Detection & molecular confirmation of a focus of Plasmodium malariae in Arunachal Pradesh, India.

BACKGROUND & OBJECTIVE During a malaria epidemiological study in Arunachal Pradesh, Plasmodium malariae like human malaria parasites were seen in blood smears from fever cases. The study was undertaken to detect the presence of P. malariae and to confirm its identity through DNA based polymerase chain reaction approach. METHODS Fever survey was carried out in 22 villages in Indo-Myanmar bordering district of Lohit, Arunachal Pradesh in 2005. Morphologically suspected P. malariae cases were confirmed using nested PCR based on 18S small subunit ribosomal DNA gene sequence. RESULTS Screening of 1,995 fever cases resulted in 9 probable cases of P. malariae based on morphological identification in Chakma tribe people residing in 2 villages. Nested PCR confirmed the identity of all probable cases of P. malariae by producing diagnostic band of 144 bp. PCR method was able to detect mixed infection of P. malariae with P. vivax and with P. falciparum. INTERPRETATION & CONCLUSION P. malariae may have been present in Arunachal Pradesh but most probably is being misdiagnosed due to its close resemblance with P. vivax, especially in ring forms. Estimation of actual case load of P. malariae in north-east India is, therefore, important with accurate species identification using molecular methods.