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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 103, Num. 7, 2008, pp. 627-628
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Memórias do Instituto Oswaldo Cruz, Vol. 103, No. 7, November, 2008, pp. 627-628
EDITORIAL
Rio de Janeiro
against Aedes aegypti: yellow fever in 1908 and dengue in 2008 - Editorial
Ricardo
Lourenço-de-Oliveira
Editor
Code Number: oc08115
In 2008, Brazil
is experiencing its second most devastating dengue epidemic, with 734,000 reported
dengue cases through October this year. However, this represents the most severe
dengue epidemic in terms of deaths: 212 deaths were recorded, primarily in children.
Deaths have been mainly reported for infections with dengue virus type 2 (DENV-2)
in endemic areas that had previously experienced epidemics of DENV-3. Southeastern
and Northeastern Brazilian cities have been most affected, and in some cities,
the incidence has increased more than 2,000-fold. Again, the "eye of the hurricane"
has been in Rio de Janeiro, located in the Southeast, the most "developed" region
of Brazil. A favourable climate for reproduction of the mosquito vector Aedes
aegypti, degradation of environmental conditions, low income levels, violence,
and drug fiefdoms on hillside slums, political quarrels, have all hampered efficient
control activities, leading to a deterioration of public services and minimized
integrated activity with regard to sanitation, education, communication, and
dengue vector control, resulting in the emergence of Rio de Janeiro as a major
point of dengue introduction and dissemination into the country. Additionally,
and unfortunately, almost no results from scientific investigations on the dengue
vector have been taken into account in local dengue control campaigns.
This is similar
to circumstances over 100 years ago in which the physician Antonio Gonçalves
Peryassu published a monograph in Rio de Janeiro, whose data encouraged the
fight against Ae. aegypti. The two main differences between this historical
scenario and the current one are the vector carried virus (yellow fever in 1908,
and dengue in 2008) and the strong influence of Oswaldo Cruz, the director of
the Instituto de Manguinhos and yellow fever mosquito campaigns that resulted
in implementation of laboratory and field scientifically proven results in the
mosquito control strategies.
Peryassu's monograph
entitled "Os Culicideos do Brasil" (Culicids from Brazil) is comprised
of 407 pages containing more than 60 black and white and colour plates, as well
as a detailed mosquito map of almost every street in the city of Rio de Janeiro
in 1906. This comprehensive work on Brazilian and South American mosquito systematics
and biology was produced over a period of two years of investigation at the
Instituto de Manguinhos, which was named Instituto Oswaldo Cruz in 1908. Peryassu's
work was clearly driven by the need for scientific knowledge regarding Ae.
aegypti biology and behaviour. Transmission of the yellow fever virus by
Ae. aegypti was discovered only few years earlier Peryassu's first field
and laboratory assays, which were initiated in 1906. Prior to this work, all
that was known about Ae. aegypti's behaviour and biology had been reported
by the US Army Yellow Fever Commission in Cuba. Almost nothing was known about
Ae. aegypti behaviour and biology in the environmental and climatic conditions
of Rio de Janeiro. In addition to the substantial data describing Stegomyia
calopus (= Ae. aegypti) and other mosquito species provided in three
large chapters in the first section of his monograph, Peryassu also described
his numerous laboratory experiments examining the biology of this mosquito in
the second part of the book. He sought to discover the weakness in the mosquito
life cycle that could be exploited in control campaigns. Some of the main assays
and field observations described in Peryassu's work include resistance of eggs,
larvae, and pupae to desiccation, co-habitation of Ae. aegypti with other
immature native mosquitoes in several breeding environments, and larval and
pupal mortality due to exposure to seawater, sodium chloride, and mercury chloride.
He also pointed out that the most productive habitats for immature Ae. aegypti
were large and permanent water-holding containers. Peryassu demonstrated that
Ae. aegypti larvae survived exposure to soap at concentrations regularly
used in tanks for washing clothes (and subsequently held in drains). Furthermore,
he found that when the local temperature dropped below 20ºC, Ae. aegypti
development and reproduction were strongly affected. "In nature, a single night
with temperature dropping to 20ºC is enough to delay and disrupt larval hatching
and development", reinforced Peryassu. Additionally, Peryassu's incredibly detailed
map of the distribution Ae. aegypti in the city of Rio de Janeiro (supplementary
data) shows that the mosquito distribution is clearly influenced by human population
density. Indeed, Peryassu emphasized that Ae. aegypti was considerably
more frequent in the populated city centre and that its distribution matched
that of yellow fever cases.
Peryassu's monograph
was assembled under the guidance of Arthur Neiva, with some advices from Adolpho
Lutz. He received encouragement and sponsorship from Oswaldo Cruz, who was particularly
interested in mosquito studies and the role of mosquito species in human disease
transmission. Oswaldo Cruz himself wrote (and possibly illustrated) the first
paper published at the Instituto Oswaldo Cruz on a new species of anopheline.
In 1903, Oswaldo Cruz also launched the anti-yellow fever mosquito campaign,
which culminated in the control of yellow fever epidemics in Rio late in the
1920s. Ae. aegypti was considered eradicated from Brazil in 1955 after
a continental campaign.
Currently, 100
years later, Rio's main enemy is once again Ae. aegypti. Again, the battle
must be won not only by the health authorities and governmental anti-mosquito
campaigns, but also by scientists. Since a dengue vaccine is still not available,
control strategies have been focused on mosquito population reduction. An efficient
campaign against Ae. aegypti must be based on scientific investigations,
taking into account that large metropolitan areas such as Rio have spatial heterogeneity
in terms of the vector population. This obviously makes control strategies more
complex. Additionally, dengue control will require much more than a health-based
approach. For instance, the strategy must be constructed with inputs and actions
from education and sanitation backgrounds. Scientific investigations, especially
those conducted in networks with multidisciplinary approaches, must be utilised
as the primary method of gaining information in support of an efficient control
campaign in Rio de Janeiro. As Oswaldo Cruz and AG Peryassu suggested 100 years
ago, funding of scientific investigations and promotion of interactions between
the authorities involved in control at all levels and scientific workers is
essential in the fight against mosquitoes during the next dengue transmission
season.
Ricardo
Lourenço-de-Oliveira
Editor
Copyright 2008 - Instituto Oswaldo Cruz - Fiocruz
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