33
and the Senegal Dam on the Senegal–Mauritania border in 1987/1988 (Martin et al.
2008). A recent study conducted in Kenya confirmed that irrigated areas in arid and
semi-arid areas support endemic transmission of RVF (Mbotha et al. 2017) but more
work is needed to isolate the virus from such cases to confirm observations made
from serological studies. Drought-resistant livestock species, including goats, which
are thought to play a critical role in the epidemiology of RVF and other zoonotic
diseases, are increasingly being raised in arid and semi-arid areas as one of the
adaptation measures for climate change and variability. These changes are likely to
increase the risk of infectious diseases that would compromise health and livelihoods of a large population of pastoralists.
3.2.2 Ticks and Tick-Borne Diseases (TBDs)
Ticks are important vectors of a wide range of pathogens that cause many diseases
in livestock such as anaplasmosis, babesiosis, cowdriosis, coxiellosis (Q fever),
Crimean–Congo haemorrhagic fever, ehrlichiosis and theileriosis. East Coast fever
(ECF)—the disease with the greatest economic importance in dairy animals—is
caused by Theileria parva and transmitted by Rhipicephalus appendiculatus. The
disease causes high mortality, especially in highly productive, susceptible breeds
where mortality can reach 100%. Other losses associated with the disease include
poor weight gain, fertility losses, reduced growth and productivity, paralysis and
increased susceptibility to other diseases. Its geographical range stretches from
South Sudan to South Africa and up to Democratic Republic of the Congo (DRC)
(Olwoch et al. 2008).
There are few studies in East and southern Africa that have looked at the effects
of climate change on ticks and TBDs. Olwoch et al. (2008) applied a simple climate
envelope model to investigate the effects of climate change on the distribution of R.
appendiculatus and ECF in sub-Saharan Africa, based on climate anomalies for
2020s versus 1990s. They predicted a reduction in the range of the tick in the western arid regions in Angola, southern DRC and Namibia, given that these areas were
already hot and dry and further increases in temperature would make them unsuitable under the future climate scenarios used. On the contrary, the study established
that some areas in Botswana, eastern DRC, the Northern and Eastern Cape provinces of South Africa, and Zambia would become more suitable in the 2020s,
because of increased rainfall and a rise in the minimum temperatures.
From a global perspective, a rise in temperature has the potential to expand the
geographical range of about 50% of tick species, with 70% of these involving economically important tick species (Cumming and van Vuuren 2006). This mainly
represents the northern expansion of the northern limits of ticks as has been observed
in Sweden and Russia among other places.
3 Climate Change and Infectious Livestock Diseases…
and the Senegal Dam on the Senegal–Mauritania border in 1987/1988 (Martin et al.
2008). A recent study conducted in Kenya confirmed that irrigated areas in arid and
semi-arid areas support endemic transmission of RVF (Mbotha et al. 2017) but more
work is needed to isolate the virus from such cases to confirm observations made
from serological studies. Drought-resistant livestock species, including goats, which
are thought to play a critical role in the epidemiology of RVF and other zoonotic
diseases, are increasingly being raised in arid and semi-arid areas as one of the
adaptation measures for climate change and variability. These changes are likely to
increase the risk of infectious diseases that would compromise health and livelihoods of a large population of pastoralists.
3.2.2 Ticks and Tick-Borne Diseases (TBDs)
Ticks are important vectors of a wide range of pathogens that cause many diseases
in livestock such as anaplasmosis, babesiosis, cowdriosis, coxiellosis (Q fever),
Crimean–Congo haemorrhagic fever, ehrlichiosis and theileriosis. East Coast fever
(ECF)—the disease with the greatest economic importance in dairy animals—is
caused by Theileria parva and transmitted by Rhipicephalus appendiculatus. The
disease causes high mortality, especially in highly productive, susceptible breeds
where mortality can reach 100%. Other losses associated with the disease include
poor weight gain, fertility losses, reduced growth and productivity, paralysis and
increased susceptibility to other diseases. Its geographical range stretches from
South Sudan to South Africa and up to Democratic Republic of the Congo (DRC)
(Olwoch et al. 2008).
There are few studies in East and southern Africa that have looked at the effects
of climate change on ticks and TBDs. Olwoch et al. (2008) applied a simple climate
envelope model to investigate the effects of climate change on the distribution of R.
appendiculatus and ECF in sub-Saharan Africa, based on climate anomalies for
2020s versus 1990s. They predicted a reduction in the range of the tick in the western arid regions in Angola, southern DRC and Namibia, given that these areas were
already hot and dry and further increases in temperature would make them unsuitable under the future climate scenarios used. On the contrary, the study established
that some areas in Botswana, eastern DRC, the Northern and Eastern Cape provinces of South Africa, and Zambia would become more suitable in the 2020s,
because of increased rainfall and a rise in the minimum temperatures.
From a global perspective, a rise in temperature has the potential to expand the
geographical range of about 50% of tick species, with 70% of these involving economically important tick species (Cumming and van Vuuren 2006). This mainly
represents the northern expansion of the northern limits of ticks as has been observed
in Sweden and Russia among other places.
3 Climate Change and Infectious Livestock Diseases…