COVID-19 spreading between people, animals

Several recently-published studies indicate that SARS-CoV-2 likely has jumped between people and animals.

In one study, which was presented recently at the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and included data from 16 mink farms in the Netherlands, investigators noted that the virus likely jumped between people and mink and back, providing strong evidence that animal-to-human transmission is possible.

In December of 2019, the initial source of the SARS-CoV-2 outbreak was thought to have started with the spread of the disease from a live animal market in Wuhan, China.

Considering the new diseases' similarities with SARS-CoV-1, a zoonotic origin seemed not only plausible but likely.

Experiments since then have revealed that many nonhuman primates, as well as other animals like ferrets, rabbits, and dogs, were capable of contracting SARS-CoV-2, but the spread from animals to humans was not certain. However, with further evidence being revealed, this seems to be evermore probable.

The outbreak of SARS-CoV-2 on the mink farms was first identified on April 23 and April 25. Once these were diagnosed, it was decided that an in-depth investigation was needed, which would help to establish the potential environmental and occupational hazards.

The investigation employed epidemiological information, surveillance data, and contract tracing, which the Dutch national response system for zoonotic diseases made available, to assist in whole-genome sequencing (WGS). WGS is useful in monitoring the emergence and spread of pathogens in a population.

The investigators tested both owners and employees of the mink farms. In total, 97 individuals were tested, using 1 of 2 options, these being serological assays or RT-PCR. Of those tested, 66 out of 97 showed evidence of SARS-CoV-2 infection. This was shown by either respiratory tract samples (of which 49% tested positive) or serum samples (of which 51% tested positive) containing SARS-CoV-2 specific antibodies.

Using WGS, the investigators sequenced 18 total samples from those testing positive from 7 different farms. In a majority of the cases, the sequences from the human samples were nearly identical to those of the mink sequences from the same farm. This is clear evidence that the animals were most likely the cause of human infection.

Additional evidence collected that confirms this theory was that there appeared to be no significant spillover to people who lived within the same 4-digit postal code as the mink farms.

These and other related findings prompted government officials there to cull millions of minks to control spread there.

Meanwhile, Kansas State University researchers have discovered 2 important findings published in recent studies that relate to the COVID-19 pandemic. The studies found that cats can be asymptomatic carriers of the SARS-CoV-2 virus, while pigs are most likely not significant carriers.

The studies, published in Emerging Microbes & Infections, took place at Kansas States Biosecurity Research Institute.

This article originally appeared on our sister publication, Contagionlive's website.

Reference
Gaudrealt NA, Trujillo JD, Carossino M, et al. SARS-CoV-2 infection, disease and transmission in domestic cats. Emerg Microb Infect. Accessed November 19, 2020; doi.org/10.1080/22221751.2020.1833687