Cholera

Cholera A life-threatening secretory diarrhea induced by enterotoxin secreted by V. cholerae ( non-invasive) Water-borne illness caused by ingesting water/food contaminated by copepods infected by V. cholerae A major epidemic disease

V. cholerae Transmitted by fecal-oral route Endemic in areas of poor sanitation (India and Bangladesh ) May persist in shellfish or plankton 7 pandemics since 1817 – first 6 from Classical strains, 7th from El Tor

Cholera is not transmissible person-to-person, but can easily be spread through contaminated food and water

People Most at Risk People with low gastric acid levels Blood types Children: 10x more susceptible than adults Elderly Blood types O>> B > A > AB Not sure why O more susceptible—allows bacteria to adhere to gut lining—guess a)e1tor and 0139—cholera gravis—mostly O blood type endemic regions a)bangladesh—low attack rates in adults b) Antibodies– resistance--- intestinal IgA prevent attachment to mucosal surface, neutralize cholera toxin b)Cmmon in children

Incubation Period Ranging from a few hours to 5 days Most cases presenting within 1-3 days As expected for organisms passing through the gastric barrier, the incubation period is shortest when: highest dose of ingested organsim High gastric pH Infectious dose ranges from 106_ 1011 colonizing units

Symptoms Usually mild, or no symptoms at all Cramps Occur 2-3 days after consumption of contaminated food/water Usually mild, or no symptoms at all 75% asymptomatic 20% mild disease 2-5% severe Vomiting Cramps Watery diarrhea (1L/hour) Without treatment, death in 18 hours-several days 1)No fever—not invasive 2) clever-viable even after exit body—take host’s liquid

Cholera Gravis More severe symptoms Rapid loss of body fluids 6 liters/hour 107 vibrios/mL Rapidly lose more than 10% of bodyweight Dehydration and shock Death can occur within 2-3 hours

Consequences of Severe Dehydration Intravascular volume depletion Severe metabolic acidosis Hypokalemia Cardiac and renal failure Sunken eyes, decreased skin turgor Almost no urine production 1)Fluid and electrolyte loss 2)Hypokalemia—low levels of K+ in blood a)necessary for proper nerve, muscle, heart function b)cramping, cardiac arrest 2)why sunken eyes? 3)Phosphates move out of cells

Mortality In untreated patients, mortality can reach 50-70% Risk much higher in children 10x greater than adults As well as pregnant women 50% risk of fetal death in 3rd trimester Patients can die within 2-3 hours of first sign of illness also seen from 10 hours- several days

Diagnosis No clinical manifestations help distinguish cholera from other causes of severe diarrhea: Enterotoxigenic e. coli Viral gastroenteritis Bacterial food poisoning Look up those diseases

Laboratory Diagnosis Made through isolation of bacteria from stool samples Specimens are collected Gram Stain show sheets of curved Gram negative rods Untreated patients have 106 to 108 organisms / mL of stool Important to start treatment before the cause of infection is identified: death can occur within hours

Labroratory Diagnosis Cont. Vibrios often detected by dark field microscopy of stool Organisms are motile, appearing like “shooting stars” When plated on sucrose dishes, yellow colonies appear confirming cholera Additional methods of detection include PCR and monoclonal antibody-based stool tests.

Treatment Three options prove most effective: Oral Rehydration Intravenous Rehydration Antimicrobial Therapy

Treatment: Oral Rehydration Salts (ORS) Reduces mortality from over 50% to less than 1% 1)Sodium transport coupled to glucose transport in small intestine a)glucose accelerates absorption of glucose and water 2)Glucose Enables small intestine to absorb fluids and salts more efficiently 3)Boil water for at least 10 minutes 4)Bicarbonate—corrects acidosis 5)Sports drinks a)excess sugar—worsen condition bc of osmolosis

O.R.S. The WHO recommends a solution containing: Per liter of water 3.5 g NaCl 2.9 g trisodium citrate/ NaHCO3 1.5 g KCl 20 g glucose or 40 g sucrose Per liter of water Min. of 1.5 x the stool volume losses should be administered Commercially sold over-the-counter

Intravenous Rehydration Used in patients who lost more than 10% of body weight from diarrhea or are unable to drink due to vomiting Ringer’s Lactate is usually used in hospitals.

Intravenous Rehydration – Additional Options Saline can be used, however bicarbonate and potassium losses are not being replaced

Antimicrobial Therapy Seen as an adjunct to appropriate rehydration Reduce the volume of diarrhea by a half and the duration of excretion to about 1 day, therefore, they lower the expense of treatment and play a role in cholera control. Due to short duration of illness, antibiotics not highly recommended

Dosage – Antibiotic Agents Given orally when vomiting stops. Tetracycline is the standard treatment Administered in single dose primarily to prevent spread of secondary infection WHO guidelines

Prevention V. Cholerae is spread through contaminated food and water, therefore, prevention depends upon the interruption of fecal-oral transmission Antibiotic prophylaxis, vaccines and surveillance of new cases are the answer to preventing the spread of disease.

Antibiotic prophylaxis The WHO recommends prophylaxis if 1 household member in a family becomes ill. Mass administration of antibiotics to a whole community is not effective nor recommended

Vaccines Two types : Killed-whole-cell formulation: Provides immunity to only 50% of adult victims and to less than 25% of children Live-attenuated vaccine, genetically- engineered Provides >90% protection against classical biovar and 65-80% against El-Tor biovar.

Traveling Precautions Boil or treat water with chlorine or iodine No ice Cook everything Rule of thumb: “Boil it, cook it, peel it, or forget it.” Wash hands frequently