Equine Helminths
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Questions and Answers

What is the primary method of diagnosing cutaneous habronemiasis?

  • Identifying larvae in skin scrapings or biopsies (correct)
  • Blood tests to check for antibodies
  • Clinical observation of symptoms over time
  • Monitoring for adult worms during a gastroscopy

    • Which anthelmintic is commonly used to treat equine stomach worms?

  • Fenbendazole
  • Moxidectin (correct)
  • Praziquantel
  • Ivermectin

    • What additional treatment may be necessary in severe cases of summer sores?

  • Intravenous fluids
  • Antibiotic therapy
  • Surgical removal or cauterization (correct)
  • Vaccination

    • What is a crucial control measure to reduce exposure to equine stomach worm larvae?

    <p>Implementing fly management around wounds</p> Signup and view all the answers

    Which of the following is true regarding zoonotic concerns with equine stomach worms?

    <p>Equine stomach worms have no significant zoonotic concerns</p> Signup and view all the answers

    What order do Draschia megastoma, Habronema muscae, and Habronema microstoma belong to?

    <p>Spirurida</p> Signup and view all the answers

    Which equine stomach worm is known to cause the most severe clinical lesions?

    <p>Draschia megastoma</p> Signup and view all the answers

    What is the main intermediate host in the life cycle of these equine stomach worms?

    <p>Muscid flies</p> Signup and view all the answers

    What is the prepatent period for the development of adult worms after infection?

    <p>2 months</p> Signup and view all the answers

    Which clinical sign is most likely associated with heavy infections of equine stomach worms?

    <p>Gastritis</p> Signup and view all the answers

    What condition results from L3 larvae being deposited on wounds or moist skin?

    <p>Cutaneous habronemiasis</p> Signup and view all the answers

    How are equine stomach worms typically diagnosed?

    <p>Molecular methods</p> Signup and view all the answers

    Where do Draschia megastoma adult worms reside within the horse's body?

    <p>Stomach</p> Signup and view all the answers

    What is the primary age group affected by Parascaris equorum?

    <p>Nursing and weaned foals under one year old</p> Signup and view all the answers

    Which of the following clinical signs is NOT associated with heavy infections of Parascaris equorum?

    <p>Excessive growth</p> Signup and view all the answers

    How does the pathology of Parascaris equorum vary with worm burden?

    <p>Heavy infections result in intestinal impaction and rupture</p> Signup and view all the answers

    What is the recommended treatment approach for foals with heavy infections of Parascaris equorum?

    <p>Gradual deworming protocol</p> Signup and view all the answers

    Which diagnostic method is commonly used to identify Parascaris equorum?

    <p>Fecal flotation to identify eggs</p> Signup and view all the answers

    What environmental control measure is important for managing Parascaris equorum contamination?

    <p>Regular manure removal</p> Signup and view all the answers

    What type of lesions might be observed in the liver due to larval migration of Parascaris equorum?

    <p>Milk spots similar to those in pigs</p> Signup and view all the answers

    Which statement about the zoonotic potential of Parascaris equorum is true?

    <p>No significant zoonotic concerns are associated</p> Signup and view all the answers

    What is the primary clinical sign associated with Strongyloides westeri infections in foals?

    <p>Watery diarrhea</p> Signup and view all the answers

    Which life cycle characteristic is unique to Strongyloides westeri?

    <p>It alternates between parasitic and free-living forms.</p> Signup and view all the answers

    How does Strongyloides westeri primarily transmit from the mare to the foal?

    <p>Through mare's milk.</p> Signup and view all the answers

    What method is most effective in diagnosing Strongyloides westeri?

    <p>Fecal flotation</p> Signup and view all the answers

    What type of medication is commonly used to treat Strongyloides westeri infections?

    <p>Anthelmintics</p> Signup and view all the answers

    Which of the following statements is true regarding the zoonotic potential of Strongyloides westeri?

    <p>It is not known to be zoonotic.</p> Signup and view all the answers

    What specific feature of Parascaris equorum distinguishes it from Strongyloides westeri?

    <p>It has a direct life cycle with long-lived infective eggs.</p> Signup and view all the answers

    What happens to Strongyloides westeri eggs or larvae that are passed in the feces?

    <p>They develop into either free-living adults or infective larvae.</p> Signup and view all the answers

    What are Strongylus spp. primarily classified as?

    <p>Nematodes</p> Signup and view all the answers

    What is the primary location where Strongylus vulgaris larvae migrate after ingestion?

    <p>Cranial mesenteric artery</p> Signup and view all the answers

    Which species of Strongylus has a prepatent period of 6 months?

    <p>Strongylus vulgaris</p> Signup and view all the answers

    What clinical sign is most commonly associated with Strongylus spp. infection in horses?

    <p>Dependent edema</p> Signup and view all the answers

    Which of the following migrations is generally harmless compared to Strongylus vulgaris?

    <p>Strongylus edentatus to the liver</p> Signup and view all the answers

    How is a Strongylus spp. infection typically diagnosed?

    <p>Fecal egg counts and clinical signs</p> Signup and view all the answers

    What is a consequence of S.vulgaris larvae's migration in horses?

    <p>Colic due to mesenteric artery thrombosis</p> Signup and view all the answers

    Where do Strongylus equinus larvae migrate to after leaving the peritoneal cavity?

    <p>Pancreas and liver</p> Signup and view all the answers

    What is the primary clinical sign of an Oxyuris equi infection in horses?

    <p>Intense itching around the tail</p> Signup and view all the answers

    How does a horse become infected with Oxyuris equi?

    <p>By ingesting eggs with infective L3 larvae</p> Signup and view all the answers

    What is the duration of the prepatent period for Oxyuris equi?

    <p>5 months</p> Signup and view all the answers

    What treatment is commonly used for controlling Oxyuris equi infection in horses?

    <p>Ivermectin</p> Signup and view all the answers

    Which method is used to diagnose Oxyuris equi infection?

    <p>Scotch tape test</p> Signup and view all the answers

    What is the potential consequence of hair loss due to excessive rubbing from Oxyuris equi infection?

    <p>Secondary bacterial infections</p> Signup and view all the answers

    What is the shape and structure of Oxyuris equi eggs?

    <p>Elongated, oval with a flattened side and operculum</p> Signup and view all the answers

    What hygiene measure is important for controlling Oxyuris equi infection?

    <p>Cleaning the perianal area and disinfecting the environment</p> Signup and view all the answers

    What is a primary consequence of hypobiosis in small strongyle infections?

    <p>Larvae can survive unfavorable conditions until favorable ones return.</p> Signup and view all the answers

    Which category of horses is at the highest risk of small strongyle infections?

    <p>Young horses under five years old.</p> Signup and view all the answers

    What is the prepatent period for small strongyles?

    <p>6-12 weeks</p> Signup and view all the answers

    What method is vital for diagnosing minor strongyle infections?

    <p>Fecal egg counts (FEC).</p> Signup and view all the answers

    Which clinical sign is most likely observed during heavy infections of small strongyles in horses?

    <p>Unthriftiness</p> Signup and view all the answers

    How do small strongyles primarily differ from large strongyles?

    <p>Small strongyles do not migrate outside the gastrointestinal tract</p> Signup and view all the answers

    What is a key treatment option for small strongyle infections?

    <p>Use of anthelmintics like ivermectin.</p> Signup and view all the answers

    How can small strongyle infections best be controlled?

    <p>Good pasture management and manure removal.</p> Signup and view all the answers

    What is the primary consequence of mass emergence of encysted larvae from small strongyles?

    <p>Severe diarrhea and colitis</p> Signup and view all the answers

    What is the implication of low or negative fecal egg counts in diagnosing larval cyathostominosis?

    <p>The horse may be an intermittent shedder.</p> Signup and view all the answers

    What typically occurs to small strongyles after they are ingested by horses?

    <p>They enter the mucosa of the cecum and colon</p> Signup and view all the answers

    What is hypobiosis in the context of small strongyles?

    <p>A period of arrested development</p> Signup and view all the answers

    What is a significant challenge in the treatment of small strongyles?

    <p>Resistance development to some anthelmintics.</p> Signup and view all the answers

    Are small strongyle infections considered zoonotic?

    <p>No, they are specific to equines only.</p> Signup and view all the answers

    What pathology is associated with the emergence of a large number of encysted small strongyles?

    <p>Severe damage to the intestinal mucosa</p> Signup and view all the answers

    What happens to small strongyle eggs after they are passed in feces?

    <p>They hatch into L1 larvae and develop further</p> Signup and view all the answers

    What is the main reason Anoplocephala perfoliata diagnosis is challenging?

    <p>Eggs are not consistently shed in the feces.</p> Signup and view all the answers

    What is included in the treatment plan for Anoplocephala perfoliata?

    <p>Praziquantel or a double dose of pyrantel pamoate.</p> Signup and view all the answers

    How can horses be effectively protected from Anoplocephala perfoliata infections?

    <p>By managing pasture conditions to reduce mite exposure.</p> Signup and view all the answers

    Which diagnostic method can improve the accuracy of identifying Anoplocephala perfoliata?

    <p>Fecal egg counts using modified flotation techniques.</p> Signup and view all the answers

    What public health concern is associated with Anoplocephala perfoliata?

    <p>There are no zoonotic concerns associated with this tapeworm.</p> Signup and view all the answers

    What is the primary intermediate host for Anoplocephala perfoliata?

    <p>Oribatid mite</p> Signup and view all the answers

    Where do Anoplocephala perfoliata tapeworms most commonly attach within the horse's intestines?

    <p>Ileocecal junction</p> Signup and view all the answers

    What clinical sign is commonly associated with heavy infections of Anoplocephala perfoliata?

    <p>Colic</p> Signup and view all the answers

    What period does it typically take for Anoplocephala perfoliata to reach maturity within the horse after infection?

    <p>6-10 weeks</p> Signup and view all the answers

    Which of the following conditions is NOT associated with Anoplocephala perfoliata infections?

    <p>Appendicitis</p> Signup and view all the answers

    Which group of horses is at heightened risk for clinical disease related to Anoplocephala perfoliata?

    <p>Young horses and those with poor pasture management</p> Signup and view all the answers

    What type of damage does Anoplocephala perfoliata cause to the intestinal mucosa?

    <p>Local inflammation and damage</p> Signup and view all the answers

    What is the key difference in clinical signs of Dictyocaulus arnfieldi infection between donkeys and horses?

    <p>Donkeys may be heavily infected but usually do not show clinical signs.</p> Signup and view all the answers

    Which method is effective for diagnosing lungworm infection in horses?

    <p>Identification of L1 larvae in fresh feces using the Baermann technique.</p> Signup and view all the answers

    What is a recommended strategy to control Dictyocaulus arnfieldi infection in equines?

    <p>Separating grazing areas for horses and donkeys.</p> Signup and view all the answers

    What is a common misconception about the zoonotic potential of Dictyocaulus arnfieldi?

    <p>It does not pose a zoonotic risk and is specific to equines.</p> Signup and view all the answers

    Which of the following anthelmintics is effective against Dictyocaulus arnfieldi infection?

    <p>Ivermectin.</p> Signup and view all the answers

    What is the main host species for Dictyocaulus arnfieldi?

    <p>Donkeys</p> Signup and view all the answers

    What are the typical clinical signs of Dictyocaulus arnfieldi infection in horses?

    <p>Coughing and nasal discharge</p> Signup and view all the answers

    What unique lifecycle characteristic does Dictyocaulus arnfieldi demonstrate?

    <p>Direct life cycle without intermediate hosts</p> Signup and view all the answers

    What is the prepatent period for Dictyocaulus arnfieldi?

    <p>4 weeks</p> Signup and view all the answers

    Which of the following consequences can arise from a heavy infection of Dictyocaulus arnfieldi in horses?

    <p>Airway obstruction and inflammation</p> Signup and view all the answers

    Why are donkeys considered reservoirs for Dictyocaulus arnfieldi?

    <p>They are often asymptomatic carriers shedding larvae</p> Signup and view all the answers

    What happens to L1 larvae of Dictyocaulus arnfieldi after being passed in feces?

    <p>They develop into infective L3 larvae in the environment</p> Signup and view all the answers

    What is a common pathology associated with Dictyocaulus arnfieldi infection in horses?

    <p>Bronchitis and excess mucus production</p> Signup and view all the answers

    What is the primary treatment for Onchocerca spp. infections?

    <p>Moxidectin</p> Signup and view all the answers

    What method can be used to confirm the presence of Onchocerca DNA?

    <p>PCR testing</p> Signup and view all the answers

    What is a crucial aspect of controlling Onchocerca spp. infections?

    <p>Reducing standing water</p> Signup and view all the answers

    Which statement regarding the zoonotic potential of Onchocerca spp. is true?

    <p>It is exclusively found in equines and does not affect humans.</p> Signup and view all the answers

    Why might surgical removal be necessary in Onchocerca spp. treatment?

    <p>To eliminate adult worm nodules</p> Signup and view all the answers

    What is the primary habitat of adult Onchocerca spp. in horses?

    <p>Connective tissues</p> Signup and view all the answers

    Which species of vector is primarily associated with the transmission of Onchocerca spp.?

    <p>Culicoides species</p> Signup and view all the answers

    Which clinical sign is associated with Onchocerca spp. infection in horses?

    <p>Uveitis</p> Signup and view all the answers

    What is the typical duration of the prepatent period for Onchocerca spp. after infection?

    <p>4-6 months</p> Signup and view all the answers

    What type of life cycle do Onchocerca spp. exhibit?

    <p>Indirect life cycle</p> Signup and view all the answers

    Which pathology associated with Onchocerca spp. is primarily due to microfilariae in the skin?

    <p>Localized inflammation</p> Signup and view all the answers

    Which Onchocerca spp. is primarily of relevance to donkeys in Africa?

    <p>Onchocerca railliti</p> Signup and view all the answers

    Which condition may result from chronic Onchocerca spp. infections in horses?

    <p>Fistulous withers</p> Signup and view all the answers

    What is the primary consequence of larvae being deposited on a horse's skin by flies?

    <p>They cause granulomatous skin lesions.</p> Signup and view all the answers

    Which clinical signs are characteristic of cutaneous habronemiasis?

    <p>Granulomatous, ulcerative skin lesions.</p> Signup and view all the answers

    What role do houseflies and stable flies play in the life cycle of Habronema spp.?

    <p>They facilitate the transfer of infective larvae.</p> Signup and view all the answers

    How does the immune response to larvae in the skin manifest in horses affected by cutaneous habronemiasis?

    <p>By causing a granulomatous inflammation.</p> Signup and view all the answers

    What treatment options are available for managing cutaneous habronemiasis?

    <p>Systemic anthelmintics and topical corticosteroids.</p> Signup and view all the answers

    Why might cutaneous habronemiasis become a chronic condition if untreated?

    <p>Secondary bacterial infections can complicate healing.</p> Signup and view all the answers

    Which environment is most likely to facilitate the transmission of Habronema spp. larvae?

    <p>Warm, moist conditions with abundant flies.</p> Signup and view all the answers

    What is a common method for diagnosing cutaneous habronemiasis?

    <p>Identifying larvae in skin scrapings or biopsies.</p> Signup and view all the answers

    What is the primary method for treating Thelazia lacrymalis infections?

    <p>Manual removal of worms using fine forceps</p> Signup and view all the answers

    Which of the following is NOT a preventive measure for Thelazia lacrymalis?

    <p>Conducting regular eye examinations</p> Signup and view all the answers

    How can Thelazia lacrymalis be diagnosed?

    <p>Direct observation of adult worms in the eye</p> Signup and view all the answers

    What zoonotic risk is associated with Thelazia lacrymalis?

    <p>Thelazia lacrymalis is not known to infect humans.</p> Signup and view all the answers

    Which treatment is effective in eliminating any remaining larvae or worms after manual removal in Thelazia lacrymalis cases?

    <p>Ivermectin</p> Signup and view all the answers

    What is the primary natural habitat of Thelazia lacrymalis in horses?

    <p>Conjunctival sac and tear ducts</p> Signup and view all the answers

    Which of the following best describes the life cycle of Thelazia lacrymalis?

    <p>Indirect life cycle involving flies</p> Signup and view all the answers

    What clinical signs are indicative of Thelazia lacrymalis infection in horses?

    <p>Excessive tearing and photophobia</p> Signup and view all the answers

    How can Thelazia lacrymalis infection primarily be prevented in horses?

    <p>Implementing effective fly control measures</p> Signup and view all the answers

    What is the prepatent period for Thelazia lacrymalis in horses?

    <p>3-6 weeks</p> Signup and view all the answers

    What is a potential consequence of prolonged Thelazia lacrymalis infection in horses?

    <p>Corneal damage and vision impairment</p> Signup and view all the answers

    Which group of horses is most susceptible to Thelazia lacrymalis infection?

    <p>Horses in areas with high fly populations</p> Signup and view all the answers

    What impact does Thelazia lacrymalis have on the horse's eye?

    <p>It primarily causes irritation and inflammation</p> Signup and view all the answers

    Study Notes

    Classification and Prevalence

    • Draschia megastoma, Habronema muscae, and Habronema microstoma are classified as nematodes in the order Spirurida.
    • These parasites are commonly known as equine stomach worms.
    • Habronema muscae is the most prevalent species among the three.
    • Draschia megastoma is responsible for the most severe clinical lesions, including large stomach nodules filled with necrotic material.
    • Habronema microstoma has not been reported in America.

    Life Cycle

    • The life cycle is indirect, involving flies as intermediate hosts.
    • Adult worms inhabit the horse's stomach and release eggs or L1 larvae, which are ingested by Muscid flies.
    • The larvae develop into the infective L3 stage within the fly.
    • If L3 larvae are deposited around the horse's mouth, they are ingested and mature into adults in the stomach.
    • If the larvae are placed on wounds or moist skin, they result in cutaneous lesions but do not mature into adult worms.
    • The prepatent period, from infection to adult worm development, is approximately 2 months.

    Clinical Presentation (Ingestion of Larvae)

    • Most horses remain asymptomatic upon ingesting infective L3 larvae.
    • Heavy infections can lead to gastritis.
    • Draschia megastoma causes severe lesions, forming nodules in the stomach that can reach 10 cm in diameter, containing numerous worms and necrotic tissue.
    • Nodules may cause mechanical obstruction or rupture, risking fatal peritonitis.
    • The parasites are linked to Rhodococcus equi, a pneumonia pathogen in foals.

    Clinical Presentation (Deposited on Wounds)

    • L3 larvae on wounds or moist skin can lead to cutaneous habronemiasis (summer sores).
    • Lesions are characterized by granulomatous, itchy, reddish-brown, and greasy areas with yellow, calcified material resembling rice grains.
    • Common sites for skin lesions include legs, face, and near the eyes.

    Diagnosis

    • Diagnosing equine stomach infections is challenging; eggs are not typically identified in routine fecal flotation.
    • Molecular diagnostic methods exist but are seldom employed.
    • Adult worms or lesions can be detected via gastroscopy or necropsy.
    • Diagnosis of cutaneous habronemiasis is performed by identifying larvae in skin scrapings or biopsies.

    Treatment and Control

    • Stomach infections are treated with anthelmintics such as moxidectin.
    • For summer sores, oral or topical moxidectin may be effective, while severe cases might require surgical removal or cauterization of excessive granulation tissue.
    • Control strategies primarily involve managing fly populations around wounds to minimize larval exposure.

    Zoonotic Concerns

    • There are no significant zoonotic risks associated with Draschia megastoma, Habronema muscae, or Habronema microstoma; these parasites are specific to equines and do not pose a risk to humans.

    Strongyloides westeri Classification and Characteristics

    • Strongyloides westeri is a nematode belonging to the order Rhabditida, commonly known as the equine threadworm.
    • Parasitic females exclusively reside within the host, with eggs or larvae expelled in feces.

    Strongyloides westeri Life Cycle

    • The life cycle involves direct transmission but is complex, alternating between parasitic and free-living forms.
    • Eggs or larvae develop in the environment into free-living adults or infective L3 larvae.
    • L3 larvae can penetrate skin or be ingested and then migrate to the small intestine to mature into adult females.
    • Transmission can also occur through mare's milk, where larvae reactivated during parturition are passed to foals.

    Clinical Presentation in Foals

    • Primarily affects foals, causing small intestinal enteritis, diarrhea, and skin irritation from larval penetration.
    • Common clinical signs include watery diarrhea, weight loss, dehydration, and behavior termed "frenzied behavior" due to skin irritation.
    • Adult horses typically show no clinical symptoms.

    Diagnosis of Strongyloides westeri

    • Diagnosis involves identifying eggs in feces through flotation methods; eggs are small, oval, and thin-shelled, often containing larvae.
    • Skin scraping may help identify larvae in cases of dermal invasion.

    Treatment and Control Measures

    • Infected foals are treated with anthelmintics such as ivermectin or fenbendazole.
    • To prevent transmission, mares should receive ivermectin treatment within 24 hours of foaling.
    • Maintaining a clean and dry environment is crucial to reducing the survival of infective larvae.

    Zoonotic Concerns

    • Strongyloides westeri is not zoonotic, posing no infection risk to humans.

    Parascaris equorum Classification

    • Parascaris equorum is classified as a large roundworm under the order Ascaridida, also called the equine ascarid or large roundworm.

    Parascaris equorum Life Cycle

    • The life cycle is direct; infective eggs containing L2 larvae are shed in feces and can persist in the environment.
    • Upon ingestion, eggs hatch in the small intestine, and larvae migrate through the intestinal wall to the liver and then to the lungs.
    • Larvae are coughed up, swallowed, and mature into adults in the small intestine, with a prepatent period of about 10-12 weeks.

    Clinical Presentation in Foals

    • Primarily affects nursing and weaned foals under one year, with signs including coughing, nasal discharge, weight loss, and reduced growth.
    • Heavy infections may cause intestinal impaction and rupture, leading to potential fatality.
    • Liver lesions resembling "milk spots" can result from larval migration.

    Pathology Based on Worm Burden

    • Mild to moderate infections result in mild respiratory signs and growth reduction.
    • Heavy infections increase the risk of serious complications, including intestinal blockage, rupture, and respiratory symptoms due to larval migration through the lungs.

    Diagnosis of Parascaris equorum

    • Diagnosis usually involves identifying characteristic thick-shelled ascarid eggs in feces using flotation methods.
    • In severe cases, adult worms may be observed in feces or during necropsy.

    Treatment and Control Measures

    • Treatment typically includes broad-spectrum anthelmintics such as ivermectin or fenbendazole, with gradual deworming recommended for heavily infected foals to avoid blockage.
    • Effective control requires regular manure removal and pasture management since eggs can remain viable in the environment for years.
    • Foals are dewormed more frequently than adult horses to prevent heavy infections.

    Zoonotic Concerns

    • No significant zoonotic risks are associated with Parascaris equorum, as it is specific to horses and does not infect humans.

    Classification of Strongylus spp.

    • Classified as nematodes under the order Strongylida.
    • Commonly known as large strongyles or bloodworms.
    • Notable species include Strongylus vulgaris, Strongylus edentatus, and Strongylus equinus.

    General Life Cycle of Strongylus spp.

    • Life cycle is direct; horses ingest infective L3 larvae while grazing.
    • Larvae penetrate gastrointestinal (GI) mucosa, migrating through tissues based on species.
    • Larvae return to cecum and colon to mature into adults, ingest blood, and produce eggs shed in feces.
    • Prepatent period varies: 6 months for S. vulgaris, 11 months for S. edentatus, 9 months for S. equinus.

    Migration of Strongylus vulgaris Larvae

    • After ingestion, larvae penetrate the intestinal wall, migrating to the cranial mesenteric artery.
    • This migration causes damage to arterial endothelium, leading to arteritis, thrombosis, and possible embolism.
    • Larvae then mature and return to the large intestine, completing their life cycle.

    Migration of Strongylus edentatus Larvae

    • Larvae migrate via portal veins to the liver, residing there for about 2 months.
    • They then move through the peritoneal cavity back to the large intestine to mature.
    • This migration is relatively harmless compared to S. vulgaris.

    Migration of Strongylus equinus Larvae

    • Larvae migrate through the peritoneal cavity to the liver and pancreas, staying for several months.
    • Eventually, they return to the large intestine to mature.
    • This species is less pathogenic compared to S. vulgaris.

    Clinical Presentation of Strongylus spp. Infection in Horses

    • Common clinical signs include weight loss, lethargy, diarrhea, anemia, and hypoproteinemia.
    • Dependent edema may occur due to protein loss.
    • S. vulgaris is the most pathogenic, with potential for colic due to mesenteric artery thrombosis, ischemia, and bowel infarction.

    Diagnosis of Strongylus spp.

    • Diagnosis relies on clinical signs, fecal egg counts, and identification of strongyle-type eggs in feces.
    • Eggs cannot be distinguished between large and small strongyles.
    • Necropsy may reveal migration damage from S. vulgaris in the cranial mesenteric artery.

    Treatment and Control of Strongylus spp.

    • Treatment involves broad-spectrum anthelmintics such as ivermectin, moxidectin, or fenbendazole.
    • Strategic deworming is necessary due to long prepatent periods targeting larval stages.
    • Regular fecal egg counts and pasture management (e.g., manure removal) are crucial for controlling parasite load.

    Zoonotic Concerns

    • No zoonotic concerns with Strongylus spp.; they are specific to equines and do not pose risks to humans.

    Classification

    • Oxyuris equi is a nematode classified under the order Oxyurida.
    • Commonly known as the equine pinworm.

    Life Cycle

    • Life cycle is direct, with no intermediate hosts.
    • Horses ingest eggs containing infective L3 larvae.
    • Larvae emerge in the small intestine and migrate to the cecum and colon to mature into adults.
    • Adult females migrate to the perianal region to deposit eggs on the skin around the anus.
    • Eggs become infective in 3-5 days.
    • Prepatent period lasts about 5 months.

    Clinical Presentation

    • Primary symptom is intense itching around the tail and perianal region due to egg deposition.
    • Excessive tail rubbing leads to hair loss, broken tails, and potential secondary bacterial infections.
    • Itching may cause horses to rub against objects, damaging skin and coat.
    • Possible intestinal ulcers from larval feeding on the intestinal mucosa.

    Diagnosis

    • Diagnosed using the "scotch tape test," which collects eggs for microscopic examination.
    • Eggs are elongated, oval with a flattened side, and possess a distinct operculum (cap).
    • Adult worms can be seen around the anus or in feces.

    Treatment and Control

    • Treated with anthelmintics such as ivermectin, pyrantel pamoate, or fenbendazole.
    • Hygiene measures are vital due to the stickiness of eggs; cleaning the perianal area is crucial.
    • Disinfection of the environment, including bedding and grooming equipment, helps reduce contamination.

    Zoonotic Concerns

    • No zoonotic risks associated with Oxyuris equi.
    • Pinworm infections are specific to horses and do not affect humans.

    Classification of Small Strongyles

    • Small strongyles, or cyathostomins, belong to the superfamily Strongyloidea and order Strongylida.
    • Over 40 species of small strongyles infect horses.

    Life Cycle and Migration Differences

    • Cyathostomins do not migrate outside the gastrointestinal tract, contrasting with large strongyles.
    • After ingestion, L3 larvae enter the cecum and colon mucosa, where they encyst.
    • Encysted larvae may undergo hypobiosis before maturing and feeding on the mucosal surface.

    Life Cycle of Small Strongyles

    • Direct life cycle where horses ingest infective L3 larvae from contaminated pastures.
    • Larvae encyst in the cecum and colon mucosa and may remain dormant until conditions are favorable.
    • After weeks to months, larvae emerge, mature into adults, and begin feeding.
    • Adult worms mate and shed eggs in feces, which hatch into L1 larvae and develop to L3 larvae in the environment.
    • Prepatent period is 6-12 weeks based on environmental factors.

    Clinical Presentation of Infection

    • Light infections may show no clinical signs.
    • Heavy infections can cause unthriftiness, lethargy, diarrhea, anemia, and hypoproteinemia.
    • Sudden mass emergence of larvae may lead to colitis and severe diarrhea, termed larval cyathostominosis, prevalent in late winter or early spring.

    Pathology Associated with Small Strongyles

    • Massive emergence of encysted larvae damages the mucosal lining, causing inflammation, edema, and fibrosis.
    • This disrupts nutrient absorption, leading to weight loss and colitis.
    • Adult worms contribute less to pathology than encysted larvae.

    Impact of Hypobiosis

    • Hypobiosis allows larvae to survive adverse conditions and synchronize their emergence.
    • This can overwhelm the host's immune response, causing clinical disease.
    • Horses may show no symptoms during hypobiosis; signs appear when larvae emerge.

    Susceptible Horses

    • All age groups can be infected, but younger horses and those in poorly managed pastures are at higher risk.
    • Heavily stocked pastures increase exposure to high egg shedding.

    Diagnosis of Small Strongyle Infections

    • Diagnosis primarily involves fecal egg counts (FEC) to detect strongyle-type eggs.
    • Eggs cannot differentiate between small and large strongyles.
    • Low or negative FEC may occur in larval cyathostominosis due to the presence of immature larvae.
    • Necropsy can reveal encysted larvae in the intestinal mucosa.

    Treatment Options

    • Treatment includes anthelmintics like ivermectin, moxidectin, or fenbendazole, with moxidectin effective against encysted larvae.
    • Resistance, particularly to fenbendazole and pyrantel, has been reported, highlighting the need for resistance management.
    • Targeted deworming based on FEC is recommended to minimize resistance.

    Prevention and Control

    • Good pasture management includes rotating pastures, avoiding overstocking, and manure removal.
    • Regular FEC monitoring helps identify high egg shedders and guides deworming strategies.
    • AAEP recommends deworming based on FEC results and routine treatments for encysted larvae (powerpac with double dose of fenbendazole for 5 days).

    Zoonotic Concerns

    • There are no zoonotic risks associated with cyathostomins; they are equine-specific and do not affect humans.

    Classification

    • Anoplocephala perfoliata is a cestode (tapeworm) under the order Cyclophyllidea and family Anoplocephalidae.
    • It is the most common tapeworm species found in horses.

    Life Cycle

    • The life cycle is indirect, involving an intermediate host, the oribatid mite.
    • Mites ingest tapeworm eggs shed in horse feces, leading to the development of infective cysticercoid larvae.
    • Horses become infected by ingesting mites while grazing, releasing larvae in their intestines.
    • The larvae attach to the intestinal mucosa, usually at the ileocecal junction, and mature into adults.
    • The prepatent period for infection is approximately 6-10 weeks.

    Typical Location in Horses

    • Tapeworms typically attach at the ileocecal junction, ileum, and cecum.
    • In heavy infections, tapeworms can cluster in these areas, leading to serious clinical issues.

    Clinical Presentation

    • Many horses remain asymptomatic despite infection.
    • Heavy infections can lead to colic, weight loss, diarrhea, and poor body condition.
    • Associated complications include ileocecal impaction, spasmodic colic, intussusception, and cecal rupture, all of which can be life-threatening.
    • Inflammation from the tapeworm attachment contributes to these symptoms.

    Pathology

    • Anoplocephala perfoliata causes localized inflammation and damage to the intestinal mucosa at the ileocecal junction.
    • This inflammation can impair intestinal motility and increase the risk of ileal impaction and cecal intussusception.
    • Severe cases may lead to rupture of the cecum or other intestinal sections.
    • The inflammation and physical blockage from large worm populations are primary pathology contributors.

    Risk Factors for Clinical Disease

    • Horses of all ages can be infected; however, younger horses and those with poor pasture management are more vulnerable.
    • Pastures with high populations of oribatid mites, particularly in dense vegetation and humid conditions, increase the risk of infection.

    Diagnosis

    • Diagnosing tapeworm infections is challenging due to inconsistency in egg shedding.
    • Fecal flotation can detect eggs, but sensitivity is low.
    • Modified flotation techniques or ELISA-based tests for antibodies or antigens increase diagnostic accuracy.
    • Post-mortem diagnosis can occur by finding adult tapeworms attached to the ileocecal junction.

    Treatment and Control

    • Treatment involves anthelmintics like praziquantel or a double dose of pyrantel pamoate.
    • Horses should be dewormed at least once a year, typically in fall or winter when mite activity lessens.
    • Preventive measures include managing pasture conditions and reducing overgrazing to limit exposure to oribatid mites.

    Public Health or Zoonotic Concerns

    • Anoplocephala perfoliata poses no zoonotic concerns, as it is specific to equines and does not affect humans.

    Classification

    • Dictyocaulus arnfieldi is a nematode in the order Strongylida.
    • It is the primary lungworm affecting equines.

    Hosts Affected

    • Natural hosts are donkeys, which often remain asymptomatic.
    • Horses can become infected when sharing pastures with donkeys and exhibit clinical symptoms.

    Life Cycle

    • The life cycle is direct and begins in the bronchi and bronchioles of the host.
    • Adult worms lay embryonated eggs that are coughed up, swallowed, and excreted in feces as eggs or L1 larvae.
    • L1 larvae develop into infective L3 larvae in the environment.
    • Infection occurs when horses or donkeys ingest L3 larvae while grazing.
    • L3 larvae penetrate the gastrointestinal mucosa and migrate to the lungs through lymphatics and blood vessels.
    • In the lungs, larvae mature into adults, causing respiratory disease, with a prepatent period of approximately 4 weeks.

    Clinical Presentation

    • Horses exhibit coughing, nasal discharge, dyspnea, and exercise intolerance due to lungworm infection.
    • Wheezing or abnormal lung sounds may be present; severity depends on the number of adult worms.
    • Donkeys typically do not show clinical signs despite being carriers.

    Pathology

    • Adult lungworms in the bronchi and bronchioles cause irritation and inflammation.
    • This leads to bronchitis, excess mucus production, airway obstruction, and reduced lung function.
    • Secondary bacterial infections may complicate respiratory symptoms in severe cases.

    Reservoir Status of Donkeys

    • Donkeys are asymptomatic carriers, shedding infective larvae without showing disease signs.
    • Co-grazing with donkeys increases the risk of lungworm infection in horses.
    • The asymptomatic nature of the infection in donkeys complicates detection and management.

    Infection Variability

    • Donkeys, as the natural hosts, often show no clinical signs even with heavy infections.
    • Horses are more likely to develop significant respiratory symptoms when infected.

    Diagnosis

    • Diagnosis in horses is achieved by identifying L1 larvae in fresh feces using the Baermann technique.
    • Adult worms or larvae may be found in bronchoalveolar lavage (BAL) or tracheal wash fluid.
    • Diagnosis may also rely on clinical signs, history of co-grazing, and auscultation findings.

    Treatment and Control

    • Treat infections with anthelmintics like ivermectin or moxidectin, effective against adults and migrating larvae.
    • Control strategies include separating grazing areas for horses and donkeys or regularly deworming donkeys.
    • Monitoring donkey fecal output can help assess infection risks in shared pastures.

    Zoonotic Concerns

    • Dictyocaulus arnfieldi poses no zoonotic risk; it specifically affects equines and is not a threat to humans.

    Classification and Host

    • Onchocerca spp. are nematodes classified under the order Spirurida.
    • These are filarial worms that primarily impact the skin and connective tissues of horses.

    Affected Species and Vectors

    • Horses are the primary species affected by Onchocerca spp.
    • Transmission vectors include biting flies, especially:
      • Culicoides species (biting midges)
      • Simulium species (black flies)

    Relevant Onchocerca Species in Equines

    • Key Onchocerca species affecting horses include:
      • Onchocerca cervicalis
      • Onchocerca reticulata
      • Onchocerca railliti, primarily affecting donkeys in Africa

    Life Cycle

    • The life cycle is indirect, involving several stages:
      • Adult worms inhabit connective tissues, notably the nuchal ligament.
      • Microfilariae produced by adults migrate to the skin and are ingested by biting flies.
      • Within the fly, microfilariae develop into infective L3 larvae.
      • The larvae are transmitted to a new host upon the fly's next bite.
      • Larvae mature into adult worms within the host's subcutaneous tissues.
      • The prepatent period lasts approximately 4-6 months.

    Clinical Signs

    • Most Onchocerca spp. infections are asymptomatic, particularly in adult worms.
    • Microfilariae presence can cause:
      • Dermatitis
      • Fistulous withers
      • Poll evil
      • Uveitis
    • Common symptoms include itching (pruritus), hair loss, crusting, and depigmentation.
    • O. cervicalis can cause localized swelling or nodules in the nuchal ligament.
    • O. reticulata may lead to increased reactions in distal limb connective tissue.
    • Eye inflammation can result in conjunctivitis or uveitis.

    Pathology

    • Pathology is primarily caused by microfilariae in the skin, leading to:
      • Localized inflammation and dermatitis
      • Possible ocular lesions
      • Chronic infections can form nodules or fibrous masses in affected tissues
      • Chronic eye involvement may result in recurrent uveitis or other ocular issues

    Diagnosis

    • Diagnosis relies on clinical signs, such as itching and nodules, with a history of fly exposure.
    • Skin biopsies can identify microfilariae, while serological tests or PCR detect Onchocerca DNA.

    Treatment and Control

    • Treatment options include:
      • Ivermectin or moxidectin effective against microfilariae but limited on adult worms.
      • Surgical removal may be necessary for adult worm-induced nodules.
    • Control measures aim at reducing fly exposure through:
      • Insect repellents and fly masks
      • Environmental management, like reducing standing water, to limit fly breeding.

    Zoonotic Concerns

    • No zoonotic risks are associated with Onchocerca spp.; these parasites are specific to horses and do not affect humans.

    Classification of Habronema spp.

    • Habronema spp. are nematodes in the order Spirurida.
    • Primarily inhabit the stomach of horses.
    • Larvae can lead to cutaneous lesions, known as summer sores.
    • Life cycle of Habronema spp. is indirect.
    • Adult worms release eggs or larvae in the horse's stomach, passed through feces.
    • Flies (houseflies and stable flies) ingest larvae while feeding on feces.
    • Larvae develop into infective L3 larvae inside the flies.
    • Flies deposit L3 larvae on moist areas of the horse’s skin, particularly wounds and around the eyes.
    • Larvae invade skin instead of maturing in the stomach, causing summer sores through granulomatous reaction.

    Clinical Signs of Cutaneous Habronemiasis (Summer Sores)

    • Characterized by granulomatous, ulcerative skin lesions that do not heal.
    • Commonly located on the face, eyes, legs, and near wounds.
    • Lesions are reddish-brown, greasy, and may contain calcified debris resembling rice grains.
    • Affected horses may experience itching and irritation, leading to scratching or rubbing.

    Pathology Associated with Cutaneous Habronemiasis

    • Inflammatory reaction from larvae presence in the skin triggers immune response.
    • Granuloma formation can become chronic if untreated.
    • Secondary bacterial infections may arise, complicating the condition and hindering healing.

    Diagnosis of Cutaneous Habronemiasis

    • Diagnosis based on non-healing, granulomatous skin lesions, particularly in fly-bite areas.
    • Identification of larvae may occur in skin scrapings or biopsies from lesions.
    • History of fly exposure during warmer months supports diagnosis.

    Treatment and Control of Cutaneous Habronemiasis

    • Systemic anthelmintics like ivermectin or moxidectin are used to eliminate larvae.
    • Topical treatments such as corticosteroids and antibiotic ointments help reduce inflammation and secondary infections.
    • Severe cases may necessitate surgical removal of affected tissue.
    • Effective fly control strategies include repellents, fly masks, and environmental management to lower fly populations.

    Zoonotic Concerns with Habronema spp.

    • No zoonotic risks; Habronema spp. parasites are specific to equines and do not infect humans.
    • Fly control is crucial to minimize the spread of these parasites and other equine diseases.

    Classification

    • Thelazia lacrymalis is a nematode classified under the order Spirurida.
    • Commonly referred to as the equine eyeworm.

    Natural Habitat

    • Resides in the conjunctival sac and tear ducts of horses.
    • Feeds on the tear film, leading to irritation of the eye.

    Life Cycle

    • The life cycle is indirect, involving adult worms in the conjunctival sac.
    • Adult worms mate and produce eggs, which are consumed by flies, particularly Musca species (e.g., face flies).
    • Inside the fly, larvae develop into infective L3 larvae.
    • L3 larvae are deposited back onto the horse's eyes, maturing into adult worms.
    • Prepatent period lasts about 3-6 weeks:
      • 2-4 weeks for egg to L3 in the fly,
      • 10-11 weeks for L3 to become adults in the horse.

    Clinical Signs

    • Symptoms can range from mild to severe ocular irritation.
    • Common signs include excessive tearing (epiphora), conjunctivitis, eyelid swelling, squinting (blepharospasm), photophobia, and eye rubbing.
    • Severe cases may lead to corneal ulcers and secondary bacterial infections.
    • Adult worms may be visible in the eye or conjunctival sac.

    Pathology

    • Primarily causes irritation and inflammation of the conjunctiva and tear ducts.
    • Inflammation results in excess tear production, redness, and swelling.
    • Prolonged infections can cause corneal damage, vision impairment, and increase the risk of secondary infections.
    • The movement of worms results in physical irritation and discomfort.

    Risk Factors

    • Horses in areas with high fly populations, especially where Musca species thrive, are at greater risk.
    • Wet, warm environments contribute to large fly populations.
    • Poor fly control around stables or grazing areas elevates infection risk.

    Diagnosis

    • Diagnosis often involves direct observation of adult worms in the conjunctival sac or tear ducts.
    • Worms are thin, white, and visible to the naked eye or under magnification.
    • Excessive tearing and conjunctivitis may prompt further examination.
    • Microscopic examination can reveal larvae or adult worms in eye secretions.

    Treatment and Control

    • Treatment usually involves manual removal of worms using fine forceps, often under sedation or local anesthesia.
    • Topical and systemic anthelmintics, such as ivermectin, are effective in eliminating remaining worms or larvae.
    • Preventive measures include fly control strategies like fly masks, repellents, and managing fly populations.
    • Reducing horse exposure to flies during peak seasons minimizes infection risk.

    Zoonotic Concerns

    • Thelazia lacrymalis is not known to be zoonotic, though some Thelazia species can infect humans.
    • Zoonotic infections in humans are more closely associated with Thelazia callipaeda.
    • Good hygiene and effective fly control are essential to reduce the risk of zoonotic infections from other species.

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