Cholera
caused by Vibrio cholerae serotype O1, El Tor is more resistant than
classical Vibrio and causes carriage in 5% of infections, A new classical
toxigenic strain, serotype O139, established itself in Bangladesh in 1992.
Infection spreads via the stools or vomit of symptomatic patients or of the
much larger number of subclinical cases, It survives for up to 2 weeks in
fresh water and 8 weeks in salt water.
Transmission is normally through infected drinking water, shellfish and food
contaminated by flies, or on the hands of carriers.
Clinical features
Painless diarrhoea followed by vomiting begins suddenly.
Following the evacuation of normal gut faecal contents, typical ‘rice water’
material is passed, consisting of clear fluid with flecks of mucus.
Classical cholera produces enormous loss of fluid (H
2
O) and electrolytes
(Cl), leading to intense dehydration with muscular cramps, Shock and
oliguria develop but mental clarity remains.
Death from acute circulatory failure may occur rapidly unless fluid and
electrolytes are replaced, Improvement is rapid with proper treatment.
The majority of infections, however, cause mild illness with slight diarrhoea.
Occasionally intense illness ‘cholera sicca’ occurs with loss of fluid into
dilated bowel, killing the patient before typical gastrointestinal symptoms
appear. The disease is more dangerous in children.
Clinical diagnosis is easy during an epidemic. Otherwise, the diagnosis
should be confirmed bacteriologically. Stool dark-field microscopy shows
the typical ‘shooting star’ motility of V. cholera, Rectal swab or stool
cultures help in diagnosis.
Management
Maintenance of circulation by replacement of water and electrolytes is the
most important.
clinical assessment of dehydration is made from appearance of patient, Oral
rehydration solution (ORS) is effective and safe for all patients especially
severly dehydrated one.
The addition of resistant starch to ORS reduces fluid loss, shortens the
duration of diarrea, this is by increasing sodium absorption in the colon.
Ringer-Lactate is the best fluid for I.V replacement. Vomiting usually stops
once the patient is rehydrated, and fluid should then be given orally up to
500 mL hourly.
The fluid required is calculated every
8
hours from urine volume stool and
vomit output and estimated insensible less as much as 5 liters / 24hr in hot
humid climate.
Total fluid requirements may exceed 50 L over a period of 2–5 days.
Accurate records can be greatly facilitated by the use of a ‘cholera cot’.
children require careful attention to fluid balance, they are prone to
hypoglycemia.
Three days treatment with tetracycline 250 mg 6 hours.
a single dose of doxycycline 300 mg or ciprofloxacin 1 g in adults reduces
the duration of excretion of V. cholerae and the total volume of fluid needed
for replacement.
Prevention
Strict personal hygiene, drinking water should come from a clean piped
supply or be boiled, Flies must be denied access to food, Parenteral or oraly
vaccinated provide limited protection, In epidemics Mass single-dose
vaccination and treatment with tetracycline are valuable. Disinfection of
discharges of patient reduce the danger of spread.
Strongyloidiasis
Strongyloides stercoralis is a very small nematode (2 mm-0.4 mm) which
parasitises the mucosa of the upper part of the small intestine, often in large
numbers, causing persistent eosinophilia. The eggs hatch in the bowel but
only larvae are passed in the faeces. In moist soil, they moult and become
the infective filariform larvae. After penetrating human skin, they undergo a
development cycle similar to that of hookworms, but the female worms
burrow into the intestinal mucosa and submucosa. Some larvae in the
intestine may develop into filariform larvae, which may then penetrate the
mucosa or the perianal skin and lead to autoinfection and persistent
infection. Strongyloidiasis occurs in the tropics and subtropics, and is
especially prevalent in the Far East.
Pathology
In the intestine the female worms burrow into the mucosa and submucosa
and induce inflammatory reaction, with heavy infection the mucosa may be
severely damaged leading to malabsorption, granulomatous changes,
necrosis and even perforation and peritonintis may occur.
eosinophilia commonly persist.
Immune suppression may cause fatal systemic strongyloidiasis.
Clinical features
The classic triad of symptoms
consists of abdominal pain, diarrhoea and urticaria.
Cutaneous manifestations are characteristic and occur in 66% of
patients. either urticaria or larva
currens (transient itchy linear urticarial weall across the abdomen and
buttock due to acute infection)
Systemic strongyloidiasis with dissemination of larvae throughout the body,
occurs in association with immune suppression ex. steroid treatment, HIV
and HTLV-1 infection.
Patients present with generalised abdominal pain, abdominal distension and
shock. Massive larval invasion of the lungs causes cough, wheeze and
dyspnoea; cerebral involvement causes confusion, seizure, coma.
Gram-negative sepsis frequently
complicates the picture.
Investigation
faeces should be examined for larvae; excretion is intermittent and so
frequent stool examinations is necessary, jejunal aspirate for larvae,
serology by ELISA is helpful, Larvae may also be cultured from faeces.
Management
ivermectin (200 µg/kg) single dose or 2 doses on successive days
albendazole is given orally 15 mg/kg every 12 hours for 3 days, A second
course may be required.
For the Strongyloides hyperinfection syndrome, ivermectin is given at 200
µg/kg on day 1, 2, 15 and 16.