Trichinosis

Trichinosis is a parasitic disease that afflicts domestic and wild mammals. Humans acquire it by accident when they eat raw or insufficiently cooked meat and meat products from infected animals.

The causative agents for this disease are various species of the genus Trichinella which, in the larval stage, form cysts in the muscle fibres of susceptible mammals, mostly in the striated muscles which are more active and therefore concentrate more oxygen (diaphragm, masseter, intercostal, tongue muscles, eye muscles, etc.). Trichinella spiralis and Trichinella britovi are the species present in the Iberian Peninsula.

Encapsulated larvae may survive for years in the muscle tissue of the host. As time goes by, the fibrous capsule thickens and the cyst starts to calcify. From an epidemiological point of view, the fact that they resist putrefaction is very important: infective live larvae have frequently been recovered during at least 4 months in meats in a state of advanced decomposition. The cysts also resist curing, salting and smoking.

The main sources of infection for humans are doubtless meat and meat products from infected wild or domestic pigs. Eating horse meat has caused serious outbreaks in European countries and in the United States.

Clinical signs in humans are variable and depend on the individual’s sensitivity, the state of his immune system and the amount of larvae ingested. The first symptoms appear between 4 and 10 days after eating infected meat and consist in diarrhoea, generalized rheumatic symptoms, retinal haemorrhage which aggravates prognosis, edema of the eyelids, pronounced eosinophilia and muscle stiffness affecting mainly flexor muscles which appear swollen, hard and sensitive to the touch.
When the diaphragm and intercostal muscles are affected there is difficulty breathing, asthma attacks and shortness of breath that may produce death. When the muscles in the tongue and pharynx are affected the symptoms are hoarseness, a nasal voice and difficulties swallowing.