# Presentation: 695815

## Trigger Events for Mosquito Adulticide Applications in Massachusetts in 2001

**Massachusetts Department of Public Health**

## Decisions Regarding Adulticiding in MA

**Local government/health dept. makes decision regarding mosquito control, unless Governor declares a state of emergency (on advice of MDPH)**
**In general, role of MDPH is to provide guidance and data to advise and inform on risk of disease**
**In the case of an emergency (significant outbreak), MDPH may direct mosquito control, larvacide and adulticide**

## WNV Guidance for 2001

**For 2001, WNV prevention & control guidance developed by process involving MDPH, local health depts., mosquito control districts, academic experts, etc.**
**MA already had plan for EEE; was expanded/modified**
**Resulting matrix similar to CDC’s guidance for 2001 and to guidance developed by many other states**

## Risk Categories for Human Disease

**No current or prior year activity**

**No current activity (impacted area)**

**WNV-infected bird**

**WNV in birds/bird-biting mosquitoes**

**Signif. risk indicators positive**

**Locally-acquired human case**

**Multiple human cases**

**1**

**2**

**3**

**4**

**5**

**6**

**7**

## 5:  Significant Risk Indicators Positive(high risk of human disease)

**Definition**
**identification of continued high or increasing numbers of WNV-infected birds, rising or high WNV minimum infection rates in mosquitoes, and a WNV-positive pool of mammal biting mosquitoes, or laboratory confirmed WNV in a horse**
**Communication (cat. 4 plus)**
**Multi-media press release**

## 5:  High Risk of Human Disease

**Communication, cont.**
**intensify public education on personal protection measures**
**special messages for areas with vulnerable populations**
**advisory information provided on spraying**
**Surveillance & Control (cat. 4 plus)**
**review current situation in area and consider ground-based adulticiding**
**town or city may request to preempt private property ‘no spray’ requests**

## 5:  High Risk of Human Disease

**Surveillance & Control, cont.**
**measure treatment effect of pesticide use if mosquito adulticiding is used**
**Assessment & Options (cat. 4 plus)**
**when a trend of increasing or significant WNV activity is identified, MDPH will confer with local health officials to determine if the risk of human disease warrants a recommendation for adult ground-level mosquito control; factors to consider include the time of year, mosquito population abundance, and proximity of virus activity to at-risk populations**

## 6:  Locally-Acquired Human Case(high probability of human outbreak)

**Communication (cat. 5 plus)**
**Public Health Alert status**
**Surveillance & Control (cat. 5 plus)**
**review current situation in area and consider ground-based adulticiding**
**town or city may preempt private property ‘no spray’ requests if approved**
**statewide active horse and human surveillance**

## 6:  High Probability of Human Outbreak

**Surveillance & Control, cont.**
**enhanced passive surveillance for adverse events related to adulticiding**
**Assessment & Options (cat. 5 plus)**
**if surveillance indicates a continuing risk of human disease and potential for an outbreak, MDPH recommends ground-based adult mosquito control in a community and contiguous areas**
**areas to be treated are selected based on mosquito surveys that identify human-biting mosquitoes**

## 7:  Multiple Human Cases(human outbreak in progress)

**Communication (cat. 6 plus)**
**Public Health Alert status (by request, MDPH will designate high-risk areas where private ‘no spray’ requests may be preempted by local officials based on this risk level)**
**recommend restriction of group outdoor activities**
**Surveillance & Control (cat. 6 plus)**
**continual reassessment of recommendations for ground-based adulticiding**

## 7:  Human Outbreak in Progress

**Surveillance & Control, cont.**
**consideration of aerial adulticiding based on risk of human disease, if risk of disease transmission is widespread**
**Assessment & Options (cat. 6 plus)**
**MDPH recommends curtailment of group outdoor activities in areas of intensive virus activity, and use of ground-based adult mosquito control**
**MDPH will confer with local health agencies to discuss the use of intensive mosquito control methods**

## 2001 WNV Guidance

**Overall, more conservative with respect to adulticiding than recommendations for 2000**
**Stresses prevention, with source reduction, larvaciding and education/personal protection**
**Implementation meant to be flexible:**
**With respect to time of season (date)**
**With respect to community**

## 2001 WNV Guidance, cont.

**Allows range of responses to same indicators**
**Factors to consider include:**
**The time of year**
**Mosquito population abundance**
**Proximity of virus activity to at-risk populations**
**Intensity and trend of viral activity**

## WNV Surveillance Data

**Avian, mosquito, equine, and human**
**Provided directly to local health depts.**
**Posted daily to website – for public and media**
**Monitored and interpreted by MDPH (incl. dead bird/crow density assessment)**

## 2001 WNV Experience

**WNV-positive birds found earlier in season**
**WNV-positive birds found over wider area**
**WNV-positive mosquitoes found over wider area (mostly bird-biters)**
**No indicators for adulticiding triggered in July/August/early September**

- WNV-Positive Birds in 2000 and 2001
- Massachusetts

## 2001 Experience, cont.

**Two adjacent towns chose to spray (with ground-level adulticide) a shared area with intense WNV activity; was a local decision**
**Sept. 11 and subsequent BT events led to significant diversion of public, media and public health attention from WNV**

## 2001 Experience, cont.

**MA had 45 WNV-positive horses in 2001 but earliest confirmed case was in mid-Sept, with press release on Sept. 12**
**MA had one human case of EEE; confirmed Sept. 17**
**MA had three human cases of WNV; first case confirmed in early Nov.**

## MA 2001 Human WNV Cases

**3 laboratory-confirmed cases**
**Fever, headache, muscle weakness, mental confusion, seizures; meningo-encephalitis or encephalitis**
**1 fatality**
**Males, ages 70, 72, and 89**
**Residents of Woburn, Dartmouth and Acushnet**
**Onsets between 9/15/01 and 11/05/01**

## 2001 Experience, cont.

**Prospectively, the horse and human cases were reported well beyond viable time for adulticiding**
**Retrospectively, density and other triggers were not met prior to the horse or human reports (to permit pre-emptive spraying)**

## Lessons From 2001

**Need to expand time period of concern well into Fall if weather is mild**
**Unclear implication with respect to mosquito control, since generally can’t adulticide during these months**
**Prospective assessment of dead bird/crow density needs a geographic correlate smaller than county but larger than town**