Inefficacy of ivermectin and moxidectin treatments against Dictyocaulus viviparus in dairy calves

Background The bovine lungworm Dictyocaulus viviparus negatively impacts bovine health and leads to substantial economic losses. Lungworm infections can be difficult to manage due to the unpredictable and severe nature of clinical outbreaks. Despite the widespread use of macrocyclic lactones (MLs) i...

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Bibliographic Details
Published in:Veterinary record 2024-08, Vol.195 (3), p.no-no
Main Authors: Campbell, Paul, Forbes, Andrew, McIntyre, Jennifer, Bartoschek, Taylor, Devine, Kayleigh, O'Neill, Kerry, Laing, Roz, Ellis, Kathryn
Format: Article
Language:English
Subjects:
Animals
Anthelmintics - pharmacology
Anthelmintics - therapeutic use
Cattle
Cattle Diseases - drug therapy
Cattle Diseases - parasitology
Dairying
Dictyocaulus - drug effects
Dictyocaulus Infections - drug therapy
Drug Resistance
Feces - parasitology
Female
Ivermectin - pharmacology
Ivermectin - therapeutic use
Macrolides - pharmacology
Macrolides - therapeutic use
Parasite Egg Count - veterinary
Scotland
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Summary:Background The bovine lungworm Dictyocaulus viviparus negatively impacts bovine health and leads to substantial economic losses. Lungworm infections can be difficult to manage due to the unpredictable and severe nature of clinical outbreaks. Despite the widespread use of macrocyclic lactones (MLs) in grazing cattle in the UK, there have been no confirmed reports of resistant lungworms to date, with only one case of anthelmintic‐resistant (ML) lungworm confirmed worldwide. Methods Lungworm Baermann filtrations were conducted on first‐season grazing dairy calves as part of a wider study investigating anthelmintic resistance in gastrointestinal nematodes in Scotland using the faecal egg count reduction test. Results Clinical signs and significant numbers of lungworm larvae in faeces were observed after treatment with either ivermectin or moxidectin. Limitations There are no established guidelines for the diagnosis of resistant lungworms in the field. Currently, resistance can only be diagnosed after a controlled efficacy test has been conducted. This limits the conclusions that can be drawn; however, they are highly suggestive of resistance. Conclusion This short report describes the inefficacy of ivermectin and moxidectin against D. viviparus and is highly suggestive of ML resistance.
ISSN:0042-4900
2042-7670
2042-7670
DOI:10.1002/vetr.4265