A Case report of dengue and chikungunya co-infection in Sri Lanka

Abstract

Dengue fever and chikungunya are arboviral diseases transmitted by Aedes mosquitoes. Though dengue has been an important communicable disease in Sri Lanka for many years, chikungunya has not been reported in Sri Lanka since late 1960s. However, in November 2006, an outbreak suggestive of chikungunya erupted in the country. We report here the first laboratory confirmed case of dengue and chikungunya co-infection in Sri Lanka. The objective is to confirm the co-infection of dengue and chikungunya in a clinical case reported in November 2006. Clinical history of high fever, severe headache, nausea, loss of appetite, severe arthralgia and mild oedema of knees, small joints of hands and feet for 3 days suggested the possibility of dengue and chikungunya in a 70 year old male. There was no skin rash or bleeding manifestations. Laboratory investigations performed included total white blood corpuscle count/differential count (WBC/DC), platelet count (PLT), serum, haemoglobin (Hb%) and packed cell volume levels (PCV). Reverse Transcription- Polyrnerase Chain Reaction (RT-PCR) technology was used to confirm the presence of either dengue or chikungunya. Viral RNA was extracted from serum samples collected during the first five days of infection using QiAmp Viral RNA Kits and amplified products were visualized by 2% agarose gel electrophoresis and ethidium bromide staining. WBC/DC analysis showed a leucopaenia (WBC count 3.04 x 103 per μl) with relative lymphocytosis (51.0%). The total PLT was 115 x 103 per μl. Hb% was 14.3 g/dl with a PCV of 43.8%. The presence of both infections was confirmed by RT-PCR which amplified 225 bp and 354 bp products for dengue and chikungunya respectively. This was the first laboratory confirmed case of dengue and chikungunya co-infection, which was also the first confirmed report of chikungunya since 1969 in Sri Lanka. As clinical and biochemical manifestations of this patient suggested the probability of a mixed infection of dengue and chikungunya, the confirmation was achieved by a RT-PCR assay. This report highlights the importance of using molecular assays to confirm mixed viral infections during their early stages, especially infections such as dengue which can result in fatal complications.