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Date: Wed, 13 Nov 2002
Posted by: Dominick Ninivaggi (Dominick.Ninivaggi@co.suffolk.ny.us)

It is not possible to conduct efficacy and non-target studies whenever control is undertaken. Both types of studies require adequate baseline data, especially the non-target studies. You have to know the area that's going to be treated well in advance and look at it for some period of time before and after treatment. Operationally, that's rarely the case. Typically, treatment is undertaken in response to rapidly developing situations, and on a few days notice, at best. There's little time to gather baseline data. After treatment, it's very common for weather to change, confounding the ability to compare pre-spray and post-spray numbers. In addition, applications may be done when mosquito numbers are relatively low, because infection rates are high or other factors. This makes it difficult to get statistically adequate sample sizes. We make every effort to follow up after treatments, but it is no simple matter, especially when you sometimes have to choose between follow-up samples and checking out the latest situation to appear in your surveillance. I can tell you that no mosquito control program is so well funded that they can afford to throw out pesticide with no regard for whether it's working.

Non-target studies, particularly for insects, require very large sample sizes due to the inherent natural fluctuations in many non-target populations. They are best done under controlled conditions, rather than by trying to sample around operational events. Another approach is the use of modeling. The point I'm trying to make is that no one disputes the value of such studies, but they are inherently difficult due to the very nature of the problem. Suffolk County is planning to undertake studies that will attempt to address as many of these issues as possible, at a cost to local taxpayers that will exceed $4M. We have already done extensive monitoring in preparation for this study. I wouldn't mind seeing the State and the Feds kick in on this.

Robert Foster wrote:

Every time a local, state or federal health unit undertakes a mosquito control activity there is an opportunity to conduct studies to determine efficacy and non-target impacts.

Citizens Campaign for the Environment believes that it is responsible when public funds are used to justify efficacy and assumptions regarding non-target and human health impacts with concrete data.

Sufficient federal, state and local resources should be provided to accommplish this goal.

In New York State, legislation has been introduced to provide state funding to conduct the type of monitoring necessary to determine efficacy and non-target impacts.

Robert Foster
Program Director
Citizens Campaign for the Environment

norman robbins wrote:

Dear West Nile List-Servers,

As a scientist, I am greatly disturbed to read lengthy discussions and CDC or State recommendations for WNv actions that often appear to be based mainly on opinion rather than citations of statistical validation. As much as one prefers prospective studies, could a thorough and sophisticated CDC retrospective analysis of activities (e.g. larviciding, adulticiding in 1999-2002) and resulting mosquito density and human disease, shed some light on questions we will once again be debating in the next few months?

I encourage List-servers to revise or expand the following list of questions in the hope that a collated version can be signed by you and sent to CDC advocating that they use resources to investigate these issues. My sense is that the CDC people are not at all resistant to undertaking this analysis -- they just need outside advocacy to gain the resources.

QUESTIONS FOR CDC TO INVESTIGATE BY ANALYSIS OF WEST NILE DATA TO DATE:

What is the STATISTICAL EVIDENCE AND PROBABILITY RANGE (not opinion) that:

1. larviciding (at WHAT intensity and frequency) reduces mosquito populations (by species)?

2. URBAN adulticiding (at what intensity, frequency, area and method) reduces mosquito populations, by species and for how long?

3. there are (or are not) acute or chronic human health effects of urban adulticiding in typical ULV amounts and frequency?

4. certain types of public messages or policies are more or less effective than others in reducing urban standing water (residential, public spaces, etc.)

5. one or another type of surveillance (dead crows, gravid or C0-2/light traps, virus-positive mosquitoes, etc.) predicts human disease with what kind of probability range.

6. both gravid and C0₂/light traps are desirable for human disease prediction.

7. there is some level of mosquito density which predicts risk of animal or human disease and calls for more aggressive mosquito management

Norman Robbins
Shaker Heights (OH) West Nile Task Force

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