Issue |
Vet. Res.
Volume 34, Number 4, July-August 2003
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|
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Page(s) | 461 - 467 | |
DOI | https://doi.org/10.1051/vetres:2003018 | |
How to cite this article | Vet. Res. (2003) 461-467 |
DOI: 10.1051/vetres:2003018
Multispecies and multiple anthelmintic resistance on cattle nematodes in a farm in Argentina: the beginning of high resistance?
Miguel E. Mejíaa, Belisario M. Fernández Igartúaa, Enrique E. Schmidtb and Jacques Cabaretca Veterinary Surgeons, Los Aromos 134, CC 116, CP 6070 Lincoln, Argentina
b Dpto Prod. Anim., Fac. Vet. Ciencias Veterinarias, Universidad de La Pampa, Calle 1 esp. 116, CP 6390 General Pico, Argentina
c INRA, Bio-Agresseurs Santé Environnement, 37380 Nouzilly, France
(Received 26 November 2002, accepted 1 April 2003)
Abstract
There are very few resistance records on cattle nematodes. South American successive records
have been increasing rapidly since the year 2000. In Argentina, increasing dissatisfaction
based on the exclusive use of macrocyclic lactones has prompted the use of benzimidazoles in
the Pampean region. The studied farm is located in the Argentina humid Pampas and had
apparently poor results after anthelmintic treatments. Evaluation of resistance was firstly
based on faecal egg reduction after treatment in November 2001 and June 2002 and was
complemented with worm counts obtained by necropsy in June 2002. The study reports that the
reduction of faecal egg excretion after benzimidazole (reduction 31-79%) or ivermectin
treatments (76-97%) in November 2001 was insufficient and these poor results were confirmed
in June 2002 (benzimidazoles (65-89%) and ivermectin (47-77%)). Several methods for
evaluating faecal egg count reduction were performed and yielded different results. A new
method based on the estimated faecal egg counts (corrected from the initial faecal egg counts
and animal type using a general linear model) was used and gave higher flexibility in the
interpretation of putative resistance to anthelmintics. From necropsy results, it could be
concluded that Cooperia oncophora was resistant to avermectins and benzimidazoles and
that Cooperia punctata, Ostertagia ostertagi and Haemonchus placei were
resistant to benzimidazoles. This case of multispecies and multidrug resistance is probably
not unique and could reflect the emergence of resistances in Argentina. This emergence is
probably due to the intensive use of anthelmintics, the absence of refugia, and the frequent
circulation of infected cattle.
Key words: nematode / cattle / resistance / anthelmintic / Argentina
Correspondence and reprints: Jacques Cabaret Tel.: (33) 2 47427768; fax: (33) 2 47427774;
e-mail: cabaret@tours.inra.fr
© INRA, EDP Sciences 2003