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Toxocara canis

Toxocara canis. Sidney Milliron Aaron Bettenhausen. Taxonomy. Kingdom: Animalia Phylum: Nematoda Class: Secernentea Order: Ascaridida Family: Toxocaridae Genus: Toxocara Species: Toxocara canis. Geographic range. World wide distribution

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Toxocara canis

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  1. Toxocaracanis Sidney Milliron Aaron Bettenhausen

  2. Taxonomy • Kingdom: Animalia • Phylum: Nematoda • Class: Secernentea • Order: Ascaridida • Family: Toxocaridae • Genus: Toxocara • Species: Toxocaracanis

  3. Geographic range • World wide distribution • Found commonly in all domestic dogs and other canids • Possible to have prenatal infections of puppies

  4. Hosts • Primary host is dogs • Adults are infected upon infestation of embryonated eggs, or by eating rodents infected with visceral larva migrans • Worms can penetrate the placenta and infect unborn puppies • Puppies can be born infected • Puppies can also become infected via the transmammary route

  5. Other hosts • If a rodent eats the embryonated eggs the worms will hatch and begin migration before going dormant • If the rodent is then eaten by a dog the dog can become infected • Rodent acts as paratenic host • Rodents develop visceral larva migrans • Humans who ingest the eggs also develop visceral larva migrans

  6. Egg • Eggs • Brownish • Almost spherical • Surficial pits • Unembryonated when laid

  7. Larvated Eggs – Infective Stage

  8. Larvae • Found in Intestines, Circulatory, Lungs and Esophagus of Hosts

  9. Adults • Adults • Large (M=4-6cm; F=6.5-15+cm) • Have 3 lips • Prominent cervical alae in both sexes

  10. 3 Prominent Lips

  11. Life Cycle • Adult worms live in small intestine of their host • Produces prodigious numbers of eggs • Eggs are passed in feces • Develop into L3 in 5-6 days under optimal conditions

  12. Canine Oral ingestion • In Puppies: • Worms hatch and migrate through the portal system and lungs • Get swallowed and find their way back to intestine • Can be fatal to puppies due to malnutrition • In older dogs (secondary immune response) • Juveniles do not complete the lung migration • Wander through the body, eventually entering a developmental arrest for a long periods • Most adult dogs show no symptoms when infected and gain an increased immunity to reinfection as they age

  13. Life Cycle

  14. Infection during canine pregnancy • Dormant juveniles are activated by host hormones late in pregnancy • Reenter the circulatory system • Carried to placentas • Penetrate through to the fetal bloodstream • Complete lung migration en route to the intestine • Juveniles can also be passed by the trasmammary route, in mother’s milk

  15. Other routes • If a rodent or other mammal eats embryonated eggs • Juveniles begin to migrate but then become dormant and continues it’s developmental arrest • If rodent is eaten by a dog • Worms promptly migrate through the lungs to the intestine or into tissues to continue their wait, depending on age.

  16. Visceral Larva Migrans • Occurs when nematode gains entry into paratenic host • They do not complete the normal migration but undergo developmental arrest • Begin an extended, random wandering through various organs and tissues of the body

  17. Pathogenesis • Juveniles provoke a delayed-type hypersensitivity reaction in paratenic hosts • Eventually they will find their way to the brain • In other tissues, juveniles will form a granuloma • Can cause chronic ocular inflammation, as well as retinal granulomas • Rarely can cause eosinophilicmeningoencephalitis

  18. Visceral Larva Migrans • Occurs when a mammal other than the intended host (Dogs) ingest the eggs • Worms hatch and begin migration but eventually undergo developmental arrest • Worms begin a randomly wandering through the body • Can be caused by a number of different species however Toxocaracanisis the most common species that causes this disease in humans • In experimental hosts juvenile worms seem to prefer residing in the brain.

  19. Symptoms in Humans • Fever, pulmonary symptoms, hepatomegaly, and eosinophilia • Worms migrate indiscriminately to and from any organ including but seem to prefer the liver • Can cause blindness if they migrate to the eye • Can cause neurological symptoms • Extent of tissue damage is proportional to the numbers of juvenile worms in the body

  20. Prevalence of infection • In the united states 4.6-7.3% of children ages 1 to 11 years old have Visceral Larva migrans • Up to 30% infection has been found in African American children of low socioeconomic status • Up to 34% infection has been found in Irish school children • In some developing tropical countries the rates of infection among children can be around 50 to 80%

  21. Diagnosis • An ELISA using secretory-excretory antigens • A liver biopsy might reveal a juvenile surrounded by a granuloma • Infected patients may present with high eosinophilia

  22. Treatment and Control • Mebendazole • Periodic deworming of household pets • Proper disposable of animal feces • Don’t let your dog eat rodents • Covering sandpits in public parks when not in use

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