COVID-19: Human-Animal Transmission or Vice Versa?

By Dr Ezeme Udoakuchinyere Chimamanda

As Coronavirus Disease 2019 (COVID-19) caused by the SARS-CoV-2 virus (otherwise known as the COVID virus) pandemic continues to surface in different parts of the world, scientists are still in active search of the missing link between animal to human transmission. According to daily updates monitored on the website of  the World Organisation for Animal Health (OIE), there are not enough scientific proofs to authenticate the purported transmission of SARS-CoV-2 from animals to humans, even though current evidence suggests that  the virus originated from an animal origin.

According to OIE, the COVID-19 virus isolated from humans shares 96% homology with beta coronaviruses isolated from multiple species of bats in the genus Rhinolophus. SARS-CoV isolated from humans shared 92% homology with SARS-like viruses that were circulating in bats. Thus, the comparatively strong genetic sequence homology between the COVID-19 virus and beta coronavirus isolated from bats suggests that ancestors of the COVID-19 virus were circulating in bats in the Rhinolophus genus. These groups of bats are widely distributed across Asia, the Middle East, Africa and Europe.

Civets were implicated as the intermediate host in the transmission of SARS-CoV to humans and owing to the similarities between SARS-CoV and the COVID-19 virus, opinions are in the favour of an intermediate animal host which is yet to be identified as opposed to direct bat to human transmission.

Dr Peter Embarek, a Food Safety and Zoonoses expert with the World Health Organisation believed it is never too late to find the missing link, citing the example of MERS episode of 2012, “finding the missing animal-human link was far from been straightforward, even though, everybody was looking for the source. It took months of epidemiological detective work and a slice of luck before the transmission link to camels was found, after health officials in Qatar reported two suspect cases linked to a farm, which were followed to confirm the link to the dromedaries”.

Laboratory findings according to recent OIE updates shows that so far, cats, ferrets and fruit bats are susceptible to this viral infection with a potential of transmission while dogs are less susceptible. There are reports of dogs, cats and minks which have tested positive to SARS-CoV-2, following close contact with infected humans, which raises the possibility of other animals to become infected with the virus after close contact with an infected human. However researches so far suggest that poultry and pigs are not susceptible to SARS-CoV-2.

OIE, FAO and WHO are all currently involved in studies of the human-animal transmission (zoonosis) of SARS-CoV-2. OIE specifically has mobilized research groups in its member countries to make available research findings and impact of COVID-19 on animal health and its implication in veterinary public health. It has issued guidelines to veterinary laboratories to support public health services response on COVID-19 as well as to keep the OIE updated on any investigation or research outcome in animals for risk assessment, management and risk communication to reduce the risk in future events.

In Nigeria, the chairman of Nigeria Veterinary Medical Association (NVMA) Oyo state branch, Dr Ayo Adejuyigbe on May 8, 2020 while on a Radio Nigeria programme made a request to the federal government to set up laboratories for testing animal samples across the country to support the fight against COVID-19. He further advised pet owners to keep some distance from their animals, wear gloves and face mask while taking care of them and ensure change of clothes afterwards in order to avoid a cycle of infection. LIVESTONEWS.

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