Longitudinal Studies of Aedes aegypti (Diptera: Culicidae) in Thailand and Puerto Rico: Blood Feeding Frequency THOMAS W. SCOTT, PRIYANIE H. AMERASINGHE, 1 AMY C. MORRISON, LESLIE H. LORENZ, 2 GARY G. CLARK, 3 DANIEL STRICKMAN, 4 PATTAMAPORN KITTAYAPONG, 5 AND JOHN D. EDMAN 6 Department of Entomology, University of California, Davis, CA 95616 J. Med. Entomol. 37(1): 89Ð101 (2000) ABSTRACT We used a histologic technique to study multiple blood feeding in a single gonotrophic cycle by engorged Aedes aegypti (L.) that were collected weekly for 2 yr from houses in a rural village in Thailand (n = 1,891) and a residential section of San Juan, Puerto Rico (n = 1,675). Overall, mosquitoes from Thailand contained signiÞcantly more multiple meals (n = 1,300, 42% double meals, 5% triple meals) than mosquitoes collected in Puerto Rico (n = 1,156, 32% double meals, 2% triple meals). The portion of specimens for which frequency of feeding could not be determined was 31% at both sites. We estimated that on average Ae. aegypti take 0.76 and 0.63 human blood meals per day in Thailand and Puerto Rico, respectively. However, frequency of multiple feeding varied among houses and, in Puerto Rico, the neighborhoods from which mosquitoes were collected. In Thailand 65% of the mosquitoes fed twice on the same day, whereas in Puerto Rico 57% took multiple meals separated by  1 d. At both sites, the majority of engorged specimens were collected inside houses (Thailand 86%, Puerto Rico 95%). The number of blood meals detected was independent of where mosquitoes were collected (inside versus outside of the house) at both sites and the time of day collections were made in Puerto Rico. Feeding rates were slightly higher for mosquitoes collected in the afternoon in Thailand. Temperatures were signiÞcantly higher and mosquitoes signiÞcantly smaller in Thailand than in Puerto Rico. At both sites female size was negatively associated with temperature. Rates of multiple feeding were associated positively with temperature and negatively with mosquito size in Thailand, but not in Puerto Rico. Multiple feeding during a single gonotrophic cycle is a regular part of Ae. aegypti biology, can vary geographically and under different climate conditions, and may be associated with variation in patterns of dengue virus transmission. KEY WORDS Aedes aegypti, multiple blood feeding, histology, Thailand, Puerto Rico FEEDING BEHAVIOR OF adult female Aedes aegypti (L.) is unusual compared with most other mosquitoes (Clements 1992), because they frequently take 1 blood meal during each gonotrophic cycle (reviewed in Scott et al. 1993a, b)Ña behavior we refer to as multiple feeding. Moreover, they seldom feed on plant sugar compared with male Ae. aegypti and females of most other mosquito species (Edman et al. 1992, Van Handel et al. 1994, Martinez-Ibarra et al. 1997, Costero et al. 1999). When closely associated with humans, which is most often the case for the domestic form of this species (Christophers 1960), females feed almost exclusively on human blood (Scott et al. 1993b) and appear to use blood as their sole source of nutrients for reproduction and synthesis of energy reserves (Van Handel et al. 1994; Naksathit et al. 1998a, b; L. C. Harrington, unpublished data). Multiple meals within a single gonotrophic cycle are necessary to avoid star- vation (Costero et al. 1999). Results from studies that used life table parameters to examine Þtness effects of diet demonstrated that cohorts of female Ae. aegypti fed only human blood had higher net replacement rates and intrinsic rate of growth than cohorts fed human blood plus sugar (Scott et al. 1997, Costero et al. 1998a, Naksathit and Scott 1998, Morrison et al. 1999). There appears to be a selective advantage for females that feed only on human blood. Restricting their diet to human blood increases human contact (Canyon et al. 1999; L. C. Harrington, unpublished data) and, therefore, the potential for spread of den- gue and yellow fever viruses. To examine more closely the phenomenon of mul- tiple feeding, we applied a histologic technique de- veloped by Romoser et al. (1989) to Ae. aegypti (Scott et al. 1993a). Laboratory standardization experiments and examination of Þeld-caught specimens demon- strated that the technique can be used for longitudinal, community-wide surveys of multiple feeding by this species. Limitations of the procedure are that it de- 1 Department of Zoology, University of Peradeniya, Peradeniya, Sri Lanka. 2 Department of Entomology, University of Maryland, College Park, MD 20742. 3 Dengue Branch, Division of Vector-Borne Infectious Diseases, NCID, Centers for Disease Control and Prevention, 2 Calle Casia, San Juan, PR 00921Ð3200. 4 Department of Entomology, Walter Reed Army Institute for Re- search, Washington, DC 20307Ð5100. 5 Department of Biology, Mahidol University, Bangkok, Thailand. 6 Department of Entomology, University of Massachusetts, Am- herst, MA 01002. 0022-2585/00/0089Ð0101$02.00/0  2000 Entomological Society of America Downloaded from https://academic.oup.com/jme/article/37/1/89/858778 by guest on 05 November 2021