Introduction 

Trichinosis, also known as trichinellosis, is a disease caused by a parasitic roundworm of the Trichinella species. Human trichinosis is most commonly caused by Trichinella spiralis, and is contracted by the ingestion of raw or undercooked meat. The most frequent source of human infection is the domestic pig, followed by rodents, horses, wild boars, and bears as common reservoirs. Although anyone can get trichinosis regardless of health status, cases are most commonly seen in North America and Europe, where consumption of a traditional meat- or pork-based diet is common. Approximately 10,000 people contract trichinosis per year, though numbers have fallen with progress in strict food safety regulations.^1,2

Once ingested, Trichinella larvae invade the small intestine, where they’re subject to digestion, and further migrate to striated muscles (known as the encysting phase), leading to a range of serious, sometimes fatal, symptoms. Early signs of infection include diarrhoea and abdominal discomfort, while later stages can lead to muscle pain, swelling, fever, and, in severe cases, neurological and cardiac complications such as encephalitis or myocarditis. Early detection and treatment of trichinosis are essential to reduce discomfort and prevent complications. Treatment options include antiparasitic drugs known as anthelmintics, symptom management and supportive care strategies.^2,3

Diagnosis

The clinical presentation of trichinosis ranges from asymptomatic to severe symptoms depending on the number of larvae present within the host. The first sign of an infection is if an individual presents with three of the following signs:¹

• Fever
• Muscle aches and pains
• Gastrointestinal symptoms 
• Facial swelling
• High levels of eosinophils
• Subconjunctival, subungual, and retinal haemorrhages - which refer to small areas of bleeding in the outer eye, under the nails or in the retina

Laboratory tests are also conducted to confirm Trichinella infection. During disease progression, an increase in eosinophils, a type of white blood cell, can be detected. Elevations in creatine kinases, indicating muscle damage, are also observed. Immunoassays such as ELISA are techniques that allow for the measurement of specific antibodies against Trichinella present in the serum of an animal, more specifically the detection of anti-Trichinella IgG, to confirm infection. Muscle biopsies can also be taken to examine encysted larvae microscopically.^1,4

Treatment

The treatment of trichinosis focuses on eliminating the parasite with antiparasitics, more specifically anthelmintics, reducing the inflammatory burden, and managing associated complications. It is important to note that larvae have greater resistance than adult forms and can survive for years in the muscle tissues of living animals.¹

First-line medications

Albendazole or mebendazole

Both benzimidazole derivatives, albendazole and mebendazole, are anthelmintics given as first-line treatments against trichinosis. Treatment with either of these agents should preferably begin immediately, within 1 week of infection, when the roundworm is still in the gut. This allows the inhibition of the development of newborn larvae and the progression to the encysting phase. It is up to 100% effective in adult forms of Trichinella species, though trichinosis is difficult to diagnose at this stage due to its asymptomatic nature. In most cases, therapy doesn't begin until symptoms including fever, rash, swelling, and severe muscle pain are expressed, indicating larval invasion and encystment. Nevertheless, the drugs still reduce the burden of larval migration and encystment in muscle tissues. ^1,4,5

Albendazole is the primary medication used to treat trichinosis. It is taken orally, twice daily for two weeks, and reaches the required plasma levels without the need for monitoring. If administered early, it prevents muscle invasion and disease development. Mebendazole is taken thrice daily for 13 days, though plasma levels vary between individuals, therefore, monitoring is required. Both medications are generally well-tolerated with minimal side effects, though they are not used in pregnant women or children under 2 years of age.^1,6,7

Pyrantel

Pyrantel is another anthelmintic used to treat parasitic worm infections and is an effective option for pregnant women or younger children. It kills Trichinella species at the intestinal stage by causing paralysis of the roundworm and preventing its migration through the intestinal wall, leading to its removal by normal digestion. It should be noted that pyrantel has little to no effect on newborn or muscle larvae. ^2,6,8

Supportive care - symptom management

Corticosteroids 

In individuals with a larger parasite burden, severe symptoms, including myalgias (muscle pains) are more common. Therefore, in many cases, anthelmintics are given alongside analgesics - pain medications. Glucocorticoids such as prednisone or prednisolone may be co-administered with anthelmintics for 10-14 days with monitoring to prevent severe inflammation. The risk of developing low blood pressure (hypotension) is seen in those with higher parasite numbers following anthelmintic therapy, as an inflammatory response can develop when large numbers of parasites are rapidly killed off. Administration of glucocorticoids can reduce this risk as well. ^4,6 

Future strategies

Medicinal plants 

The spread of anthelmintic resistance and the decreasing activity of medications against the encysting stage of infection led to the exploration of medicinal plants as alternative therapeutic strategies. A study showed that the leaf extract from the plant Lasia spinosa is effective against both adult and migrating stages of Trichinella spiralis infection. However, encysted muscle larvae are still less sensitive. ^6,7

Artemisia species have the ability to kill or inhibit the growth of nematodes in plants and animals. Essential oils from some of these species have shown strong effects against the muscle larvae of Trichinella spiralis infection without toxicity to mammalian cells. Another study also identified decreased adult-worm count in infected animals as well as reduced infection-related symptoms, such as oedema and inflammation, with this therapy.^6,7,8

Myrrh is a sap-like resin from a certain Commiphora tree and may be effective for controlling Trichinella spiralis infection. A study showed reductions in levels of encysted larvae, though more studies are required.^7,8

Prevention strategies

The prevention of trichinosis involves a combination of public health measures, proper food handling as well as awareness and education of risk factors. Some of the ways infection can be prevented are as follows:^1,4

• Cook all wild-game meats thoroughly at a temperature of at least 71-74℃ (160-165℉) to kill encysted larvae
• Maintain proper hygienic practices: wash your hands with soap and water before and after handling raw meat, disinfect all utensils and surfaces used to prepare raw meat
• Long-term freezing of cuts of pork at -15 to -20℃ (5 to -4℉) is effective at killing Trichinella spiralis, though some species of Trichinella are freeze-resistant 

It is important to note that microwave cooking, curing, drying, salting, smoking or short-term freezing do not destroy larvae. 

FAQs

How long can you have trichinosis without knowing? 

Most cases of trichinosis are asymptomatic during the early stages (1-2 weeks), and symptoms can develop gradually as the larvae migrate to the muscles (around 2 weeks). Symptoms may remain mild, and some people may not experience noticeable signs until the larvae have encysted in the muscles. This can occur over a period of months, and the infection can persist for months to years without treatment, depending on the parasite load. If you are concerned about exposure, a blood test can confirm infection and allow for prompt treatment. ^2,3

What are the potential long-term complications of untreated trichinosis?

In most cases, trichinosis-related long-term complications are rare. In people experiencing severe disease with high parasite burden, the larvae can travel to other organs and cause complications. This includes myocarditis, inflammation of the heart muscle, pneumonitis, inflammation of the lungs, and encephalitis, inflammation of the brain.²

Summary 

Trichinosis (trichinellosis) is a disease caused by a parasitic roundworm and is transmitted to humans most commonly by the consumption of raw or undercooked pork. Anyone can get trichinosis, and it presents with a range of symptoms including abdominal discomfort, fever, and muscle pain. Diagnosis of the disease depends on the clinical signs presented by an individual, and infection is confirmed by conducting several laboratory tests. Prompt diagnosis is crucial, allowing the immediate administration of treatments to prevent long-term complications. 

First-line treatments are the anthelmintic medications albendazole and mebendazole, which target the parasitic roundworms directly. These treatments can be given in combination with corticosteroids to reduce inflammation-related symptoms. Medicinal plants are also being considered as future therapeutic strategies. Preventing trichinosis relies on proper food handling practices, awareness of risk factors, and, most importantly, thoroughly cooking wild game meat to eliminate the risk of infection.