Last update: 28 June 2004

Congratulations to Dr. Bill Reisen, recipient of the
2004 Academic Federation Award for Excellence in Research!
Please click here for news article:

"William Reisen, an internationally known expert on mosquito diseases, was chosen for the Academic Federation Award for Excellence in Research."

The California Applications Program and California Climate Change Center are studying the relationships between climate and human health. In collaboration with several groups of outstanding doctors and scientists, CAP/CCCC are exploring how variations in our medium-range weather patterns to long-range climate patterns may play a role in the onset, frequency and longevity of human health problems. Vector borne diseases and Kawasaki Disease are two areas CAP/CCCC are currently researching.

Kawasaki disease has become the most common cause of acquired heart disease in children

CAP/CCCC are researching a possible link between climate and Kawasaki Disease with a group led by Jane C. Burns, MD, Professor of Pediatrics with the University of California, San Diego. More information about the Kawasaki Disease Research Program can be found at http://www-pediatrics.ucsd.edu/research/disease/kdresrc.htm

What is Kawasaki Disease?

Kawasaki disease is an inflammation of the child's blood vessels. The most important blood vessels involved are those of the heart, including the coronary arteries. If Kawasaki disease is not recognized and appropriately treated within 10 days, the risk for permanent heart damage increases. Children can die from heart problems during this illness. They can also die from heart attacks later in childhood or as young adults. Early treatment is effective in preventing this, but first Kawasaki disease must be recognized.

Kawasaki disease is an uncommon but important cause of fever in children. It was first noticed in Japanese children following World War II. While it is more common among the Japanese, we now know that it occurs in all racial groups, primarily in children younger than 5 years of age. Sometimes Kawasaki disease appears in clusters of children. An infectious agent is suspected although the cause is unknown.

July 2004
West Nile Virus in California
Emerging Infectious Diseases, serial on the Internet, to be released August 2004
W. Reisen, H. Lothrop, R. Chiles, M. Madon, C. Cossen, L. Woods, S. Hustad, V. Kramer and J. Edman.
Available from: http://www.cdc.gov/ncidod/EID/vol10no8/04-0077.htm

West Nile virus (WNV) was first detected in California during July 2003 by isolation from a pool of Culex tarsalis collected near El Centro, Imperial County. WNV then amplified and dispersed in Imperial and Coachella Valleys, where it was tracked by isolation from pools of Cx. tarsalis, seroconversions in sentinel chickens, and seroprevalence in free-ranging birds. WNV then dispersed to the city of Riverside, Riverside County, and to the Whittier Dam area of Los Angeles County, where it was detected in dead birds and pools of Cx. pipiens quinquefasciatus. By October, WNV was detected in dead birds collected from riparian corridors in Los Angeles, west to Long Beach, and through inland valleys south from Riverside and to San Diego County. WNV was reported concurrently from Arizona in mid-August but not from Baja, Mexico, until mid-November. Possible mechanisms for virus introduction, amplification, and dispersal are discussed.

April 2002
CAP contribution to January 2002 MVCAC conference "Climate variability and encephalitis epidemiology":

Climate linkages to female Culex Cx. tarsalis abundance in California

August 2001

CAP initial analysis of Kern County Mosquitos

The vector-borne group of diseases is made up of organisms that spend part of their life inside a mosquito, flea, tick or other arthropod, and the other part inside a vertebrate. The arthropod (or "vector") picks up the disease agent when it bites a sick or infected host, and then carries it to one or more new hosts during its next blood meals.

CAP is reasearching a links between climate and vector borne diseases with a group led by Bill Reisen, Arbovirus Research Station, Bakersfield, CA. Working with Bill is Bruce Eldridge, Director of the UC Mosquito Research Program in the Department of Entomology at the University of California, Davis. Bruce maintains a web resource for mosquito and vector control in California which can be found at http://mosqnet.ucdavis.edu/

The image below shows the the transmission cycle for Western Equine Encephalitis (WEE). Encephalitis is generally involved in a mosquito-bird cycle with both hosts serving as reservoirs, but humans or horses may be accidental end point. Encephalitis is a viral disease that affects the central nervous system and causes an inflammation of the brain. The different encephalitis strains are caused by different viruses but are all transmitted by the bite of a mosquito. Following infection, symptoms range from inapparent (no disease) to encephalitis and death.

More information about vector borne disease can be found at the Marin/Sonoma Mosquito and Vector Control District web site (an excellent source of information): http://www.msmosquito.com/

Extracted from "Improved Detection of Mosquito Borne Encephalitis Activity in California" by Bill Reisen

THE DISEASE

Western equine (WEE) and St. Louis (SLE) are forms of encephalitis caused by viruses that persist in nature within a silent cycle involving the mosquito Culex tarsalis and several species of wild birds (especially house finches). Humans and horses are infected incidentally by mosquito bite. Following infection, symptoms range from inapparent (no disease) to encephalitis and death.

THE EMERGING PROBLEM

Currently, there is no cure following infection, and intervention focuses on mosquito abatement and horse vaccination. Measuring of the level of mosquito abundance and virus transmission among birds is critical for forecasting the risk of human and horse infection and focussing mosquito control. However, despite the existence of a state-wide surveillance system and the combined control efforts of 52 agencies with a combined budget of >$60,000,000, the activity of mosquito-borne encephalitis viruses has increased in California during the past decade. WEE is now active each year in the Central Valley and in the irrigated valleys of the southeastern desert (Imperial and Coachella Valleys, lower Colorado River). SLE persists in the Los Angeles basin and southeastern California. An expanding non-immune human population residing in close proximity to existing or newly-formed wetlands where mosquito control is limited can only exacerbate this emerging problem.

CURRENT PROGRAM

A state-wide Encephalitis Virus Surveillance (EVS) program currently integrates the efforts of the California Department of health Services (CDHA), members of the Mosquito and Vector Control Association of California (MVCAC), and the Center for Vector-borne Disease Research at University of California, Davis (UCD). Weather data and water availability from scattered sources are monitored and interpreted locally by MVCAC personnel. Mosquito abundance is monitored by light and other traps by MVCAC. Virus activity in the bird cycle is detected by UCD by testing pools of mosquitoes for infectious virus and by CDHS by testing the blood of sentinel chickens for antibodies. Horse and human cases are detected by health care providers who must recognize mosquito-borne viruses as the possible cause for the illness and request appropriate laboratory tests which are done free by the CDHS. Mosquito abundance and virus activity is reported weekly by fax/email to all participants and interested organizations by the CDHA.

RESEARCH TOWARD A MODEL SYSTEM

Research upon which the current EVS system is based was largely completed in the 1960s. Although selected aspects have been improved since that time, there has been no focussed effort to modernize the current system. In 1997 UCD with integrated financial support from selected MVCAC members and grants the University-wide Mosquito Research Program, the CDC and NIH and with collaboration by MVCAC members and the CDHS launched a 5 year research project targeting 5 areas of the EVS program:

1.Human and horse cases. Recent serological surveys indicate low level annual infection of humans by SLE and to a lesser extent WEE, but clinical cases are detected and/or reported by health care providers, even from areas supporting elevated virus activity.

2.Viral activity. We have minimal data to relate seroconversion rates in chickens and virus infection rates in mosquitoes to virus infection rates in wild bird populations. To facilitate detecting infection in wild birds, we developed a new assay that has allowed us to rapidly and inexpensively test any bird sera for any virus.

3.Mosquito abundance. Light traps currently are the method of measuring mosquito abundance; however, effectiveness has been compromised recently by increased levels of background illumination due to security lighting, expanded residential housing, and decreased mosquito abundance. Our research plans to launch an Integrated Mosquito Sampling Program that combines several collection methods to enhance detection of important species in specific habitats.

4.Analyses, prediction and reporting. Current reporting consists of a weekly fax or email message listing human and horse cases, positive sentinel chickens, and virus isolations from mosquitoes during the previous week. There is no archival system. Interpretation and analyses largely are left to report recipients. In 1997, UCD and MVCAC developed a geographical information system to record sentinel chicken flock and mosquito pool collection locations, and integrated these data with mapping software into the world wide web (WWW) or internet access. At a glance, the spatial pattern of virus activity is delineated at the state and then local levels. Data also will be permanently archived and available by WWW to California, US government and international agencies. Eventually we hope to interface this system with weather and water data and predictive models to "forecast" virus activity based on sensitive predictive variables

5.Weather and water. Weather currently is recorded electronically at a series of remote California Irrigation Management Information System (CIMIS) and National Oceanographic and Atmospheric Association (NOAA) stations. These data are managed at UCD with WWW access. Additional data on snow pack and agricultural irrigation are available but scattered. We plan to develop appropriate data bases that interface with simulation models to express these data into terms of mosquito abundance, virus activity and the risk of human and horse cases.