Cholera Notes

–       Cholera is a water-borne disease caused by a bacterium.

–       It often appears in a population following a natural disaster, such as a major earthquake or flood.

–       Cholera is caused by a bacterium called Vibrio cholerae.

 

Signs and symptoms of cholera

Common symptoms of cholera and the dehydration it causes include:

–       watery, pale-colored diarrhea, often in large amounts.

–       nausea and vomiting.

–       cramps, particularly in the abdomen and legs.

–       irritability, lack of energy, or unusual sleepiness.

–       glassy or sunken eyes.

–       dry mouth and extreme thirst.

–       dry, shriveled skin.

 

Transmission of cholera

Describe how cholera can be spread from one person to another/ Explain how cholera is transmitted from one person to another through water supply/

Describe and explain the ways through which cholera is transmitted

–       food and waterborne disease;

–       due to lack of proper sanitation/poor hygiene by infected person;

–       feaces from infected person;

–       contains Vibrio cholerae, the causative agent;

–       contaminate water supply/water borne;

–       water used to irrigate crops;

–       sewage and water supply not separated / human faeces (sewage)

–       contaminates water supply;

–       person drinks water / eats food / swims in contaminated water / AW

–       transmitted to uninfected person;

–       via contaminated water;

–       e.g. vegetables irrigated with raw sewage;

–       pass out (of infected person) in feaces/(bacteria) leave person in faeces;

–       infected people handle food/cooking utensils without washing hands;

 

Global distribution of cholera

–       Cholera is now almost unknown in the developed world but can still cause large numbers of deaths in less developed countries.

Outline the reasons why cholera is more likely to spread in less developed countries.

–       lack of education/knowledge of hygiene;

–       poor sanitation;

–       lack of sewage treatment;

–       raw sewage used to irrigate/fertilise crops;

–       lack of water treatment;

–       unable to control outbreaks due to lack of rehydration treatments;

–       natural disasters;

–       poor economy;

–       civil unrest/migrants;

Reasons why cholera does not show the same global distribution as malaria

–       malaria is transmitted by, mosquito / Anopheles / vector;

–       distribution is determined by mosquito which lives in, tropics / subtropics /described; ora

–       malaria not dependent on poor, hygiene / sanitation;

–       cholera transmitted via water or food;

–       sickle trait / genetic factors, influence distribution of malaria;  –     ref to natural disasters / manmade disasters;

 

Why infants who are breast fed rarely suffer from cholera

–       breast milk is sterile / idea;

–       infants do not drink (contaminated) water / drink milk;

–       passive immunity;

–       milk may contain antibodies (to cholera);

–       antibodies provide protection for infant;

 

Measures to control the spread of cholera

• piped water;
• ensure that water supply is separate from sewage;
•   hygienic, removal / disposal, of faeces; A ‗human waste‘ / sewage treatment
• encourage breast feeding;
• treat people with cholera / provide ORT / provide antibiotics / provide trained
• medical personnel / medical facilities / access to medical facilities;
• boiled drinking water / sterilized water / chlorinated water;
• make sure people, eat cooked food / avoid raw food;
• AVP;; e.g. ref to education, vaccination, contact tracing, cordon sanitaire, ref to flies

 

Role of economic factors in the prevention and control of cholera

• waterborne disease;
• caused when water is infected by feaces from carrier/sufferer;
• important to purify water;
• important to have proper sewage treatment;
• developing countries often cannot afford the required measures;
• partly because they have large debts;
• education needed about importance of hygiene + economic link;
• cost money to train teachers/run advertising campaigns/build schools;
• locate and isolate carriers/sufferers;
• cost  money to build hospitals/isolation wards/trace contacts/train staff/pay nurses;
• (economic) aid available in form of oral rehydration packs for treatment;
• cheap and effective;
• from international aid e.g. Red Cross;
• antibiotics can cure but often too expensive;
• little incentive for drug companies to develop cured because developing countries cannot afford them;

 

Explain why it has been proved difficult to develop a vaccine to control the spread of cholera

• V. cholerae in intestine;
• out of reach of immune system;
• antigenic concealment;
• antibodies broken down in intestine;
• antibodies are proteins;
• ref to pH and effect on structure or shape; e.g. in the stomach
• denaturation;
• vaccine stimulates antibodies in, blood / lymph;
• not in gut;
• oral vaccine needed;
• mutation;
• different strain idea;
• AVP; e.g. not required in developed countries
• developing countries cannot afford to develop vaccines
• cholera can be treated with ORT
• can be treated with antibiotics