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?

Fatal neurologic disease Signup and view all the answers

Which of the following best describes Halicephalobus gingivalis?

A parthenogenic nematode with hematogenous spread Signup and view all the answers

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

Ceratopogonidae Signup and view all the answers

Which treatment is effective against habronemiasis caused by Habronema larvae?

Ivermectin Signup and view all the answers

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

Scotch tape test Signup and view all the answers

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

Pruritus ani Signup and view all the answers

How do larvae of Habronema reach their definitive host?

Via midge bites Signup and view all the answers

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

Regular deworming Signup and view all the answers

What type of parasite causes summer sores in horses?

Ceratopogonidae Signup and view all the answers

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

Laminitis Signup and view all the answers

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

Eggs in the environment Signup and view all the answers

What is the primary diagnostic challenge associated with Anoplocephala infections?

Eggs are difficult to detect in feces. Signup and view all the answers

Which of the following treatments is effective against Strongylus vulgaris?

Benzimidazoles Signup and view all the answers

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

Diarrhea with hypoalbuminemia Signup and view all the answers

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

Transmammary Signup and view all the answers

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

It assesses the efficacy of dewormers. Signup and view all the answers

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

It migrates through the liver and lungs causing injury. Signup and view all the answers

What treatment is typically ineffective against adult cyathostomes?

Benzimidazoles Signup and view all the answers

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

They can be mistaken for eggs from small strongyles. Signup and view all the answers

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

Arteritis and thrombosis in cranial mesenteric arteries Signup and view all the answers

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

To determine the presence of large strongyles Signup and view all the answers

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

A decrease in the parasite load in the treated animal Signup and view all the answers

What is a common characteristic of Dictyocaulus arnfieldi in equids?

It causes chronic bronchitis in horses Signup and view all the answers

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

All parasites were eliminated from the system Signup and view all the answers

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

Baermann method to detect L1 in feces Signup and view all the answers

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

Insufficient dosage or treatment protocol failure Signup and view all the answers

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

Performing blood work and imaging as next steps Signup and view all the answers

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

Macrocyclic lactones Signup and view all the answers

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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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.