July 16, 2017

India, Emerging Infectious Disease and the One Health Framework

http://www.onehealthinitiative.com/map.php



The concept of ‘One Health’ promotes the realization that the health of humans, animals and the environment are linked to each other.

Animals can be sentinels of environmental hazards for humans; for example, regularly monitoring the levels of dangerous contaminants (eg lead) in pets can alert to the potential for poisoning of children. Animals develop many of the same diseases we do and can thus be good model systems. For example, dogs live for about 20 years making possible long-term longitudinal studies to assess cancer risk as exemplified by the Golden Retriever Lifetime Study. The discovery that ticks transmit cattle fever germinated the idea of mosquito bites transmitting yellow fever and malaria. Antimicrobial resistance in humans is directly traced to the use of antibiotics in livestock and poultry.

Animals are an affordable and sustainable source of protein for humans. But food security often comes at the risk of deforestation, which can promote the spread of emerging viruses to humans. Ebola and SARS viruses are directly transmitted to humans through eating infected wild animals. Nipah virus was traced to pigs that were reared on deforested land and got infected from fruit bats emerging from the lost forest. Researchers are also exploring the role of pigs as intermediate hosts in the transmission of Ebola virus.

In a landmark report in 20081, Kate Jones and colleagues (Zoological Society of London, UK) analyzed emerging infectious disease (EID) events between 1940 and 2004, with some startling conclusions. The EID events had a non-random geographic distribution, were dominated by zoonoses (i.e. transmission from animals to humans) of which over 70% originated in wildlife, and their origins correlated with socio-economic, ecological and environmental factors.

Of almost 1500 pathogens known to infect humans, over 60% are of animal origin. But these ‘known’ knowns appear to be a small fraction of the total diversity. A 2013 study estimated 320,000 viruses to infect mammals; if extrapolated to other species, there are an estimated 100 million viruses on our planet2. There is thus a vast pool of ‘unknown’ knowns.

What infectious agents are lurking in animals that can jump into humans and cause disease? Are we at a greater risk of zoonoses from apes, which share our genes, or rodents, which share our habitats? With the devastating track record of zoonotic pathogens such as HIV, pandemic influenza, Ebola and others, it would be sensible to address this comprehensively.

Two recent studies3,4 report on viruses spilling over from animals into humans and what drives such zoonotic risk.

Olival and colleagues (EcoHealth Alliance, USA) writing recently in the journal Nature3, analyzed associations between 754 mammals and 586 viruses to understand what determines viral richness, diversity and zoonotic potential. Bats, primates and rodents were found to carry the highest numbers of zoonotic viruses. Bats are also a major reservoir for coronaviruses, which made big news in 2002 when SARS emerged in China, spreading to 27 countries and killing 774 people. In 2012, the newly emerged MERS coronavirus caused 640 deaths.

Anthony and colleagues4 (Columbia University, USA) studied coronavirus diversity in 12,333 bats, 3,387 rodents and 3, 470 monkeys from 20 countries in Central Africa, Latin America and Asia, which were previously identified by Jones as ‘hotspots’ for zoonoses. Nearly 10% of bats carried coronaviruses compared to only 0.2% of the other species, with diversity being highest in locations that harbored multiple bat species, such as the Amazon rainforest.

India also has an an incredibly diverse bat population with 117 species and 100 sub-species5. But we know nothing about the viral diversity that it harbors and its potential for causing human or animal disease.

The Jones study should have alerted researchers and health policy people in India. We and our immediate neighborhood are ‘hotspots’ for zoonotic, drug-resistant and vector-borne pathogens. But there is little information from India, a key country that is also missing from the Anthony study. Poor domestic research and international collaborations in this area, the latter driven by restrictive government policies on sharing clinical and research materials, are responsible for it.

Professor Ian Lipkin at Columbia University is a world expert in the search for novel pathogens and a key contributor to the Anthony study. He has also tried to work with India for many years. “Sample access is challenging”, says Prof. Lipkin. He adds - “I'm eager to help (provided) the logistics can be sorted. Let's focus on technology transfer in emerging infectious diseases. Global public health and the people of India deserve our best efforts”. 

Why is India an EID ‘hotspot’?

The transmission of infectious disease requires contact, and its probability increases with population density. With a population of 1.34 billion people6, 512 million livestock and 729 million poultry7, and a land area of 3.287 million sq km8, India has a high density of about 400 people, 156 livestock and 222 poultry per sq km. High rates of human-animal, animal-animal and human-human contacts increase the potential of emergence, circulation and sustenance of new pathogens.

The International Livestock Research Institute in Nairobi, Kenya, showed 13 zoonoses to cause 2.4 billion cases of human disease and 2.2 million deaths per year. The highest zoonotic disease burden, with widespread illness and death, is on Ethiopia, Nigeria, Tanzania and India9.

India has also lost about 14,000 sq km of forests over the past three decades, bringing down its forest cover to 24% of land area10, against the recommended one-third. This increasingly brings wildlife into contact with humans and domesticated animals, adding to the direct risk of zoonoses from wildlife. Forest loss also alters weather patterns, indirectly and unpredictably affecting zoonoses.  

India presents a poor picture of One Health research, preparedness and policy.

There are 460 medical colleges and 46 veterinary colleges in India, but most do little or no research. Limited research on priority zoonoses such as influenza, tuberculosis, encephalitis and others, happens primarily in the health sector, with the veterinary sector paying little attention to human disease.

The governance structure and inter-sectorial coordination is also problematic. The work on human health is guided by the Ministry of Health and Family Welfare, that on animal health and husbandry by the Ministry of Agriculture, and on the environment by the Ministry of Environment and Forests. Each works in a silo.

India’s National Health Policy11 approved recently is also a missed opportunity. Framed to address the changing national healthcare needs, it does not even mention the terms “zoonoses” and “emerging infectious diseases”. It fails to break down the sectorial silos or provide an enabling environment to build core capacity in key EID areas.

What must India do?

India has shown that various sectors can successfully come together in a crisis situation such as during the 2006 Bird Flu outbreak. The need is to move from being reactive to proactively understand zoonotic pathogens before they emerge as disease in humans. This will require preparedness and policy inputs.

An Inter-Ministerial Task Force involving the key sectors of science and technology, human and animal health and the environment could be entrusted with preparing a policy framework that enables preparedness by strengthening research and health systems. Life scientists, physicians, veterinarians and ecologists could be awarded collaborative research grants to comprehensively survey animal species for pathogens with potential for causing disease in humans.

The technology for pathogen discovery is not complicated and is also available in the interest of global health. The challenge is to come together.

Such research also makes economic and political sense.

Discovering the entire viral diversity on Earth is estimated to cost $6.4 billion2. In comparison, the World Bank estimates the 2002 SARS outbreak to have cost the global economy $54 billion, and a severe flu pandemic could cost about $3 trillion or 5% of the world economy12.

A new disease emerging in any part of the world is a global threat. If India aspires to be a future leader, it must take this responsibility seriously. After all, if we can pledge to not proliferate nuclear weapons, how can we remain a potential threat for disease proliferation?
  
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