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Botulism
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Botulism in Alaska
Seasonality, types, and location Foods Prevention Other aspects of botulism in Alaska Unanswered questions
SurveillanceAs already mentioned, botulism is a public health emergency and health care providers should report all suspected cases to the Alaska Division of Public Health, Section of Epidemiology. Since 1947, the Alaska Area Native Health Service of the Indian Health Service, the Arctic Investigations Program of the U.S. Centers for Disease Control and Prevention (CDC), and the Alaska Division of Public Health have conducted epidemiologic investigations of all patients with possible botulism. Although early records contain less detail, results of the investigations have been collected and analyzed.CasesFor this monograph, the definitions of confirmed and possible botulism explained in Table 5 were used. Botulism cases may go undiagnosed and therefore unreported if a person either does not seek medical care or the diagnosis is not considered. However, since laboratory confirmation requires testing which is only available from the CDC, the botulism cases summarized here likely represent all confirmed cases in Alaska from 1947 through 1997.
From 1950 to 1997, 105 confirmed outbreaks of foodborne botulism involving 214 persons occurred in Alaska (there were no confirmed cases during 1947-1949) (Figure 1). Almost exactly half (51/105) of the outbreaks had more than one case and seven outbreaks had five or more cases. The largest outbreak, with nine cases, occurred in 1973. All cases occurred in Alaska Natives. The average annual incidence among Alaska Natives increased from 3.5 cases/100,000 population during 1950-1954 to 10.7 cases/100,000 during 1995-1997 (Table 6). Reasons for the increase are unknown but may relate to changes in food preparation practices or improved recognition of mild cases. The mean age of persons at onset of foodborne botulism, 43 years, did not change substantially during 1950-1997 (correlation coefficient=0.17; r2=0.03). Illness was relatively uncommon in children - only 11 cases were 12 years of age or less. There have been a total of 19 deaths for an overall case fatality rate of 9%. The case fatality rate declined from 31% during 1950-1959 to 5% during 1990-1997.
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Seasonality, types, and locationOutbreaks occurred in every month of the year (Figure 2). Slightly over half of the outbreaks (55 of 100 with a known date) occurred during June through September. Type E botulism was by far the most frequent type, accounting for 82% (86/105) of the outbreaks, 79% (169/214) of the cases, and 84% (16/19) of the deaths.Types A and B botulism caused 9 and 32 cases, respectively. Botulism occurred predominantly in coastal villages in the western and southeastern parts of the state (Figure 3).
FoodsIn 53 (50%) of the outbreaks and 109 (51%) of the cases, an implicated food sample tested positive for botulism toxin (Table 7). The remaining outbreaks were confirmed as a result of either a positive toxin assay of a patient's serum, stool, or gastric contents; or a positive culture of a patient's stool specimen for C. botulinum organism. When food samples did not contain botulism toxin, the results of the epidemiologic investigation were used to identify the food most likely responsible for the outbreak.
A variety of traditional Alaska Native foods including seal, whale, and fish have been implicated (Table 7). The commonest method of preparation was fermentation - a process in which fresh food was allowed to putrefy for 1 to 2 weeks in either a pit in the ground or a closed or air-tight container (Table 8). No cases of foodborne botulism in Alaska have been associated with home canned food.
PreventionPrevention and control of foodborne botulism in Alaska remains problematic. Although a multivalent toxoid which includes types A, B, and E is available, immunization of the entire population is not practical or indicated. Strategies for controlling foodborne botulism fall largely into two approaches: (1) reducing contamination of food with C. botulinum spores and preventing toxin production in food, and (2) early identification of botulism cases. Reducing contamination and preventing toxin formation are difficult to achieve. Subsistence hunting and fishing remain an integral part of Alaska Native life and botulism spores, particularly type E, are ubiquitous in Alaska.In addition, the traditional methods of preparation of fermented foods produce a flavor and texture that is altered and generally unacceptable if procedures such as cooking are added to the process. However, the traditional methods have been made even more unsafe with the current use of airtight containers - glass and plastic jars, buckets, and plastic bags and the practice of accelerating the process by fermenting food in a warm environment. Attempts to educate preparers of traditional fermented foods in methods to reduce the risk of botulism have not as yet been successful. In contrast to the lack of success in controlling foodborne botulism by educating the preparers, educating health care providers to recognize botulism early in its clinical course and to report cases promptly has proved effective in limiting adverse outcomes. Educational efforts directed toward eliciting a careful food consumption history, having a high level of suspicion when confronted with illness with gastrointestinal and neurologic symptoms, and use of the "diagnostic pentad" have been the mainstay of control efforts in Alaska. These educational efforts combined with rapid epidemiologic investigation of suspected cases, prompt supportive care, and the availability of botulism antitoxin may be responsible for the decrease of the case fatality rate.
Other aspects of botulism in AlaskaC. botulinum spores are widely distributed in the Alaska environment. Miller, Clark, and Kunkle (1972) demonstrated type E botulism toxicity in enrichment cultures of 17 of 23 beach soil samples collected in the Kotzebue region. Other investigators (Houghtby and Kaysner 1969) detected low level intrinsic contamination of Alaska salmon with type E C. botulinum spores. Among 589 pink, sockeye, chinook, and chum salmon collected from Bristol Bay, Southeastern Alaska, Kodiak, and the Yukon River, 6 (1%) had gill specimens yielding positive cultures for type E toxin. None of 494 viscera specimens were positive.Probably the most extensive environmental survey for C. botulinum in Alaska was conducted by Miller (1975). Samples of beach soil, ocean water and sediments, salmon, and marine mammals were collected from 23 sites in both interior and coastal areas. As shown by the results summarized in Table 9, type E C. botulinum spores were widely distributed. No other type of C. botulinum was identified and, with one exception, no specimens from north of Point Hope were positive. Shaffer et al. (1990) surveyed Alaska Native food consumption patterns and preparation practices in the Bristol Bay region in 1987. In four Yupik villages, they found that fermented foods were regularly prepared by 15% of high school students, 71% of students' parents, and 80% of their grandparents. Fermentation practices appeared to have changed from the traditional method of using a clay pit in the ground. Only 13% of preparers reported that they used the traditional method to ferment fish heads while 42% used a wooden barrel above ground, 38% used a wooden barrel in the ground, and 8% used a plastic bucket above ground. These findings suggested that changes in food preparation practices have resulted in fermentation taking place in warmer conditions which are known to favor the production of botulism toxin.
Unanswered questionsMany questions concerning botulism in Alaska remain unanswered. Future studies may improve our understanding of botulism pathophysiology, treatment, and ecology. Important concerns include:
Botulism remains a fascinating illness which challenges the clinician to make a diagnosis using the classic elements of medical practice--history and physical examination. Once the diagnosis is made the patient's life may well have been saved. Clinical opportunities like this do not come often, but can be extremely satisfying if appropriately handled. Practitioners who care for Alaska Natives have a reasonably high likelihood of encountering botulism. They should be alert to this possibility and act decisively if the diagnosis is entertained.
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