The "other" side

[Neil Jones]

In article <3987D5F0.622 at mindspring.com>
           cherubini at mindspring.com "Paul Cherubini" writes:

> Similarly, the NABA website
> http://www.naba.org/wnvirus.html is now making sensational,
> worrisome, scientifically groundless claim that the mosquito
> spraying over New York City represents: 
> 
> -"rather significant risks
> not only to humans but to non-target species" and could be
> 
> -"devastating to butterflies and other non-target species,
>  and frightening and potentially harmful to many humans"

I contend that the above is false logic and that small snippets
of an article have been knowingly taken and used to create a misleading
impression.  Does anyone have evidence to the contrary?

Anyway here is the article concerned. Judge for yourselves whether the
learned author is a "scarmongering extremist" or is he applying his considerable
scientific knowledge to find a better solution that both satisfies 
human needs and preservation of the environment. 



The following article recently appeared in the Summer 2000 issue of 
American Butterflies 

Public Panic over West Nile Virus
         by Michael Gochfeld, Professor of Environmental and Community
Medicine at the Robert  Wood Johnson Medical School and School of Public
 Health 

NABA members, even those living far from New York, could hardly have missed
the news coverage of the great encephalitis outbreak (or "scare"). The 
discovery in September, 1999 that a new viral encephalitis had appeared
 in the New York Metropolitan area,fostered a media campaign as well as
 some ill-advised control efforts. The virus, genetically very similar 
to the West Nile Virus which is widespread in the Old World, caused more
 than 50 documented cases of disease and about 7 deaths of humans (all of 
people over the age of 60), as well as widespread mortality in crows and 
sporadic mortality  in other birds. West Nile Virus belongs to a large
 group of arthropod-borne viruses (nicknamed ARBO viruses) which includes
 many viruses that cause more familiar forms of encephalitis as well as 
dengue fever and yellow fever. 

As do other virus, ARBO viruses require a host, in which to live. The 
primary hosts for the virus are referred to as reservoirs. Viruses are
 sometimes spread from host to host by other animals, which are then 
referred to as vectors. For West Nile Virus, mosquitoes are the vectors 
and birds are the primary hosts, while humans are an alternate host. In
areas such as Africa, where the virus has occurred for years, most bird
species have developed resistance to the virus through the selective 
elimination  of susceptible individuals and the survival of those who 
could resist the infection. This evolutionary process is similar to the
 process by which mosquito populations build up resistance to pesticides,
 or by which bacteria develop resistance to antibiotics. 

Having studies ARBO viruses briefly in Trinidad many years ago, I have 
a healthy respect for their potential impact. Nonetheless, it is 
relatively difficult to contract an ARBO virus disease. These diseases 
are not spread directly from person to person. Rather, a person has to 
be bitten by an arthropod (usually a mosquito) that has  recently bitten
an infected animal in whose blood the virus was already circulating. 

Not only are humans not the primary host for this virus, but human are
 probably not even a very good host. Based upon experience with other 
West Nile  Virus epidemics, we know that typically less than one 
tenth of one percent of people bitten by infected mosquitoes develop 
any clinical signs of disease, and of those who do develop disease 
symptoms most do not develop the serious encephalitis manifestations. 
However, up to  10% of those who actually develop encephalitis may 
die of the disease. 

It is clear that there is something particularly terrifying about 
encephalitis that conjures up more frightful images than other more 
common infectious diseases, such as influenza, which each year kills 
more people than does encephalitis. Thus it is easy to understand why 
the arrival of this West Nile-like virus caused such consternation 
and alarm in the media and the public. However, in a city such as 
New York, where more  people die each day of respiratory diseases 
such as asthma and tuberculosis than died in the entire two month 
encephalitis "epidemic," it is surprising that there was such a 
dramatic response among politicians and public health workers who 
expressed an urgency to eradicate mosquitoes. Particularly fearsome
 was the prospect that infected birds would soon be migrating and 
spreading the virus. 

Often, when people think of mosquito control, their first thought 
is pesticide spraying -- what I call "quick Henry -- the Flit" 
mentality (after a popular ad of 50 years ago). This is obviously
what politicians thought of first when West Nile Virus was discovered
in New York. Indeed, pesticide spraying can reduce local outbreaks of
 mosquitoes temporarily, but populations recover quickly and over the 
long term pesticide-resistance emerges. However, serious mosquito-born
e diseases, such as malaria, encephalitis and dengue, continue to
 occur  in many parts of the world, requiring public health officials
 to develop effective means of reducing risks to humans. 

The well-established public health techniques for preventing exposure
 to mosquito-borne diseases include eliminating mosquito breeding 
places or treating them to eliminate the larval mosquitoes, the use
 of screens or netting in homes, the use of mosquito repellants, 
reducing exposed areas of the body and reducing activities that 
expose people to mosquitoes. The use of pesticides to eliminate 
adult mosquitoes is a last resort and should be used only as an 
interim measure when and where there are large infestations of 
mosquitoes in close proximity to human populations. 

Despite these recommendations from the Centers for Disease Control 
and the World Health Organization, widespread spraying (termed 
"broadcast" spraying) was conducted in the New York metropolitan 
area -- even at a time when mosquito populations were declining 
naturally due to cool weather. Pesticide advocates asserted, 
incorrectly, that the pesticides used were innocuous to humans 
and pets and ignored outcries about the harm to non-target species. 
Advocates even pointed to the Monarch migration - the largest in 
years - as evidence that  the spray was harmless to butterflies. 
Although reports of dead birds were widely publicized, no attempt 
was made to document dead butterflies or other non-target insects. 

Television coverage emphasized the spraying and reported where 
spraying was being conducted, but rarely described all the 
above-mentioned steps that homeowners could take to reduce 
their contact with mosquitoes. There were impressive exceptions.
 Union County, New Jersey took out a full-page advertisement in 
the Newark Star Ledger explaining why it was not spraying and 
clarifying the recommendations that empowered readers to act 
in a way that reduced their risk of mosquito bites. Experts in
 environmental medicine at our Environmental and Occupational
 Health Sciences Institute concluded that the media coverage 
of deaths and spraying actually distracted the public from 
these effective measures and created the mistaken impression
 that broadcast spraying was the first choice, the preferred 
effective solution to West Nile Virus disease, and the only 
thing that needed to be done. 

In some counties, the finding of a single dead crow became a 
sufficient stimulus for county-wide aerial spraying, ignoring
 several important features of viral disease ecology, 
avian ecology and pesticide science, and particularly ignoring
the rather significant risks of broadcast pesticide spraying 
not only to humans but to non-target species that are of 
economic, aesthetic and ecological importance. Moreover, 
the investment in spraying diverted scarce funds from other 
public health problems. 

Although malathion (an organophosphate) and the synthetic 
pyrethroids sumithrin (Anvil) and resmithrin (Scourge) have 
relatively low toxicity to humans and other mammals and 
birds, they are not innocuous or harmless. People can become 
sick from exposure to these  pesticides as well as from the 
so-called "inert ingredients" in which they are applied. 
This is particularly true when spraying is repeated. 
Organophosphates such as malathion and pyrethroids reduce 
the activity of the enzyme acetylcholinesterase which is 
essential for normal nervous system function. This is the
mode of action by which these pesticides kill insects and 
harm humans. For example, malathion is in the same class of 
chemicals as the nerve gases such as sarin, and workers who
 produce malathion or blend it into final products as well 
as those who apply it, if not well-protected, can suffer 
agitation, sleepy difficulty and weakness, as well as anxiety,
 forgetfulness and depression. 

Pesticides, even those with relatively low acute toxicity to 
adults may be more problematic in young children, with 
immature nervous systems, and in the elderly. It is also
 a problem for those who have, or believe that they have, 
unusual sensitivities to pesticides or other chemicals. 
TV broadcasts cautioned listeners to remain indoors during 
spraying, but the time of spraying at any one location could
not be predicted and many people could not remain indoors all
 day on the announced day of spraying. Moreover, it is easier
to make a house mosquito-proof than spray proof. Indeed, it is
 well-established that outdoor air pollutants tend to accumulate
 at higher levels indoors than out. 

The reason that my colleagues and I argued against broadcast
 spraying are 1) in broadcast application most of the spray falls
 on areas where the likelihood  of mosquito-human contact 
is low. Thus areas with few mosquitoes but many other non-target 
species are sprayed, as are densely populated residential areas
 where mosquito populations are low to begin with. 2) It is not made 
clear to the public that these broad-spectrum insecticides kill many 
other insects besides mosquitoes. These include economically valuable
 insects such as honeybees, praying mantids and ladybird beetles as
 well as conspicuous and attractive species such as butterflies. 
Such insecticides also destroy innumerable less conspicuous insects
 that are important components of biodiversity and are the food for
 birds and small mammals. This, after all, was the message of Rachel
 Carson's "Silent Spring" published in 1962, that even 
her detractors recognize as one of the most influential books of the
 20th century. 

In weighing the risks and benefits of mosquito control, we should also 
consider the disease itself and the risk to the human population. The
media always paired the words "lethal" or "deadly" with "West Nile" or
 "encephalitis," reinforcing in the public’s mind the danger from the 
disease. But it would be equally appropriate to characterize West Nile 
Virus infection as "inapparent," "usually asymptomatic," or "occasionally
 serious." Seven deaths in a population of over 10 million people 
over a one month period is certainly tragic, but pales besides the 
number of deaths from many other diseases that are addressed less
 aggressively. 

The only human epidemic of West Nile Virus infection that has been
 well-studied occurred in Romania in the late summer of 1996. 
The U.S. Centers for Disease Control and Prevention, certainly 
the premier infectious disease control agency in the world, 
assisted in the evaluation and control of that epidemic and 
recently published a report in The Lancet, the leading British 
medical journal. 

In that epidemic an estimated 94,000 people were infected by the virus, 
of whom about 400 developed clinically apparent encephalitis confirmed
by virological studies. Fifteen of those people, almost all over the
 age of 65, died. Thus, even if one is bitten by an infected mosquito,
the risk of suffering disease is very low and the risk of dying much 
lower. Moreover, in Africa where West Nile Virus has been recognized 
for more than sixty years and where it is widespread, there have been 
very few human epidemics. In fact, West Nile Virus infection is
 characterized by its sporadic outbreak in humans, even in areas 
where it is endemic in birds. This is likwise true of related
 infections, such as St. Louis encephalitis and Easter equine 
encephalitis, where 30 or more years may pass between human 
outbreaks. A knowledge of these numbers is crucial in assessing the 
risk-risk tradeoffs essential to public health decisions in this area. 

Finally, emphasis has focused on dead birds, particularly dead crows.
 Crows are among the most susceptible species to West Nile Virus in the
 Old World and are obviously going to be a major reservoir for the virus
 in the New World. The fact that West Nile Virus does not usually kill 
the birds that carry it is one piece of evidence supporting the 
hypothesis that it recently arrived in North America, where our 
crows and other birds have yet to develop any immunity. However, in 
order for the disease to be sufficiently widespread in the birds to 
cause a number of bird deaths, and in order for there to be enough 
infected birds to infect enough mosquitoes to produce an epidemic,
the virus had to be present in the bird population for many months,
 perhaps even for years. In southern Europe the virus was present 
for several years before the Romanian outbreak. 

This means that the virus is probably already fairly widespread 
in birds, not  just in crows. Birds, including crows, range 
widely and are not cognizant of county barriers. Thus a bird 
that dies in county A today may have been infected in county B 
last week. Thus, to base county-wide control programs on a single 
dead crow is inappropriate. 

It is interesting to contrast the experience and response in
 New York versus that in New Jersey, which has a statewide 
network of County Mosquito Control Commissions, established
 long ago to control New Jersey’s state "bird," the mosquito. 
New Jersey has extensive experience in conducting surveillance 
programs for viral encephalitis, including the strategic 
placing of sentinel chickens in cages in area where mosquitoes 
are prevalent. The chickens are then regularly tested for virus
 activity. This surveillance program successfully reduced human
and equine infection by Easter equine encephalitis and St. Louis 
encephalitis even though these viruses continued to be active in
 bird populations. 

Although New Jersey abandoned this program years ago because the
 yield seemed to be low, it quickly re-instated surveillance when 
news of West Nile Virus arrived. Moreover, the county Commissions 
have been vigilant in keeping infestations of mosquitoes in check 
through the use of Integrated Pest Management which reduces breeding 
areas in proximity to human activities, introduces natural predators
 to keep mosquito populations in check and uses judicious 
spot-applications of larvicides. Spraying to control adult 
mosquitoes is considered a last resort to be used only when 
local infestations become a serious nuisance or health threat. 

Local health officials, the media, and the public, need to be 
aware of these facts and need to be reminded lest our vigilance 
is reduced and serious disease outbreaks occur. The seductiveness
 of aerial pesticide spraying, devastating to butterflies and 
other non-target species, and frightening and potentially harmful 
to many humans, should be the last, not the first, approach to 
controlling disease spread. 

West Nile Virus is likely to surface again this year, heralded 
by dead crows and great fanfare, and the pressure to use broadcast
 spraying may be powerful indeed. Improved surveillance will show
that the virus occurs over a much wider area than just the New
 York metropolitan region. Spraying is likely to begin much earlier in
the season - June rather than August. If this happens, it is 
likely that the impact on butterflies and other non-target 
species will be severe. 

Alternatively, public health agencies can focus on the
 less flashy, but more effective,strategies for reducing 
mosquito populations. Integrated Pest Management has been very
successful in reducing mosquitoes in New Jersey and elsewhere
 where it has been tried. It can virtually eliminate the risk 
of an ARBO-virus disease, without eliminating many other
 valuable or aesthetically pleasing creatures and without
jeopardizing human health. 


-- 
Neil Jones- Neil at nwjones.demon.co.uk http://www.nwjones.demon.co.uk/
"At some point I had to stand up and be counted. Who speaks for the
butterflies?" Andrew Lees - The quotation on his memorial at Crymlyn Bog
National Nature Reserve