SHIGELLOSIS
Shigellosis is the commonest cause of bacillary dysentery in children, characterized by: (a) typical small volume, bloody-mucoid stools with extreme frequency, (b) high fever with toxic appearance and (c) risk of systemic complications.
TABLE 10.13: Complications of Shigellosis
TABLE 10.14: Common causes of dysentery
• Dehydration, dyselectrolytemia
• Hypoglycemia
• Septicemia and DIC
• Seizures, encephalopathy*
• Renal failure, hemolytic uremic syndrome
• Hemolytic anemia, thrombocytopenia
• Local: Rectal prolapse, toxic megacolon
• Others**: Arthritis, Reiter syndrome, hepatitis, myocarditis *Ekeri syndrome: Hyperpyrexia, toxic appearance, seizures, coma and death, without significant sepsis/dehydration
**? autoimmune ?? toxin-mediated
Epidemiology: Shigellosis is caused by one of the four species—S.
dysenteriae (commonest), S. flexneri, S. boydii and S. sonnei. Contaminated food and water is the commonest source of infection, though person-to-person transmission through infected food handlers is common. High-risk factors: It is most common in pre-school age group (except in breastfed infants due to protective antibodies in breast milk) and institutionalized children, e.g. orphanages and daycare centers. While most cases are endemic in India, intermittent outbreaks are common in rainy season.Pathogenesis: Shigella requires very low inoculum to produce clinical disease, mainly caused by invasion of colonic epithelium (invasive disease). However, some strains of S. dysenteriae produce a powerful exotoxin— Shiga toxin and/or an endotoxin (ShET1).
Pathological lesions are characterized by intense mucosal inflammation and formation of multiple ulcers, mainly in distal colon. Development of secretory IgA and type-specific serum antibodies leads to spontaneous recovery after 7-10 days in uncomplicated cases.
Chronic diarrhea is rare.Clinical manifestations develop after a short incubation period of 1-3 days, with:
• Acute watery diarrhea, which rapidly evolves into typical small-volume blood and mucus mixed stools with high frequency (15-20/day), urgency, painful defecation (strangury) and colicky abdominal pain.
• High fever, toxic appearance and other constitutional symptoms.
• Extraintestinal manifestations and complications in ~ 30-40% cases (Table 10.13).
Diagnosis is supported by presence of leukocytes (usually gt;50-100#8725;hpf) and blood in stools and peripheral leukocytosis with band cells. Confirmation requires stool culture (or rectal-swab cultures) on selective media, e.g. xylose-lysine deoxycholate (XLD) and SalmonellaShigella agar. However, negative culture does not exclude shigellosis. Molecular PCR tests are available but rarely used.
• Bacterial:
Shigella
E. coli (enteroinvasive serotypes)
C.difficile (pseudomembranous enterocolitis) Others: C. jejuni, Y. enterocolitica, Salmonella
• Protozoal: E. histolytica
• CIBDs: Ulcerative colitis, Crohn's disease
CIBD: Chronic inflammatory bowel diseases
D/D of shigellosis includes other causes of infective dysentery and acute attack of chronic inflammatory bowel diseases, e.g. ulcerative colitis (Table 10.14).
Management includes: (a) fluid and electrolyte correction,
(b) antibiotic therapy, and (c) symptomatic measures.
Antibiotics of choice for shigellosis are Ciprofloxacin (PO 20-30 mg/kg/day q12hr) or Cefixime (PO 8 mg#8725; kg/day q12hr) for 5 days, while IV Ceftriaxone (50 mg#8725; kg/day OD) may be used in small infants or seriously sick patients. Azithromycin is a second-line antibiotic in non-responders.
Studies have also shown beneficial effects of single dose vitamin A (200000 IU) and zinc supplements (PO 20 mg 14 days) in recovery from shigellosis, apart from high-protein, high-caloric diet.
Most cases recover within 5-7 days and mortality is uncommon except in severe malnourished children or those with complications, e.g. severe dyselectrolytemia, DIC, renal failure and encephalopathy.
Prevention depends on: (a) prolonged breastfeeding, (b) personal hygiene, e.g. hand-washing after defecation/ before food handling and (c) proper water/sewage treatment. No vaccine is available at present.
IMNCI recommends diagnosis of dysentery in any child age 2 months-5 years with blood in stools, who should be treated with Cefixime (PO 10 mg/kg/ day q12hr) for 5 days and Tab Zinc 20 mg once a day (half tab in infants 2-6 months), with follow-up after 2 days.