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Medical Entomology

What testing is ongoing in South Carolina to detect West Nile virus (WNV) and other mosquito-borne diseases?

S.C. DHEC has been testing for West Nile virus infections since 1999 in addition to other viral infections that are spread by mosquitoes. South Carolina’s surveillance program includes detection of WNV in birds, mosquitoes, mammals, and humans. S.C. DHEC’s surveillance to detect WNV focuses on the bird and mosquito components of the WNV transmission cycle. Detection of WNV in bird and mosquito populations helps health officials predict and prevent human and domestic animal infections. Equines (horses, donkeys, and mules) serve as effective sentinels because a high intensity of mosquito exposure makes them more likely to be infected than people.

Bird Surveillance

Dead bird surveillance appears to be the most sensitive early detection system for WNV activity. Certain species of birds, in particular corvids (e.g., crows and jays) are particularly sensitive to WNV. Due to public involvement in reporting dead bird sightings, dead wild birds are readily available over a much wider region than can be sampled by other surveillance methods. Dead bird surveillance can be used for early detection and ongoing monitoring of WNV transmission.

Please see Reporting Dead Birds for West Nile virus Testing for instructions and forms on how to submit a dead bird. Avoid handling live or dead birds with your bare hands. Use gloves or doubled plastic bags to pick up any dead birds you think might qualify for testing.

Mosquito Surveillance

While dead-bird-based surveillance has proven to be the most sensitive method of detecting WNV in an area, mosquito-based surveillance remains the primary tool for measuring the intensity of virus transmission in an area. Intensive mosquito-based surveillance may provide the earliest evidence of transmission in an area. It establishes information on potential mosquito vector species, provides an estimate of vector species abundance, and it gives information on virus infection rates.

Animal Surveillance

Equines (horses, donkeys, and mules) may be particularly useful sentinels or indicators in rural areas where dead birds may be less likely to be detected. Sick equines have been one of the earliest, if not the earliest, sentinels of WNV in some areas. Other animals might be tested as part of a general laboratory evaluation. West Nile virus is not considered routinely as a cause of disease or death in dogs, cats, livestock other than equine species, or other non-bird domestic animals, although rare infections do occur. S.C. DHEC partners with Clemson University Veterinary Diagnostic Center to test equines and other mammals.

Human Surveillance

Human-based surveillance assesses the public health impact of WNV disease, demonstrates the need for public health intervention programs, and identifies geographic areas in need of targeted interventions. S.C. DHEC’s Bureau of Laboratories supports the human surveillance for West Nile virus that is conducted by the Division of Acute Disease Epidemiology (DADE). Specifically, the Bureau of Laboratories provides virus isolation, molecular detection, and anti-West Nile virus testing services for humans suspected of having West Nile virus infections.

The 2005 Instructions for Physicians (pdf) outlines the clinical presentation of WNV disease, diagnostic testing available through S.C. DHEC, and specimen submission and reporting.

If you have questions after reading the vector-borne disease pages:

  1. Contact your county environmental health department.
  2. If you have additional questions after contacting your county health department, please e-mail: wnv@dhec.sc.gov.