Trichinosis is a parasitic zoonosis caused by nematodes of the genus Trichinella (most commonly T. spiralis), acquired through ingestion of raw or undercooked meat containing encysted larvae. [1-2] The disease progresses through an enteral phase (GI symptoms from intestinal invasion) followed by a parenteral phase (systemic symptoms from larval migration into striated muscle and other tissues). [2-3]
1. History
- Key exposure question: Recent consumption of raw or undercooked pork, wild boar, bear, deer, walrus, or ground beef — ask about timing (typically 1–4 weeks prior to symptom onset) [1][4]
- Symptom characterization: Biphasic illness — early GI symptoms (nausea, diarrhea, abdominal pain) within 1–7 days of ingestion, followed by systemic symptoms (fever, myalgias, periorbital edema) at 2–6 weeks [3][5]
- Severity clues: Degree of myalgia, difficulty with movement, dysphagia, dyspnea (diaphragm involvement) [6-7]
- Important negatives: No travel to endemic area, no shared meal exposure, no history of consuming uninspected meat
2. Alarm Features
- Myocarditis: Chest pain, dyspnea, tachycardia, arrhythmias — leading cause of death [4-5]
- Neurotrichinosis: Encephalopathy, seizures, focal neurologic deficits (hemiparesis, ataxia) — mortality up to 5% with CNS involvement [3]
- Pneumonitis: Cough, dyspnea, pulmonary infiltrates [4][7]
- Thromboembolic disease [5]
- Rapidly falling eosinophil count — paradoxically associated with poor prognosis [3]
- Splinter hemorrhages and conjunctival/subconjunctival hemorrhages [4][8]
3. Medications
- Anthelmintics (for systemic disease):
- Albendazole (preferred): 800 mg/day (15 mg/kg/day) in two divided doses for 10–15 days; take with fatty meals to improve absorption [5][9]
- Mebendazole (alternative): 200–400 mg TID for 3 days, then 400–500 mg TID for 10 days; or 5 mg/kg/day (up to 20–25 mg/kg/day) for 10–15 days [5][7]
- Corticosteroids (for severe symptoms): Prednisolone 30–60 mg/day for 10–15 days, particularly for myocarditis, CNS involvement, or severe systemic inflammation [1][5]
- Contraindications: Albendazole and mebendazole are contraindicated in pregnancy and not recommended in children <2 years [5]
- Mild disease with clinical suspicion alone may not require antiparasitic treatment [1]
- Pearl: Treatment is most effective during the enteral (intestinal) phase; efficacy decreases once larvae have encysted in muscle [3]
4. Diet
- Administer albendazole with fatty meals to significantly improve bioavailability [9]
- Prevention: Ensure all pork, wild game, and ground meat is cooked to an internal temperature of ≥71°C (160°F); freezing may kill some but not all Trichinella species (arctic species are freeze-resistant)
- No specific acute dietary restrictions beyond supportive hydration during the febrile/GI phase
5. Review of Systems
- MSK: Myalgias (63% of cases), arthralgia, difficulty with movement, muscle weakness [8][10]
- HEENT: Periorbital/facial edema (59%), conjunctival hyperemia, ocular hemorrhages [8][10]
- GI: Diarrhea, abdominal pain, nausea, vomiting (early phase) [4-5]
- Constitutional: Fever (61%), chills, fatigue, headache, malaise [5][10]
- Skin: Urticarial rash, splinter hemorrhages [4][8]
- Pulmonary: Cough, dyspnea [7]
- Cardiac: Chest pain, palpitations [5]
- Neuro: Confusion, focal deficits, headache [3]
6. Collateral History and Family History
- Critical: Identify a common-source exposure — others who shared the same meal; outbreak investigation is key to diagnosis [8-9]
- Ask about the source of the meat: home-slaughtered, uninspected, wild game, backyard-raised pigs
- Family history is not directly relevant (non-hereditary), but household members who shared the meal need evaluation
- Contact the CDC Parasitic Diseases Hotline when an outbreak is suspected [1]
7. Risk Factors
- Consumption of raw or undercooked pork, wild boar, bear, deer, horse, or walrus meat [1][4]
- Home-slaughtered or uninspected meat — particularly backyard-raised pigs fed scraps/offal [8]
- Hunters consuming wild game without adequate cooking
- Military personnel (highest pooled prevalence at 41.5% in exposed populations) [10]
- Geographic risk: Higher prevalence in Asia (Thailand), Europe (Germany, Türkiye, Eastern Europe), and Oceania [10]
- Regions with inadequate meat inspection programs [2]
8. Differential Diagnosis
- Dermatomyositis/polymyositis — myalgias + elevated CPK, but no eosinophilia or exposure history
- Polyarteritis nodosa — fever, myalgias, eosinophilia; distinguish by angiography/biopsy
- Eosinophilic fasciitis
- Other tissue-invasive helminths: Toxocariasis (visceral larva migrans), muscular sarcocystosis, cysticercosis [4]
- Acute viral myositis (influenza, Coxsackie)
- Drug reaction with eosinophilia (DRESS)
- Hypereosinophilic syndrome
- Angioedema (if periorbital edema is the dominant feature)
- Bacterial endocarditis (splinter hemorrhages, fever)
- Pearl: Patients are often initially misdiagnosed and treated with antibiotics without improvement [8]
9. Past Medical History
- Prior episodes of trichinosis (rare but possible with re-exposure)
- Immunocompromised state — may alter presentation and severity
- Pre-existing cardiac or neurologic disease — increases risk of complications from myocarditis or neurotrichinosis
- Chronic liver disease — may affect anthelmintic metabolism
10. Physical Exam
- Vital signs: Fever (often high-grade), tachycardia
- HEENT: Periorbital/facial edema (hallmark finding), conjunctival injection, subconjunctival hemorrhages [4][8]
- Skin: Maculopapular or urticarial rash, splinter hemorrhages of nails [4]
- MSK: Diffuse muscle tenderness (especially extraocular muscles, masseters, diaphragm, limb flexors), difficulty with movement [6][8]
- Cardiopulmonary: Signs of myocarditis (gallop, murmur, friction rub), crackles if pneumonitis
- Neuro: Altered mental status, focal deficits if neurotrichinosis [3]
11. Lab Studies
- CBC with differential: Marked eosinophilia (present in ~97% of cases), leukocytosis (71%) [8]
- CPK/CK: Elevated in ~82–85% — reflects muscle invasion [6][8]
- LDH, aldolase, AST/ALT: Often elevated [1][7]
- ESR: Elevated in ~98% [6]
- Serology: Anti-Trichinella IgG by ELISA (sensitivity ~94%, specificity ~94%) — but often negative in the first 3 weeks of illness; requires paired sera drawn weeks apart [1][11]
- Hypergammaglobulinemia may be present [1]
- Troponin, BNP if myocarditis suspected
- Pearl: The IDSA recommends serology (EIA) through the CDC or a reference laboratory as the main diagnostic test [12]
12. Imaging
- Chest X-ray: Patchy pulmonary infiltrates, fuzzy lung markings, hilar enlargement if pulmonary involvement [7]
- Brain MRI: Multifocal white matter and cortical lesions if neurotrichinosis suspected — superior to CT [3]
- Brain CT: Multifocal hypodensities in cortex and white matter [3]
- Echocardiogram: If myocarditis suspected
- Imaging is generally unnecessary in mild, uncomplicated cases
13. Special Tests
- Muscle biopsy (preferably deltoid): Definitive diagnosis — demonstrates encysted larvae in striated muscle [7][12]
- Serology (EIA/ELISA): Through CDC or reference lab; two specimens drawn several weeks apart recommended [1][12]
- CDC Parasitic Diseases Hotline consultation recommended when disease is suspected [1]
- No validated clinical scoring system specific to trichinosis; diagnosis relies on the clinical triad of periorbital edema + myalgia + eosinophilia in the setting of appropriate exposure history [5]
14. ECG
- Indications: Obtain ECG in all moderate-to-severe cases to evaluate for myocarditis
- Findings: Sinus tachycardia, ST-T wave changes, conduction abnormalities, arrhythmias
- Myocarditis is a leading cause of death in severe trichinosis [5]
15. Assessment
Classic triad: Fever + periorbital edema + myalgia with eosinophilia, in the context of raw/undercooked meat consumption. [5][10] The most frequently reported symptoms in a global meta-analysis were myalgia (63%), fever (61%), and facial edema (59%). [10]
- Mild disease: GI symptoms only, self-limited
- Moderate disease: Systemic symptoms (fever, myalgia, edema) without organ complications
- Severe disease: Myocarditis, neurotrichinosis, pneumonitis, thromboembolic events — can be fatal [4-5]
- Chronic sequelae: Fatigue and reduced muscle strength may persist for years; 6 months post-treatment, 52% of patients in one cohort still reported myalgias and fatigue [2][13]
16. Treatment Plan
Initial stabilization (ED):
- IV fluids, antipyretics, analgesics
- Obtain CBC with differential, CMP, CPK, LDH, ESR, troponin, ECG
Anthelmintic therapy (for systemic involvement):
- Albendazole 400 mg PO BID with fatty meals × 10–15 days (preferred) [5][9]
- Alternative: Mebendazole 200–400 mg TID × 3 days, then 400–500 mg TID × 10 days [7]
Corticosteroids (for severe disease):
- Prednisolone 30–60 mg/day × 10–15 days, tapered as symptoms improve [1][5]
- Indicated for myocarditis, neurotrichinosis, severe systemic inflammation
Supportive care:
- NSAIDs or acetaminophen for myalgias and fever
- Cardiac monitoring if myocarditis suspected
17. Disposition
- Admit: Severe myalgias with inability to ambulate, myocarditis, neurotrichinosis, pneumonitis, high fever with hemodynamic instability, dysphagia/dyspnea [3][5]
- Observation: Moderate symptoms with significant eosinophilia and elevated CPK pending workup
- Discharge: Mild GI symptoms only, stable vitals, able to tolerate PO, reliable follow-up
- Consult infectious disease for all confirmed or strongly suspected cases
- Notify public health — trichinosis is a reportable disease; outbreak investigation may be warranted [8]
18. Follow Up / Return Precautions
- Follow-up: Infectious disease within 1–2 weeks; repeat serology in 2–4 weeks if initial testing negative (seroconversion may take 3+ weeks) [1]
- Return immediately for: Chest pain, dyspnea, confusion, seizures, worsening weakness, new facial swelling, inability to swallow
- Expected course: Symptoms typically improve within 2–3 weeks of treatment; chronic myalgias and fatigue may persist for months [2][13]
- Counsel: All remaining suspect meat should be discarded; educate on proper cooking temperatures for pork and wild game
- Monitor: Repeat CPK and eosinophil count to track treatment response
References
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