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Shigellosis
- 2. Table of content : Introduction Epidmiology Causative agent Clinical feature Diagnosis Treatment Prevention and control
- 3. Introduction Bacillary dysentery is an acute bacterial disease involving the large and small intestine It is caused by bacteria of the genus Shigella, of which S. dysenteriae type 1 causes the most severe disease and the largest outbreaks (other species include S. flexneri, S. sonnei and S. boydii). It is the most important cause of acute bloody diarrhoea.
- 4. epidmiology Shigellosis causes an estimated 150 million illnesses and 14,000 deathes worldwide Its endemic in both tropical & temprate climate S. dysenteriae type 1 is of particular concern in developing countries and complex emergency situations where huge outbreaks can occur. S. sonnei is most common in industrialized countries, where the disease is generally less severe
- 5. Causative agent Shigella strains are gram negative , faculatively anaerobic,non motile rods classified in the family enterobacteriacae. Shigella strains cause dysentry by invading and destroying the cells that line the large intestine There are 4 subgroups of shigella • Group A: S.dysenteriae (most severe infection due to shig toxin type 1) • Group B: S.flexneri • Group C: S.bodyii • Group D: s.sonni Group A<B<C are further subdivided into 15,8,19 serotype respectively. While group D consist of a single serotype
- 6. Mood of transmission The only significant reservoir is human Mainly by direct or indirect fecal-oral transmission from a symptomatic patient or a short-term asymptomatic carrier Infection may occur after the ingestion of contaminated food or water as well as from person to person. The infective dose can be as low as 10–100 organisms. Water and milk transmission may occur as the result of direct fecal contamination; flies can transfer organisms from latrines to uncovered food items.
- 7. Incubation period Usually 1–3 days, but may range from 12 to 96 hours; up to 1 week for S. dysenteriae 1
- 8. Clinical feature acute loose stools of small volume accompanied by fever, nausea and sometimes toxaemia, vomiting, cramps and tenesmus In typical cases, the stools contain blood and mucus (dysentery)resulting from mucosal ulcerations and confluent colonic crypt micro abscesses caused by the invasive organisms; many cases present with a watery diarrhea.
- 9. Mild and asymptomatic infections occur. illness is usually self-limited, lasting on average 4–7 days. Case fatality rate can be up to 20% even with hospitalization
- 10. Differential diagnosis Other causes of dysentry include :: • Campylobacter jejuni, • entero-invasive Escherichia coli, • Salmonella • , Entamoeba histolytica (less frequently )
- 11. Complications High risk pateints include • Children under 5 years • Severly malnourished patiens • Eldelrly over 50 years Complications include : • Sepsis • Rectal prolapse • Haemolytic uremic syndrome • Convulsions (especially among young children) Shiga bacillus is associated with • Toxic megacolon • Intestinal peroration • HUS
- 12. Period of communicability During acute infection and until the infectious agent is no longer present in feces, usually within 4 weeks after illness. Asymptomatic carriers may transmit infection; rarely, the carrier state may persist for months or longer. Appropriate antimicrobial treatment usually reduces duration of carriage to a few days.
- 13. Diagnosis Isolation of shigella from feces or rectal swabs provide bacteriological diagnosi Blood is observed in a fresh stool specimen Stool speciment should be processed rapidly because Shigella remains viable only for a short period outside human body Infection is usually associated with large numbers of fecal leukocytes detected through microscopical examination of stool mucus stained with methylene blue or Gram.
- 14. Isolated specimen should be tested for antimicrobial suseptiablity No rapid diagnostic test or antigen assays are avaliable yet
- 15. Case mangment Refer seriously ill or severely malnourished patients to hospital immediately. Check the results of antimicrobial sensitivity tests with the laboratory. Give an antimicrobial effective against local S. dysenteriae type 1 (Sd1)strains promptly to all patients, preferably as inpatients Treat dehydration with oral rehydration salts or intravenous fluids if severe. If the antimicrobials used are effective, clinical improvement should be noted within 48 hours.
- 16. Children < 6 mo. Less likely to get infected as breast feeding is protective
- 17. Azithromycin and ceftrixone may also be considered for treatment of shigellosis especially in children The use of antimotility agents is discourged as they prolong the duration of illness
- 18. Mangment of contacts Whenever feasible ill contacts should be discouraged from handling food ,caring of children and patients .. Until diareah stop and stool culutre is negative in one or more succesive test taken 24 hours apart and 48 hours after discontinuation of antibiotics Thourogh hand washing after defecation, before food handling and caring of children patients is essential Investigate water and food sources and recreational water sources using general sanitation measures
- 19. Prevention and control Health education regarding hand washing and sanitary measures No prophylaxis No vaccination
- 20. Specail considerations Reporting : case report to health authoraties is obligatory Common source water and foood borne outbreak require prompt investigaiton & intervention whaterever the infecting species Shiga bacillus is a potential problem is disaster situation where personal hygeine and enviromental sanitaion is defiecient
- 22. Refences Who manual Control of communicable diseases manual 18th edition Control of communicable diseases manual 20th edition Communicable disease control manula 2012 ,ministry of health,newzeland