Lecture 15 - Equine Internal Parasites

What animals are trichostrongylus axei found on? What is the prepatent period?

-Horses, pigs, ruminants

-Prepatent period: 25d

What does a T. axei infection cause?

-Gastritis with hyperemia/erosions

-Diarrhea

How is T. axei diagnosed?

Fecal egg count (can’t differentiate from strongyle eggs)

How do you prevent/control T. axei?

-Prevention improbable/unnecessary

-Control based on fecal egg count and treat if necessary

What animals are Habronema muscae found?

Equids

What are the clinical signs of H. muscae?

-Summer sores from skin lesions

-Granulomas, necrosis, and mineralization

How is H. Muscae diagnosed?

-Eggs/larvae not easily detected in feces

-Biopsy non healing cutaneous lesions

How do you prevent and control H. muscae?

-Prevention: fly control and wound care

-Control: macrocyclic lactones and corticosteroids

What does Draschia megastoma cause?

Caseous abscess in fundus of stomach

Where are Gasterophilus intestinalis found? G. nasalis? Which one is more common?

-G. intestinalis: larvae in non-glandular part of stomach, eggs on distal legs, neck and withers

-G. nasalis: larvae in pylorus, eggs in submaxillary region

What is the pathogenesis of gasterophilus spp.?

Rarely clinical but may see erosions/ulcerations on gastric mucosa

How do you prevent and control gasterophilus spp?

-Prevent - manually remove eggs

-Control - ivermectin

Are males or female Strongyloides westeri parasitic? How do they reproduce?

-Females

-Reproduce by pathenogenesis (asexual reproduction)

How is S. westeri transmitted?

-Lactogenic transmission to foals with arrested larvae

-Oral ingestion or percutaneous invasion

What is the pathogenesis of S. westeri?

-Small intestinal enteritis

-Villous atrophy from adult worms in mucosa

-Dermatitis of distal extremities

How is S. westeri prevented and controlled?

-Adult horses are immune, mares are carriers

-Give anthelmintics to mares after foaling

Which roundworm most commonly affects equids? What age does it commonly affect?

-Parascaris univalens

-Usually affects foals

What is the pathogenesis of P. univalens?

Ingested eggs hatch in small intestine → larvae migrate to the liver than lungs → coughed and swallowed

What are the clinical signs of P. univalens?

Limited clinical signs since immune response generally clears infection

How is P. univalens prevented and controlled?

-Prevention: sanitation of paddocks, fecal pickup, rotate pastures

-Control with benzimidazoles and monitoring fecal egg counts?

What species composes about 99% of eggs passed in manure of pastured horses?

Strongyles (“cyathostomes”)

What are two types of strongyles? What are their primary sites?

1. Small strongyles - cecum, right and left ventral colons

2. Large strongyles - arteries (including cranial mesenteric artery)

What is an issue with treating strongyle infections?

Resistance is high due to short prepatent period

What are Anoplocephala perfoliata? What is the intermediate host? Where do they like to attach?

-Horse tapeworm

-Intermediate host: oribatid mite

-Attach to ileocecal junction