34
3.2.3 Inferences from the Case Studies
These two cases show that climate change will cause local shifts in geographical
ranges of most vector-borne diseases in both dry/hot and cool/wet areas due to at
least two distinct processes. In the hot/dry areas, scenarios of higher rainfall and
humidity would promote higher survival rates of vectors, while in the cool/wet
areas, increasing temperatures would allow overwintering of these vectors. The key
determinants of vectors’ population dynamics include temperature, humidity and
water availability, especially for mosquitoes. Although we point to potential shifts
in disease risk, we believe climate change would affect transmission patterns of
infectious diseases in multiple ways, including lowering the effectiveness of existing intervention strategies. No studies have been done to verify this issue but given
that the rate of development of most arthropods would increase with temperature
and lead to changing population dynamics, the frequency of application of some of
the vector control measures such as acaricides might need to be reviewed. High
temperatures also reduce the hosts’ immune responses (Dittmar et al. 2014) and
studies need to be done to determine whether this has implications on the effectiveness of the available vaccines which confer protection by priming the hosts’
immune system.
3.3 Mitigations and Adaptations
Projections from simulation models suggest that global warming will continue to
worsen if the current levels of greenhouse gas emissions are not reduced. It is, therefore, expected that the incidence and impacts of climate-sensitive diseases—including RVF and TBDs—will increase, particularly among the most vulnerable
populations in developing countries. These diseases, though, can be mitigated by
established control measures including quarantine, import bans, the identification
and removal of suspicious animals and premises, surveillance and reporting, vaccination, disinfection, and compensation (Grace and McDermott 2012). However, the
effectiveness of some of these measures in the face of climate change has not been
determined. Moreover, their deployment is inadequate as the animal health systems
in most of these countries have deteriorated.
Vector control and vaccination are often used to control RVF and TBDs. Vector
control is however not a reliable measure for controlling RVF in livestock (Gachohi
et al. 2017). This is because floods that trigger RVF epidemics maintain high mosquito population densities and insecticide-induced mortality rates would be much
lower compared to the rates of development and emergence of new adults.
Conversely, acaricides have been used successfully for many years to control TBDs
but recent observations indicate that tick resistance to acaricides is threatening to
limit the effectiveness of this measure. Alternative ways of managing TBDs are
therefore being developed, such as the use of tick vaccines (specifically for
B. Bett et al.
3.2.3 Inferences from the Case Studies
These two cases show that climate change will cause local shifts in geographical
ranges of most vector-borne diseases in both dry/hot and cool/wet areas due to at
least two distinct processes. In the hot/dry areas, scenarios of higher rainfall and
humidity would promote higher survival rates of vectors, while in the cool/wet
areas, increasing temperatures would allow overwintering of these vectors. The key
determinants of vectors’ population dynamics include temperature, humidity and
water availability, especially for mosquitoes. Although we point to potential shifts
in disease risk, we believe climate change would affect transmission patterns of
infectious diseases in multiple ways, including lowering the effectiveness of existing intervention strategies. No studies have been done to verify this issue but given
that the rate of development of most arthropods would increase with temperature
and lead to changing population dynamics, the frequency of application of some of
the vector control measures such as acaricides might need to be reviewed. High
temperatures also reduce the hosts’ immune responses (Dittmar et al. 2014) and
studies need to be done to determine whether this has implications on the effectiveness of the available vaccines which confer protection by priming the hosts’
immune system.
3.3 Mitigations and Adaptations
Projections from simulation models suggest that global warming will continue to
worsen if the current levels of greenhouse gas emissions are not reduced. It is, therefore, expected that the incidence and impacts of climate-sensitive diseases—including RVF and TBDs—will increase, particularly among the most vulnerable
populations in developing countries. These diseases, though, can be mitigated by
established control measures including quarantine, import bans, the identification
and removal of suspicious animals and premises, surveillance and reporting, vaccination, disinfection, and compensation (Grace and McDermott 2012). However, the
effectiveness of some of these measures in the face of climate change has not been
determined. Moreover, their deployment is inadequate as the animal health systems
in most of these countries have deteriorated.
Vector control and vaccination are often used to control RVF and TBDs. Vector
control is however not a reliable measure for controlling RVF in livestock (Gachohi
et al. 2017). This is because floods that trigger RVF epidemics maintain high mosquito population densities and insecticide-induced mortality rates would be much
lower compared to the rates of development and emergence of new adults.
Conversely, acaricides have been used successfully for many years to control TBDs
but recent observations indicate that tick resistance to acaricides is threatening to
limit the effectiveness of this measure. Alternative ways of managing TBDs are
therefore being developed, such as the use of tick vaccines (specifically for
B. Bett et al.