2024-03-21 09:33:58
Despite the drop in the number of cases of trichinellosis observed in France, this parasitosis nonetheless remains a public health problem, in particular because of its potential seriousness and the epidemic risk.
Agent
Trichinae are parasites that belong to the class of nematodes (roundworms). Twelve species are listed, eight of which have already been isolated from humans. However, infections encountered in humans in France are linked to Trichinella spiralis, T. pseudospiralis or T. britovi.
Adults are small worms (1.5 mm for the male, 2 to 3 mm for the female). Lemon-shaped larvae (400 µm long) encysted in muscle fibers are just under 1 mm long and spirally coiled. The development cycle of trichinae never takes place outside of their host (monoxene cycle). The larvae, ingested in the form of cysts, become adults in 24 to 36 hours in the epithelium of the mucosa of the small intestine; after fertilization, female adults give birth to new larvae (on average 1,500 larvae per female) between days D4 and D10 after infestation. These larvae then take the blood circulation or the lymphatic route and migrate towards the striated skeletal muscles; they penetrate the muscle cells in which they encyst within 3 weeks; they can remain there for several years, and the cysts can even calcify.
Reservoir
Trichinae are likely to infest almost all carnivorous and omnivorous mammals, including certain marine mammals, and at all latitudes. They are found in particular in horses, wild boars, pigs… but also lynx, foxes, bears, badgers, polecats, birds, dogs, cats, rats… and humans. In animals, their presence is generally asymptomatic. Carnivorous or scavenger birds as well as certain reptiles can also be infested.
Mode de contamination
Transmission of the parasite to humans is linked to the ingestion of lightly or uncooked contaminated meat; in Europe, it is mainly wild boar, pork and horse meat.
Epidemiology
The main source of human contamination worldwide is pork. The distribution between countries is very contrasting depending on the species likely to be affected by the disease.
In France, current regulations require systematic monitoring of risky meats: pigs, wild boar, horses. This check consists of an analysis of a muscle sample taken at the slaughterhouse.
The cases identified in France result from the ingestion of uncontrolled wild boar meat or game meat illegally imported into France.
The emergence in the 1980s and 1990s of epidemics of several hundred cases linked to the consumption of horse meat led to the strengthening of veterinary control measures, particularly on horse carcasses. These measures have been effective, as no cases linked to horse meat have been observed since 1998.
Clinic in men
Incubation : 48 hours often silent, sometimes digestive syndrome with abdominal pain, diarrhea, if massive infestation.
From D+2 to D+15 to +30: fever, abdominal pain, diarrhea, nausea, vomiting.
From D+15: Plateau fever, deterioration of general condition, muscle damage with sometimes intense myalgia and reduction in muscle tone, facial edema, very characteristic of the disease and possibly allergic-type manifestations.
During the chronic phase, the fever decreases, but fatigue, muscular and allergic manifestations persist. Cardiac (myocarditis) and neurological complications: local deficit signs (hemiparesis, central sensory deficit) or encephalopathy may occur. Neurological or muscular after-effects may be observed.
The severity of the disease depends on the quantity of larvae ingested and the species involved. Early treatment reduces complications. In humans, there are healthy carriers (who have less than a few dozen larvae).
Note: no characteristic clinical symptoms are observed in the infested animal.
Diagnostic
The diagnosis is based on a set of clinical, biological and epidemiological arguments. The questioning must look for consumption of raw or lightly cooked wild boar or horse meat, taking into account a very variable incubation time (1 to 3 weeks).
– Massive hyper eosinophilia greater than 1000, which increases until D+60.
– Increase from the second week in muscle enzymes: CPK, LDH, myokinase.
– Presence of serum antibodies from D+15, the notion of seroconversion being important.
– Muscle biopsy: positive from 5-6 weeks, but be careful of false negatives if the infestation is not significant.
We can also, when possible, look for encapsulated trichinella larvae in the meat consumed.
Treatment
Treatment is based on anti-parasitic chemotherapy, notably benzimidazoles combined with corticosteroid therapy.
Prevention
Transmission occurs through contaminated raw or undercooked meat, particularly horse and wild boar meat.
At an individual level, sufficient cooking of meat (71°C, gray meat through) is the ideal prevention method.. Freezing meat is not sufficient to eliminate any risk of transmission of trichinellosis. As for cold meats, only cooked products destroy trichinella; salting and smoking are not sanitizing techniques.
At the collective level, prevention is based on systematic health control of meat. In France, veterinary surveillance by artificial chlorhydro-pepsic digestion concerns horse meat and free-range pork (survey for industrial pork).
For the wild game market, controls are mandatory if the hunter transfers to a third party the game he has hunted himself, whether in a commercial context or not, with the exception of a direct transfer from the hunter to the consumer. In the latter case, it is strongly recommended that consumers ask the hunter for a certificate relating to the search for trichinae. As far as the hunter is concerned, his personal liability would be engaged if the consumption of the meat provided resulted in damage to the consumer; it is therefore very strongly recommended that this research be carried out.
Statement
Human trichinellosis as a collective foodborne illness (TIAC) is a notifiable disease.
Any TIAC must be declared to the departmental health authority (ARS or DDCSPP). This declaration is obligatory: “on the one hand for any medical doctor who has noted its existence, on the other hand, for the main occupant, head of family or establishment, of the premises where the patients are located.”
The mandatory declaration data comes from 2 different sources:
– the number of TIAC outbreaks declared to the Regional Health Agencies (ARS) is transmitted to the Health Monitoring Institute as well as, where applicable, the investigation report of the TIAC outbreak.
– declarations from TIAC outbreaks to the Departmental Directorates of Veterinary Services are subject to immediate notification by fax to the General Directorate of Food and subsequently the sending of an investigation report.
The synthesis and analysis of the data are carried out by InVS after pooling information from these two sources and eliminating double declarations.
Download the declaration form
To know more
– Health monitoring institute:
Weekly epidemiological bulletins n°29/1994 – July 26, 1994; n°44/1995 – October 31, 1995; n°49, 1997 – December 2, 1997; n°28, 1998 – July 14, 1998; n°15/2001 – April 10, 2001 (TIAC).
– National Agency for Food, Environmental and Occupational Health Safety (ANSES):
Trichinellosis file
1711108896
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