What is a Vector Index?

As of 2016, Chester County is using the Vector Index method of using mosquito data to predict the West Nile Virus threat to humans. Here is a summary from “2013 West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control” at the CDC site, p. 18 (boldface added):

The Vector Index (VI) is an estimate of the abundance of infected mosquitoes in an area and incorporates information describing the vector species that are present in the area, relative abundance of those species, and the WNV infection rate in each species into a single index (Gujaral et al. 2007, Bolling et al. 2009, Jones et al. 2011). The VI is calculated by multiplying the average number of mosquitoes collected per trap night by the proportion infected with WNV, and is expressed as the average number of infected mosquitoes collected per trap night in the area during the sampling period. In areas where more than one WNV vector mosquito species is present, a VI is calculated for each of the important vector species and the individual VIs are summed to represent a combined estimate of the infected vector abundance. By summing the VI for the key vector species, the combined VI accommodates the fact that WNV transmission may involve one or more vectors in an area. Increases in VI reflect increases in risk of human disease (Bolling et al. 2009, Jones et al. 2011, Kwan et al. 2012, Colborn et al. 2013 in press) and have demonstrated significantly better predictive ability than estimates of vector abundance or infection rate alone, clearly demonstrating the value of combining information for vector abundance and WNV infection rates to generate a more meaningful risk index (Bolling et al. 2009). As with other surveillance indicators, the accuracy of the Vector Index is dependent upon the number of trap nights used to estimate abundance and the number of specimens tested for virus to estimate infection rate. Instructions for calculating the Vector Index in a system with multiple vector species present are in Appendix 2.

For the actual VI formula and a detailed example, see pp. 64-66 of the above Guidelines.

Risk analysis needed before spraying permethrin

Contributed by one of Dontsprayme’s consulting scientists, in response to spraying activity this summer

I am concerned about the recent decision to spray in an area of Chester County for West Nile carrying mosquitoes, considering what is currently known about permethrin, the availability of less toxic alternatives and methods for mosquito control, and the demonstrated resistance of mosquito populations to this pesticide. Even if there are some West Nile positive mosquitoes in the vicinity, has a risk analysis been done to see that the perceived benefits of spraying outweigh the long term risk to human health?

While permethrin was studied at length in 1994 by the US Army and found to be relatively safe, this early study should be taken in context: more American soldiers have died from insect-borne illness than of enemy fire. For troops deploying to tropical areas, and who have already willingly put their lives on the line for our country, permethrin is the lesser of two evils. Since the 1994 study, there has been a great deal of research into the toxicity of permethrin, and the picture grows more and more grim with the passing years. Work that supports the use of permethrin, such as the EPA’s cumulative risk assessment (2011)[1], is very thorough at the surface, but consider limited endpoints: specifically, those derived from the a priori known ways in which pyrethrins and pyrethroids disrupt neural function.

As complete as the EPA study seems to be, its flaw is in its failure to consider other endpoints besides neural function. A recent review article[2] identified 29 studies in which permethrin-induced toxicity was identified in various species (and cited a number of other studies where human toxicity was shown). It also goes into far more detail than the Army study about the mechanisms of toxicity in the various bodily systems.

From the article:

Although it was believed that PER showed low mammalian toxicity, an increasing number of studies have shown that PER can also cause a variety of toxicities in animals and humans, such as neurotoxicity (Carloni et al., 2012, 2013; Falcioni et al., 2010; Gabbianelli et al., 2009b; Nasuti et al., 2014, 2008, 2007b), immunotoxicity (Gabbianelli et al., 2009a; Jin et al., 2010; Olgun and Misra, 2006), cardiotoxicity (Vadhana et al., 2010, 2011a, 2011b, 2013), hepatotoxicity (Gabbianelli et al., 2004, 2013), reproductive (Issam et al., 2011), genotoxic (Turkez and Aydin, 2012, 2013; Turkez and Togar, 2011; Turkez et al., 2012), and haematotoxic (Nasuti et al., 2003) effects, digestive system toxicity (Mahmoud et al., 2012; Sellami et al., 2014b, 2015), anti-androgenic activity (Christen et al., 2014; Xu et al., 2008), fetotoxicity (Erkmen, 2015), and cytotoxicity (Hu et al., 2010) in vertebrates and invertebrates.

Additionally (Vadhana et al., 2013):

Early life environmental exposure to PER could play a critical role in the onset of age-related diseases (Carloni et al., 2012, 2013; Fedeli et al., 2013; Gabbianelli et al., 2013; Vadhana et al., 2011b). Previous findings demonstrate that early life pesticide exposure to low doses of the PER insecticide has long-term consequences leading to toxic effects such as cardiac hypotrophy, increased Ca2 ©≠ level and increased Nrf2 gene expression….

In fact, there is evidence that effects of this nature are transgenerational and that there are epigenetic changes that ensue due to exposure. What’s clear is that the pesticide research community has NOT signed off on the harmlessness of such pesticides to humans despite the EPA guidelines or material safety data sheets. 

In addition its toxicity, it’s also fairly clear that mosquitoes evolve resistance to permethrin and other pesticides relatively rapidly. From Ramkumar et al (2015), after exposure to permethrin, within 10 generations, the 50% lethal dose concentration (LC50) of permethrin increased 17-fold. 

Ramkumar, G., & Shivakumar, M. S. (2015). Laboratory development of permethrin resistance and cross-resistance pattern of Culex quinquefasciatus to other insecticides. Parasitology Research, 114(7), 2553–2560.

Research on West Nile carrying mosquitoes indicates that when field collected mosquitos were tested for pesticide resistance, in one case there was a 299-fold increase in dosage to reach the LC50.

Kasai, S., Shono, T., Komagata, O., Tsuda, Y., Kobayashi, M., Motoki, M., … Tomita, T. (2007). Insecticide resistance in potential vector mosquitoes for West Nile virus in Japan. Journal of Medical Entomology, 44(5), 822–829.

An alternative to using such pesticides is a larvicide, BT, which has been studied extensively. This appears to be safe at the moment (except for mega-doses, or deviant genetic strains), and is a champ at killing mosquito larvae. 

Ibrahim, M. A., Griko, N., Junker, M., & Bulla, L. A. (2010). Bacillus thuringiensis. Bioengineered Bugs, 1(1), 31–50.

So the question is: if permethrin has already been shown to be dangerous to animals and humans AND it’s been shown to have diminishing effects on mosquitoes, and there are alternative measures that work, why is there such a strong push to spray? One must remember that where spraying of this nature is used by the WHO, it is used as the lesser of two evils in regions where the risk of mosquito-borne illness and subsequent death or disability is high enough to justify its use. Are there enough cases of West Nile in our area that spraying is justified? Has there been enough sampling of mosquito populations? What is the correlation between the ratio of mosquitoes with West Nile and the number of diagnosed cases? Are larvicide or other control measures being optimally used?

As a scientist who teaches the physical sciences and who does health-related research, I’m struggling to understand how the data can possibly support a decision to spray.

[1] US Environmental Protection Agency; Office of Pesticide Programs. (2011). “Pyrethrins/Pyrethroid Cumulative Risk Assessment.” Retrieved from US Environmental Protection Agency.

[2] Xu Wang et al., “Permethrin-induced oxidative stress and toxicity and metabolism. A review,” Environmental Research, Volume 149, August 2016, Pages 86-104.

Chester County Health Department WNV releases, summer 2016

“Mosquito control treatment scheduled for East Coventry Township
to control nuisance mosquitoes.” released dated 6/13/16. Spraying was scheduled for June 15 from 8:30 pm to 10:30 p.m. Download the release here: spraying-e-coventry-6-15-16.

“West Nile Virus identified in mosquito sample in Chester County
West,” release dated 7/15/16. The mosquito sample in question was collected in Tredyffrin on July 7. Download the release here: west-nile-idd.

“Mosquito control treatment scheduled for Thornbury and Birmingham Townships
to prevent West Nile Virus,” release dated 9/9/16. Spraying was scheduled for Sept. 13 from 7:30 pm to 11:00 p.m. Download the release here: spraying-thornbury-birmingham-9-13-16

Also hear an interview about Zika virus with Chesco Health Director Jeanne Casner and other staff members on The Julia Journal, WCHE, 1520 AM, 9/29/16.

Community activists fight mosquitoes and spraying

by Pete Bannan, Daily Local News, 9/10/16

WEST CHESTER >> Motorists driving through the streets of the borough this summer may have noticed the lawn signs with a baby wearing a gas mask stating ‘Don’t Spray Me.’ Those provocative signs belong to a group of community activists formed to stop Chester County from spraying pesticides in the borough.

Co-founders Margaret Hudgings and Nathaniel Smith recently sat down with a reporter to talk about the group.

“In 2012 the county sprayed in the southwest quadrant of the borough,” said Hudgings. “The morning after it was like silent spring, and we had a lot of people reporting illnesses.”

Three years later, Hudgings and Smith received reports of a plan by the county to spray in the Marshall Square Park area for West Nile mosquitoes which had been discovered in that neighborhood. County Health Department officials planned to use permethrin with permanone, sprayed by truck in the evening after winds had calmed down.

Concerned about the health effects on people and the environment, the two drew up a petition calling for a stop to spraying.

“We assembled a group of five volunteers who walked the southwest quadrant of the borough with a petition asking the county not to spray,” Hedging said. “We got a 98-percent signing rate. People don’t want to be sprayed.”

They presented it to West Chester Mayor Carolyn Comitta and county health officials…

dln-dsm

read more at Daily Local News

The Zika virus and Chester County

by Nathaniel Smith, The Times of Chester County, 9/1/16

Getting rid of standing water is more effective than spraying

News has come around lately that “Pennsylvania Is Now One Of The Top States With Zika Virus ” (Phoenixville Patch, 8/23/16). Currently PA ranks 5th in the number of diagnosed Zika cases. Of course, no one knows how many undiagnosed cases there are anywhere.

Quick quiz: how is Zika spread? If you answered “by mosquitoes,” you’re only half right. It’s our fault too.

It’s important to focus on this note in the article: “All of the cases were travel-related, according to the Centers for Disease Control and Prevention.”

That means no human has acquired Zika from a mosquito in PA. Although the prime mosquito host for Zika, aedes aegypti, does exist in Pennsylvania, it doesn’t do well this far north (yet).

The fact is that Zika is spread not only by mosquitoes but also by people, whether through sexual contact (CDC offers explicit advice on this aspect) or from carrying the virus (usually without symptoms) and being bitten by a mosquito that in turn bites someone else, who thus acquires the disease. The aedes albopictus mosquito, often called “Asian tiger,” has become very numerous in PA but fortunately does not seem to transmit Zika very well (yet).

Spraying pesticides is a limited, short-term fix that leaves many adult mosquitoes alive and does not affect eggs and larvae but harms many forms of life and can lead to acquired immunity. Mosquitoes breed over 500 times faster than people, so they will become immune to whatever we do against them much faster than we can evolve to resist them. Mosquitoes in Puerto Rico and Florida are already becoming resistant to permethrin, the standard anti-mosquito pesticide.

This is all not good news, except that in PA we do have some time to get ready for present and future mosquito-borne diseases….

read more at The Times of Chester County

Mosquito traps made from old tires are 7 times more effective than standard traps

by Melissa Breyer, treehugger, April 8, 2016

A new study found this cheap, easy system significantly reduced virus-carrying Aedes mosquitoes in Guatemala.

Called an ovillanta, a simple mosquito trap fashioned from old tires spells doom for mosquito eggs. So effective is the cheap eco-friendly system that during a 10-month study in Guatemala, the team collected and destroyed over 18,100 Aedes mosquito eggs per month, almost seven times the eggs collected compared to standard traps. Anecdotally, the researchers note that there were no new reports of dengue during the time in the area, normally during that timeframe the community would have reported up to three dozen cases.

The Aedes genus of mosquitoes is primarily responsible for transmitting a host of vexing viruses, including Zika, dengue, chikungunya, and yellow fever. Aedes is notoriously tough to control, according to the World Health Organization. Pesticide-resistance, lack of resources, and a boost in mosquito-friendly environments have hindered traditional methods of controlling the pest’s quick spread.

Created in collaboration by researchers from Canada and Mexico, the ovillanta is made of two 20-inch sections of old car tire secured together in the form of a mouth, with a fluid release valve at the bottom. A milky mosquito-luring non-toxic solution is poured in the bottom – the solution includes a mosquito pheromone that tells female mosquitoes that it’s a safe place to lay eggs. The mosquitoes enter, lay eggs on a paper or wooden strip that is floating in the “pond” … twice a week the little egg raft is removed, the eggs destroyed, and the solution drained and filtered before being reused in the trap again….

ovillanta old tire mosquito trap

read more at treehugger

Aimed at Zika Mosquitoes, Spray Kills Millions of Honeybees

By ALAN BLINDER, New York Times, SEPT. 1, 2016 [n.b. the spraying agency made several “human errors” in this case: spraying a toxic chemical other than as a last resort; not giving adequate public notice, especially to beekeepers; and spraying when bees are active during morning hours and on a hot day. If you ever observe private companies spraying airborne pesticide at times or locations where bees could be active, please document details and let us know.]

The Monday morning scene at Juanita Stanley’s apiary in Summerville, S.C., was ghastly and stunningly quiet: Everywhere one looked were clumps of honeybees, dead after a dousing on Sunday with the potent pesticide with which the local authorities had intended to kill mosquitoes.

“There was no need for a bee suit Monday morning to go down there, because there was no activity. It was silent,” Ms. Stanley said on Thursday. “Honestly, I just fell to the ground. I was crying, and I couldn’t quit crying, and I was throwing up.”

For Ms. Stanley and her business, the death toll easily exceeds two million bees, and Dorchester County officials are still tabulating how many more might have been killed when a day of aerial spraying, scheduled to combat mosquitoes that could be carrying viruses like Zika, went awry. The apparently inadvertent extermination, the county administrator said, happened after a county employee failed to notify Ms. Stanley’s business, which the administrator said should have been alerted about the spraying strategy. Some hobbyists were also caught by surprise.

“We’ve learned that the beekeeping community in Dorchester County, and in that area in particular, is larger than we were aware of,” Jason L. Ward, the county administrator, said in an interview. “Our idea is to balance working with them with the issue of public safety.”

Concerned about the spread of the Zika virus across the South, local officials on Sunday targeted a 15-square mile area of the county, which is near Charleston, with naled. The pesticide, which has been in use in the United States for more than 50 years, is a common tool for mosquito control, but federal officials have said the chemical can be harmful to honeybees while also posing brief risks to aquatic invertebrates and terrestrial wildlife….

read more at New York Times. Also see Melissa Breyer, “Massive bee death after South Carolina sprays for Zika mosquitoes, treehugger, 9/1/16, and “‘Like it’s been nuked’: Millions of bees dead after South Carolina sprays for Zika mosquitoes,” Washington Post, 9/1/16 (see also videos and photos there).

More technical: “NALED Insecticide Fact Sheet” at No Spray Coalition. A dangerous spray, no doubt about it!

Inovio Pharmaceutical’s DNA Vaccine for Zika Virus Induces Robust Immune Responses in Preclinical Study

Inovio Pharmaceutical, 2/17/16

Biotech begins clinical manufacturing; expects to test Zika vaccine in humans in 2016

PLYMOUTH MEETING, Pa., Feb. 17, 2016 (GLOBE NEWSWIRE) — Inovio Pharmaceuticals, Inc. (NASDAQ:INO) announced today that preclinical testing of its synthetic vaccine for the Zika virus induced robust and durable immune responses, demonstrating the potential for a SynCon® vaccine to prevent and treat infections from this harmful pathogen. Health authorities have observed neurological and autoimmune complications potentially associated with Zika virus, including microcephaly in newborns and Guillain-Barre syndrome. Inovio is developing its Zika vaccine with GeneOne Life Sciences (KSE:011000) and academic collaborators.

Read more at Inovio Pharmaceutical. Read about the current clinical trial in Puerto Rico here.

Don’t Spray Me community celebration on Sunday, September 4, at 4-7 p.m. in Everhart Park

Community celebration for Dontsprayme members: Block Captains, displayers of signs, others who support our goals — we’ll ask you to fill out a brief survey and sign in free as members.

What’s happening?

Mayor Carolyn Comitta, who has been indispensable in our successes this year, will speak to us
Friends of Everhart Park
Sierra Club of Chester County
West Chester Food Co-op
West Chester Community Rights Alliance
Info on the Borough’s various green efforts
Games for children; face painting
Bat house construction
Martial arts demo
Meeting lots of local, like-minded people

Union St. side of Everhart Park 

Please bring whatever food and drink you wish to consume (no alcohol), with utensils, plus a blanket or lawn chairs, if desired.

Come celebrate our success in a summer of fewer mosquitoes and no spraying in West Chester!

In case of threatening weather, please check here for any update. Rain date Monday.