM in mules with the same dose and route of administration licensed for horses, significant pharmacokinetic differences might exist between horses and mules, as already observed for donkeys. The aim of the present study was to evaluate the pharmacokinetic profile and anthelmintic efficacy of an oral paste of IVM in mules naturally infected with cyathostomins. Fifteen adult mules with fecal egg counts (FEC) ≥200 eggs per gram (EPG), with exclusive presence of cyathostomins, were included in the study. All mules were orally treated with IVM according to the manufacturer's recommended horse dosage (200 µg/kg body weight). FECs were performed before (day-10 and day-3) and after treatment at days 14 and 28 by using a modified McMaster method. The FEC reduction (FECR%) was also calculated. Blood samples were collected from five animals at various times between 0.5 h up to 30 days post treatment to determine pharmacokinetic parameters. The maximum IVM serum concentration (Cmax) was 42.31 ± 10.20 ng/mL and was achieved at 16.80 ± 9.96 hours post-treatment (Tmax), area under the curve (AUC) was 135.56 ± 43.71 ng × day/mL. FECR% remained high (>95%) until the 28th day.

Ivermectin (IVM) is an anthelmintic compound commonly used off-label in mules due to its broad-spectrum of activity. Despite the general use of IVM in mules with the same dose and route of administration licensed for horses, significant pharmacokinetic differences might exist between horses and mules, as already observed for donkeys. The aim of the present study was to evaluate the pharmacokinetic profile and anthelmintic efficacy of an oral paste of IVM in mules naturally infected with cyathostomins. Fifteen adult mules with fecal egg counts (FEC) ≥200 eggs per gram (EPG), with exclusive presence of cyathostomins, were included in the study. All mules were orally treated with IVM according to the manufacturers recommended horse dosage (200 µg/kg body weight). FECs were performed before (day-10 and day-3) and after treatment at days 14 and 28 by using a modified McMaster method. The FEC reduction (FECR%) was also calculated. Blood samples were collected from five animals at various times between 0.5 h up to 30 days post treatment to determine pharmacokinetic parameters. The maximum IVM serum concentration (Cmax) was 42.31 ± 10.20 ng/mL and was achieved at 16.80 ± 9.96 hours post-treatment (Tmax), area under the curve (AUC) was 135.56 ± 43.71 ng × day/mL. FECR% remained high (>95%) until the 28th day.

Cyathostomins are the most prevalent horse nematodes worldwide and over 50 species are described. The eggs and the infective larvae (L3) can easily be obtained or cultured from infected horses, but cannot be differentiated morphologically at species level. A reverse line blot (RLB) method based on the hybridization of a PCR fragment with a species specific probe, has previously been developed for the differentiation of individual eggs and/or L3s, but is too labor intensive for large scale studies. In the present study a RLB method on multiple pooled L3s for the semi-quantitative differentiation of cyathostomin larval cultures was developed and validated. First, the probability of the presence of a certain species within a pool was calculated as function of the frequency and the number of L3s within a pool. Ten L3s per pool were found to be optimal. Next, the probability, the chance of occurrence was calculated when 4 pools per culture were used. The probability distributions for 0, 1, 2, 3 or 4 positive pools were transformed into the corresponding median frequency of the cumulative probability: 0.014, 0.04, 0.08, 0.16 and 0.59, respectively. Based on these calculated probabilities, RLB on 10 L3s per pool and 4 pools per sample was validated by estimating the cross-hybridization, precision and accuracy in 3 groups of horses. First, absence of cross-hybridization was confirmed by differentiation of the same L3s (160 L3s from the 4 horses from group 1) in the RLB on individual as well as on pooled L3s. Cross-hybridization was excluded for 9 of the most common cyathostomins. Next, the precision and accuracy were determined by the differentiation of 10 replicates of 3 cultures from 3 horses from group 2 (1200 L3s). The coefficient of variation (CV) was between 0 and 0.90 and the accuracy was between 0.42 and 1.73. A Monte Carlo simulation based on the observed scores and associated probability distributions gave similar results as the use of a fixed median frequency.