Lab Matters Spring 2018 - Page 18

from the bench Louisville Expands Arbovirus Surveillance, Streamlines Mosquito Testing By Kim Krisberg, writer Every minute counts when trying to stop a disease outbreak. Especially when that disease can cause severe birth defects and lifelong health problems. “We knew it was coming,” said Leslie Wolf, PhD, referring to the 2015 Zika outbreak in Brazil. “We’re the only public health lab in the state that tests mosquitoes. …We needed to beef up our capacity not only to do our own testing, but if other counties needed help, we wanted to be ready.” Wolf is the laboratory technical director in Kentucky’s Louisville Metro Department of Public Health and Wellness Laboratory, which helps monitor hundreds of community sites throughout the metro area for mosquito-borne disease. The resulting data serves as a critical foundation for the agency’s mosquito control efforts, essentially providing a map of potential disease threats and pinpointing neighborhoods at heightened risk of transmission. Such control efforts are hardly new for the agency—the Louisville public health department has been operating its Mosquito Control Program for 60 years—but the emergence of Zika and its associated birth defects brought a new urgency to the need to expand and strengthen the lab’s mosquito surveillance capacity. To get ready for Zika’s arrival in the US, the Louisville lab upgraded its instrumentation and testing protocols. The result: the lab not only expanded the number of mosquito-borne diseases it monitored, it also shaved a full day off its mosquito testing process, giving responders a new advantage in the event of an outbreak. “We wanted to get results back to our mosquito control colleagues so they could respond in as real-time as possible,” Wolf said. Wolf’s colleagues in the agency’s Mosquito Control Program typically target more than 300 sites in the Louisville metro area for ongoing mosquito control from March 16 LAB MATTERS Spring 2018 Before the upgrades, Wolf said staff could test less than a dozen pools of mosquitoes at a time for West Nile. After the upgrades, lab staff could test mosquitoes for West Nile as well as Zika virus and Saint Louis Encephalitis. through November. Throughout that time, specially trained staff set out and collect mosquito traps on a weekly basis. They then sort the mosquitoes by genus, species, location and date collected and deliver the vials of insects to the public health lab for RNA extraction and testing. Prior to implementing the new testing methods, Wolf said the lab only screened mosquitoes for West Nile virus, human cases of which have been reported in Kentucky every year for the last 15 years. The US Centers for Disease Control and Prevention (CDC) reports 162 cases of West Nile virus in Kentucky between 1999 and 2016. And in August 2017, local public health workers found West Nile-infected mosquitoes in six Louisville ZIP code areas. But with the advent of Zika, “we had to boost our capacity,” Wolf said. As funding became available, the Louisville public health lab began upgrading its equipment, bringing on a higher-capacity PCR instrument in 2015 and a higher-throughput extractor in 2016. The changes made a big difference. Before the upgrades, Wolf said staff could test less than a dozen pools of mosquitoes at a time for West Nile. After the upgrades, lab staff could test mosquitoes for West Nile as well as Zika virus and Saint Louis Encephalitis. As for throughput, the lab went from having an extraction instrument that did eight mosquito pools at a time to one that does 96 pools at a time; its new PCR system went from testing 32 samples at a time to 96 at a time. The improvements also shortened the testing process by a day — from three days to two. And all that was accomplished without putting extra stresses on lab staff. In fact, Wolf said the old method with its low throughput meant staff were constantly having to load sample pools throughout mosquito season while still keeping up with their year-round duties. But with the new instrumentation, Wolf said the lab was able to both streamline the mosquito testing process and expand its surveillance abilities. “Not only were we able to decrease our turnaround time, but we’re able to do more testing without increasing our staff,” she said. The new streamlined process was up and ready to go by the 2016 mosquito season— the first year that a locally transmitted case of Zika virus was identified in the US. In 2016, Wolf said the lab tested 300 mosquito pools between July and October, with 18 positive for West Nile virus and none positive for Zika or Saint Louis Encephalitis. During the 2017 mosquito season, the lab tested a bit fewer at about 250 pools, which Wolf said is likely due to having fewer seasonal workers available to trap, collect and sort the insects for testing. Beyond testing for more diseases more quickly, the lab’s upgrades also enhanced its verification capacity. Previously, Wolf said the lab didn’t have the ability to confirm its mosquito testing results— the lab tested using validated methods and colleagues in mosquito control and environmental health acted on those PublicHealthLabs @APHL APHL.org