TWiV 394: Cards in a hand

Vincent and Alan speak with Erica Ollmann Saphire about her career and her work on understanding the functions of proteins of Ebolaviruses, Marburg virus, and other hemorrhagic fever viruses, at ASM Microbe 2016 in Boston, MA.

You can find TWiV #394 at microbe.tv/twiv, or listen or watch the video below.

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Zika Zoo

When we decided to work on Zika virus in February 2016, experiments in mice were certainly part of our plans. However, one does not simply walk into a mouse facility and start inoculating animals with viruses! Carrying out animal experiments requires approval of a detailed protocol by the Institutional Animal Care and Use Committee (IACUC). I have filed many IACUC protocols in the past 30 years, and to work on Zika virus in mice, we had to file a new one. Here is how the process works.

Read the remainder of this article at Zika Diaries.

Are viruses alive?

In this new video from Virus Watch, I tackle the thorny question of whether viruses are alive.

Plenty of people have offered their opinon on this question. The results of a poll I’ve had here on virology blog shows that people are divided on the answer.

But I’m sure I have a good answer to this question.

Interview with J. Michael Bishop

A major new feature of the fourth edition of Principles of Virology is the inclusion of 26 video interviews with leading scientists who have made significant contributions to the field of virology. For the chapter on Transformation and Oncogenesis, Vincent spoke with Nobel Laureate J. Michael Biship, of the University of California, San Francisco, about his career and his work on oncogenes.

TWiV 393: Lovers and livers

Possible sexual transmission of Zika virus, and a cell protein that allows hepatitis C virus replication in cell culture by enhancing vitamin E mediated protection against lipid peroxidation, are the subjects discussed by the TWiVerati on this week’s episode of the science show This Week in Virology.

You can find TWiV #393 at microbe.tv/twiv, or listen below.

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Zika virus and mosquito eradication

Aedes aegyptiThe Aedes aegypti eradication campaign coordinated by the Pan American Health Organization led by 1962 to elimination of this mosquito from 18 countries, including Brazil. Ae. aegypti transmits not only Zika virus, but dengue virus, chikungunya virus, and yellow fever virus. Could control measures be implemented today to achieve similar control of this mosquito? Two articles in PLoS Neglected Tropical Diseases revisit the successful PAHO mosquito control campaign and suggest that its approaches should be revived.

The elimination of Ae. aegypti in 18 countries, which was accompanied by a marked reduction in dengue hemorrhagic fever, was achieved by removing mosquito breeding sites or spraying them with DDT. Determining whether households harbored such breeding sites was essential for the effectiveness of the campaign.

The United States did not participate in the PAHO campaign, even though Ae. aegypti was (and still is) present in that country, and was a vector for outbreaks of dengue fever from the 1920s through the 1940s. Peter Hotez (link to paper) cites a “lack of funds and political will” and “logistical difficulties due to lack of access to private homes or cultural norms of privacy in the US”. As a consequence, by 1970 the US became one of the last reservoirs of Ae. aegypti in the Americas.

Eventually the PAHO campaign fell apart and Ae. aegypti returned, followed by outbreaks of dengue fever in the 1980s in Latin America and the Caribbean, and Chikungunya virus and Zika virus in 2013.

Hotez argues that while control of Ae. aegypti is labor intensive and involves house-to-house spraying, PAHO demonstrated its feasibility. He further suggests that by not participating in the PAHO campaign, the US failed to establish a generation of mosquito control expertise, which is now needed as Zika virus and other mosquito-borne viruses threaten to spread. He calls for an “unprecedented campaign against the Ae. aegypti mosquito”. However, he does not specify exactly what kind of control should be implemented, only saying that “these activities might not closely resemble the Latin American programs of the 1960s”.

Paul Reiter (link to paper) believes that the success of the PAHO campaign “can be attributed to a single aspect of the behavior of the mosquitoes: female Ae. aegypti do not lay all their eggs in one basket”, but rather place them at multiple locations. During the PAHO campaign, infested containers were identified and sprayed with DDT, increasing the likelihood that a female would lay eggs at a site that had been treated. This approach is called perifocal.

The current use of fogging machines to spray residential areas with insecticides has a low impact on mosquito populations, according to Reiter, because they only work for a few minutes when the droplets are airborne. He believes that we should return to perifocal treatments to eliminate mosquitoes, but not using DDT. Rather he suggests the use of other, novel insecticides, such as crystals of deltamethrin embedded in a rain and sun-proof polymer that ensures release for three months.

Reiter acknowledges that long-term use of insecticides leads to resistance, in which case we should turn to the new anti-mosquito approaches that are being developed, including the release of mosquitoes containing Wolbachia bacteria or a lethal gene. But he indicates that these approaches “are some way from mass application”, and meanwhile, perifocal approaches could reduce mosquito populations (although the newer insecticides would first need to be tested).

The best way to prevent viral infection is with a vaccine, but one for Zika virus is likely years away. Meanwhile, mosquito control can make a difference, as it could for the next emerging virus well before a vaccine can be developed.

Virus Watch: How mosquitoes spread viruses

In this episode of Virus Watch, I explain how mosquitoes spread viruses. We’ll look at how a mosquito finds a host, how it finds a blood vessel, and how it delivers viruses to a new host. Don’t blame mosquitoes for viral diseases: it’s not their fault!

TWiV 392: Zika virus!

Four virologists discuss our current understanding of Zika virus biology, pathogenesis, transmission, and prevention, in this special live episode recorded at the American Society for Microbiology in Washington, DC.

You can find TWiV #392 at microbe.tv/twiv, or listen/watch below.

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Virus Watch: Counting Viruses

In this episode of Virus Watch, I show how to do my favorite assay in all of virology – the plaque assay.

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