‘I just bear up to my bewilderness’ Trichinella in undercooked bear meat, Japan, 2016

An outbreak of trichinellosis occurred in Japan in December 2016. All case-patients had eaten undercooked bear meat, from which Trichinella larvae were subsequently isolated. DNA sequencing analysis of the mitochondrial genes cytochrome c-oxidase subunit 1 and internal transcribed spacer 2 confirmed that Trichinella T9 had caused the outbreak.

Outbreak of Trichinella T9 infections associated with consumption of bear meat, Japan 

Emerging Infectious Diseases vol. 24 no. 8

Katsushige Tada, Hiromichi Suzuki, Yosuke Sato, Yasuyuki Morishima, Isao Nagano, Haruhiko Ishioka, and Harumi Gomi 


Raw meat does not confer ‘strength’ 12 sick with trichinellosis from wild boar, 2017

The U.S. Centers for Disease Control reports on January 15, 2017, a hospital physician notified the Alameda County Public Health Department (ACPHD) in California of a patient with a suspected diagnosis of trichinellosis, a roundworm disease transmitted by the consumption of raw or undercooked meat containing Trichinella spp. larvae (1).

A family member of the initial patient reported that at least three other friends and family members had been evaluated at area hospitals for fever, myalgia, abdominal pain, diarrhea, and vomiting. The patients had attended a celebration on December 28, 2016, at which several pork dishes were served, including larb, a traditional Laotian raw pork dish, leading the hospital physician to suspect a diagnosis of trichinellosis. Although the event hosts did not know the exact number of attendees, ACPHD identified 29 persons who attended the event and seven persons who did not attend the event, but consumed pork taken home from the event by attendees. The event hosts reported that the meat had come from a domesticated wild boar raised and slaughtered on their private family farm in northern California. ACPHD conducted a case investigation that included identification of additional cases, testing of leftover raw meat, and a retrospective cohort study to identify risk factors for infection.

Investigation and Findings

Contact information for additional attendees and exposed persons was obtained during interviews with confirmed attendees. Reports of suspected diagnoses of trichinellosis among event attendees were requested from hospital infection prevention specialists, outpatient clinic providers, and local health jurisdictions where event attendees lived.

Exposure to Trichinella was defined as consumption of pork in which Trichinella spiralis larvae were identified. Thirty-six potentially exposed persons were identified, including 29 who attended the event and seven who consumed food taken home from the event by attendees. Among the potentially exposed persons, 20 (56%) were interviewed, 16 for whom professional language interpreters were used. Fourteen potentially exposed persons were not interviewed because contact information was unavailable, and two persons could not be reached. Clinical and exposure information from all 20 persons who were interviewed was collected using a structured questionnaire administered by telephone 28–92 days after the December 28 event. Medical records for patients with a suspected diagnosis of trichinellosis were requested from hospitals and outpatient providers and abstracted. In consultation with the California Department of Public Health and CDC, ACPHD recommended serologic testing for Trichinella for all persons with a suspected diagnosis of trichinellosis using a commercial laboratory’s enzyme-linked immunosorbent assay* to detect immunoglobulin G (IgG) directed against a Trichinella excretory-secretory antigen.

An illness that was clinically compatible with trichinellosis was defined as the occurrence of 1) myalgia and fever; or 2) periorbital edema; or 3) eosinophilia (≥6% eosinophils), with or without gastrointestinal symptoms (e.g., diarrhea, vomiting, or abdominal pain) in an attendee or someone who had consumed food brought home by an attendee. A probable case was defined as clinically compatible illness in a patient with exposure to Trichinella. Confirmed cases were defined as laboratory-confirmed Trichinella infection (i.e., a positive serologic test for Trichinella IgG antibodies) in a patient with history of exposure and clinically compatible illness.

Ten confirmed and two probable cases of trichinellosis were identified; 11 occurred in men. Eleven patients self-identified as Asian, and one identified as Asian and white. The median age was 58 years (range = 39–71 years). Onset dates ranged from December 28, 2016, to January 23, 2017. Nine patients were hospitalized, two of whom were admitted to the intensive care unit; nine had sepsis, seven had acute kidney injury, and two had gastrointestinal bleeding, one case of which was attributed to nonsteroidal antiinflammatory drug use. Eight patients had elevated peak creatine phosphokinase levels indicating skeletal muscle damage (median = 2,821 μg/L; range = 566–25,467 [normal <200 μg/L]), and seven had elevated peak lactic acid levels, which is an indicator of sepsis (median = 3.1 mmol/L; range = 2.3–5.3 [normal = 0.5–2.2 mmol/L]). Six had elevated peak troponin levels indicating damage to the myocardium (median = 0.76 μg/L; range = 0.23–2.02 [normal <0.10 μg/L]). Ten cases were confirmed by a positive Trichinella serological test; two patients were not tested (Table).

Several event attendees had also assisted with food preparation. The three pork-containing dishes reported to have been served at the event included pork stew, grilled pork, and raw larb. Attendees were interviewed about preparation and consumption of the three pork dishes served at or taken home from the event, as well as consumption of any other pork-containing dishes served at the event and other sources of wild boar or bear meat. Attack rates and relative risks were calculated. Leftover raw pork from the implicated meal was obtained from the event hosts.

Larvae in an unstained touch preparation from the raw pork were verified as Trichinella spp. from a photomicroscopic image (Figure); samples were sent to CDC’s Division of Parasitic Diseases and Malaria diagnostic laboratory and identified as Trichinella spiralis through sequencing of the polymerase chain reaction–amplified ITS1-ITS2 region. Consumption of larb was significantly associated with trichinellosis, with an attack rate of 100% and a relative risk of 3.33 (95% confidence interval = 1.29–8.59). No other meat dishes were associated with an increased relative risk.

Public Health Response

The caretaker of the source farm could not be reached, but the event host who owns the farm reported that the caretaker purchased the pig from a private farm at age 5 weeks, raised it in an outdoor, fenced pen, and slaughtered it with the farm owner at age 2.5 years. The farm owner stated there are several pigs being raised on the farm, and the swine are only given commercial feed and never cooked or uncooked meat, offal, or garbage. The farm owner denied any rodent infestation issues on the farm but did state that small animals such as chicks had occasionally gotten into the fenced pen and been eaten by the pigs, indicating that small mammals infected with Trichinella could have entered the pen and been consumed by the swine. The event host has slaughtered pigs and served the fresh raw pork dish at previous celebrations; no illnesses had been reported before this event. Health education regarding safe food handling practices and avoiding consumption of raw meat was provided during interviews with potentially exposed persons and patients. The host was educated about reducing the risk for trichinellosis when consuming pigs from his farm by freezing raw meat for 30 days and cooking meat to a minimum internal temperature of 160°F (71.1°C) to kill Trichinella larvae (2). Although the host did not indicate that he would employ these risk reduction techniques, he did state that he would not serve raw pork from pigs from his farm in the future. Some patients said they would no longer eat raw meat; one patient reported he would continue to eat raw meat from animals that he hunts, believing that raw meat confers strength.


Historically, most cases of trichinellosis were associated with the consumption of raw or undercooked Trichinella-infected pork (median = 360 cases reported to CDC per year during 1947–1956); however, largely owing to improvements in agricultural and food processing standards (3), many fewer cases are currently reported (median = 14.5 cases reported per year during 2006–2015) (4). Whereas trichinellosis is rare in the United States, it remains a public health threat, especially among populations that consume raw or undercooked wild game meat or pork from noncommercial sources (5). Recent outbreaks of trichinellosis have been associated with wild boar, bear, walrus, and unspecified pork (4,6). The outbreak described in this report was linked to consumption of a privately raised boar, yet surveillance data during 2008–2012 identified just one case of trichinellosis linked to the consumption of home-raised swine (4), suggesting that this might be an underrecognized risk factor for trichinellosis. Home-raised and home-slaughtered swine produced for personal consumption typically are not subject to the same safety and inspection standards as are commercially produced swine and might be outside the purview of inspections by the state agriculture department or animal health board. Home-raised swine with access to the outdoors are also at risk for acquiring other zoonotic parasites, including toxoplasmosis and Ascaris suum (large roundworm of pigs). Educating persons who raise swine for personal consumption about these safety concerns by public health or agriculture authorities might mitigate the risks.

Clinical disease associated with trichinellosis can be severe and might include sepsis, which has rarely been reported in the English-language scientific literature. This outbreak investigation indicates that high-risk meat preparation and consumption practices might be part of valued cultural traditions. Public health, agriculture, and wildlife authorities should strengthen efforts to provide culturally competent education about trichinellosis prevention to private farmers, hunters, and communities whose cultural practices include raw meat consumption.


Marcos de Almeida, Henry Bishop, Kathleen Breen, Jeffrey Jones, Division of Parasitic Diseases and Malaria, CDC; Edward Powers, Infectious Diseases Branch, California Department of Public Health; Barbara Gregory, City of Berkeley Public Health Department, California; Susan Farley, Ileen Quimora, Contra Costa Public Health, Martinez, California.

Conflict of Interest

No conflicts of interest were reported.

Trichinellosis Outbreak Linked to Consumption of Privately Raised Raw Boar Meat — California, 2017

Morbidity and Mortality Weekly Report; March 2, 2018; 67(8);247–249

Dustin Heaton, MSN; Sandra Huang, MD; Rita Shiau, MPH; Shannon Casillas, MPH; Anne Straily, DVM; Li Kuo Kong, MD; Valerie Ng, MD, PhD; Viviana Petru, MD


16 sickened with trichinellosis in Belgium from imported wild boar meat

Trichinellosis is a rare parasitic zoonosis caused by Trichinella following ingestion of raw or undercooked meat containing Trichinella larvae. In the past five years, there has been a sharp decrease in human trichinellosis incidence rates in the European Union due to better practices in rearing domestic animals and control measures in slaughterhouses.

wild-boar-recipes-and-uses_homemediumIn November 2014, a large outbreak of trichinellosis occurred in Belgium, related to the consumption of imported wild boar meat. After a swift local public health response, 16 cases were identified and diagnosed with trichinellosis. Of the 16 cases, six were female. The diagnosis was confirmed by serology or the presence of larvae in the patients’ muscle biopsies by histology and/or PCR. The ensuing investigation traced the wild boar meat back to Spain. Several batches of imported wild boar meat were recalled but tested negative.

The public health investigation allowed us to identify clustered undiagnosed cases. Early warning alerts and a coordinated response remain indispensable at a European level.

Outbreak of Trichinellosis related to eating imported wild boar meat, Belgium, 2014

Eurosurveillance, Volume 21, Issue 37, 15 September 2016, DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.37.30341

P Messiaen, A Forier, S Vanderschueren, C Theunissen, J Nijs, M Van Esbroeck, E Bottieau, K De Schrijver, IC Gyssens, R Cartuyvels, P Dorny, J van der Hilst, D Blockmans


Trichinellosis in 3 French travelers after eating bear meat in Greenland

Jean Dupouy-Camet reports to ProMED-mail that on 11 Mar 2016, a 55-year-old patient presented to the Parasitology Clinical Service of Cochin Hospital in Paris complaining of high fever and muscular pain that he had been suffering from since 4 Mar 2016.

Green-MeatHe was part of a group of 3 French people having recently travelled in East Greenland. Between, 13 and 16 Feb 2016, they each had consumed around 200 g of polar bear (_Ursus maritimus_) meat. The polar bear meat had been cut into 1 cm thick slices and then fried for several minutes, but was still pink when eaten.

One of the consumers, aged 56, was totally asymptomatic besides one day of pronounced diarrhea at the beginning of March. On 9 Mar 2016 the last consumer, aged 59, developed fever, myalgia and a slight facial edema and one day of diarrhea. Blood tests were performed on all the patients and showed both elevated muscle enzyme and eosinophile levels.

Antibody testing for _Trichinella_ was positive by ELISA and western blot for the 3 patients (LDBio Diagnostics, France) and they were prescribed albendazole for 10-days. The polar bear, weighing around 400 kg, was shot by a local accredited Inuit hunter in the Scorebysund region on the East coast of Greenland.

Only the 3 French travellers ate under-cooked meat, whereas local people ate the meat boiled and have been informed that the polar bear was infected with _Trichinella_. None of the meat was imported to France.

Careful with that bear meat: Trichinellosis surveillance, US, 2008–2012

The U.S. Centers for Disease Control reports that trichinellosis is a parasitic disease caused by nematodes in the genus Trichinella, which are among the most widespread zoonotic pathogens globally. Infection occurs following consumption of raw or undercooked meat infected with Trichinella larvae.

Trichinella2Clinical manifestations of the disease range from asymptomatic infection to fatal disease; the common signs and symptoms include eosinophilia, fever, periorbital edema, and myalgia. Trichinellosis surveillance has documented a steady decline in the reported incidence of the disease in the United States. In recent years, proportionally fewer cases have been associated with consumption of commercial pork products, and more are associated with meat from wild game such as bear.

Period Covered: 2008–2012.

Description of System: Trichinellosis has been a nationally notifiable disease in the United States since 1966 and is reportable in 48 states, New York City, and the District of Columbia. The purpose of national surveillance is to estimate incidence of infection, detect outbreaks, and guide prevention efforts. Cases are defined by clinical characteristics and the results of laboratory testing for evidence of Trichinella infection. Food exposure histories are obtained at the local level either at the point of care or through health department interview. States notify CDC of cases electronically through the National Notifiable Disease Surveillance System (available at http://wwwn.cdc.gov/nndss). In addition, states are asked to submit a standardized supplementary case report form that captures the clinical and epidemiologic information needed to meet the surveillance case definition. Reported cases are summarized weekly and annually in MMWR.

Results: During 2008–2012, a total of 90 cases of trichinellosis were reported to CDC from 24 states and the District of Columbia. Six (7%) cases were excluded from analysis because a supplementary case report form was not submitted or the case did not meet the case definition. A total of 84 confirmed trichinellosis cases, including five outbreaks that comprised 40 cases, were analyzed and included in this report. During 2008–2012, the mean annual incidence of trichinellosis in the United States was 0.1 cases per 1 million population, with a median of 15 cases per year. Pork products were associated with 22 (26%) cases, including 10 (45%) that were linked with commercial pork products, six (27%) that were linked with wild boar, and one (5%) that was linked with home-raised swine; five (23%) were unspecified. Meats other than pork were associated with 45 (54%) cases, including 41 (91%) that were linked with bear meat, two (4%) that were linked with deer meat, and two (4%) that were linked with ground beef. The source for 17 (20%) cases was unknown. Of the 51 patients for whom information was reported on the manner in which the meat product was cooked, 24 (47%) reported eating raw or undercooked meat.

Interpretation: The risk for Trichinella infection associated with commercial pork has decreased substantially in the United States since the 1940s, when data collection on trichinellosis cases first began. However, the continued identification of cases related to both pork and nonpork sources indicates that public education about trichinellosis and the dangers of consuming raw or undercooked meat still is needed.

Public Health Actions: Changes in domestic pork production and public health education regarding the safe preparation of pork have contributed to the reduction in the incidence of trichinellosis in the United States; however, consumption of wild game meat such as bear continues to be an important source of infection. Hunters and consumers of wild game meat should be educated about the risk associated with consumption of raw or undercooked meat.


Of course it came from Missouri; trichinellosis caused by consumption of wild boar meat — Illinois, 2013

It sounds like something Amy would have eaten when she was a kid. Maybe that’s why she’s still attracted to me – there’s a parasitic worm affecting her cognitive abilities.

The U.S. Centers for Disease Control reports that on March 6, 2013, the Cook County Department of Public Health (Chicago, Illinois) contacted the Illinois Department of Public Health regarding a diagnosis of trichinellosis in a patient who had consumed wild boar and deer meat obtained by hunting at a Missouri ranch January 16–18. Trichinellosis is a parasitic infection caused by consumption of undercooked infected meat, most commonly from carnivorous or omnivorous animals (1).

he_WildBoarThe Cook County and Illinois health departments and the Missouri Department of Health and Senior Services queried the Illinois and Missouri electronic reportable disease registries and interviewed patients to identify additional cases and describe patients’ clinical characteristics. CDC performed immunoglobulin G enzyme-linked immunosorbent assay testing of patient serum and microscopically examined the meat for evidence of Trichinella larvae.

Patient interviews revealed that the index patient had ground the wild boar and deer meat into sausage and served it to three family members who had participated in the hunt. The sausage was shared with a friend and the friend’s four family members, none of whom had participated in the hunt. A case was defined as illness in a person who consumed the implicated meat and had positive serology or myalgias. Nine cases were identified. All nine persons had consumed the implicated sausage during January 20–February 16 and experienced illness compatible with trichinellosis during February 13–March 4; three of six tested had a positive serologic test for antibodies specific to Trichinella within 7 days of symptom onset. No one else consumed the sausage, and no additional cases were identified from electronic disease registries.

Among the nine cases, five occurred among men (median age = 35 years; range = 20–54 years), and the median incubation period was 16 days (range = 4–24 days). All patients reported myalgias, eight had periorbital edema, and seven had both fever and eosinophilia. Trichinella spiralis larvae were identified microscopically in the sausage but not in the deer meat, indicating that the boar meat was the likely source. All patients were treated solely with albendazole and recovered without complications.

Trichinellosis cases remain infrequent in the United States because of state and federal laws preventing feeding of uncooked swill to commercial swine and public awareness of the danger of eating raw or undercooked game meat. The Missouri Department of Health and Senior Services provided additional education to employees of the ranch about the risk for Trichinella ingestion and the need to inform hunting patrons. The Illinois Department of Public Health recommends posting advisories at hunting ranches that inform hunters of the importance of cooking game meat to the cooking temperature of 71°C (160°F) recommended by the U.S. Department of Agriculture and CDC before consuming it (2).