Trichinellosis - France

International Society for Infectious Diseases
<http://www.isid.org>

Source: Eurosurveillance weekly release, Vol. 11 Issue 9 [edited]
< http://www.eurosurveillance.org/ew/2006/060914.asp#5>


Human trichinellosis acquired from wild boar meat: a continuing
parasitic risk in France
-----------------------------------------------
Since the beginning of 2006, the French Trichinella National
Reference Centre has been notified of 3 incidents of trichinellosis
due to the consumption of wild boar: one in the Midi-Pyrenees region
(2 cases in the Department of Haute Garonne), and 2 in the
Provence-Alpes-Cote-d'Azur region (outbreaks of 3 and 6 cases, all in
the Department of Var). In comparison with the 20 incidents of
trichinellosis notified or published in France since 1975 (see
Table), this recent series of incidents seen over a period of 6
months shows a significant increase in frequency (P<0.01). These
small scale outbreaks share some common characteristics:

* They all occurred in a group of hunters and their close contacts
(household and friends).
* Game meat was prepared by the hunters themselves (or their close
contacts), and therefore was not on sale to the public, and had not
undergone the usual regulatory hygiene inspection.
* Occurred in people who often ate this kind of game meat, but who
neglected basic cooking rules by eating raw or rare barbecued meats.
* Meat was distributed within a private network, making
identification of the exposed population and recovery of all the
contaminated portions very difficult.
* Several animals were killed during the same hunting trip and cooked
together, which makes the search for contaminated portions very difficult.

Table: Indigenous outbreaks of trichinellosis due to wild boar meat
in France since 1975:
Number of outbreaks Number of cases by Department, (species)
1975-1980 2 4A, 3B
1981-1985 4 5C, 13D , 39E , 3?
1986-1990 2 11F, 4G
1991-1995 6 10F (_T. britovi_) , 4F, 3G, 3H, 4G, 3A
1996-2000 1 4G (_T. pseudospiralis_)
2001-2005 2 6F (_T. britovi_) ,4I
2006 3 3D, 3B (_T.spiralis_) , 6B (_T. britovi_)
Total 20

A: Pyrenees Orientales, B: Var, C: Pyrenees Atlantiques, D: Haute
Garonne, E: Cher F: Alpes Maritimes, G: Bouches du Rhone, H: Herault, I: Aude

This recent increase in notified outbreaks could be due to better
recognition of the disease by health professionals. However,
ignorance of basic cooking rules for high-risk meat of this nature,
and new culinary trends promoting raw meat consumption, are probably
partly responsible for the increase in cases. Furthermore, these
outbreaks have occurred in regions with large wild boar populations
and where hunters are reluctant to subject their game meat to hygiene
inspections.

Cosmopolitan parasites acquired by eating raw meat that contain
larvae of the nematode worm _Trichinella_ can be efficiently
controlled by applying hygiene measures both through public health
and in the home. Human and animal trichinellosis should be considered
as potentially serious epidemic diseases. They are reemerging in
Europe and worldwide [1,2]. The parasite's reservoir is wild animals,
and in France, _Trichinella spiralis_, _T. britovi_ (found more
commonly in mountain regions) and _T. pseudospiralis_, all circulate.
Therefore, game meat that is likely to contain _Trichinella_ needs to
be inspected. _T. spiralis_ had not been seen in France for 20 years
until it was found to have infected several people in March 2006.
They had eaten an infected wild boar found to contain a parasitic
load of over 20 larvae/g of muscle. The other events described (see
Table) are mostly due to T. britovi, but it has not been possible to
type the isolates in all outbreaks. It is difficult to evaluate the
prevalence of the parasite in carnivorous wild animals (foxes or
mustelids) or omnivores (suidae: pigs, wild boars). A study in 1973
found _Trichinella_ larvae in a weasel and a field mouse [3], but
since then, there has only been one large-scale survey, in 1996: of
5473 foxes examined, 54 were found to be positive for _Trichinella_
larvae, and most of these were in mountainous areas in central and
southwest France [4].

The National Reference Laboratory for veterinary parasitology has
carried out annual surveys since 1996 on smaller samples of wild
carnivores (50 to 70), and prevalence has been found to vary between
0.05 percent and one percent.

Serological studies were carried out between 2000 and 2005 on a
sample of 8000 wild boars throughout France, and seroprevalence
between Departments was found to vary from 2 percent and 14 percent
[5]. Around 5000-7000 wild boar hunted or raised for consumption are
officially inspected each year, and _Trichinella_ prevalence of less
than 1/10 000 has been found [5,6,7]. The illness is now fairly well
known, and clusters of patients who present with fever, facial edema,
myalgia, hypereosinophilia and increased muscular enzymes seric
levels are suggestive of trichinellosis, which is confirmed by
serology with western blotting. Early diagnosis allows rapid
prescription of specific treatment (albendazole, 400 mg twice daily
for 10-14 days) and symptomatic treatment (1mg/kg of prednisolone for
several days) in order to avoid complications [8].

The illness can be avoided by taking appropriate measures both at
home and in public health terms. Meat from wild boars that have been
hunted should be inspected by an approved laboratory (of which there
is on average one per Department in France), and the meat to be eaten
should be cooked all the way through. _Trichinella_ larvae are killed
after 3 minutes at 58 C, and almost immediately at 63 C. Microwave
ovens are not recommended for cooking the meat. Freezing for long
periods at low temperatures destroys the larvae: -22 C (domestic
freezers) for 80 hours, -26 C for 48 hours, or -32 C for 22 hours.
However, this method is not recommended, because certain species such
as _T. britovi_ are resistant to cold, and some other species are
sensitive to cold in certain hosts, but can be resistant to it in
other hosts. Curing the meat does not destroy the larvae if the water
content is under 0.92 (a long maturation period is required). In
theory, industrial curing processes with long maturation periods
should destroy the parasite. Smoking does not destroy _Trichinella_ larvae.

Public health measures based on the inspection of wild boar carcasses
are required before consumption. This is specified in the European
regulations [9], which are currently being introduced into French
law. The regulations require that infested meat be destroyed. Special
dispensations are allowed, particularly if the meat is to be eaten by
the hunter, and is not on sale to the public. Sampling of meat
(usually the tongue) for inspection by artificial digestion is
carried out either at designated centers by veterinary services
personnel or by the hunters themselves, who send samples to one of
the approved laboratories with an information form. Fewer than 7000
of more than 450 000 wild boar hunted each year in France [10] are
officially inspected. Therefore, it is likely that incidents of this
type will continue to occur, and it is important that specific
information continues to be targeted at exposed populations,
particularly hunters and others who eat wild game.

Acknowledgments:
Some of the data in this report come from the research contract
MedVetNet (Workpackage TRICHIMED,
<http://www.medvetnet.org/cms/templates/doc.php?id=71>
and NEMAGECO (ECCO2005 program).


References:

1. Dupouy-Camet J. Trichinellosis: a worldwide zoonosis. Vet
Parasitol 2000;93:191-200.

2. Dupouy-Camet J. Trichinellosis: still a concern for Europe. Euro
Surveill 2006;11
(< http://www.eurosurveillance.org/em/v11n01/1101-222.asp>)

3. Lancastre F, Houin R, Campana-Rouget Y, Le Fichoux Y, Deniau M.
Decouverte en France dans la region de Bourgogne - Franche-Comte d'un
foyer de trichinose sauvage. Ann Parasitol Hum Comp 1973;48:315-17.

4. Pozio E, La Rosa G, Serrano FJ, Barrat J, Rossi L. Environmental
and human influence on the ecology of Trichinella spiralis and
Trichinella britovi in Western Europe. Parasitology 1996;113:527-33.

5. Boireau P. Les trichinelloses animales. Special zoonoses, INRA
mens, Mai 2005, 23-24 et 30-31.

6. Boue F, Hars J, Terrier ME, Kuntz-Simon G, Le Potier MF, Mesplede
A, Garin- Bastuji B, Boireau P, Toma B, Pacholek X. Bilan du
programme national 2002/2003 de surveillance serologique des
sangliers sauvages. Peste Porcine Classique, Maladie d'Aujeszky,
Brucellose, Trichinellose. Rapport ONCFS/DGAl. 2003; 40p.

7. Hars J, Albina E, Artois M, Boireau P, Cruciere C, Garin B ,
Gauthier D, Hathier C, Lamarque F, Mesplede A, Rossi S.
Epidemiosurveillance des maladies du sanglier transmissibles aux
animaux domestiques et a l'homme. Epidemiol et sante anim 2000;37:31-43.

8. De Bruyne A, Vallee I, Ancelle T, Brocheriou I, Bonafe A, Boireau
P, Dupouy- Camet J. Trichinelloses. Encycl Med Chir-Mal Infectieuses
2006;8-517-A-10

9. COMMISSION REGULATION (EC) No 2075/2005 of 5 Dec 2005 laying down
specific rules on official controls for Trichinella in meat (Text
with EEA relevance). Official Journal of the European Union 2005;
L338/60: 22 Dec 2005.
(<http://eurlex.europa.eu/LexUriServ/site/en/oj/2005/l_338/l_33820051222en006000
82.pdf>)

10. ONCFS. Tableaux de chasse, Cerf - Chevreuil - Sanglier, Saison
2004 - 2005.
(<http://www.oncfs.gouv.fr/events/point_faune/mammifere/TCGG0405_FS271.pdf >}
[in French]

[Reported by: De Bruyne A 1/, Ancelle T /1,  Vallee I /2, Boireau P
/2, Dupouy-Camet J /1 <jean.dupouy-camet@cch.ap-hop-paris.fr >

1/ Centre national de reference des Trichinella; Universite
Paris-Descartes, Faculte de Medecine, Hopital Cochin Paris, France

2/ UMR BIPAR INRA-AFSSA-ENVA-UPMV, LNR Parasites, Maisons-Alfort, France]