To prepare and respond to potential mosquito-borne outbreaks, it is important that effective surveillance be conducted and maintained, which requires properly trained and equipped personnel with the capacity to trap, collect, analyze, and identify mosquitoes and their larvae. Such tasks for Guam belong to the Division of Environmental Health's Mosquito Surveillance and Control Program.
The mosquito is not only a nuisance pest, but more importantly, a highly effective and deadly vector (animal that transmits disease to man). It is responsible for spreading diseases, such as malaria, Dengue Fever, filariasis, encephalitis, and the West Nile virus. In order to prevent human illness and deaths, and control the spread of these diseases, public health departments must ensure that mosquito surveillance and control are implemented.
Outbreaks of Dengue Fever and Japanese B encephalitis were not uncommon on Guam during the 1920’s and 1940’s, but because of eradication efforts by the military post-WWII and improved sanitation of the island since then, Guam has been generally free of mosquito-borne diseases. All reported mosquito-borne illnesses on Guam have been from individuals coming to the island after being infected from their travels in foreign countries where these diseases are endemic. Guam has been fortunate that no mosquito- borne diseases have become established despite the island’s proximity to these endemic countries. However, that may be short-lived.
According to the U.S. Centers for Disease Control and Prevention, vector-borne infectious diseases are “emerging or resurging as a result of changes in public health policy, insecticide and drug resistance, shift in emphasis from prevention to emergency response, demographic and societal changes, and genetic changes in pathogens.” For example, the number of Dengue Hemorrhagic Fever cases is now four times higher than the past 30 years with approximately 50 to 100 million cases of the disease each year.
Based on the surveillance conducted in the 1970’s, there are 24 species of mosquitoes recorded on Guam of which eight (8) are well-known, efficient vectors for transmitting Dengue Fever, Japanese B encephalitis, malaria and filariasis. The latest surveillance activities were conducted in December 2007 by the U.S. Air Force and the U.S. Navy, which substantiated the presence of these disease-transmitting mosquito species, and again in March of 2010.