2.3 Nematodes - roundworms (continued)

What is Baylisascaris procyonis?

The raccoon roundworm.

What is the definitive host of Baylisascaris procyonis?

The raccoon.

What is the alternative definitive host of Baylisascaris procyonis?

The canine (a host in which the parasite can still sustain itself).

What are incidental hosts of Baylisascaris procyonis?

Many small mammals, rodents, and birds.

Is Baylisascaris procyonis zoonotic?

Yes.

What is the PPP of Baylisascaris procyonis when infection occurs via egg ingestion?

7-10 weeks.

What is the PPP of Baylisascaris procyonis when infection occurs via ingestion of a larval‑infected paratenic host?

5 weeks.

What medications can treat Baylisascaris procyonis?

Broad‑spectrum anthelmintics such as pyrantel, ivermectin, and febantel (fenbendazole).

How can Baylisascaris procyonis be prevented?

Avoid keeping raccoons as pets, avoid raccoon‑frequented areas, use monthly preventatives, and discourage feces ingestion.

What is Parascaris equorum?

The equine roundworm.

What is the definitive host of Parascaris equorum?

Horses, typically foals.

What is the PPP of Parascaris equorum?

75-80 days.

What is notable about the size of Parascaris equorum?

It is the largest equine nematode.

What clinical signs can heavy Parascaris equorum infestations cause?

Unthriftiness, depression, potbellied appearance, colic, and nasal discharge.

How is Parascaris equorum diagnosed?

Observation of eggs on fecal flotation.

How can Parascaris equorum be prevented?

Pasture rotation for foals, washing feeders and waterers.

What medications are used to treat Parascaris equorum?

Ivermectin and pyrantel.

What is Ascaris suum?

The roundworm of pigs.

What are the paratenic hosts of Ascaris suum?

Dung beetles and earthworms.

Where does Ascaris suum live in the host?

The small intestine; it is the largest nematode found there.

Can Ascaris suum cause intestinal obstruction?

Yes, in heavy worm loads.

Is Ascaris suum zoonotic?

Yes.

What is the PPP of Ascaris suum?

6-7 weeks.

How resistant are Ascaris suum eggs?

Very resistant to chemicals; sensitive to dryness, sunlight, and heat.

How long can Ascaris suum eggs survive in the environment?

5-11 years under optimal conditions.

What clinical signs can Ascaris suum cause?

Reduced growth, weight loss, coughing, abdominal breathing, "thumps," and liver damage.

How is Ascaris suum diagnosed?

Eggs on fecal float, worms in feces, milk spots on liver, or adult worms in intestine at necropsy.

Why can fecal sample collection be difficult in pigs?

Pigs are coprophagic and may consume the sample.

What causes "milk spots" on the liver in Ascaris suum infection?

WBC accumulation from larval migration.

What treatments may be used for Ascaris suum?

Supportive therapy, antibiotics for respiratory debris, ivermectin, and pyrantel.

Baylisacaris procyonis life cycle

1. Unembryonated eggs shed in environment

2. Raccoons ingest infective egg or paratenic host

3. Infective egg hatches infective larvae within host

4. Larvae are carried by blood to lungs, migrate up trachea and are swallowed

5. Larva develop into adult stage once back in small intestine

When and where do Baylisacaris procyonis develop into infective L3 stage

in environment in 2-4 weeks

paratenic hosts for baylisascaris procyonis

birds and mammals

True or False: Dogs can be an accidental host for Baylisascaris procyonis

True

Life cycle of parascaris equorum

1. eggs passed in feces

2. larvae grow and molt within the eggs

3. Horse ingests eggs and travel to intestines where they hatch

4. Larvae migrate to liver through hepatic portal vein

5. larvae are carried to lungs by circulatory system

6. Once in lungs, they are coughed up and swallowed

7. Larvae mature into adults and feed on blood in intestines

Ascaris suum life cycle

1. Eggs are ingested and travel to intestine

2. Larvae hatch and penetrate intestinal wall into circulation

3. They are carried by circulatory system to the alveoli and bronchi of lungs

4. They are coughed up and swallowed into small intestine where they mature into adults

5. eggs can stay dormant in winter and resume development in spring when temps rise

Describe MOST ascarids life cycle

1. eggs ingested

2. L3 larvae hatch in small intestine

3. Larvae penetrate intestinal wall

4. Travel via bloodstream to liver --> lungs

5. Break into alveolie

6. coughed up

7. swalllowed into GI tract

8. mature into adults in small intestine