Nematodes - Ascaridida - Ascaridoidea & Heterakoidea

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All ascarids

Parascaris equorum

Adults: Long 30cm, white to cream color, 3 large lips
Eggs: thick-walled, 90um
LC: direct, per os L2 eggs; hepatic tracheal migration
SOI: Small intestine
Pathogenesis: 1) perforation, 2) intestinal obstruction, 3) unthriftiness or production losses
Clinical signs: coughing, unthriftiness in young animals, weight loss, slow weight gain
Diagnosis: Fecal - eggs
Treatment: anthelminthics; post 60 days of age


Host specific.
Adults: large,10-30cm long, white to cream colored, 3 lips
Eggs: thick-walled, resistant eggs.
Infective stage: L2 in egg
Infect young animals.

Toxocara canis (Common roundworm, ascarid)

Canines. Zoonotic.
Adults: large, white, 10cm, single finger-like process on the tail of the male, mouth with 3 lips.
Egg: dark brown, round, thick pitted shell, 85x75um
LC: Direct, eggs w/L2 are infective, per os, transplacental or prenatal, transmammary, paratenic host
PPP: 3-5wks
SOI: small intestine
Pathogenesis: Moderate infections - larval migration, adults cause little reaction
Clinical signs:depends on age of dog, pneumonia, pneumonitis, eosinophilia, v d, intestinal obstruction, general malaise, unthriftiness, anemia, pot belly appearance.
Diagnosis: Fecal float
Treatment: environmental management and anthelmintics (fenbendazole, ivermectin)

Toxocara cati (Common roundworm, ascarid)

Felines. Zoonotic. 4% of strays in SKB.
Adults: large, white, 10 cm, arrow-head with posterior margins almost at a right angle to the body.
Eggs: thick-pitted shell, colorles in cat 60x80um
LC: direct, eggs w/L2 are infective, per os, transmammary, paratenic hosts,
SOI: small intestine
Pathogenesis: little migration
Clinical signs: depends on age, number, soi. pneumonia, eosinophilia, hypersensitization, digestive disturbances, instestinal obstruction, general malaise, unthriftiness, anemia, pot belly appearance.
Diagnosis: eggs on fecal float
Treatment: concentrate on kittens, treat for appropriate stage of adult. Visceral larva migrans rare but can occur.

Toxascaris leonina (Ascarid)

Canine and Felines.
Adults: 6-10cm
Egg: Slightly ovoid, smooth thick shell
LC: Direct. Per os (PPP 10-11wk), Paratenic host
SOI: Small intestine
Path: Moderate infections - no apparent damage to tissues.
CS: None, vomition, diarrhea, intestinal obstruction, general malaise, unthriftiness, anmeia, pot belly appearance.
Dx: Fecal float, necropsy
Tx: Adequate hygiene, Ivermectin

Ascaris suum

Swine roundworm
FH: pigs, humans. ZOONOTIC
PH: earthworm or dung beetle
Adult: large, white, 3 lips (female 40cm)
Egg: 70um, yellow, ovoid, thick pitted shell
LC: direct. egg psssed, develops to egg with L2 (infective stage); consumed by FH or PH, hatches in SI, hepatic tracheal migration.
PPP: 6-8wks
SOI: adults in SI; larval migration; patent infection in humans
PATH: larval migration causes "white spots" (localized lesions 1cm in diameter), larvae in lungs may lead to transient pneumonia, intestinal disturbances depending on load, poor feed conversion, slower weight gains, delay to market
Adults- obstruction, bile duct - jaundice and carcass condemnation
CS: diminished weight gain, intestinal or biliary obstruction, piglets under 4mo - transient pneumonia
Dx: ascarid in fecal exam float with zinc sulphate or magnesium sulphate
Tx: associated with outdoor and indoor production. most persistent and most resistant, in pasture eggs may be pinfective for 6-7 yrs. older animals have less helminthology and excrete fewer eggs than younger ones. use parasiticides

Ascaridia spp

FH: domestic fowl and wild birds
PH: earthworm
Adults: largest nematode in poultry (females 7-12cm, males 5-8cm), 3 lips
Eggs: oval, smooth shells, 73-92 x 45-57um
LC: direct. infective stage is egg with L2, hatches in SI, parasitic stage is nonmigratory, in histotropic stage larvae embed in mucosa of SI, duration depends on number of ingested infective eggs; nematodes develop in the small intestine. PH may also ingest eggs. Establishment of infection influenced by age of chicken, size of infective dose, age of the eggs, and sex & diets of the chickens.
SOI: small intestine
PATH/CS: weight loss, partial or total obstruction of the duodenum or the jejunum. Pronounced in chickens up to 3 mo of age. CS include anorexia, drooping wings, ruffled feathers, weight loss, decreased egg production, anemia, diarrhea, and mortality. Enteritis or hemorrhagic enteritis w/ large numbers.
Dx: eggs in feces (poss. Heterakis), necropsy

Heterakis spp. (H. gallinarum, H. isolonche, H. dispar)

Poultry cecal worm
FH: domestic & wild fowl
PH: earthworms and houseflies
Adults: small in size, male 1cm, female 1-1.5cm
Eggs: 65-80 x 35-46um, thick, smooth shell, difficult to differentiate from A. galli
LC: Direct, earthworms and houseflies are mechanical transports. Eggs pass out with feces and develop to L2 in egg. Host ingests infective eggs, eggs hatch in small intestine, larvae reach cecum and develop to adults.
PPP: 24-30d
SOI: lumen of cecum
PATH/CS: H. gallinarum - most common nematode of poultry, relatively non-pathogenic but transfers the protozoon Histomonas meleagridis "blackhead" in turkeys.
H. isolonche - pathogenic. cecal inflammation, thickening of mucosa with petechial hemorrhages, diarrhea, emaciation, & death
Dx: by accident during fecal exam, necropsy

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