Shigellosis
Shigellosis is an intestinal infection caused by Shigella bacteria, primarily affecting the gastrointestinal system. It is highly prevalent in developing countries, often linked to conditions such as poverty, malnutrition, poor hygiene, and overcrowding, making it a significant public health concern. The infection is characterized by acute symptoms, including abdominal cramps, a painful urge to defecate, bloody and mucus-filled diarrhea, fever, and malaise. Globally, it accounts for a substantial portion of bloody diarrhea cases, particularly among children under five years old, with an estimated 600,000 fatalities annually—most in Sub-Saharan Africa and South Asia.
There are four main species of Shigella that cause shigellosis: S. dysenteriae, S. flexnerii, S. sonnei, and S. boydii. Transmission occurs from person to person, as there is no animal reservoir. While antibiotic treatments can be effective, rising resistance to these medications poses challenges, and research is ongoing for potential vaccines. Understanding and addressing the underlying social determinants that contribute to the spread of shigellosis is crucial for reducing its incidence and impact.
Shigellosis
ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system
DEFINITION: An intestinal infection caused by Shigella bacteria
CAUSES: Bacterial infection; often related to poverty, malnutrition, poor hygiene, and overcrowding in developing countries
SYMPTOMS: Abdominal cramps, painful urge to defecate, bloody and mucus-filled diarrhea, fever, malaise
DURATION: Acute
TREATMENTS: Antibiotics
Causes and Symptoms
Shigellosis accounts for half of the cases of bloody diarrhea in developing countries and a smaller portion of diarrheal illness in the United States. As of 2024, the Centers for Disease Control and Prevention (CDC) reported 80 to 165 million cases occur annually across the world and in all age groups. An estimated 600,000 people die of the infection annually, most of them children. Named after Kiyoshi Shiga, a Japanese scientist who performed much of the original research about it in the aftermath of an 1896 epidemic, Shigella is a gram-negative bacillus. The four species that cause shigellosis are S. dysenteriae, S. flexnerii, S. sonnei, and S. boydii.
The severity of shigellosis is quite variable, ranging from mild diarrhea to death. The more severe illness, dysentery, is characterized by abdominal cramps, tenesmus (a painful urge to defecate), and a bloody, mucus-filled diarrhea. Most victims of this severe illness are children, with those under age five years being particularly at risk. According to the WHO, 443,832 children died in 2024 from severe diarrhea worldwide. Most of those lived in Sub-Saharan Africa and South Asia. Poverty, malnutrition, poor hygiene, and overcrowding are associated with this serious disease, which is almost never seen in industrialized countries except in travelers who have visited an endemic area of the world. Shigella dysenteriae type 1 is responsible for most of these severe cases.
The pathogenicity (or disease-causing mechanism) of shigellosis is the invasion of the intestinal lining by the bacteria, causing inflammation and ulceration of the intestinal wall. Although Shigella bacteria also produce a toxin, the role of this toxin in the infection is less clear and remains a research topic of much interest. In contrast to some other intestinal infections such as cholera, shigellosis produces a relatively small fluid volume loss, making dehydration less problematic. Victims also suffer from fever, malaise, and decreased appetite. Transmission of the Shigella bacteria is from person to person; there is no animal reservoir.
Treatment and Therapy
The diagnosis of shigellosis is made by the growth of Shigella in a stool culture. Antibiotic treatment is helpful, but resistance to many antibiotics is increasing. Quinolones, such as ciprofloxacin, are the treatment of choice for adults. Children are often treated with a cephalosporin or a variety of other agents. Azithromycin has been used successfully for multidrug resistant cases. Research continues on a possible vaccine.
Bibliography
Alam, N. H. “Treatment of Infectious Diarrhea in Children.” Pediatric Drugs 5.3 (2003): 151–65. Print.
Bhattacharya, S. K. “An Evaluation of Current Shigellosis Treatment.” Expert Opinion on Pharmacotherapy 4.8 (Aug. 2003): 1315–20. Print.
"Shigellosis." MedlinePlus, medlineplus.gov/ency/article/000295.htm. Accessed 8 Apr. 2024.
"Shigellosis." National Institute of Allergy and Infectious Diseases. NIH, 15 Sept. 2015. Web. 16 May 2016.
"Shigella." World Health Organization, 30 Mar. 2024, www.who.int/teams/immunization-vaccines-and-biologicals/diseases/shigella. Accessed 8 Apr. 2024.