|Livestock Research for Rural Development 25 (7) 2013||Guide for preparation of papers||LRRD Newsletter||
Citation of this paper
Agriculture and livestock are amongst the most climate sensitive economic sectors in the developing countries whilst the rural poor communities are more vulnerable to the adverse effects of climate change. Climate change is real and is happening now. Current knowledge on the relationship between climate change effects and animal health is lacking particularly in East Africa despite of livestock agriculture being economically important in the region. Many related studies in the region have reported on the impacts of climate change on human health compared to animal health. This deficiency has created a knowledge gap which affects livestock management authorities and several development projects.
This review paper describes the current knowledge in regards to potential impact of climate change and livestock infectious diseases in East Africa region. A number of research reports and scholarly articles on climate change, animal diseases epidemiology were reviewed over a period of two months. Livestock production and health are significantly vulnerable to the impact of climate change and resource poor farmers and pastoralists are the most vulnerable. Early warning systems, preparedness and improved public and private veterinary services should be strengthened so as to lower the adverse effect of climate change. In addition, adaptation and mitigation approaches should be practiced to minimize the effects. The knowledge obtained from this paper will help all stakeholders including decision makers and donor communities to have a better understanding of climate change effects on livestock sector so as to build resilience of vulnerable livestock keeping communities and work together in formulation of mitigation, adaptation and traditional coping strategies against these adverse effects.
Key words: adaptation, animal diseases, extreme weather, livestock agriculture, pastoralists vulnerability
Changes in climate and extreme weather events have received increased attention in the recent years. According to the 4th Intergovernmental Panel on Climate Change (IPCC) assessment report, there is already evidence that Africa is warming faster than the global average, and this is likely to continue (IPCC 2007). Climate change is real and it is taking place now. It will become worse in future with more impacts to rural poor communities of developing countries (AMCEN 2011). The same observation have been reported by WFP et al (2009) who noted that rural communities in developing countries especially women, children and marginal communities are at greatest risk to suffer from potential impacts of climate change due to high exposure to natural hazards, their direct dependence on climate sensitive resources such as plants, animals, water and land, and their limited capacity to adapt to and cope with climate change.
Changing temperature and weather pattern have great influence on increasing magnitude of climate change impacts. As reported by IPCC (2007), the average global surface temperature has risen by 0.8°C in the past century and by 0.6°C in the past three decades (Hansen et al 2006) mainly because of human activities. It is projected that if the greenhouse gas emission will continue to rise, by the end of 21st century the mean global temperatures will increase 1.4 – 5.8°C.
The East Africa region is characterized by wide diverse climates from desert to forest over comparatively small areas. Rainfall seasonality is complex, changing within tens of kilometers. The rainfall cycle for the year is bimodal with long rains from March to May and short rains occurring from October to December (WWF 2006). In the past, the region has been prone to floods and drought which have had severe negative impacts on key sectors of economies of most countries of East Africa. These include agricultural production, health status, water availability, energy use and biodiversity and ecosystem services (including tourism). In the late seventies and eighties drought caused widespread famine and economic hardships. Reports from risk assessment studies indicate that that future climate change may lead to a change in the frequency or severity of such extreme weather events, potentially worsening these impacts, together with annual and seasonal rainfall changes. In addition, the extreme weather events such as drought and floods will have a potential negative consequence on livestock-agriculture sector (Nicholson and Entekhabi 1986; Ward 1998). Any outcome of the impact will have a strong distributional pattern and amplify inequalities in health status and access to resources, due to apparent spatial variations in vulnerability. Furthermore, vulnerability is exacerbated by existing developmental challenges and low adaptive capacity of rural communities (DFID 2009).
The effects of climate change on livestock production and health could be an additional significant burden to the already existing problems that hold back livestock development in Africa (Van den Bossche 2008). In addition, lack of economic development and institutional capacity makes the situation more challenging. Climate change impacts have the potential to weaken progress made in improving the socio-economic well-being of East Africans (WWF 2006). Significantly, the climate variability will have a serious effect on pastoralists whose livelihood depends upon livestock for food, economic security and cultural preservation. The impact of climate change also increases the problem of water scarcity; pasture land shortage and diseases dynamics. Diseases in livestock result in severe effects on livestock survival, marketability, animal health and livelihoods (Gardner 2012).
This paper explores the potential impacts of climate change on livestock production and health in the region and proposes several appropriate approaches that can be adopted to mitigate or adapt the prevailing situation. It is anticipated that this paper will generate valuable information that will be useful to various stakeholders in livestock sector in the region towards improved and sustainable livestock production.
Livestock production contributes significantly to the economy of East African countries and has been recognized to be among the most significant sources of revenues in the region. However, the large proportion of livestock including cattle is owned by small scale poor farmers who are facing several challenges including variation of climate patterns. Being in the pool of poverty, climate change has direct impacts on small scale livestock keepers and affects their resilience to livelihood including food security. Without understanding current and future climate variability these challenge will be persistent and growing. It is predicted that, by 2020, Africa will have close to a quarter of its population experiencing water stress, low agricultural yields, and natural disasters like droughts and famines, as well as increased negative health impacts. Despite of socio-economic in the region, there is little information so far documented on that can give a good picture of current knowledge on potential impacts of climate change and livestock production and health in the region. The knowledge presented in this paper will therefore address this gap by generating information that will be useful to various stakeholders, from the ground up to international level. It will enhance or promote a new thinking on the best way the livestock sector in the region can be managed in a changing climate towards improved and sustainable livestock production.
This extensive literature review covers research reports and scholarly articles on climate change, infectious livestock diseases and other important information related to this topic. More than 40 papers were reviewed over a period of two months, and drafts prepared were passed to a number of reviewers for their concrete comments to refine this article.
In the past three decades warming was at the rate of 0.050C per year. East Africa has experienced a more variable precipitation; but, historical records indicate that there has been an increase in rainfall over the last century (Hulme et al 2001; IPCC 2001). The rainfall experienced across Eastern Africa has been highly variable ranging from about 100 mm/year in northeastern Ethiopia to about 2500 mm/yr in parts of northern Tanzania, with an average annual precipitation of 920 mm/year (WWF 2006). According to Hulme et al 2001 parts of equatorial East Africa are likely to experience 5-20% increased rainfall from December to February and 5-10% decreased rainfall from June to August by 2050 (Figure 2). Despite this, there is general consensus that East Africa will become wetter (Van den Bossche 2008). Table 1 shows the overview of past and future trends in temperature and rainfall in East Africa and Figure 1 shows Drought and El Nino Oscillation in East Africa.
Table 1: Overview of past and future trends in temperature and rainfall in East Africa
• At the national level, between 1960 and2003, mean annual temperatures increased by 10 C per decade.
•Daily temperature observation show increasing trends in the frequency of hot days and a much larger increase in the frequency of hot nights.
projections indicate that
In terms of rainfall,
no statistically significant trends were observed.
•Mean rainfall is projected to increase by up to 48% by the 2090s, and within this, the proportion of rainfall that falls within heavy events is projected to increase by 13% over the same duration.
•No data available.
temperatures will increase 3-5°C and mean annual temperatures will
rise by 2-4°C.
•No data available.
•Areas with bimodal rainfall areas an increase in rainfall of 5-45% and areas with uni-modal rainfall decrease of 5-15%.
•Since 1960, mean
annual temperature has increased by 1.3°C, with an increase in the
hot days frequency.
•Increases in the hot days and nights, and continued decreases in the number of cold days and nights.
• A decrease in
annual rainfall of about 3.4mm per month (3.5% per decade).
• An increase in annual rainfall, particularly in the short-rain season with an increasing proportion of rain falling during heavy rainfall events.
Source: Global water initiative, East Africa Programme
|Figure 1: Drought and El Nino Oscillation. Rainfall in East Africa Related to ENSO, currently severe La Nina Phase.
Figures 2 and 3 show observed and simulated variations in past and projected future annual average precipitation and temperature over land territories of three East African countries Tanzania, Kenya and Uganda. Black lines show estimates from observational measurements from GISTEMP (Hansen et al 2010), HadCRUT3 (Brohan et al 2006), HadCRUT220.127.116.11 (Morice et al 2012) and MLOST (Smith et al 2008) for temperature, and CMAP (Xie and Arkin 1997), CRU TS 3.10 (Harris et al., 2012), GPCP v2.2 (Adler et al 2003), and PRECL (Chen et al. 2002) for precipitation. Shading denotes the 5-95 percentile range of climate model simulations from the CMIP5 archive (Taylor et al 2012), driven with "historical" changes in anthropogenic and natural drivers (68 simulations), historical changes in "natural" drivers only (30), the "RCP4.5" emissions scenario (68), and the "RCP8.5" (68). Data are anomalies from the 1986-2006 average of the individual observational data (for the observational time series) or of the corresponding historical all-forcing simulations.
|Figure 2: Observed and simulated variations in past and projected future annual average precipitation.
Source: Hansen et al 2010 and others
|Figure 3: Observed and simulated variations past and projected future annual average temperature.
Source: Hansen et al 2010 and others
Livestock production systems existing in the region may be divided into two main groups; these are commercial and small scale farmers (Mc Dermont et al 1999). Small scale is predominantly practiced in the region and is carried out by small family units independently (Perry et al 2007). The small scale production can be categorized into groups depending on the integration of livestock and crops or on the level of commercialization. Small scale farmers may be defined into two groups. Subsistence farmers are the ones found in remote poor areas and depend fully on their production; they have limited capital for investments, and increase in production depends largely on climatic factors and other factors such as additional labour, animal manure and livestock management practices. Semi subsistence farmers are found near the main road and urban markets; they mainly depend on farming but the surplus is often sold.
Mixed farming is practiced when livestock and crop productions are integrated in the same farm. Pastoralism is based almost entirely on livestock production, with little or no integration with crops. These systems are found mainly in arid or semi-arid zones and are characterized by high animal mobility. Considering the types of livestock production systems in East Africa and its dependence on environmental conditions this makes the sector very vulnerable to climate change. The situation is worsened by other factors such as low skills and knowledge of farmers/producers, low input/output production methods, ineffective private and public animal health and laboratory services, these factors leave the sector incapable to deal with the challenges caused by climate change impact (Van den Bossche 2008).
The direct effect of climate change as a result of increased ambient temperature and concurrent changes in heat exchanges causes heat stress which influences growth, reproduction performance, milk production, wool production, animal health and welfare (Walter et al 2010; Reilly 1996). Heat stress suffered by animals will reduce feed intake and result in poor growth performance, although indigenous cattle are heat tolerant to high temperatures (Walter et al 2010). Extremely high temperature caused by extreme weather events experienced at this era may still affect B. indicus resulting in reduced milk and meat production and reduced time for foraging as they prefer to remain in the shade (Robertshaw and Finch 1976). Additionally, heat related mortality and morbidity would increase. Climate change is also expected to increase the risks of drought and floods that occur with El Niņo in the future and this could result in serious high mortality of livestock due to drought resulting in pasture shortage and water scarcity which will aggravate the existing conflicts on natural resources and food insecurity in the region. Similarly El Niņo may result in diseases outbreaks related to flooding (Van den Bossche 2008).
These are changes that influence quantity and quality of pastures, fodder crops and grains, water availability, severity and distribution of diseases and parasites (Baylis and Mathew 2010). Pastures shortage and water scarcity in drought areas resulting from extreme weather conditions and major anthropogenic factors have been reported (IPCC 2001).
Changes in the frequency and distribution of diseases due to climate variability have been reported; however, estimating the real impact of climate change on livestock health over a long period still is a challenge (Van den Bossche 2008). It seems difficult to separate non-climatic factors from climatic factors. The best way in estimating a future impact of climate change based on empirically observed relationship between climatic conditions and their effects on the biological processes that determine diseases transmission in space and time (Rogers 1996; Rogers and Randolph 2006).
The impact of climate change on the transmission and geographical distribution of animal diseases shows that this has been associated with changes in the replication rate, dissemination of pathogens, vector and animal host populations, which are sensitive to changing temperature and rainfall (Baylis and Mathew 2010).
Increased temperature may have effect on some pathogens and parasites in that it causes, increased development on their life cycle outside their hosts. This may reduce their generation time and hence have more generations per year resulting into higher number of pathogens/parasites which predicts more infections. However, there are some pathogens/parasites that are sensitive to higher temperature and will affect their survival (Baylis and Mathew 2010; Harvell et al 2002). Another effect to consider is moist and dry conditions. Pathogens and parasites that are sensitive to moist or dry conditions may be affected by changes to precipitation, soil moisture and the frequency of floods. Changes to winds could affect the spread of certain pathogens as well (Baylis and Mathew 2010).
Temperature and moisture frequently impose limits on vectors distribution. Often, low temperatures limit vector distribution because of high winter mortality and a relatively slow rate of population recovery during warmer seasons. This is different with high temperatures as, limiting occurs when there is excessive moisture loss. Therefore, cooler and high altitude regions which were previously too cold for certain vectors may begin to allow them to flourish with climate change. Warmer regions could become even warmer and yet remain permissive for vectors if there is also increased precipitation or humidity. Conversely, these regions may become less conducive to vectors if moisture levels remain unchanged or decrease, with concomitant increase in moisture stress. Changes to temperature and moisture will also lead to increases or decreases in the abundance of many disease vectors. For example biting midges and mosquito-borne diseases outbreaks have been linked to the occurrence of ENSO (Anyamba et al 2002; Baylis et al 1999; Gagnon et al 2001; Gagnon et al 2002; Hales et al 1999; Kovats 2000).
The ability of some insect vectors to become or remain infected with viruses varies with temperature. Together with this effect on vector competence, increase in temperature will alter the balance between lifespan and the Extrinsic Incubation Period (EIP), increasing or decreasing the proportion of infected vectors that live long enough to transmit the infection forward. This effect will be most important for short-lived vectors such as biting midges and mosquitoes (Lines 1995).
The feeding frequency of arthropod vectors may also increase with temperature increase. Many vectors must feed twice on suitable hosts before transmission is possible. For many blood-feeding arthropods, feeding frequency is determined by the time required for egg development. For example, C. sonorensis females feed every three days at 30 °C but only every ~14 days at 13 °C (Wittmann and Baylis 2000).
Another effect on vectors worthy of consideration is wind movement and there may be important effects of climate change on vector dispersal, particularly when there are changes in wind patterns. Reports show that there is an association between wind movements and the spread of epidemics of many culicoides and mosquito borne diseases (Sellers et al 1982; Sellers and Pedgley 1985; Sellers and Maarouf 1990, 1991, 1993), a possible good example being the British blue tongue outbreak in 1998 (Baylis and Mathew 2010).
According to (Aucamp 2003; de Gruijl et al 2003) mammalian cell immunity level may be suppressed following a sharp exposure of ultraviolet B (UV-B) as a result of expected ozone layer depletion. Biologically, there is depletion in specific Lymphosites cells and for that reason animals become susceptible to some pathogens such as viruses; rickettsia (such as Cowdria and Anaplasma, and some bacteria, such as Brucella (Baylis and Mathew 2010), besides prolonged exposure to ultraviolet radiation may diminish animal’s response to vaccination (de Gruijl et al 2003). Therefore, continued depletion of ozone layer would possibly impact some animal diseases in future. Although, this investigation was done in mice and humans only (Baylis and Mathew 2010). There is a need for further investigation in animal cells.
Genetic resistance of animal on diseases is worthy for consideration, for example wild mammals in Africa may be infected with trypanosomes, but rarely show signs of disease where as European breeds and/or crossed breeds introduced are highly susceptible to Trypanasomiasis. The experience was different for the case of rinderpest disease experience in late 19th century, where by the African mammals proved highly susceptible and many animals died. Although, the genetic resistance seems not to be affected by climatic change factors but still climate change pose a threat to animals due to a significant shifts in the distribution of animal diseases at present (Baylis and Mathew 2010).
Another host related effect worthy of consideration is “endemic stability” of animals. This means the infection is common and there is lifelong immunity after infection, also occurs when the disease is less severe in younger than older individuals. Tick borne diseases such as anaplasmosis, babesiosis and cowdriosis, show endemic stability (Eisler et al 2003). If climate change drives such diseases to new areas, non-immune individuals of all ages in these regions will be newly exposed, and outbreaks of severe disease could follow (Baylis and Mathew 2010).
Effect on Epidemiology
Climate change may alter transmission rates between hosts by affecting the survival of the pathogen/parasite or the intermediate vector, but also by other, indirect, forces that may be hard to predict with accuracy (Baylis and Mathew 2010). For example, a series of droughts in East Africa between 1993 and 1997 resulted in pastoral communities moving their cattle to graze in areas normally reserved for wildlife. This resulted in cattle infected with a mild lineage of rinderpest transmitting disease both to other cattle and to susceptible wildlife such as buffalo and impala, causing severe disease, and devastating certain populations (Kock et al 1999). Climate change may affect the abundance or distribution of hosts or the competitors/predators/parasites of vectors and influence patterns of disease in ways that cannot be predicted from the direct effects of climate change alone. Climate change-related disturbances of ecological relationships, driven perhaps by agricultural changes, overgrazing, deforestation, construction of dams and loss of biodiversity, could give rise to new mixtures of different species/strains, thereby exposing hosts to novel pathogens and vectors and causing the emergence of new diseases (WHO 1996).
Non vector borne diseases
The effect of climate change on the distribution and prevalence of non-vector borne diseases varies greatly (Van den Bossche 2008). Changes in the environmental condition resulted directly or indirectly by the climatic change can increase or reduce the survival of the pathogen agent in the environment or predispose the susceptible animal to the infection. These environmental changes could also increase or reduce contact between infected and susceptible animals. Pathogens which spend a period outside the host are sensitive to changes in temperature and humidity. These pathogens include the infective spores of anthrax and blackleg, the viruses causing peste des petits ruminants (PPR) and foot and mouth disease (FMD), contained in wind-borne aerosol droplets (Van den Bossche 2008). Drought, overgrazing and environmental stress expose anthrax spores similarly scarce water may get contaminated with anthrax spores. The prevalence of fasciola infections may increase in areas where rainfall increases and create water bodies for snail’s survival as intermediate host of F.hepatica (Van den Bossche 2008).
Climate variables are able to affect the prevalence, intensity and geographical distribution of helminthes. Various reports indicate that the impact of climate change on helminthes is more patent in temperate and colder areas as well as in high altitude. The influence of climate change is manifested directly to free-living larval stages and indirectly mainly on invertebrate, but also vertebrate hosts (Mas-Coma et al 2008).
Close contact diseases are less related to climate change however, climate variability and ecosystem change resulting in shortage of pasture and water cause mass movement of livestock and wildlife which bring them close together and may results in the transmission of pathogens (Morgan et al 2007) such as Bovine Contagious Pleuro Pneumonia, Foot and Mouth Disease ad PPR. A good past experience was a rinderpest outbreak in stressed cattle and wildlife population (Kock et al 1999; Thornton et al 2006).
Vector borne diseases
Many studies have reported on the effects of climate change and the frequency and distribution of human vector borne diseases (Hay et al 2002; Kovats et al 2001). In East Africa probably in the whole of Africa animal vector borne diseases fall into categories Viral-midges and biting flies.
Tsetse transmitted trypanasomiasis is one of the greatest diseases of economic importance in the region. This is a vector borne disease caused by a parasite called trypanosomes through vector know as tsetse flies. There are three major groups of vector depending on their habitats. It is predicted by 2050 a decline in all three groups habitats in their northern and southern fronts However, in East Africa there is an increase in habitats (Baylis and Mathew 2010). In addition, there is predicted to be an extended distribution of habitat suitability for the morsitans group in other places across Africa (Baylis and Mathew 2010). The vectors are sensitive to warming because temperature can alter vector development rates, shifts their geographical distribution and alter transmission dynamics (Moore et al 2011). According to Moore et al 2011, model findings predicted that increases in mean annual temperatures over the next 50–100 years are likely to significantly shift the distribution of T. b. rhodesiense to eastern and southern Africa. These shifts in distribution may lead to an increase in the risk of public health infection. African trypanosomiasis, a vector-borne disease of humans and animals, was recently identified as one of the 12 infectious diseases likely to spread owing to climate change (Moore et al 2011).
Ticks transmit many important livestock diseases in Africa such as East Coast Fever (ECF), Babesiosis, Cowdriosis and heart water and, like tsetse; ticks inflict significant constraints on productivity. A model on Tick Borne Encephalitis a European case, was applied to tropical and sub-tropical ticks, in that it took into account changes in both temperature and moisture conditions from a variety of climate models. This has suggested that some species may expand their ranges in the future and others may contract (Randolph 2008; Estrada-Peņa 2001; Rogers and Randolph 1993). Specifically, a detailed study on 30 species of Rhipicephalus ticks a primary vector of ECF in Eastern and southern Africa concluded that 54% of species may spread into new regions, while the ranges of 46% may contract (Olwoch et al 2007), the difference lying, not surprisingly, in the sensitivity of each species to ‘harsh’ conditions of high temperature and dryness. Still is there is a challenge to determine if ticks abundance is contributed by climate change or host variability
Rift Valley Fever is a viral disease transmitted by mosquitoes mainly affecting livestock but also humans. The virus survives in the Aedes mosquito eggs during the dry period. During flood season the virus is transmitted by Culex, Mansonia and Anopheles species (Seufi and Galal 2010). Rift Valley fever outbreaks are positively correlated with El Niņo events and have become frequent (Patz et al 2005). Flooding is driven by the interaction between the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole Moment (IOD) (AMNEC 2011).
In recent incidence of several vector borne diseases has significantly increased and/or changed its distribution still we cannot rule out that all these changes are due to climate change, there are other factors that need to be put into consideration when looking at the vector borne diseases epidemiology.
Many assessments on the relationship between climate change and infectious diseases have concentrated on human health particularly vector borne diseases such as malaria, yellow fever and dengue and still there are debates on the attribution of malaria resurgence in some African areas. More researches at regional and local level are still required on studying and quantifying climate change impact on infectious livestock diseases. Very little research has been conducted on the impacts of climate change on livestock health, regardless of its vital importance in the sub region unfortunately, there are little information on the relationship between long climate change and animal health. Monitoring its impact is a complex task since there are other confounding factors which may contribute to animal health problems. In addition, research is needed on the analysis of indirect effects of climate change on economic, social and demographic sectors and their impact on the livestock sector (Van den Bossche 2008).
Despite much uncertainty, some of the effects of climate change in East Africa livestock sector may be predicted with relative certainty. These could form the basis for the development of general policies on how to prevent the adverse effects. Livestock keepers could be made more aware of climate change and variability so surveillance systems should be established or improved and capacity of the production system to deal with such changes should be enhanced.
The development and establishment of coping strategies is a continuous process and need to be improved. However, this remains a big challenge and need to be well addressed to all stakeholders for their valuable contribution. Models that have been used that clarify, qualify and quantify the future effects assist in scientific uncertainties and help to focus on research work. An assessment of climate change on animal health should consider other confounding factors in modeling and such integrated models will be far much useful for decision making policy. The evidence for the relationship between climate change and animal health depends largely on the context, and varies between different livestock production systems. Therefore, these models must be based on data relevant to the livestock population so that the information generated would be applied in other areas with similar climatic conditions and livestock production systems.
Indeed a better understanding of the effect of climate change on animal health and production is crucial and good for recommendations on how to lessen its potential impact. Unfortunately, the determinants of resilience and adaptation that already reduce this impact are often poorly understood even though they are not unique but are needed regardless. For example, adaptive capacity could be increased in the broader context of developing appropriate policy measures and institutional support to help the East African livestock owners to cope with all animal health problems. In fact, the development of an effective and sustainable animal health service, with associated surveillance and emergency preparedness systems and sustainable animal disease control and Prevention programmes (e.g. vaccination campaigns against Rift Valley Fever, African Horse Sickness and bluetongue), is perhaps the most important and most needed adaptive strategy. This will safeguard livestock populations from the threats of climate change and climate variability.
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Received 13 May 2013; Accepted 28 June 2013; Published 1 July 2013
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