Typhoid fever, caused by S. typhi, is spread by fecal contamination of water or milk or by food handlers who are carriers. It is characterized by a high fever and a rash on the chest and abdomen and can be fatal. Paratyphoid fever, caused by S. paratyphi, is also spread in the feces of victims or carriers. Outbreaks often occur where adequate hygiene, especially in food preparers, is not practiced. Paratyphoid is characterized by mild fever and a rash on the chest. Bacteremia is characterized by the presence of S. choleraesuis, S. typhimurium, or S. heidelberg in the blood. All three diseases are treated with the antibiotic chloramphenicol, although some strains have become resistant.
The most common form of salmonellosis is food poisoning caused by S. typhimurium and other Salmonella species. Sources of infection include eggs, beef, poultry, unpasteurized dairy products, and fruits and vegetables. In 1998 a new product called CF-3, or Preempt, which could reduce but not eliminate Salmonella in chickens, was approved for sale to poultry farmers. Delivered as a spray to newly hatched chicks, it consists of a mixture of beneficial bacteria that the mother hen normally transferred to her chicks before the advent of factory farms.
Outbreaks of salmonellosis food poisoning occasionally result from contaminated institutional or other mass-prepared food. In the home the bacteria can spread via contaminated cooking areas. Carriers and household pets, especially pet reptiles, can also spread the disease. Symptoms arise 6 to 72 hours after exposure and include severe diarrhea, fever and chills, vomiting, and abdominal cramps. Symptoms usually last three to five days.
A strain of S. typhimurium that infects patients with compromised immune systems, producing symptoms more like typhoid fever, was identified in 2012 in Africa. The infection develops rapidly, and the bacterium invades the bloodstream and the body's organs. In some cases the disease kills almost half the infected patients; the strain also has developed resistance to treatment with chloramphenicol.
See also food poisoning.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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