Trichinosis
Trichinosis, also known as trichinellosis, is a parasitic disease caused by nematodes from the Trichinella genus, primarily T. spiralis. This disease is acquired through the consumption of undercooked or contaminated meat, particularly pork and bear meat, which can harbor encysted larvae. Once ingested, the larvae mature in the intestines, reproduce, and then migrate to muscle tissues, leading to a range of symptoms such as nausea, vomiting, diarrhea, fever, swelling in the face and hands, muscle pain, and respiratory issues. The onset of symptoms typically occurs within 72 hours post-infection and can last up to two weeks.
Trichinosis is diagnosed through blood tests that identify specific antibodies or changes in eosinophil counts, and definitive diagnosis may require muscle biopsies. Treatment usually involves antihelminthic medications like mebendazole, often combined with corticosteroids to manage inflammatory responses. Although cases have declined in developed regions due to food safety measures, outbreaks still happen in parts of Latin America and Asia. Prevention focuses on educating the public about safe cooking practices and controlling the feeding and processing of meat products to eliminate potential sources of infection. Understanding these measures is essential, especially for communities that traditionally consume raw or undercooked meats.
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Trichinosis
ALSO KNOWN AS: Trichinellosis
ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, intestines, muscles, musculoskeletal system
DEFINITION: A parasitic disease of humans caused by nematodes of the Trichinella genus and acquired by eating contaminated, undercooked meat
CAUSES: Parasitic infection transmitted through ingestion
SYMPTOMS: Nausea, vomiting, diarrhea or dysentery, fever, sweating, swelling in face and hands, muscle inflammation and pain, coughing, hoarseness
DURATION: Chronic
TREATMENTS: Antihelminthic agents (e.g., mebendazole), corticosteroids
Causes and Symptoms
Trichinosis is a zoonosis (disease acquired from animals) caused by nematodes (roundworms) belonging to the Trichinella genus, most commonly T. spiralis. Trichinella are parasites of carnivores that show little host specificity, infecting pigs, bears, horses, and humans among other mammals. Undercooked, contaminated pork and bear meat are the most significant sources of human infection. While food processing requirements in developed parts of the world have resulted in decreases in trichinosis, other areas, particularly Latin America (Argentina, Mexico, Chile) and Thailand, continue to experience outbreaks of this disease.
The are ingested as larvae that are encysted in the muscle of the infected animal. Once ingested, the larvae hatch from the cysts and mature as adults in the upper intestine. There, the worms mate. Gravid female worms penetrate the intestinal and deposit larvae that migrate in the bloodstream, eventually becoming encapsulated in the muscle of the infected individual.
Ingesting large numbers of larvae results in symptoms such as nausea, vomiting, or dysentery, fever, and sweating that begin seventy-two hours after infection and may last two weeks. As the larvae migrate, (swelling) may be observed around the eyes, side of the nose, temples, and hands. Encysted larvae often result in muscle and pain, and respiratory symptoms such as cough and hoarseness may be observed late in the infection.
Diagnosis is difficult because of the number of body systems affected and the variety of symptoms. Changes in blood, including an increase in the number of eosinophils (eosinophilia), can be monitored. Because the nematodes are highly antigenic, the human is strong, and antibodies in the blood indicate infection. Sensitive tests involving fluorescently labeled antibodies and enzyme-linked immunosorbent assay (ELISA) can be used to detect circulating antigens in blood serum. Definitive diagnosis is made by examining muscle biopsies for the presence of encysted larvae.
Treatment and Therapy
Trichinosis is usually treated using antihelminthic compounds. Early in the infection, mebendazole (Vermox) may be used. Treatment with these compounds is often accompanied by the administration of corticosteroids to prevent reactions. The effectiveness of treatment depends on a variety of factors, including the stage of infection, the nature of the infected individual’s immune response, the species of nematode, and the initial number of larvae ingested.
Control of the disease is primarily through control of feeding and processing of meat food products, especially pork. In Europe, feeding garbage to pigs has been banned, and in the United States, any garbage-fed pigs and hogs must be pretreated. Inspectors examine animals at slaughter, and in the United States freezing, heating, or freeze-drying of meat products is required during processing. Educating the public to cook pork thoroughly to a temperature of 71 degrees Celsius (161 degrees Fahrenheit) is an important focus of control and prevention efforts. Communities that consume game such as bear or Arctic populations that consume raw meat are prone to infection.
Bibliography
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Moorhead, A., et al. “Trichinellosis in the United States, 1991–1996: Declining but Not Gone.” American Journal of Tropical Medicine and Hygiene 60 (1999): 66–69.
Oksanen, Antti, et al. "Epidemiology of Trichinella in the Arctic and Subarctic: A Review." Food and Waterborne Parasitology 28 (2022), doi.org/10.1016/j.fawpar.2022.e00167. Accessed 8 Apr. 2024.
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