II. Epidemiology
- U.S. infections are now rare
III. Pathophysiology
- Trichinella spiralis is a parasitic Roundworm found in carnivorous mammals (esp. swine and rats fed raw garbage)
- Humans are infected by consuming undercooked pork infected with Trichinella encysted larvae
- In addition to pork, other ingested meat sources include wild boar, bear, deer or ground beef
- After ingestion, larvae emerge from their cysts within the host's Small Intestine
- Cysts mature into adult worms, male and female, who then mate
- After mating, adult worms are passed in the host's stool
- Female adult worms penetrate the intestinal mucosa where they produce thousands of larvae
- Larvae invade the host's bloodstream and infect skeletal Muscle and various other organs
- Larvae encyst within skeletal Muscles where they may remain dormant for years to decades
- Larvae may also infect cardiac Muscle or Central Nervous System (may be fatal)
IV. Symptoms
- Often asymptomatic with initial infection
- Gastrointestinal symptoms (most common, occurs with adult worm penetration of intestinal mucosa)
- Diarrhea
- Abdominal Pain or cramping
- Nausea or Vomiting
- Fever
- Systemic Symptoms (uncommon, occurs with larvae systemic spread to Muscle)
- Fever
- Myalgias and Myositis
- Eosinophilia
- Circumorbital edema
V. Labs
- Trichinella spiralis Antibody Testing
- Unreliable in first 3 weeks of infection
- Obtain 2 specimens, 2 to 3 weeks apart (consult CDC resource below)
- Other variable findings with Muscle invasion
- Complete Blood Count with Eosinophilia
- Lactate Dehydrogenase increased
- Hypergammaglobulinemia
VI. Diagnostics
-
Myositis
- Serum Creatine Kinase increased
- Muscle biopsy of Myositis location may demonstrate larvae
- Suspected CNS involvement
- Brain imaging (e.g. MRI Brain)
VII. Management
-
Albendazole
- Adult (and age >6 years): 400 mg orally twice daily for 8 to 14 days
- Child age 1 to 6 years: 5 to 10 mg/kg divided twice daily orally for 10 to 15 days
- Asymptomatic or mild symptoms may not require treatment
- Effective for enteric stages of infection (but does not affect Muscle larvae)
- Mebendazole or the less tolerated Thiabendazole may be used as an alternative
-
Prednisone
- Consider with Albendazole in patients with severe systemic symptoms
- Prednisone (adult dose) 30 to 60 mg orally daily for 10 to 15 days or until symptoms improve
VIII. Prevention
- See Prevention of Foodborne Illness
- Full cook or freeze pork prior to ingestion
IX. Complications
- CNS or cardiac Muscle infection
- Risk of fatal disease
X. Resources
- CDC Parasite Hotline
- Rawla (2023) Trichinella spiralis Infection, StatPearls, Treasure Island, FL
XI. References
- Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 362-81
- Pyzocha (2023) Am Fam Physician 108(5): 487-93 [PubMed]