Zika Scan for Nov 07, 2017

Zika and 2nd mosquito feeding
Wolbachia mosquitoes OK'd
Chikungunya replacing Zika

Data from meeting indicate 2nd mosquito feeding key to Zika spread

The proportion of Zika virus–carrying Aedes albopictus and Aedes aegypti mosquitoes capable of transmitting the virus increased dramatically after a second blood meal, according to data presented today at the 66th annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH).

US researchers fed both Ae albopictus and Ae aegypti mosquitoes blood containing the Zika virus and then fed them virus-free blood 2 days later.

"We found that if you gave these mosquitoes a second feeding a couple of days later—and with just regular blood that contained no virus—they became much more infectious," said lead author Doug Brackney, PhD, in an ASTMH news release. "The percentage of our Asian tiger mosquitoes [Ae albopictus] that were capable of transmitting virus jumped from 25% to 75%."

The effect was also noted in Ae aegypti, the most common Zika spreader. "We found that the second feeding not only increases the proportion of insects that are infectious, but also shortens the time it takes for the virus to reach their saliva," Brackney said. "It produces a lot of infectious mosquitoes very quickly."

A related study noted that Ae albopictus mosquitoes are expanding their range deeper into New England, according to the release.
Nov 7 ASTMH news release


EPA approves Wolbachia-infected mosquitoes to curb disease threat

Though it hasn't formally announced its decision, the US Environmental Protection Agency (EPA) has cleared the way for MosquitoMate to release its Wolbachia pipientis infected mosquitoes to battle Ae albopictus mosquitoes and combat diseases like Zika, dengue, and yellow fever, Nature News reported yesterday in a news story. It said the EPA notified the company of its decision on Nov 3, which will allow it to release the lab-infected male mosquitoes in 20 states and in Washington, DC.

According to the report, the EPA has restricted the release of the MosquitoMate mosquitoes to places with climates similar to where they were tested, which included Kentucky, New York, and California. Nature said the EPA's approval doesn't extend the use to southeastern states, which have large mosquito populations and longer mosquito seasons, because the company didn't do field trials there.

The company told Nature that it will start selling its mosquitoes in Lexington, Ky., its home base. Then as it scales up protection MosquitoMate will expand availability to other cities in the region, such as Louisville and Cincinnati. Potential customers include homeowners, golf courses, and hotels.

Male mosquitoes infected with naturally occurring Wolbachia bacteria don't bite, and when they mate with female mosquitoes, the eggs don't hatch, a tactic that helps drive down local mosquito populations.

In 2016 a World Health Organization expert group that assessed if any new mosquito control tools could be helped to curb the spread of Zika virus found that Wolbachia was one of only two methods that warranted careful pilot testing with rigorous monitoring.
Nov 6 Nature News story


Brazil study shows chikungunya spike as Zika outbreak wound down

Brazilian investigators writing yesterday in PLoS Neglected Tropical Diseases detail the waning of the Zika outbreak in Recife in the northeast, which was then replaced by a chikungunya outbreak.

The experts assayed acute and convalescent blood samples from 263 patients who had fever and other symptoms suggestive of an arboviral disease and attended an urgent care clinic in the Recife metropolitan area. The patients were in the clinic from May 2015 to May 2016.

Polymerase chain reaction testing determined that 26 (9.9%) were positive for Zika virus and 132 (50.2%) for chikungunya virus but none for dengue virus. This was at a time when there were many official dengue notifications in the area.

The authors concluded, "We show that when Zika cases started to decrease, chikungunya cases appeared and increased rapidly, remaining high until the end of the study. We also highlight the high levels of cross-reactivity on dengue serological assays with ZIKV-positive samples, emphasizing the importance of choosing appropriate tests in areas with simultaneous circulation of arboviruses."
Nov 6 PLoS Negl Trop Dis report

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