Trichinosis
Trichinosis: Excerpt from The 5-Minute Pediatric Consult
Jennifer R. Reid, MDGeorge Anthony Woodward, MD, MBA
Trichinosis - BASICS
Trichinosis - description
- Infection caused by the ingestion of undercooked meat containing nematode larval cysts of the Trichinella genus
- Additional names: Trichinosis, Trichinelliasis, Trichinellosis
Trichinosis - general prevention
- Eat only fully cooked meat, especially pork and wild game (bear, walrus, cougar)
- Meat should reach >160°F internally, no pink:
- Freezing kills T. spiralis in pork (<6 in thick) at –20°F for 6 days, –10°F for 10 days, and –5°F for 20 days.
- Freezing may not kill other Trichinella species, particularly in wild game.
- Smoking, salting, and drying meat (including jerky) are not reliable sterilization methods.
- Separate and routinely clean pork and game meat-grinding equipment.
- Irradiation may not kill Trichinella, but should prevent ability to replicate.
- Avoid feeding swine uncooked meat scraps.
- Actively control rodents.
- Avoid breast feeding if patient infected.
Trichinosis - epidemiology
- Worldwide distribution, disease concentrated in Europe and North America: 8 Trichinella species (T. spiralis, T. brivoti, T. pseudosprilais, T. papuae, T. nativa, T. nelsoni, T. murrelli, and T. zimbawensis)
- Historically, majority of US infections are due to T. spiralis in commercial pork.
- In 1997–2001, majority of US infections were associated with wild game.
- Infections sporadic and in epidemics (e.g., families and communities with common exposure)
- Consider in patients who have had recent foreign travel, consumed foreign meat or wild game (e.g., bear, cougar, hyena, lion, panther, fox), horse, dog (China), seal, or walrus meat
- Carried by rodents, domesticated animals (e.g., dogs, cats), raccoons, opossums, and skunks
- Disease not transmissible person to person
Trichinosis - incidence
Between 1997 and 2001 in the US, median of 12 cases annually, 9 outbreaks involving 33 cases, and no deaths:
- Decreasing number of cases attributed to decline in prevalence of Trichinella in commercial swine (1.41% in 1900, 0.125% in 1966, and 0.013% in 1995), federal regulation preventing uncooked meat consumption by commercial swine, increased public awareness regarding properly frozen and cooked meat
Trichinosis - prevalence
~4% of cadavers in 1970 study with evidence of previous infection (additional estimates range from 10–20% prevalence)
Trichinosis - risk factors
- Consumption of inadequately cooked meat
- Trichinella species consumed
- Immune status of host
Trichinosis - pathophysiology
- Trichinella are obligate intracellular parasites
- Larvae in undercooked meat eaten by patient
- Larvae are released after cyst wall digestion by gastric enzymes; pass to small intestine; invade mucosa with edema, hyperemia, and ulcerations; then develop into adult worms.
- Fertilized females release larvae (~500) over 2–3 weeks. Adult worms are expelled in feces; they do not multiply in human host.
- Newborn larvae travel the bloodstream to seed skeletal muscles. There they grow 10-fold, coil, and encyst. Muscle fibers enlarge and become edematous; may have granulomatous reactions in nonskeletal muscle, but larvae are found only in skeletal muscle.
- Cysts (hyaline capsules) may calcify over several months to years.
Trichinosis - etiology
Consumption of undercooked infected meat; see “Description”
Trichinosis - associated conditions
Immunocompromised hosts at risk for more serious or prolonged infection
Trichinosis - DIAGNOSIS
Trichinosis - signs & symptoms
- Severity of symptoms depend on Trichinella species and size of inoculum.
- Children often have fewer and milder symptoms than adults have.
- Most infections asymptomatic (subclinical)
- Enteral phase (1st week after infection): Symptoms attributable to adult worms in the intestines and mucosal invasion
- Diarrhea, abdominal pain, nausea, vomiting, anorexia
- May persist for weeks
- Parenteral phase (1–8 weeks after infection): Symptoms attributable to systemic invasion:
- Fever (begins at 2 weeks, peaks after 4 weeks, may reach 40–41°C), malaise
- Ocular: Periorbital edema, subconjunctival hemorrhage, conjunctivitis, disturbed vision, ocular pain, chemosis
- Muscular: Myalgias, myositis (usually in extraocular muscles, then masseters, tongue, neck, limb flexors, lumbar muscles, intercostals, and diaphragm) with dyspnea, cough, hoarseness
- Neurologic: Headache, focal paralysis, delirium, psychosis
- Cardiac: Myocarditis, arrhythmias secondary to myocarditis
- Parenteral phase symptoms typically peak 2–3 weeks after infection
- Malaise and weakness may persist for weeks.
- Convalescent phase (may persist for months to years): Myalgias, weakness
- Death can occur due to myocarditis, encephalitis, or pneumonia
- Many signs and symptoms (i.e., periorbital edema, muscle edema, eosinophilia due to allergic reaction to parasite antigens)
- Nonspecific signs and symptoms may mimic those of other illnesses.
Trichinosis - history
- Ingestion of inadequately cooked meat (commercial pork, noncommercial pork, game animals, foreign meat)
- Others with same dietary exposure with similar symptoms
Trichinosis - physical exam
Fever, periorbital edema, muscular tenderness, generalized edema, urticaria: See: “Signs and Symptoms.”
Trichinosis - tests
Trichinosis - lab
- Specific tests:
- Detection of Trichinella-specific DNA by polymerase chain reaction (availability limited)
- Trichinella serology (through US Centers for Disease Control and Prevention or state labs):
- 2 tests required to ensure accurate diagnosis: 1st to detect antigen and the 2nd to detect antibodies that react to parasite surface antigens
- Bentonite flocculation (1:5 or 4-fold increase), latex flocculation test, ELISA, or immunofluorescence
- Skeletal muscle biopsy (i.e., deltoid muscle from patient at least 17 days after infection; can test suspected meat if available). Usually not necessary:
- Result can be negative in infected patient due to sampling error
- Inflammatory cells surround encysted larvae in necrotic muscle fibers.
- Granulomatous reaction present in nonskeletal muscle but not encysted larvae
- Nonspecific tests:
- CBC and differential: Eosinophilia (to 70%; peaks 10–21 days postinfection), leukocytosis (up to 24,000/μL)
- Elevated serum creatine phosphokinase (up to 17,000 U/L) alanine aminotransferase, aspartate transaminase, total IgE
Trichinosis - imaging
- Cardiac: Myocarditis may show EKG changes (premature contractions, prolonged PR interval, small QRS with intraventricular block, and flattening or inversion of T waves)
- Neurologic: Small CNS lesions, ring calcifications; intravenous enhancement on CT scan
- Electromyography: Results resemble those of polymyositis and inflammatory myopathies.
Trichinosis - diag proced-surgery
See “Lab tests.”
Trichinosis - pathological findings
See “Lab tests.”
Trichinosis - differencial diagnosis
- Infection: Viral syndromes, parasitic, spirochete, gastroenteritis, influenza, sinusitis, typhoid fever, measles, scarlet fever, meningitis, rheumatic fever, encephalitis, encephalomyelitis, poliomyelitis, tetanus, schistosomiasis, hookworm, Strongyloides, or helminthic infection
- Miscellaneous: Fever of unknown origin, dermatomyositis, myocarditis, inflammatory bowel disease, angioneurotic edema, rheumatoid arthritis, glomerulonephritis, polyneuritis, eosinophilic leukemia, polyarteritis nodosa, nonabsorption syndromes
Trichinosis - TREATMENT
Trichinosis - general measures
- Most patients recover without specific therapy.
- Symptomatic treatment: Acetaminophen, salicylates, bed rest
Trichinosis - diet
Avoid further exposures.
Trichinosis - medication
Trichinosis - first line
- Mebendazole (Vermox): Variable dosing recommendations: 200–400 mg t.i.d. for 3 days, followed by 400–500 mg t.i.d. for 11 days (14-day course)
- Thiabendazole (Mintezol):
- 25 mg/kg PO b.i.d. for 10 days
- Better absorbed than mebendazole, but increased side effects
- Albendazole (Albenza):
- 15 mg/kg/d divided b.i.d. for 15 days
- Max dose 800 mg/d
- Not approved for <2 years, but used
- Mebendazole, thiabendazole, and albendazole are most efficacious during the enteral phase (active against intestinal worms, little effect on muscle-embedded larvae)
- Pyrantel pamoate (Antiminth):
- 10 mg/kg/d for 4 days
- Max dose 1 g/d
- Not approved for <2 years
- Effective only against adult worms, not encysted larvae
Trichinosis - second line
Systemic corticosteroids:
- Symptomatic relief of inflammatory reaction and help if CNS or cardiac involvement
- Not recommended as monotherapy, may prolong adult worm survival in intestines
Trichinosis - surgery
Muscle biopsy for diagnosis, see “Tests.”
Trichinosis - FOLLOW UP
Expect improvement over several weeks
Trichinosis - disposition
Trichinosis - admission criteria
Cardiac, neurologic, or pulmonary complications indicate more severe disease.
Trichinosis - discharge criteria
Resolution of cardiac symptoms
Trichinosis - issues for referral
Cardiac, neurologic, pulmonary complications
Trichinosis - prognosis
- Mild to moderate illness usually resolves spontaneously with minimal sequelae. Muscle swelling and weakness may persist.
- Poorer prognosis (can be fulminant and fatal) with cardiac, CNS, or pulmonary involvement
- Children are usually less symptomatic, have fewer complications, and recover more quickly.
Trichinosis - complications
- Cardiac: Myocarditis (may result in death 4–8 weeks after infection), secondary arrhythmias, hypotension, pericardial effusion
- Neurologic: Meningoencephalitis, CNS granulomas, headaches
- Pulmonary: Pneumonia, pneumonitis, pleural effusion, pulmonary embolism or infarct
- Renal: Glomerulonephritis
- Hepatic: Fatty change
- Muscular: Prolonged myalgias
- Ocular: Retinal hemorrhages
- Complications rarely permanent
Trichinosis - patient monitoring
Cardiopulmonary monitoring
Trichinosis - bibliography
American Academy of Pediatrics. Trichinosis (Trichinella spiralis). In: Pickering LK, ed. 2006 Red Book: Report of the Committee of Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006;671–673.- Bruschi F, Murrell KD. New aspects of human trichinellosis: The impact of new Trichinella species. Postgrad Med J. 2002;78:15–22.
- Centers for Disease Control and Prevention. Trichinellosis associated with bear meat—New York and Tennessee, 2003. MMWR Morb Mortal Wkly Rep. 2004;53(27):606–610.
- Centers for Disease Control and Prevention. Trichinellosis surveillance—United States, MMWR 1997–2001. 2003;52(SS06):1–8.
Grove DI. Trichinosis. In: Mandell GL, ed. Principles and Practice of Infectious Disease. 6th ed. Philadelphia, PA: Elsevier; 2005: 3268–3269.- Ozdemir D, Ozkan H, Akkoc N, et al. Acute Trichinellosis in children compared with adults. Pediatr Infect Dis J. 2005;24:897–900.
- Shellenberg RS, Tan BJ, Irvine JD, et al. An outbreak of Trichinellosis due to consumption of bear meat infected with Trichinella nativa, in 2 northern Saskatchewan communities. J Infect Dis. 2003;188:835–843.
Trichinosis - CODES
Trichinosis - icd9
124 Trichinosis
Trichinosis - PATIENT TEACHING-MED
If concern for Trichinosis exposure or symptoms, seek medical care early. Treatment most efficacious the 1st week after exposure.
Trichinosis - prevent
- Thoroughly cook all meat, internal temperature should reach >160°F.
- Freezing, drying, or curing may not kill all Trichinella species.
Trichinosis - FAQ
- Q: How can I prevent infection?
- A: Be sure meat is fully cooked (internal temperature ≥160°F [71°C], not pink) or frozen (–20°F for 6 days, –10°F for 10 days, or –5°F for 20 days). Trichinella larvae in game may be relatively resistant to freezing. Frozen bear meat has yielded infective larvae after >2 years of freezing.
- Q: Is trichinosis contagious from person to person?
- A: No, except through infected breast milk.
- Q: Do special precautions need to be taken when treating a patient with presumed trichinosis?
- A: Only thorough hand washing. No isolation required.
- Q: What should we recommend for a patient who has eaten contaminated meat?
- A: Treatment with mebendazole or thiabendazole should be considered.
- Q: What are the classic hallmarks of trichinosis?
- A: Diarrhea, abdominal pain, periorbital edema, myositis, fever, and eosinophilia, especially when combined with history of ingestion of potentially poorly cooked meat.
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Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
More About Trichinosis
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Medical Books Excerpts
- Trichinosis
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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