Pandemic Potential of Infectious Agents of Animal Origin and Their Biological Threats
Archana¹*, Sourabh Swami², Rakhi³, Himani Singh⁴ and Priyeranjan⁴
- PhD scholar, Department of Veterinary Public Health & Epidemiology, Bihar Veterinary College, BASU, Patna-14
- PhD scholar, Department of Veterinary Public Health & Epidemiology, College of Veterinary and animal sciences, GBPUAT Pantnagar
- PhD scholar, Department of Veterinary and Animal Husbandary Extension Education, Bihar Veterinary College, BASU, Patna-14
- V.Sc scholar, Department of Veterinary Public Health & Epidemiology, Bihar Veterinary College, BASU, Patna-14
*Corresponding author
Email id: archi2lalio@gmail.com
Abstract:
Since the last two years, the whole world has been facing the Covid-19 pandemic. The Covid-19 pandemic wasn’t the first to devasted the world and won’t be the last. In a new series, we round up emerging infectious threats that have the potential to flare up into global pandemics. Climate change, change in food habits, deforestation and globalization are some important factors which facilitate the rapid emergence and spread of zoonotic agents and evolve as a pandemic threat.
Introduction:
We interact with animals in our daily lives at our home and away from home. Animals provide us many useful things such as milk, meat, fiber, livelihoods, sport, and companionship. we use animals for beneficial purposes in various ways. But sometimes animals carry harmful germs that can spread to people and cause illness that is known as zoonotic diseases which are transmissible from vertebrate animals to humans and vice-versa. More than 60% of known infectious diseases of people are zoonotic in nature. During recent decades, the public health risk represented by the onset of outbreaks and epidemics of previously unknown human infectious diseases. Majority of those diseases emerged from animal reservoirs such as Ebola virus, West Nile virus, Nipah virus, Hantavirus, Creutzfeldt-Jakob disease, severe acute respiratory syndrome (SARS), highly pathogenic avian influenza (HPAI) viruses and more recently coronavirus have shown that biological agents and animal breeding activities can pose a significant public health risk. Several animal infectious diseases are endemic such as leptospirosis, brucellosis and rabies. Therefore, these agents can potentially cause epidemics at any time. In this light, we can say that the risk of zoonoses, particularly in occupational settings, has been probably underestimated in past years. This has been highlighted by epidemics that originated from the animal breeding sector, and, in some cases, from specific and identified animal breeding and feeding modalities.
Next pandemic:
Following diseases have the capability to cause pandemic in near future.
1.Nipah virus – Nipah virus can be the next pandemic threat as it kills as many as three in four people it infects. Fruit bats carry the virus that lives in trees in close proximity to markets, places of worship, schools and tourist spots and come into contact with humans. Bat guano is used as fertilizer in fields too, meaning that farmers and agricultural workers are potentially in frequent contact with the virus. In the ‘Nipah belt’ on the Bangladesh-India border, outbreaks happen regularly, and recent research indicates that bats across Bangladesh harbour the virus, suggesting undetected outbreaks could be occurring. As 60% of the world’s population lives in the region where Nipah originated and deforestation and environmental change continue to bring humans, livestock and wildlife closer, the risk of spill-over events grows. The disease is also so deadly that many governments classify it as a bioterrorism threat and limit the laboratories that are allowed to culture and study it.
2.Crimean-Congo Haemorrhagic Fever – Crimean-congo haemorrhagic fever (CCHF) is a widespread disease caused by a tick-borne virus (Nairovirus) of the Bunyaviridae family. The CCHF virus is transmitted to people either by tick bites or through contact with infected animal blood or tissues during and immediately after slaughter. Majority of cases have occurred in people involved in the livestock industry, such as agricultural workers, slaughterhouse workers and veterinarians. Factors such as climate change and the movement of livestock or wild animals may further increase its geographic spread, with the virus recently expanding its reach from the Balkan region to Central and Western Europe. Nairovirus is a biosafety level 4 pathogen which causes frequently fatal infections in humans and there is no effective treatment for it. The increasingly widespread geographical dispersion of these parasites is a major cause for concern.
3.Hantavirus –Spread from rodents to humans, old and new world Hantavirus has become endemic in many continents, but there are sporadic cases of person-to-person transmission strong enough evidence that it can be next pandemic potential. Orthohantaviruses are a viral genus which are able to cause disease in humans. These are transmitted through inhalation of aerosols from infected rodent excretions and cause a range of haemorrhagic and pneumonic symptoms. Particular species such as Hantaan orthohantavirus and Dobrava-Belgrade orthohantavirus have most likely been circulating in regions of the world for centuries, while Sin Nombre virus and Andes virus species were isolated in the 1990s. This distinction between old and new world viruses is significant regarding morbidity and mortality as well as their potential to become pandemic.
4.Ebola – Ebola has so far only affected African countries and occasional cases outside of the continent have been rapidly reported. But the virus could mutate to spread more easily between people, making it more of a pandemic threat. If the virus mutates in ways that allow it to spread via respiratory droplets, as COVID-19 does, that would increase the potential for it to spread more easily and become a pandemic threat. Reston strain of Ebola virus so far only affects animals, but it is so similar to the other four Ebola viruses, there is a concern that it could mutate to become pathogenic in humans and then spread easily around the world through imported livestock or other animal production. Ebola’s natural hosts are fruit bats of the Pteropodidaefamily. But the virus can spread to people through porcupines and other non-human primates too. It spreads between people through direct contact with blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials, such as bedding or clothing, contaminated with these fluids.
5.Chikungunya – Chikungunya is spread by the Aedes aegypti and Aedes albopictus mosquitoes, the same mosquitoes that transmit dengue and Zika virus. Today the deadly combination of climate change and globalization makes chikungunya (and other mosquito-borne disease) a pandemic threat, as mosquitoes find new habitats and increased travel can mean that people bring new diseases into their country. When mosquito breeding sites are located close to where people live, the risk of infection goes up significantly. In parts of Africa, other mosquito species have also been implicated in chikungunya transmission. In addition, small animals may act as ‘reservoirs’ of disease where the virus lurks and which are able to trigger further outbreaks later on.
6.H5N1 and H7N9 influenza – The highly pathogenic H5N1 avian subtype has developed the ability to be transmitted from poultry to humans. It was previously said that people could only be infected with H1, H2 and H3 variations but the spill-over demonstrates the high risk imposed by random mutations in the hemagglutinin and neuraminidase glycoproteins, from which the subtypes get their H and N classifications. So far, there are no reports of human-to-human transmission of H5N1, but this is not true of avian influenza subtype H7N9, which emerged in 2013 and has limited suspected cases in which people were infected by family members. Both have high mortality rates and little is understood about these mutations, making them unpredictable, they have a high pandemic potential and must be considered high risk. Influenza is spread through respiratory droplets when an infected host sneezes or coughs. Because birds, pigs and other zoonotic hosts are reservoirs for the virus and have the potential to transmit the virus to humans, the threat posed by influenza virus is ever-present.
7.Yellow fever – The yellow fever is caused by flavivirus closely related to those that cause dengue, Zika virus disease, Japanese encephalitis and West Nile fever, but significantly more deadly. This virus is endemic in tropical parts of Africa and Central and South America. However, because of climate change Aedes aegyptiis expanding its territory, and is projected to occupy central parts of the USA and China as well as some southern European countriesby 2050. The yellow fever virus is primarily spread by the Aedes aegypti mosquito. Its “life” cycling between mosquitoes and wild monkeys, and humans living nearby can also become infected. If they travel to more densely populated urban areas, subsequent mosquito bites can transmit the disease to other individuals.
8.Lassa fever – Lassa fever is an acute viral haemorrhagic illness caused by the Lassa virus belonging to the Arenaviridaevirus family. The disease was first discovered in 1969, but it was most likely endemic in West Africa before that. Lassa fever is endemic across Benin, Ghana, Guinea, Liberia, Mali, Nigeria and Sierra Leone, and potentially other West African countries, but there have been cases seen in the USA and Europe imported from West Africa. There is Pandemic threat from this disease due to long incubation time and the fact that four in five people become infected with Lassa virus have no symptoms means the disease can spread easily through international travel. Lassa virus is carried by Mastomysrats that lives inside or near human habitation. The rats themselves don’t become ill, but shed the virus in their urine and faeces. People become infected when they come into contact with infected rat droppings, and this is why people most at risk are those living in rural areas, in crowded and unsanitary conditions. Lassa fever is difficult to distinguish from other viral haemorrhagic fevers such as Ebola virus disease or yellow fever, as well as other diseases that cause a fever, including malaria or typhoid fever. There are no vaccines to protect against infection.
9.Marburg – A deadly cousin of Ebola, Marburg can kill nine out of ten people it infects, and international travel has taken it from Africa to Europe twice in the past 40 years. Due to increasing globalization this virus is more likely to erupt around the world. Marburg virus can spread from human to human through contact of bodily fluids, much like Ebola. As previous outbreaks in Europe and the US have shown, that increasing globalization and international travel increases the risk for global spread, especially when the incubation period could be up to three weeks. Marburg virus is spread through direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and also through any materials such as bedding, that have been contaminated with the infected fluids. Burial ceremonies in which people have direct contact with the body can also drive the spread of the virus.
10.Next Coronavirus – It is a disease of pandemic threat as hundreds of coronaviruses are circulating in animal species such as bats, pigs and pangolins, which have the potential to jump to humans, mutate and become more transmissible. The sale of live wild animalsin traditional food markets will make such events more frequently. Although the development of COVID-19 vaccines may help to end the current COVID-19 pandemic, ongoing high rates of infection in many countries could lead to the emergence of further variants capable of evading vaccine-induced immunity. Middle East Respiratory Syndrome (MERS) also has pandemic potential as MERS coronavirus is usually contracted through direct or indirect contact with infected camels or camel products, but there have been cases of human-to-human transmission. The worry is that more transmissible variants may emerge, which rapidly spread. This scenario becomes more likely as climate change increases the frequency of droughts, and prompts farmers in countries, such as Kenya, to switch cattle for camels, potentially bringing a greater number of infected animals into close contact with humans.
Conclusion:
Incidence of emerging infectious agents like, SARS, MERS, Covid-19 and Ebola is more frequent in past decades. In the future, new agents will emerge with pandemic potential. The multiple factors play a vital role in emergence of infectious agent which become pandemic in future. Education of people, maintenance of hygiene, proper cooking of food etc. are some measures to reduce the next pandemic.
