In 2005, there were outbreaks of febrile polyarthritis due to Chikungunya virus (CHIKV) in the Comoros Islands. CHIKV then spread to other islands in the Indian Ocean: La Réunion, Mauritius, Seychelles and Madagascar. These outbreaks revealed the lack of surveillance and preparedness of Madagascar and other countries. Thus, it was decided in 2007 to establish a syndrome-based surveillance network to monitor dengue-like illness.
This study aims to evaluate the use of capillary blood samples blotted on filter papers for molecular diagnosis of CHIKV infection. Venous blood samples can be difficult to obtain and the shipment of serum in appropriate temperature conditions is too costly for most developing countries.
Methodology and principal findings
Venous blood and dried-blood blotted on filter paper (DBFP) were collected during the last CHIKV outbreak in Madagascar (2010) and as part of our routine surveillance of dengue-like illness. All samples were tested by real-time RT-PCR and results with serum and DBFP samples were compared for each patient. The sensitivity and specificity of tests performed with DBFP, relative to those with venous samples (defined as 100%) were 93.1% (95% CI:[84.7–97.7]) and 94.4% (95% CI:[88.3–97.7]), respectively. The Kappa coefficient 0.87 (95% CI:[0.80–0.94]) was excellent.
This study shows that DBFP specimens can be used as a cost-effective alternative sampling method for the surveillance and monitoring of CHIKV circulation and emergence in developing countries, and probably also for other arboviruses. The loss of sensitivity is insignificant and involved a very small number of patients, all with low viral loads. Whether viruses can be isolated from dried blood spots remains to be determined.
Chikungunya is a mosquito-transmitted viral disease. No treatment is currently available. The only way to prevent infection is to avoid mosquito bites. Surveillance of circulation by early diagnosis is useful to prevent or limit outbreak. CHIKV, like all RNA viruses, is heat-labile. Consequently, confirmatory diagnosis classically requires blood samples that are transported in appropriate conditions (i.e. at 4°C within 48 hours, in liquid nitrogen, or frozen at −80°C and transported on dry ice) to prevent false negative results. This is not always possible in field conditions in low income countries. Dried blood spots are already used to diagnose parasitic, bacterial and viral infection. We compared venous sample to dried blood sample to make diagnosis of Chikungunya infection. We demonstrate the usefulness of this sampling method for the molecular diagnosis of Chikungunya infection. In particular, dried blood spots were very nearly as suitable as frozen serum specimens for the diagnosis of recent infection by CHIKV.