Page 100 - Medical Parasitology_ A Textbook ( PDFDrive )

Intestinal Nematodes: Non-Soil Transmitted Helminths 93

Visceral Larva Migrans (VLM)

This condition is caused by the migration of nematode larvae of dogs and cats in the
visceral organs. Human is an abnormal host and the parasite cannot develop into
adults. The most common cause is the dog ascarid, Toxocara canis, and less often
the cat ascarid, T. cati. Human acquires infection by the accidental ingestion of
Toxocara eggs.

Pathogenesis and Clinical Features
When the infective eggs from faeces of dogs and cats are ingested by human, the
eggs hatch in the small intestine, releasing larvae which penetrate the gut wall and
migrate to the liver. They may migrate via circulation to other organs such as lungs,
brain or eyes. Since human is an abnormal host, they do not develop into adults.
Granulomatous foci are produced around dead larvae. Clinical manifestations
depend on the sites affected and the degree and duration of infection. It is more
frequently reported in children due to habit of eating dirt (pica). Fever, hepatomeg-
aly, pneumonitis and hyperglobulinaemia are the common findings. There is persis-
tent high eosinophilia. In ocular larva migrans, patients may also develop
retinochoroiditis. Retinochoroiditis may be misdiagnosed as retinoblastoma.

Diagnosis
1. Serodiagnosis
2. Biopsy
Not an effective method.

Treatment
Thiabendazole (25 mg/kg twice/day for 5–7 days) is suggested in severe symptom-
atic cases. Diethylcarbamazine (DEC) has also been recommended.

Prevention and Control
1. Deworming of dogs and cats
2. Personal hygiene
3. Prevent children from eating dirt (pica)

Intestinal Nematodes: Non-Soil Transmitted Helminths

Enterobius vermicularis

Common name Pinworm

Distribution
It is worldwide in distribution and commonly affects children.