- Author: Anne Schellman
In years past, I would get bitten by mosquitoes when out late at night. But in the past decade, I've been bitten frequently during the day, and this year seems to be particularly bad, possibly due to favorable weather conditions for mosquitoes.
Invasive Mosquitoes
West Nile Virus
How can you protect yourself?
Although day biting mosquitoes can bite through clothing, it can help reduce bites. You can also wear an application of repellent underneath. The CDC recommends using an insect repellent containing the active ingredients DEET, Picardin, IR3535, or the plant-based oil of lemon eucalyptus. Please note, the last active ingredient is not an essential oil.
How to Prevent Mosquitoes
For more in-depth information and tips for how to protect yourself and your family in and around your home, visit the UC IPM Website at https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
Resources
California Department of Public Health https://www.cdph.ca.gov/Programs/CID/DCDC/pages/Aedes-aegypti-and-Aedes-albopictus-mosquitoes.aspx
EPA https://www.epa.gov/mosquitocontrol/general-information-about-mosquitoes
UC IPM Pest Notes: Mosquitoes https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
West Nile CA https://westnile.ca.gov/
UC IPM Quick Tips: Mosquitoes https://ipm.ucanr.edu/legacy_assets/pdf/qt/qtmosquito.pdf or if you prefer in Spanish, https://ipm.ucanr.edu/legacy_assets/pdf/qtsp/qtspmosquitoes.pdf
Stanislaus County, Human West Nile Virus Cases in Stanislaus County, https://www.schsa.org/pdf/press-releases/2023/WNV%2023-06.pdf
Anne Schellman has been the UC Master Gardener Coordinator in Stanislaus County since the program started in 2018.
/h3>/h3>/h3>/h3>/h3>Mosquito Awareness Week, observed April 16 - 22, 2023, educates California residents about mosquitoes and how to help prevent the spread of mosquito-transmitted diseases.
One of the wettest years in history has left standing water across the state, creating perfect conditions for mosquitoes to develop. Stagnant water creates havens for disease-spreading mosquitoes, and mosquito experts are concerned this could be a long and intense mosquito season.
“After record amounts of rainfall this year, it is really important for all Californians to dump and drain standing water that has accumulated in their yards, porches, and patios,” said Assemblymember Jim Wood, who authored the state resolution recognizing California Mosquito Awareness Week. “It only takes a small amount of water for mosquitoes to develop so removing all stagnant water is a simple but very effective way to help to eliminate mosquitoes from our community. Not only are mosquitoes a nuisance, but they can transmit deadly diseases. Let's all work together to fight the bite!”
West Nile virus, spread by Culex mosquitoes, is the most prevalent and serious mosquito-borne disease in California. There is no human vaccine for West Nile virus, a disease which can cause debilitating cases of meningitis, encephalitis, and even death. In 2022, there were 209 human West Nile virus disease cases from 28 counties in California, including 13 human deaths.
In addition, invasive Aedes mosquitoes continue to spread throughout the state. First detected in 2013, they have spread to 25 counties and 300 cities and towns. These mosquitoes are very hard to control and pose a serious public health threat because they can spread diseases like Zika, dengue, chikungunya, and yellow fever to people and animal heartworm to pets.
According to the California Department of Public Health, since 2016 there have been nearly 900 California residents with travel-associated dengue infections. While there has not yet been local transmission of dengue in the state, it is occurring at California's borders, making the threat even more real. In 2022, the border state of Sonora, Mexico had more than 9,000 cases with 91 people dying from dengue. In December 2022 in Maricopa County, Arizona, two individuals tested positive for dengue, which they acquired locally from a mosquito bite.
“While all of the rain has been great for the drought, it provides mosquitoes with more places to lay their eggs,” said Wakoli Wekesa, PhD, president of the Mosquito and Vector Control Association of California. “As we work to keep Californians safe from mosquito-transmitted diseases and combat the spread of invasive Aedes, it's critical that residents take simple precautions to protect themselves and keep their communities mosquito-free.”
Mosquito experts say the future of mosquito control requires innovation to protect the public from mosquito-borne diseases. Mosquito and vector control agencies in California are exploring the potential use of three innovative technologies: self-limiting mosquitoes, Wolbachia, and irradiation. More information about the need for innovative technologies and how they work is available on the MVCAC website.
Everyone can do their part to help prevent mosquito bites:
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Apply insect repellent containing an EPA-registered active ingredient, including DEET, picaridin, oil of lemon eucalyptus, or IR3535, to clothes and exposed skin according to label instructions. Repellents keep mosquitoes from biting. It is important to follow EPA and CDC guidelines for the safe use of repellents on children.
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Dress in long sleeves and pants, especially if outside at dawn and dusk when mosquitoes that can spread West Nile virus are most active.
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Install screens on windows and doors and keep them in good repair to keep mosquitoes out of your home.
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Eliminate all sources of standing water on your property, including in flowerpots, old tires, buckets, pet dishes, and trash cans. Mosquitoes lay their eggs in very small amounts of standing water.
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Repair leaking faucets and broken sprinklers that can contribute to standing water around your home.
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Clean rain gutters clogged with leaves.
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Report neglected swimming pools and day-biting mosquitoes to your local mosquito and vector control agency (agency information can be found at www.mvcac.org)
To learn more, please visit the MVCAC website or the California Department of Public Health Mosquitoes and Mosquito-Borne Diseases webpage.
About MVCAC
The Mosquito and Vector Control Association of California (MVCAC) is the statewide voice for mosquito and vector control professionals. The association provides public health information, expertise, mosquito and vector-borne disease surveillance, innovative research, professional training, effective legislative and regulatory advocacy on behalf of California public agencies.
[Shared from the Mosquito and Vector Control Association of California. View UC IPM's Pest Notes: Mosquitoes for more information.]
- Author: Kathy Keatley Garvey
By Geoff Attardo
Assistant Professor of Entomology and Nematology at UC Davis
California's changing climate is creating a myriad of public health concerns. Wildfires, intense heatwaves, and a drought are the most readily apparent. However, increasingly temperate winters are also facilitating the spread of invasive disease-spreading mosquitoes throughout the state. Just as our fire authorities need a robust set of tools to address wildfires, it is critical that mosquito control and public health professionals have a wide range of tools to protect Californians from mosquito-borne diseases.
The growing presence of Aedes aegypti mosquitoes, which can transmit the viruses that cause Zika, dengue, chikungunya, and yellow fever as well as the parasite that causes heartworm in pets, is a major public health threat. In 2013 this invasive species was detected in the Central Valley and has been found in California every year since. These mosquitoes cohabitate with humans and often hitchhike facilitating their spread.
Aedes aegypti lay eggs in flowerpots, water storage containers or anything capable of holding small amounts of water. Part of the problem, as highlighted in our research in Frontiers in Tropical Diseases, is that these mosquitoes have cryptic breeding sites in residential areas where mosquito control agencies can't easily inspect and treat.
In addition, their eggs can dry out and then hatch when rehydrated. In fact, when Aedes aegypti were detected in 2014 in the city of Exeter there was a large eradication effort. The effort appeared successful, as they were no longer detectable in 2015. Yet, the mosquitoes were detected in Exeter again in 2018. The unique biology of this invasive species has allowed it to expand its geographical range and today they are present in more than 300 cities in California.
Another key factor is their inherent resistance to a class of insecticides called pyrethroids, which have been a mainstay for adult mosquito control because they have low toxicity to humans and other animals. Work from our lab and the California Department of Public Health found increasing insecticide resistance in these mosquitoes (Parasites and Vectors) which limits the ability of mosquito control agencies to act against adult mosquitoes in a time of crisis.
In order to protect public health, mosquito control agencies need effective tools in their toolbox. One innovative approach takes advantage of the fact that male mosquitoes do not bite; only female mosquitoes bite and can spread viruses. This approach works by releasing sterile male Aedes aegypti mosquitoes. These male-only mosquitoes carry a self-limiting gene that prevents their female offspring from surviving. When they mate with females, this reduces the abundance of biting females in the next generation. One of the benefits of this species-specific approach is that it only targets the Aedes aegypti mosquito. This means that wildlife, such as butterflies and bees, are unharmed.
The public health threat of Aedes aegypti cannot be overstated. The World Health Organization (WHO) estimates that dengue fever causes approximately 40,000 deaths a year and Zika virus, of which there were over 5,100 symptomatic domestic cases in 2016, is known to cause serious birth defects and miscarriage as well as Guillain-Barré syndrome. The WHO also said “the potential public health benefit of practical and effective new tools to reduce or even eliminate diseases such as malaria and dengue is clear and widely recognized.”
A company called Oxitec is working with government agencies to bring its innovative mosquito control technology to the U.S. In August, they announced they are seeking regulatory approvals to expand their pilot program to bring their Friendly™ Aedes aegypti technology to California. I encourage regulators to allow the company to work with mosquito control agencies to determine the technology's effectiveness in California.
It's clear that we need efficient mosquito control tools, and we cannot wait until we have a public health emergency to act. As we have seen with the COVID pandemic it is critical to have an infrastructure in place, especially one that includes innovative – and proven – technologies, to help public health and mosquito controls stay ahead of the curve.
- Author: Kathy Keatley Garvey
What's medical entomolology?
Anyone who's an entomologist or who works in entomology is asked that question periodically. Medical, they know. Entomology? Often not. But medical entomology?
Well, it's the study of relationships among arthorpods, microbial pathogens and human health, according to medical entomologist Thomas Scott, professor of entomology at UC Davis.
Scott teaches courses on medical entomology. His next one: the 2009 winter quarter, Jan. 5 through March 16.
Worldwide, Scott says, arthropod-borne diseases have devastating effects on human health; they are a leading cause of human morbidity and mortality.
In his course, he explains the basic biology of medically important arthropods and the pathogens they transmit. The diseases include malaria, dengue fever, yellow fever, West Nile virus, Lyme disease and River Blindness.
Scott, a noted mosquito-borne disease expert and newly elected fellow of the prestigious American Association for the Advancement of Science (for "distinguished contributions to the biology and ecology of mosquitoes and his leadership in developing strategic concepts for preventing dengue fever and other mosquito-borne diseases”) does research from his mosquito research laboratory at UC Davis and at field stations in Peru, Thailand and Mexico.
In January, Scott hosted the 42nd annual U.S.-Japan Parasitic Disease Conference on the UC Davis campus. Some 100 scientists from throughout the world participated in the three-day conference "to develop a cross-cutting perspective on what the priorities should be for the future research on arthropod vectors of disease," he explained.
With new and emerging diseases, increasing national and international travel, settlement in endemic areas, and the proliferation of commerce, we can expect disease from vector-borne pathogens to increase, Scott says.
It's obvious what we need less of (diseases) and what we need more of (medical entomologists).