CHENNAI: Even as the State health department is confidently striding ahead to get Chennai declared as malaria-free by the World Health Organisation, a study done by the National Institute of Malaria Research (NCMR), Chennai along with other institutions has shown the existence of asymptomatic malaria which remains undetected.
This sub-microscopic malaria acts as a transmission reservoir in endemic areas and poses a major challenge in efforts to eliminate malaria, Dr Eapen Alex from NCMR, Chennai, the lead author of the study, told Express.
The study, ‘The sub-microscopic malaria in Chennai: The hidden parasite Reservoir’, was done by the Chennai and Delhi centres of NCMR, the research organisation of the Indian Council of Medical Research, along with the Centre for Genomics and Systems Biology, Department of Biology, New York University.
This was done to find the burden of sub-microscopic and asymptomatic malaria in the community, Dr Alex added. The findings, which are yet to be published, was presented at the 13th conference on Vector Borne Diseases in Chennai on Tuesday.
For the study, households in Besant Nagar, Chennai were randomly chosen from Census data, selecting two to four persons from each house. Individuals of age above one year and below 70 years were enrolled after getting consent. Pregnant and people with chronic illnesses were excluded.
Socio-demographics, malaria history, clinical information were obtained through a questionnaire, while blood samples were collected for microscopic and polymerase chain reaction (PCR) test, which is more sensitive than microscopy diagnosis.
The results, if validated by review, should be a wake-up call for the health department.
Of the 1,054 symptomatic patients who visited the clinic, 186 (17.6%) were tested positive by microscopy and 222 (21.1%) by PCR. During community survey conducted with a sample of 928, only 8 (0.9%) infections were found under microscopic examination while the figure was 24 (2.6%) when PCR test was done.
The community study also showed that majority of the infections were hidden even during microscopic examination but were detected by PCR.
To show actual sub-microscopic burden in the catchment area so as to address the public health risk caused by malaria, a disease that causes high morbidity and mortality, sensitive PCR detection methods should be used, the author added in the study.
The study result shows the existence of sub-microscopic infections that acts as a reservoir, said Dr Alex, pointing out that this hindered the control programmes by the authorities. Better surveillance and intervention methods targeting the infection reservoirs were needed to scale down malaria to pre-elimination level.
The researchers said that this would make the government’s plans to achieve malaria elimination by 2020, a target set by WHO, all the more challenging.