Tag: dengue virus

Categories : Diseases, Syndromes and Conditions Mental HealthTags :

Dengue Linked to Heightened Short- and Long-term Risk of Depression in Taiwan

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New study also uncovers short-term links with sleep disorders

Photo by Ekamelev on Unsplash

Analysis of the medical records of nearly 50 000 people who experienced dengue fever in Taiwan suggests that this disease is associated with elevated short- and long-term risk of depression. Hsin-I Shih and colleagues of National Cheng Kung University and National Health Research Institutes, Taiwan present these findings in the open-access journal PLOS Neglected Tropical Diseases.

People may develop dengue fever after being bitten by a mosquito carrying the dengue virus. Dengue fever can be mild, but it can also progress to life-threatening severity, and some people may have long-term health effects. Prior research has uncovered links between active dengue fever and psychiatric disorders, such as depression and anxiety. However, few studies have examined the long-term risk of such disorders after a dengue infection.

To address this knowledge gap, Shih and colleagues analysed the medical records of 45 334 dengue patients in Taiwan and, for comparison, 226 670 patients who did not experience dengue. Covering the years 2002 to 2015, the researchers examined whether dengue patients were more likely to develop anxiety, depressive disorders, and sleep disorders at various time points after infection. To help account for other factors that could influence mental health, the dengue patients were grouped with demographically similar non-dengue patients for statistical analysis.

The researchers found that the dengue patients had a greater likelihood of developing a depressive order across all timeframes, including less than three months, three to 12 months, and more than 12 months after their infection. Sleep disorders were only elevated within three to 12 months post-infection, and there was no observable elevated risk of anxiety.

Taking a closer look at patients whose dengue was severe enough for them to be hospitalized, the researchers found an elevated risk of anxiety disorders within the first three months of infection, as well as elevated risk of sleep disorders in the first 12 months. This subgroup also had elevated risk of depression across timeframes.

These findings suggest a potential link between dengue fever and subsequent depressive disorder. However, further research is needed to determine whether dengue contributes directly to development of depression, or if the association is due to some indirect mechanism.

The authors add: “This study highlights a significant association between dengue fever and an elevated risk of depression in both the short and long term, underscoring the need for further research into the mental health impacts of dengue infection.”

Provided by PLOS

Categories : Environmental Effects GeneticsTags :

Scientists Abuzz over a Genetic Way to Deafen Mosquitoes

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Photo by Ekamelev on Unsplash

Specific receptors in the ears of mosquitoes have been revealed to modulate their hearing, finds a new study led by researchers at UCL and University of Oldenburg. Since male mosquitoes need to hear female mosquitoes is a crucial factor in their reproduction, this discovery could help develop new insecticides and control the spread of harmful diseases, such as malaria, dengue, and yellow fever.

In the study, published in Nature Communications, the researchers focused on a signalling pathway involving a molecule called octopamine. They demonstrated that it is key for mosquito hearing and mating partner detection, and so is a potential new target for mosquito control.

Male mosquitoes acoustically detect the buzz generated by females within large swarms that form transiently at dusk.

As swarms are potentially noisy, mosquitoes have developed highly sophisticated ears to detect the faint flight tone of females amid hundreds of mosquitoes flying together.

However, the molecular mechanisms by which mosquito males ‘sharpen their ears’ to respond to female flight tones during swarm time have been largely unknown.

The researchers looked at the expression of genes in the mosquito ear and found that an octopamine receptor specifically peaks in the male mosquito ear when mosquitoes swarm.

The study found that octopamine affects mosquito hearing on multiple levels. It modulates the frequency tuning and stiffness of the sound receiver in the male ear, and also controls other mechanical changes to boost the detection of the female.

The researchers demonstrated that the octopaminergic system in the mosquito ear can be targeted by insecticides. Mosquito mating is a bottleneck for mosquito survival, so identifying new targets to disrupt it is key to controlling disease-transmitting mosquito populations.

Source: University College London

Categories : Diseases, Syndromes and ConditionsTags :

Zika Can Mutate to Increase its Infectivity

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Mosquito, a malaria parasite vector
Photo by Егор Камелев on Unsplash

Researchers have found that Zika virus has the potential to mutate and increase its infectivity, potentially breaking through pre-existing immunity.

“The world should monitor the emergence of this Zika virus variant,” said LJI Professor Sujan Shresta, PhD, who co-led the La Jolla Institute for Immunology (LJI) study which is published in Cell Reports.

A mosquito-borne virus, symptoms of Zika infection are usually mild in adults. However, in a developing foetus, infection can cause birth defects such as microcephaly.

Zika virus and dengue virus occur together in a number of countries. Both viruses are a mosquito-borne flavivirus, sharing biological similarity:  similar enough that prior dengue exposure can offer immune protection against Zika.

“In areas where Zika is prevalent, a vast majority of people have already been exposed to dengue virus and have both T cells and antibodies that cross-react,” said Prof Shresta.

Unfortunately, both viruses share the trait of rapid mutation. “Dengue and Zika are RNA viruses, which means they can change their genome,” she further explained. “When there are so many mosquitoes and so many human hosts, these viruses are constantly moving back and forth and evolving.”

To study Zika’s fast-paced evolution, the researchers simulated infection cycles that repeatedly switched back and forth between mosquito cells and mice. This painted a picture of how Zika virus naturally evolves as it encounters more hosts.

The LJI team found that an easy change of a single amino acid allows the virus to make more copies of itself — and help infections take hold more easily. This mutation (called NS2B I39V/I39T mutation) boosts viral replication in both mice and mosquitoes – and also in human cells.

“This single mutation is sufficient to enhance Zika virus virulence,” commented study first author Jose Angel Regla-Nava, PhD. “A high replication rate in either a mosquito or human host could increase viral transmission or pathogenicity – and cause a new outbreak.”

Prof Shresta added, “The Zika variant that we identified had evolved to the point where the cross-protective immunity afforded by prior dengue infection was no longer effective in mice. Unfortunately for us, if this variant becomes prevalent, we may have the same issues in real life.”

To help prepare for this variant, Dr Shresta’s laboratory is already looking at ways to tailor Zika vaccines and treatments that counteract this dangerous mutation.

“We want to understand at what point in the viral life cycle this mutation makes a difference,” said Dr Shresta.

Source: La Jolla Institute for Immunology