Ascarids of dogs + cats Flashcards
What are the different ascarids?
*Toxocara canis
*Toxocara cati
*Toxascaris leonina
What does Toxocara canis affect? Zoonotic?
Dogs + Foxes
Zoonotic!
What does Toxocara cati affect? Zoonotic?
Cats
Zoonotic?
What does Toxascaris leonina affect? Zoonotic?
Cats + Dogs
Not Zoonotic
What are common characteristics of ascarid nematodes?
- Large, white, fleshy worms
- Direct life cycles
- May include paratenic host
- Infective stage = egg containing the L2
- Eggs highly resistant
- Infections usually stimulate strong immunity
What are paratenic hosts? definition
not essential to life cycle but some
development may occur
(Intermediate host = essential)
What is the morphology of adult worms?
- Large, white, fleshy worms
- Found in small intestine
- Females produced ~ 200,000 eggs/per day
- Strong, effective immune response
What is the morphology of Toxocara spp eggs?
- 80 μm
- Spherical
- Thick-shelled, brownish in colour
- Morula fills the egg
What is the morphology of Toxascaris leonina eggs?
- 80 μm
- Oval
- Thick-shelled
- Morula doesn’t fill the egg
What are the 4 routes of infection of Toxocara canis?
1.Direct transmission - Puppies <12wks
2.Paratenic Transmission
3.Transplancental transmission - >6m/o
4.Transmammary transmission
Which ascarids have a large cervical aeli?
T. cati
What does the male T. canis worms have at tail end?
fingerlike projection at tail end
What is the direct transmission route of infection?
- Egg containing infective larvae (L2/L3) ingested
- Hepato-tracheal/pulmonary migration – larvae migrate via liver to lungs, coughed up and swallowed, larvae develop through L4 – L5 (adult); PPP ~6 weeks.
What is the paratenic route of transmission?
- Paratenic host ingests eggs; Paratenic host ingested; Mucosal migration to gut; PPP 4 weeks
What is the transplacental transmission route of infection?
- L2 migrates into tissues, becomes encysted and development is arrested.
- Pregnancy – reactivates L2, crosses the placenta to the foetal liver; PPP 3 weeks.
What is the transmammary route of infection?
- L2 in milk; No migration – larvae develop into adults in intestine.
What is the lifecycle / route of infections of Toxocara cati?
- Ingestion of eggs containing L2 – migration
- PPP 8 weeks
- Ingestion of paratenic host – no migration
- PPP 6 weeks
- Transmammary transmission – no migration
- PPP 2-3 weeks
- No transplacental transmission
What is the life cycle / route of infection of Toxascaris leonina?
- Dogs and cats
- No migration
- Infection by ingestion of
- Egg containing L2
- Paratenic host
- No transplacental transmission
- No transmammary transmission
What are the clinical signs in adult dogs?
ASYMPTOMATIC
What are the clinical signs in puppies?
- Heavy worm burdens in puppies
- Pot bellied
- Poor weight gain
- Intestinal obstruction
- Pneumonia associated with pulmonary phase
- No diarrhoea
How is ascarids diagnosed?
- Age of dog/cat
- Clinical signs
- Eggs in faeces (salt flotation often not necessary)
- Adult worms may be passed or vomited
How is ascarids controlled?
- Intestinal stages susceptible to benzimidazoles and macrocyclic lactones
- Dogs: Fenbendazole given daily from 42 days gestation can prevent transplacental transmission
- Cats: Emodepside ~7 days before expected parturition to prevent lactogenic transmission.
- Regular worming – 2, 4, 6 weeks of age; 3, 6 months and then every 3-6 months.
- Cats – no transplacental transmission, can start treatment at 3 weeks of age
How do you reduce the zoonotic risk of ascarids?
- Eggs are highly resistant and long lived
- Prevent environmental contamination
- Educate pet owners, regular worming of pets
- Hygiene (hand washing)
- Regular worming:
- Modern macrocyclic lactones
= Selamectin, milbemycin, moxidectin - Fenbendazole, Pyrantel
- Emodepside (cats)
Describe the migration of L2 ascarid larvae in the cat and dog host.
Hepato-tracheal migration, where the L2 hatches from the egg in the gut of the dog/cat, pentetrates though the wall of the small intestine and migrates to the liver and is carried to the lungs in the blood stream. The L2 moults to the L3 and is coughed up and swallowed, maturing to the L4 the L5/adult worm in the small intestine.
What is the most common way in which dogs are infected with Toxocara canis?
Via transplancental transmission. L2, arrested in the muscles of the bitch, are activated during pregnancy and migrate across the placenta to the lungs of the foetus. As the puppies are born, the L2 moults to the L3, is coughed up, swallowed and matures to the adult worm in about three weeks.
How do differentiate between T. canis, T. cati and T. leonina adult worms?
Male Toxocara spp. worms have a small appendage on its posterior end which is absent in T. leonina worms. T. cati has an inflated cervical alae, it is sometimes referred to the arrow-head worm.
What treatment is used to control ascarids in dogs and cats?
Benzimidazoles
Macrocyclic lactones
