For nearly a year between July 2016 and May 2017, Alaska health officials reported two outbreaks of trichinellosis in the Norton Sound region associated with consumption of raw or undercooked walrus meat; five cases were identified in each of the two outbreaks.

Image/skeeze via pixabay
Image/skeeze via pixabay

Walrus meat has been implicated in half of all trichinellosis cases reported in Alaska since 1975, yet the frequency of walrus-associated trichinellosis in the state has declined in recent years for unknown reasons.

These were the first multiple-case outbreaks of walrus-associated trichinellosis in Alaska since 1992, according to a CDC MMWR report published today.

The report details the two outbreaks which were first recognized in August 2016 and May 2017, respectively.

The significance of wild game species in the epidemiology of trichinellosis is apparent in Alaska. Among 241 trichinellosis cases reported in the state since 1975, 227 (94%) were attributed to consumption of nonporcine wild game, including ursid species (black bear [Ursus americanus], grizzly bear [Ursus arctos], and polar bear [Ursus maritimus]) and pinniped species (walrus and sea ice–associated seal species). Under the Marine Mammal Protection Act, Alaska Natives may harvest marine mammals for subsistence purposes. Walruses, polar bears, and several sea ice–associated seal species are important for the nutritional, cultural, and economic well-being of many coastal communities in northern and western Alaska.

In the Arctic, trichinellosis, or trichinosis, is caused by a microscopic parasite called Trichinella nativa, sometimes found in the meat of wild mammals like polar bears, black bears, wolves, foxes and, most commonly, walruses.

Trichinosis is a parasitic disease caused most commonly by the roundworm Trichinella spiralis. If someone ingests undercooked or raw meat with the encysted larvae, the stomach acid releases the larvae which mature to adults in the intestine.

Trichinella spiralis parasite
Trichinella spiralis cysts

After about a week the female starts releasing larvae which enter the bloodstream and find their way to skeletal muscle where they encapsulate.

There can be gastrointestinal symptoms mimicking acute food poisoning when there is activity of the adults in the intestine.

Sudden appearance of fever, muscle soreness and pain with swelling of parts of the face is early classic signs. This can sometimes be followed by retinal hemorrhages and other ocular signs.

With heavy infections cardiac, respiratory and neurological problems may ensue with death by heart failure being most common. The more larvae you ingest, the more serious the disease.

The report closes with: These outbreaks also highlight the importance of culturally sensitive public health messaging. In areas where wild game species are harvested for subsistence, traditional methods of collecting, handling, preparing, storing, and consuming meat often have great cultural significance; however, some of these methods can be inconsistent with public health best practices. Rather than promoting or proscribing specific methods, public health messages that focus on communicating risks and explaining the manner and magnitude of risk reduction that can be achieved using different approaches (e.g., alternative methods of preparing meat for consumption) enable members of the target population to make informed decisions that integrate their traditional practices with their awareness and tolerance of risks.

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