Abstract:
The present study was conducted within six month period
from January to June 1991 in some selected malarious villages in
the Kurunegala District. 82%-86% of the total population in the
chosen villages were screened for malaria parasites by several
blood surveys.An average malaria prevalence rate of 4.47% to 7.08%
was detected in the different health areas duri!lg these
surveillences.
It is generally considered, and frequently stated that the
incidence of asymptomatic malaria carriers in sri Lanka is
extremely low or insignificant because most infected individuals ,
develop the disease due to a lack of immunity. Theses assumptions
have been mainly based on observations made by Passive Case
Detection.The present study was carried out to investigate the
extent of the asymptomatic carrier states prevalent in a malaria
endemic region of shri lanka. The study reveals that of all malaria
infections detected, at least 11% are truly asymptomatic cases,
they having not experienced any symptom during a period extending
up to one month previously, while harboring parasites. At least
another 20% appear to be asymptomatic during some time of their
infections. The number of symptomatic malaria infections were
inversely proportional to the age and the number of previous
malaria attacks suggesting that their asymptomatic state was due to
the acquisition of some source of immunity.These asymptomatic
parasite carriers appear to be the contribu,tory sources of
infection for epidemic outbreaks of the malaria when environmental
conditions are favorable for high production of vector densities
