Experimental and modeling approaches to evaluate different aspects of the efficacy of Targeted Selective Treatment of anthelmintics against sheep parasite nematodes
Authored by S Gaba, J Cabaret, C Sauve, J Cortet, A Silvestre
Date Published: 2010
DOI: 10.1016/j.vetpar.2010.03.040
Sponsors:
European Union
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
Model code not found
Abstract
Maintaining a refugia i.e. a proportion of the population that is not
exposed to selection by treatments has been suggested as an alternative
to mass treatment in the management of nematode parasites of sheep.
Three refugia have been identified: nematodes in untreated hosts, encysted larvae and free-living stages on pastures. Here we tested
whether Targeted Selective Treatments (TST) could be relevant in
controlling nematode infections and delaying anthelmintic resistance
selection. We first conducted a one grazing season experiment to compare
all flock treatment (the whole flock was treated monthly) and TST based
on monthly excretion eggs and daily weight gain. Nematode burden was
higher in TST group, but anthelmintic susceptibility of nematodes was
preserved. We then used an individual-based model to evaluate the
sustainability of TST on a longer period. The simulation approach
indicated that TST20\% and TST30\% of the flock were efficient both at
maintaining resistance at a low level and controlling nematode parasite
infections on a mid-term period (i.e. simulation of five grazing
seasons). However for an efficient TST, these percentages of treated
hosts should be adapted to flock size since the number of nematode
parasites exposed to selection increases in large flocks. Our results
also showed a high dependence on the timing of treatment i.e. on the
size of the refugia constituted by the free-living stages on the
pasture. (C) 2010 Elsevier B.V. All rights reserved.
Tags
Strategies
Populations
New-zealand
Grazing sheep
Free-living stages
Ostertagia-circumcincta
Macroparasite aggregation
Teladorsagia-circumcincta
Benzimidazole resistance
Pasture
contamination