EQUINE | Equine Disease Update
Equine Disease Quarterly
FROM : EQUINE DISEASE QUARTERLY College of Agriculture , Food and Environment Department of Veterinary Science
APRIL 2017 Volume 26 , Number 2
EQUINE | Equine Disease Update
The Future of Parasite Control ?
In this issue , Dr . Gene Lyons provides a brief review of the history and current status of anthelmintic treatment of important equine gastrointestinal parasites . No new anthelmintics with newer modes of action have been introduced since the early 1980s , and levels of anthelmintic resistance are ever increasing in cyathostomin and Parascaris spp . parasites . While resistance is slow to develop , work by Dr . Lyons has clearly illustrated that once it appears in a given parasite , it is there to stay .
Today , we can expect resistance to at least one drug class to be present in every equine operation across the world , and an overwhelming majority will feature multi-drug resistance . With only three classes to choose between , we are running out of treatment options . A pertinent question to ask is how to tackle this emerging crisis and what to expect in the future .
The first step is to acknowledge the extent of the problem . Despite recommendations given during the past couple of decades , a majority of individuals in the industry continue to use oldfashioned parasite control programs based on frequent treatments given year-round without any consideration of treatment efficacy , parasites present , and climatic conditions . If no diagnostic testing is done , resistance will not be identified . For the long term , we need new anthelmintic drug classes with new modes of action . It is important to learn from the past however , and realize that no drug class is going to remain effective indefinitely , and that reverting back to treatment regimens of the past would be a complete mistake . The pharmaceutical industry is not anticipating developing any equine products in the foreseeable future . Recent pharmaceutical trends are aimed at co bination deworming products , i . e . formulations where two or more dewormers targeting the same parasites are combined into the same product . Research in the sheep industry has also The Future of Parasite Control ? highlighted the importance of reducing treatment intensity to avoid development of multi-drug resistance . A recent project by the author highlighted the importance of high starting efficacy of the given combination . If combination treatment efficacy is markedly less than the desired 95 percent or above , resistance may develop quickly . The author ’ s laboratory is also testing a bacterial dewormer . Strains of naturally occurring Bacillus huringiensis produce crystal proteins capable of killing worm parasites . If successful , this could become an anthelmintic product in the future .
Perhaps the most important element in future parasite control programs is utilization of good diagnostic tools . Fecal egg counts will remain a cornerstone of control programs , but they have limitations in not providing information about larval stages and specific types ( species ) of parasites present . Recent collaborations have led to several new diagnostics , including species- and stage-specific serum ELISAs for important strongyle parasites , and an ultrasonographic technique for determining ascarid burdens in foals . One current project is making use of DNA-sequencing technologies to identify
• Volume 19 no 2 • June 2017 • 23