Global & Disaster Medicine

Archive for the ‘Dengue’ Category

A dengue outbreak has killed at least 21 people in India’s southern state of Kerala in the past three weeks.

Reuters

 


A new antibody-based assay distinguishes Zika from similar viral infections

Eureka

“A new test is the best-to-date in differentiating Zika virus infections from infections caused by similar viruses. The antibody-based assay, developed by researchers at UC Berkeley and Humabs BioMed, a private biotechnology company, is a simple, cost-effective way to determine if a person’s infection is from the Zika virus or another virus of the same family, such as dengue and West Nile viruses….”

PNAS

“…..This study demonstrates that the antibody-based assay we developed and implemented in five countries has high specificity and sensitivity in the detection of recent and past ZIKV infections. The ZIKV nonstructural protein 1 (NS1) blockade-of-binding ELISA assay is a simple, robust, and low-cost solution for Zika surveillance programs, seroprevalence studies, and intervention trials in flavivirus-endemic areas….”


WHO: New vector control response seen as game-changer

WHO

The call came from the WHO Director-General in May 2016 for a renewed attack on the global spread of vector-borne diseases.

“What we are seeing now looks more and more like a dramatic resurgence of the threat from emerging and re-emerging infectious diseases,” Dr Margaret Chan told Member States at the Sixty-ninth World Health Assembly. “The world is not prepared to cope.”

Dr Chan noted that the spread of Zika virus disease, the resurgence of dengue, and the emerging threat from chikungunya were the result of weak mosquito control policies from the 1970s. It was during that decade that funding and efforts for vector control were greatly reduced.

‘Vector control has not been a priority’

Dr Ana Carolina Silva Santelli has witnessed this first-hand. As former head of the programme for malaria, dengue, Zika and chikungunya with Brazil’s Ministry of Health, she saw vector-control efforts wane over her 13 years there. Equipment such as spraying machines, supplies such as insecticides and personnel such as entomologists were not replaced as needed. “Vector control has not been a priority,” she said.

Today more than 80% of the world’s population is at risk of vector-borne disease, with half at risk of two or more diseases. Mosquitoes can transmit, among other diseases, malaria, lymphatic filariasis, Japanese encephalitis and West Nile; flies can transmit onchocerciasis, leishmaniasis and human African trypanosomiasis (sleeping sickness); and bugs or ticks can transmit Chagas disease, Lyme disease and encephalitis.

Together, the major vector-borne diseases kill more than 700 000 people each year, with populations in poverty-stricken tropical and subtropical areas at highest risk. Other vector-borne diseases, such as tick-borne encephalitis, are of increasing concern in temperate regions.

Rapid unplanned urbanization, massive increases in international travel and trade, altered agricultural practices and other environmental changes are fuelling the spread of vectors worldwide, putting more and more people at risk. Malnourished people and those with weakened immunity are especially susceptible.

A new approach

Over the past year, WHO has spearheaded a new strategic approach to reprioritize vector control. The Global Malaria Programme and the Department of Control of Neglected Tropical Diseases – along with the Special Programme for Research and Training in Tropical Diseases, have led a broad consultation tapping into the experience of ministries of health and technical experts. The process was steered by a group of eminent scientists and public health experts led by Dr Santelli and Professor Thomas Scott from the Department of Entomology and Nematology at the University of California, Davis and resulted in the Global Vector Control Response (GVCR) 2017–2030.

At its Seventieth session, the World Health Assembly unanimously welcomed the proposed response.

The GVCR outlines key areas of activity that will radically change the control of vector-borne diseases:

  • Aligning action across sectors, since vector control is more than just spraying insecticides or delivering nets. That might mean ministries of health working with city planners to eradicate breeding sites used by mosquitoes;
  • Engaging and mobilizing communities to protect themselves and build resilience against future disease outbreaks;
  • Enhancing surveillance to trigger early responses to increases in disease or vector populations, and to identify when and why interventions are not working as expected; and
  • Scaling-up vector-control tools and using them in combination to maximize impact on disease while minimizing impact on the environment.

Specifically, the new integrated approach calls for national programmes to be realigned so that public health workers can focus on the complete spectrum of relevant vectors and thereby control all of the diseases they cause.

Recognizing that efforts must be adapted to local needs and sustained, the success of the response will depend on the ability of countries to strengthen their vector-control programmes with financial resources and staff.

A call to pursue novel interventions aggressively

The GVCR also calls for the aggressive pursuit of promising novel interventions such as devising new insecticides; creating spatial repellents and odour-baited traps; improving house screening; pursuing development of a common bacterium that stops viruses from replicating inside mosquitoes; and modifying the genes of male mosquitoes so that their offspring die early.

Economic development also brings solutions. “If people lived in houses that had solid floors and windows with screens or air conditioning, they wouldn’t need a bednet,” said Professor Scott. “So, by improving people’s standard of living, we would significantly reduce these diseases.”

An entomologist inserts live mosquitoes in wall of a mud house in Kisumu, Kenya

An entomologist inserts live mosquitoes into a standard ‘cone bioassay’. After 30 minutes he will see how many have been killed – this will measure if the insecticide was sprayed properly on the walls, and constitutes intervention monitoring.
WHO/S. Torfinn

The call for a more coherent and holistic approach to vector control does not diminish the considerable advances made against individual vector-borne diseases.

Malaria is a prime example. Over the past 15 years, its incidence in sub-Saharan Africa has been cut by 45% – primarily due to the massive use of insecticide-treated bed nets and spraying of residual insecticides inside houses.

But that success has had a down side.

“We’ve been so successful, in some ways, with our control that we reduced the number of public health entomologists – the people who can do this stuff well,” said Professor Steve Lindsay, a public health entomologist at Durham University in Britain. “We’re a disappearing breed.”

The GVCR calls for countries to invest in a vector-control workforce trained in public health entomology and empowered in health care responses.

“We now need more nuanced control – not one-size-fits-all, but to tailor control to local conditions,” Professor Lindsay said. This is needed to tackle new and emerging diseases, but also to push towards elimination of others such as malaria, he said.

Dr Lindsay noted that, under the new strategic approach, individual diseases such as Zika, dengue and chikungunya will no longer be considered as separate threats. “What this represents is not three different diseases, but one mosquito – Aedes aegypti,” said Professor Lindsay.

GVCR dovetails with Sustainable Development Goals

The GVCR will also help countries achieve at least 6 of the 17 Sustainable Development Goals. Of direct relevance are goal 3 on good health and well-being, goal 6 on clean water and sanitation, and goal 11 on sustainable cities and communities.

The GVCR goals are ambitious – to reduce mortality from vector-borne diseases by at least 75% and incidence by at least 60% by 2030 – and to prevent epidemics in all countries.

The annual price tag is US$ 330 million globally, or about 5 cents per person – for workforce, coordination and surveillance costs. This is a modest additional investment in relation to insecticide-treated nets, indoor sprays and community-based activities, which usually exceed US$ 1 per person protected per year.

It also represents less than 10% of what is currently spent each year on strategies to control vectors that spread malaria, dengue and Chagas disease alone. Ultimately, the shift in focus to integrated and locally adapted vector control will save money.

‘A call for action’

Dr Santelli expressed optimism that the GVCR will help ministries of health around the world gain support from their governments for a renewed focus on vector control.

“Most of all, this document is a call for action,” said Dr Santelli, who now serves as deputy director for epidemiology in the Brasilia office of the U.S. Centers for Disease Control and Prevention.

It will not be easy, she predicts. The work to integrate vector-control efforts across different diseases will require more equipment, more people and more money as well as a change in mentality. “The risk of inaction is greater,” said Dr Santelli, “given the growing number of emerging disease threats.” The potential impact of the GVCR is immense: to put in place new strategies that will reduce overall burden and, in some places, even eliminate these diseases once and for all.


edes aegypti mosquitoes that carry Zika can also transmit dengue and chikungunya in the same bite.

Nature

Rückert, C. et al. Impact of simultaneous exposure to arboviruses on infection and transmission by Aedes aegypti mosquitoes. Nat. Commun. 8, 15412 doi: 10.1038/ncomms15412 (2017).

“…..Thus, we here expose Ae. aegypti mosquitoes to chikungunya, dengue-2 or Zika viruses, both individually and as double and triple infections. Our results show that these mosquitoes can be infected with and can transmit all combinations of these viruses simultaneously. Importantly, infection, dissemination and transmission rates in mosquitoes are only mildly affected by coinfection…..”


AGS-v: An investigational vaccine that triggers an immune response to mosquito saliva rather than to a specific virus or parasite carried by mosquitoes

NIAID

The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), has launched a Phase 1 clinical trial to test an investigational vaccine intended to provide broad protection against a range of mosquito-transmitted diseases, such as Zika, malaria, West Nile fever and dengue fever, and to hinder the ability of mosquitoes to transmit such infections. The study, which is being conducted at the NIH Clinical Center in Bethesda, Maryland, will examine the experimental vaccine’s safety and ability to generate an immune response.

Mosquito vaccine trial partipant recieves injection

The investigational vaccine, called AGS-v, was developed by the London-based pharmaceutical company SEEK, which has since formed a joint venture with hVIVO in London. The consulting group Halloran has provided regulatory advice to both companies.

Unlike other vaccines targeting specific mosquito-borne diseases, the AGS-v candidate is designed to trigger an immune response to mosquito saliva rather than to a specific virus or parasite carried by mosquitoes. The test vaccine contains four synthetic proteins from mosquito salivary glands. The proteins are designed to induce antibodies in a vaccinated individual and to cause a modified allergic response that can prevent infection when a person is bitten by a disease-carrying mosquito.

“Mosquitoes cause more human disease and death than any other animal,” said NIAID Director Anthony S. Fauci, M.D. “A single vaccine capable of protecting against the scourge of mosquito-borne diseases is a novel concept that, if proven successful, would be a monumental public health advance.”

Led by Matthew J. Memoli, M.D., director of the Clinical Studies Unit in NIAID’s Laboratory of Infectious Diseases, the clinical trial is expected to enroll up to 60 healthy adults ages 18 to 50 years. Participants will be randomly assigned to receive one of three vaccine regimens. The first group will receive two injections of the AGS-v vaccine, 21 days apart. The second group will receive two injections of AGS-v combined with an adjuvant, 21 days apart. The adjuvant is an oil and water mixture commonly added to vaccines to enhance immune responses. The third group will receive two placebo injections of sterile water 21 days apart. Neither the study investigators nor the participants will know who is assigned to each group.

Participants will be asked to return to the clinic twice between vaccinations and twice after the second vaccination to undergo a physical exam and to provide blood samples. Study investigators will examine the blood samples to measure levels of antibodies triggered by vaccination.

Each participant also will return to the Clinical Center approximately 21 days after completing the vaccination schedule to undergo a controlled exposure to biting mosquitoes. The mosquitoes will not be carrying viruses or parasites, so the participants are not at risk of becoming infected with a mosquito-borne disease. Five to 10 female Aedes aegypti mosquitoes from the insectary in NIAID’s Laboratory of Malaria and Vector Research will be put in a feeding device that will be placed on each participant’s arm for 20 minutes. The mosquitoes will bite the participants’ arms through the netting on the feeding devices.

Afterward, investigators will take blood samples from each participant at various time points to see if participants experience a modified response to the mosquito bites as a result of AGS-v vaccination.

Investigators also will examine the mosquitoes after the feeding to assess any changes to their life cycle. Scientists suspect that the mosquitoes who take a blood meal from ASG-v-vaccinated participants may have altered behavior that could lead to early death or a reduced ability to reproduce. This would indicate that the experimental vaccine could also hinder disease transmission by controlling the mosquito population.

All participants will be asked to return to the clinic for follow-up visits every 60 days for five months following the mosquito feeding. A final clinic visit to assess long-term safety will take place approximately 10 months after the mosquito feeding. Throughout the trial, an independent Data and Safety Monitoring Board will review study data to evaluate participant safety and the overall conduct of the study. A medical monitor from NIAID’s Office of Clinical Research Policy and Regulatory Operations will also perform routine safety assessments.

The study is expected to be completed by summer 2018. For more information about the trial, see ClinicalTrials.gov using the trial identifier NCT03055000 (link is external).


Mosquito-disseminated pyriproxyfen (PPF), a potent juvenile-killing insecticide, has potential to block mosquito-borne virus transmission citywide

PLOS

Abad-Franch F, Zamora-Perea E, Luz SLB (2017) Mosquito-Disseminated Insecticide for Citywide Vector Control and Its Potential to Block Arbovirus Epidemics: Entomological Observations and Modeling Results from Amazonian Brazil. PLoS Med 14(1): e1002213. doi:10.1371/journal.pmed.1002213

Aedes-aegypti_1

 

 


In 2013 there were a total of 58.40 million symptomatic dengue virus infections including 13 586 fatal cases, and that the total annual global cost of dengue illness was US$8·9 billion.

The Lancet

Image: Lab Confirmed cases of Dengue in South America

Image: Dengue in the world

 

 


Group from Argentina developes a plastic ovitrap, a small cup made from low-density polyethylene that has been infused with pyriproxyfen to knock off Aedes mosquitoes

Aedes Traps

 

Biological and Chemical Characterization of a New Larvicide Ovitrap Made of Plastic With Pyriproxyfen Incorporated for Aedes aegypti (Diptera: Culicidae) Control

Brazil: Zika isn’t the only emergency. 2 other mosquito-borne viruses are spiking: Dengue and CHIKV. Meanwhile, the country is going through a massive economic and political crisis as well, facing one of the worst recessions in its history.

NPR

Recife:  “….New cases of microcephaly are dramatically down. Last November, Recife registered 125 cases. But since the beginning of this year, the numbers have hovered around 25 a month……[T]he decline was expected: Women giving birth this spring would have become pregnant during the cooler winter period when there were fewer mosquitoes around to transmit Zika……”


Fighting the Aedes mosquito

Graphic: Mosquito prevention starts with you


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