International Conference on Environment and Health, 22-23 May 2013, Soegijapranata Catholic University, Indonesia
280 surface-air temperature. An increase of
atmospheric greenhouse gas concentrations leads to an average increase of the
temperature of
the surface-tropospher
system IPCC, 2001; Alisjahbana, 2008:34. Annual mean temperature in Indonesia has
been observed as increasing by around 0.3 degrees Celcius since 1990 Sari et al,
2007. Climate change causes changing pattern of
rainfall, temperature, humidity, and wind direction that affecting land and sea
ecosystem. This may lead to health problem, especially deal with disease vector such as
Aedes, Anopheles etc. Barrera, 2006. Climate change affects the continuous
increased number of vector borne disease Munasinghe et.al, 2003. Collwell study
revealed the effect of climate change to infectious
diseases, mainly
arthropode poikilothermic borne disease Collwell et.al,
1998. Increasing temperature shortened reproductive cycle of vectors as well as
extrinsic development of pathogen in the vector, which may lead to high transmission
of several arbovirus disease such as Japanesse enchepalitis and dengue WHO,
1990. Our study aimed to analyze the climate variability and its association to the
incidence of DHF.
MATERIAL AND METHOD
This was an observational study with cross sectional design. Study subject was 26.415
cases of DHF registered in DHO. Data of temperature, humidity and rainfall was
obtained from
Badan Meteorologi,
Klimatologi, Geofisika
Semarang. As
dependent variable was DHF incidence while independent was rainfall, temperature
and humidity. Rank Spearman was used to analyze the correlation between climate and
DHF Sugiyono, 2002.
RESULTS AND DISCUSSION
Average of DHF incidence 2002-2011 was 220month, rainfall 193 mmmonth and
humidity 76. Temperature tends to constant in 27.7
o
C, no fluctuation observed BMKG, 2002-2011.
a. Correlation of rainfall and DHF
incidence
There was significant correlation of rainfall and DHF during 2002-2011 p-value=0,001
and r=0,304.
Coefficient correlation
r=0.304 indicated positive relation, which means increasing of rainfall followed by
increasing of DHF incidence. The result was similar with Andriani study, which revealed a
significant relationship between
climate factors and DHF incidence during 1997-2000
in Jakarta Andriani, 2000. Consistent results on the relationship between rainfall and DHF
have also seen in Southeast Asia. Peak of transmission occurs in high rainfall and
temperature when habitat water storage container of
Aedes aegypti
is abundant
.
Although ini some places the peak occurs
International Conference on Environment and Health, 22-23 May 2013, Soegijapranata Catholic University, Indonesia
281 before rainy season and increase during
transitional season Gubler, 1998. Rainfall will added puddle of water as
mosquito breeding places. In dry season plenty of scraps such as used cans, used
plastic glasses, used tired etc was discardes or irregularly placed. During transitional season,
all the scraps may become water reservoir and act as breeding places. In the rainy season,
Aedes female mosquitos acquire plenty of freshwater to breed from every curved object
or curve of trees. This due to Aedes bionomic that prefers clean water to lay eggs. Especially
in cloudy weather when female mosquito stimulated to lay eggs Irpis, 1972.
An
Aedes
can lay 100-300 eggs, causing mosquito
population increase
rapidly. Mosquitos need blood for their eggs
maturation and there by increasing the probability to bite. That is why the increase in
mosquito population in the beginning of rainy season will be followed by the increase of
DHF Irpis, 1972.
b. Correlation of temperature and DHF
incidence
The result showed no significant correlation between temperature and DHF incidence
during 2002-2011 p-value = 0,235 and r=- 0,109. This is in contrast with Andriani
200 400
600 800
1000 1200
1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 2002
2003 2004
2005 2006
2007 2008
2009 2010
2011 100
200 300
400 500
600 700
800 900
D H
F in ci
de nce
case s
R ai
nf al
l m
m m
on th
F i g u r e 1 . C o r r e l a t i o n b e t w e e n r a i n f a l l a n d D H F i n c i d e n c e i n S e m a r a n g C i t y
-----DHF incidence ------ Rainfall
International Conference on Environment and Health, 22-23 May 2013, Soegijapranata Catholic University, Indonesia
282 study that concluded significant relationship
of climate factors and DHF incidence in Jakarta 1997-2000. Increase in temperature
will affect bionomic change of mosquito population
in biting
rate. Besides,
reproductive activities also change, which characterized by rapid proliferation Ditjen
PP PL Depkes RI, 2009.
Temperature can also modify vector growth and alter biting rate. Season transitional
changes transmission time. Vector may adapt to temperature change by shifting their
geographical distribution WHO, 2003. Increasing temperature shorten time needed to
develop from egg to adult. In 26
o
C, virus need 25 days to reach saliva gland and ready to
transmit throughout mosquito lifetime. On the contrary, they only need 10 days in
temperature of 30
o
C. This will speed up the probability of dengue transmission. The faster
the mosquito breeding, the higher the risk of epidemik.
Larval development is mainly influenced by temperature and food availability in the
breeding places. In the laboratory setting with optimal condition sufficient food and water
temperature of
25-27
o
C the
larval development need 6-8 hari. When the water
temperature is more than 28
o
C or less then 24
o
C the larval develpoment become longer. At the temperature of 31
o
C, 24
o
C, 20
o
C, 18
o
C and 16
o
C the larval development is 12, 10, 19, 24 and 29 days respectively. Larvae die in
temperature less than 10
o
C or more than 40
o
C. In a fluctuative temperature, the development
is faster compare to constant temperature Sungkar, Saleha, 2005.
Mosquitos survive in low temperature, but its metabolism decrease and even stopped in
critical temperature. In high temperature 35
o
C physiology
process will
also decrease. Average optimum temperature for
development is
25
o
C-27
o
C. Mosquito‟s
developent stops in temperature less than 10
o
C or more than 40
o
C Depkes RI, 2000. Environmental temperature affects extrinsic
incubation period EIP of dengue virus in the mosquito. Increase temperature shorten EIP
and increase probability of transmission. Increasing environmental temperature affects
rapid eggs
hatching UNDP,
2007. Theoritically, environmental temperature may
also affect biting rate Djunaedi, 2006; Brisbois and Ali, 2010.
However, our study showed no significant correlation
of temperature
and DHF
incidence. This probably due to the condition of Semarang temperature during 2002-2011
that still in optimum range for mosquito growth and development. It is also possible
that the mosquito infectivity was low, so it does not affect DHF incidence.
International Conference on Environment and Health, 22-23 May 2013, Soegijapranata Catholic University, Indonesia
283
c. Correlation
