THE ABUNDANCE AND INFECTION STATUS OF ANOPHELES spp. MOSQUITOES AT THREE SITES IN LOUDOUN COUNTY, NORTHERN VIRGINIA

• Main Author: Krishnan, Priya
• Format: Others
• Published: VCU Scholars Compass 2011
• Subjects: Biology; Life Sciences
• Online Access: http://scholarscompass.vcu.edu/etd/319; http://scholarscompass.vcu.edu/cgi/viewcontent.cgi?article=1318&context=etd

Malaria is a re-emerging infectious disease with approximately half of the world's population at risk. In the US, since the 1950’s the Center for Disease Control (CDC) has been reporting between 1,000 and 1,500 cases of malaria every year. A majority of these cases were among US travellers and were attributed to Plasmodium falciparum. In August 2002, two cases of human malaria due to Plasmodium vivax were reported in Loudoun County, Northern Virginia. The Center for Disease Control and Prevention concluded that these cases were acquired locally. This was because of an absence of other risk factors such as international travel, and blood transfusion. Pools of Anopheles quadrimaculatus and Anopheles punctipennis collected in Loudoun County, Northern Virginia in 2002 tested positive for P. vivax subtype 210 indicating local transmission of malaria in the area. The purpose of this study is two-fold: 1) to determine the abundance of blood-fed Anopheles mosquitoes in the three sites close to the 2002 local transmission of human malaria in Loudoun County, Northern Virginia, and 2) to determine the infection status of the blood-fed Anopheles mosquitoes collected in the area. We observed a significant difference in the total abundance of Anopheles quadrimaculatus and Anopheles punctipennis at all the three sites, with Anopheles quadrimaculatus being more abundant. We also found a significant difference in the total abundance of Anopheles quadrimaculatus across the years at each of the three sites. All the pools collected in 2009 and 2010 tested negative for human Plasmodium parasites. The pools collected in 2010 tested negative for avian Plasmodium and Haemoproteus parasites. However, in 2009, 20 (28%) pools out of 71 tested positive for avian Plasmodium and Haemoproteus parasites. Four (20%) pools tested positive for avian Plasmodium, three of which were composed of Anopheles quadrimaculatus and were collected at Algonkian Regional Park while, one pool of Anopheles punctipennis was collected at Youngs Cliff. In addition, one (5%) pool composed of Anopheles quadrimaculatus and collected from Algonkian Regional Park tested positive for Haemoproteus. Eleven (55%) pools tested positive for both Haemoproteus and Plasmodium. Of these, four pools were composed of Anopheles quadrimaculatus and were collected from Algonkian Regional Park, two pools composed of Anopheles quadrimaculatus and one pool composed of Anopheles punctipennis were collected from Youngs Cliff. Lastly, four pools collected at Potomac Drive were composed of Anopheles quadrimaculatus. In summary, Algonkian Regional Park showed a high number of mosquitoes with malarial parasites. The maximum likelihood estimation (MLE) of mosquito infection rates based on the Biggerstaff (2006) method showed that among the three sites Youngs cliff had the overall highest infection rate (74.50%) for Anopheles mosquitoes compared to Algonkian Regional Park (53.86%) and Potomac drive (25.01%). An. quadrimaculatus had a higher infection rate compared at Algonkian Regional Park (57.95%) and Potomac drive (32.56%) compared to An. puncipennis (0%), while at Youngs cliff An. puncipennis had a higher infection rate (182.88%) compared to An. quadrimaculatus (56.06%).