Parasites Affecting Horses
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Questions and Answers

What is the most characteristic clinical sign of Equine Protozoal Myeloencephalitis (EPM) caused by Sarcocystis neurona?

  • Respiratory distress
  • Symmetric muscle atrophy
  • Severe dehydration
  • Asymmetric ataxia (correct)
  • Which diagnostic method is NOT typically used for confirming the diagnosis of EPM?

  • PCR test of cerebrospinal fluid
  • Postmortem examination
  • Fecal egg count (correct)
  • ELISA
  • In which host does Parelaphostrongylus tenuis primarily live as an adult?

  • White-tailed deer (correct)
  • Cattle
  • Sheep
  • Horses
  • What is the likely outcome for abnormal hosts infected by Parelaphostrongylus tenuis?

    <p>Fatal neurologic disease (D)</p> Signup and view all the answers

    Which of the following best describes Halicephalobus gingivalis?

    <p>A parthenogenic nematode with hematogenous spread (B)</p> Signup and view all the answers

    What is the primary cause of granulomas in horses due to larvae deposition?

    <p>Ceratopogonidae (D)</p> Signup and view all the answers

    Which treatment is effective against habronemiasis caused by Habronema larvae?

    <p>Ivermectin (D)</p> Signup and view all the answers

    What diagnostic test is best used to confirm the presence of pinworm eggs in horses?

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

    Which of the following is a clinical sign specifically associated with pinworm infestation in horses?

    <p>Pruritus ani (C)</p> Signup and view all the answers

    How do larvae of Habronema reach their definitive host?

    <p>Via midge bites (B)</p> Signup and view all the answers

    What is one of the main methods to prevent future infections by parasitic larvae in horses?

    <p>Regular deworming (D)</p> Signup and view all the answers

    What type of parasite causes summer sores in horses?

    <p>Ceratopogonidae (A)</p> Signup and view all the answers

    What serious condition can result from Potomac horse fever if not treated?

    <p>Laminitis (C)</p> Signup and view all the answers

    What is the life cycle initial stage for pinworms in horses?

    <p>Eggs in the environment (D)</p> Signup and view all the answers

    What is the primary diagnostic challenge associated with Anoplocephala infections?

    <p>Eggs are difficult to detect in feces. (C)</p> Signup and view all the answers

    Which of the following treatments is effective against Strongylus vulgaris?

    <p>Benzimidazoles (A), Pyrantel pamoate (D)</p> Signup and view all the answers

    What is the most likely clinical sign of larval cyathostominosis in horses?

    <p>Diarrhea with hypoalbuminemia (A)</p> Signup and view all the answers

    What is the mechanism of transmission for Strongyloides westeri in horses?

    <p>Transmammary (C)</p> Signup and view all the answers

    What is the significance of a fecal egg count reduction test (FECRT) in veterinary practice?

    <p>It assesses the efficacy of dewormers. (D)</p> Signup and view all the answers

    How does the larval stage of Parascaris contribute to its pathology in horses?

    <p>It migrates through the liver and lungs causing injury. (A)</p> Signup and view all the answers

    What treatment is typically ineffective against adult cyathostomes?

    <p>Benzimidazoles (A), Macrocyclic lactones (D)</p> Signup and view all the answers

    What is a common characteristic of strongyle-type eggs in fecal samples?

    <p>They can be mistaken for eggs from small strongyles. (D)</p> Signup and view all the answers

    What factor can lead to the development of bowel wall infarction in horses infected with Strongylus vulgaris?

    <p>Arteritis and thrombosis in cranial mesenteric arteries (B)</p> Signup and view all the answers

    What is the primary purpose of performing a larval culture for the parasites in Moonbeam?

    <p>To determine the presence of large strongyles (A)</p> Signup and view all the answers

    What does a fecal egg count reduction indicate after treatment with fenbendazole?

    <p>A decrease in the parasite load in the treated animal (D)</p> Signup and view all the answers

    What is a common characteristic of Dictyocaulus arnfieldi in equids?

    <p>It causes chronic bronchitis in horses (D)</p> Signup and view all the answers

    Why might the fecal flotation test reveal 'None detected' for Moonbeam after treatment with moxidectin?

    <p>All parasites were eliminated from the system (A)</p> Signup and view all the answers

    Which method is used to diagnose the presence of Dictyocaulus in equids?

    <p>Baermann method to detect L1 in feces (A)</p> Signup and view all the answers

    What is the potential implication of a rising strongyle egg count in Moonbeam after treatment with fenbendazole?

    <p>Insufficient dosage or treatment protocol failure (D)</p> Signup and view all the answers

    What should be considered if neurological signs are observed in a horse?

    <p>Performing blood work and imaging as next steps (A)</p> Signup and view all the answers

    Which of the following treatments would likely be effective against Dictyocaulus in equids?

    <p>Macrocyclic lactones (C)</p> Signup and view all the answers

    Flashcards

    Habronema midges

    Flies that deposit larvae on wounds or mucous membranes, causing granulomas (summer sores).

    Habronema life cycle

    Adult Habronema live in the horse's stomach. Larvae are passed in feces, ingested by muscid maggots, then deposited by flies on the horse's skin where they burrow in creating wounds/granulomas.

    Summer sores

    A skin disease caused by Habronema larvae.

    Pinworms

    Nematodes that cause pruritus ani (intense itching around the anus).

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    Pinworm eggs

    Have a polar plug and are asymmetrically flattened. Can be detected by a Scotch tape test or fecal flotation.

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    Treatment for Habronema

    Ivermectin, moxidectin, or surgical excision.

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    Treatment for Pinworms

    Pyrantel pamoate, ivermectin, or fenbendazole.

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    Colic diagnostic testing

    Testing to identify causes of colic/diarrhea in a horse; tests depend on the suspected differential.

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    Potomac Horse Fever

    An acute, potentially fatal disease in horses caused by the bacterium Neorickettsia risticii, typically acquired through ingestion of infected caddisflies.

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    What is a larval culture test?

    A lab technique used to identify specific types of parasitic worms in a horse by incubating fecal samples and examining the developing larvae under a microscope.

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    Anoplocephala perfoliata

    A type of tapeworm that infects horses, residing in the cecum and ileum. It's transmitted through the ingestion of cysticercoids in oribatid mites.

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    What are Cyathostomins?

    A group of small strongyle parasites that infect horses, often found in the large intestine.

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    Strongylus vulgaris

    A type of strongyle that lives as an adult in the large intestine of horses. Its larvae migrate through blood vessels to the cranial mesenteric arteries, potentially causing severe damage and even death.

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    What does a FECR test show?

    A fecal egg count reduction test measures the effectiveness of deworming medication by comparing the number of parasite eggs in feces before and after treatment.

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    Why might an FECR show no change?

    A lack of change in the FECR may indicate resistance to the deworming medication, or the presence of a different parasite species that is not affected by the drug.

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    Larval Cyathostominosis

    A disease caused by a large number of encysted larvae of cyathostome (small strongyle) worms emerging from the horse's intestinal mucosa, leading to watery diarrhea and hypoalbuminemia.

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    What is Dictyocaulus?

    A type of lungworm that infects horses, causing respiratory problems.

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    Strongyloides westeri

    A type of roundworm that lives in the small intestine of horses, often transmitted from mother to foal through milk.

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    Parascaris equorum

    A large roundworm that infects horses, migrating through the liver and lungs before reaching the intestines. Primarily affects young horses.

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    How is Dictyocaulus diagnosed?

    The presence of Dictyocaulus larvae (L1) in horse feces can be detected by the Baermann method.

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    FECRT (Fecal Egg Count Reduction Test)

    A test recommended annually to assess the effectiveness of deworming medications in horses. It involves comparing the number of eggs in fecal samples before and after treatment.

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    What causes neurologic signs in horses?

    Several factors can cause neurological issues in horses, including infections, toxins, trauma, and even tumors.

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    What tests might be helpful for neurologic signs?

    Common tests for neurological problems in horses may include blood tests, spinal fluid analysis, imaging studies (like x-rays, MRI, CT), and even biopsies.

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    Strongyle Eggs

    Eggs of strongyle worms, which can be detected in feces and are indistinguishable from cyathostome eggs.

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    Cyathostome Larvae

    Larvae of cyathostome worms, which can be identified by larval culture, allowing for differentiation from other strongyle species.

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    Treatment for Strongyle Infections

    Treatment for strongyle infections in horses typically involves deworming medications such as benzimidazoles, macrocyclic lactones, and pyrantel pamoate, but resistance can be a major challenge.

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    Sarcocystis neurona

    A protozoan parasite that causes Equine Protozoal Myeloencephalitis (EPM) in horses.

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    EPM (Equine Protozoal Myeloencephalitis)

    A neurological disease in horses caused by the protozoan parasite Sarcocystis neurona.

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    Parelaphostrongylus tenuis

    A nematode parasite commonly known as the meningeal worm, that infects white-tailed deer.

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    Halicephalobus gingivalis

    A tiny nematode that can cause fatal meningoencephalomyelitis in horses and humans.

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    Halicephalobus gingivalis Diagnosis

    Diagnosis of Halicephalobus gingivalis infection is typically made on necropsy because the parasite doesn't produce eggs in feces.

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    Study Notes

    Parasites by Host: Horse

    • This presentation covers parasites that affect horses, focusing on diagnosis, treatment, and prevention.
    • Students should be able to provide a differential list of parasites causing clinical signs in a horse.
    • Generate a diagnostic plan to rule in or out specific parasites, including expected findings for each test.
    • Design a treatment plan tailored to the parasite causing the problem.
    • Inform horse owners about parasite prevention strategies.

    Ceratopogonidae (Midges)

    • Tiny flies typically less than 2mm in size.
    • Characterized by long, slender antennae and short mouthparts.
    • Mottled wings.
    • Adults are nocturnal.
    • Females are blood-feeding.
    • Culicoides spp. bites are painful and similar to cigarette burns.
    • Can trigger allergic dermatitis in horses.

    Habronematoidea

    • Live as adults primarily in the horse's stomach.
    • Larvae or eggs passed in feces, are ingested and developed by muscid flies.
    • L3 stage deposited on wounds or mucous membranes in the horse.
    • Larvae cause granulomas (cutaneous habronemiasis).
    • Treatment options include Ivermectin, moxidectin, and surgical excision.

    Oxyurida (Pinworms)

    • Nematodes with long, tapering tails.
    • Esophagus has a bulbous shape.
    • Highly host-specific.
    • Gravid females deposit eggs around the perianal area.
    • Eggs develop to infective stage in 4-5 days and contaminate the environment.
    • Common signs include pruritus ani and tail rubbing.
    • Diagnosis: Scotch tape test or fecal flotation
    • Eggs have a polar plug, and are asymmetrically flattened
    • Treatment options include Pyrantel pamoate, ivermectin, and fenbendazole.

    Trichoptera (Caddisflies)

    • Causes Potomac Horse Fever.
    • Infection occurs via drinking water containing caddisflies.
    • Caused by Neorickettsia risticii.
    • Symptoms include acute enterocolitis, mild colic, fever and diarrhea.
    • Abortion in pregnant mares.
    • May lead to laminitis.
    • Treatment: Oxytetracycline

    Anoplocephala

    • Adults live in the cecum and ileum of the horse.
    • Definitive host infected when ingesting cysticercoid from mites.
    • Associated with ulceration and ileal inflammation.
    • Can cause intussusception near ileocecal valve.
    • Diagnosis: Eggs are difficult to detect in feces; ELISA for IgG may be considered
    • Treatment: Pyrantel pamoate, praziquantel

    Strongylus

    • Live as adults in the large intestine of horses.
    • Strongylus vulgaris: fourth-stage larvae enter blood vessels, migrate to cranial mesenteric arteries.
    • Migratory larvae cause arteritis, thrombosis, and embolism
    • Bowel wall infarction is frequent and fatal.
    • Diagnosis involves examining fecal flotation specimens for strongyle-type eggs.
    • May be indistinguishable from small strongyle eggs;
    • Eggs may not be passed when signs develop.
    • Treatment options include benzimidazoles, macrocyclic lactones, and pyrantel pamoate.

    Cyathostomins

    • Aka Small Strongyles
    • Live as adults in the large intestines of horses, pigs, and wildlife.
    • Larval symptoms include watery diarrhea with hypoalbuminemia, (mostly fall and spring).
    • Larvae encyst in the mucosa.
    • Diagnosis: Strongyle-type eggs on fecal flotation.
    • Larval culture for L3 identification.
    • Treatment: Adults resistant to benzimidazoles and pyrantel (may be susceptible to ivermectin but resistance developing).

    Strongyloides

    • Tiny parthenogenic female nematodes.
    • Live in mucosal crypts of the small intestine.
    • Strongyloides westeri in horses.
    • Transmammary transmission occurs.
    • Diagnosed via fecal examination (eggs contain rhabditiform larvae)
    • Treatment: Macrocyclic lactones, benzimidazoles.

    Parascaris

    • Very large nematode.
    • Acquired through ingestion of infective eggs (containing L3).
    • Larvae migrate through liver and lungs.
    • Worm burden peaks at 5 months of age then decreases.
    • Can cause bowel perforation and peritonitis.
    • Diagnosis: Eggs in fecal flotation, ultrasonography
    • Treatment: Pyrantel pamoate, piperazine, benzimidazoles, macrocyclic lactones.

    Fecal Egg Count Reduction Test (FECRT)

    • Recommended annually by the American Association of Equine Practitioners (AAEP).
    • Helpful for monitoring deworming effectiveness.
    • deworm and repeat fecal test 10-14 days after initial treatment.

    Clinical Signs & Parasites

    • Skin lesions: Ceratopogonidae (midges)
    • Colic/diarrhea: Various parasites

    Active Learning Activities

    • Various scenarios about treating several horses, with specific questions about different diagnostic and treatment considerations.

    Dictyocaulus

    • Adult worms in the horse's respiratory tract.
    • First-stage larvae hatch from eggs before passing into feces
    • Disease: Chronic bronchitis
    • Diagnosis: L1 in feces, Baermann method
    • Treatment: Macrocyclic lactones, benzimidazoles

    Sarcocystis neurona

    • Causes equine protozoal myeloencephalitis (EPM).
    • Infection via ingestion of sporocysts from opossum feces.
    • Symptoms include ataxia, weakness of limbs, muscle atrophy.
    • Diagnosis: PCR of cerebrospinal fluid, ELISA, antibody titers, postmortem exam.
    • Treatment: Ponazuril, diclazuril, sulfonamides, pyrimethamine.

    Parelaphostrongylus tenuis

    • AKA Meningeal worm.
    • Adults live in the meninges of whitetailed deer (definitive host).
    • Development of larvae in abnormal hosts (sheep, goats, camelids, cattle, horses).
    • Leads to fatal neurologic disease.
    • Diagnosis is presumptive, no larvae in abnormal host feces
    • Treatment unrewarding in aberrant hosts.

    Halicephalobus gingivalis

    • Tiny nematode with rhabditiform esophagus.
    • No males.
    • Parthenogenic species.
    • Infection via contamination of wounds, then hematogenous spread.
    • Symptoms include present in nasal and maxillary sinuses, gingiva, kidneys, heart, brain, spinal cord.
    • Potentially fatal meningoencephalomyelitis infections in horses and humans.
    • No eggs passed, typically diagnosed on necropsy
    • Treatment: No approved treatment, prognosis poor with CNS involvement.

    Practice Questions

    • Multiple-choice questions on various parasite identification, clinical signs related to parasites
    • What clinical sign is associated with a specific parasite detected in a fecal flotation?
    • Diagnostic tests for various types of parasite infections
    • Effects of various drugs against specific parasites
    • Potential parasite exposure to opossum feces.

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    Parasites by Host - Horse PDF

    Description

    This quiz explores various parasites that impact horses, including their diagnosis, treatment, and prevention strategies. It emphasizes the importance of understanding the life cycles of these parasites to provide effective care. Students will learn to create diagnostic and treatment plans tailored to the specific parasites affecting horses.

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