All You Need to Know About Neck Threadworms and Your Itchy Horse

By Jane Clothier

Finally, here inis the information that owners of itchy horses have been waiting for.

Neck threadworms (Onchocerca cervicalis) are now found in many countries throughout the world, even in regions where the textbooks say it cannot exist. Well, it does - and owners who have used the methods included in this book to successfully help their horses are testament to the fact.

In this book, you can learn what this unusual parasite is, how it is transmitted from horse to horse, and what you can do to get in control of the unbearable itching it can cause. This book contains everything you need to know, collated and edited into 20 succinct and easy-to-read chapters.

Since first published in 2013, this information has proved invaluable for owners, saving months and even years of heartache and expense in the search for elusive answers. Now every horse owner can have this information at their fingertips, equipping them to identify and then fight their horse's neck threadworms.

Dr Jane Clothier has been researching and writing about this parasite for nearly a decade. She holds a PhD in Animal Science (Equine), meaning you can rely on the information included in this publication as being validly researched and carefully interpreted.

 

Note: this information is not intended to replace veterinary advice. Your equine veterinarian should always be consulted prior to starting any treatment protocols.

• Language: English
• Publisher: Jane Clothier
• Release date: Jul 15, 2021
• ISBN: 9781386480051

Jane Clothier

Writer Jane Clothier is completing her PhD with the University of New England and CSIRO in Armidale, NSW, Australia. This concerns the ongoing effects of gestational immaturity in the adult horse. She established the blog, The Horse's Back, in 2012 and has been writing for it ever since, with a few contributions from guest authors. When not writing and researching, she has a regional bodywork practice, Balanced Horse Services, also based in Armidale, New South Wales, Australia.

Book preview

1.

Introduction

Look on any ivermectin or moxidectin-based dewormer packet and you’ll see a long list of parasites. Tucked in neatly at the end – it’s nearly always at the end – you’ll see the words Onchocerca microfilariae.

Also known as neck threadworms, these critters vary in length from 6cm to 10cm. Astonishingly, they live in the horse’s nuchal ligament.

Yes, the nuchal ligament. The funicular part runs like a cord along the full length of the neck, from poll to withers, with a flat ligament, the lamella, connecting with the cervical vertebrae lower down (note: this has been found to go no lower than the cervical, ie neck, vertebra C5 in most horses, with only a weak connection at the vertebra C6).

The funicular part of the nuchal ligament, shown in yellow, runs from poll to wither. The lamellar part is in red. (c) sustainabledressage.com

Apparently, most horses have Onchocerca. For many they’re not a problem, but some horses develop a reaction to their microscopic larvae (the microfilariae). This condition is known as Onchocerciasis.

The horses become itchy, mostly around the head, neck, chest, shoulders and underside of the belly. That’s why owners often make the understandable assumption that their horse has Queensland itch or sweet itch.

Onchocerca is what’s known as a parasitic filarial worm (nematode). One reason these worms get relatively little attention is that they don't live in the intestines. The microscopic larval form lives in the horse’s skin, mostly around the head, neck, shoulders, chest and underside of the belly. It is the adult worm that later makes its home in the nuchal ligament. 

The biting insect that serves as a carrier is the Culicoides fly, or biting midge,​ which is also connected to Queensland Itch (aka Sweet Itch, Summer Itch, etc., depending on country).

Despite the low awareness around Onchocerciasis in horses, the problem is global and horses in most countries have been found to have this parasite. Unfortunately for those of us who keep horses in the warmer, humid climates of the world, it’s more prevalent in such areas, as are all parasites. 

It’s an unfortunate coincidence of environment that leads to many cases of neck threadworms being overlooked, because it's wrongly assumed that they can only survive in the humid zones.

Could we be missing something?

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