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Handbook of Equine Parasite Control – review

Like it or not, the days of calendar-based worming programs are behind us.

One can imagine some horse owners, used to grabbing their dewormer of choice and firing it down the throats of their horses at regular intervals, might be a tad grumpy over the whole affair.

I mean, what could be easier than buying a bunch of wormers every few weeks and dispensing the joy?

Parasitologists now believe this so-called interval-based dosing program and its derivatives have been main contributors to current levels of drug resistance in horse establishments.

The overwhelming evidence suggests that the way forward is evidence-based parasite control (EBPC), authors Craig Reinemeyer and Martin Nielsen explain in their new book, “Handbook of Equine Paraside Control“.

By implementing such a program, horse owners will quickly identify which of their horses are most vulnerable to heavy parasite burdens and many may be surprised at how they reduce their use of dewormers while still keeping parasite numbers in check.

 

Handbook of Equine Parasite Control
by Craig R Reinemeyer and Martin K Nielsen
Softcover, 210pp, Wiley-Blackwell, Oct 2012.
ISBN 9780470658710; RRP $A77.23
Available from Amazon (US), Amazon (UK), and from Wiley. Also available as an e-book 

 

In doing so, they will be eliminating unnecessary use of deworming drugs and doing their bit against the rise of drug resistance among parasites.

Reinemayer and Nielsen, both equine parasitologists, say evidence-based parasite control is a relatively new development in equine medicine, which some vets and horse owner may still see as “new-fangled”.

However, horse vets are now more receptive to the approach, and their book is their attempt to address that interest by offering practical advice and logical recommendations, based on the latest science.

Change, they say, does not come easily.

“The authors face the challenge of changing a mindset, of overcoming four decades of tradition, literally tens of millions of episodes of implementation, and competing recommendations from the marketing departments of every pharmaceutical company with a horse in the race,” they write.

“Change is painful but necessary, and progress in parasite control will be measured one practitioner and one horse owner at a time.”

The authors have successfully distilled a significant body of material into a 210-page volume containing a well-balanced mix of the latest science, together with practical advice for implementing evidence-based programs.

The first section delves into internal parasites and factors affecting their transmission, neatly summarizing the likes of their biology, life cycles, environmental factors, and aspects of the host and the parasite that affect transmission.

It is surprising what science cannot tell us about some of these organisms, signalling that future research still has significant scope to improve parasite management in horses.

Take encysted small strongyles, for example. At a certain stage in their life cycle they burrow into the wall of the digestive tract for a period ranging from a few weeks up to 2.5 years.

They are constantly surrounded by a small volume of clear fluid, but the properties of this liquid are virtually unknown.

Once mature, the adult larvae break through the cyst and into the digestive tract, doing damage to the gut wall in the process, to be ejected back into pasture. Relatively little is known of the mechanical and chemical means by which the larvae do this.

The second section explains the principles of parasite control, dealing not only with anthelmintic use, but non-chemical means of parasite control, such as pasture hygiene and quarantine practices.

This section outlines the anthelmintic drugs available and the normal treatment regimens, from interval dose programs, almost invariably used without diagnostic testing to assess worm burdens, to more strategic dosing – again, without testing for worm burdens. It also explains low-dose daily treatments, which may be responsible for high levels of pyrantel pamoate/embonate resistance in North America.

The third section delves into diagnosing and assessing parasitologic information, the tests for assessing worm burdens and the use of fecal egg counts to detect resistance to anthelminitics.

By now, the pair have laid the groundwork to lay out a synopsis for evidence-based parasite control.

They lay out the scientific arguments for this approach in compelling fashion.

“When veterinary practitioners and horse owners turn to parasitologists for advice and guidance, the experience commonly results in frustration, annoyance, or wholesale rejection of any ‘new fangled’ recommendations,” the pair admit.

“Those involved with the practical aspects of equine management typically seek simple and straightforward advice, and parasite control in horses has long been just that – a one-size-fits-all, generic recipe that only considers a drug and calendar.

“Unfortunately, evidence-based parasite control is more complicated than most pragmatists suspect, and this book has attempted to explain why.”

An evidence-based approach relies on the use of diagnostic testing before applying the strategic use of the right anthelmintics to achieve three things:

  • Minimize the risk of parasitic disease.
  • Reduce infection pressure.
  • Maintain and prolong the effectiveness of existing drugs.

The last section of the book is a practical goldmine of information, where the authors describe 20 real-life case histories. They outline the issue or problem in each case, and pose the questions raised in each circumstance. They then explain their thinking on the issue and the answers.

It is a great approach, providing easily digestible information on a wide range of practical parasite problems.

The case histories are an eclectic mix, ranging from dealing with a riding-school owner sceptical about the accuracy of egg counts (subsequent testing of 31 horses on three occasions showed no extreme variability – horses that had higher fecal eggs counts in the first tests tended to continue in the same vein for later tests, and horses with lower counts tended to stay low).

There are also case histories involving individual horses – one with repeated colic, a foal with diarrhea, another with oral lesions.

In all, the cases provide a great mix of some pretty interesting scenarios.

One suspects that the task confronting Reinemayer and Nielsen, in assessing what was worthy of inclusion in the handbook and what should be left out, was not easy. The pair did an excellent job in that regard, producing a handbook which is logically structured and lays out what veterinarians, technicians and others with an interest in worm control need to know to put together a parasite control program using the latest principles.

The book is being promoted as a companion for equine veterinary practitioners, veterinary students, equine veterinary technicians and nurses, researchers in equine parasitology, horse owners, and farm and stable managers.

Each chapter concludes with the references to relevant scientific papers, should equine professionals choose to delve further.

Nielsen told Horsetalk: “The target reader would be veterinary practitioners, laboratory and veterinary technicians, farm managers and other equine professionals. The ordinary horse owner may find it a bit hard to read, but a lot have great interest in parasite control and would probably find the book useful.”

That said, a keen horse owner with a special interest in parasite control will find it a valuable source of useful information, such as the management issues in dealing with “lawns and roughs” in pasture, the merits of harrowing pastures, and pasture rotation strategies, let alone the sensible use of drugs to keep worm numbers under contol.

Reinemeyer and Nielsen are to be congratulated for producing the book, having identified a clear need for such a handbook. It is the kind of pro-active action that will promote much-needed change  - one practitioner and one horse owner at a time.


Craig R. Reinemeyer graduated from the Ohio State University College of Veterinary Medicine in 1976, and spent 5 years in mixed animal practice before returning to OSU to pursue a PhD in veterinary parasitology. He was a faculty member of the University of Tennessee College of Veterinary Medicine from 1984 to 1998, and served as the President of the American Association of Veterinary Parasitologists from 2003 to 2004. In 1997, Dr. Reinemeyer founded East Tennessee Clinical Research, a contract research organization that conducts pharmaceutical studies to facilitate the development of new veterinary drugs. ETCR’s efforts have contributed to the approval of several currently marketed anthelmintics for horses, cattle, and pets.

Martin K. Nielsen is Assistant Professor in the Department of Veterinary Science of the Maxwell H. Gluck Equine Research Center at the University of Kentucky. He has a doctorate from the University of Copenhagen, and was a faculty member there for four years before moving to Kentucky. His research interests include endoparasite infections of horses, clinical and molecular diagnosis, epidemiology, surveillance, and control.

 


 

Table of contents

SECTION I Internal Parasites and Factors Affecting Their Transmission 
1 Biology and Life Cycles of Equine Parasites 
2 Pathology of Parasitism and Impact on Performance 
3 Environmental Factors Affecting Parasite Transmission 
4 Host Factors Affecting Parasite Transmission 
5 Parasite Factors Affecting Transmission 

SECTION II Principles of Equine Parasite Control 
6 Decreasing Parasite Transmission by Nonchemical Means 
7 Pharmaceutical Approaches to Parasite Control 

SECTION III Diagnosis and Assessment of Parasitologic Information 
8 Diagnostic Techniques for Equine Parasitism 
9 Detection of Anthelmintic Resistance 
10 Evaluating Historical Information 
11 Synopsis of Evidence-Based Parasite Control 

SECTION IV Case Histories 
Case 1 Mystery Drug 
Case 2 Pyrantel Efficacy Evaluation 
Case 3 Egg Count Results From Illinois Yearlings 
Case 4 Colic and Parasites 
Case 5 Confinement after Deworming 
Case 6 Abdominal Distress in a Foal 
Case 7 Quarantining Advice 
Case 8 Diarrhea and Colic 
Case 9 Foal Diarrhea 
Case 10 Oral Lesion 
Case 11 Skin Lesion 
Case 12 Legal Case 
Case 13 Repeated Egg Counts 
Case 14 Repeated Colic 
Case 15 Ivermectin Efficacy 
Case 16 Ten Commandments 
Case 17 Ivermectin Egg Reappearance 
Case 18 Name that Worm 
Case 19 Parasite Control for Yearlings 
Case 20 Reaction to Treatment 

 

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