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PNAS Papers on Rift Valley Fever, Malaria Vector Tracking, Circulating Extracellular MicroRNAs

Researchers from France and the UK take a look at the extent of Rift Valley fever (RVF) arbovirus spillover into human populations from the southwestern Indian Ocean island of Mayotte during an epidemic of the hemorrhagic fever from late 2018 to the fall of 2019. Using insights from 143 RT-PCR-confirmed RVF cases assessed during the epidemic — along with phylogenetic, seroprevalence, livestock, and other epidemiologic data — the team did mathematical modeling on transmission events, estimating that direct contact between humans and infected livestock led to roughly double the cases as vector transmission. On the other hand, vaccinating both humans and livestock showed promise for guarding against additional outbreaks. From these and other findings, the authors suggest that "[c]oordinated human and animal health surveillance, and timely livestock vaccination appear to be key to controlling RVF in this setting."

A University of Oxford-led team explores the potential African range of a previously unappreciated malaria vector Anopheles stephensi, an Asian mosquito species that seems particularly fond of urban environments. Along with a malaria outbreak in Djibouti City in 2012, the researchers write, the species is suspected of spreading to Ethiopia, Sudan, and other sites where it may pose a future malaria risk. With that in mind, they used spatial modeling and other data to map the range of An. stephensi mosquitoes from the mid-1980s to 2019, taking available genetic and phylogenetic considerations from prior studies into account, in an effort to predict how many urban populations might be at risk of malaria transmission from the mosquitoes. "We predict an increased [population at risk] of up to 126 million people if An. stephensiwere to occupy this predicted niche," the authors report. "If it continues its incursion into the African continent unchecked, there is a very real possibility of mass outbreaks of malaria among naïve populations in areas of vector-parasite coexistence." 

Investigators from the University of Massachusetts and the University of California, Los Angeles, report on results from a functional study of circulating, extracellular microRNAs in human blood plasma and cerebrospinal fluid samples from healthy individuals, individuals with increased intracranial pressure, or individuals with amyotrophic lateral sclerosis that were assessed with the help of Argonaut AGO2 immunoprecipitation, quantitative real-time PCR, and small RNA sequencing. "Our findings suggest that miRNAs in circulation are largely contained in functional miRISC/AGO2 complexes under normal physiological conditions," the team reports, though it notes that "in human CSF, the assortment of certain extracellular miRNAs into free miRISC/AGO2 complexes can be affected by pathological conditions such as amyotrophic lateral sclerosis."