COVID-19 (SARS-CoV-2 Scourge): Veterinary Perspective

Human to animal transmission of the virus requires preventive protocol especially while dealing with the pet and domestic animals at home
Representational Image
Representational ImageSource: Rebecca Scholz from Pixabay

COVID-19 evolved as a global pandemic, since its initial outbreak in Wuhan, China has rendered human populations on tenterhooks. Till now it is established that the disease originated from an animal reservoir with strong evidence referable to Bats (Horseshoe bats). Amongst various known Bat species the majority are poor hosts except a few that harbor this infection. The notorious Corona viruses are already known to infect various species of birds and mammals causing gastroenteritis and respiratory infections. Recently the virus strains have caused fatal diseases in humans especially Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS). However COVID-19 (novel Corona virus Disease-2019) is the zoonotic infection adapted in humans due to SARS-CoV-2 virus culminating in life threatening severe respiratory embarrassment with aerosol mode of transmission. More than half a million people around the world have been predated by this disease and further cases continue to pop up. Having been declared a pandemic by the WHO the virus might become part of the respiratory viruses group that infects humans regularly. It is evidenced that the majority of newly emerging or re-emerging human diseases originated in animals and the predisposition facilitated by the destruction of wildlife habitats, climatic changes and human interference into wildlife habitats. SARS-CoV-2 virus infected wide range of animal hosts and reports have been pouring in suggesting that many animals harboring and spreading the infection to human subjects. Owing to the initial mutation in animals, COVID-19 strain had an easy way spreading from person to person; the risk to animals being low but natural infections of SARS-CoV-2 have been documented in companion dogs, cats, tigers, lions, leopards, non-human primates, farmed mink and ferrets. The reason assigned to the transmission is that of animals having been exposed to an animal caretaker or sick owners (infected with COVID-19). The possibility of a rodent intermediate host has not been excluded. Since the experimental studies have suggested that ferrets, raccoon, white-tailed deer, rabbits, fruit bats, and certain hamsters are equally susceptible to SARS-CoV-2 infection along with various other non-human primates (Rhesus macaques, baboons, and marmosets) are also found susceptible to SARS-CoV-2. The first COVID-19 case in pet animal was reported in a Pomeranian dog (Hong Kong China in February 2020) and the first positive COVID-19 case in cat was reported (March 2020) in the same country only after their owners were Covid -19 positive. Many studies throughout the world suggest that the cats are highly susceptible and have greater tendency to transmit the infection to other cats. Cat-to-cat transmission can take place via contact or air and it can spread from people to animals in some situations, especially during close contact that must serve a concern to cat owners. So far transmission of SARS-CoV-2 from companion animals (cats and dogs) to humans has not been reported but there is possibility of SARS-CoV-2 to be transmitted from pet animals (dogs and cats) to humans and vice versa because they possess same cell receptor (ACE2 proteins) and thereby inter-species transmission may be possible. The initial confirmed cases of natural SARS-CoV-2 animal infections in non-domestic species in the world were reported from four tigers and three lions at the Zoo, NY, (United States) after they developed respiratory signs. SARS-CoV-2 was detected in respiratory secretions/feces from all seven animals. Nine SARS-CoV-2 genomes from the animals and keepers were identified. In this case epidemiological data confirmed the human-to-tiger transmission. SARS-CoV-2 infection in minks was first reported in the Netherlands (farmed in several countries for their fur) followed by their mortality reported from various countries (Italy, France, Canada, Greece and Spain). SARS-CoV-2 infection was confirmed from the clinical signs (pneumonia), pathological findings, rapid animal-to-animal transmission in minks (similar to the findings observed in human patients with COVID-19) and finally by the isolation of the virus. In India recently 8 Asiatic lions (Nehru Zoological Park, Hyderabad) have been confirmed positive for SARS CoV-2 virus probably transmitted from infected caretakers.Based on the current studies birds like chicken, turkeys, quail, geese, ducks and pigeons are not susceptible at all or spread the infection, presumed to be resistant to SARS-CoV-2. Moreover till now studies confirm that the virus did not replicate in chicken eggs. There is no evidence so far on the susceptibility of livestock animals like Cattle Sheep, horses and donkeys to COVID-19 infection. Laboratory animals such as hamsters, ferrets and non-human primates are used as animal models for studying the SARS CoV-2 as these provide the exact clinical and pathological resemblance to that in humans. Fortunately at present in J&K there have been no reports of the spread of this infection in animals from humans or vice versa but the transmission of this infection particularly via wildlife especially around the peripheries of the wildlife areas in the valley is not a remote possibility as there are reports of species spillover of this infection from the world nations. Obviously awareness and preventive measures are important. Human to animal transmission of the virus requires preventive protocol especially while dealing with the pet and domestic animals at home. Sick owners need to avoid direct contact with their pets. The future concern is that owing to mass human vaccination around the world, the virus might be forced to re-enter the animal species for another gene mutation in order to escape vaccinal immunity in human population and re infect them. Such reverse zoonosis or anthro-pozoonosis has been observed in several viruses. This concern will impel the need for animal/livestock vaccinations. This has perhaps made Russia to initiate vaccination of pet and zoo animals against COVID-19 for the effective eradication. This is the first such vaccine against COVID-19 in animals given in two shorts -21 days apart that provide immunity in animals for 6-months. This vaccine is named Carnivak-Cov based on a principle similar to the human vaccine. The vaccine has shown 100 per cent efficacy in trial results on dogs, cats, foxes and mink. There is a demand for vaccinating the animals against COVID-19 especially those living in close proximity with humans (pets, minks, big cats, non-human primates). Several pharmaceutical companies are already in race of manufacturing the vaccines for animals against COVID-19. Although it is presumed that animals are somewhat resistant to SARS-CoV-2 transmission compared to humans, however this disease has severely affected the animal welfare directly and indirectly. There is a serious concern ahead regarding re-infection of this SARS CoV-2 virus to humans as it has the wide host range and ability to cross the species barrier and thereby coming back to humans in a new form probably. Nevertheless on the basis of available information, the risk of animals spreading COVID-19 to people is also considered to be low and the impact of the virus has been mild on animals but we cannot deny the fact that the source of infection is animal. The fear is that this disease can spread from humans to wild life and vice versa, might get mutated and re-emerge even if pandemic is over.

DR. NUZHAT HASSAN, Asstt. Prof. Veterinary Preventive Medicine -SKUAST-K

DR. MUZAFFAR SHAHEEN, Prof. & Head. Veterinary Medicine -SKUAST-K

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