The Breteau (or Breteau) index is an entomological metric used to quantify the density of mosquito‑breeding sites in a defined area, primarily for the surveillance of Aedes species that transmit dengue, Zika, chikungunya, and yellow fever viruses. It is calculated as the number of water‑holding containers positive for mosquito larvae or pupae per 100 houses inspected:
$$ \text{Breteau Index (BI)} = \frac{\text{Number of positive containers}}{\text{Number of houses inspected}} \times 100 $$
The index is one of three classic “Stegomyia” indices, alongside the House Index (percentage of houses with positive containers) and the Container Index (percentage of containers infested). Because it incorporates both the number of positive containers and the number of houses surveyed, the Breteau index is often regarded as the most informative single indicator of vector abundance for public‑health decision‑making.
Historical background
The metric was introduced in the mid‑20th century as part of vector‑control programs in Southeast Asia and the Caribbean. Although the precise individual who first formulated the index is not widely documented in readily accessible encyclopedic sources, the name “Breteau” is derived from a French‑speaking entomologist who contributed to early dengue‑surveillance methodology. The index has been incorporated into World Health Organization (WHO) guidelines for dengue monitoring and is routinely employed by national public‑health agencies worldwide.
Application and interpretation
- Thresholds: WHO and regional health authorities have proposed operational thresholds for dengue risk. A Breteau index ≤ 5 is generally considered indicative of low transmission risk, whereas values ≥ 10–20 suggest heightened risk and may trigger intensified vector‑control measures. Specific thresholds can vary by locale and vector species composition.
- Surveillance: The index is obtained through systematic larval surveys of domestic and peri‑domestic environments. Survey teams inspect a representative sample of households, record all water‑holding containers, and determine the presence of immature Aedes stages.
- Program evaluation: Changes in the Breteau index over time are used to assess the impact of interventions such as source‑reduction campaigns, insecticide spraying, and community education.
Limitations
While widely used, the Breteau index has limitations. It reflects immature mosquito presence rather than adult vector density, which more directly drives disease transmission. Environmental heterogeneity, seasonal variation, and sampling bias can affect its reliability. Consequently, many recent studies combine the Breteau index with additional entomological and epidemiological indicators to improve predictive power for outbreaks.
References (representative)
- World Health Organization. “Monitoring and evaluation of dengue vector control programmes.” (WHO technical documents, 1998, 2012).
- Breteau index definition and use in entomological surveillance literature (e.g., Aedes aegypti larval indices and risk for dengue epidemics, Emerging Infectious Diseases, 2005).
- Global Vector Hub, “Larval Surveys” (guidance on calculation of the Breteau index).
The Breteau index remains a cornerstone of vector‑borne disease surveillance, providing a standardized, quantitative basis for public‑health actions aimed at reducing the burden of dengue and related arboviral diseases.