Higher infection rates for children (especially boys and blacks), probably due to patterns of pica
Children are higher risk than adults for developing ocular or visceral forms of VLM
Etiology
Toxocara Canis (helminth: dog ascarid): dog infection (especially puppies) is common in temperate and tropical zones
ELISA for larval antigens show that 2.8% of dog population in USA is infected
Toxocara Cati (helminth: cat ascarid):
Physiology
Ingestion of soil contaminated by eggs (deposited by infected dogs or cats/ require weeks of incubation in soil) -> hatched larvae in intestine penetrate vessels -> travel to lungs -> travel to liver, brain, heart, muscle, eyes -> inflammatory response with necrosis, hemorrhage, granulomas
Infection may persist for up to 10 years in animal models
Life cycle is usually aborted at larval stage in adult dogs (but transplacental passage of larvae to puppies leads to fecal contamination of soil)
Diagnosis
Sputum GS/Cult+Sens:
Lung Bx: definitive diagnosis is finding of T. Canis larvae in tissue (but this is rarely possible)
May show granulomas with intact or fragmented larvae
CXR/Chest CT patterns (CXR is abnormal in 40% of cases):
Alveolar infiltrates (>30% of cases): typically bilateral small peribonchial infiltrates (which may be migratory) > subsegmental or segmental infiltrates