I was privileged to return to the University of Wisconsin–La Crosse recently and presented a seminar on the worldwide pandemic of diseases (Yellow Fever, Dengue, Chikungunya and Zika) transmitted by Aedes aegypti mosquitoes.
In the absence of vaccines, mosquito control is the only way to combat these diseases.
Aedes aegypti was controlled in the Americas to prevent Yellow Fever. In the absence of cases, mosquito control was drastically reduced. Aedes aegypti resurged with a vengeance, resulting in the current public health emergency.
During my visit, I was dismayed to learn that, in this time of budget austerity, the La Crosse County Vector Control Program is being dramatically reduced.
This is apparently due largely to the reduction in La Crosse encephalitis cases in La Crosse County. This is shortsighted; in the absence of vector control, La Crosse encephalitis cases will certainly surge.
I started working on the La Crosse virus while obtaining bachelor and master’s degrees from UW-L and a Ph.D. from UW-Madison. These studies were to determine how the newly emerged La Crosse virus was maintained in nature and why so many cases of La Crosse encephalitis were occurring in La Crosse. Later, I worked with Dr. Cameron Gundersen and others at the Gundersen Health System to develop rapid diagnostic tests for La Crosse encephalitis to aid physicians in prescribing the best care for seriously ill children. La Crosse encephalitis can be life threatening in children. Clearly, La Crosse virus infections need be prevented, and in the absence of a vaccine, the mosquito vector must be controlled.
Early studies revealed that La Crosse virus is transmitted in forested areas between chipmunks and squirrels by Aedes triseriatus mosquitoes, which are called tree-hole mosquitoes because, following a blood meal, the mosquito lays her eggs in tree-holes where larvae can develop and adults emerge. Humans become infected when they interrupt the cycle and are bitten by infected mosquitoes. Cases of La Crosse encephalitis increased dramatically in the 1960s with building of homes in forested areas, exposing children to the tree-hole mosquitoes. Discarded tires and other water-retaining containers near homes also brought the mosquito and children in contact.
Understanding the natural cycle of La Crosse virus led to the development of the La Crosse County Vector Control Program. This program, started in 1978 by David Geske (La Crosse County), Dr James Parry (UW-L), and Dr. Cameron Gundersen focused on control of Aedes triseriatus around homes where children had were infected, thereby protecting other children from infection. The program included a countywide effort to identify and remove tires and other mosquito breeding sites, and education on how to prevent La Crosse virus infections. It has been a very successful program. From 1975-1979, there were 27 cases of La Crosse encephalitis in the county. In 2010-2015, there were only three cases, but 39 would be expected based on the increased population in La Crosse County (80,268 in 1975 to 114,881 in 2010). Even more cases would be expected because of the many homes built in rural areas, thereby increasing the number of children at risk of infection.
The successes of the program caused neighboring counties to reach out to La Crosse County for help in controlling this serious disease. In the early 1980s, Vernon, Crawford and Monroe counties and Winona and Houston counties in Minnesota began to work as partners in a regional mosquito-borne disease program. These counties have also had a dramatic reduction in the number of La Crosse encephalitis cases. There is no doubt that vector control has been the major factor involved. I have always touted the successes of the La Crosse County Vector Control Program and the regional effort in reducing La Crosse encephalitis cases in the Driftless region.
Prevention of infection precludes the severe suffering experienced by infected children and is also very cost-effective. Treatment and care of just one child with severe La Crosse encephalitis greatly exceeds the vector-control budget. In addition, West Nile virus, tick-borne diseases and invasive mosquitoes pose new threats to human health. The citizens of La Crosse County and its public health officials should be very proud of their excellent program and preserve it. Don’t let the success of the program lead to its demise. Aedes triseriatus and La Crosse virus remain threats. Without the leadership of the La Crosse County Vector Control Program, the regional effort to contain this terrible disease will certainly falter.