Lecture 11 - Nematodes of ruminant GI tract

What is the HOT complex for abomasal parasites?

H: Haemonchus contortus

O: Ostertagia ostertagi (Teladorsagia)

T: Trichostrongylus axei

What is the general life cycle of nematodes?

-Adult nematodes inhibit GIT

-Eggs produced by females and are passed in feces

-Eggs → L1 → L2 → L3 (7-10 days)

-Ruminants ingest L3

Which nematodes have a direct life cycle?

Trichostrongyles, Oesophagostomum, and Bunostomum

What does L3 penetrate in Haemonchus and Trichostrongylus?

Mucous membrane

What does Ostertagia L3 penetrate? What does it cause?

Gastric glands causing abomasal lesions (moroccan leather)

What is the parasitic part of the life cycle of Oesophagostomum?

-Infective L3 penetrate lamina propria of intestinal wall

-Inflammatory response causes fibrous nodules

-Larvae emerge into intestinal lumen and mature

How does L3 of Bunostomum cause infection?

Skin penetration → venous blood → heart and lungs → coughed and swallowed → small intestine

What clinical signs may you see with the HOT complex in larval stages?

-Reduced appetite

-Reduced digestive capability of abomasum

What is hypobiosis?

Dormant stage of parasites

What clinical signs may you see with Haemonchus, bunostomum, and oesophagostomum infections?

-bottle jaw (submandibular edema)

-anemia

Which nematodes are blood sucking?

-Haemonchus

-Bunostomum

-Oesophagostomum

Where are Strongyloides papillosus adults found? What animals are they an issue in?

-Wall of small intestine

-Issue in ruminants less than 4-5mo

What can heavy infections of Strongyloides papillosus cause?

Catarrhal enteritis and severe diarrhea

What eggs are these?

Toxocara vitulorum

What is the life cycle of Toxocara vitulorum in calves? In cows?

-Calves: eggs swallowed and hatch in intestine OR L3 ingested in colostrum/milk → Eggs migrate through tissues to lungs/trachea → coughed and ingested → Mature in small intestines → Released in feces

-Cows: eggs swallowed and hatch in intestine → tissue migration → infect fetus (if pregnant) → mammary gland → colostrum/milk

What is the pathogenesis of Toxocara infections?

-Migrating larvae may cause damage to liver and lungs

-Potential intestinal lumen obstruction with heavy worm burden

-Diarrhea and reduced weight gain

-Parasites expelled by 5 months

How are Toxocara infections diagnosed and controlled?

-Eggs in feces

-Increased sanitation

Where in the GIT are Trichuris ovis and Trichuris discolor found? In what species?

-Cecum and upper colon (not pathogenic but common)

-Cattle, sheep and goats

How are trichuris ovis and trichuris discolor diagnosed?

Eggs in feces

Where is Gongylonema pulchrum (gullet worm) found?

Mucosa of esophagus or in lumen of rumen

Where is Gongylonema verrucosum found? What is the intermediate host?

-Found in rumen, reticulum or omasum

-Intermediate host: coprophagous beetle