Visceral Larva Migrans

Epidemiology

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

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):

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)

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
Albumin: globulin ratio: decreased
Total IgG and total /IgM: increased
Isohemagglutinin titer: increased anti-A (>1:400)/ increased anti-B (>1:200)
- Seen more commonly in Toxocara Canis infection than in other nematode infections
Ab to Toxocara Canis: present in 28.8% of asthmatic children (compared to 6.4% of non-asthmatic children)
ELISA larval stage antigens: following absorption to remove cross-reacting roundworm antigens, test is specific
CBC: marked eosinophilia (usually >30%/ eosinophilia present in almost all cases)/ leukocytosis
Skin testing: not useful
Stool exam: not useful (since organism does not mature to reproductive stage in human)
Liver Bx: definitive diagnosis is finding of T. Canis larvae in tissue (but this is rarely possible)
- May show granulomas with intact or fragmented larvae

Asthma, Bronchiolitis, or Pneumonia-Like Presentation
- Cough and wheezing (present in 20-85% of cases)

Diethylcarbamazine (2 mg/kg TID x 7-10 days) or thiabendazole (25 mg/kg BID x 5 days): preferred treatments
Steroids: usually used in combination with an anti-helminthic