Trichinellosis/Trichinosis Clinical Presentation

Updated: Apr 18, 2018
  • Author: L Kristian Arnold, MD, MPH; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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The usual incubation period of trichinellosis is 8-15 days. Following intestinal incubation, initial symptoms most commonly are gastrointestinal due to the invasion of the intestinal wall by the juvenile larvae. [57] Diagnosis depends heavily upon a suspicion and obtaining the history of ingesting potentially infected meat that was not cooked enough to kill the larvae. With increasing global migration, global exotic food transport and exotic tourism, the emergency physician should be aware of this diagnosis and include appropriate travel and dietary questions in the history of patients with gastroenteritis or unexplained myalgias.

Consider the following:

  • Myalgia (75%) - Classically reported as most common in masseter, diaphragm, and intercostal muscles, though high percent reported in extremities and neck/shoulder girdle in one cohort from a large outbreak in Turkey [58] ; may be severe to point of inability to ambulate or perform simple upper extremity or truncal tasks like feeding or sitting upright

  • Fever (60-75%) - 38.5-40.5°C

  • Weakness (75%)

  • Diarrhea (40-60%) - Usually only in the acute intestinal proliferative and penetration phases of nematode infestation

  • Facial edema (40-64%) - Usually considered one of the hallmark features, particularly when localized to the eyelids

  • Headache (50-60%)

  • Fatigue/malaise (up to 95%)

  • Arthralgia

  • Cardioneurologic syndrome - Onset of these symptoms has usually been reported to occur early following onset of general symptoms and prior to muscle invasion. [59, 12] The syndrome includes varying combinations of the following:

    • Encephalopathy

    • Focal neurologic deficits

    • Acute myocardial injury (eg, myocarditis, sinus and atrial nodal dysfunction, congestive heart failure, infarction)

    • Hypereosinophilia (≥4000 granulocytes/mm3)

  • Rash - This may occur in several forms, as follows:

    • Urticaria (most common)

    • Petechiae

    • Splinter hemorrhages

    • Palmar rash - Peripheral palmar and volar digital edema and erythema; desquamation occurs (10% in one study [60] )



Physical examination findings may include the following:

  • Fever (71%)

  • Palpebral edema (50-60%) - Usually considered one of the hallmark findings; may be associated with chemosis and proptosis. [61]

  • Generalized edema

  • Muscle weakness and tenderness - Usually not true neurologic weakness but pain related

  • Neurologic findings consistent with encephalopathy or focal deficits

  • Cardiac findings of myocarditis, pericarditis, or ischemia



Trichinellosis is a completely preventable infestation. The single most important causative factor is the consumption of inadequately cooked meat. Although most developed countries have some form of trichosis control program, these controls have been documented to fail.

Trichinella species of nematodes: Of the 11 recognized genotypes, the following are the most clinically significant, although others may not yet have been identified:

  • T spiralis is the primary cause associated with domesticated animals.

  • T britovi is seen frequently in wild boar, horses, and free-ranging swine. It has also been reported in bear in Japan where it has been given a separate classification, T9, because of minor genetic variations from the European T britova. [14]

  • T murrelli has been identified in wild and domestic animals other than pigs only in North America. [49]

  • T nelsoni is seen in various large carnivores of sub-Saharan Africa. [24]

  • T nativa has been documented in almost all land and marine mammalian carnivores in the arctic and periarctic regions around the globe. In humans, it has been associated with more prolonged diarrhea and fewer muscle symptoms. It is also more resistant to freezing than other species, having been documented to not be killed by prolonged freezing at -18o C. [49]

  • T9, closely related to T britovi is isolated to Japan, existing in bear, fox, and raccoon dog. [49]

  • T pseudospiralis has been documented in birds and does not form a capsule in the muscle, thus leading to less muscle inflammation and pain. Conversely, the muscle phase seems to remain actively infective for a longer period, probably since, without cyst formation, ultimate calcification does not occur. [62]

  • T papuae in wild pigs has been identified in Papua-New Guinea as a source of infection among forest-dwelling hunters. It is a nonencapsulating form of Trichinella. [53]

  • T zimbabwensis has been identified as infecting reptiles in southern Africa. Particularly concerning for increasing human risk is their presence in farm-raised crocodiles. [63] More recent reports indicate a presence in sylvatic reptiles as well. [64]