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