Exam 2 - Lecture 9 Flashcards
Lecture 9
Parascaris equorum
Morphology
-Large Stout Worms; Males (15 to 28cm) and Females (up to 50cm long, & 8mm in diameter)
-Sexually dimorphic
-Anterior opening w/ 3 lips
-Adults parasitic in the small intestine of equines
Parascaris equorum
-Direct lifecycle
-Infection by ingestion of larvated eggs on
contaminated pasture
-Tracheal/somatic migration
-Primarily parasite of foals
-Pre‐patent period ~12 weeks; round eggs ~ 90μm on fecal float
Parascaris equorum
-Clinical signs include: diarrhea, enteritis, respiratory issues & nasal discharge, dull hair coat & poor growth
-Extreme infections can be fatal; large worm burden, worm grow faster than
intestinal tract of the infected foal, impaction colic, intestinal perforation &
rupture
Does Parascaris equorum impact colic?
Yes
Parascaris equorum - Treatment & Control
-Clean mare’s udders & teats; provide clean nursing environment
-Dedicated pastures for foals; grazed by older animals w/low FECs, all subject to same anthelmintic regimen
-Effective drug therapy @ 2, 4, 6, 8 (months):
-Pyrantel pamoate (Early indications)‐ Single farms; few
-Fenbendazole (Early indications)
-Macrocyclic lactone (Widespread): high farm prevalence >80% and multiple continents
-Critically Ill animals treated with care: FBZ administered to kill worms gradually and allow for expulsion
Oxyuris equi “Equine Pinworm ”
-Medium size worms
-Sexually Dimorphic: Males (9 to 12mm) and females (40 to 150mm)
-Adult worms: long tail w/ acute distal end and muscular “Bulb” esophagus
-Adults parasitic in cecum, small & large colon
-Cosmopolitan distribution
-Horses of all ages
Lifecycle - Oxyuris equi “Equine Pinworm”
-Direct lifecycle: infection by ingestion of
embryonated egg
-Larvae hatch, penetrate colon wall, develop, return to lumen & reproduce
-Females deposit (cement) eggs in perianal folds
-Prepatent period ~ 5 months
-Eggs flake off skin, & adhere to buckets, mangers, stalls, curry brushes, etc.
-Infective after 4 to 5 days
developement
Clinical Significance - Oxyuris equi “Equine Pinworm”
-Females deposi t (cement) eggs in perianal folds
-Clinical signs include:
-Intense anal pruritis and itching,
-Rubbing hind end on stalls, fence posts
-Broken tail hair
-Behavioral issues
-Must be differentiated from mange and other causes of anal pruritus
Diagnosis - Oxyuris equi “Equine Pinworm ”
-Oval/operculated egg
-90x42 μm
-Observed on “ScotchTape” microscope slide preparation
-Occasionally seen on fecal examination
-Egg mass (8 to 60k ) in tail hair resembles dried “whipped/shaving cream”
Treatment & Control - Oxyuris equi “Equine Pinworm”
-Adult worms susceptible to treatment: 91% efficacy w/ Pyrantel @ 13.2 mg/kg (x2 the labeled dose), 96% efficacy w/ Ivermectin Paste @ 200μg/kg
-L4 larval stages were >99% susceptible with both drugs
-No evidence of drug resistance; contradicts anecdotal reports
-Successful treatment & control requires attention to hygiene: 1000’s of sticky eggs adhere to everything and use disposable wipes for cleaning affected animals
Strongyloides westeri “EquineThreadworm“
-Small adult worms in small intestine
-Only females parasitic
-Morphology & life cycle biology similar to canine species: homogonic life cycle and hetrogonic lifecycle
-Infection of foals: lactogenic route, -prepatent Period ~ 7 days of
life!
-Other routes of infection: ingestion of L3 and percutaneous
Clinical Significance - Strongyloides westeri “ EquineThreadworm“
-Primarily infection of foals: eggs disappear from feces by 24 weeks of age, and arrested in tissues for life
-Clinical disease:
-Diarrhea‐dehydration
-Poor growth
-Treatment to remove adults from small intestine:
-Supportive care
Equine Stomach Worms ”Draschia & Habronema
-Adult worms live in the stomach of horses
-Small worms, sexually dimorphic: males (8 to 14 mm) and females (13 to 22 mm)
-Obligate Indirect lifecycle:
-Transmission of infective larvae by fly intermediate host
-Larvae in cutaneous wounds
-Larvae in warm/moist openings & wound sites
-Adults in stomach & eggs /larvae passed in feces
-Ingested by maggots: larvae grow to infective stage as flies develop (metamorphose), trans‐stadial transmission
-Horses ingest flies accidentally in food/water
-Parasites penetrate mucosa and develop in stomach
-Prepatent period ~ 5 months
-Eggs (~45 x ~12μm) occasionally seen on
fecal flotation
Clinical Significance - “Equine Stomach Worms” Draschia & Habronema
-Disease process associated with deposition of larvae by Fly (Intermediate Host)
-Cutaneous Harbronemiasis Aka “Summer Sore”, “Swamp Cancer”,
-Granulomatous lesion persistent through the “Fly Season”
-Larvae associated with lesions
-Adult worms live within caseous, fibrotic nodules in stomach
Clinical Significance - “Equine Stomach Worms” Draschia & Habronema
-World‐wide (Cosmopolitan) distribution:
-United States, Europe, United Arab Emirates
-Infrequent due to historical suppressive use of Ivermectin
-Perhaps making a come‐back w/ transition to “Selective Deworming”
-Single dose macrocyclic lactone is usually
sufficient
-Concurrent fly control important
