The "Art of War" against gastrointestinal nematodes in sheep and goat herds of the tropics
Juan Felipe Torres-Acosta (1*), Hervé Hoste (2), Carlos Alfredo Sandoval-Castro (1), Rafael Arturo Torres-Fajardo (1), Javier Ventura-Cordero (1), Pedro Geraldo González-Pech (1), María Gabriela Mancilla-Montelongo (3), Nadia Florencia Ojeda-Robertos (4), Cintli Martínez-Ortíz-de-Montellano (5)
(1) Faculty of Veterinary Medicine and Zootechnics, Universidad Autónoma de Yucatán (UADY), Mérida, México
(2) Interactions Hôtes - Agents Pathogènes (IHAP), Institut National de la Recherche Agronomique (INRA), Ecole Nationale Vétérinaire de Toulouse (ENVT), Université de Toulouse, Toulouse, Francia
(3) Consejo Nacional de Ciencia y Tecnología (CONACYT), Faculty of Veterinary Medicine and Zootechnics, Universidad Autónoma de Yucatán (UADY), Mérida, México
(4) División Académica de Ciencias Agropecuarias (DACA), Universidad Juárez Autónoma de Tabasco (UJAT), Villahermosa, México
(5) Faculty of Veterinary Medicine and Zootechnics, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, México
The present work delves into the concept of infections by gastrointestinal nematodes (GIN) in ruminants in the light of new findings of the animal-parasite-vegetation relationship and shows how to use these to guide the rational use of alternative control methods. First, we reflect on the control of the GIN in the current era and how the indiscriminate use of anthelmintics (AH) has generated a big problem of resistance to these drugs. The research on AH-resistant GIN helped to recognize that high GIN burdens are found in a low proportion of animals in each herd. This makes it possible to propose a new control paradigm based on the selective use of AH only in those animals that need treatment. It is proposed that low GIN infections in herds are due to: (i) the use of native GIN-resistant breeds, (ii) the low infectivity of grasslands for many months of the year, (iii) the consumption of native tropical plants containing secondary compounds (SC) affecting several stages of the GIN cycle, and (iv) grazing behaviour that limits the consumption of infective phases of GIN in low-rise fodder at hours of increased infectivity. There is a need to use a targeted selective treatment strategy aiming to reduce false positives and false negatives events commonly found in several strategies. To reduce reliance on conventional AH, alternative control methods affecting GIN phases outside or inside the host are required. Possibly many producers are already using some alternative method of control without being aware of this. For example, the use of tropical breeds takes advantage of their enhanced ability to resist GINs. In addition, browsing in the tropical forest vegetation involves consuming nutraceutical plants that provide nutrients and SC with AH activity. The aforementioned strategies can be reinforced with dietary supplementation to improve productivity and immune response against GINs. Some producers might be interested in rotational grazing, which serves to evade the infecting larvae in the pastures. In the future they may have access to nematophagous fungi that can be used to prevent L3 larvae from leaving the faeces and contaminate the fodder. One element that will be important is the Barbervax© vaccine that uses an antigen obtained from the Haemonchus contortus intestine to generate antibodies against that parasite achieving parasitic burdens reductions >90%. In conclusion, it is necessary to continue deepening the animal-parasite-vegetation relationship in order to be leaded by such knowledge to make better decisions about control methods. All this to allow the sustainability of the GIN control strategy in each herd.
Keywords: Post-anthelmintic era. Alternative control methods. Combined control strategies.
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