Q: What are zoonoses?

A: Zoonotic infections or zoonoses are infections naturally transmissible between vertebrate animals and humans. Apart from being a public health problem, many of the major zoonotic diseases prevent the efficient production of food of animal origin and create obstacles to international trade in animal products. Animals (thus) play an essential role in maintaining zoonotic infections in nature.

Zoonoses may be bacterial, viral, or parasitic, or may involve unconventional agents such as prion diseases (Bovine spongiform encephalopathy).

Q: How do people get zoonotic diseases?

A: There are different ways in which people get infected with zoonotic diseases. Some of the common ways are:

  • Directly between an animal and a person, like in rabies, with the virus in its saliva where an infected animal bites a person and infects the human.
  • Water borne and food borne such as salmonellosis, giardiasis, cryptosporidiosis, and toxoplasmosis; eating infected meat or drinking infected milk (anthrax and tuberculosis)
  • Handling infected or dead animals (anthrax), aborted foetuses and afterbirths (brucellosis)
  • Vector-borne – requiring that a vector, often an insect, passes the infectious agent between animals and people. This is the case, for example with Japanese encephalitis, where a mosquito transmits the virus to people from birds and pigs through a mosquito bi

Q: Can zoonotic diseases be treated?

A: Many zoonoses such as worm infestation are less severe in presentation and can be treated. Others can be treated, but you can get very sick and even die from others (rabies, anthrax, Japanese encephalitis) if timely prevention and/or treatment is not taken. And then there are zoonoses which have no definitive cure, treatment is mainly supportive and outcome could vary from complete recovery to death (dengue and dengue hemorrhagic fever).

Q: Why are zoonotic illnesses so common ?

A: Zoonoses have been around ever since humans came in contact with animals. Domestication of animals led to creation of opportune conditions for zoonotic pathogens to cross the species barrier. In recent times, developmental activities such as urbanization and expansion of human habitats through encroachment of wild areas have resulted in intensification of the human-animal interface. And finally, human behaviors such as hunting for 'bush meat' in rural settings and preference for keeping wild animals as 'exotic' pets also bring humans closer to animals and their pathogens. Increased and easy movement of populations has also made the spread of these infections much faster (rapid spread of SARS, H1N1 through air travel). Thus, zoonoses and opportunity for their spread to humans exist in variety of ecosystems - urban, rural, occupational, wild area, domestic and pet settings. It is not surprising that nearly 800 of the 1400 known human pathogens are of zoonotic origin and over 75% of the newly emerged infections in last three decades are zoonoses.

Many zoonotic diseases are very common and some are a serious problem all over the world. The good news is that many of these diseases can be prevented and treated. As more people learn about zoonotic diseases and how to control them, they may become less of a problem.

Q: What can I do to prevent zoonotic infections?

A: Zoonotic illnesses can infect humans by entering the body in a variety of ways: animal bites, insect bites, by ingestion, by inhalation, through cuts/scratches and through the eyes or contact with other mucous membranes. A combination of precautions would generally be necessary to prevent zoonotic infections:

  • Always practice good hand washing after working with animals, in animal housing areas, or when working with animal products.
  • Cook meat and eggs thoroughly and wash vegetables carefully in clean water.
  • Keep drinking water clean and protected from animals and animal feces.
  • Fight the bite- use insect bite protection techniques for both people and pets/livestock where ever possible
  • Control rats, mice and insect pests around your home.
  • Wash any animal bite site immediately with clean water and see your doctor as soon as possible.
  • Keep your pets and livestock healthy, consult with your veterinarian as needed.
  • Minimise contact with animal blood, feces (poop), respiratory secretions, fluids draining from wounds and injuries. When possible take protective measures to prevent transmission of disease causing agents
  • Do not handle wildlife unless absolutely necessary

Q: Why is global surveillance of zoonoses necessary?

A: Zoonoses occur throughout the world, transcending natural boundaries. Their important effect on global economy and health is well known, extending from the international movement of animals and importation of all animal products and restrictions on other international trade practices. For effective control of zoonoses, global surveillance is therefore necessary.

Q: Who are the people most at risk of contracting one or another form of Zoonoses?

A: Anybody can get infected with zoonotic infections. Certain population groups however, are at higher risk of contracting zoonoses; their greater vulnerability determined either due to their occupation that involves close contact with zoonotic pathogens, their behavioural patterns/ practices, proximity to ecosystems that increase the opportunity for zoonoses to spread to humans or as a result of their biological vulnerability. Accordingly, some of the these groups which are at risk include poultry workers, backyard livestock farmers, those living in urban slums, pet owners, rural children and those who may be immunocompromised. What makes the situation precarious, is that most of these people are unaware of their own vulnerabilities.

Q: What are the ‘12 Manhattan Principles’ in the context of One Health?

A: As many as 12 recommendations were made for establishing a more holistic approach to preventing epidemic/ epizootic disease and for maintaining ecosystem integrity for the benefit of humans, their domesticated animals and the foundational biodiversity that supports us all. These were presented to world leaders, civil society, global health community and institutions of science urging them to base their work on these principles:

1. Recognise the essential link between human, domestic animal and wildlife health and the threat disease poses to people, their food supplies and economies and the biodiversity essential to maintaining healthy environments and functioning ecosystems.

2. Recognise that decisions regarding land and water use have real implications for health. Alterations in resilience of ecosystems and shifts in patterns of disease emergence and spread manifest themselves when we fail to recognise this relationship.

3. Include wildlife health science as an essential component of global disease prevention, surveillance, monitoring, control and mitigation.

4. Recognise that human health programmes can greatly contribute to conservation efforts.

5. Devise adaptive, holistic and forward-looking approaches to prevention, surveillance, monitoring, control and mitigation of emerging and resurging diseases that take the complex interconnections among species into full account.

6. Seek opportunities to fully integrate biodiversity conservation perspectives and human needs (including those related to domestic animal health) when developing solutions to infectious disease threats.

7. Reduce demand for and better regulate international live wildlife and bushmeat trade not only to protect wildlife populations but to lessen risks of disease movement, cross-species transmission and the development of novel pathogen-host relationships. The costs of this worldwide trade in terms of impacts on public health, agriculture and conservation are enormous and the global community must address this trade as the real threat it is to global socioeconomic security.

8. Restrict mass culling of free-ranging wildlife species for disease control to situations where there is a multidisciplinary, international scientific consensus that a wildlife population poses an urgent, significant threat to human health, food security or wildlife health more broadly.

9. Increase investment in global human and animal health infrastructure commensurate with the serious nature of emerging and resurging disease threats to people, domestic animals and wildlife. Enhanced capacity for global human and animal health surveillance and for clear, timely information-sharing (that takes language barriers into account) can only help improve coordination of responses among governmental and nongovernmental agencies, public and animal health institutions, vaccine/ pharmaceutical manufacturers, and other stakeholders.

10. Form collaborative relationships among governments, local people and private and public (non-profit) sectors to meet challenges of global health and biodiversity conservation.

11. Provide adequate resources and support for global wildlife health surveillance networks that exchange disease information with the public health and agricultural animal health communities as part of early warning systems for emergence and resurgence of disease threats.

12. Invest in educating and raising awareness among the world’s people and in influencing the policy process to increase recognition that we must better understand the relationships between health and ecosystem integrity to succeed in improving prospects for a healthier planet.

Additional Information on Zoonoses

  • Zoonotic Diseases: Over 75% of recently emerging infectious diseases affecting humans are diseases of animal origin; approximately 60% of all human pathogens are zoonotic.
  • Foodborne Illness: Each year, foodborne pathogens cause an estimated 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States alone.
  • Vectorborne Diseases: There have been 1.5 million West Nile virus infections since 1999. 2.5 billion people are at risk for dengue in more than 100 endemic countries with 50 million cases of dengue fever each year.
  • Healthy Water: One billion people in the world lack access to safe water for drinking, personal hygiene, and domestic use.
  • Economic losses due to zoonoses: In addition to human suffering, over the last decade zoonotic disease outbreaks have resulted in direct losses of USD 20 billion (public and animal health services costs, compensation for lost animals, production and revenue losses to livestock sector) and indirect losses of USD 200 billion

Useful Links

Center for Disease Control (CDC) (www.dpd.cdc.gov)
National Center for Foreign Animal & Zoonotic Disease Defense (http:/fazd.tamu.edu/)
World Health Organization (WHO) (www.who.int/en/)
World Organization for Animal Health (OIE) (www.oie.int/eng/en)