What Asia Can Do to Protect against Animal-Borne Diseases

Zoonoses (zoonosis, singular) account for 60% of infectious diseases affecting humans. These diseases are caused by a range of pathogens, such as viruses, bacteria, fungi, and parasites. Of the 1,415 pathogens known to infect humans, 61% are zoonotic.

They are spread through direct contact or though food, water, and the environment. Direct transmission from wild and farmed animals to humans is through media, such as air, or through bites and saliva. Infection can also occur via an intermediate species, referred to as a vector or carrier. Eating food contaminated with pathogenic bacteria, viruses, or parasites is the most potent zoonotic infection. The most significant foodborne pathogens are Escherichia coli O157:H7, Campylobacter, Caliciviridae, Nipah virus and Salmonella. Eggs, seafood, meat, dairy, and some vegetables are common foods linked to zoonotic contaminations.

Outbreaks of zoonotic diseases, such as Ebola virus, severe acute respiratory syndrome (SARS), avian influenza, and swine flu Influenza H1N1, have recently galvanized the attention of the global community to these public health emergencies. Most emerging zoonotic diseases often originate from the South and Southeast Asian subregions, such as SARS in the People Republic of China (PRC) in 2002, and Nipah virus in Malaysia in 1999 and Bangladesh in 2001.^[1] In the last few decades, there have been three highly pathogenic influenza virus pandemics, two of them originated in Asia. These are  Asian influenza (H2N2) in 1957, H3N2 in Hong Kong, China in 1968, and swine-origin influenza A (H1N1) virus in 2009, initially detected in humans in Mexico. 

Figure 2: Acceleration of Zoonoses

The factors exacerbating the emergence, reemergence, and spread of zoonoses are related to global trends. These include climate change, population growth, antimicrobial resistance, weak health systems, deforestation, intensive farming systems, rapid urbanization, expansion of international travels, and increased agriculture trade. These compound challenges in anticipating and detecting zoonoses, and affect the effectiveness of the response to food-borne threats to human health. In addition to these factors and weak regional health systems, disease outbreaks travel quickly, posing a serious threat to public health. For example, the H1N1 outbreak started in Mexico in 2009, it spread globally, and the World Health Organization declared its first ever "public health emergency of international concern" in 2010. The SARS outbreak in 2003 devastated the Asia and Pacific region’s tourism and aviation sectors.

Most of the zoonotic pathogens have reservoirs in wild animals. Habitat destruction, climate change and other environmental factors have contributed to increased contact between wild and farmed animals and given rise to new zoonotic diseases.

There have been substantial increases in consumption of animal products in the last few decades, mostly in Asia and the Pacific. With the increased demand, generally livestock are raised in more confined spaces with less diversity in the gene pool. These production systems are associated with the overuse and misuse of antimicrobial medicines and growth hormones in animals. These factors result in selection and spread of antimicrobial resistance, further increasing the emergence of zoonotic diseases. Traces of these excessively used antibiotics then enter the food chain, exacerbating antibiotic resistance in humans. The World Bank estimates that antimicrobial resistance would reduce the gross domestic product of the world by over 3.5% annually. By 2050, cumulative impact could be $100 trillion and 10 million deaths annually.

Zoonotic diseases are a major threat to society; they can affect entire sectors of the livestock and reduce human capital. Direct costs include lower animal production and higher public health costs. At the height of avian influenza, chicken production was reduced by over one third in the PRC. During the avian influenza outbreak in Viet Nam in 2009, 12% of the total annual poultry stock (some 50 million birds) died or were culled, heavily impacting households and the national economy.

In the last decade, the direct cost attributed to zoonoses was estimated at more than $20 billion and indirect cost at more than $200 billion.

Improved prevention and control measures far outweigh the cost of investment in human and animal health services. However, in most cases, zoonotic disease outbreaks have received a reactive response, particularly to large outbreaks, such as the avian influenza. Investments in identifying zoonotic diseases at source could prevent outbreaks or enable rapid response in an event of an outbreak and reduce impact through early detection and control. Investment in human and animal health systems to mitigate pandemic and epidemic risks in low and middle-income countries is estimated to generate high return. Globally an annual investment of $1.8 billion to $4.5 billion in preventive measures would yield $30 billion to $60 billion per year in avoided costs.

ADB has provided technical assistance at the regional and country levels, and has helped strengthen institutional capacity, including support to improve regulations, build capacity, and develop laboratories and other infrastructure to improve food safety.  Projects include enhancing sanitary and phytosanitary measures in the Greater Mekong Subregion, Mongolia, and Turkmenistan; a sustainable livestock farming and product safety demonstration project in the People’s Republic of China; and strengthening food safety standards in agricultural value chains in central and west Asia.

The Food and Agriculture Organization of the United Nations, the World Organization for Animal Health, and the World Health Organization jointly promote the One Health approach to tackle zoonoses. One Health is a collaborative, multisectoral, and transdisciplinary approach as it recognizes the interconnection of humans, animals, and the environment. Governance and coordination mechanisms of the One Health approach promotes coordination as an effective way of addressing crosscutting problems. Collaboration and coordination are adopted at global, regional and national levels to improve prevention and control of zoonotic diseases.

Zoonotic diseases are transboundary in nature. To effectively manage and control diseases, it is important to network and share information with other countries in the region. The notable regional level efforts that largely work under the One Health approach, include the One Health Network South East Asia, One Health Network South Asia, and GREASE Network. They facilitate disease identification, surveillance, and risk assessments; and develop standard methods for prevention and control of zoonoses among member countries.

Here are examples of how countries in the region are taking the One Health approach.

^[1] Nipah virus outbreak was first recognized in Malaysia in 1999, in Bangladesh in 2001, and identified periodically in eastern India. https://www.who.int/news-room/fact-sheets/detail/nipah-virus; https://www.who.int/csr/disease/nipah/en/.

ADB.2018. Strategy 2030: Achieving a Prosperous, Inclusive, Resilient, and Sustainable Asia and the Pacific. Manila.

Center for Disease Control and Prevention. Saving Lives By Taking A One Health Approach. Fact Sheet.

J.H. Epstein, et al. 2006. Nipah Virus: Impact, Origins, and Causes of Emergence. Current Infectious Disease Reports. February. 8 (1): pp. 59–65.

O.B. Jonas, et al. 2017. Drug Resistant Infections: A Threat to Our Economic Future. Washington, D.C.: World Bank Group.

W Li, et al. Animal Origins of the Severe Acute Respiratory Syndrome Coronavirus: Insight from ACE2-S-Protein Interactions. 2006. Journal of Virology . 80 (9). pp. 4211–4219. Washington, D.C.: American Society for Microbiology. 

World Bank. 2012. People, Pathogens and Our Planet: the Economics of One Health. Washington, DC: World Bank.

World Health Organization (WHO). Nipah Virus Fact Sheet.

WHO. Nipah Virus Infection.

Z. Huang, et al. 2017. HPAI Impacts on Chinese Chicken Meat Supply and Demand. World's Poultry Science Journal, 73 (3): pp. 543–558. Beekbergen: World's Poultry Science Association.