Toxocara

• Toxocara Species

  Zoonotic disease from stray dogs and cats
• Toxocariasis

  Disease caused by Toxocara larvae

  
• Toxocara larvae


  • Causing the disease

  
• Definitive host


  Host in which the parasite reaches sexual maturity and reproduces

  
• Toxocara canis

  Dog roundworm
• Toxocara cati

  Cat roundworm
• Life cycle of Toxocara

  1. Completed in dogs and cats as definitive hosts

  2. Stops in the absence of dogs or cats

  
• Transplacental transmission

  Reactivation of encysted eggs in pregnant female dogs
• Transmammary transmission


  Transmission of larvae through milk from infected female dogs
• Toxocariasis is more common in children than adults
• Reasons for higher prevalence in children

  • Tendency to play in soil
  • Exhibit geophagia or soil eating
• Toxocariasis is common where dogs and cats are not dewormed
• Paratenic host

  Rabbits and small mammals
• Definitive host

  Dogs or cats
• Infective stage (to humans)

  • Embryonated ova
  • Encysted larvae in small mammals
• Life cycle of Toxocara canis and Toxocara catus

  1. Definitive host lays unembryonated eggs

  2. Eggs undergo embryonation to become infective

  3. Infective ova ingested by definitive or paratenic host

  4. Larvae hatch and penetrate gut wall in definitive host

  5. Larvae encyst in tissues of definitive or paratenic host

  
• Reason for larval migration in young dogs is still unknown
• Encysted larvae in older dogs can reactivate during pregnancy
• Transplacental transmission is more common in Toxocara canis, while transmammary transmission is more common in Toxocara cati
• Visceral Larva Migrans (VLM)


  Migration of larvae and death in different organs, causing intense inflammatory response
• Neurological Toxocariasis


  Formation of a solitary mass in the brain, causing seizures, encephalitis, optic neuritis, eosinophilic meningitis
• Ocular Larva Migrans (OLM)


  Unilateral visual impairment and strabismus in children, with potential for retinal invasion
• Covert Toxocariasis (CoTOX)


  Less specific syndrome or may be asymptomatic
• Diagnosis of toxocariasis

  1. Definitive: Tissue biopsy demonstrating larvae

  2. Other tests: ELISA for IgG, PCR

  3. Stool exam not useful

  
• Treatment

  • Most patients recover without therapy
  • For severe cases: Albendazole or Mebendazole plus anti-inflammatory drugs (steroids)
• Prevention and control

  1. Control and capture of stray dogs and cats

  2. Cleaning up feces from soil and pavements

  3. Fencing gardens to prevent contamination

  4. Washing vegetables thoroughly

  5. Avoiding consumption of raw/undercooked meat

  6. Hand washing

  7. Deworming of dogs and cats