As the world battles with the COVID-19 virus, researchers believe that the transmission of this virus could have been through a vertebrate animal. As per WHO definition, a zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Animals thus play an essential role in maintaining zoonotic infections in nature.
Zoonosis may be bacterial, viral, or parasitic, or may involve unconventional agents. As well as 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.
Based on an article published by Centre for Disease Control and Prevention (CDC), people and animal live in close contact and there are few common ways people can get infected with germs that can cause zoonotic disease
- Direct contact: Coming into contact with the saliva, blood, urine, mucous, faeces, or other body fluids of an infected animal. Examples include petting or touching animals, and bites or scratches.
- Indirect contact: Coming into contact with areas where animals live and roam, or objects or surfaces that have been contaminated with germs. Examples include aquarium tank water, pet habitats, chicken coops, barns, plants, and soil, as well as pet food and water dishes.
- Vector-borne: Being bitten by a tick, or an insect like a mosquito or a flea.
- Foodborne: Each year, 1 in 6 Americans get sick from eating contaminated food. Eating or drinking something unsafe, such as unpasteurized (raw) milk, undercooked meat or eggs, or raw fruits and vegetables that are contaminated with faeces from an infected animal. Contaminated food can cause illness in people and animals, including pets.
- Waterborne: Drinking or coming in contact with water that has been contaminated with faeces from an infected animal.
According to UNEP Frontiers 2016 Report on emerging issues of environmental concerns, environmental health initiatives have not been well represented in global zoonosis control programs.
The following primary drivers of disease emergence associated with the past emerging zoonotic disease events, based on above report, reinforce the fact that zoonosis is one of the most alarming environmental crisis of modern era:
- Rabbies transmitted by vampire bats to cattle and human was linked to forest activities in South America;
- Bat-associated viruses emerged due to loss of bat habitat from deforestation and agricultural expansion. In fact all SARS-CoV-2 isolated from humans to date are closely related genetically to coronaviruses isolated from bat populations, specifically, bats from the genus Rhinolophus. SARS-CoV, the cause of the SARS outbreak in 2003, is also closely related to coronaviruses isolated from bats. This suggests that they all have their ecological origin in bat populations. Bats in the Rhinolophus genus are found across Asia, Africa, the Middle East, and Europe.
- SARS was associated with contact with civet either in the wild or in live animal markets;
- Avian Influenza was linked to intensive poultry farming;
- Ebola outbreak in West Africa was a result of forest losses, leading to closer contacts between wildlife and human settlements;
- Japanese encephalitis virus (JEV) was linked to irrigated rice production and pig farming in Southeast Asia;
- Nipah virus was linked to intensification of pig farming and fruit production in Malaysia; and
- Lyme disease in human was triggered by Forest fragmentation in North America.
However, based on this above-mentioned report ecosystem integrity can help regulate diseases by supporting a diversity of species so that it is more difficult for one pathogen to spread rapidly or dominate.
As the human population grows, ecosystems change. Forests are exploited for logging, landscapes are clear-cut for agriculture and mining interests, and the traditional buffer zones – once separating humans from animals or from the pathogens that they harbour – are notably reduced or lost.
Because of historic underinvestment in the health sector of developing nations, and rapid development often at the cost of natural capital, disease emergence is likely to continue
The report highlights how the ecosystem integrity is compromised and eventually contributing in emergence of zoonosis.
International Environment Laws to prevent zoonosis
There are bunch of International Environmental Conventions, Treaties and Protocols adopted and entered into force with an intention to prevent such compromise of ecological integrity of this planet.
The potentially most important global conventions related to ecosystem service are the United Nations Framework Convention on Climate Change (UNFCCC); the International Plant Protection Convention; the Convention on Biological Diversity (CBD); the Convention on the Conservation of Migratory Species of Wild Animals and the United Nations Convention to Combat Desertification.
Besides these five conventions there are four more multilateral agreements which have relevance in preventing zoonosis.
Although, UNEP Frontiers 2016 Report on emerging issues of environmental concerns made a point that environmental health issues are not adequately addressed in global forum, but all the above conventions and treaties to some extent tried to cover issues related to health and environment, particularly zoonosis.
Climate change is a major factor for disease emergence. It influences the environmental conditions that can enable or disable the survival, reproduction, abundance, and distribution of pathogens, vectors, and hosts, as well as the means of disease transmission and the outbreak frequency.
Growing evidence suggest that outbreaks or epidemic diseases may become more frequent as climate continues to change.
The views and opinions expressed in the article are those of the authors and do not necessarily reflect the official policy or position of The Tilak Chronicle and TTC Media Pvt Ltd.