Mosquito-borne disease advisories — Sebastian, Florida

The Florida Department of Health in Indian River County and the Indian River Mosquito Control District watch for mosquito-borne viruses around Sebastian, chiefly through 8 sentinel chicken flocks tested every week.

The DOH-Indian River Mosquito-Borne Diseases page states that the department partners with the mosquito control district to prevent the spread of mosquito-borne illness in the county, and that sentinel chickens are monitored and tested for exposure to arboviruses, the term for viruses carried by mosquitoes. The district maintains 8 flocks of 6 carefully raised chickens in cages located throughout the populated eastern half of Indian River County.

The surveillance program dates to 1978. The IRMCD Arbovirus Surveillance page says the district participates in a State-sponsored program of surveillance for St. Louis encephalitis, West Nile, and Eastern equine encephalitis viruses, and that this program has been in place since 1978. It has two parts: the sentinel flocks, which measure virus moving from mosquitoes to birds, and intensive monitoring of two representative populations of the principal vector mosquito, Culex nigripalpus, in different parts of Indian River County.

The roles are split. IRMCD, based at 5655 41st Street in Vero Beach, collects the weekly blood samples (IRMCD); a Florida Department of Health laboratory in Tampa tests the samples, and DOH-Indian River lists its Environmental Public Health office at 1900 27th St. in Vero Beach, phone 772-794-7440 (DOH-Indian River). The district’s spraying, impoundment and larval work is a separate subject covered on the mosquito control page.

Each Indian River County sentinel chicken gives a blood sample every week, and the test shows whether antibodies to the screened viruses are present, a measure of virus transmission from mosquitoes to birds.

DOH-Indian River explains why chickens are used: chickens are good sentinels and, like normal barnyard chickens, they are readily fed upon by mosquitoes. Each bird is tested for prior infection with St. Louis Encephalitis Virus, West Nile Virus, and Eastern Equine Encephalitis virus before it goes into the field (DOH-Indian River).

The IRMCD Sentinel Program page gives the routine: three times a week the flocks are checked for food and water and once a week blood is collected for arbovirus screening, and after 6 months the chickens are retired and replaced with new birds. The district says that this season it will begin independently screening weekly chicken blood serum for West Nile Virus using Enzyme-Linked Immunosorbent Assay (ELISA) testing, to provide fast results for control practices, while weekly samples still go to the state laboratory in Tampa to screen for St. Louis and Eastern equine encephalitis.

The mosquitoes are studied as well as the birds. The district’s Science Department dissects the ovaries of adult Culex nigripalpus every week (IRMCD), and its adult surveillance page says it deploys 25 CDC light traps throughout the county, plus BG Sentinel traps that target the domestic Aedes species that live near homes.

Indian River County surveillance results have reached the public through Florida Department of Health in Indian River County releases, such as the December 2015 release reporting West Nile Virus in a county sentinel flock.

The IRMCD Sentinel Program page explains how the results are read. By examining the blood serum of host birds and the mosquito vector species, the risk of disease transmission can be evaluated. The district adds two checks on the mosquitoes themselves: weekly ovary dissections of adult Culex nigripalpus, which help determine the age of mosquito populations, and aspirator collections of resting mosquitoes at the same sites, which show whether a new emergence has just occurred. Two sites are currently used to collect females with passive-baited traps for the dissections, and the in-house West Nile testing is meant to give fast results so control practices can be carried out.

The December 17, 2015 DOH-Indian River release shows the sequence. It said that due to high temperatures and rainfall, mosquitoes were still prevalent in Indian River County, and that this had led to recent detections of the West Nile Virus in a sentinel flock of chickens maintained in the county. The release named both the department and the Indian River Mosquito Control District, and it listed the department number, 772-794-7440, and the district number, 772-562-2393, for more information.

Formal Indian River County advisory notices for earlier years are posted by the state as PDF documents and are not summarized here; this section relies on the department’s HTML release and the district’s own pages.

Indian River County sentinel chickens give no early warning for dengue, chikungunya or Zika, and the district states that for those viruses the only indication in Florida will be the reporting of a human case.

The IRMCD Arbovirus Surveillance page states that, unlike the encephalitis viruses, there are no useful early detection monitoring programs for dengue, chikungunya, or Zika viruses. Since these viruses are transmitted from mosquito to man, the only indication of the virus in Florida will be the reporting of a human case.

For these viruses the district relies on case work. Human case investigation involves determining when and where a disease was contracted, and the district says a close working relationship with the local Florida Department of Health helps determine whether a case was acquired locally or was travel-related outside the county (IRMCD). Trap work fills part of the gap: the BG Sentinel traps described on the IRMCD adult surveillance page are used to watch the domestic Aedes species that live near homes and can carry dengue, chikungunya and Zika.

Indian River County’s record includes the 1990 St. Louis encephalitis epidemic, first recognized in the county, and West Nile detections in sentinel chickens since 2001 with no human West Nile case recorded locally.

The IRMCD St. Louis encephalitis page states that the 1990 epidemic was first recognized in Indian River County, which also experienced the highest impact of any affected county, with 19 confirmed cases despite a relatively low population. St. Louis encephalitis remains one of the three major arboviruses the district routinely screens for.

The IRMCD West Nile page says the virus was first detected in Indian River sentinel chickens in 2001, and many times in the following years, yet there has not yet been a human case of disease caused by West Nile virus in this county. Eastern equine encephalitis is rarer: the IRMCD EEE page states that EEEV is infrequently detected in Indian River County, with only one human EEE case recorded.

The state program also tracks the wider picture. The IRMCD Arbovirus Surveillance page posts weekly Florida Arbovirus Surveillance Reports, and the 2015 DOH-Indian River release listed West Nile, Eastern equine encephalitis, St. Louis encephalitis, malaria, chikungunya, and dengue among the illnesses under statewide surveillance.

Sebastian residents find mosquito-borne illness notices through DOH-Indian River Environmental Public Health at 772-794-7440 and the Indian River Mosquito Control District at 772-562-2393, which offers an email sign-up for advisory notices.

The IRMCD contact page lists the administrative office at 5655 41st Street, Vero Beach, FL 32967, phone 772-562-2393, and offers an email sign-up with options for Important Alerts, Newsletter and Advisory Notice. DOH-Indian River lists Environmental Public Health at 772-794-7440, fax 772-794-7447, 1900 27th St., Vero Beach (DOH-Indian River).

The 2015 DOH-Indian River release carried the Drain and Cover message, including draining standing water to stop mosquitoes from multiplying, with house gutters, boats under tarps and birdbaths among the examples.

Last verified: October 11, 2026, on the Indian River Mosquito Control District website.