Trichinellosis acquired in Nunavut, Canada in September 2009: meat from grizzly bear suspected

05.nov.09
Eurosurveillance, Volume 14, Issue 44,
S Houzé, T Ancelle, R Matra, C Boceno, Y Carlier, A A Gajadhar, J Dupouy-Camet

Five cases of trichinellosis with onset of symptoms in September 2009, were reported
in France, and were probably linked to the consumption of meat from a grizzly bear
in Cambridge Bay in Nunavut, Canada. Travellers should be aware of the risks of
eating raw or rare meat products in arctic regions, particularly game meat such as
bear or walrus meat.
Case detection and description
On 5 October 2009, the French National Reference Centre (NRC) for Trichinella was
informed about a possible case of trichinellosis in an individual returning from
Nunavut, Canada. This very asthenic patient had high eosinophil counts and elevated
plasma levels for muscle enzymes. Specific antibodies were detected by ELISA and
Western-blot (Diasorin & LDBio, France). The patient belonged to a group of five
marine navigators who had travelled from the Aleutian Islands to Greenland and
crossed the North-West Passage in northern Canada. The NRC started an investigation
and identified four more cases among these travellers. Case 2 presented primary
symptoms of shivers and fever without diarrhoea on 7 September. At the time she had
been diagnosed with influenza but symptomatic treatment did not improve her
condition. As high fever (40.4° C), intense muscular and joint pain, extreme
asthenia and bilateral inferior limbs oedema persisted, the patient was hospitalised
on 22 September. She also had elevated levels of eosinophils and muscle enzymes and
was serologically positive on 30 September for trichinellosis (ELISA and
Western-blot). The third and fourth crew members also had asthenia, high levels of
eosinophils and muscle enzymes; one had a lasting diarrhoeal disease at the end of
August; these two cases were tested positive by ELISA and Western-blot by the NRC
and Biomnis lab in late October. The fifth traveller, living in Brussels, was also
investigated and found to have been initially diagnosed with influenza but
subsequently revised as trichinellosis (particularly when the link was made with the
other cases) with manifestations of fever, myalgia, increased eosinophils and
muscular enzymes levels and positive serology. Serological assays were not performed
on one of the two patients with mild symptoms. No cardiac or neurological
complications were observed. Only case 2 was hospitalised, discharge occurring 11
days later. All patients were treated with albendazole (7.5 mg/kg twice a day for 10
days) and corticosteroids were used in the first case and in the hospitalised
patient (case 2).
Outbreak investigation
During the travel expedition many stopovers were made in Inuit's villages, and, on
these occasions, the crew consumed meat of various wild animals: caribou, walrus,
seal, polar bear and grizzly bear. Considering the occurrence, onset and duration of
signs and symptoms, the source of infection were probably grizzly (Ursus arctos)
steaks which were consumed in the Cambridge Bay area (Iqaluktuuttiaq), Victoria
Island, Nunavut, Canada between the 19 and 22 August 2009. Information obtained from
residents of Cambridge Bay indicated the grizzly bear was shot at Elu Inlet Lodge,
at the beginning of August, transported fresh to Cambridge Bay where it was frozen
for about a week. A leg was thawed, cut into pieces and given to the travellers. The
pieces were frozen again for two days. After departure, the meat was stored for two
additional days in the boat. All five members of the crew consumed this meat,
barbecued or pan-fried, on several occurrences after the 19 August. All the
remaining meat from the bear was consumed locally in Cambridge Bay, but well cooked
and no suspected cases were reported. The Centre for Food-borne & Animal
Parasitology, Canadian Food Inspection Agency, in Saskatoon, Canada was contacted on
6 October 2009 and informed of the outbreak. In the course of the investigations, it
was established that, for some time, the boat of the five travellers sailed together
with another one with four persons on board and members of both crews ate at the
same places. The second boat was on the way for Halifax, Canada in mid-October when
the crew was contacted by email and alerted of the possibility of trichinellosis
infection and of specific preventive and treatment measures that might be necessary.
According to their blog, one of the crew members had been affected by a persistent
flu during the same period as the travellers on the first boat. But no additional
information could be obtained from this second crew.
Discussion
This report illustrates well the fact that trichinellosis can be misdiagnosed for
influenza, which is particularly important in the context of the pandemic H1N1
influenza outbreak when health professionals and the general public are more
inclined to suspect influenza. Misdiagnosis of trichinellosis for influenza is not
unusual because the initial clinical symptoms of these diseases occurring at the
acute stage of infection are not pathognomonic. In another occurrence, Laurichesse
et al. [1] emphasized that "general practitioners could have misdiagnosed cases of
trichinellosis because they did not routinely order serological tests". The presence
of specific clinical and biological signs (facial oedema, elevated levels of
eosinophils and muscle enzymes, and specific antibodies) can readily confirm the
diagnosis of trichinellosis.
Trichinellosis is a widespread helminthic zoonosis endemic in northern Canada where
the incidence rate among the indigenous population was estimated at 11 cases per
100,000 [2], which is 200 times the national Canadian rate [3]. Walrus (Odobenus
rosmarus) meat is the most frequent source of trichinellosis infection in humans;
polar bear (Ursus maritimus) seems to be less important. Trichinella nativa and the
genotype T6 are widespread in northern Canada [4,5]. The precise genotype
responsible for this small outbreak could not be determined, as the infected meat
was not conserved and no muscular biopsies were performed. In an extensive survey
recently performed on wildlife across northern Canada, Gajadhar and Forbes found
that 29.4 % of grizzly bears examined harboured Trichinella larvae [5]. The
prevalence was 65.9% among polar bears, 40.6% in walrus and 7.3 % in black bears
(Ursus americanus). There are no other recent survey reports for Trichinella in wild
fauna in Nunavut, except for a survey of wolverines (Gulo gulo) which found 87.8 %
of these animals positive [6]. Outbreaks of trichinellosis among Inuit population
have been described earlier in Nunavut on Baffin Island [7] and Repulse Bay [8].
They occurred in the local residents after consumption of walrus meat. Apparently,
Inuit populations consume bear meat thoroughly cooked whereas walrus meat is eaten
frozen, fermented or air-dried [9]. An earlier study has shown that traditional
northern foods used by Inuit can harbour infective Trichinella larvae [10]. Other
outbreaks, linked mainly to walrus meat consumption have been described in
neighbouring Nunavik (from Inukjuak on south Hudson Bay and as far north as Salluit)
leading to the development and implementation of a prevention program for
trichinellosis in Inuit communities [8,9]. We also described, in 2005, an outbreak
of trichinellosis among French hunters and their families in France after
consumption of black-bear meat obtained from northern Quebec [11,12]. Apparently,
French tourists, especially hunters, are particularly fond of bear meat. Including
the present report, a total of 25 cases linked to bear meat consumption have been
reported to the NRC since 1995 [12]. The present outbreak appears to be associated
with the most northern geographic area described to date in Canada with grizzly bear
meat as source. As shown in this report, the arctic species of Trichinella (T.
nativa and T6) are resistant to freezing and are killed by sufficient cooking at
67°C. Travel in endemic regions is a classical driver for acquiring trichinellosis,
and travellers should be aware of the risks of eating raw or rare meat products,
particularly game meat such as bear or walrus meat [13].
Acknowledgements
Many thanks to Sophie Lecam (Biomnis lab, Lyon, France) and Vicki Aitaok from the
Arctic Coast Visitor Centre (Iqaluktuuttiaq, Nunavut, Canada).
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