TROPICAL
INSECT - BORNE INFECTIONS
Malaria
Malaria in Cambodia is endemic in all forested
areas, and a few seaside regions, but is not present in Phnom Penh,
nor in most towns, because of the absence of the vector mosquito
Anopheles dirus which bites at night. Because the flight range of
Anopheles is less than a mile, malarial areas are extremely focal,
so local advice is often more helpful than that given back home.
Non drug measures to prevent malaria are very important; use bed
nets, preferably impregnated with synthetic pyrethroid insecticide,
wear light coloured clothing which covers arms, legs, ankles and
feet, using insect repellant on exposed skin, burn mosquito coils
or use knock down insecticide spray, and sleep in an air conditioned
room or directly under a fan. Avoid perfumes that not surprisingly
attract the female mosquito. As most people can be expected to follow
these measures rigidly for up to 2 weeks, prophylactic anti malarial
drugs are not recommended for visitors staying less than 2 weeks
in a malaria zone.
The most important advice after prevention is awareness.
Any fever occurring more than 7 days after leaving a malaria area,
regardless of whether an anti-malarial drug has been taken or not,
could be malaria. A high fever of more than 48 hours should prompt
a blood test for malaria; the risk of death rises considerably if
treatment is delayed after the fourth day.
Dengue Fever
Dengue fever is common in urban areas of Cambodia
and therefore foreign tourists are at risk. It is transmitted by
Aedes aegypti, a mosquito which bites during the day and early evening.
As the vector larvae live in the water containers (jars, flower
pots) around houses, water in those should be emptied at least once
a week. Peak incidence is in the rainy season. Symptoms include
severe headache, muscle pains, and rashes. Dengue haemorrhagic fever
rarely develops in the foreigner.
Japanese encephalitis
This is an infection of the central nervous system
caused by a virus transmitted to man through the evening bite of
a mosquito that lives in rice fields. Pigs are the normal host,
but when the population of mosquitoes is high, as in the rainy season,
epidemics in humans can occur. This disease is generally regarded
as rural, and the risk factor is approximately 1 to 1.5 per 1000
to 5000 - with children most at risk. The majority of people bitten
and infected never develop any illness; it is estimated that for
every 100 persons infected, only one will develop overt disease;
however this person has a high risk of dying or being left with
permanent brain damage. 30,000 – 50,000 cases are reported
in Asia every year of which 30% die.
Scrub typhus / Flea –
borne typhus
Rickettsial infection spread by a mite of chigger,
or flea; primarily a disease of wild rats, present in scrub or grasslands.
Doxycycline, taken for malaria prophylaxis, also prevents typhus.
Plague
Very rare now; limited to small isolated areas.
Disease transmitted by the rat flea.
|
