Impact of naled (Dibrom 14) on the mosquito vectors of eastern equine encephalitis virus.
SOURCE: Journal of the Am Mosquito Control Assoc, Dec;13(4):315-25, 1997
Howard JJ, Oliver
New York State Department of Health, SUNY-College ESF, Syracuse 13210, USA.
In central New York, aerial mosquito adulticide applications have been used in response to eastern equine encephalitis (EEE) outbreaks and have targeted the swamp habitats of the primary enzootic vector of EEE virus, Culiseta melanura (Coquillett). The organophosphate insecticide Naled (also called Dibrom) (1, 2, dibromo-2, 2-dichloroethyl dimethyl phosphate) has been the insecticide of choice in this region. This study reports on analyses of 11 years (1984-94) of mosquito collection data from Cicero and Toad Harbor swamps in relation to applications of naled. Naled applications were successful in achieving short-term reductions in mosquito abundance. However, despite repetitive applications, populations of the primary vector of EEE virus, Cs. melanura, have increased 15-fold at Cicero Swamp. Preventive applications had no noticeable impact on the enzootic amplification of EEE virus, and isolations of virus following preventive applications have resulted in additional spraying. The possibility that applications of naled contributed to increased populations of Cs. melanura discredits the rationale that preventive applications of naled reduce the risk of EEE.
CHEM-TOX COMMENTS:
The above research provides strong evidence of how mosquito control pesticides (once applied to a "pristine" wildlife habitat) can then result in a dramatic increase in the incidence rate of encephalitis carrying mosquitoes in the area. While this research only shows "what is happening" - the next research would suggest investigations into "why it is happening." Current theories regarding this issue include:
1) Weakening of Wildlife Immune Systems
Due to the recent increase in journal articles finding that low level chemical exposures can decrease the quality of mammalian immune system function, it is quite reasonable to expect wildlife in this immune weakened state to contract encephalitis more frequently. Therefore, one would also expect to see an increase in the numbers of mosquitoes developing encephalitis (since their chance of biting encephalitis infected wildlife has also increased).
2) Damage to the mosquito genetic structures
Studies have shown that mosquitoes with a "leaky" stomach barrier allow transfer of the encephalitis virus from their stomach to their salivary glands (after ingesting a contaminated blood-meal). Mosquitoes which do not exhibit this "leaky" stomach condition do not appear to be able to contract encephalitis either at all - or as readily. Therefore, since chemical pesticides are well-known to induce genetic damage in tests in living cells and in animal test models, the possibility must be considered that genetic mutations could very well be occurring to the genes within the mosquito which control proper stomach integrity and that this resulting loss of integrity could be increasing the encephalitis development rate among mosquitoes.
Evidence Suggests a Possible Link
by Richard Pressinger (M.Ed.)
Chem-tox.com
A new theory is coming to light which should be causing concern regarding the use of chemical pesticides for controlling mosquito populations in Florida and elsewhere. Because of the serious potential for irreparable widespread harm to human health regarding this potential problem, it is an issue that cannot be ignored and must be investigated immediately and thoroughly as it is based on the latest information we have regarding encephalitis carrying mosquitoes and human genetic function.
New Discovery Encourages New Theory
As scientists learn more about encephalitis, along with the effects of chemical pesticides on human health, we are now able to see connections between the two that suggests pesticide use may very well be increasing the encephalitis problem it was intended to reduce. Rates of encephalitis infection among "Sentinel Chickens" in Brevard County Florida have steadily increased from zero in 1990 to three around 1995 and are now up to seven in 1999. Other Florida counties are seeing similar increases as well. Hundreds of millions of dollars are being spent each year on mosquito control in Florida, yet, the encephalitis problem (at least according to our monitoring system), continues to worsen. A 15-fold increase in encephalitis carrying mosquitoes was found in one New York swamp habitat after beginning treatment with the pesticide Dibrom (Naled) over an 11 year period. This was reported in the Journal of Mosquito Control (1997, Vol. 13). This provides strong evidence demonstrating that current chemical treatment methods are actually making the situation worse in the long term. Common sense suggests if this trend continues - the likelihood of being bitten by an encephalitis carrying mosquito will increase dramatically as long as we choose to continue the use of chemical pesticide applications.
