ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Horse Disease Focus - Worms

Updated on March 6, 2013

Horses and Worms

Horses get worms. In fact, horses get a lot of worms...there are almost 150 species of internal parasite that affect horses.

Wild horses range over large areas. This reduces the chance of a horse grazing close to its own or somebody else's dung and picking up worms. Domestic horses, confined to smaller pastures or stalls, often pick up a significant parasite load. Severe infections cause weight loss, anemia and colic.

Because of this, worm prevention is an important part of managing a horse.

Controlling Worms

Controlling worms is done by using a wormer.

Horses should be wormed every six weeks or so. Wormer is administered orally, either by the use of a powder mixed with a grain feed or by using a syringe to squirt paste into the mouth. In general, the syringe method is preferable. Dosage is more accurate and some horses will refuse to eat feed that has wormer in it. (Presumably, it doesn't taste that good).

Foals and yearlings should be given wormer specially designed for young horses.

Many people recommend rotating types of wormer. The most common active ingredient is ivermectin, but if you only use ivermectin the worms may become resistant. The best practice is to rotate through four or five different active ingredients. Always buy wormer from a reputable vendor and be aware that once a syringe has been opened, the unused wormer often goes bad fairly quickly. Dosage is based off of weight and wormer comes with charts - invest in a weight tape to give a quick and reasonably accurate estimate of your horse's weight. The exact schedule depends on your location, climate and the level of risk of specific parasite species.

In addition to using wormer, picking up dung from stalls and small paddocks regularly helps control worm infection. Harrowing in mid summer can also can expose and kill worm larvae.

Any animals that are turned out with your horse should also be wormed. Cattle, sheep and goats can be infected by the small stomach worm, which also affects horses. Donkeys and mules get lungworm.

Avoid over grazing pasture and if possible rotate pasture. (This is not always feasible, especially at urban barns).


Most equine worms are 'stomach worms' (in fact, they generally live in the gut). Donkeys, however, commonly get lungworm.

A donkey with lungworm will have no symptoms even from a fairly heavy infection. Horses, however, will suffer extreme respiratory distress and can die from the infection. Lungworm is only normally found in horses pastured with donkeys or mules, as the worm cannot breed in horses. A broad spectrum wormer will normally kill it, but mysterious respiratory complaints in horses that are kept with donkeys or mules could be a sign of resistant lungworm and indicate that a change of wormer is necessary.

Treating a heavy infestation

A neglected horse may have a very heavy worm infestation. The temptation is to give them a massive dose of wormer to kill it.

Do not do it! The wormer will kill the worms...and then the dead worms will give the horse severe colic. Many horses have been rescued from bad situations by well meaning people only to be killed by an excessive dose of wormer.

If you have a horse that is in low body condition and has been neglected, work with your veterinarian. The vet may suggest a specific worming program with increasing doses or may give the horse corticosteroids to help reduce the risk of colic.

Things That Are Not Worms

Ringworm is a fungal infection of the skin. It is not a worm, but be careful - ringworm also infects humans.

Some people also think bots are a kind of worm, as they are a common stomach parasite. They're not. They're a kind of maggot, the larvae of the horse bot fly. However, they are vulnerable to ivermectin-based wormers. Botfly eggs are laid on the neck and shoulders of the horse and can often be found and removed when grooming.


    0 of 8192 characters used
    Post Comment

    • jenniferrpovey profile imageAUTHOR


      6 years ago

      Good additional points from Ann...particular for those of us who have drafts.

    • Ann1Az2 profile image


      6 years ago from Orange, Texas

      Good information. A good idea (at least on the Gulf Coast of Texas) is to get horses wormed by the Vet at least once or twice a year, and then worm them yourself in between. That way, they are apt to become less resistant to wormers, and they get the proper dosing. Importunately, wormers seldom go over 1200 lbs, so if you have a horse that weighs 1400 lbs, you have to buy more than one dose and split one. You also have a problem sometimes with minimum doses. Most wormers start at 500 or 600 lbs. If you have a pony that weighs less than that, you have to be careful not to overdose. Voted up.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)