Ascarids

Found in the small intestine. Females lay large numbers of resistant eggs. L2 develop inside the egg, larvae in egg infective stage. Direct life cycles. 

• Hepatotracheal migration which causes a profound inflammatory response. The adults browse on intestinal contents resulting in mechanical blockage due to size. 
• No Mucosal Damage. 
• Susceptible to all anthelmintics. 

Ascaris Suum- see pigs. 

Poultry Ascarids- see poultry. 

Horse Ascarids- see horses (parascaris equorum). 

Toxocara Canis

Life Cycle

• Development outside the host takes 2 weeks. 
• PPP= 4-5 weeks or 3 weeks if prenatal inf. 

Infection Routes 

• Puppy ingests eggs directly. Hepato-tracheal migration. 
• If the puppy is above 5/6 weeks old the L2 larvae migrate to the muscles where they remain arrested and viable. By 6 months of age, all larvae ingested do this. 
• If an adult female is infected, at 42 days gestation the L2 react and leave the muscles crossing the placenta to affect the fetus. L2-L3 in foetal lung and then matures in the gut. PPP= three weeks. 
• Transmammary transmission. 
• Paratenic host-> L2 ingestion by dog.

Disease

• Diagnose by age, clinical signs, eggs, or adult worms may be passed or vomited.
• Heavy puppy worm burden-> pot belly, poor weight gain & intestinal obstruction. 
• No diarrhoea. 
• Human toxicariosis can cause unilateral blindness.

Treatment 

• Decrease zoonotic risk by decreasing environment contamination with eggs.
• Dose older dogs annually and bitch post whelping.
• Programme to prevent transplacental transmission (fenbend) costly.
• Worm puppy 2, 4, 6 weeks of age, and then 3, 6 months and then annually. 

Toxocara Cati

• Ingestion of L2 & migration. 
• Ingestion of paratenic host/transmammary= NO migration.
• No transplacental transmission. 

Toxoascaris Leonina

• Cats and dogs.
• Mixed infection and no migration.
• Eggs in faeces.
• L2= 3-4 week development.
• Infection via L2 in the egg or L3 in mice.
• No prenatal inf. 
• 10 week PPP (8 week if paratenic host).

T.Vitulorum 

• Cattle and buffalo.
• Tropics.
• Increasing UK reports.
• Transmammary inf.
• Poor thrift & weight loss.