[Smart Farmers] The common "enemy" of humans and animals: What is the "coronavirus"?

Frequent zoonotic diseases in recent years have gradually attracted people's attention, especially the outbreak of the new coronavirus at the end of 2019, which has caused heated discussions around the world. Since the 20th century, a number of coronavirus pandemics that have endangered human health have made people "terrified by the mention of the coronavirus". Is the coronavirus really that scary? Can humans and animals transmit the coronavirus to each other?

The coronavirus epidemic that has spread across the world (Photo source: Internet)

What is coronavirus?

Coronavirus is a type of widely distributed RNA virus that can cause zoonotic diseases and belongs to the Orthocoronavirinae subfamily of the Coronaviridae family of the Nidovirales order. It was first discovered in 1937. Because the virus has spike-like protrusions composed of glycoproteins on its surface, it is named coronavirus because of its crown-like shape.

SARS-CoV structure diagram (Source: Swiss Instute of Bioinformatics)

The International Committee on Taxonomy of Viruses divides them into four groups: α, β, γ, and δ. Among them, α and β coronaviruses are mainly spread in mammals such as cattle, pigs, and horses, and can also cause human diseases, while γ and δ coronaviruses mainly infect poultry and pigs.

As a positive-strand RNA virus, coronavirus can not only serve as a translation template to directly guide protein synthesis, but also as a replication template to synthesize negative-strand RNA. In other words, a series of subgenomic mRNAs produced during viral replication may serve as template chains, leading to a high replication rate and high mutation rate of coronavirus, which is conducive to the virus causing virulence or host mutation.

What are the dangers of coronavirus?

In the early days, the academic community generally believed that coronaviruses were not very harmful to humans. It was not until the outbreak of atypical pneumonia in 2002 that the harm of coronaviruses became truly apparent. Different coronavirus infections have different harmful effects on humans. For example, the current novel coronavirus is known to cause damage to the respiratory, digestive, and nervous systems.

1. Respiratory system damage: It usually appears one week after the patient is infected, and the main manifestations are dyspnea, hypoxemia, etc.

2. Digestive system damage: Digestive system damage includes decreased appetite, nausea and vomiting, abdominal pain, etc. Patients with more serious conditions may also experience symptoms such as gastrointestinal bleeding and diarrhea.

3. Nervous system damage: including abnormal epileptic discharges or slow wave activity. Some patients with new coronary pneumonia also have symptoms such as impaired consciousness and changes in mental status.

Can pets and livestock get infected with the coronavirus?

Coronaviruses have a wide range of hosts and are carried by a variety of livestock and poultry and wild animals, including mammals, reptiles, aquatic animals, etc. At present, common coronaviruses in livestock and poultry include infectious bronchitis virus (IBV), epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV) and porcine deltacoronavirus (PDCoV). These coronaviruses are relatively common in livestock and poultry breeding clinics, and outbreaks of the disease often cause large-scale deaths, especially in young livestock.

Classification table of common animal coronaviruses

Although many species can carry coronaviruses, not all animals can directly transmit the virus to humans. Among animals, bats carry the most types of coronaviruses and pose the greatest threat to humans. However, wild bats have less contact with humans, so the spread of the virus can be prevented and controlled.

Studies have found that coronaviruses also exist in wild animal populations such as bamboo rats, pheasants and civets, but the prevalence is low and they are not genetically related to human coronaviruses. For coronaviruses, we only need to do a good job of prevention and control, and don't imagine it to be too scary. This virus is preventable and controllable.

Coronavirus evolution pattern diagram (Source: Internet)

How to protect against coronavirus?

As opportunities for contact between animals and humans increase, the risk of pathogens carried by animals also increases. Viruses are introduced into new environments and spread across species through contact with livestock and humans.

For individuals, the most important preventive measure is to reduce contact with wild animals and not eat wild animals. In addition to the possibility of transmitting viruses to humans, wild animals also carry a large number of pathogens and parasites.

Feeding wild birds, taking photos with marmots and other close contact with wild animals should be avoided. If contact is necessary, personal protective measures must be taken, such as wearing a mask, gloves, and changing into water shoes. After contact with livestock and poultry, personal hygiene must be paid attention to, personal cleaning is done well, and medical alcohol is used for disinfection when necessary.

Farmers need to establish a sound livestock and poultry breeding system and strictly abide by the biosafety law at all times. Sick animals should be isolated or harmlessly treated, and cages, utensils, etc. should be thoroughly disinfected. Prevention should be the priority to improve the level of biosafety. According to the epidemic situation in the farm and the surrounding area, the age, purpose and season of the animals, appropriate vaccines should be selected, and reasonable immunization procedures should be formulated to prevent animals from getting sick.

It is necessary for management departments to strengthen epidemiological detection of coronavirus. In addition, strict law enforcement should be implemented to crack down on illegal activities such as trafficking, purchasing, and eating wild animals, and to prohibit deforestation and excessive reclamation. Because when wildlife trade, animal breeding, or forests are cleared for mining, farming, or roads, the risk of pathogens spilling over and spreading to humans will increase.

Author: Chen Xiaofan (Master’s student at South China Agricultural University)

Scientific review: Wang Xiaohu (Researcher at the Institute of Animal Health, Guangdong Academy of Agricultural Sciences)