Confirmation of 2006 chikungunya outbreak in Sri Lanka using RT-PCR

Abstract

Chikungunya, a mosquito-borne viral infection caused by a single-stranded RNA virus of the family Togaviridae, is considered as a rare, non-fatal disease. During February to October 2006, an epidemic of over 1.3 million suspected cases was reported in India and neighbouring countries causing a significant economic loss due to crippling manifestations of this infection. With the outbreak of many viral fevers including dengue and dengue haemorrhagic fever, in October–November 2006, patients with manifestations suggestive of chikungunya such as high fever, headache, arthralgia and arthiritis (particularly, in ankle, knee and small joints of hands) were reported in many parts of Sri Lanka. As no chikungunya cases had been officially reported in the island since 1969, laboratory investigations for the presence of chikungunya virus was a prime requirement for confirmation of the outbreak. A total of 60 venous blood samples collected from suspected patients from different geographical regions of Sri Lanka were analysed using a reverse transcriptase-polymerase chain reaction (RT-PCR) technique to confirm the presence of chikungunya virus. Viral RNA was extracted from samples collected within 1-4 days of fever by using a Qiagen RNA extraction kit. RT-PCR was performed using chikungunya specific oligonucleotides. Both positive and negative controls were included in each set of reactions. The amplified products (354 bp) were visualized by running in a 1.5% agarose gel followed by ethidium bromide staining. Of the 60 samples, 33 (55%) were positive for chikungunya. They were distributed among almost all the geographical regions, highlighting the presence of a wide-spread epidemic in the country.