Detection of asymptomatic carriers of malaria in Kohat district of Pakistan

Abstract

Background: Kohat district is one of the medium intensity malaria transmission areas in Pakistan where asymptomatic carriers are likely to form a reservoir of infection. This study was done to explore the possibility of using microscopy, rapid diagnostic testing (RDT), real time polymerase chain reaction (RT-PCR) and RT-PCR followed by endpoint fluorometry (EPF) for detection of malaria in asymptomatic immediate family members of patients of malaria (homestead) and in a sample from the general population of Kohat.

Methods: This cross-sectional study was done at Combined Military Hospital Kohat and Molecular Lab of Riphah International University, Islamabad from Jan to Dec 2015. A total of 1000 individuals including 200 microscopy positive patients of malaria, 400 asymptomatic immediate family members (homestead) of the active patients of malaria and 400 apparently healthy controls were tested by microscopy, RDT and RT-PCR. At the end of RT-PCR the result were read by EPF.

Results: In the 200 malaria microscopy positive patients, 190 (95%) were RDT positive and all were RT-PCR positive. In the 400 individuals from the homestead of malaria patients, 6 (1.5%) individuals were malaria microscopy positive while RDT failed to pick any positive and 32 (8%) were RT-PCR positive for malaria. EPF of all the RT-PCR positive results were positive and the negative results were negative. The difference in the frequency of malaria in the homestead versus general population was very significant (p = 0.0002) and the relative risk of malaria was 4.0 times higher (95% CI 1.87-8.57).

Conclusion: The chances of detecting asymptomatic malaria carriers is significantly higher in the homestead of malaria patients than in the general population and for this purpose RT-PCR with EPF can be very useful in the diagnosis of malaria especially with low parasite density.

Keywords: Asymptomatic malaria; Endpoint fluorometry; RT-PCR.

Fig. 1

Correlation between RT-PCR cycle threshold (Ct) and the corresponding EPF relative fluorescence units (RFU) in 240 samples positive for malaria