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Summary Containment Strategies - selected infectious diseases
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Containment Strategies - summary of all the selected diseases
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TrachomaA common infectious disease, trachoma is the major cause of blindness in the world.
Organism – VIRUS & BACTERIUM - Chlamydia trachomatis,
Clinical features – Commencing as a keratoconjunctivitis, the first sign is red eye. There may
be irritation and discharge, but it is passed off as a self-limiting infection. A follicular
infiltration of the conjunctiva then takes place particularly in the upper lid. Blood vessels grow
into the periphery of the eye, forming pannus. Trachoma is often complicated by secondary
infection. It is at the late stages of the disease, when it is non-infectious that scarring,
particularly of the upper eyelid, turns the eyelashes inward to rub on the eye, a condition called
trichiasis. This constant rubbing of the eyeball, aided by the dryness of the conjunctiva,
damages the cornea, leading to scarring and finally blindness.
Diagnosis – Is usually made on clinical grounds, but can be confirmed by finding the
characteristic inclusion bodies in scrapings taken from the conjunctiva.
Transmission – Trachoma is a disease of poor sanitary conditions where a combination of
close contact and dirty conditions encourages transmission. Within the family unit,
transmission is from child-to-child or by flies that are attracted to the discharges around the
eyes. These are mainly Musca sorbens. Cycles of reinfection and recrudescence continue to
damage the eye and lead to blindness at school age. The usual method of wiping away
secretions with hands, towels or clothing, which is then used by the adult on other children or
themselves, is a typical pattern of transmission.
Incubation period – 5-12 days
Period of communicability – Continues as long as active lesions are still present. Once
treatment commences, infectivity ceases within 2-3 days although the clinical disease persists.
Occurrence and distribution – Trachoma is found mainly in the dry regions of the world,
especially Africa, South America and the extensive semi-desert regions of Asia. A disease of
antiquity, it was first described by the ancient Egyptians. In endemic areas, 80-90% of children
are infected by the age of 3 years. In conditions improved sanitation, there is a natural cycle
lasting until the age of 11 years, with little residual damage. Females develop trachoma and
blindness as adults more commonly than males because they are directly concerned with
looking after children. The chance of acquiring infection is increased by large families with
short birth intervals, as there are more children of a young age living in close proximity.
Control and prevention – The use of water to wash away secretions, clean clothes and the
surrounding is perhaps the single most effective method. Washing the face often has been
shown to reduce the risk of developing trachoma so regular daily face washing should be
encouraged. Long-term preventive measures include improved sanitation and the provision of
water supplies. Flies proliferate in rubbish and excrement, reaching their maximum numbers
during the dry, sunny periods of the year. The damp, moist condition in open pit latrines may
be more important in encouraging fly breeding than non-use of latrines. Any flushing
mechanism or improved latrine will discourage flies. A strategy for a control programme is as
follows:
- Conduct a survey to find the worst-affected areas;
, - Give mass treatment;
- Conduct health education through schools, stressing regular face washing;
- Provide back-up services
WHO has launched a programme for the global elimination of trachoma by 2020 and given it
the acronym of SAFE. This stands for:
- Surgery for trichiasis;
- Antibiotics;
- Facial cleanliness;
- Environmental improvement
Treatment – Mass treatment is preferable, as the majority of the population is an infected area
will have trachoma. This is given easily in schools, but is better done at home, where the main
transmission takes place. A single dose of azithromycin (20 mg/kg) is better than topical
tetracycline and one dose a year may be sufficient to eliminate the blinding propensity of
trachoma. Mothers can be taught to regularly treat all children in the household. Preventing
blindness, once scarring and trichiasis have developed, is very easily done by a simple
operation that a Medical Assistant can be trained to do. This involves cutting through the
scarred conjunctiva of the upper lid and averting it so that the eyelashes no longer rub on the
cornea.
Surveillance – After the initial survey, follow-up surveys should be conducted at regular
intervals. This is most easily done in primary schools.
,Gastroenteritis
Organism – BACTERIUM – Escherichia coli.
Common form of diarrhoea that predominantly attack children. It is endemic in
developing countries, but seasonal epidemics occur. Attempts to find a specific organism as a
cause are often unsuccessful and not essential, as management and control are the same. Strains
of enterotoxigenic, enteropathogenic and enteroaggregative Escherichia coli as well as enteric
viruses, particularly rotavirus, are the main organisms. Campylobacter is now a major cause.
Clinical features – Profuse, watery diarrhoea with occasional vomiting, but despite the fluid
nature of the stools, faecal material is always present. There is never the rice-water stool
characteristic of cholera. Water and electrolytes are lost, which in the young child may be
sufficient to cause dehydration and ionic imbalance, leading to death. Normally, a self-limiting
condition, but in unhygienic surroundings, or where babies’ bottles are used, repeated
infections occur leading to chronic loss of nutrients and subsequent malnutrition. A serious
infection in neonates, mortality decreases with age until in adults, it is just a passing
inconvenience (travellers’ diarrhoea).
Diagnosis – Is made on clinical criteria unless laboratory facilities sufficient to identify viral
infections are available. Specific DNA probes are likely to be the most appropriate method if
identifying causative organisms in developing countries if they can be made cheap enough.
Transmission – Epidemics occur in families or groups of children sharing similar
surroundings. Infection is often seasonal, for example, the beginning of the rains heralding an
outbreak. This would suggest transmission by water and simple control measures, such as
boiling of water, can stop the epidemic. Improperly sterilized babies’ bottles or their contents
are a common method of infecting the neonate.
Incubation period – 12-72 hours (generally 48 hours)
Period of communicability – 8-10 days
Occurrence and distribution – Gastroenteritis is found throughout the world, especially in
developing countries and in conditions of poor hygiene. It is particularly common where bottle-
feeding has been recently introduced, such as by unscrupulous infant-feed companies. A
seasonal distribution suggests contamination of the water supply.
Control and prevention –
- Promotion of breast-feeding;
- Use of oral rehydration solution (ORS) in the community;
- Improvement in water supply and sanitation;
- Promoting personal and domestic hygiene;
- Vaccination (rotavirus and other vaccines, e.g. measles).
Breastfeeding not only provides a sterile milk formula in the correct proportions (in contrast to
the often-contaminated bottle), but also promotes lactobacilli and contain lactoferrins and
lysozymes. Promoting breastfeeding and the administration of ORS solution in the community
are the main control strategies. Improvement in water supplies and sanitation, with the
promotion of personal hygiene, are long-term measures. The oral cholera vaccine WC/rBS has
been shown to be about 60% effective against enterotoxigenic E. coli so might have some place
in control although its protective effect in infants is considerably less. Rotavirus vaccine (RRV-
, TV) has so far been shown to be less effective in developing countries than the developed and
several cases of intussusception has resulted in its withdrawal from use in the latter. Preventing
other childhood infections by vaccination, especially those associated with gastro-intestinal
disease, such as polio and measles, can reduce the severity of gastroenteritis.
Treatment – Is by replacement of fluid and electrolytes using ORS in the moderately
dehydrated and intravenous replacement in the severely dehydrated. A suitable ORS is made
by dissolving the following constituents in 1L of water:
- Sodium chloride (salt) 3.5 g (NA+ 90 mmol)
- Trisodium citrate dehydrate 2.9 g (citrate 10 mmol)
- Potassium chloride 1.5 g (K+ 20 mmol, CI- 88 mmol)
- Glucose anhydrous (dextrose) 20.0 g (glucose 111 mmol)
These ingredients can be obtained separately or in packets of readily prepared mixtures. In the
absence of prepared packets, a simpler formulation can be made, which consists of mixing salt
and sugar in 1L of clean water. Potassium is not an essential constituent but addition of the
juice of one orange is useful. Tea leaves also contain potassium, so the mixture can be prepared
as tea with the addition of salt and sugar. Teaspoons vary in size and it is dangerous to give too
much salt; hence a useful check is for the mother to taste the solution before administering it
to her child. If it tastes salty, then more water should be added. A naturally available
rehydration solution is the fluid from a green coconut. A 7-month coconut has been found to
be the most suitable. Rice-water made form a handful of rise boiled in a saucepan of water until
it disappears, plus the appropriate amount of salt for the volume of water, makes a simple
rehydration solution. Carrot water can also be used. If mothers are taught how to make up these
solutions, then they can treat their children as soon as they start to get diarrhoea. The mother
should use a cup and a spoon and sit with her child giving it small quantities of fluid at frequent
intervals. Severe dehydration can usually be prevented by primary care from the mother. There
is no need to use an antibiotic or an antispasmodic, both of which are contraindicated.
Lactobacilli, which inhibit E. coli, colonize the guy in the breast-fed infant. In some countries,
lactobacilli are administered in yoghurt (curd).
Surveillance – In countries with a seasonal rainfall pattern, gastro-enteritis outbreaks often
start with the beginning of the rains, so monitoring the weather can provide early warning of
an impending outbreak.
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