ZOONOSIS THEORY

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Context

• There is now a large body of peer-reviewed scientific research consistent with the zoonotic origin of Covid-19 pandemic.

Important Articles:

https://www.iasgyan.in/daily-current-affairs/livestock-and-zoonosis

 https://www.iasgyan.in/daily-current-affairs/one-health-approach-37

Zoonosis

• A zoonosis is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that can jump from a non-human (usually a vertebrate) to a human and vice versa.

Examples

• Major modern diseases such as Ebola virus disease and salmonellosis are zoonoses.
• HIV was a zoonotic disease transmitted to humans in the early part of the 20th century, though it has now evolved into a separate human-only disease.
• Most strains of influenza that infect humans are human diseases, although many strains of bird flu and swine flu are zoonoses. These viruses occasionally recombine with human strains of the flu and can cause pandemics such as the 1918 Spanish flu or the 2009 swine flu.

Modes of Transmission

Direct Zoonosis

• Zoonoses have different modes of transmission. In direct zoonosis the disease is directly transmitted from non-humans to humans through media such as air (influenza) or through bites and saliva (rabies). 

Reverse zoonosis or Anthroponosis

• In contrast, transmission can also occur via an intermediate species (referred to as a vector), which carry the disease pathogen without getting sick. When humans infect non-humans, it is called reverse zoonosisor anthroponosis.

Causes of Zoonoses

• The emergence of zoonotic diseases originated with the domestication of animals. 
• Zoonotic transmission can occur in any context in which there is contact with or consumption of animals, animal products, or animal derivatives.
• This can occur in a companionistic (pets), economic (farming, trade, butchering, etc.), predatory (hunting, butchering or consuming wild game) or research context.

Rise in Frequency of Zoonotic Diseases

• Approximately 1.67 million undescribed viruses are thought to exist in mammals and birds, up to half of which are estimated to have the potential to spill over into humans -  Study led by researchers at the University of California.

Underlying reason

• According to a report from the United Nations Environment Programme and International Livestock Research Institute large part of the causes are environmental like climate change, unsustainable agriculture, exploitation of wildlife, land use change.

Preventing Zoonosis

https://www.thehindu.com/sci-tech/health/explained-a-boost-to-the-zoonoses-theory-regarding-the-origins-of-the-sars-cov-2-virus/article66643322.ece