Potential Bioterrorism Agent: Category B
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Physician: Report by facsimile, mail or phone
Local Public Health Agency (LPHA): Report by IDSS, facsimile, mail or phone. Follow-up required
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Salmonellosis is caused by Salmonella bacteria other than Salmonella typhi, (the Salmonella species that causes typhoid fever). There are approximately 2,000 known serotypes; only about 200 are detected in the U.S. in any given year. Infection may begin as acute diarrhea and develop into septicemia (blood infections) or focal infection. Infectious dose of Salmonella is usually over 10, 000 organisms.
B. Clinical Description
Symptoms of Salmonellosis are diarrhea (sometimes bloody), headache, stomach cramps, fever, nausea, and sometimes vomiting. The infection may also appear as septicemia, an abscess, arthritis or cholecystitis.
Onset of illness may begin as acute enterocolitis and develop into septicemia or focal infection. Anorexia and diarrhea often persist for several days.
Complications include dehydration that may be severe, especially among infants and the elderly, and invasive disease may occur. Occasionally, the infectious agent may localize in any tissue of the body, produce abscesses and cause septic arthritis, cholecystitis, endocarditis, meningitis, pericarditis, pneumonia, pyoderma, or pyelonephritis. Deaths are uncommon, except in the very young, the very old, the debilitated and the immunosuppressed. It is estimated that 400 fatal cases occur each year; a few cases are complicated by chronic arthritis.
Common reservoirs: humans, livestock, pets, poultry and other birds, reptiles and amphibians. Most infected animals are chronic carriers and may be asymptomatic.
D. Modes of Transmission
Spread via the fecal-oral route. By far the most common mode of transmission is ingestion of food or water that has been contaminated with animal feces. This includes raw or undercooked poultry, meats, and raw milk or milk products. Eggs can become infected “in utero,” thus should be cooked until no longer runny, or pasteurized egg products used. In addition, reptiles such as iguanas, snakes and lizards are often chronic carriers of these bacteria and can be sources of infection.
Person-to-person spread can occur when an infected food handler contaminates food. A large dose of organisms is usually needed to cause infection, but the infectious dose may be lower for certain susceptible groups such as children, the elderly and the immunocompromised. Most often, person-to-person spread occurs among household contacts, preschool children in child care, and the elderly and developmentally disabled living in residential facilities. Transmission can also occur person-to-person through certain types of sexual contact (e.g. fecal - oral contact).
E. Incubation period
The incubation period can vary from 6 - 72 hours but is usually about 12 - 36 hours. Longer incubation periods of up to 16 days have been documented and may not be uncommon following low-dose ingestion. The higher the infectious dose of the organism, the shorter the incubation period.
F. Period of Communicability or Infectious Period
The disease is communicable for as long as infected persons excrete Salmonella bacteria in their stool, but most likely while diarrhea exists. This can last from days to months, depending on the serotype, but rarely lasts more than one year. Treatment with antibiotics can prolong carriage. However, due to large infectious dose, transmission from carriers is very uncommon.
Salmonellosis has a worldwide distribution, with approximately 1.4 million cases occurring annually in the United States alone. An estimated 1.2 million cases occur annually in the United States; of these, approximately 42,000 are laboratory-confirmed cases reported to CDC. Salmonella serotypes Enteritidis, Typhimurium, and Newport account for about half of culture-confirmed Salmonella isolates reported by public health laboratories in the U.S.
About 60-80% of cases are sporadic, but large outbreaks have occurred in institutional settings and nationwide from common food sources. The largest common-vehicle outbreak of salmonellosis ever recognized in the United States was caused by ice cream made by a large national producer when the ice cream premix was transported in contaminated tanker trucks.
H. Bioterrorism Potential
Category B Agent: Salmonella has been used as a bioterrorism agent. In one well-known example in 1984, a religious sect in Oregon deliberately contaminated salad bars at restaurants with Salmonella to disrupt an election process. Over 700 people became ill.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Salmonella can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2015 Red Book: Report of the Committee on Infectious Diseases, 30th Edition. Illinois, American Academy of Pediatrics, 2015.
CDC web site, Salmonellosis; www.cdc.gov/salmonella/
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20ͭͭ ͪ Edition. Washington, DC, American Public Health Association, 2015.
USDA web site providing latest information on salmonellosis in animals www.aphis.usda.gov/
FDA web site providing the latest food recalls: www.fda.gov/opacom/7alerts.html