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(1) Emerging Infectious Diseases. 1 (2) (1995): 55-57. Gubler, Duane J, and Gary G Clark. "Dengue/dengue hemorrhagic fever: the emergence of a global health problem." http://www.cdc.gov/ncidod/EID/vol1no2/gubler.htm and (2) Emerging Infectious Diseases. 1 (2) (1995): 39-46. Wilson, Mary E. "Travel and the emergence of infectious diseases." http://www.cdc.gov/ncidod/EID/vol1no2/wilson.htm Dengue & Dengue Hemorrhagic Fever Dengue fever is an illness caused by any one of four different strains of the dengue virus. Apparently you feel as if every one of your bones is broken so it has been called "Break Bone Fever" in many different languages. Typically people survive. Having been exposed to one form of the virus, people generally have long-term (10-40 years) immunity to that form of the virus. However, if they are exposed to a different strain of the virus, they are at increased risk of developing dengue hemorrhagic fever (DHF) which is a severe disease. The current mortality rate from DHF is approximately 5% worldwide. When the disease was first observed, mortality rates of 10-20% were not uncommon. Dengue Hemorrhagic Disease was first recorded in the 1950's in Southeast Asia. Before that time there were reports of dengue fever in several different parts of the world. The different strains of the dengue virus existed, but they were not in the same place. People were not at risk of being exposed to more than one strain of the virus. However with World War II and subsequent increase trade and travel around the world (and accompanying movement of dengue-infected people and mosquitoes around the world) people now can be exposed to different strains. In fact, for some parts of the world, two or more strains now co-exist. This greatly increases the probability that people encounter more than one strain, placing them at risk of developing dengue hemorrhagic fever. Dengue in the Americas is spread by two species of mosquitoes, Aedes aegypti and Aedes albopictus. Aedes aegypti are present in Tucson AZ. There are a significant number of dengue fever cases, transmitted by Aedes aegypti, as close by as Hermisillo, Mexico (about 300 miles away). With the movement of people and mosquitoes (which are adept at hitching rides, for instance in old tires in the back of pick-ups) from Mexico into Tucson, this means Tucsonans are in danger of getting dengue. How bad is the risk? Well, in part we don't know. But we know if there are fewer Aedes aegypti mosquitoes, then we are at less risk. Controling Aedes aegypti The Aedes aegypti mosquito stays low to the ground and doesn't travel very much. So, seeing these mosquitoes in your backyard suggests a breeding site (sufficient standing water) within at most a couple of hundred yards. This means either you or your neighbors are likely growing mosquitoes. The Aedes aegypti female is content to lay her eggs in a container you would use for watering your plants or even in the ceramic saucer you place under some of your container plants. Or in your child's plastic wading pool or wagon. She's not fussy if the water is tap water and contains a little chlorine. She gets along just fine with all kinds of small containers that hold a few day's worth of water. In fact, the water doesn't even have to persist. She can lay her eggs and the next day the water can be gone. The eggs will withstand the drying process and when the container becomes wet again days or even years later, the larvae will develop and adults emerge a few days later. She's got our patterns well under control. Leave a container wet for a few days, get eggs. Let it dry out, then fill it again, leave for a few days, and you get adults. If you grow plants or children in Tucson Rearing mosquitoes is easier than growing plants in Tucson. In fact, it takes careful awareness NOT to rear mosquitoes if you rear either kids or plants in Tucson. What you need to do is make sure that NO water suitable for breeding mosquitoes stands for more than 5 days. This span of time prevents the larvae from developing into adults. If any eggs have hatched into larvae, the larvae will die when the water dries out. Ornamental ponds In ornamental ponds you can rear fish that feed on the mosquito larvae or you can add a bacterium, Bacillus thuringiensis, (B.t.) that contains a toxin that kills the mosquito larvae. There are several different strains of B.t., one of which is incredibly specific for killing mosquito larvae. Inside your house You need to make sure that you aren't breeding mosquitoes INSIDE your house, too. I have a friend who studies insects who sheepishly admitted that he has inadvertently bred them in his house when he left a window slightly opened when he went away for a week. He'd placed his potted plants in the bathtub, on a little platform above some water in the tub, so they would stay humid enough while he was away. A window was cracked open for ventilation. He came back to a bathroom full of mosquitoes. Easy to do. Bottom line It would be difficult NOT to rear mosquitoes at some time in your life if you live in Tucson. Imagine watering your plants and the phone ringing. It would easy to forget that watering can on your porch, perhaps especially easy if you or your child was ill. You can expect to be part of the problem. |
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The University of Arizona Last update Sept 22, 2003 schmidtz at u.arizona.edu willott at u.arizona.edu "http://research.biology.arizona.edu/mosquito/willott/323/project/mosquitoes.html" All contents copyright © 1999-2003. All rights reserved. |