Phylum: PlatyhelminthesPlatyhelminthes (from the Greek , platy, meaning "flat" and, helminth-, meaning "worm"). This Phylum includes more than 13,000 species of free-living and parasitic species.Characteristics of Phylum Platyhelminthes

12/1/2010
Influence of climate on malaria
transmission depends on daily
temperature variation
Krijn P. Paaijmans , Simon Blanford , Andrew S. Bell , Justine I.
Blanford , Andrew F. Read , and Matthew B. Thomas.
Presented by
P.B.TiRUPATHI PICHIAH
Ph.D., Student Dept Of
Human Nutrition
Lets First Understand What is Malaria?
Malaria is a mosquito-borne infectious disease caused by a eukaryotic protist of the
genus Plasmodium.
Widespread in tropical and subtropical regions, including parts of the Americas (22
countries), Asia, and Africa.
250 million cases of malaria/year
Major affected area : sub-Saharan Africa
Commonly associated with poverty
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12/1/2010
History Of Malaria
First described in India during Vedic Period 1600BC and by Hippocrates some 2500 years ago.
Charaka and Sushrutha gave vivid descriptions of malaria and even associated it with the
bites of the mosquitoes.
In 1640, Huan del Vego first employed the tincture of the cinchona bark for treating malaria,
although aborigines of Peru and Ecuador had been using it even earlier for treating fevers.
Morton (1696) presented the first detailed clinical picture of malaria and its treatment with
cinchona.
Lancisi (1717) linked malaria with poisonous vapours of swamps and thus originated the
name malaria, meaning bad air
Gize (1816) studied extraction of quinine from the cinchona bark.
Pelletier and Caventou (1820) extracted pure quinine alkaloids
Laveran (1880) a French physician working in Algeria, first identified the causative agent
for human malaria while viewing blood slides under a microscope.
P.vivax and P.malariae were identified in 1885 by Golgi
Sakharov (1889) and Marchiafava and Celli (1890) identified P.falciparum
Sir Ronald Ross (1897) while working as a military physician in India, demonstrated the
malarial oocysts in the gut tissue of female Anopheles mosquito. This was reported in the
British Medical Journal.
Paul Muller (1939) discovered the insecticidal properties of DDT.
Curd, Davey and Rose (1944) synthesised proguanil for treating falciparum malaria
During the World War II research into antimalarials was intensified.
Chloroquine was synthesised and studied under the name of Resochin by the Germans as
early as 1934
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Short, Granham, Covell and Shute (England) identified tissue forms of P.vivax in the liver.
Tissue stages of P. falciparum, P. ovale, and P. malariae were also identified later on.
Elderfield (1950, USA) synthesised primaquine.
Lysenko (1976-78) formulated a theory on the polymorphism of P.vivax sporozoites.
Bray and Garnham (1982) proposed that some sporozoites in the liver remain latent
(hypnozoites) causing relapses later on.
Quinine has now been completely synthesized. Its synthetic analogue is called
mefloquine..
In 1967, WHO realized that the global eradication of malaria was impossible for a variety
of reasons and the focus shifted to control of the disease.
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Global Temperature Map
Life cycle of Malaria Vector:
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Climate and Malaria
The three main climate factors that affect malaria are temperature, precipitation, and
relative humidity (Pampana, 1969).
Climate predicts, to a large degree, the natural distribution of malaria (Bouma and van der
Kaay, 1996).
Temperature
Temperature affects many parts of the malaria life cycle.
The duration of the extrinsic phase depends on temperature and on the species of the
parasite the mosquito is carrying (Pampana, 1969).
The extrinsic cycle normally lasts nine or ten days, but sometimes can be as short as five
days (Bradley et al., 1987).
As the temperature decreases, the number of days necessary to complete the extrinsic
cycle increases for a given Plasmodium species.
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P. vivax and P. falciparum have the shortest extrinsic incubation times and therefore are
more common than P. ovale and P. malariae (Oaks et al., 1991).
The extrinsic phase takes the least amount of time when the temperature is 27°C
(Pampana, 1969).
The time required for development of the ookinete, the egg of the parasite, in the midgut
of the Anopheline mosquito, decreases as temperature increases from 21°C to 27°C (Patz
et al., 1998).
Below 20°C, the life cycle of falciparum is limited. Malaria transmission in areas colder
than 20°C can still occur because Anophelines often live in houses, which tend to be
warmer than external temperatures.
Larval development of the mosquito also depends on temperature (Russell et al., 1963).
Higher temperatures increase the number of blood meals taken and the number of times
eggs are laid by the mosquitoes (Martens et al., 1995).
The intersections of the ranges of minimum and maximum temperature for parasite and
vector development determine the impact of changes in temperature on malaria
transmission.
The minimum temperature for mosquito development is between 8-10°C, the minimum
temperatures for parasite development are between 14-19°C with P. vivax surviving at
lower temperatures than P. falciparum.
The optimum temperature for mosquitoes is 25-27°C, and the maximum temperature for
both vectors and parasites is 40°C (McMichael et al., 1996). There are some areas where
the climate is optimal for malaria and Anopheles mosquitoes are present, but there is no
malaria.
This is called “Anophelism without malaria” which can be due to the fact that the
Anopheles mosquitoes present do not feed primarily on humans (Bruce-Chwatt, 1985) or
because malaria control techniques have eliminated the parasite .
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Precipitation
Anopheline mosquitoes breed in water habitats, thus requiring just the right amount of
precipitation in order for mosquito breeding to occur.
Different Anopheline mosquitoes prefer different types of water bodies in which to breed
(Nagpal and Sharma, 1995).
Too much rainfall, or rainfall accompanied by storm conditions can flush away breeding
larvae.
Not only the amount and intensity of precipitation, but also the time in the year, whether in
the wet or dry season, affects malaria survival (Russell et al., 1963).
Rainfall also affects malaria transmission because it increases relative humidity and modifies
temperature, and it also affects where and how much mosquito breeding can take place
(Pampana, 1969).
Relative Humidity
Relative humidity also affects malaria transmission.
Plasmodium parasites are not affected by relative humidity, but mosquitoes are.
If the average monthly relative humidity is below 60%, it is believed that the life of the
mosquito is so shortened that there is no malaria transmission (Pampana, 1969).
Wind
Wind may play both negative and positive roles in the malaria cycle because very
strong winds can decrease biting or ovipositing by mosquitoes, while at the same time
extending the length of the flight of the mosquito.
During a monsoon, wind has the potential to change the geographic distribution of
mosquitoes (Russell et al., 1963).
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Daily Temperature Variations - Net Radiation
Diurnal temperature variation is a meteorological term that relates to the variation in
temperature that occurs from the highs of the day to the cool of nights.
The net radiation determines whether the
surface temperature rises, falls, or remains the
same.
net radiation = incoming solar - outgoing IR.
If the net radiation > 0, surface warms ( 6 AM -
3-5 PM)
if the net radiation < 0, surface cools (3-5 PM -
6 AM)
Factors Affecting Daytime Warming - Fundamental Process.
warm air
hot ground
cool air
boundar
y layer
Heat is transported from the hot surface to air molecules very near the hot surface
by conduction.
Heat is then transported further upward by convection - thermals of air.
The layer of air near the earth's surface where most of the daily temperature
variation occurs as a result of the heating/cooling of the ground is called the
boundary layer (1-1.5Km)
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Factors Affecting Daytime Warming Night time cooling - radiation inversion
During the night time hours, there is no SW heating
the ground, so the ground cools rapidly.
hence, there is heat transfer by conduction from the
warm air to the cold ground.
This heat transfer occurs in a shallow layer near the
ground since air is a poor conductor
a "radiation inversion' is formed: a shallow layer of air
near the earth's surface where the temperature
increases with height
average radiation inversion depth is about 100m, but
can vary from 10m -1 km
wind speed land
type humidity
vegetation cover
soil moisture
cloudiness
From the Paper:
Reproductive number (R0),
R0 = ma 2
bce-pS
/pr
where,
m = vector:human ratio, a = vector biting frequency, bc = transmission
coefficients defining vector competence, p = daily vector survival rate,
S= the extrinsic incubation or development period of the parasite within the
vector, and r=recovery rate of the vertebrate hosts from infection.
These parameters relate in some way to mosquito abundance, its biology, or
physiology
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Aim:
Role of temperature (constant and fluctuating) in
1. Growth and dissemination of the P.chabuadi inside the
mosquito.
2. Survival rate of mosquito larva.
3. Gonotropic cycle * length of female mosquitoes.
* The complete cycle from time of feeding to oviposition (Covell et al 1953).
Results and Discussion
Figi. Mean monthly temperature and mean monthly DTR throughout Africa for January, April,
July, and October. Temperature surfaces were generated by interpolation using weather station
data collected between 1960 and1990. For areas where data records were limited, such as in
the Democratic Republic of the Congo, the time period was extended to 2000. The current
geographical limits of malaria transmission are illustrated by the dotted lines.
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12/1/2010
Growth rate and dissemination of P. chabaudi malaria in An. stephensi mosquitoes under
constant and fluctuating temperature regimens. Constant temperatures (dashed red lines) or
temperatures with a diurnal temperature fluctuation of ±6 °C (DTR = 12 °C; solid blue lines).
Fig. 3 Interaction plot of the development time and
survival of the immature stages of An. stephensi under
constant compared with fluctuating temperature
regimens.
(A) Development time (days, solid lines) and survival
(percentage, dashed lines) of mosquito immatures until
they reached the adult stage at a constant 20 °C and at a
mean temperature of 20 °C but with a diurnal
temperature fl uctuation of ±6 °C (DTR = 12 °C).
(B) Data from an equivalent experiment at 27 °C.
Results are given for three different larval densities (■,
0.5, ▲, 1, and • , 2 larvae/cm 2 ).
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12/1/2010
rime (days)
Fig. 4. Cumulative percent survival and gonotrophic cycle length of female An. stephensi
mosquitoes under constant and fluctuating temperature regimens.
(A) Survival at constant 18 °C (dashed red line) compared with survival at
a mean temperature of 18 °C but with a diurnal temperature fluctuation of ±6 °C (DTR = 12
°C; closed blue line). (Inset) The percentage of mosquitoes that completed the gonotrophic
cycle on a given day (on the x axis) at constant 18 °C (red bars) compared with completion
at a mean temperature of 18 °C but with a diurnal temperature fluctuation of ±6 °C (DTR =
12 °C;
blue bars).
(B) (B) Data from equivalent experiments at 24
°C.
The key mosquito-related traits that combine to determine malaria transmission
intensity are all sensitive to daily variation in temperature.
ie
1. parasite infection,
2. parasite growth and development,
3. immature mosquito development and survival,
4. Length of the gonotrophic cycle, and adult survival.
Temperature fluctuation increases relative rate processes under cool conditions and
slows rate processes under warm conditions.
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12/1/2010
Limitations:
Used rodent malaria and one species of mosquito need to extend investigations to
human malaria species and to other important vectors.
These findings caution against standard practice in studies estimating mosquito and/or
malaria climate relations and strengthen arguments for greater ecological understanding of
how infectious organisms respond to the natural environment.
What we learn?
Daily temperature fluctuation on basic aspects of insect and parasite life histories
suggest the need to consider the role of temperature variation for many ectotherms
(other insects, amphibians, reptiles, etc.) and their parasites and pathogens, both for
understanding current biology and the likely impacts of climate change
13

12/1/2010
Beer Consumption Increases Human Attractiveness to
Malaria Mosquitoes
Thierry Lefevre1
', Louis-Clement Gouagna2,3
, Kounbobr Roch Dabire3
’4
, Eric Elguero1
, Didier Fontenille2
Francois Renaud1
, Carlo Costantini2
’6
, Frederic Thomas1,6
1 Gentoque et Evolution det Mattoet mfeaieuset, OMR CNRS/IRO 2724. Mompelllei. France. ZCaucttostoon et Controte des Populations de
Vecteurs. IRO/Uft 016 Montpellier, France, 3 Insritut de Recherche en Soence de la Same, Bobo-Dioulasso, Burkina Faso, 4 Laboratoire de
Parasit olog* et dlntomotogie Medicale. Centre Mura? Bobo-Ooulasw, Burkina Faw, ^Organisation de Coordination pour la lutte centre les
Endemics en Afrique Centrale. Yaounde. Cameroon. dinstitut de Recherche er Biologic Vegetal*. Univefsite de Montreal. Montreal. Canada
Abstract
Background: Malaria and alcohol consumption both represent major public health problems. Alcohol consumption is rising in
developing countries and, as efforts to manage malaria are expanded, understanding the links between malaria and alcohol
consumption becomes crucial. Our aim was to ascertain the effect of beer consumption on human attractiveness to malaria
mosquitoes in semi field conditions in Burkina Faso.
Methodoiogy/Principai Findings: We used a Y tube-olfactometer designed to take advantage of the whole body odour (breath and
skin emanations! as a stimulus to gauge human attractiveness to Anopheles gomblae (the primary African malaria vector} before and
after volunteers consumed either beer (n = 25 volunteers and a total of 2500 mosquitoes tested) or water (n = 18 volunteers and a total
of 1800 mosquitoes). Water consumption had no effect on human attractiveness to An. gomblae mosquitoes, but beer consumption
increased volunteer attractiveness. Body odours of volunteers who consumed beer increased mosquito activation (proportion of
mosquitoes engaging in take-off and up-wind flight) and orientation (proportion of mosquitoes flying towards volunteers’ odours).
The level of exhaled carbon dioxide and body temperature had no effect on human attractiveness to mosquitoes. Despite Individual
volunteer variation, beer consumption consistently increased attractiveness to mosquitoes.
Condusions/Significance: These results suggest that beer consumption is a risk factor for malaria and needs to be integrated into
public health policies for the design of control measures.
Citation: Lefevre T, Gouagna K. Dabire KR, Elguero E Fontenille 0, et al. (2010) Beer Consumption increases Human Attractiveness
to Malaria Mosquitoes. PLoS ONE 5(3): *9546. d0fcl0,1371/joumal.pone0009546
Editor Tom Treqenza, University of Exeter, United Kingdom
Received January 21, 2010; Accepted February 16, 2010; Published March 4. 2010
Copyright: © 2010 Lefevre et al. This n an open-access article distributed under the terms of the Creawe Commons Attribution
License, which permits unrestricted use. distribution, and reproduction in any medium. provided the original author and source are
crecfited.
Funding: The study was Supported by the French National Research Agency (ANR) number 0-0712154)1-01. The funders had no role
in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interest*: The authors have declared that no competing interests exnt.
• E-mail: telefevdemory.edu
Malaria Control with Transgenic Mosquitoes
John M. Marshall, Charles E. Taylor*
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12/1/2010
nature Vol 464 AJilarcb.imfldoiilO.IOM/ialuriOaaM
ARTICLES
Odorant reception in the malaria mosquito
Anopheles gambiae
Allison F. Carey', Guirong Wang", Chih-Ying Su1, Laurence J. Zwiebel2 & John R. Carlson1
The mosquito Anopheles gambiae is the major vector of malaria in sub-Saharan Africa. It locates its human hosts primarily
through olfaction, but little is known about the molecular basis of this process. Here we functionally characterize the Anopheles
gambiae odorant receptor (AgOr> repertoire- We identify receptors that respond strongly to components of human
gduurjnd.that may act in the process of human recognition. Some of these receptors are narrowly tuned, and some salient
odorants elicit strong responses from only one or a few receptors, suggesting a central role for specific transmission channels
in human host-seeking behaviour. This analysis of the Anopheles gambiae receptors permits a comparison with the
corresponding Drosophila melanogaster odorant receptor repertoire. We find that odorants are differentially encoded by the two
species in ways consistent with their ecological needs. Our analysis of the Anopheles gambiae repertoire identifies
Sciei
iceDaiiy
Your source for the latest research news
Web address:
http://www.sciencedaily.com/releases/2010/10/
101020151324.htm
Malarial Mosquitoes Are
Evolving Into New
Species, Say Researchers
ScienceDaily (Oct. 21.2010) — Two strains of Ilie type of
transmission in Africa have evolved such substantial genetic
diflerejDteS-tlMJhex^
avoiding taj^arah£E.b£hiai-teQ.nEw studies published
in the journal Jcvme.
Over 200 million people globally are infected with malaria,
according to the World Health Organisation, and the majority of
these people are in Africa. Malaria kills one child every 30
seconds.
The international research effort, co-led by scientists from
Imperial College London, looks at two strains of the tlnwlKtes
gambiae mosquito. ths type of mosquito primarily
responsible for transmitting malaria in sub-Saharan Africa. These
strains, known as M and S, are physically identical. However, the
new research shows that thefr genetic differences are such that
they appear to be becoming different species, so efforts to control
mosquito populations may be effective against one strain of
mosquito but not the other.
H Hie scientists .nene licit Alien researchers arc dceloping new
ways oI controlling malarial mosquitoes. Ibr example by creating new insecticides
or trying to interfere with their aJ ' z
L ability to reproduce, they need to make sure
that they are ______________________i-ffi-eliv.- in hrslh sirs ms
15

Phylum: Platyhelminthes Platyhelminthes (from the Greek , platy, meaning "flat" and, helminth-, meaning "worm"). This Phylum includes more than 13,000 species of free-living and parasitic species. Characteristics of Phylum Platyhelminthes

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