Understanding Chikungunya

Editor’s Note: The following article appeared on Mike Merchant’s blog, “Insects in the City,” which can be found at http://insectsinthecity.blogspot.com. The blog offers readers news and commentary about the urban pest management industry and is excerpted here with permission of the author.
 

A blood-engorged Aedes albopictus, a common vector of the chikungunya virus. James Gathany, CDC

The black and white Asian tiger mosquito is one of the two most common potential vectors of chikungunya nationwide.

Fortunately for all of us who live and work in the U.S., insect-borne disease is not rampant in our country. But this isn’t something to take for granted either, as we saw last summer with the rapid spread of the chikungunya (chik-un-GOON-ya) virus throughout the Caribbean.

More than 30 years ago as a graduate student taking a course in medical entomology, I learned about all kinds of diseases spread by insects. By far, most of these were tropical and exotic-sounding. Chikungunya virus was one of those diseases I memorized way back then, and have since mostly forgotten.

Chikungunya was first described in 1952 during an outbreak in southern Tanzania (east Africa). The name comes from the Makonde language and means “that which bends up,” referring to the contorted, bent-over appearance due to joint pain suffered by those who contract the disease. Sounds bad, doesn’t it?

While not as serious as some mosquito-borne diseases, including malaria or Eastern equine encephalitis, or even the neurological form of West Nile virus, chikungunya is nothing to sneeze at. While some people have mild cases, it frequently comes with a very bad headache, joint pain, rash and fever. There is no treatment for chikungunya, and there is no vaccine to protect you if you visit places where the disease is active.

When I learned about chikungunya in college, it was found only in eastern Africa and in parts of India and Southeast Asia. That distribution has spread in recent years as outbreaks occurred in parts of western Africa and Europe. In December 2013 the first epidemic on our side of the world was reported when the disease made the jump into the islands of the Caribbean. Since the beginning of 2014, the disease has been spreading like wildfire, with more than a quarter million cases, and more than 20 fatalities in the Caribbean.
 

Chikungunya In The U.S.

Chikungunya has been on the radar of U.S. health officials in recent years largely because its vectors are very common in our country. The principal mosquito vectors of chikungunya are in the genus Aedes. They include the Asian tiger mosquito, Aedes albopictus, and its close relative, the yellow fever mosquito, Aedes aegypti. These are the species that inevitably bite me whenever I chance a trip outside without repellent in my backyard in the Dallas area.

Unlike West Nile virus, birds are not a part of the chikungunya disease cycle. As far as we know, the virus is only viable in mosquitoes and primates. In Africa, the disease lurks both within humans and non-human primates, such as baboons and monkeys. For the virus to take hold here in the U.S., it would have to be common enough to reach an epidemic tipping point. This would occur when enough people are infected to start a cycle from human to mosquito to human again.

We may not have yet reached that tipping point, but we could get there easily. Last July, the first locally acquired cases were reported in Florida. These were the first cases where the victims had not recently traveled to the Caribbean, or other places where the disease is endemic. According to the CDC, between 2006 and 2013 the U.S. averaged about 28 cases of chikungunya annually from travelers. As of February 2015, a total of 2,492 chikungunya virus disease cases were reported to CDC from U.S. states for 2014.
 

How Concerned Should You Be?

So, should you or your customers be worried about chikungunya? If you plan on traveling to the Caribbean this year, definitely! Make sure to carry repellent and use it liberally during your travels to any Caribbean island. At home there is little risk yet; but this could change. As the number of sick travelers returning from Caribbean cruises and high school mission trips increases, the risk of acquiring chikungunya will increase.

All of this increases the value and importance of all residential pest control services, especially where Aedes mosquitoes are active. Technicians servicing homes should be on the lookout for any sources of standing water. These may take the form of storm sewer catchment basins, leaking septic systems, containers or plastic items that catch and hold water, house plant pots with dishes that hold water, bird baths, wheelbarrows, boat covers and other items. You may not be servicing an account specifically for mosquitoes, but pointing out mosquito risk factors is an add-on service to your customer and can increase your value in their eyes. If you have a newsletter or email service, now’s a great time to remind readers of the four Ds:

• Drain and dump standing water
• Dusk and dawn are the highest risk times for mosquitoes (though Aedes mosquitoes are active all day)
• Dress in long-sleeved shirts and long pants when outdoors
• DEET is an ingredient to look for in your insect repellent (or another effective choice such as lemon oil of eucalyptus, picaridin, p-menthane 3,8-diol or IR3535).
   

For more information about where mosquitoes can breed, and how to identify Aedes and other mosquitoes, visit http://mosquitosafari.tamu.edu. For more about chikungunya, visit CDC’s chikungunya web page, www.cdc.gov/chikungunya.  

The author is an entomology specialist for Texas AgriLife Extension. Readers can contact him via email at mmerchant@giemedia.com.