By John P. Roche, Ph.D.
Dengue fever, caused by a virus spread by the yellow fever mosquito (Aedes aegypti), can cause serious illness in humans, ranging from fever and flu-like symptoms to hemorrhagic fever and death. The World Health Organization (WHO) estimates 4.6 million cases of dengue fever occurred globally in 2023 and that there may be 50 to 100 million dengue virus infections per year. There are four different strains, or “serotypes,” of dengue virus—DENV-1, DENV-2, DENV3, and DENV-4—all of which can cause illness. Dengue fever is a growing problem in tropical and subtropical areas; the yellow fever mosquito that spreads dengue virus is expanding its range, and the number of annual cases has been rising for several years.
Making predictions about the spread of a vector-borne pathogen such as dengue virus relies on information on vectorial capacity, the ability of a vector (such as a mosquito or tick) to spread a pathogen. Vectorial capacity can be influenced by a variety of factors, including the vector’s physiology, behavior, and life history. Ioana Mateescu and Sebastian Lequime, Ph.D., of the University of Groningen in the Netherlands conducted a review of research on how infection of Aedes aegypti mosquitoes by dengue virus can influence their vectorial capacity. They also looked at research examining if the virus was manipulating its host—or if changes in the host were byproducts of other factors. The central practical goal behind their research review was to explore how we can use discoveries about effects of the virus on the vector to help contain the spread of dengue fever. Their study was published in October in the Journal of Medical Entomology.
Feeding-related behaviors contributing to vectorial capacity include locomotion, host seeking, and feeding. Some studies have found that genes related to locomotor and host-seeking behaviors were upregulated in mosquitoes infected with dengue virus. For example, Lima-Camara et al. (2011), studying DENV-2 infection in yellow fever mosquito females, observed increased locomotor activity from two to six days post-infection. Tallon et al. (2020), studying DENV-1 infection in yellow fever mosquitoes, observed an increase in locomotor activity four to six days post-infection but a decrease in locomotor activity 14 to 16 days post-infection.
For feeding time, the research results are mixed. For example, Platt et al. (1997) found increased probing and feeding time in yellow fever mosquitoes infected with DENV-3. But Putnam and Scott (1995) observed no difference in feeding time 14 days post-infection with mosquitoes infected with DENV-2.
Several other feeding behaviors in yellow fever mosquitoes, including rate of re-feeding after interruption (avidity), blood ingestion time, frequency of probing, and frequency of biting were found to increase with dengue infection in some studies.
Life history traits related to vectorial capacity include survival, oviposition, and fecundity. Infection with DENV was found to decrease survival in studies on DENV-1 and DENV-2 but did not have an effect on survival in studies with DENV-4. For example, Keirsebelik et al. (2024) observed that infection with DENV-1 decreased survival, but Maraschin et al. (2023) found that infection with DENV-4 did not affect survival of yellow fever mosquitoes. It is still unknown if dengue infection has any effect on fecundity.
The question of manipulation versus byproduct remains a fascinating one—and an unresolved area of research. It is particularly difficult to address because it is a multi-level issue. For example, to find support for manipulation, investigators would first have to determine if infection provides a benefit to the virus. And if infection was found to provide a benefit, investigators would then have to determine if that benefit was selected for by natural selection, something that is extremely difficult to test. The alternative hypothesis is that an observed benefit is due to other factors—in other words, that it is a byproduct.
Mateescu and Lequime’s review provides an extensive summary of the literature examining effects of dengue infection on vectorial capacity. One key finding of the review was that the current state of the art in this field has some notable problems and difficulties. One difficulty is that different studies looked at different serotypes, and different serotypes sometimes have different effects. Most research so far has been done on DENV-2. Much more research should be conducted comparing how dengue infection affects traits in all four different serotypes.
Another difficulty is that different studies used different methodologies. For example, different behavioral assays have been used in different studies of yellow fever mosquito behavior, making cross-study comparisons difficult. “The biggest challenge to this research,” Lequime says, “is probably to be able to have everyone use a similar methodology or framework to analyze these interactions. That way, we can provide clear comparisons and hopefully get clearer insights.”
There is a great amount of research still to be done on the effects of dengue infection on Aedes aegypti mosquito vectorial capacity. And the authors point out that additional comparative research is needed to examine if similar patterns are present in other vector species being infected by other arboviruses. But this review provides a vital road map to what has been found so far with dengue virus in Aedes aegypti mosquitoes and what remains to be tested in the future.
“I think it’s interesting to note that the potential effects of dengue, and maybe other arboviruses, have on their host is somewhat overlooked currently,” Lequime says, “especially in designing epidemiological models that are useful to assess epidemic risks. I would argue it’s an important factor to explore for the future.” The findings from past studies detailed in Mateescu and Lequime’s review, and future studies building on their review, promise to help inform measures to lessen or prevent the burden of dengue fever.
John P. Roche, Ph.D., is an author, biologist, and science writer with a Ph.D. and postdoctoral fellowship in the biological sciences and a dedication to making rigorous science clear and accessible. He authors books and articles, and writes for universities, scientific societies, and publishers. Professional experience includes serving as a scientist and scientific writer at Indiana University, Boston College, and the UMass Chan Medical School; and as editor of science periodicals at Indiana University and Boston College.
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