Cholera
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1- identification: an acute bacterial eneric disease characterized by in its severe form by sudden onset, profuse painless watery stool, nausea & vomiting early in the course of illness & in untreated cases rapid dehydration, acidosis, circulatory collapse, hypoglycemia in children & renal failure.
Asymptomatic infection is much more frequent than clinical illness, especially with organisms of the EI Tor biotype, mild cases with only diarrhea are common particularly among children.
In sever untreated cases death may occur within few hours, & the case fatality rate may exceed 50% , with proper treatment the rate is less 1%.
Diagnosis: by isolation vibrio cholera of a sero group O1 or O139 from feces. In non endemic area isolated organism from initial cases should be confirmed by appropriate biochemical & serological reaction & by testing the organism for cholera toxin production or for the presence cholera toxin gene. In epidemic, once laboratory confirmation & antibiotic sensitivity have been established, all cases need not be laboratory confirmed.
2- infectious agent: vibrio cholerae sero group O1 includes 2 biotypes ( classical & EI Tor) . V. cholerae O139 also cases typical cholera. The clinical pictures of illness caused by V.cholerae O1 of either biotype & O139 are similar because an almost identical entero toxin is elaborated by these organism.
3-resorviour : human & recently environmental reservoir exist.
4- mode of transmission: this occur through:
**ingestion of food or water contaminated directly or indirectly with feces or vomitus of infected person.
EI Tor & O139 organisms can persist in water for long periods.
**contaminated surface water & unsafe domestic water storage methods resulting in extensive water borne transmission of cholera
**vegetable & fruits freshened with untreated sewage water have also as a vehicle of transmission. Out breaks or epidemics as well as sporadic cases are often attributed to raw or under cocked sea foods.
4- incubation period: from a few hours to 5 days, usually 2-3 days.
5- period of communicability: as long as stools are positive, usually only a few days after recovery. Occasionally the carrier state may persist for several months.
6- susceptibility & resistance:
*gastric acidity (lower the gastric PH, lower susceptibility
* lower socioeconomic status: higher incidence.
*migration: increased population movement & international travel
*immunity: more immunity with natural infections.
*age: affects all ages. Attack rate is highest among children
*sex: affect both sex
7- methods of control:
A- preventive measures:
1- health education to public regarding the importance of hand washing after defecation & before eating or serving & carrying food for food handler & attendants.
2- dispose of human feces in a sanitary matter & maintain fly proof latrines
3- protect, purify & chlorinate public water supply.
4- control flies by screening, spraying with insecticide & use of insecticidal baits & traps
5- cleanliness in food preparation & handling, refrigerate as appropriate. Particular attention should be directed to the proper storage of salads & other foods served cold.
6- pasteurize or boil all milk & diary products.
7- enforced suitable quality-control procedures in industries that prepare food & drink for human consumption.
8- active immunization with current killed whole cell vaccine given parentally is of little practical value in endemic control or management of contacts to cases. These vaccine shown to provide partial protection (50%) of short duration (3-6 months) in highly endemic areas & do not prevent asymptomatic infection, they are not recommended.
Two oral vaccine that provide significant protection for several months against cholera caused by O1 strain
9- measures that inhibit or otherwise compromise the movement of people, foods or other goods are not justified.
B- control of patients, contact & immediate environment:
1- report to local health authority: obligatory (within 24 hours)
2- isolation: hospitalization with enteric precaution for severely ill patients. Fly control should be practiced
3- concurrent disinfection: of feces & vomitus & of linens & articles use by patients , by heat or other disinfectant.
4- quarantine: none
5- management of contact: tetracycline(500 mg four times daily) or doxycyclin (a single daily dose of 300 mg for 3 days).
6- investigation of contact & source of infection: investigate possibilities of infection from polluted drinking water& contaminated food. Meal history for the 5 days prior to onset should be interviewed
7- a search by stool culture for unreported cases is recommended only among household members or those exposed to possible common source in a previously an infected area.
8- specific treatment
a- aggressive rehydration therapy
b- give effective antibiotic
c- treatment of complication
C- epidemic measures:
1- educate the population at risk concerning the need to seek appropriate treatment without delay
2- provide effective treatment facilities
3- adopt emergency measures to ensure a save water supply. Chlorinate public water supply, even if the source water appears to be uncontaminated. Chlorinate or boil water used for drinking, cocking & washing dishes & food container unless the water supply is adequately chlorinated & subsequently protected from contamination
4- ensure careful preparation & supervision of food & drink.
After cocking or boiling , protect against contamination by flies & unsanitary handling
5- investigation designed to find the vehicle & circumstances (time, place, person) of transmission, & plan control measure accordingly
6- save facilities for sewage disposal
7- parenteral whole cell vaccine is not recommended.