Infectious acquired through GIT
choleraIDENTIFICATION (signs and symptoms) :
- An acute bacterial disease (enteric), - sudden onset of profuse watery stools (1L/ day), - occasional vomiting, - rapid dehydration, acidosis , - circulatory collapse.Prognosis:
* Asymptomatic infection occur much more frequently than clinical illness75% asymptomatic. 20% mild , * In severe cases (untreated) , death can happen (within few hours ) ,2-5% severe * C.F.R ≈ 50%, but with proper Rx, C.F.R. < 1%.DIAGNOSIS: - Confirmed by culturing Cholera vibrio of serotype 01 from feceas , or - significant rise in titer of antitoxic antibodies,
Infectious Agent:Group A – Vibrio cholerae Serogroup 01 (which includes)- El-TOR true - classical or : INABA, OGAWATrue cholera vibrio is demonstrated by:- - presence of specific O antigen and - no hemolysis of goat or sheep RBCs if added to suspension of these cells.
Group B – non cholera Vibrios. (Non pathogenic to man)
- Most vibrio strains elaborate enterotoxin resulting in similar clinical picture - In any single epidemic one particular type tends to be dominant (presently El Tor biotype is predominant except in Bangladesh, where the classical biotype has reappeared).
In 1992, a new serogroup – a genetic derevative of the EL TOR biotype – emerged in Bangladesh and caused an extensive epidemic. It has now spread over large parts of Asia and is termed Vibrio Cholerae o139 “ BENGAL”.
Occurrence :- During 19th century pandemic cholera repeatedly spread from India to most of the world. - During Ist half of 20th century, the disease was confined largely to Asia (except for severe epidemic in Egypt in 1947). - Since 1961, cholera spread from Indonesia to Western Europe , and AFRICA.
OCCURRENCE:-
- During 1977 and 1978 outbreaks were reported from Japan*, - In 1983; 13 African countries reported the disease, - The Western hemisphere was free from cholera between 1911 – 1973 (except for 2 lab. acquired cases)OCCURRENCE:
In 1991 cholera appeared in South America, ( it had been absent for > century ).Within a year it spread to 11 countries, and through the continent.In 1992 large outbreaks began in India & Bangladesh. “Such outbreaks was caused by a previously unrecognized serogroup” ( O139\Bengal ). It is a more virulent variant of EL TOR biotype.SIZE OF THE PROBLEM GLOBALLY: 140 000 – 290 000 cases were reported between 1997- 1998.In 1999, global incidence was about 254 000 , and Africa alone accounted for about 81% of the global total number of cases.In 2000, multiple outbreaks were reported in populations in various islands of Oceania .
Reservoir:- Man : - A patient during incubation period (faeces) - A patient during illness (faeces & vomitus) - A patient during convalescence (faeces) - Contact through faeces
Mode of Transmission:-
A. Primary ingestion of water (contaminated with faeces or vomitus of patients, or to lesser extent to faeces of carriers). OR B. Ingestion of food contaminated by dirty water, faeces, soiled hands or flies.C. Use of soiled articles (e.g. utensils, clothes and bedlinen) “to lesser extent.”Poor sanitation transmits many diseases. Each year 1.3 million children die from diarrhoeal diseases alone. Ensuring safe methods of excreta disposal, access to latrines at home and in schools, and encouraging hand washing.
INCUBATION PERIOD: Few hours – 5 days. “ The international I.P. is 5- days “.Period of Communicability: - For the duration of stool ve+ stage (usually few days after recovery) - Carrier state may persist for few months (98% non infectious by the end of 3rd week) *NOTE:Effective antibiotic eg. (tetracycline) reduce the period of communicability.
Suscept. And Resistance:-
Susceptibility is general and variableGastric achlorhydria increases the riskPeople more at risk:1- People with low gastric acid level2-Children 10X more susceptible than adult3-Elderly4-Blood type O≥B≥A≥AB
Unsanitary environment:
WHO cholera 6th report stated factors favouring endemicity in India (lower Bengal area):High density population, Increased humidity, Abundance of uncontrolled H20 supply, High salinity and organic water contents. **- An attack gives temporary immunity
METHODS OF Controls and prevention
1- Sanitary disposal of human faeces (maintenance of fly proof latrines). 2- Protect, purify and chlorinate public water supplies. (avoid cross connection with sewer system.). 3- Control flies by spraying with insectici.4- Cleanliness in preparation of food, 5- Pasteurize or boil milk , 6- Sanitary supervision of commercial milk production, storage and delivery.
7- Two available types of vaccines which provide high level of protection for several months against vibrio cholerae serotype o1. ( Of use for travellers to endemic countries, but not yet used for public health purposes ). -
8- Reporting to local health authority 9-Disinfection of articles soiled with faeces or vomits of patients (by heat, carbolic acid or other effective disinfectant 10-Specific measure during pilgrimage season.
Contacts:- - Surviellance for 5-days. - Chemoprophylaxis with tetracycline. - No immunization necessary. - Investigate contacts with source of infection. - Specific Rx:- * Prompt fluid replacement using adequate volumes of electrolytes solutions, to correct dehydration.
treatments
Rehydration therapy must begin immediately because death can occur within hours. Oral or intravenous rehydration, up 80% of cases can be treated by oral rehydration salts. Adults tetracycline, doxycycline ,cotrimoxazole and ciprofloxacine Children erythromycin, cotrimoxazole and furazolidone are the drugs of choice