Climate change can impact the transmission of zoonotic diseases in several ways. Warmer temperatures allow vectors like mosquitoes and ticks to survive in new areas, increasing transmission of diseases. Increased rainfall can create more breeding sites for mosquitoes and flooding events, raising risks of water-borne diseases. Changes in animal migration patterns and environments from climate change can spread zoonotic pathogens over longer distances. A variety of zoonotic diseases may see changed prevalence and transmission under climate change conditions through these types of environmental and ecological impacts.

1. Climate change
&
zoonoses
Assignment
VPE-603
Submitted by:
Safier Ahmad Ganiee
M-5849

2. Introduction
Weather:
It is the continuously changing condition of the atmosphere,
usually considered on a time scale that extends from minutes
to weeks.
Climate:
It is the average state of the lower atmosphere, and the
associated characteristics of the underlying land or water, in a
particular region, usually spanning at least several years.
CLIMATE CHANGE:
“Climate change refers to any change in climate over time,
whether due to natural variability or as a result of human
activity. ” (ref: IPCC, 2007)

3. Source: ILRI
zoonoses
 Of 25 major human diseases, 17 are zoonoses.
 Of 1500 human infectious diseases, about 65% zoonotic.
 One new disease emerges every 7 months.
 75% of the emerging diseases have zoonotic potential
Source: ILRI
Source: ILRI

4. Epidemiological triad
Environment
AgentHost

6. Effect of temperature
With warmer climates and decreasing snowfall, the
protective environment provided by snow is removed and
rodents seek shelter within human habitats .
e.g. increasing transmission of hanta virus, as seen in Scandinavia
On mosquitoes
• increased activity
• increased reproduction
• faster digestion of blood
• increased frequency of bites
e.g. outbreaks of Japanese encephalitis in India
On rodents

7. Contd……..
• Warmer climates allow ticks to survive at higher latitudes and
altitudes.
• Humans, may be at higher risk for tick bites, as ticks will bite
earlier and for longer periods.
e.g. Lyme disease in Himalayan region, CCHF in spring season
• Sand-flies are more active at higher temperatures .
• Take more frequent blood-meals .
• In turn increases transmission of disease.
e.g. spread of leishmaniasis
On ticks
On sand-fly

8. Rainfall pattern
• Increased precipitation creates more potential breeding sites for
mosquitoes.
• The vegetation is dense after rainfalls and this provides shelter and
resting grounds for vector
• Heavy rainfall and larval development creates increased vector
capacity and outbreaks occur if vertebrate reservoirs are available.
• Increased rainfall leads to more crops and food which may increase
rodent populations and rodent-borne zoonoses.
• Flooding increases the risk of water-borne zoonoses.
e.g. Outbreaks of Rift Valley fever (RVF) are associated with periods
following heavy rainfall.

9. Soil conditions
 Soil moisture is a factor in the developmental stages of ticks,
with mortality related to dry conditions and soil evaporation
Hyalomma ticks, the vector for Crimean-Congo haemorrhagic fever, are more
adapted to surviving in dry conditions than other ticks .
 Optimal soil factors include humus rich, high calcium and
alkaline (pH>6.1) conditions for spore survival

10. Water borne zoonoses:
Water borne and food borne diseases are a major cause of
mortality world wide
Increased prevalence of echinococcosis,
taeniosis, and toxoplasmosis.
Heavy rainfall
Faecal matter contamination of
surface water
Association between warmer temperatures
and the occurrence of disease suggests that
rates of waterborne and food-borne illnesses
are likely to increase with rising temperatures.
e.g. Warm water in disseminating cholera in
the Ganges river delta
Wide spread concern about the potential impact of global climate change on the distribution
and burden of cholera and other infectious threats in the developing world.
e.g. apperance of Vibrio cholerae 0139 Bengal strain in South India

11. water borne parasitic zoonoses:
 An increase of a few degrees in environmental temperatures may lead to
marked increases in cercarial emergence from snails (first intermediate
host).
 Trematodes and helminths whose life cycles include a larval stage in the
environment or in an invertebrate host may be more susceptible to climate
change impact (29) than trematodes and helminths in whose life cycle such
phases are absent.
 The prevalence of zoonoses, namely, paragonimosis, gnathostomosis,
schistosomosis, dracunculosis, fasciolopsiosis and diphyllobothriosis have
been reported in India with increasing trend.
 Human infection with Entamoeba histolytica , Giardia intestinalis and
cryptosporidiosis has been reported (and many other animals are potential
reservoirs of infection).

12. Food borne zoonoses
• Brucellosis, listeriosis, and infections due to drug-resistant
Staphylococcus aureus, Salmonella Typhi, S. Paratyphi, and Shigella
species are other important emerging foodborne zoonoses.
Climate change may cause increased risk of food contamination
changes in prevalence of pathogens in animal
reservoirs and changes in host–parasite ecology
increased environmental survival of pathogens

13. Ocean temperatures, sea level and acidity
• Rising sea temperatures,melting of polar ice caps and glaciers, increase in
sea levels is also of concern.
• Rising sea levels will lead to coastal flooding and risks for water-borne
zoonoses.
Pathogen adaptation
• Zoonotic pathogens may acquire novel virulence traits that offer survival
advantages.
• Chikungunya is an example of pathogen adaptation with the A336V
mutation that is only found in strains from A. albopictus mosquitoes
contributing to the recent outbreaks

14. Animal migration
 With alteration in seasons, changes in migration patterns and duration may
be seen.
Migration of wild birds is involved in WNF transmission
 Wild aquatic birds are the natural reservoir for highly pathogenic avian
influenza (HPAI) and these migratory birds have been shown to excrete and
act as long distance vectors for HPAI .

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