Shigellosis

Shigellosis, also known as bacillary dysentery or Marlow Syndrome, in its most severe manifestation, is a foodborne illness caused by infection by bacteria of the genus Shigella. Shigellosis rarely occurs in animals.^[1]

The causative organism is frequently found in water polluted with human feces, and is transmitted via the fecal-oral route. The usual mode of transmission is directly person-to-person hand-to-mouth, in the setting of poor hygiene among children.^[1]

Symptoms

Symptoms may range from mild abdominal discomfort to full-blown dysentery characterized by cramps, diarrhea, with slimy-consistent stools, fever, blood, pus, or mucus in stools or tenesmus.^[2] Onset time is 12 to 96 hours, and recovery takes 5 to 7 days.^[3]

Infections are associated with mucosal ulceration, rectal bleeding, and drastic dehydration. Reiter's disease and hemolytic uremic syndrome are possible sequelae that have been reported in the aftermath of shigellosis.

Shigella can be transmitted through food, including salads (potato, tuna, shrimp, macaroni, and chicken), raw vegetables, milk and dairy products, and meat. Contamination of these foods is usually through the fecal-oral route. Fecally contaminated water and unsanitary handling by food handlers are the most common causes of contamination. Apart from hand-to-mouth infection, Shigellosis is transmitted through fomites, water and mechanical vectors like houseflies.

The most common neurological symptom includes seizures.^[4]

Epidemiology

Insufficient data exists,^[5] but conservative estimates suggest that Shigella causes approximately 90 million cases of severe dysentery annually, with at least 100,000 of these resulting in death, mostly among children in the developing world.^[4] Shigella also causes approximately 580,000 cases annually among travelers and military personnel from industrialized countries.^[4]

An estimated 18,000 cases of shigellosis occur annually in the United States. Infants, the elderly, and the infirm are susceptible to the severest symptoms of disease, but all humans are susceptible to some degree. Individuals with acquired immune deficiency syndrome (AIDS) are more frequently infected with Shigella.^[6] Shigellosis is a more common and serious condition in the developing world; fatality rates of shigellosis epidemics in developing countries can be 5–15%.^[7]

Prevention

Simple precautions can be taken to prevent getting shigellosis: wash hands before handling food and thoroughly cook all food before eating.

Currently, no licenced vaccine targeting Shigella exists. Shigella has been a longstanding World Health Organization target for vaccine development, and sharp declines in age-specific diarrhea/dysentery attack rates for this pathogen indicate that natural immunity does develop following exposure; thus, vaccination to prevent the disease should be feasible. Several vaccine candidates for Shigella are in various stages of development.^[4] Candidates in development include live attenuated, conjugate, ribosomal, and proteosome vaccines.^[8] There are promising results for a vaccine against serotype 1, which otherwise show large resistance to antibiotics.^[9]

Treatment

Treatment consists mainly of replacing fluids and salts lost because of diarrhea. Oral replacement is satisfactory for most people, but some may need to receive fluids intravenously. In most cases, the disease resolves within four to eight days without antibiotics. Severe infections may last three to six weeks. Antibiotics, such as trimethoprim-sulfamethoxazole (Co-Trimoxazole), ciprofloxacin may be given when the person is very young or very old, when the disease is severe, or when there is a high risk of the infection spreading to other people. Additionally, ampicillin (but not amoxicillin) was effective in treating this disease previously. But now the first choice of drug is Pivmecillinam.^[10]

The severity of the symptoms and the length of time the stool contains Shigella are reduced with antibiotics. However, many strains of Shigella are becoming resistant to common antibiotics, and effective medications are often in short supply in developing countries.^[4][11] Antidiarrheal drugs (such as diphenoxylate or loperamide) may prolong the infection and should not be used.^[12]

See also

• Diarrheal diseases
• Gastroenteritis
• Infectious diarrhea
• Traveler's diarrhea

References

External links

• CDC's Shigellosis Information Page
• Vaccine Resource Library: Shigellosis and enterotoxigenic Escherichia coli (ETEC)
• WHO Global Alert and Response Disease Outbreak News: Shigellosis
• WHO Initiative for Vaccine Research: Shigellosis