2011 Annual Report - Sacramento-Yolo Mosquito & Vector Control ...

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SurveillanceEncephalitis virus surveillanceSentinel ChickensIn an effort to use all available surveillance tools and increase the chances of early detection ofarbovirus activity, the District uses sentinel chickens as part of the encephalitis virus surveillanceprogram. Chickens usually don’t get sick when infected with West Nile virus and are deadendhosts for it, meaning they do not infect mosquitoes when bitten again by them. Moreover,chickens stay inside a coop in a fixed area and the presence of antibodies in their bloodindicates local virus transmission. Therefore they are used by many mosquito control districtsin their surveillance programs and may serve as an early indicator of local arbovirus activityin an area.In 2011, the District maintained a total of 91 chickens distributed in 13 flock sites withinSacramento and Yolo Counties. Approximately 2,500 blood samples were collected fromApril 28 through October 31, 2011 from the 7 chickens in each of the 13 flock sites. Sampleswere tested for the presence of antibodies towards SLE, WEE, and WNV viruses. The first WestNile virus-positive chicken sample was detected on a collection made on August 15, 2011. Atthe end of the sampling period, antibody conversions had been found in 2 of the 13 chickenflocks with a total of 7 chickens positive for antibodies towards West Nile virus.Need Caption2011 SENTINEL CHICKEN TESTSSACRAMENTO COUNTYFlock Location No. chickens WEE positive SLE positive WNV positiveElk Grove 7 0 0 2Galt 7 0 0 0Hood 7 0 0 0Natomas 7 0 0 0Wilton 7 0 0 5Sacramento 7 0 0 0Folsom 7 0 0 0Need CaptionRanchoMurieta7 0 0 0Pocket 7 0 0 0YOLO COUNTYFlock Location No. chickens WEE positive SLE positive WNV positiveWinters 7 0 0 0Davis 7 0 0 0Esparto 7 0 0 0Need CaptionWoodland 7 0 0 010 Sacramento–Yolo Mosquito & Vector Control District
SurveillanceWild BirdsThe District’s wild bird surveillance program monitors the presence of antibody for encephalitisvirus in the avian population in rural and suburban habitats. The purpose of the program isto aid in the identification of local enzootic virus transmission, the determination of avianhosts, their residency, mobility, longevity, and mortality by maintaining records of changesin abundance, age structure, and immunity. Data provided by this program contribute to ourunderstanding of the local infection cycle in birds and mosquitoes, and assist in the assessmentof the risk of virus transmission to residents. The program was initiated in the spring of 1996to monitor the endemic Western Equine Encephalomyelitis virus and has since also providedthe first evidence of West Nile Virus transmission in Sacramento County and tracked the virusas it rapidly moved into the resident bird population and became established.In order to capture wild birds, the District uses mist nets and seed-baited traps with authorizationfrom the U.S. Geological Survey, Bird Banding Laboratory in Laurel MD, and the CaliforniaDepartment of Fish and Game. Each captured bird is aged, sexed, weighed, measured,banded, and a small blood sample (0.1ml/10g wt.) is collected to test for the presence ofarbovirus antibody. Birds are released at the location of capture and samples are broughtinto the District’s laboratory, where they are tested by an enzyme-linked immunosorbent assay(ELISA) that identifies antibody to the different viruses.The use of wild birds as an arbovirus surveillance tool has provided a serological history ofWNV in our District. The wild bird surveillance program is maintained through a cooperativeagreement and with volunteer personnel support from the US Fish and Wildlife Service on theStone Lakes National Wildlife Refuge. In 2011, a total of 711 blood samples were tested from54 bird species. The collected sera were tested for antibody to Western EncephalomyelitisVirus (WEEV), St. Louis Encephalitis Virus (SLEV), and West Nile Virus (WNV). Only antibodyfor WNV was detected in birds sampled in 2011. Overall, WNV antibody was detected in0.8% of the samples.WNV Seropositive Wild Birds in 2011BirdPositive detections (total sampled)Western scrub-jay 1 (5)Snowy egret 1 (6)Great-tailed grackle 1 (2)Song sparrow 1 (108)Green heron 1 (6)Birds are released at the location of capture andsamples are brought into the District’s laboratory.2011 Annual Report11
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Page 10 and 11: Surveillance6.5%9.2%.9%13.1%America
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Page 30 and 31: Financial StatementsSacramento-Yolo
Page 32: Sacramento County8631 Bond RoadElk

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