Natural infection confers some amount of immunity but it is present only for 6-12 months and reinfections are seen after this period.

Immunization with killed vaccines induces only anti bacterial immunity.

Purified somatic antigens are used as vaccines, short lived and protect against infection.

Immunity may be local in the intestine, or systemic.

The prevention requires certain general measures such as - protected water supply - proper disposal of sewage - improvement of envinormental sanitation Specific measures -originally the vaccines are live suspensions

of vibrios as they gave rise to adverse reactions they were replaced by killed vaccines.

ACTIVE IMMUNIZATION Killed parenteral vaccine - Widely used for active immunization. - Two injections are given

intramuscularly at an Interval of four weeks. - Duration of protection is only 3-6

months. - A single dose confers good

protection in adult due to its action as a booster on prior

to natural immunization - In children below five years single

dose is in effective.

- There is a good cross protection between classical and El Tor vibros.

- Aluminum hydroxide and phosphate adjuvant vaccines produce better immunity, particularly in young children.

- cholera toxoid vaccine has been tried but they are not successful.

- The degree of protection is 50- 60%.

KILLED ORAL VACCINE - B.sub unit whole cell vaccine. - The vaccine contains cholera toxin B

sub unit, heat killed classical vibrio and formalin killed El Tor vibrio.

- Degree of protection was 85% for one year and 60% for two years.

- This vaccine also conferred significant protection against diarrhea due to Esch.coli.

LIVE ORAL VACCINES - Recombinant DNA vaccine with

expression of v. cholera in attenuated strain Ty21a of salmonella typhi has been developed .

- This vaccine colonises peyer’s patches and induces IgA response by local immunity.

CHEMO PROPHYLAXIS Anti microbial drugs are useful.

- It consists of the prompt and adequate replacement of lost fluid and electrolytes.

- Oral administration of fluid containing glucose and electrolytes, either alone or supplemented by intravenous fluid is successful method of treating cholera.

- Anti bacterial therapy is of secondary importance.

- Oral tetracycline was recommended for reducing the period of vibrio excretion and need for parenteral fluids

They cannot grow in the media lacking sodium chloride.

Their natural habit is sea water and marine life.

Some halophilic vibrios which cause human diseases are -:

>V.parahaemolyticus >V.alginolyticus >V.vulnificus

It is the causative agent of food poisoning due to consumption of sea food.

It produces peritrichous flagella when grown on solid media but polar flagella are formed in liquid media.

It can tolerate sodium chloride concentration up to 8%.

It is killed at 60*c in 15 mins. It cant grow at 4*c but can survive freezing. Drying destroys it.

All strains are not pathogenic for man.Strains isolated from environmental

sources are nearly always non-haemolytic when grown on a high salt blood agar, while strains isolated from human cases are almost always haemolytic. This is called kanagawa phenomenon.

Abdominal pain , diarrhoea , vomiting , and moderate degree of dehydration are the dominant features.

Recovery occurs with in 3 days.

It is frequently found in sea fish its role in human lesion is uncertain.

It has higher salt tolerance up to 10%.

It has a property to swarm on the surface of non-selective media.

It has been incriminated in marine wound infection.

It has less salt tolerance less than 8% .

It may cause wound infection and cellulitis following exposure of wounds to sea water.

Following ingestion of under cooked or raw sea food, it penetrates the gut mucosa without causing gastrointestinal manifestations and enter in to the blood leading to septicaemia with high mortality.