Each summer, hordes of these insects descend on backyards, parks and campgrounds. While most mosquitoes are merely nuisances, some can transmit serious diseases such as encephalitis and malaria in humans and heartworm disease in dogs.
Two different kinds of mosquitoes plague in Hong Kong. Floodwater (temporary pool) mosquitoes deposit their eggs singly in low-lying areas that will be flooded later. Under normal summer temperatures, large numbers of biting mosquitoes will emerge about two weeks after heavy rains and can be a major nuisance problem for several weeks. The most common of these in Hong Kong is the inland floodwater mosquito. A vicious biter, this mosquito will commonly fly 10 or more miles from where they hatch, particularly along prevailing winds.
Vector mosquitoes carry diseases and lay their eggs in stagnant ditches and sewage treatment ponds or water in treeholes, old tires, clogged gutters, old tin cans and anything else that will hold water. Eggs are laid on or just above the water surface, where they usually hatch within two to three days.
Another disease-carrying mosquito is the Asian tiger mosquito. An aggressive day-biting mosquito, it breeds in large numbers in water-filled artificial containers.
Floodwater mosquitoes will transmit heartworm disease in dogs, as do Culex mosquitoes. The worms live and reproduce in the heart and pulmonary vessels and can severely weaken or kill the dog. Although difficult to treat, the disease is easily prevented by medication prescribed by a veterinarian. And the most common human illness carried by mosquitoes is encephalitis. This inflammation of the brain is caused by viruses and the disease can range from mild to severe. Severe symptoms include rapid onset of severe headaches, high fever and mental disturbances, such as confusion, irritability, tremors, stupor and coma. Severe cases sometimes end in death or with survivors suffering permanent physical and mental disabilities.
The first and best defense against these pests and the illnesses they may carry is to eliminate the places where they breed. Here are a few suggestions:
Community-wide mosquito abatement efforts can be quite effective if they are conducted as part of an integrated pest management program. This includes monitoring and draining or treating areas where mosquitoes breed — such as street catch basins, occasionally flooded marshes, river backwater areas, swamps and other low-lying areas.
When it is necessary to be outdoors, apply insect repellent as indicated on the repellent label. The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate. Apply repellents to clothes whenever possible; apply sparingly to exposed skin if label permits. Consult a physician before using repellents on young children.