A very informative article by Khan Sharun and others, from Dept. of surgery, ICAR - Indian Veterinary Research Institute, Bareilly, India, shows that the deadly COVID-19 virus was first transmitted in Wuhan, China via Zoonotic [animal to human] transmission. Further tests have indicated Bats as the possible origin of the virus, however, Pangolin could be the intermediate host as well.
Detailed studies have suggested that the virus spreads to animals such as cats, lions, tigers and shows symptoms such as vomiting, diarrhea, breathing difficulties; the only exception being dogs, who contract the disease, but do not show symptoms.
This scientific review studies in detail not only animals to humans studies, but also humans to animals spreading of animals. Many infected humans have reported heavy viral infections, where chances of spilling over to animals could be a cause of concern. Due to uncertainty regarding the origin of the virus, it is very important to observe hand hygiene in animal markets.
In another study, it was noticed that cats infected with the virus did not show many symptoms, but were able to spread this virus to other pet animals via droplets and maintaining the infection chain. The COVID-19 virus appeared to originate from Bats, then spread to cattle, sheep, goats as intermediate hosts and finally humans as terminal or final hosts.
A researcher from Italy found out that pet dogs acted as intermediate hosts in the spreading of COVID-19 as the dog to human population ratio was very high, which could have resulted in animal to human spreading of virus, causing huge deaths in Italy. Also Pangolins were found to be natural reservoirs for COVID-19 virus.
By using animal models like the mice and studying their effect by injecting COVID-19, the antibodies produced in the mice can be tested, so that suitable vaccines may be prepared for future use in human beings. These animal models and their outcome can be used in the fundamental research for development of vaccines and other preventive medicines. By studying the effect of Coronavirus in these animal models, matching medicines can be identified which will help in further prevention of the disease.
Also the use of animal models to study the effect of the disease is useful to study structural body differences of these animals as compared to human beings, gives an approximate information regarding the effect of this disease inside these animals.
An interesting study by Aung Myint, retired, formerly head of bacterial vaccine production at the Livestock Breeding and Veterinary Department , Myanmar and Trevor Jones ,retired, former veterinary investigation officer Nottinghamshire, UK, where a vaccine for birds was developed by these authors from tissue of infected birds in a farm in Myanmar.
This vaccine was then used on over 9,000 birds. After vaccination, it was found out that not only the death rate in young birds was significantly reduced, but surprisingly the egg production rate also increased on the farm. This vaccine proved to be very active both when used both as a preventive and treatment of bird flu in Myanmar, and many such good reports came in also from the neighbouring farms by veterinarians and farmers alike. The farmers have even called it as "Egg increasing Vaccine ", and are very happy with the results since the last 25 years.
Therefore a multidisciplinary effort by specialists in medicine, veterinary science, virology and microbiology can identify the chain of spreading of this virus, so that a tailored action may be taken to block further spreading at the required area. Although the infection chain has been seen in domestic animals such as cats, ferrets, etc., none of them conclusively prove that infection and spreading of disease occurs from animals to humans under natural conditions. So far, there is no confirmed direct evidence of spread of COVID-19 from animals to humans.
Compiled from various international research journals available at google scholar by D. Mukherjee having 38 years of pharmaceutical (Cardiac, Diabetic, Neurology, Pain & Inflammation products) experience with a Swiss Multinational Company NOVARTIS and edited by Dr Sandeep Ahlawat, MBBS