Trichinosis / Trichinellosis

Trichinosis is caused by Trichinella spiralis, a parasite found in pigs, rats and bears. Transmission occurs through the consumption of raw or undercooked pork or game meat containing larvae of the organism.

The larvae invade the intestinal mucosa and mature into adult worms. Secondary invasion of striated muscle by fresh larvae produced by the adult worms occurs.

Clinical presentation

• It depends on the number of ingested larvae.
• Light infection may be asymptomatic ( less than ten larvae per gram for muscle)
• Shorter incubation= more severe disease

A heavy infection has two stages;

1. Intestinal- between 2nd and 7th day.

• Abdominal pain, nausea, vomiting and diarrhoea
• May be asymptomatic

2. Muscle stage-

• Freshly produced larvae disseminate hematogenously to skeletal muscle and may remain viable for many years
• Present with muscle pain, tenderness, swelling and weakness. This may limit movement
• High fevers

Physical examination;

• Subungual splinter haemorrhages
• Oedema of the face, eyelids and conjunctiva
• Subconjunctival hemorrhages, conjunctivitis, chemosis, and retinal hemorrhage are the common ocular findings.
• Tenderness and stiffness of muscles
• Invasion of diaphragm- cough, dyspnoea, pain

Serious infection;

• Acute myocariditis
• Encephalitis
• Pneumonia
• Thrombotic complications

Diagnosis; clinical, confirmed by serology

Investigations

1. Complete blood count- eosinophilia
2. Serology- reliable. Confirmed with Western blot. Antibodies are detectable after three or more weeks of infection
3. Muscle biopsy- for definitive diagnosis. Larvae are identified in the gastrocnemius or deltoid muscle
4. PCR- differentiates among the Trichinella species

Differential diagnosis

• Strongyloidiasis
• Visceral larva migrans
• Cysticercosis
• Sarcocystosis
• Dermatomyositis

Management

For most patients, it is self-limited

• Albendazole 400mg bd for 8 to 14 days
• Alt; mebendazole 200 to 400mg TDS for three days, follows by 400 to 500mg TDS for ten days.
• Add corticosteroids in the presence of systemic disease

Prevention

• Education regarding the consumption of pork
• Irradiation of sealed packed meat