By Dr P J Sharma
The ‘World Zoonoses Day’ is observed annually on the 6th of July since 1885. The day is celebrated in order to remember the first step being taken of vaccination towards eradicating the zoonotic disease for the first time. It marks the scientific achievement of French biologist Louis Pasteur, who successfully invented and administered the first vaccination against a zoonotic disease (rabies) to a man named Joseph Meister who was bitten by a dog with rabies on July 6th 1885. The concept of the term Zoonoses remains in the word zoon and nosos which denotes animal and ailments respectively. So, Zoonoses are infectious diseases (viral, bacterial, parasitic, mycotic, or unconventional) that can spread from animals or bug to humans, and vice versa, either with direct contact with animals or indirectly, vector-borne or food-borne. People may develop zoonotic diseases from contact with infected live poultry, rodents, reptiles, amphibians, insects, and other domestic and wild animals. Researchers have found that bats carry the highest number of unknown pathogens that can infect humans. Zoonoses not just originate from wild animals like bats or monkeys, it can also come from pets and farm animals.
Zoonotic diseases spread by food and water that are already infected by germs and bite of mosquito or tick is the common way of the spread of these diseases. According to studies, 75% of zoonotic infections in people are transmitted indirectly, such as through food (like milk, meat, eggs, raw fruits, and vegetables that have been obtained from infected animals or their contact).
Zoonotic pathogens can spread to humans through any contact point with domestic, agricultural or wild animals. Markets selling the meat or by-products of wild animals are particularly high risk due to the large number of new or undocumented pathogens known to exist in some wild animal populations. People living adjacent to wilderness areas or in semi-urban areas with higher numbers of wild animals are at risk of disease from animals such as rats, foxes or raccoons. Urbanization and the destruction of natural habitats increase the risk of zoonotic diseases by increasing contact between humans and wild animals. The use of antibiotics in farm animals raised for food increases the potential for drug-resistant strains of zoonotic pathogens. That’s why animals have an important role in zoonotic infections.
“Preventing the Next Pandemic: Zoonotic diseases and how to break the chain of transmission” reported that around 80 per cent of pathogens infecting animals are “multi-host,” meaning that they move among different animal hosts, including occasionally humans.
According to reports, 60 percent of human infections have an animal or insect as their primary source. Another study by the C.D.C. states that at least 70% of developing infectious diseases have animal origins, and 60% of all infectious diseases that are currently prevalent are zoonotic.
Between 1980 and 2013, there were over 12,000 recorded disease outbreaks affecting more than 44 million people worldwide, including zoonotic viruses such as SARS, MERS, H1N1 (avian) and H5N1 (swine) influenza viruses.
There are approximately 150 reported zoonotic diseases that currently exist. Animal and bird flu, bovine tuberculosis, Rabies, Ebola, plague, Nipah virus (NiV) disease and other zoonotic illnesses have had a major impact on people. Zoonotic illnesses can be exceedingly threatening to human lives since they spread quickly and, if left untreated, can infect a huge number of humans. Zoonotic diseases continue to be a threat to global health, causing millions of deaths and economic losses every year. Every year, nearly 60 000 people die from rabies, and other zoonotic diseases such as avian flu, salmonellosis, West Nile Virus, Ebola or Rift Valley fever constitute additional threats. Some diseases like HIV, begin as a zoonosis but later mutate into human-only strains. These diseases not only affect human health and welfare, but also animal health and welfare, causing lowered productivity (milk, egg, meat quality and safety, etc.), or death, and consequently affecting farmers’ livelihoods and countries’ economies.
There is evidence of Nipah virus disease among several species of domestic animals like dogs, cats, goats, sheep and horses. The case fatality ratio ranges from 40 to 100%. In India, the first Nipah virus disease outbreak was reported in Siliguri town in 2001, followed by a second outbreak in Nadia district in 2007, both in West Bengal state. In 2018, an outbreak was reported in Kozhikode district, and in 2019, another outbreak in Kochi district, both in Kerala state. Bats from the genus Pteropus . were the probable source of the 2018 outbreak in Kerala state.
Nipah virus disease can be prevented by avoiding exposure to bats and sick animals in endemic areas, and avoiding consumption of fruits partially eaten by bats, and avoiding drinking raw date palm sap/toddy/juice. The risk of infection and international transmission via fruit or fruit products, such as raw date palm sap/toddy/juice contaminated with urine or saliva from infected fruit bats can be prevented by washing them thoroughly and peeling them before consumption. Diseases not recognize any borders. For example, if pig farms have fruit trees which can attract the bats (Pteropus fruit bats are natural host of the virus) from the tropical forest, can expose our domestic pigs to infected bat’s urine and feces and get NiV infection. While there are no licensed vaccines or treatments available, experimental monoclonal antibodies have been developed to treat Nipah virus disease under compassionate use. Research into development of vaccines has been ongoing in Australia and France.
Rabies is included in WHO’s new 2021-2030 road map (of neglected tropical diseases) and targeting its elimination. This plan gives birth to the National Rabies Control Programme of India with rabies now also declared a Notifiable Disease. India set the scene on World Rabies Day by launching its new National Action Plan for dog Mediated Rabies Elimination (NAPRE) by 2030. India is endemic for rabies and suffers approximately 36% of the world’s human rabies deaths transmitted by dogs. In pre-Covid -19 pandemic times, these dogs would most likely have been intercepted by the mass dog vaccination (MDV) programs that Bhutanese and Indian veterinary officers routinely run along the border. Rabies is present on all continents, except Antarctica, with over 95% of human deaths occurring in the Asia and Africa regions. In the Americas, bats are now the major source of human rabies deaths as dog-mediated transmission has mostly been broken in this region. Bat rabies is also an emerging public health threat in Australia and Western Europe.
Under the United Against Rabies Forum’ (UAR) collaboration, WHO is working with the Food and Agriculture Organization of the United Nations (FAO), the International Organisation for Animal Health (OIE) and the Global Alliance for Rabies Control (GARC) to support countries to achieve “Zero human rabies deaths by 2030”. In 2019, GAVI included human rabies vaccines in its vaccine investment strategy 2021-2025 which will support scaling up rabies PEP in Gavi eligible countries.
WHO is also working with partners to forecast the global need for human and dog vaccines and rabies immunoglobulin, to understand the global manufacturing capacity and to explore bulk purchasing options for countries in need.
Mexico was the first country to have been validated by WHO in 2019 for eliminating human deaths from dog-mediated rabies In 2300 B.C., Rabies was first recorded and the Mosaic Esmuna Code of Babylon showed the first written account of rabies causing death in humans and dogs.
The theme of World Zoonoses Day 2022 is – “Let’s Break the Chain of Zoonotic Transmission”. It is explained during discussion of NiV above.
By the following ways we can observe world zoonoses day like: Let us vaccinate our pets against Rabies, get ourselves vaccinated against Rabies, support a pet shelter etc, etc
As part of the One Health approach, the World Health Organization (WHO) collaborates with the Food and Agriculture Organization of the United Nations (FAO) and the World Organisation for Animal Health (OIE) on the Global Early Warning System for Major Animal Diseases (GLEWS). This joint system builds on the added value of combining and coordinating alert mechanisms of the three agencies to assist in early warning, prevention and control of animal disease threats, including zoonoses, through data sharing and risk assessment.
One Health approach presented in the TZG( Tripartite Zoonoses Guide) to address zoonotic diseases helps countries to make the best use of limited resources and reduces indirect societal losses, such as impacts on livelihoods of small producers, poor nutrition, and restriction of trade and tourism.
