Trichinellosis

Trichinellosis (trichinosis) is a parasitic disease caused by Trichinella nematodes (T. spiralis, T. nativa, T. britovi, T. pseudospiralis, T. nelsoni), acquired by eating undercooked meat containing encysted larvae.

• Sources: pork, wild boar, bear, walrus, horse, and African wildlife (T. nelsoni in warthog and bush pig).
• Outbreaks are typically associated with communal meals; incubation about 1 to 2 weeks (range 1 to 6 weeks).
• Complications in heavy infection: myocarditis, encephalitis, and pneumonitis; mortality under 1% with treatment.

• Intestinal phase (days 1 to 7): nausea, diarrhoea, and abdominal cramps.
• Muscle invasion phase (weeks 2 to 6): fever, severe myalgia, periorbital and facial oedema (classical), conjunctival haemorrhage, subungual splinter haemorrhages, and rash.
• Eosinophilia (often over 20%), raised CK and LDH.
• Cardiac (arrhythmia, heart failure) and neurological involvement are the main causes of death.

• Clinical features plus exposure history, with eosinophilia and elevated muscle enzymes (CK, LDH).
• Serology (ELISA, Western blot; may be negative for 3 to 5 weeks).
• Muscle biopsy (deltoid or gastrocnemius) showing coiled larvae within nurse cells (after week 3); PCR.
• ECG and echocardiography for myocarditis; CSF and MRI if neurological symptoms.
• Exclude myositis, viral infection, toxocariasis, strongyloidiasis, fascioliasis, and drug reactions.

• Albendazole 400 mg twice daily for 8 to 14 days (children 10 to 15 mg/kg/day divided), or mebendazole 200 to 400 mg three times daily for 3 days then 400 to 500 mg three times daily for 10 days. Most effective if started early in the intestinal phase; less effective against encysted larvae.
• Prednisolone 30 to 60 mg daily for 10 to 15 days (tapered) for severe muscular, cardiac, or CNS involvement, always together with an anthelmintic.
• Analgesics and supportive care; treatment of myocarditis and heart failure; seizure management.
• Pregnancy: albendazole is avoided in the first trimester, and the risk benefit is individualised.
• Prevention: cook meat to an internal temperature of 71 degrees Celsius (160 degrees Fahrenheit), freezing is unreliable for arctic species; meat inspection.