NO SPRAY NEWS MARCH 8, 2003
Part 1: The Year West Nile Virus Arrived (sort of)
Disease Déjà vu
Tiger Mosquitoes and West Nile virus
Did the Drought Really Save Us?
Lesser Known West Nile Virus Facts
Will Outbreaks Be An Annual Event?
Part 2: More Questions About Sprayings Effectiveness Against West Nile
CDC Scientists Conclusions vs. the CDCs Company Line
Should We Spray Water?
How Killing Mosquitoes Can Increase Mosquito-Borne Disease
Part 3: 2002 Local Mosquito Spraying Roundup
City of Columbia: City Cant Find Mosquitoes, Sprays Anyway
West Nile Provides Excuse For More Routine Spraying by DHEC
Most Spraying Done When Traps Show Few Mosquitoes
DHEC Trap Locations Pump Up Mosquito Counts
Are We Spraying For Tiger Mosquitoes? DHEC Wont Say
Why Spraying for Tiger Mosquitoes Is Not Effective
Part 4: EPA Toxicologist Rips EPAs Malathion Risk Assessment
Excerpts from His Open Letter
City of Columbias Donny Phipps reassures residents
The Spray Is Not Going To Hurt Us.
Part 5: References and Explanatory Notes
THE YEAR WEST NILE VIRUS ARRIVED (SORT OF)
Well, it turned out that this was the year, although, at least here in South Carolina, it didnt live up to all the hoopla, with not a single human case confirmed to have been contracted here.
DISEASE DÉJÀ VU: Although West Nile virus is new in North America, its more virulent cousin, St. Louis encephalitis was first identified in the U.S. over 70 years ago.
According to the U.S. Centers for Disease Control (CDC):
Epidemiologically, clinically, and in terms of prevention and control methods, the differences between the 2 viruses generally are subtle and largely academic.1
MORE THAN A COINCIDENCE?
- South Carolina has never had a human case of St. Louis encephalitis.2
- South Carolina has never had a human case (known to have been contracted here) of West Nile virus.
The 3 states with the most cases of WNv in 2002 were Illinois, Michigan, and Ohio, with a total of 1720 cases.3 This region of the country has also been headquarters for St. Louis encephalitis over the years. (Illinois, Ohio, and Indiana rank 2, 3, and 4 in the nation in St. Louis Encephalitis cases, 1964-1998.)4
WEST NILE VIRUS TOTALS FOR SOUTH CAROLINA 2002
Source: DHEC website
- 52 WNv-positive birds
- 25 cases of WNv in horses
- 3 pools of WNv- infected mosquitoes.
- 0 human cases confirmed to have been contracted here.
Lexington Countyand Richland County led the state in West Nile virus-positive birds, with 9 and 8, respectively. Richland County had 2 of the 3 West Nile virus-positive mosquito pools in the state, both in the Harbison area. (Both of the pools were Culex quinquefasciatus.)
FACTS ABOUT OUR MAIN VECTOR OF WEST NILE VIRUS:
Culex quinquefasciatus is a mosquito that likes dirty water. It breeds in storm drain catch basins, foul water pools, and containers too polluted or otherwise unacceptable to tiger mosquitoes. In third world slums, open sewers provide habitat for enormous numbers of these mosquitoes. At my house in Dentsville, I see only about a half dozen per year, mostly in April and October, but for some reason there appear to be more in the Harbison area.4a They look nothing like tiger mosquitoes, being light brown instead of black with white stripes. If you do have some of these mosquitoes, they may very well find their way into your house in fact, their common name is Southern House mosquito.
An Earlier Invader: Like the tiger mosquito, Culex quinquefasciatus (as well as its colder-weather cousin, Culex pipiens) is adapted to human-altered environments, and, like the tiger mosquito, it is an exotic that has been transported around the world by people. In the case of these two Culex species, their world-wide distribution (out of Africa) took place hundreds of years ago on sailing ships.5 Here in Columbia, we are actually close to the dividing line between the 2 species; in fact, Clemson has Culex pipiens instead of Culex quinquefasciatus.6
ONE REASON HORSES GET WEST NILE:
Horse pastures and stables tend to contain:
a) lots of horse manure, and
b) soils which, due to compaction by horses hooves, produce long-lasting puddles after rains.
Put the two together and you get foul-water pools that are
made-to-order for Culex quinquefasciatus.
THE PRESENCE OF TIGER MOSQUITOES
REDUCE THE INCIDENCE OF WEST NILE VIRUS?
Despite repeated predictions that West Nile virus would take advantage of the Souths longer mosquito seasons and abundant mosquitoes, the disease has so far occurred predominantly in the North, where winters are too cold for tiger mosquito eggs to survive.
THE TIGER MOSQUITO ENIGMA: On paper, the tiger mosquito looks like an important vector of West Nile virus, being able to transmit the virus 70% of the time just 4 days after being infected. Compare this to the main vector, Culex spp., which was found to be capable of transmitting West Nile virus only 15-30% of the time, and then only 10 days after being infected.7 It would seem reasonable to conclude that the presence of the tiger mosquito would increase the risk of a West Nile virus outbreak. But think again
NOT BITING ENOUGH BIRDS? It appears that the limiting factor in the ability of the tiger mosquito to serve as a vector of West Nile virus is that it doesnt bite birds that much.8 ( WNv is essentially a bird disease that people and horses accidentally get.) The tiger mosquito is a day biter. But Culex mosquitoes, which are better adapted to feed on birds, are out after dark, when most birds are inactive and are sitting ducks, so to speak.9
MOST WNV WHERE CULEX MOSQUITOES DOMINATE CONTAINER HABITATS: In northern states where there have been many more West Nile virus cases, Culex mosquitoes occupy what would otherwise be the tiger mosquitos urban container habitats. Is this the key factor in the higher number of West Nile virus cases in the North? I am not implying that you cant get West Nile virus from being bitten by a tiger mosquito, only suggesting that the overall effect may be to reduce the number of cases.
DID THE DROUGHT REALLY SAVE US
FROM WEST NILE VIRUS LAST YEAR?
Thats the message repeated ad infinitum by DHEC representatives, from Commissioner Earl Hunter on down.11 On the surface it does sound plausible. After all, more rain means more mosquitoes, which means more mosquito-borne disease, right? But with diseases like West Nile virus and St. Louis Encephalitis, it doesnt work that way.
DHECS CLAIM DOESNT HOLD WATER
Two researchers reported in a 2001 paper entitled West Nile Virus & Drought12 that:
We analyzed weather patterns coincident with a series of U.S. urban outbreaks of St. Louis encephalitis (a disease with a similar lifestyle) and four recent large outbreaks of West Nile virus. Drought emerged as a common feature.
The following reasons that have been suggested for the correlation between drought and these diseases:
Ironically, at the same time that DHEC was claiming in The State newspaper that the drought was the reason why we didnt have West Nile virus here, the (Charleston) Post&Courier was quoting a Johns Hopkins University Public Health professor14 who cited the nationwide drought as the reason there were already so many cases in the U.S. this year.
Of course, all droughts are not created equal. Maybe ours was so severe as to inhibit any amplification of the West Nile virus. But this doesnt explain the absence of St. Louis Encephalitis cases in South Carolina over the past 70+ years.
HURRICANE LILI DOUSES WEST NILE VIRUS OUTBREAK
If droughts are a common feature of WNv outbreaks, then flooding rains result in ?
From a Louisiana Dept. of Health press release (Oct. 24, 2002):
For the fourth week in a row, health officials are reporting very few new human cases of West Nile virus. .. The trend of fewer cases of West Nile comes in spite of reports throughout south Louisiana that mosquito populations are at an all-time high.
Reuters News Service (10/4/02) quoted Louisianas state epidemiologist, Raoult Ratard, as saying that Hurricane Lili and Tropical Storm Isidore may have dealt a fatal blow to [Louisianas] West Nile virus outbreak.
WILL WEST NILE VIRUS OUTBREAKS BE AN ANNUAL EVENT??
WEST NILE HERE TO STAY, HEALTH OFFICIALS WARN headline in the (Charleston) Post&Courier, August 6, 2002
This is something we are going to have to live with. CDC Director Julie Gerberding (from the AP article under the above headline)
Oh, Really? Consider the history of St. Louis Encephalitis in this country, which the CDC itself admits is almost identical epidemiologically to West Nile virus.20 In 1975 St. Louis encephalitis was the leading cause of encephalitis in the USA, with 1810 cases.21 Now, although St. Louis encephalitis is still around, most people have never heard of it, even though it is more virulent than West Nile virus. In Europe, West Nile also follows a pattern of occasional sporadic outbreaks (called recrudescence). Why wont it be the same here, once it gets settled?
One caveat: Admittedly, exotic life forms transferred to novel environments are inherently unpredictable but this only implies the possibility that West Nile virus wont behave as it has in Europe, not the likelihood.
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MORE QUESTIONS ABOUT SPRAYINGS EFFECTIVENESS AGAINST WEST NILE VIRUS
CDC ENTOMOLOGIST EXPRESSES DOUBTS ABOUT SPRAYINGS VALUE
From Science Magazine, September 20, 2002, p.1989
Surprisingly little is known about how useful spraying is, [U.S. Center for Disease Control medical entomologist Paul] Reiter says, and there are reasons to doubt its efficacy. Spray trucks produce a relatively narrow swath of insecticide, whose dispersion is further blocked by buildings and vegetation. Furthermore, insecticides kill only flying mosquitoes; those that are resting which might be the majority survive.
IN THE TREE TOPS: This same article in Science described an experiment performed by Reiter that determined that Culex pipiens (the northern relative of our own WNv vector, Culex quinquefasciatus) feeds on birds mostly in the tree canopy, 50 feet or more above ground. This is out of range of most of the insecticide from spray trucks.
A TOUGH MOSQUITO TO KILL:
From Jefferson Parish (Louisiana) Mosquito Control website
The adult Southern House mosquito [i.e., Culex quinquefasciatus, our main WNv vector] is well recognized as the most difficult mosquito to abate by reason of its secretive activity and its propensity to become pesticide tolerant.
SHOULD WE SPRAY WATER?
According to Charlie Morris, University of Florida Extension Medical Entomologist
One component of mosquito control that should not be overlooked is the placebo effect. It is common knowledge that if people see a spray truck , they will perceive a reduction in the mosquito problem, whether or not there is one. This is referred to by mosquito control as people control.21a
CDC OFFICIAL CALLS SPRAYING FOR DISEASE A FAILURE IN LOUISIANA
From the Shreveport Times, Sept. 11, 2001
In a closed door meeting, local elected officials spoke about replacing Centers for Disease Control entomologist Harry Savage . Savage cited both personal and professional obligations as his reasons for leaving. He issued recommendations for a program to target immature, or larval, mosquitoes. He had earlier announced that weeks of intense spraying by trucks and planes had no effect due to storm sewers in which mosquitoes can breed.
By the way, the mosquitoes Dr. Savage (above) is referring to as breeding in storm drains are Culex quinquefasciatus, which is also the main WNv vector here in Columbia. In this case, the disease outbreak was West Nile virus cousin, St. Louis encephalitis.
Note The Discrepancy: In discussing mosquito spraying, the CDCs official West Nile Virus Guidelines read in places like a pesticide company ad. For example, the CDC makes the claim that mosquito spraying is an extremely important part of any integrated mosquito management program.22 However, as you can see by the above citations, the CDCs company line is one thing, and what individual CDC scientists say is something else.
HOW KILLING MOSQUITOES CAN INCREASE MOSQUITO-BORNE DISEASE
Even if spraying does manage to kill some Culex mosquitoes, it could at the same time be increasing the number of West Nile virus cases. This is because mosquito spraying doesnt just kill mosquitoes. In fact, the ability of mosquito spraying to cause pest outbreaks (of scale insects, for example) by preferentially killing insect predators is well- documented.24 If mosquito spraying results in the remaining mosquitoes living longer due to the loss of predators, then this effect can quickly overwhelm any initial benefit of killing some vector mosquitoes.
A SURPRISING RESULT: Since it takes 10 days after biting a viremic bird before a Culex mosquito can pass West Nile virus on,23 the key factor in transmission of this disease is not how many vector mosquitoes there are, but how many old vector mosquitoes there are. Thus even a small increase in mosquito longevity can radically increase transmission of West Nile virus. Daily survival probabilities used by CDC scientists in modeling Culex populations range from 0.6 to 0.8.25 Even with no change in the overall Culex mosquito population, increasing the daily survival probability from 0.6 to 0.8 will eventually produce a 3900% increase in vectorial capacity!26
OTHER WAYS THAT SPRAYING MIGHT INCREASE WNV
Many of the pesticides used in mosquito spraying have been shown to affect the immune system.27 Could exposure to these pesticides in the course of mosquito spraying increase susceptibility to West Nile virus:
- In people?
- In birds? (which serve as WNv reservoirs)
- In mosquitoes receiving a sublethal dose of insecticide?
(Consider that West Nile virus is also a disease of mosquitoes.)
I am aware of no research specifically linking pesticide exposure to West Nile virus susceptibility, but it sounds plausible.
JUST A COINCIDENCE? Louisiana probably has the most unrestricted mosquito spraying of anywhere in the U.S.. Yet in 2002 this state also happened to have by far the most human cases of any southern state (323 cases).
If spraying works, then why didnt it work here?
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CITY OF COLUMBIA 2002
CITY CANT FIND MOSQUITOES, SPRAYS ANYWAY
While the local media last August and September showed the city of Columbia putting out mosquito traps and spraying for mosquitoes in response to finding WNv-positve birds, they neglected to mention that the citys traps had produced only very low counts of mosquitoes.28 (Remember that these traps do not catch tiger mosquitoes, the kind everyone has, and which the city of Columbia does not even claim to be spraying for.) The city, in response to my Oct. 2, 2002 FOIA request, stated that:
As recommended and used by the CDC, a one mile radius of the areas where birds tested positive for West Nile virus was sprayed.
But this is not the recommendation I found on the CDC Guidelines, which says:
Consider focal or targeted adult mosquito control if surveillance indicates likely potential for human risk to increase.29
Admittedly, this is somewhat vague, but it is hard to see how surveillance indicates likely potential for human risk to increase when the citys surveillance cant find many mosquitoes period, let alone infected mosquitoes.
Donny Phipps, who oversees the citys mosquito spraying, hinted at the low mosquito counts in a WOLO-TV interview on (about) August 30:
Phipps: We did want to spray, basically because we do have a contagious mosquito in the area, so whether there is 1 or 10,000, we want to kill them.
The city of Columbia sprayed a total of 4 times in 2002. In each case, the insecticide used was malathion.
Richland County 2002:
WEST NILE PROVIDES COVER FOR MORE ROUTINE SPRAYING
(note: Richland County contracts DHEC to manage its mosquito spraying and mosquito control.)
Despite the drought and low mosquito counts, DHEC continued routine spraying in Richland County until the beginning of July. DHECs records30 show that the resumed spraying that took place after a WNv-positive bird was found in Harbison on August 13 appeared to be mostly routine as well, showing little relationship to trap counts of mosquitoes associated with West Nile virus.
IS THIS SPRAYING FOR WEST NILE VIRUS? After the arrival of West Nile virus on August 13, DHEC spent the same amount of time spraying a single zone (an area of Forest Acres west of Trenholm Road) as it spent spraying 3 zones running from the Greystone Boulevard area north through Harbison. This was despite the fact that:
MOST SPRAYING DONE WHEN TRAPS SHOW FEW MOSQUITOES
As in years past, the great majority of DHECs Richland County spraying was done when its own mosquito traps showed that mosquito levels were below (in fact, way below) the standard nuisance threshold of 25 mosquitoes per night, or in the absence of any trap data. Only 10% of spraying was done when DHECs traps showed that mosquito levels were above the nuisance threshold, and another 4% when they were close to the nuisance threshold of 25 mosquitoes caught in a night. In fact, more spraying was done where DHEC traps found absolutely no mosquitoes than when mosquito levels over the nuisance threshold were found (21.4 hours vs. 20.7 hours).33
A REALITY CHECK: Even as this spraying was going on, DHECs Richland
County Environmental Health Director Jim Raymond was claiming that, we only
spray as a last resort in a June 26 meeting with Richland County officials.30a
COMPARE THIS TO LOUISIANA: A single trap in Louisiana caught over 50,000 mosquitoes in one night this past autumn after flooding caused by Hurricane Lili.31
ILLEGAL IN SOME STATES: In Florida, it is actually illegal to do mosquito spraying when mosquito trap counts are less than 25 mosquitoes per night.32 (Florida regulations do permit alternate methods of documenting elevated mosquito levels.)
DHEC TRAP LOCATIONS PUMP UP MOSQUITO COUNTS:
But even DHECs paltry mosquito trap statistics for Richland County overstate actual mosquito levels in residential areas where spraying is done
I know of at least 2 cases (and I believe there are more) in which DHEC places its traps in localized mosquito hotspots adjacent to flood plains.34 These hotspots (which produce a large percentage of the mosquitoes trapped in Richland County) are completely unrepresentative of the large residential areas that are supposedly being monitored by these traps.
DHEC has declared the locations of these traps exempt from disclosure under the South Carolina Freedom of Information Act. (DHECs claim of exemption is in clear violation of the Act.35) Nevertheless, in these two cases I have a general idea of where the traps are located. Records of an alternate trap in one zone showed that DHECs regular trap (located adjacent to Gills Creek floodplain) overstates typical residential mosquito numbers by 900%. (Thanks to Richland County Councilwoman Joan Brady for getting this alternate trap set up.) This finding concurs with data from my own landing rate counts in this zone, and with results reported by USC grad student Stephanie Cook in her 1998 masters thesis.36
MY PERSONAL EXPERIENCE: In my own case, DHEC sprayed my neighborhood at 3:30am on the night of June 10-11. DHECs records show that, just before spraying occurred, its trap found 11 mosquitoes, but that night I could get only 1 to bite me in 45 minutes. When DHEC sprayed again on September 10-11, it was basically the same story their trap found 22 mosquitoes, but I found only 2 Aedes vexans mosquitoes in 30 minutes. Where are they finding all these mosquitoes? I dont know where DHEC places its trap in my spray zone, and DHEC isnt telling.
The purpose of DHECs mosquito trapping appears to be to find as many mosquitoes as possible in order to provide an excuse for spraying as much as possible.
THE FUTILITY OF RURAL SPRAYING: The mosquito spraying done without trap data in 2002 was almost all done in rural parts of Richland County. Spraying rural areas by truck is intrinsically ineffective, due to the fact that spray from a truck impacts only areas immediately adjacent to roadways. One Florida mosquito control department compared spraying rural areas by truck to dipping a cup in a swimming pool water from the rest of the pool simply rushes in to take its place.
WHAT ARE WE SPRAYING FOR? DHEC WONT SAY
At a June 26, 2002 meeting I had with Richland County and DHEC officials, DHECs Richland County Mosquito Control Director Tammie Brewer refused to state whether Richland County was spraying for tiger mosquitoes, repeatedly responding that I wont say that we are, and I wont say that we arent. Keep in mind that the tiger mosquito is responsible for something like 99% of the mosquito bites here in the Columbia metro area.37 Whether she wants to admit it or not, DHEC is spraying for tiger mosquitoes, since its spraying is partly (if not mostly) based on landing rate counts and mosquito complaints, both of which include tiger mosquitoes.
SAY IT AGAIN SPRAYING IS NOT EFFECTIVE AGAINST THE TIGER MOSQUITO
The tiger mosquito is a daytime flyer and cannot be effectively controlled using routine ULV strategies. North Carolina Department of Environment and Natural Resources
These applications would have almost no effect on the day biting mosquitoes [i.e., tiger mosquitoes] (the ones that bite us the most).- Georgia Extension Service
Our normal spraying for adult mosquitoes is ineffective against this mosquito [the tiger mosquito]. Indian River County [Florida] Mosquito Control
The asian tiger mosquito flies during the day and isnt controlled by evening spraying Bob Bellinger, Clemson University Entomology Department Pesticide Coordinator
WHY NOT SPRAY IN THE DAYTIME FOR THE TIGER MOSQUITO?
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EPA SENIOR TOXICOLOGIST RIPS EPA RISK ASSESSMENT FOR MALATHION
EPA Toxicologist Brian Dementi speaks out:
(italics from original)
The following constitutes a personal statement of dissent with respect to certain conclusions of this risk assessment for malathion. .
I do not find acceptable our cancer committees interpretations regarding the following:
Liver tumor responses in the mouse and rat
Rare nasal cavity tumor findings in the rat, where substantial evidence of nasal tissue vulnerability to malathion is evident, both in the rat and mouse.
Rare squamous cell tumor findings in the palate of the rat, in concert with the absence of a full histopathology assessment of the oral cavity.
Thyroid C-cell tumor response in the rat.
Thyroid follicular cell tumor response in the rat.
Testicular interstitial cell tumor response in the rat.
I have considerable disagreement with our cancer committees understanding and use of principles of interpretation of neoplastic findings in cancer bioassays as set forth in various authoritative sources. For example:
Employing less remarkable tumor findings at high dose levels, considered excessive, to discount significantly positive tumor findings of the same kind in an acceptable lower dose range, which I might add, are of inherently greater concern because of the enhanced concern over findings in the lower dose range.
Inadequate review of the collective evidence of carcinogenicity at very low doses.
Issues: Deletion of the Food Quality Protection Acts imposed 10X safety factor for
the protection of infants and children is indefensible, as our committee has not been
successful in establishing the malathion database to be: a) complete, b) reliable, and c)
absent evidence of increased susceptibility of the young versus adult animal, as required
under the Food Quality Protection Act. For example, I maintain that the evidence of
increased pup sensitivity in the malathion reproduction study, a focal study for assessing
susceptibility of the young, cannot be discounted on the basis of the committees
argument of increased consumption of malathion
via dams milk, absent identification of malathion in the milk, let alone any
quantitative assessment of the same. I further maintain that other studies presented to
the same committee, particularly a published work showing a nine-fold greater sensitivity
of neonatal versus weanling rats resulting from acute administration of malathion, serve
to illustrate enhanced susceptibility of the young to this organophosphate.
Brian Dementi, Ph.D., D.A.B.T. Senior Toxicologist, Toxicology Branch/HED
For the full text of the letter, see http://www.epa.gov/pesticides/op/malathion/dementi_1100.pdf
-City of Columbias Donny Phipps, providing his own toxicological assessment of malathion on the WIS-TV 6 oclock news (on about Aug. 30, 2002)
In the same broadcast, WIS-TVs Crystal Davis made the following report:
Phipps says the spray isnt anything to be concerned about, for most humans. In fact, he says that most people could run along behind the fogger truck, and not be affected.
(Mr. Phipps did not respond to my repeated attempts to ascertain the accuracy of this quote.)
Later that night on WOLO-TV, Phipps tempered slightly the remarks attributed to him on WIS-TV.
Phipps:I wouldnt want to run behind the truck or bathe in it, its common sense, but no, were not spraying anything that is dangerous to the public by any means.
Phipps did note in the WIS-TV interview that some people can have allergic reactions to malathion, and that these people are notified before spraying.
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REFERENCES AND EXPLANATORY NOTES
1) CDC Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention and Control. Workshop held in Charlotte, NC, April 2001. (quoted from the Jefferson Parish, Louisiana mosquito control website: www.jefparish.net)
2) NY encephalitis scare shouldnt concern S.C., The State, 10/2/99. This article cited CDC statistics.
3) CDCs Current Case Count as of 12/19/02.
4) CDC Encephalitis Map: Human St. Louis Encephalitis Cases by State: 1964-1998.
4a) Phone conversation with DHEC medical entomologist Chris Evans (12/2/02). DHEC Light Trap Collections by Area (1998-2000, 2002), while quite variable, also show a general pattern of higher Culex quinquefasciatus levels in this area.
5) Mosquito, by Andrew Spielman, p.44 and 79. ( I hesitate to use this book as a reference, since Spielman himself does not provide references for any of his books assertions. I am aware of some errors in this book, and I do not recommend it, but this particular assertion sounds plausible. If anyone has information to the contrary, please contact me.)
6) Survey of Container-Inhabiting Mosquitoes in Clemson, South Carolina, JAMCA, 1995, p. 396-400. However, according to Rutgers University (www. Rci.Rutgers.edu), there is not a true line of demarcation, but a zone where both species, as well as hybrids, are encountered.
7) Turell, Michael,
Vector Competency of North American Mosquitoes to WNV,J. Med.
Entomol. 38(2):130-134 (2001). Turell, Michael, Vector Competency of Mosquitoes
8) In Arboviruses, (ed. By Thomas Monath) p.160-161, Edman and Spielman describe diurnal species such as the tiger mosquito as adapted for feeding on forest mammals. Culex spp. mosquitoes which feed on birds, by contrast, are nocturnal crepuscular.
The research that I have looked at [J. of Med. Entomol. 30(1):27, JAMCA 10(3):447] indicates that tiger mosquitoes will feed on birds as a last resort, particularly in such settings as tire dumps in rural areas. The J. of Med. Entomol. paper notes that:
Even though Aedes albopictus (the tiger mosquito) was abundant in Pinebluff AR during an outbreak of SLE in 1991, virus was not recovered from this species despite high infection rates in Culex pipiens complex mosquitoes.
In the CDCs 2002 species data for WNV+ mosquito pools, something like 1-2% of those pools are tiger mosquitoes in states with significant tiger mosquitoes. (I didnt do the arithmetic.) This data is hard to interpret without knowing how many pools of each species were tested. However, it certainly doesnt appear to contradict the hypothesis that the net effect of the tiger mosquitos presence would be to reduce the prevalence of WNV outbreaks.
9) Edman & Spielman, Arboviruses (ed. By Thomas Monath), p.161.
11) Here are three articles in The State newspaper in which DHEC officials list the drought as a reason for the lack of WNv here:
a) West Nile Virus Tracked; Residents Can Help, by DHEC Commissioner Earl Hunter (8/24/02).
b) City To Test Mosquitoes for Virus, (8/8/02)
c) Scientists Itching To Catch a Bug, (8/9/02)
12) Epstein, Paul et al. 2001. West Nile Virus and Drought, Global Change & Human Health, 2(2):105-107.
14) Jonathan Patz, professor at Johns Hopkins Univ. School of Public Health.
15) USGS Researchers: West Nile Moves Bird to Bird in Lab, USGS Oct. 25, 2000 news release.
16) Komar, Nicholas et al. 2001. Serologic evidence for West Nile Virus Infection in Birds in the New York City vicinity During an Outbreak in 1999. Emerging Infectious Diseases 7(4): 621-625.
17) Nicholas Komar, vertebrate ecologist at the Arbovirus Disease branch of the CDC, found that the house sparrow (aka English sparrow) developed the highest virus levels and maintained an infectious viremia the longest, 5 days in one case. (from Subject: West Nile Virus & Birds, posted by Lois Levitan, Cornell ERAP.)
18) Walter Tabachnik, U. of Florida Director of FMEL, discusses how the techniques used to detect WNV are extremely sensitive, and count many mosquitoes that are not infective. (See http://fmel.ifas.ufl.edu and search fm buzz.)
19) Arboviruses, (ed. by Thomas Monath), p.89-117, discusses at length the process whereby a mosquito becomes infective.
19a) Science, Sept. 20, 2002, p.1989.
20) as already quoted on p. 1 of this No Spray News issue. See ref#1.
21) Thomas Monath, St. Louis Encephalitis, p.240. This is just a tally of those people who got encephalitis. The total number of cases in 1975 was something like 3,000.
21a) Charlie Morris, Mosquito Control Alternatives , p.56, Mosquito Control Pesticides: Ecological Impacts : Proceedings of a Conference Held Jan. 18, 1991 at Univ. of Florida, Gainesville, (edited by Thomas Emmel).
22) CDC Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention, and Control,. April 2002, p.30.
23) see ref#7.
24) James Stevenson, Public Land Issues, Mosquito Control Pesticides: Ecological Impacts : Proceedings of a Conference Held Jan. 18, 1991 at Univ. of Florida, Gainesville, (edited by Thomas Emmel ), p.46,. In North Carolina, The Southport News (8/1/01) discussed a county agents claim that mosquito spraying was responsible for a hermes scale outbreak that harmed historic oaks.
25) C.G. Moore, et al. Apparent Influence of the Stage of Blood Meal , JAMCA 6(1):279.
26) This percentage figure was derived using the equation for vectorial capacity, C
= ma2 pn
where m = # of vectors / host
(-loge p) a = blood meals by a vector / host / day
p= daily survival probability of a vector
n = days between infection of vector and the time it becomes infective
m is constant
since we are assuming no change in the total vector and host populations.
a is constant since the type of vector, total vector, and total host populations are constant.
p varies between 0.6 and 0.8, per CDC modeling
n = 10 for Culex spp.
This equation appears in Arboviruses (ed. Thomas Monath), p.249.
27) See No Spray News, March 11, 2002, p.2 and April 15, 2002, p.1.
28) According to the City of Columbias Oct. 31,2002 memorandum responding to my FOIA request for trap records. (Apparently there werent even enough mosquitoes to warrant writing down.)
29) CDC: Epidemic/Enzootic West Nile Virus in the United States Revised Guidelines for Surveillance, Prevention, and Control (April 2002), p.38
30) DHEC: Richland County 2002 Adult Density Index Records and Richland County 2002 Light Trap Collections by Area.
30a) From my notes on this meeting, which I attended.
31) The Advocate (Lafayette, Louisiana) on Oct. 19, 2002 quoted a mosquito control contractor who claimed to have caught 60,000 mosquitoes overnight in a surveillance trap in Duson, LA. I had another source which claimed 50,000 mosquitoes around this date in a government mosquito control trap, but I cant find it.
32) Fla. Admin. Code Rule 10D-54.036(1)-(4) Feb., 1987)
See www.law.ufl.edu/cgr/publications/legal_policy.pdf, page 60.
33) These statistics use mosquito counts from trap 12a rather than from trap 12, since the location of the former is more representative of the zone. See DHECS SECRET farther down the page for a further explanation.
34) I know the location of one mosquito trap because DHECs Richland County Vector Control director Tammie Brewer admitted to me during an April 4, 2002 phone conversation that the zone 12 trap was in the vicinity of a mosquito hotspot along Gills Creek immediately downstream from Trenholm Plaza.
I know the location of another trap in zone 3 because in 1997 Ms. Brewer actually took a State newspaper reporter (Henry Eichel) there. His article in The State, Research helps counties aim efforts to control mosquitoes (7/15/97), described the traps location as behind a home on the edge of the woods along the Broad River. The adjacent flood plain was identified in the article as a major mosquito breeding site.
However, when I submitted a Freedom of Information Act request to obtain the location of this very trap, DHEC claimed that it was a secret exempt from disclosure.
Note: While these are only 2 of DHECs 21 regular mosquito traps in Richland County, they typically catch a large percentage of the total number of mosquitoes trapped per year.
35) DHECs claim of exemption is in clear violation of SC Code 30-4-30(c) on two counts:
1) DHEC failed to make a determination within 15 business days. Therefore, according to this subsection, the request must be considered approved.
2) When DHEC finally did make a determination, it didnt provide a reason, again as required by this subsection.
Absent any attempt at legal justification by DHEC, I can only speculate that it is difficult to imagine legal grounds for exempting this information from disclosure.
36) Ms. Cooks 1998 USC masters thesis was supposed to be about examining mosquitoes in Richland County for resistance to malathion. The only problem was that Ms. Cook couldnt find enough mosquitoes, even in zones 3 and 12 where DHEC traps typically find the most mosquitoes. DHECs Tammie Brewer claimed (in an April 4, 2002 phone conversation) that Ms. Cooks problem was that she didnt put her traps in the locations where she was directed to presumably in the mosquito hotspots along floodplains where DHEC puts its traps.
37) The Houston Chronicle ( 8/13/02) quotes Ray Parsons (head of Harris County [i.e., Houston metro area] Mosquito Control Division, as saying that people are 100 to 1,000 times as likely to be bitten by an Asian tiger as a Culex mosquito. Since tiger mosquitoes are obligate container mosquitoes, and since Houston is flatter than Columbia, the proportion of bites from tiger mosquitoes should, if anything, be greater here.
38) According to Edman and Spielman in Arboviruses (editor: Thomas Monath), p. 162, diurnal mosquitoes such as the tiger mosquito employ the passive strategy of waiting in particular locations until hosts enter the field of attack.
39) Soon after the tiger mosquito was discovered in the U.S., C.G. Moore et al (JAMCA 4:356-361) reported that this mosquito had already been determined to have increased tolerance for a number of insecticides used in mosquito control, and that rapid selection under operating conditions should be considered.
40) Consider the fact that the tiger mosquito, which rarely flies more than 100 yards from where it emerges, spread like wildfire all over the southeast at the end of the 1980s.
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