Swimmer Baylis 18010

Effects of climate change on animal health in Africa: 

Effects of climate change on animal health in Africa Matthew Baylis Veterinary Clinical Science University of Liverpool SWIMMER workshop, Jan 18, 2007

Sources: 

Sources FORESIGHT Infectious Diseases: preparing for the future. Office of Science and Innovation, 2006. www.foresight.gov.uk/ Reports: Africa State of Science Review: Climate change & infectious diseases of animals Modelling studies

Climate and disease: 

Climate and disease “We must understand how climate affects infectious diseases today before we can predict climate change’s impacts of the future” (Future Threats, Appendix A) Climate may affect: Spatial distribution of outbreaks Timing of disease outbreaks Intensity or severity of outbreaks

Examples of climate-disease links (1): 

Examples of climate-disease links (1) Anthrax worldwide zoonosis spores remain infective for 10-20 years in pasture. temperature, RH and soil moisture affect spore germination heavy rainfall stirs up dormant spores. outbreaks often associated with alternating heavy rainfall and drought, and high temperatures Spotted hyena eating a zebra dead from anthrax, Ethosha Park, Namibia

Examples of climate-disease links (2): 

Examples of climate-disease links (2) Peste des petits ruminants acute, contagious, viral disease of small ruminants transmitted mostly by aerosol droplets between animals in close contact. clinical PPR is often associated with the onset of the rainy season or dry cold periods PPR in goats in Nigeria; 1982-86. Redrawn from Wosu et al, 1992

Examples of climate-disease links (3): 

Examples of climate-disease links (3) Fascioliasis (liver fluke) caused by the Fasciola trematode fluke of economic importance to cattle and sheep producers in many parts of the world. associated with environmental conditions favouring the intermediate snail host. Eg. low lying wet pasture, areas subject to periodic flooding, and temporary or permanent bodies of water Liver fluke life cycle

Examples of climate-disease links (4): 

Examples of climate-disease links (4) African horse sickness lethal infectious disease of horses caused by a virus transmitted by Culicoides biting midges. Large outbreaks of AHS in the Republic of South Africa over the last 200 years are associated with the combination of drought and heavy rainfall brought by the warm-phase of the El Niño Southern Oscillation (ENSO) El Nino Southern Oscillation

Examples of climate-disease links (5): 

Examples of climate-disease links (5) Trypanosomosis Trypanosomosis, spread by tsetse flies, imposes a huge burden on African people and livestock. Many aspects of the vectors’ life cycles are sensitive to climate, and spatial distributions can be predicted using satellite-derived proxies for climate variables Source: David Rogers, Oxford

Examples of climate-disease links (6): 

Examples of climate-disease links (6) Bluetongue The components of Vectorial Capacity are strongly linked to temperature. When raised at high but sub-lethal temperatures, innate resistance to viral infection is overcome. Disperal is associated with movements on winds Proportion of females positive for BTV 10 Rearing temperature /ºC

How climate change will affect diseases: 

How climate change will affect diseases Via direct effects on: Pathogens Hosts Vectors Dynamics/epidemiology And via indirect effects on populations, communities, landscape structures etc

Climate change and pathogens: 

Climate change and pathogens To get from one host to another, many pathogens spend time in the environment, exposed to the weather. Climate affects pathogen development time and survival Longer ‘seasons’ may increase the number of cycles Milder winters may increase/decrease between-season pathogen survival Climate change may affect disease seasonality Climate change may affect dispersal FMD virus Anthrax bacillus

Climate change and hosts: 

Climate change and hosts Ndama cattle Rinderpest in Africa Immunity to disease (in rodents/humans) can be linked to weather and UV exposure. Many hosts have partial ‘genetic’ resistance to the pathogens to which they have been exposed for aeons. Rapid spread of pathogens may expose naïve populations to new diseases. Newly-exposed populations may also suffer from lack of ‘endemic stablility’ to certain diseases.

Climate change and vectors (1): 

Climate change and vectors (1) Climate change will affect vector distributions, population sizes and seasonality Higher temperatures will affect vector competence, and vectorial capacity Climate change may affect vector dispersal Change in the frequency of extreme events (eg ENSO) may favour some vector-borne disease (RVF, AHS) Cattle being vaccinated against RVF in northeast Kenya, 2007

Climate change and vectors (2): 

Climate change and vectors (2)

Climate and epidemiological dynamics: 

Climate and epidemiological dynamics Climate can affect Transmission rates Contact networks Dispersal/migration rates or routes Landscapes Community structures……. In the 1990s. drought forced East African pastoralists to move their livestock to new areas for grazing, thereby exposing wildlife to rinderpest.

Evidence for climate change’s effects on infectious disease: bluetongue: 

Evidence for climate change’s effects on infectious disease: bluetongue Culicoides biting midge European temperature change: 1980s v 1990s “The spread of bluetongue and its vectors presents some of the strongest evidence to date that climate change is driving vector-borne diseases into new regions, as warming and disease spread have occurred at the same times in the same places” (Future Threats, Appendix A)

Bluetongue in 2006: 

Bluetongue in 2006 BTV serotype 8 – never before seen in Europe. Unknown origin. Belgium, Germany, Holland and France; >1250 foci. A ‘new’ vector – Culicoides dewulfi The summer of 2006 was exceptionally warm A member of the obsoletus group