Climate change is causing rising global temperatures which can affect vectors and the diseases they transmit in several ways. Higher temperatures can increase vector populations, shorten pathogen incubation periods in vectors, and expand the transmission seasons or geographic ranges of certain diseases. Changes in precipitation patterns from climate change can also impact vectors by altering larval habitats or humidity levels. Models project that 5-30% of parasite species could face extinction due to climate-driven habitat loss, with potentially profound effects on ecosystems since vectors play important regulatory roles and support biodiversity. Diseases spread by mosquitoes, ticks, and other arthropods already cause millions of cases annually worldwide. Climate change may further drive emergence and reemergence of certain vector-borne diseases as temperatures rise

1. Affect of climate change on
vectors and their diseases
Raja Zabeeh Ullah Khan
2011ag2395

2. What is Climate Change?
• Climate change refers to any change in climate
over time, whether due to natural variability
or as a result of human activity (IPCC,2007).
• Whereas climate means:
Average trend of weather patterns for a given
location (averages over a long time period).

3. Change or Controvery
• CLIMATE has always been changing and this Change is
NATURAL. EARTH has witnessed ice ages in past which
are examples of Change in Climate.
• Naturally occurring Greenhouse Gases include WATER
VAPOUR, CARBON DIOXIDE, OZONE, METHANE and
NITROUS OXIDE, AND TOGETHER CREATE A NATURAL
GREENHOUSE EFFECT.
• However, Human activities are causing Greenhouse
Gas levels in the atmosphere to increase and thus
Causing in GLOBAL TEMPERATURE. This increase in
mean Global Temperature is called GLOBAL WARMING.

4. Increase in Temperature over century

5. What are vectors?
• Vectors are insects (mosquitoes, ticks, fleas,
black flies and sandflies) that carry infectious
agents such as protozoa, bacteria and viruses.

6. Arthropod vectors
• Lice - epidemic typhus
• Kissing bugs – Chagas disease
• Fleas – plague
• Sand flies – Leishmaniasis
• Black flies – River blindness
• Mosquitoes – malaria, dengue, yellow fever, Japanese
encephalitis, West Nile encephalitis,
filariasis
• Tsetse flies – African sleeping sickness
• Chiggers – scrub typhus
• Ticks – Lyme disease, Tick-borne encephalitis, Rocky
Mountain Spotted Fever.

7. Climate Destruction v/s Parasite
Destruction
• conservative model projections suggest that 5
to 10% of these species are committed to
extinction by 2070 from climate-driven habitat
loss alone
• Accounting for host-driven co-extinctions,
models predict that up to 30% of parasitic
worms are committed to extinction

8. Climate change v/s Ecosystem
• If vectors/parasites face extinction
• The cascading impacts on ecosystems are
likely to be profound
• Many vectors/parasites play an important
immuno-regulatory role in host populations
• A higher diversity of vectors/parasites can act
as a partial buffer against the emergence of a
virulent pathogen .

9. Climate change v/s Ecosystem
• Parasites make up the majority of the biomass
in some ecosystems, outweighing predators
sharing their environments by a factor of 20 to
1.

10. Climate change v/s Ecosystem
• Previous work has also pointed to the merits
of vectors as regulators and connectors in
resource-consumer webs, in which they can
sometimes constitute more than 75% of the
total links and in which their occasional role in
altering host behavior can be critical to the
flow of biomass between trophic levels

11. • Despite high local extinction rates, parasite
richness could still increase by an order of
magnitude in some places, because species
successfully tracking climate change invade
temperate ecosystems and replace native
species with unpredictable ecological
consequences.

12. Malaria: Generality
• It has estimated that, in 2009, the number of cases of
malaria was 225 million and the number of deaths was
781,000, among which 50-100 million were dengue
cases, and 120 million were filariasis cases. The toll
from other vector-borne diseases like trypanosomiasis,
leishmaniasis, Japanese encephalitis, onchocerciasis
and yellow fever add more millions of cases each year.
It has been estimated that these diseases due to all
parasitic and infectious diseases, represent 17% of the
global disease burden, in terms of disability-adjusted
life years

13. Factors Affecting
• The ecology, development, behaviour, and
survival of insects and the transmission dynamics
of the diseases they transmit are strongly
influenced by climatic factors.
• Temperature
• Rainfall
• humidity
• wind
• The same factors also play a crucial role in the
survival and transmission rate of the pathogens.

14. Factors Affecting
• The main parameter that affects the rate of
multiplication in the insect is temperature. When
the temperature increases, it tends to cause
• an upsurge in the growth rates of mosquito
populations
• decrease the interval between blood meals,
• shorten the incubation time from infection to
infectiousness in mosquitoes
• accelerate the virus/parasite evolution rate

15. Temperature Effects on Vectors and
Pathogens
• Vector
– Survival decrease/increase depending on the species.
– Changes in the susceptibility of vectors to some
pathogens.
– Changes in rate of vector population growth.
– Changes in feeding rate and host contact.
• Pathogen
– Decreased extrinsic incubation period of pathogen in
vector at higher temperatures.
– Changes in the transmission season.
– Changes in geographical distribution.
– Decreased viral replication.

16. Precipitation Effects on Vectors
• Vector
– Survival: increased rain may increase larval habitat
– Excess rain can eliminate habitat by flooding.
– Low rainfall can create habitat as rivers dry into pools (dry
season malaria).
– Decreased rain can increase container-breeding
mosquitoes by forcing increased water storage.
– Heavy rainfall events can synchronize vector host-seeking
and virus transmission.
– Increased humidity increases vector survival and vice-
versa.

17. Climate change & Vector Distribution
• The anticipated changes to our climate are;
• Increasing temperatures
• Changes in precipitation
Leaving some areas more drought prone;
greater climate variability; and extreme weather
events

18. Climate change & Vector Distribution
• These climatic changes may drive the emergence
and re-emergence of vector-borne diseases in
several ways:
• (i) pole-ward spread of vectors and vector-borne
pathogens as climate warms in temperate zones
• This process may also be accompanied by pole-
ward contraction of the most equatorial limits of
these species if temperatures become too hot for
them;

19. Climate change & Vector Distribution
• (ii) greater likelihood and frequency of introduction
and endemic establishment of tropical and subtropical
vector borne diseases in to currently temperate regions
by a combination of
• (a) rising temperatures in the receiving location,
increasing vector and vector-borne pathogen survival;
• (b)increasing abundance of vectors and vector-borne
pathogens in tropical and subtropical source locations;
and
• (c)increasing rates of import of (particularly) tropical
and subtropical vector-borne pathogens due to
increased climate change-related human migration

20. Climate change & Vector Distribution
• (iii) re-emergence of endemic vector-borne
diseases associated with increasing
temperatures and weather and climate
variability and
• (iv)emergence and fixation of novel genotypes
of vector-borne pathogens as a result of
climate change- driven changes to animal host
and vector dynamics

21. • Thank You for listening