Development of a Digital Droplet Polymerase Chain Reaction (ddPCR) assay to detect Leishmania DNA in samples from Cutaneous Leishmaniasis patients.

AIM: Here, we evaluate the ddPCR platform using an evaluated qPCR-based diagnostic assay for the detection of Leishmania infection in Cutaneous Leishmaniasis patients.
METHODS: A standard curve of cultured Leishmania parasite material and clinical samples of CL patients were tested with ddPCR to determine the analytical and diagnostic performance.
RESULTS: The limit of detection of the assay on the ddPCR platform was much higher than the published limit of detection of the same assay on the qPCR platform (100 vs 1 parasites/mL, respectively).
CONCLUSION: While the performance of this assay in ddPCR format was acceptable for research purposes, it is not sufficient for clinical diagnostic purposes. The assay is more suited to the qPCR platform.

Purpose: Middle East Respiratory Syndrome Coronavirus (MERS-CoV) remains an emerging disease threat, with regular reports of human cases on the Arabian Peninsula, driven by recurring camel-to-human transmission events. A prophylactic vaccine under development has been found to greatly reduce shedding in dromedaries, but there are major gaps in our quantitative understanding of the epidemiology of MERS-CoV in dromedary populations. The purpose of our work is to develop a mathematical model of MERS-CoV transmission in camels in order to address these gaps and to eventually inform the development of evidence-based animal vaccination strategies.

Methods & Materials: After reviewing publicly available data on camel demography and epidemiology of MERS-CoV in camels, we developed a stochastic, age-structured mathematical model of MERS-CoV transmission in single homogenous camel populations, and between coupled sub-populations.

Results: We show that if immunity is completely protective against future infection, a basic reproduction number (R 0) of 6 reproduces reported patterns of age-stratified seroprevalence observed in camel populations sampled in the Arabian Peninsula and North Africa. If immunity offers only partial protection, we estimate that R 0 is approximately 3. In large modelled populations where transmission persists long-term, epidemics are predicted to have an annual periodicity driven by seasonal births. Allowing reinfection (due to partial immunity) enhances persistence but disease extinction by chance is still expected in well-mixed populations of less than 1000 animals. Hence, we predict that single herds are unlikely to be able to sustain MERS-CoV transmission. Using a meta-population model of multiple coupled small populations, we show that transmission can persist in the population as a whole due to random reintroduction of virus into populations in which transmission has previously ceased via animal movements.

Conclusion: We conclude that the R 0 of MERS-CoV in camels is in the range 3-6, indicating moderate transmissibility. A meta-population model of MERS-CoV transmission reproduces the long-term persistence of MERS-CoV in camel populations in Africa and the Arabian Peninsula and may be useful for simulating camel vaccination strategies.