Current research generally believes that the new coronavirus may have originated in bats. How the new coronavirus spreads from bats to humans also requires direct contact between humans and intermediate host animals. However, it is not clear which animals are intermediate hosts of the new coronavirus. Recently, some scientific research teams are starting with which everyday animals are susceptible to the new coronavirus to answer these questions, which is also critical to the prevention and control of the outbreak.
On April 3, local time, a new study published by the research team of the Wuhan Virus Institute of the Agricultural Microbiology of Huazhong Agricultural University and the Wuhan Virus Institute of the Chinese Academy of Sciences on the pre-printed platform bioRxiv, “SARS-CoV-2 neutraling serum antibodies incats: a serological.” They found that serum ELISA tests of 102 cats collected after the outbreak of the new coronary outbreak in Wuhan showed that serum from 15 cats (14.7%) tested positive for the receptor binding domain (RBD) of the new coronavirus. Of the positive samples, 11 had neo-coronavirus neutralizing antibodies, with the owner having the highest neutraltine titration in three cats with new crown patients, suggesting that high school and titer may be due to close contact between the cat and the new corona.
The authors of the study are Shi Zhengli, a researcher and academician of the Chinese Academy of Engineering, Kim Merlin, and others.
This is the first study on the production of antibodies specific to neo-coronavirus in animals under natural conditions, and the data from the study show that the new coronavirus infected cats in Wuhan during the outbreak. The study has not yet been peer-reviewed.
The new coronary infection in cats may have been caused by people passing the virus on to cats, the team said in the study. But they caution that this still needs to be verified by investigating new coronavirus infections by a large sample of cats from pre-outbreak cats.
At present, there is no evidence that the new coronavirus has spread from cats to humans. However, on March 31, local time, Chen Hualan, a member of the Chinese Academy of Sciences and chief scientist of the Animal Influenza Basic series and prevention and control research and innovation team at the Harbin Institute of Veterinary Medicine of the Chinese Academy of Agricultural Sciences, and the team led by The Director of the Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences and Director of the National High-level Biosecurity Laboratory for Animal Disease Prevention and Control, published a study on bioRxiv, which found a series of new coronavirus infection tests conducted in the P4 (Biosecurity Level 4) laboratory. The new coronavirus replicates poorly in dogs, pigs, chickens and ducks, but works well in ferrets and cats. They also found that the virus can be transmitted between cats through respiratory droplets.
Therefore, Shi Zhengli also noted in the study, the study pointed to the risk of cats spreading the new coronavirus, but also need more research to understand the new coronavirus from human to cat transmission routes. But it is important that “immediate action be taken to maintain an appropriate distance between people and pet animals, such as cats and dogs, and to take strict hygiene and quarantine measures against these animals.” “They believe that strong warnings and regulations should be issued to stop this potential route of transmission.
Previous studies by Shi Zhengli et al. have shown that the new coronavirus infects humans with the same cell receptor angiotensin-converting enzyme II (ACE2) as SARS-CoV, suggesting that the new coronavirus has the same host range as SARS-CoV. Some research by a team of researchers around SARS in 2003 also showed that SARS-CoV can infect ferrets and cats, meaning they may also be sensitive to new coronaviruses.
As one of the most popular pets, cats are in close contact with people, the team said. Therefore, it is important to investigate the prevalence of new coronaviruses in cats, especially in outbreak areas. So far, however, there has been no investigation into the prevalence of the new coronavirus in cats.
Serological studies are suitable for screening antibodies against neo-coronaviruses in animals. Several methods have been used for antibody testing of new human coronaviruses. However, there is no available method for detecting cat neo-coronavirus antibodies. In this study, researchers studied the serological prevalence of new coronaviruses in cats through indirect ELISA and viruses and experiments.
The team screened a total of 143 cat serums for antibody response to the neo-coronavirus S protein recombinant receptor binding domain (RBD) through ELISA. Of the 39 serum samples collected prior to the outbreak, their OD value was 0.091-0.261 and the threshold was set to 0.32. Fifteen cat serum samples (14.7%) collected after the outbreak were positive, of which 5 were strong positive and the OD value was greater than 0.6.
The team also ruled out the effects of type I and cat infectious peritonitis virus (FIPV), which were confirmed to have no serological cross-reaction with the neo-coronavirus RBD protein.
To confirm the presence of neo-coronavirus-specific antibodies in cat serum, the team conducted a neutralizing test (VNT) on all 15 ELISA-positive serums. Of these, 11 cat serums have neo-coronavirus neutralizing antibodies, with a efficacy range from 1/20 to 1/1/1080. Four other cat serums showed no meddle, including a sample number 12, which showed strong ELISA positive and an OD value of 0.85.
Of the five ELISA strong positive samples, the intenator activity of the 10th sample was also very weak, except for the 12th sample. However, the remaining three ELISA strong positive samples 4, 14 and 15 were observed with a mediantise of 1/360 to 1/1080.
Cats Nos. 1, 5-9 are from pet hospitals, and Cats Nos. 2 and 10-13 are not originally straycats, and were taken to animal shelters after the outbreak.
It is worth noting that, consistent with high school and titration, the owners of cats 4, 14 and 15 were diagnosed with the new coronavirus infection. The team noted that the three cats whose owners were infected with the new coronavirus had the highest median titration (1/360, 1/360 and 1/1/1080, respectively), compared with 1/20 to 1/80 in pet hospital cats and stray cats, suggesting that high school and titer may be due to close contact between cats and new coronary patients.
While infections in stray cats are not yet fully understood, the team believes it is reasonable to speculate that these infections may be caused by exposure to the environment contaminated by the neo-coronavirus or to new coronary patients feeding cats.
WB analysis of cat or human serum samples. The positive control was taken for COVID-19 patient recovery serum and eLISA-negative cat serum or healthy human serum as a negative control. All tested serum samples were diluted at 1:100. C-N, cat serum negative. H-P, human recovery serum. H-N, serum for healthy people. Red Arrow, S Protein; Blue Arrow, N Protein.
The team also conducted a protein immunoprinting test (Western blot) to further verify the presence of neo-coronavirus-specific IgG in cat serum. Serums 4, 14 and 15 detected s and N proteins that purify the new coronavirus, similar to the human recovery serum. In contrast, neither ELISA-negative cat serum nor healthy human serum detected a similar condition.
The paper notes that these results suggest that the new coronavirus infects cats in Wuhan, meaning that this risk may also occur in other outbreak sites. Retrospective studies confirmed that all ELISA-positive serums were derived from cat serum samples taken since the outbreak, suggesting that the cat infection may have been caused by human transmission of the virus to the cat. The team cautions that this still needs to be verified by investigating new coronavirus infections from large samples from pre-outbreak outbreaks.
In addition, the team collected nasopharynx and swabs from each cat and used commercial kits targeting orF1ab and N genes for a new coronavirus-specific qRT-PCR. However, no double gene-positive samples were detected.
The team believes that the reasons may be: first, the viral RNA load is too low to detect; second, similar to previous studies of SARS-CoV, cats may have a short time to excrete new coronaviruses, coupled with asymptomatic after infection, and the researchers did not capture the moment of acute infection; and third, the cat’s genome sequence may have mutated, causing the cat sample to fail to amplify.
This is the first study of animals producing neutralizing antibodies specific to neo-coronaviruses under natural conditions, the team said. The study points to the risk of cats spreading the new coronavirus, and more research is needed to study how the new coronavirus can spread from human to cat.
“It is important that immediate action be taken to maintain an appropriate distance between people and pet animals, such as cats and dogs, and that strict hygiene and quarantine measures be taken against these animals.” The team finally reminded.
Journalist He Liping