b'Practical Parasite Controllarvae emerging at once, inducing a huge inflammatory response in his gastrointes-tinal tract. Luckily, if treated quickly, these horses do well after a course of fenbenda-zole (from the benzimidazole deworming drug class) or moxidectin (a macrocyclic lactone). Vets are seeing small-strongyle resistance to other anthelminthic drugs, which are no longer useful for treatment. Roundworms (ascarids) Known as the ascarid, Parascarus equorum is primarily a parasite of foals. Its very resistant to extreme weather and can withstand freez-ing temperatures and dry heat. Because they cause disease in foals, ascarids are common on breeding farms. PAULA DA SILVAAffected youngsters can appear unthrifty, experience weight loss, and have a pot-bellied appearance. Furthermore, ascarid Collect horses fecal samples pre- and post-deworming and run fecal egg counts each year.migrations through the thorax can cause respiratory disease. A problem veterinarians face whenPinworms Unlike many equine para- can cause infected horses intense itching. they suspect a roundworm infection issites, Oxyuris equi worms are not knownDead microfilaria, especially, are horren-how to treat it, because a drench (large)to cause weight loss and unthrifty condi- dously itchy, often causing the horse to dose can result in a catastrophe. Yes, thetions. Instead, they settle at the very endself-mutilate. Treatment with moxidectin parasites die off quickly, but they can dieof the intestinal tract, laying eggs aroundor ivermectin (another macrocyclic lac-off so quickly that they cause a second- the rectum that cause intense itching. Atone), however, usually clears the clinical ary intestinal impaction. Benzimidazolesrubbed-raw tailhead is often the hallmarksigns. carry less risk of a massive die-off and,of this infection. Thankfully, O. equiNote that threadworm lesions can look therefore, veterinarians often recommendworms have not developed much anthel- like a few other conditions, including can-them for treating roundworm infections.mintic resistance, and most dewormerscer, pythiosis (a skin infection caused by Tapeworms These worms differ fromshould cure the infection.a funguslike microorganism), and proud many others because they are not nema- flesh. Occasionally, your veterinarian will todes. Officially known as Anoplocephalaneed to take a biopsy to make a definitive perfoliata, these parasites commonlyDeworming in verydiagnosis of threadworm infection. cause weight loss and emaciation in hors- Large strongyles The parasite of yester-es. Tapeworm infections can also causecold or very hotyear, large strongyles wreaked havoc on colic. These worms attach at the ileocecalmonths, when the para- the equine industry in the 1950s and 60s. junction, where the end of the small intes- sites are dormant, is aYears ago, large strongyles were a sig-tine meets the cecum and horses fermentnificant issue and a leading cause of colic their food. Severe infections can lead towaste of medication.and death in horses, says Olds-Sanchez. cecal impactions. Recent study resultsDR. ALLISON WILLIARD Strongylus vulgaris was the main culprit. suggest that almost all ileocecal intussus- These parasites are active blood feeders, ceptions (where one part of the gastroin- leaving affected horses weak, anemic, testinal tract telescopes into another) areNeck Threadworms Onchocerca cervi- and emaciated. Their migration patterns associated with tapeworm infections.calis worms make your horses neck theirthrough blood vessels can also result in Fecal egg counts rarely detect tape- home. Adults embed themselves in thethromboembolism, causing death in an worm eggs. A blood test is available tohorses nuchal ligament, the fleshy attach- unlucky few. screen for infections, but authors of thement that runs from the withers to theThe introduction of effective deworm-current American Association of Equinepoll. Adult threadworms often cause noers was great for equine health in that we Practitioners recommendations suggestissues, aside from some mineralizationhad a prevention or treatment for large treating horses at least twice a year for A.of the nuchal ligament. When the wormsstrongyles, Olds-Sanchez adds. perfoliata. Praziquantel (another macro- reproduce, however, problems arise.Bots As opposed to the parasites de-cyclic lactone) anthelminthics are readilyAfter breeding, microfilaria (larvae)scribed throughout the rest of this article, available to rid your horse of tapewormget released and migrate under the skinbots are the larvae of the Gasterophilus, infection but should be used sparinglyto settle in the bottommost aspect ofor botfly. These flies lay their eggs on the due to early evidence of small strongylethe chest and abdomen, where flies arehorses legs and chest. When horses go resistance to this dewormer class.abundant. Their travels through the neckto scratch their limbs, as the eggs can 26April 2020The Horse|TheHorse.com'