Advertisement

Evaluation of prevalence and clinical implications of anthelmintic resistance in gastrointestinal nematodes in goats

Lars L. MortensenDanish Center for Experimental Parasitology, Department of Veterinary Microbiology, Section for Parasitology, Royal Veterinary and Agricultural University, DK-1870 Frederiksberg C, Denmark.
Present address is Ringe Dyreklinik, 5 Gørtlervej, DK-5750 Ringe, Denmark.

Search for other papers by Lars L. Mortensen in
Current site
Google Scholar
PubMed
Close
 DVM
,
Lisa H. WilliamsonDepartment of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

Search for other papers by Lisa H. Williamson in
Current site
Google Scholar
PubMed
Close
 DVM, MS
,
Thomas H. TerrillSchool of Agriculture, Home Economics and Allied Programs, Agricultural Research Station, Fort Valley State University, Fort Valley, GA 31030.

Search for other papers by Thomas H. Terrill in
Current site
Google Scholar
PubMed
Close
 PhD
,
Robin A. KircherSchool of Agriculture, Home Economics and Allied Programs, Agricultural Research Station, Fort Valley State University, Fort Valley, GA 31030.

Search for other papers by Robin A. Kircher in
Current site
Google Scholar
PubMed
Close
 BS
,
Michael LarsenDanish Center for Experimental Parasitology, Department of Veterinary Microbiology, Section for Parasitology, Royal Veterinary and Agricultural University, DK-1870 Frederiksberg C, Denmark.

Search for other papers by Michael Larsen in
Current site
Google Scholar
PubMed
Close
 PhD
, and
Ray M. KaplanDepartment of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

Search for other papers by Ray M. Kaplan in
Current site
Google Scholar
PubMed
Close
 DVM, PhD

Abstract

Objective—To determine prevalence of resistance to all anthelmintics that are commonly used to treat gastrointestinal nematodes (GINs) in goats.

Design—Prospective study.

Animals—777 goats.

Procedure—On each farm, goats were assigned to 1 of 5 treatment groups: untreated controls, albendazole (20 mg/kg [9.0 mg/lb], PO, once), ivermectin (0.4 mg/kg [0.18 mg/lb], PO, once), levamisole (12 mg/kg [5.4 mg/lb], PO, once), or moxidectin (0.4 mg/kg, PO, once), except on 3 farms where albendazole was omitted. Fecal samples were collected 2 weeks after treatment for determination of fecal egg counts (FECs), and percentage reductions were calculated by comparing data from anthelmintic-treated and control groups. Nematode populations were categorized as susceptible, suspected resistant, or resistant by use of guidelines published by the World Association for the Advancement of Veterinary Parasitology.

Results—Resistance to albendazole was found on 14 of 15 farms, and resistance to ivermectin, levamisole, and moxidectin was found on 17, 6, and 1 of 18 farms, respectively. Suspected resistance to levamisole and moxidectin was found on 4 and 3 farms, respectively. Resistance to multiple anthelmintics (albendazole and ivermectin) was found on 14 of 15 farms and to albendazole, ivermectin, and levamisole on 5 of 15 farms. Mean overall FEC reduction percentages for albendazole, ivermectin, levamisole, and moxidectin were 67, 54, 94, and 99%, respectively.

Conclusions and Clinical Relevance—Anthelmintic resistance in GINs of goats is highly prevalent in the southern United States. The high prevalence of resistance to multiple anthelmintics emphasizes the need for reexamination of nematode control practices. (J Am Vet Med Assoc 2003;223:495–500)

Abstract

Objective—To determine prevalence of resistance to all anthelmintics that are commonly used to treat gastrointestinal nematodes (GINs) in goats.

Design—Prospective study.

Animals—777 goats.

Procedure—On each farm, goats were assigned to 1 of 5 treatment groups: untreated controls, albendazole (20 mg/kg [9.0 mg/lb], PO, once), ivermectin (0.4 mg/kg [0.18 mg/lb], PO, once), levamisole (12 mg/kg [5.4 mg/lb], PO, once), or moxidectin (0.4 mg/kg, PO, once), except on 3 farms where albendazole was omitted. Fecal samples were collected 2 weeks after treatment for determination of fecal egg counts (FECs), and percentage reductions were calculated by comparing data from anthelmintic-treated and control groups. Nematode populations were categorized as susceptible, suspected resistant, or resistant by use of guidelines published by the World Association for the Advancement of Veterinary Parasitology.

Results—Resistance to albendazole was found on 14 of 15 farms, and resistance to ivermectin, levamisole, and moxidectin was found on 17, 6, and 1 of 18 farms, respectively. Suspected resistance to levamisole and moxidectin was found on 4 and 3 farms, respectively. Resistance to multiple anthelmintics (albendazole and ivermectin) was found on 14 of 15 farms and to albendazole, ivermectin, and levamisole on 5 of 15 farms. Mean overall FEC reduction percentages for albendazole, ivermectin, levamisole, and moxidectin were 67, 54, 94, and 99%, respectively.

Conclusions and Clinical Relevance—Anthelmintic resistance in GINs of goats is highly prevalent in the southern United States. The high prevalence of resistance to multiple anthelmintics emphasizes the need for reexamination of nematode control practices. (J Am Vet Med Assoc 2003;223:495–500)