A Survey of the Mosquitoes of Guam in Two Periods in 1948 and 1949 and Its Epidemiological Implications

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Summary and Conclusions

Two surveys of the mosquitoes of Guam in the post-World War II period have provided new data of value to persons concerned with mosquito control and epidemiological investigations on diseases of man.

In these studies two species of mosquitoes are recorded from Guam for the first time: Aedes albopictus and Anopheles subpictus indefinitus. The latter record is the first of an Anopheles imported and established in the Central Pacific Area. It is felt that both of these species were introduced in the period following 1945, but there is no indication of the way in which this occurred.

Interpretation of data on the biology of the adult stage of the 11 species now known from Guam, coupled with a review of their known disease vector abilities, has permitted a re-evaluation of the relative potential importance of the various species as vectors of human disease. It is concluded that as vectors of Japanese B encephalitis the following species should be kept under surveillance: Culex quinquefasciatus, Culex annulirostris marinae, Aedes vexans nocturnus, Aedes albopictus and Aedes pandani. Laboratory tests for encephalitis viruses on 20,361 mosquitoes representing 6 species have been negative. For dengue fever only Aedes albopictus would be suspected as a vector at this time. This opinion is influenced by the almost complete disappearance of Aedes aegypti, possibly due to earlier intensive control activities. Because of the habits of Anopheles subpictus indefinitus, the possibility of autochthonous malaria is believed to be minimal. It is felt that nocturnal filariasis might well be introduced and become endemic through the vector activities of Culex quinquefasciatus.

A sample of 2,261 larval collections have been analyzed as to larval habitats, association of various species and monthly distribution of sources. It is concluded that the majority of domestic pest and potential disease vector mosquitoes have come from sources directly attributable to the activities of man, namely, domestic water receptacles and domestic and military refuse. It is suggested that any program for mosquito control on Guam should be aimed at the detection and correction or elimination of these mosquito sources. In the immediate vicinity of heavily populated areas, inspection and abatement of mosquito sources in ground pools and water collections in plants and coconut shells would be an important adjunct to this program during and immediately following the rainy season.

Author Notes

From the Neurotropic Virus Unit of the George Williams Hooper Foundation for Medical Research (W. C. R. and A. R.) and the School of Public Health (W. C. R.), University of California, San Francisco and Berkeley, California.

This investigation was carried out in collaboration with the Commission on Virus and Rickettsial Diseases, Army Epidemiological Board, Office of the Surgeon General, United States Army.