Aedes aegypti Mosquitos Found in Fresno. So far, they've tested negative for the deadly viruses they transmit

Hello everyone!

In summer 2013, I traveled to the Peruvian Amazon to study mosquito ecology. Somewhat ironically, I got sick with dengue (or possible chikungunyua, the diagnosis was never conclusive). Seeing that these mosquitos are spreading north is a bit unsettling for someone who knows personally what the viruses they carry are capable of! Dengue and chikungunya are mosquito-borne viruses that cause rashes, fever (sometimes hemorrhagic in the case of dengue), bone/muscle pain among numerous symptoms. These viruses can be deadly if the patient doesn't get proper medical attention!

With the ebola epidemic ravaging West Africa, it’s easy to forget that we in the United States may not be safe from outbreaks either. Last week, the mosquito Aedes aegypti was found in Fresno when distric health workers placed 120 mosquito traps throughout the city.

Aedes aegypti, adult, Pialoux et al 2007

When they checked the traps, they found the Aedes larvae. A. aegypti is thought to have originated from Africa, although it has spread throughout the tropics.

Fresno isn’t that far from us! (Google Maps)

Why are these mosquitos interesting? They are known to transmit several deadly viral diseases that may soon spread from the tropics: yellow fever, dengue fever and chikungunya. Infections from these viruses can cause fever, severe headaches and even death in extreme cases. None of the mosquitos the health department found tested positive for any of these viruses, but should one of the mosquitos bite a person who traveled to a region with endemic dengue, chikungunya or yellow fever. These viruses reproduce in the guts of mosquitos, as well as in human cells. When a mosquito bites an infected human, it can contract the virus and transmit it to its next victim. Our warming, increasingly interconnected world is allowing these mosquitos, and possibly the viruses they transmit, to spread to higher latitudes. 

References:

http://www.fresnobee.com/2014/09/22/4138718/mosquito-that-can-spread-yellow.html

http://www.cdc.gov/dengue/

http://www.cdc.gov/chikungunya/

Google Maps

Gubler, Duane. "Dengue/Dengue Hemorrhagic Fever: The Emergence Of A Global Health Problem." Emerging Infectious Diseases 1.2 (1995): 55-57. Print.

Pialoux, Gilles, Bernard-Alex Gaüzère, Stéphane Jauréguiberry, and Michel Strobel. "Chikungunya, an epidemic arbovirosis." The Lancet Infectious Diseases 7.5 (2007): 319-327. Print.
Mousson, Laurence, Catherine Dauga, Thomas Garrigues, Francis Schaffner, Marie Vazeille, and Anna-Bella Failloux. 

"Phylogeography of Aedes ( Stegomyia ) aegypti (L.) and Aedes ( Stegomyia ) albopictus (Skuse) (Diptera: Culicidae) based on mitochondrial DNA variations."Genetical Research 86.01 (2005): 1. Print.

--by Joe Getsy '15

West Nile Virus Outbreak in Bakersfield

Hey everyone!

Along with Humans & Viruses, I’m also taking HumBio 154A (Outbreaks, Epidemics & Disease Control Systems), taught by Dr. Sanjay Basu. One of the readings for this week is from Dr. Basu and Dr. David Stuckler’s book, The Body Economic, which examines how economic factors affect physical and mental health trends. Coincidentally, one of the assigned chapters deals with an outbreak of West Nile Virus in Bakersfield in 2007 and again in 2012. As a California native, I was surprised to read about this outbreak and realize that I knew very little about the cases of West Nile and about the virus itself. I thought I’d do some searching and share what I learned about West Nile Virus with the class. Upon searching, I found that human cases of West Nile have been on an increase in Bakersfield recently, making this an important public health concern.

West Nile Virus is most commonly transmitted to humans via mosquito vectors, though there are others as well, including blood transfusions, from mother to child in breastfeeding, and organ transplants. West Nile Virus belongs to the family Flavivirus genus. While West Nile Virus can cause fatal neurological disease in humans, 80% of people will not show any symptoms. These symptoms include fever, headaches, tiredness, and a skin rash (shown below). In severe cases of infection, neurological symptoms, ranging from headaches to paralysis, can occur. No human vaccine presently exists, though one has been developed for use with horses.

In 2007, Bakersfield experienced very hot weather, compounded with the death of birds that often carried the virus due to a lack of water and low overall numbers of mosquitoes, which would logically have decreased the rate of disease transmission. However, at the same time, Bakersfield was in the midst of the California mortgage crisis and subsequently was the center of Californian foreclosures. Almost 2% of Bakersfield had filed for foreclosure at this point, and due to a lack of financial support, homes were foreclosed and not maintained, allowing for weeds to rapidly grow, algae to grow in stagnant water, and foster a breeding ground for mosquitoes. Basu and Stuckler contend that the rise in foreclosures and the lack of public health response to provide a safety net for these families led to the neglect of property, allowing for the virus to propagate under ideal mosquito conditions.

 I thought this was an interesting possible explanation of how West Nile Virus has been transmitted despite unlikely conditions and demonstrated the need for strong public health responses proactively to avoid disease-fostering conditions. Check out The Body Economic (Chapter 8) if you’re interested in learning more!

- Nicole Dalal

References: 
http://www.cdc.gov/westnile/transmission/
http://www.who.int/mediacentre/factsheets/fs354/en/

http://www.bakersfieldnow.com/news/health/Spike-in-West-Nile-virus-cases-prompts-warning-274038271.html

Knipe, D. M., & Howley, P. M. (Eds.). (2013). West Nile Virus. In Fields Virology (6th ed., Vol. 1, pp. 1–3). Lippincott Williams & Wilkins.

Stuckler, D., & Basu, S. (2013). The Body Economic: Why Austerity Kills (pp. 123–137). London: Penguin Group.

 Image: 
http://seeyadoctor.com/wp-content/uploads/2013/05/west-nile-virus-rash-picture-300x243.jpg