Occurrence:
* Malaria is endemic or sporadic throughout most of the tropics and subtropics below an altitude of 1500m, excluding the Mediterranean littoral, the USA and Australia.
* Following WHO-sponsored campaigns of prevention and more effective treatment, the incidence of malaria was greatly reduced in 1950-'60 but since 1970 there has been a resurgence.
* Now about 40% of the world's population is at risk of malaria. Each year there are 300-500 million clinical cases of malaria, 90% of them in Africa, of whom 1% die, mainly children.
Malaria in Bangladesh :
Malaria is hyper-endemic in the Chittagong Hill tracts area, in the border areas of Dinajpur, Kustia Mymensingh and Sylhet.
In 1970, the total malaria cases detected in Bangladesh were 8,173 from 5.9 million blood slides examined. The cases were increased steadily reaching a peak of 48,804 cases in 1976.
Further Bangladesh has been facing an upsurge of malaria incidence particularly from late 1990. In 1994 the total cases of malaria were 1,66,585.
The possible causes of the upsurge of malaria may be:
* Cross-border migration of labor force
* Steady rise of cases on both sides of the border
* Lack of adequate diagnostic and treatment facilities at the peripheral level
* Inadequate vector control measures
* Little or no epidemic forecasting system
* Change in topographic features particularly in the epidemic-prone areas.
Ecological triad:
1. Agent: There are 4 species of malaria parasites which in fact man--
* Plasmodium vivax: Benign tertian (BT) malaria
* P.ovale: Oval malaria
* P. malaria: Quartan malaria.
* P.falciparum: Malignant tertian (MT) malaria, pernicious malaria.
2. HOST
* Age --all ages are affected.
* Sex -- male>Female
* Immunity --Has no natural immunity. Infants borne of immune mothers are generally protected during the first 3-5 months by maternal antibodies.
3. ENVIRONMENT:
Rainfall is the main factor, others are temperature (20--30C, humidity (63% or more) and air movement.
* Man made malaria -- burrow pits, garden pools, irrigation channels and engineering projects have led to the breeding of mosquitoes and an increase in malaria. Low socioeconomic condition favors in occurring malaria in high rate.
Incubation period:
This is the number of days covering the time between infection and the first appearance of clinical signs (fever) incubation period of P.viva x, P. oval and P. falciparum malaria: 9 -14 days 9average 12 days)
Incubation period of P .malaria: 18 days -6 weeks.
* Preparation period:
This is the number of days between infection and the first appearance of parasites in the blood.
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