Resumen:
Gastrointestinal parasites are responsible for enormous losses in sheep production worldwide, among the parasites that infect sheep is Haemonchus contortus, is a haematophage nematode responsible for causing anemia and hypoproteinemia in the host, which in turn decreases the development of animals and makes them susceptible to other diseases, the control of this nematode is complicated due to the constant reinfection during grazing, also due to the absence of accurate diagnosis with the use of microscopy and molecular techniques such as PCR for the identification of isolates resistant, this combined an inadequate handling of the anthelmintic treatments, these mainly have generated resistance on the part of the parasites. The use of plants for the control of parasites is an alternative that has been reported to have a decrease in the number of eggs per gram of feces in different degrees depending on the bioactive substance present. Onion (Allium cepa) is a crop widely consumed in Mexico for both food and medicinal use traditionally. Allium cepa contains volatile and non-volatile compounds such as thiosulfinatos, sapogenins, saponins and flavonoids, to which antioxidant, antimicrobial, antitumor and anthelminthic properties have been attributed. Objective. To evaluate the effect of onion (Allium cepa) for the control of Haemonchus contortus in sheep. Methodology. Twenty-four naturally infected sheep were used, they were divided into 3 groups; control, ivermectin and onion, fecal samples were taken straight from the rectum for 5 weeks, analyzed by Faust, PCR and McMaster for the identification of Haemonchus contortus and to calculate the number of eggs per gram of stool, samples were taken from blood weekly and hematological values were determined; hematocrit, plasma proteins, erythrocytes and leukocytes. Results. The administration of Allium cepa in sheep had efficacy of 50% compared to ivermectin that had 75%, there was no significant difference between treatments, Allium cepa had no adverse effects on the hematological parameters. Conclusion. The use of Allium cepa is a viable alternative because it does not alter the hematological parameters in sheep and decreased the number of eggs per gram of feces and does not pollute the environment and has no withdrawal time. The following considerations must be used, as long as it is acquired as agricultural waste due to the high cost and the producer receives training for its correct administration.