A model to assess the accuracy of detecting arboviruses in mosquito pools

Abstract

Vigilant surveillance of virus prevalence in mosquitoes is essential for risk assessment and outbreak prediction. Accurate virus detection methods are essential for arbovirus surveillance. We have developed a model to estimate the probability of accurately detecting a virus-positive mosquito from pooled field collections using standard molecular techniques. We discuss several factors influencing the probability of virus detection, including the number of virions in the sample, the total sample volume, and the portion of the sample volume that is being tested. Our model determines the probability of obtaining at least 1 virion in the sample that is tested. The model also determines the optimal sample volume that is required in any test to ensure a desired probability of virus detection is achieved, and can be used to support the accuracy of current tests or to optimize existing techniques.

Fig. 1

Probability of obtaining at least 1 virion from a 1-ml sample, with aliquots of 25 μl, 10 μl, and 2 μl. For testing methods such as reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR (qRT-PCR) that are able to detect a single virion, this equals the probability of detection. As the concentration of virions increases (increased titer in the original sample), the probability of virus detection increases and reaches almost a 100% probability of obtaining at least 1 virion from the original sample.

Fig. 2

The required aliquot volume from a 1-ml sample for an 85%, 90%, or 95% detection probability at varying viral densities using either reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR (qRT-PCR) (which can detect a single virion). To detect virus from a 1-ml sample that has a titer of 1 log virions/ml with 90% probability, an aliquot of 200 μl is required. This model shows how to determine a minimum aliquot volume for virus detection for any desired probability of detection. The lines approach but never reach the x-axis, indicating that as titer in the infected sample increases, the required aliquot volume decreases.