Control of internal parasites Gastrointestinal Parasites of Horses is a cornerstone of equine management and a continual endeavor. Although anthelmintics Anthelmintics are the primary method of parasite control, other factors such as pasture management and stable environment are also important. Control programs should be tailored to each farm situation and require a cooperative program between the horse owner and the veterinarian. The principal internal parasites of horses are nematodes.
Unfortunately, anthelmintic resistance has arisen in many GI parasites of horses. Many species of adult cyathostomes have developed resistance to standard doses of the benzimidazoles and the tetrahydropyrimidines. Among intensively managed horse populations, treatment with macrocyclic lactones (eg, ivermectin, moxidectin) does not suppress strongyle egg counts for as long as previously expected. Among foals, weanlings, and even yearlings, there are increasing reports of ascarids becoming resistant to ivermectin and moxidectin.
A program to prevent anthelmintic resistance involves multiple parasites and multiple drug classes, and must consider horses of all ages. No single parasite control program is ideal for all horses. Age of the horse, population density, region of the country, climate, method of confinement (eg, stall or pasture), and pasture size and quality can affect the choice of parasite control programs. As horses age, they develop resistance to reinfection with certain parasites Strongyloides westeri-Associated Disease in Horses Strongyloides westeri is an intestinal threadworm commonly infecting young foals, and it has been associated with small intestinal enteritis, resulting in diarrhea. The pathogenicity... read more , such as Strongyloides westeri and Parascaris equorum. Resistance to most strongyles is incomplete.
The parasites of greatest concern in horses are large strongyles, small strongyles, roundworms, pinworms, stomach bots, and tapeworms. GI parasites can cause acute medical problems as well as chronic debilitation. They may be responsible for diarrhea, intestinal impactions or irritation (colic), and poor performance. The result can be slow growth in young horses, poor performance, acute bouts of colic, and death in severe instances.
The migrating ascarids (P equorum) are the primary cause of pulmonary inflammation and intestinal rupture in foals and weanlings. The control of large strongyles with improved anthelmintics has allowed the small strongyles (cyathostomes) to become a greater problem. Cecocecal or cecocolic intussusceptions caused by tapeworms have been reported.
The three currently available methods of diagnosing parasites are direct examination of feces, fecal flotation to determine concentrations of worm eggs, and culture of feces for infective larva. The direct examination method is quick but not always accurate. The flotation method for parasite egg concentration is more accurate to determine the type and number of parasites. The culture method is more suitable for laboratory use and research purposes. PCR has been described for detection of Strongylus vulgaris but is not yet available for clinical use.
The effectiveness of any parasite control program can be evaluated by fecal examination. The fecal examination should be done before administration of a particular dewormer and then again 14 days later. The amount of decrease in egg population will determine the effectiveness of the dewormer. Parasite egg counts that remain high after use of a particular dewormer indicate the presence of resistance and a need to change the control program.
The three major classes of anthelmintics available for parasite control in horses are the avermectins, benzimidazoles, and pyrantels.
The avermectins have a broad range of activity, are safe and effective at low doses, and control adult and migrating larval nematodes. Deworming of the mare immediately after foaling lessens the foal's exposure to parasites in the mare's manure. Avermectins are not effective against tapeworms; however, the combination of ivermectin with praziquantel is effective against tapeworms as well as large and small strongyles, ascarids, pinworms, and bots. The avermectins are effective against bot larva and are recommended in the fall after the botfly season.
The benzimidazoles (oxibendazole, fenbendazole, and oxfendazole) are effective against most nematodes but not against encysted small strongyles or tapeworms.
The pyrantels are effective against large and small strongyles, ascarids, and pinworms. Pyrantels kill nematode parasites slowly. Pyrantels are available as a paste (single dose) and as a tartrate salt that can be administered as a daily dewormer mixed in the feed; it is effective against tapeworms but not bots.
A fourth class of anthelmintics, the isoquinolines, contains praziquantel, a narrow-spectrum drug approved for horses as a cestocide. Praziquantel is available in combination with either ivermectin or moxidectin.
To slow the development of drug-resistant parasites, the focus of most parasite control programs is to decrease selection pressure for resistance by customizing deworming protocols for the farm and individual horses. This strategy includes identifying horses most susceptible to parasites (ie, the high egg shredders) and maximizing refugia (those parasites not exposed to drug selection pressure) by decreasing the overall number of anthelmintic treatments administered and by monitoring the efficacy of different classes of dewormers using the fecal egg count reduction test.
An effective deworming protocol for horses should incorporate a cestocide (eg, a praziquantel-containing product or a double dose of pyrantel pamoate) and a boticide (eg, ivermectin or moxidectin) once or twice a year to control tapeworms and bots, respectively, and a larvicidal dose of anthelmintic effective against encysted cyathostomes (eg, fenbendazole 10 mg/kg/day, PO, for 5 days, or a single dose of moxidectin) during early winter months in northern climates or during early summer in warmer climates.
Foals should be maintained on a regular deworming schedule every 60 days that includes anthelmintics safe and effective against ascarids. Treatments effective against other nematodes (including encysted cyathostomes) and cestodes should be included in the deworming protocols for foals during the first year of life.
Effective deworming programs should also include one or more of the following nonchemical methods of parasite control:
Avoid overstocking and overgrazing pastures.
Keep pasture roughs mowed to a height of 3–8 inches.
During hot, dry weather, harrow or rake pastures to disperse manure piles and expose larvae to sun.
Cross-graze pastures with other species. Cattle, sheep, and goats serve as biological vacuums for equine parasites.
Make at least one cutting of hay from some pastures, to help decrease the parasite burden.
Plant an annual crop such as winter wheat.
Feed hay and grain in raised containers and not directly on the ground.
Remove manure from stalls, paddocks, and pastures every 24–72 hours before strongyle eggs have a chance to hatch and develop into infective larvae (5–7 days during optimal conditions).
Clean water sources regularly to prevent fecal contamination.
Quarantine new arrivals and perform fecal examinations. Use a larvicidal treatment before turning out new arrivals on pastures.
Use fecal egg counts, performed at the proper times, to identify and monitor high, medium, and low strongyle egg shedders, to monitor the efficacy of anthelmintics, and to evaluate new arrivals.
Compost manure. Properly composted manure will kill strongyle larvae and many ascarid eggs.
Kudhibiti vimelea vya ndani vya gastrointestinal ni msingi wa usimamizi wa farasi na juhudi ya kuendelea. Ingawa anthelmintics ni njia ya msingi ya udhibiti wa vimelea, mambo mengine kama vile usimamizi wa malisho na mazingira thabiti pia ni muhimu. Programu za kudhibiti zinapaswa kubadilishwa kulingana na hali ya kila shamba na zinahitaji mpango wa ushirikiano kati ya mmiliki wa farasi na daktari wa mifugo. Vimelea vikuu vya ndani vya farasi ni nematodes. Kwa kusikitisha, vimelea vingi vya tumbo la tumbo la farasi vimeathiriwa na dawa za kuua wadudu. Spishi nyingi za cyathostomes za watu wazima zimeendeleza upinzani kwa vipimo vya kawaida vya benzimidazoles na tetrahydropyrimidines. Katika idadi ya farasi wanaotunzwa kwa bidii, matibabu na lactones macrocyclic (kwa mfano, ivermectin, moxidectin) haizuii hesabu ya mayai ya strongyle kwa muda mrefu kama ilivyotarajiwa hapo awali. Miongoni mwa ndama, watoto waliozaliwa baada ya kupooza, na hata watoto wa mwaka mmoja, kuna ripoti zinazozidi kuongezeka za ascarids kuwa sugu kwa ivermectin na moxidectin. Programu ya kuzuia upinzani wa anthelmintic inahusisha vimelea vingi na madarasa mengi ya dawa, na lazima ichukue farasi wa umri wote. Hakuna programu moja ya kudhibiti vimelea inayofaa farasi wote. Umri wa farasi, idadi ya watu, eneo la nchi, hali ya hewa, njia ya kufungwa (kwa mfano, kibanda au malisho), na ukubwa wa malisho na ubora inaweza kuathiri uchaguzi wa mipango ya udhibiti wa vimelea. Kwa sababu ya umri, farasi huendelea kuathiriwa na vimelea vya aina mbalimbali, na kwa sababu ya ugonjwa wa Strongyloides westeris, ambao ni ugonjwa wa tumbo la ndani unaoathiri farasi wadogo, na ambao huathiri pia tumbo dogo. Ugonjwa huo unajulikana kama Strongyloides westerner na Parascaris equorum. Upinzani kwa strongyles wengi ni kamili. Vimelea vinavyosababisha wasiwasi mkubwa kwa farasi ni vimelea vikubwa, vimelea vidogo, vimelea vilivyozunguka, vimelea vya mkojo, vimelea vya tumbo, na vimelea vya mkanda. Vimelea vya utumbo wa tumbo vinaweza kusababisha matatizo ya matibabu ya haraka na vilevile kupooza kwa muda mrefu. Wanaweza kusababisha kuhara, kuambukizwa kwa matumbo au kuchochewa (koliki), na utendaji mbaya. Matokeo yanaweza kuwa ukuzi wa polepole kwa farasi wachanga, utendaji duni, milipuko mikali ya colic, na kifo katika visa vikali. Ascarids wanaohama (P equorum) ndio kisababishi kikuu cha uvimbe wa mapafu na kuvunjika kwa matumbo kwa ng'ombe-dume na watoto wachanga. Kudhibiti strongyles kubwa na anthelmintics kuboreshwa imeruhusu strongyles ndogo (cyathostomes) kuwa tatizo kubwa zaidi. Inasemekana kwamba minyoo ya mviringo husababisha uvimbe wa mviringo au uvimbe wa mviringo. Njia tatu zinazopatikana kwa sasa za kugundua vimelea ni uchunguzi wa moja kwa moja wa matumbo, kuteleza kwa matumbo ili kuamua mkusanyiko wa mayai ya minyoo, na utamaduni wa matumbo kwa larva ya maambukizi. Njia ya uchunguzi wa moja kwa moja ni ya haraka lakini si sahihi sikuzote. Njia ya kuelea kwa ajili ya mayai ya vimelea mkusanyiko ni sahihi zaidi kuamua aina na idadi ya vimelea. Mbinu ya utamaduni ni bora kwa ajili ya matumizi ya maabara na madhumuni ya utafiti. PCR imetajwa kwa ajili ya kugundua Strongylus vulgaris lakini bado haipatikani kwa ajili ya matumizi ya kliniki. Ufanisi wa programu yoyote ya kudhibiti vimelea waweza kutathminiwa kwa kuchunguza matope. Uchunguzi wa mkojo unapaswa kufanywa kabla ya utoaji wa dewermer maalum na kisha tena siku 14 baadaye. Kiasi cha kupungua kwa idadi ya mayai itabainisha ufanisi wa dewermer. Idadi ya mayai ya vimelea ambayo inabaki juu baada ya matumizi ya dewermer maalum inaonyesha uwepo wa upinzani na haja ya kubadilisha programu ya udhibiti. Aina tatu kuu za dawa za kuua vimelea zinazopatikana kwa ajili ya kudhibiti vimelea katika farasi ni avermectins, benzimidazoles, na pyrantels. Avermectin ina shughuli nyingi, ni salama na yenye ufanisi kwa kipimo cha chini, na kudhibiti nematodes za watu wazima na za mabuu zinazohama. Kuondoa minyoo kwenye farasi mara tu baada ya kuzaa, hupunguza uwezekano wa farasi huyo kuambukizwa vimelea vilivyo katika mbolea ya farasi. Avermectin ni moja ya dawa za kuua minyoo wa bandia, lakini inasaidia kuua minyoo wa bandia, ascarids, na wadudu wengine. Avermectins ni ufanisi dhidi ya mabuu ya bot na inapendekezwa katika vuli baada ya msimu wa botfly. Benzimidazoles (oxibendazole, fenbendazole, na oxfendazole) ni yenye matokeo dhidi ya nematodes nyingi lakini si dhidi ya encysted strongyles ndogo au tapeworms. Pyrantels ni yenye matokeo dhidi ya strongyles kubwa na ndogo, ascarids, na pinworms. Pyrantels huua vimelea vya nematodi polepole. Pyrantel inapatikana kama mchanganyiko (kiwango kimoja) na kama chumvi ya tartrate ambayo inaweza kutolewa kama dewermer ya kila siku iliyochanganywa katika chakula; ni ufanisi dhidi ya minyoo ya bendi lakini si bots. Dawa ya nne ya kuzuia vimelea, i.e., isoquinolines, ina praziquantel, dawa yenye athari ndogo ambayo imeidhinishwa kwa ajili ya farasi kama dawa ya kuua wadudu. Praziquantel inapatikana pamoja na ivermectin au moxidectin. Ili kupunguza maendeleo ya vimelea vya dawa, lengo la programu nyingi za udhibiti wa vimelea ni kupunguza shinikizo la uteuzi kwa upinzani kwa kubadilisha itifaki za kuondoa minyoo kwa shamba na farasi mmoja mmoja. Mkakati huu unatia ndani kutambua farasi walio na uwezekano mkubwa wa kuambukizwa na vimelea (yaani, wale wanaokata mayai kwa kiasi kikubwa) na kuongeza idadi ya vimelea (vimelea ambavyo havijafunikwa na shinikizo la kuchagua dawa) kwa kupunguza idadi ya matibabu ya antihelmintic na kwa kufuatilia ufanisi wa madarasa tofauti ya dawa za kuua minyoo kwa kutumia mtihani wa kupunguza idadi ya mayai. Kwa ajili ya farasi, utaratibu wa kuondoa minyoo unapaswa kujumuisha cestocide (kwa mfano, bidhaa yenye praziquantel au kipimo mara mbili cha pyrantel pamoate) na boticide (kwa mfano, ivermectin au moxidectin) mara moja au mara mbili kwa mwaka ili kudhibiti minyoo ya mviringo na bots, na kipimo cha larvicidal cha antihelmintic inayofaa dhidi ya encystedatochthyloid (kwa mfano, cybendazole 10mg kwa siku 5 au kipimo kimoja cha moxidectin) wakati wa miezi ya mapema ya majira ya baridi katika hali ya hewa ya kaskazini. Kwa hivyo, kwa sababu ya hali hii, ni muhimu kuwa na mpango wa kawaida wa kuondoa minyoo kila baada ya siku 60 na kutumia dawa za kuua wadudu (anthelmintics) ambazo ni salama na zina ufanisi dhidi ya ascarids. Matibabu yenye ufanisi dhidi ya nematodes nyingine (ikiwa ni pamoja na cyathostomes encysted) na cestodes inapaswa kuingizwa katika itifaki za kuondoa minyoo kwa foals wakati wa mwaka wa kwanza wa maisha. Programu za kuondoa vimelea zinapaswa pia kujumuisha moja au zaidi ya mbinu zifuatazo zisizo za kemikali za kudhibiti vimelea: Kuepuka kuhifadhi na kulisha kwa wingi malisho. Kuhifadhi malisho roughs mowed kwa urefu wa 3 8 inchi. Wakati wa hali ya hewa ya joto na kavu, chonga au chonga malisho ili kutawanya rundo la mbolea na kufunua mabuu kwa jua. Mimea ya malisho ya msalaba na spishi nyingine. Ng'ombe, kondoo, na mbuzi hutumika kama mahali pa kuondoa vimelea vya farasi. Fanya angalau upunguzaji mmoja wa nyasi kutoka kwa malisho fulani, ili kusaidia kupunguza mzigo wa vimelea. Panda mazao ya kila mwaka kama vile ngano ya majira ya baridi kali. Kulisha nyasi na nafaka katika vyombo vilivyoinuliwa na si moja kwa moja ardhini. Kuondoa mbolea kutoka kwa maghala, paddocks, na malisho kila masaa 24-72 kabla ya mayai ya strongyle kuwa na nafasi ya kuanguliwa na kuendeleza katika larvae ya kuambukiza (siku 5-7 wakati wa hali bora). Safisha vyanzo vya maji kwa ukawaida ili kuzuia uchafuzi wa matope. Wahamiaji wapya wawekwa karantini na kufanyiwa uchunguzi wa matumbo. Tumia matibabu ya kuua mabuu kabla ya kugeuza wageni waliowasili kwenye malisho. Kwa kutumia hesabu ya mayai ya fecal, kufanywa kwa wakati unaofaa, kutambua na kufuatilia high, kati, na chini strongyle shedders ya mayai, kufuatilia ufanisi wa anthelmintics, na kutathmini kuwasili mpya. Mbolea ya mbolea. Mbolea iliyotiwa mbolea ifaavyo itaua mabuu ya mnyama huyo na mayai mengi ya ascarid.