bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
The effect of climatic conditions on malaria epidemics in Swat
Valley.
Submitted by Sohail Khan*, Submission date: 31/03/2017
*Student at Center of Biotechnology and Microbiology, University of Swat.
Abstract:
The vector for the transmission of malaria is a mosquito and like all diseases which are
transmitted through mosquitoes are affected by climatic conditions. In the present study, such
type of investigation was done to find the influence of different climatic changes such as
temperature and humidity on the incidence of malarial cases in Swat, Khyber Pakhtunkhwa,
Pakistan from 2000 to 2016. The data relating to malarial cases and climate conditions were
collected from District Health Officer (Saidu Sharif) and Meteorological Center respectively.
Statistical analysis of the data was done by using MS Office software i.e. MS Excel. It was found
that with the increase in temperature and humidity, an increase in the incidence of Malaria
occurred and vice versa. The effect of global warming and the increasing temperature could
become an alarming factor in deciding the fate of malarial epidemics.
Key words: Malaria, Plasmodium, Anopheles, Temperature, Humidity, Swat.
1. Introduction:
One of the most drastic parasite is responsible for causing Malaria all over the world. Malaria
has settled in 108 countries of the world and in 2015 it had caused infections in about 200
million people; of which about half a million were reported dead [1]. The protozoan parasite that
causes Malaria belongs to the genus Plasmodium. Five species of the genus are responsible for
causing infections in humans. Among which the most dangerous is P. falciparum because it is
responsible for most of the infections in Africa and its mortality rate is high. In humans the other
four causative agents of Malaria are P. ovale, P. malariae, P. vivax &, also P. knowlesi which is
a monkey malaria but can affect humans in part of Southeast Asia [2].
In 1880, Charles Laveran first discovered this parasite in RBCs. He found it while he was
working in Algeria at Army Station and later proposed that the protozoan has a disease causing
ability [3]. In 1898, it was found that malaria can be transmitted from bird to bird through the
salivary glands of the mosquito, first reported and concluded by Ronald Ross [3]. During 1899
two Italians named Giuseppe Bastianelli and Amico Bignami found that this protozoan is
transmitted from human to human via female mosquito named Anopheles [4].
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
The female mosquito Anopheles spreads the infection through sporozites when it bites an
individual, these sporozoites are transmitted when this mosquito is blood feeding on a human.
The sporozoites are specialized structure they go on to liver cells (hepatocytes) and starts
division. Once a sporozoite establishes itself it can produce 10k to 30k merozoites within a single
liver cell in 5-8 days. When the hepatic cell burst several merozoites start to invade RBCs. In
about 48 hours, P. falciparum and P. ovale completes its asexual cycle in the blood while it takes
72 hours for P. malariae and 24 hours for P. knowlesi . The parasite first consumes the contents
from erythrocytes while living intracellular in them and then change the cell membrane as such
as to use it as a mean of transportation, they expose the cryptic surface antigens and introduce
newly derived proteins from the parasite into the cell and also through lipid mediated
crystallization they dispose of toxic haem (waste product) to biologically inert malarial pigment
(haemozoin). In an immunocompromised individual the rate of the parasite’s population increase
by six times to twenty time per cycle [5]. The detection by microscopy or other rapid diagnostic
test becomes possible only when there are roughly 100 million parasites in an adult’s blood
(50/μL parasitic density), from here on the symptomatic stage of infection develops. It takes
about 12-14 days for incubation of malaria from the time of the mosquito’s bite [6]. It is clear
that the infection and harm is a result of the effects of erythrocytes parasitisation and demolition
and also the reaction of the host. Some parasites in the blood develop into sexual forms known as
gametocytes these gametocytes spreads malaria into the mosquitoes.
Pakistan is affected by malaria throughout its history, the areas where it is most prevailed are
Baluchistan, Sindh, Khyber Pakhtunkhwa and especially FATA [3]. 64% of the malarial
infections in Pakistan are due to P. vivax and 36% due to P. falciparum [6]. MDSP (a program
specifically dedicated to Malaria) registered 127,825 cases in Pakistan during the period 2010
[7]. Malaria, due to its high rate, is still a major health concern in KPK affecting the areas Bannu,
Buner, Lakki, Kohat, D.I.Khan, Malakand, Swat and Shangla. These areas are at high risk [7].
The reason why malaria emerged and spread is so fast in Pakistan is because of the Afghan
refugees who migrated during Soviet War to Pakistan and especially to KP, they didn’t have
enough facilities and hence they were living in camps, they couldn’t use nets for their prevention
from the mosquitoes as a result they were prone to the parasite and later 150,000 cases were
reported in refugees and the malarial parasite started to appear in the people of Pakistan [8].
The malarial incidence in Swat is no different than the rest of KP. From 2000-05, 772 cases were
reported and from 2006-10, 846 cases were reported while from 2011-15 a total of 1705 cases
were reported [9].
Those diseases which transmit through mosquitoes are mainly subjected to climatic conditions.
Fluctuations in temperature and humidity may cause undesirable effect on its rate of growth and
division. Mosquitoes breed mainly in standing water, so a decrease in temperature causes a fall
in the growth of the parasite and mosquitoes and with increase its growth and influence
increases. Despite the fact that climatic conditions plays a huge role in its course of life and
pathogenicity but a disease requires a host, vector and environmental conditions to properly
transmit [10]. The theme of this study was to find the effect multiple climatic factors (i.e.
Temperature and Humidity) on the epidemics of Malaria in Swat Valley.
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
2. Methods and materials:
The study was aimed to find out the occurrence of malaria in the people of Swat and to update its
epidemiology on the basis of climatic conditions i.e. Temperature and Humidity.
2.1. Study Area:
Valley Swat of Khyber Pakhtunkhwa is the place where this study was conducted.
2.2. Data Collection
2.2.1. Malarial cases:
Collection of data was approved by the authorities of the Saidu Central Hospital (public) and was
collected from multiple hospitals (both in public sector & private) and labs and also a collective
data report from the district health officer’s office.
2.2.2. Meteorological data:
Data on minimum and maximum temperature and humidity was obtained from the department of
Meteorological Research Center of Pakistan.
2.3. Data analysis:
Graphs and tables were made by the Excel program of MS Office 2013, to find correlational
statistics of malarial incidence and climatic conditions (temperature and humidity).
3. Results:
By dividing the data on the basis of time into groups we can determine the epidemics of Malaria
and how it is affected by climate change.
3.1. Correlation between the number of Malarial cases and Climatic conditions from 200005:
The number of malarial cases that were reported during this duration were 772 and the range of
temperature and humidity during this period were 19-31 degrees Celsius and 20-40%
respectively. However, when the data is broken down, from June to September when the
temperature was 28 degrees Celsius and humidity is 40% the number of cases were very high
(300 cases) but with low temperatures and humidity the number of malarial cases drop as seen in
the months of January to March, a total of 100 cases with 19 degrees Celsius and 20% humidity.
Similarly from October to December when the temperature was 15 degrees Celsius and humidity
was 20% the cases of Malaria were 100. An increase in temperature and humidity causes
increase in its incidence as seen from April to June, when the temperature was 31 degrees
Celsius and humidity was 24%, the number of cases were 272. (Figure 1.0, 1.1 and Table 1.0)
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
Table 1.0
Months
(2000-05)
Malarial
Cases
Temp ºC
Humidity (%)
JAN-MAR
19
100
20
APR-JUN
31
272
24
JUL-SEP
28
300
40
OCT-DEC
15
100
20
Effect of Climatic Change on Malarial Incidence
from 2000-05
350
300
250
200
150
100
50
0
January to March
April to June
Temp ºC
July to September
Malarial Cases
October to
December
Humidity (%)
Figure 1.0
Correlation between the number of Malarial cases and Climatic conditions from 2000-05
Bar Represtation of the effect of Climatic Change
on Malarial Incidence (2000-05)
350
300
272
300
250
200
150
100
100
50
19
100
20
31
28
24
40
15
20
0
January to March
April to June
Temp ºC
July to September October to December
Malarial Cases
Humidity (%)
Figure 1.1
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
3.2. Correlation between the number of Malarial cases and Climatic conditions from 200610:
From October to December when the temperature was 17 degrees Celsius and humidity was 21%
a total of 109 Malarial cases were reported, but when the temperature and humidity collectively
reached to its extreme points during the period from June to September, there was a huge boost
in the incidence of Malaria as 325 cases were reported, the temperature and humidity during this
period were 29 degrees Celsius and 42% humidity respectively. In the middle two periods the
cases of Malaria was as such; from January to March, with 21 degrees Celsius and 23%
humidity, 160 cases were reported and from April to June 306 cases were reported when the
temperature and humidity were 33 degrees Celsius and 27% respectively. (Figure 2.1, 2.2 and
table 2.0)
Table 2.0
Months
(2005-10)
Malarial
Incidence
Temp ºC
Humidity (%)
JAN-MAR
21
160
23
APR-JUN
33
306
27
JUL-SEP
29
325
42
OCT-DEC
17
109
21
Effect of Climatic Change on the Incidence of
Malaria from 2005-10
350
300
250
200
150
100
50
0
January to March
Temp ºC
April to June
July to September October to December
Malarial Incidence
Humidity (%)
Figure 2.0
Correlation between the number of Malarial cases and Climatic conditions from 2005-10
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
Bar representation of the effect of Climate
Change on the incidence of Malaria (2005-10)
350
325
306
300
250
200
160
150
109
100
50
0
21
33
23
January to March
Temp ºC
29
27
April to June
42
17
21
July to September October to December
Malarial Incidence
Humidity (%)
Figure 2.1
3.3. Correlation between the number of malarial cases and climatic conditions from 201015:
The relation of climatic conditions and malarial incidence was no different than the ones reported
in the earlier periods. During the time period of April and June when temperature rose to its
extreme 37 degrees Celsius and humidity were measured at 29% the prevalence of malaria
became a huge concern as it affected a total of 700 individuals. While this incidence dropped
slightly when the temperature dropped to 32 degrees Celsius (70% humidity) during June and
September, the total cases reported were 600. From October to December when the temperature
and humidity were 19 degrees Celsius and 24% respectively, 200 cases were reported. The
period between January and March had seen 205 cases due to the 23 degrees Celsius temperature
and 26% humidity. (Figure 3.0, 3.1 and table 3.0)
Table 3.0
Months
(2010-15)
Malarial
Incidence
Temp ºC
Humidity (%)
JAN-MAR
23
205
26
APR-JUN
37
700
29
JUL-SEP
32
600
70
OCT-DEC
19
200
24
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
Effect of Climatic Change on the Incidence of
Malaria from 2010-15
800
700
600
500
400
300
200
100
0
January to March
April to June
Temp ºC
July to September October to December
Malarial Incidence
Humidity (%)
Figure 3.0
Correlation between the number of Malarial cases and Climatic conditions from 2010-15
Bar representation of the effect of Climate
Change on the incidence of Malaria (2010-15)
800
700
700
600
600
500
400
300
205
200
100
0
23
200
37
26
January to March
Temp ºC
29
April to June
32
70
19
24
July to September October to December
Malarial Incidence
Humidity (%)
Figure 3.1
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
4. Discussion:
The derivative of the current study shows that increase in temperature and humidity is directly
proportional to the incidence of Malaria in Swat, Khyber Pakhtunkhwa. At the time of writing no
such study was being conducted before, so to the best of our knowledge, for the first time such
study was conducted as to find the influence of climatic conditions on the incidence of malaria in
Swat. Malarial transmission is dependent on a lot of factors such as the presence of the mosquito,
to,
presence of plasmodium in the Anopheles mosquito and proper climatic conditions (temperature
and humidity) for it to grow and cause infection of a higher degree [11]. Our results are in no
contradiction to the various other studies. For instance, same kind of correlation was being
observed in a study conducted in Africa from 1990-2000, they found that high temperature and
high humidity caused an increase in the incidence of malarial cases in Africa [12]. Multiple
studies showed the same outcome, they found that malaria was more prevailed in those areas
which were warmer as compared to the less warm areas. The correlation between climatic
conditions and malaria was found by a model called spatiotemporally validated malaria
transmission model, through this model transmission patterns and incidence in regard to climatic
conditions was found in Africa [13]. Also with the increase in temperature and humidity, an
increase in the growth of Anopheles was found.
5. Conclusions:
A positive correlation was found in our present study, malarial cases have been observed with
the change in temperature and humidity (climatic conditions). As the temperature and humidity
increased, the malarial cases increased as well and vice versa. Therefore it is concluded that high
h
temperature and humidity (warm areas) favors the spread of malaria through mosquito.
Temp. ∝ Malarial incidence
1800
29
1600
28
1400
27
1200
26
1000
25
800
24
600
400
23
200
22
0
21
2000-05
2005-10
Total Cases
2010-15
Mean Temp. (°C)
Figure 4.0
Temperature is directly proportional to the epidemics of Malaria
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
Humidity ∝ Malarial Incidence
1800
40
1600
35
1400
30
1200
25
1000
20
800
15
600
400
10
200
5
0
0
2000-05
2005-10
Total Cases
2010-15
Humidity (%)
Figure 4.1
Humidity is directly proportional to the epidemics of Malaria
Time
Total
Mean
Cases
Temp.
(°C)
2000-05
772
23.25
2005-10
900
25
2010-15
1705
27.75
bioRxiv preprint first posted online Mar. 31, 2017; doi: http://dx.doi.org/10.1101/122754. The copyright holder for this preprint (which was not
peer-reviewed) is the author/funder. It is made available under a CC-BY 4.0 International license.
References:
1. World report about Malaria by W.H.O in 2015.
2. Kantele et al., A review of the emergence of fifth human parasite of malaria, P. knowlesei
2011
3. Control of Malaria, Zainab et al. 2012
4. Sylvie et al, Biodiversity of Malaria in the world.
5. Von Seidlein et al., The Clinical outcome of P. falciparum in the children of Africa. Trial
basis on a large scale 2012.
6. Aarons et al., Damage caused by P. falciparum if it goes untreated in the adult human
2002.
7. WHO website; insights on Malaria: www.who.int
8. Shehzad Zareen et al., Journal of entomology & zoology.
9. Data collection from various labs and hospitals of Swat Valley.
10. Hales et al., 2002
11. Barnet et al,. Variability in the temperature of air on the basis of climate models and its
effect on Malaria 1999.
12. Rogers et al., Epidemiology of Malaria in African Areas on the basis of Climate change
2002
13. Frank et al, the effects and influence of climate on the emergence of Anopheles.