Toxocara

Background

• Genus of nematode
• Includes two species of medical importance:
  • Toxocara canis, the dog roundworm
  • Toxocara cati, the cat roundworm
• Dogs/cats are the definitive hosts, while humans are incidental hosts
  • In humans, the larva are unable to mature into adult worms or to release eggs
• Distributed worldwide, particularly in low-resource settings with high numbers of feral dog or cat populations
• About 20% of the global population is seropositive, though there is variation
  • Africa 40%, Southeast Asia 34%, Western Pacific 24%, Americas 23%, Europe 11%, Eastern Mediterranean 8%
• Risk factors include contact with outdoor dogs and cat, and children

Clinical Manifestations

• Asymptomatic

Visceral Larva Migrans

• Most common in children less than 5 years of age
• Fevers, malaise, weight loss, respiratory symptoms, hepatomegaly, rash, lymphadenopathy
• Most commonly affects lung and liver, but can also affect cardiac and urinary systems
• Often see peripheral eosinophilia
• Pulmonary disease
  • Coughing, wheezing, dyspnea
  • May present as eosinophilic pneumonia or as asthma
• Liver disease
  • Fevers, abdominal pain, peripheral eosinophila
  • Liver lesions can mimic Fasciola hepatica, bacterial infection, and malignancy
  • Can be complicated by bacterial abscess
• Cardiac disease
  • Rare
  • Primarily myocarditis, but also pericarditis and Loeffler endocarditis

Neurotoxocariasis

• Invasion of larvae into the CNS
• Syndromes can include meningoencephalitis, myelitis, spinal abscess, optic neuritis, and cerebral vasculitis
• May present with epilepsy, cognitive impairment, and behaviour changes

Ocular Toxocariasis

• Painless (though painful in 30%) unilateral vision loss
• Photophobia and floaters
• On ophthalmoscopy, may see vitreitis, posterior of intermediate uveitis, traction retinal detachment, granuloma formation, endophthalmitis, optic neuropathy, and crystoid macular edema
• Vision loss is usually permanent

Common Toxocariasis

• Non-specific symptoms in seropositive patients
• Abdominal pain, anorexia, nausea, vomiting, lethargy, hedaches, myalgias, behaviour change
• May have eosinophilia

Management

• Albendazole 400 mg p.o. twice daily for 5 days
• Alternatively mebendazole, DEC
• Neoadjuvant corticosteroids should be given be antihelminthic therapy and continued throughout treatment for patients with: cardiac disease, VLM with severe peripheral eosinophilia, ocular infection, neurotoxocariasis
  • Followed by taper