The average temperature in the world has increased in the last few years compared to the previous century and is expected to continue rising if measures are not taken particularly by highly industrialised countries to reduce greenhouse gases emissions. Ironically, the countries that have contributed least to global warming – mainly the developing countries – are the most vulnerable to its impact especially from diseases that higher temperatures can bring.
Globalization and climate change have had an unprecedented worldwide impact on emerging and re-emerging animal diseases and zoonoses. Climate change is disrupting natural ecosystems by providing more suitable environments for infectious diseases allowing disease-causing bacteria, viruses, and fungi to move into new areas where they may harm wild life and domestic species, as well as humans. Diseases that were previously limited only to tropical areas are now spreading to other previously cooler areas e.g. malaria. Pathogens that were restricted by seasonal weather patterns can invade new areas and find new susceptible species as the climate warms and/or the winters get milder. There is evidence that the increasing occurrence of tropical infectious diseases in the mid latitudes is linked to global warming. Insect-borne diseases are now present in temperate areas where the vector insects were non existent in the past e.g. trypanosomosis, anaplasmosis. Humans are also at an increased risk from insect-born diseases such as malaria, dengue, and yellow fever.
Vector borne diseases are particularly affected by weather patterns and long-term climatic factors strongly influence the incidence of outbreaks. Most of these diseases are caused by insects and their population dynamics is dependent on the prevailing weather conditions, specifically temperature and humidity. Climate change influences local weather conditions and therefore has a significant impact on the presence of insects and their geographical distribution.
Warmer temperatures are already enabling insects and microorganisms to invade and reproduce in areas where once they could not due to severely low temperatures and seasonal chills. A small rise in temperatures can produce a 10-fold increase in a mosquito population causing an increase of malaria cases hence, malaria is now occurring in several Eastern European countries as well as in the highland areas of countries like Kenya where historically cooler climatic conditions had prevented the breeding of populations of disease-carrying mosquitoes. Freshwater snails, intermediate hosts for Fasciolosis, a disease that affects millions of herbivorous animals and can also affect humans can now be observed in areas above 4200 meters in the highlands of Peru and Bolivia as milder temperatures and altered environment conditions are more favourable to their survival.
Important zoonotic diseases such as avian influenza, Lyme disease and Rift Valley Fever are also likely to spread due to global warming. Avian influenza viruses occur naturally in wild birds, though often with no dire consequences, however, a highly pathogenic strain of the disease-H5N1-is currently a major concern because it can affect humans. This is mainly because severe winter conditions and droughts, occasioned by climate change can disrupt the normal migration pathways of wild birds and thereby bring both wild and domestic bird populations into greater contact at remaining water sources.
The role of tick vectors in diseases like babesiosis in animals and Lyme disease in humans, and of mosquitoes in the transmission of viruses (Rift Valley Fever, Dengue fever, African horse sickness, Bluetongue) and parasites (Malaria) are all well known but the geographical distribution of these diseases is expanding as changes in climate continue. The dreadful impact of these diseases on health and the economy affects entire animal and human populations but the poorest communities are the most disadvantaged. The increased incidence in deadly infectious diseases in wildlife, livestock, and people may be one of the most important immediate consequences of global warming.
It is now evident that diseases carried by insects and ticks are likely to be affected by environmental changes because these creatures are themselves very sensitive to vegetation type, temperature, humidity etc. However, the degree of expansion of diseases is much more difficult to predict, because disease transmission involves many other factors, and not all will be affected to the same extent by environmental change. Therefore, by using historical disease records, present-day ground-based surveillance, remotely sensed (satellite) and other data, mathematical models are being developed that will describe the past, explain the present, and predict the future of vector-borne infectious diseases.
The world needs to act effictively to ensure that the various procedures required to prevent and control emerging and re-emerging diseases are fully enabled and also to develop new techniques for their early, rapid, and accurate diagnosis. The IAEA, through the Animal Production and Health Section is at the forefront of developing and validating early and rapid diagnostic techniques that are simple to use, inexpensive and can be applied in a “laboratory limited” environment. Most of this work has been done by the application of nuclear, nuclear associated and nuclear-related technologies. Amongst these technologies are the use of 13/14C, 125I, 3H, 32P, 35S to label protein and nucleic acid molecules for specific and sensitive detection, monitoring, and characterization of harmful pathogens that have made a critical contribution towards the development of e.g. ELISA, PCR, real time PCR and sequencing. The Section also ensures the deployment and widespread use of applicable technologies in countries most at risk from climatically influenced infectious diseases. This technical support and guidance to countries (which test to use, when and for what purpose, equipment needs, staff training and proficiency, and quality management) played a vital role in building developing countries’ capacities during recent outbreaks of Avian influenza and Rift Valley Fever.
The Animal Production and Health Section has developed, implemented, and transferred immunoassays that are rapid, inexpensive and capable of being used to process large numbers of samples to detect infectious diseases that adversely affect livestock productivity and prevent international trade. The IAEA, through the FAO Joint Division of Nuclear techniques in Food and Agriculture is working together with FAO, WHO and OIE to reinforce the “One Health” approach on interactions between human and animal health.