In late December 2019, an unusual pneumonia emerged in humans in Wuhan, China, and rapidly spread internationally, raising global public health concerns. The causative pathogen was identified as a novel coronavirus (
1–
16) and named severe acute respiratory syndrome–coronavirus 2 (SARS-CoV-2) on the basis of a phylogenetic analysis of related coronaviruses by the Coronaviridae Study Group of the International Committee on Taxonomy of Viruses (
17). Subsequently, the disease caused by this virus was designated coronavirus disease 2019 (COVID-19) by the World Health Organization (WHO). Despite major efforts to control the COVID-19 outbreak, the disease is still spreading. As of 11 March 2020, SARS-CoV-2 infections have been reported in more than 100 countries, and 118,326 human cases have been confirmed, with 4292 fatalities (
18). WHO has now officially declared COVID-19 a pandemic.
Although SARS-CoV-2 shares 96.2% of its identity at the nucleotide level with the coronavirus RaTG13—which was detected in horseshoe bats (
Rhinolophus spp.) in Yunnan province, China, in 2013 (
3)—it has not previously been detected in humans or other animals. The emerging public health crisis raises many urgent questions. Could the widely disseminated SARS-CoV-2 be transmitted to other animal species, which then become reservoirs of infection? The SARS-CoV-2 infection has a wide clinical spectrum in humans, ranging from mild infection to death, but how does the virus behave in other animals? As efforts progress toward vaccine and antiviral drug development, which animal(s) can be used to most accurately model the efficacy of such control measures in humans? To address these questions, we evaluated the susceptibility of different model laboratory animals, as well as companion and domestic animals, to SARS-CoV-2.
All experiments with infectious SARS-CoV-2 were performed in the biosafety level 4 and animal biosafety level 4 facilities in the Harbin Veterinary Research Institute (HVRI) of the Chinese Academy of Agricultural Sciences (CAAS), which was approved for such use by the Ministry of Agriculture and Rural Affairs of China. Details of the biosafety and biosecurity measures are provided in the supplementary materials (
19). The protocols for animal study and animal welfare were reviewed and approved by the Committee on the Ethics of Animal Experiments of the HVRI of CAAS (approval number 2020-01-01JiPi).
Ferrets are commonly used as an animal model for viral respiratory infections in humans (
20–
26). We therefore tested the susceptibility of ferrets to SARS-CoV-2. Two virus strains were used in this study: (i) SARS-CoV-2/F13/environment/2020/Wuhan (F13-E), isolated from an environmental sample collected in the Huanan Seafood Market in Wuhan, and (ii) SARS-CoV-2/CTan/human/2020/Wuhan (CTan-H), isolated from a human patient. Pairs of ferrets were inoculated intranasally with 10
5 plaque-forming units (PFU) of F13-E or CTan-H and euthanized on day 4 postinoculation (p.i.). The nasal turbinate, soft palate, tonsils, trachea, lung, heart, liver, spleen, kidneys, pancreas, small intestine, and brain from each ferret were collected for viral RNA quantification by quantitative polymerase chain reaction and virus titration in Vero E6 cells. Viral RNA (
Fig. 1, A and B) and infectious virus (
Fig. 1, C and D) were detected in the nasal turbinate, soft palate, and tonsils of all four ferrets inoculated with these two viruses but were not detected in any other organs tested. These results indicate that SARS-CoV-2 can replicate in the upper respiratory tract of ferrets, but its replication in other organs is undetectable.
To investigate the replication dynamics of these virus strains in ferrets, groups of three animals were inoculated intranasally with 10
5 PFU of F13-E or CTan-H, and each ferret was then placed in a separate cage within an isolator. Nasal washes and rectal swabs were collected on days 2, 4, 6, 8, and 10 p.i. from the ferrets for viral RNA detection and virus titration. Body temperatures and signs of disease were monitored for 2 weeks. Viral RNA was detected in the nasal washes on days 2, 4, 6, and 8 p.i. in all six ferrets inoculated with the two strains (
Fig. 1, E and F). Viral RNA was also detected in some of the rectal swabs of the virus-inoculated ferrets, although the copy numbers were notably lower than those in the nasal washes of these ferrets (fig. S1, A and C). Infectious virus was detected from the nasal washes of all ferrets (
Fig. 1, G and H) but not from the rectal swabs of any ferrets (fig. S1, B and D).
One ferret from each virus-inoculated group developed fever and loss of appetite on days 10 (CTan-H–inoculated) and 12 p.i. (F13-E–inoculated), respectively. To investigate whether these symptoms were caused by virus replication in the lower respiratory tract, we euthanized the two ferrets on day 13 p.i. and collected their organs for viral RNA detection. However, viral RNA was not detected in any other tissues or organs of either ferret, except for a low copy number (10
5.4 copies/g) in the turbinate of the ferret inoculated with CTan-H (fig. S2). Pathological studies revealed severe lymphoplasmacytic perivasculitis and vasculitis; increased numbers of type II pneumocytes, macrophages, and neutrophils in the alveolar septa and alveolar lumen; and mild peribronchitis in the lungs of the two ferrets euthanized on day 13 p.i. (fig. S3). Antibodies against SARS-CoV-2 were detected in all ferrets by an enzyme-linked immunosorbent assay (ELISA) and a neutralization assay, although the antibody titers of the two ferrets that were euthanized on day 13 p.i. were notably lower than those of the ferrets euthanized on day 20 p.i. (
Fig. 1, I to L).
A virus attachment assay indicated that SARS-CoV-2 could attach to bronchiolar epithelial cells (fig. S4A) and some type II pneumocytes (fig. S4B) in ferret lungs. To further investigate whether SARS-CoV-2 replicates in the lungs of ferrets, we intratracheally inoculated eight ferrets with 105 PFU of CTan-H and euthanized two animals each on days 2, 4, 8, and 14 p.i. to look for viral RNA in the tissues and organs. Viral RNA was detected only in the nasal turbinate and soft palate of one ferret in each pair euthanized on days 2 and 4 p.i.; was detected in the soft palate of one ferret and in the nasal turbinate, soft palate, tonsils, and trachea of the other ferret euthanized on day 8 p.i.; and was not detected in either of the two ferrets euthanized on day 14 p.i. (fig. S5). These results indicate that SARS-CoV-2 can replicate in the upper respiratory tract of ferrets for up to 8 days without causing severe disease or death.
Cats and dogs are in close contact with humans; therefore, it is important to understand their susceptibility to SARS-CoV-2. We first investigated the replication of SARS-CoV-2 in cats. Seven subadult cats (aged 6 to 9 months, outbred domestic cats) were intranasally inoculated with 105 PFU of CTan-H. Two animals were scheduled to be euthanized on days 3 and 6 p.i., respectively, to evaluate viral replication in their organs. Three subadult cats were placed in separate cages within an isolator. To monitor respiratory droplet transmission, an uninfected cat was placed in a cage adjacent to each of the infected cats. The aggressive behavior of the subadult cats made it difficult to perform regular nasal wash collection. To avoid possible injury, we only collected feces from these cats and checked for viral RNA in their organs after euthanasia.
Viral RNA was detected in the nasal turbinate of one animal, as well as in the soft palates, tonsils, tracheas, lungs, and small intestines of both animals euthanized on day 3 p.i. (
Fig. 2A). In the animals euthanized on day 6 p.i., viral RNA was detected in the nasal turbinates, soft palates, and tonsils of both animals; in the trachea of one animal; and in the small intestine of the other. However, viral RNA was not detected in any lung samples from either of these animals (
Fig. 2C). Infectious virus was detected in the viral RNA–positive nasal turbinates, soft palates, tonsils, tracheas, and lungs of these cats but was not recovered from the viral RNA–positive small intestines (
Fig. 2, B and D)
In the transmission study, viral RNA was detected in the feces of two virus-inoculated subadult cats on day 3 p.i. and in all three virus-inoculated subadult cats on day 5 p.i. (
Fig. 3A). Viral RNA was detected in the feces of one exposed cat on day 3 p.i. (
Fig. 3A). The pair of subadult cats with viral RNA–positive feces was euthanized on day 11 p.i. Viral RNA was detected in the soft palate and tonsils of the virus-inoculated animal and in the nasal turbinate, soft palate, tonsils, and trachea of the exposed animal (
Fig. 3B), indicating that respiratory droplet transmission had occurred. We euthanized the other pairs on day 12 p.i. Viral RNA was detected in the tonsils of one virus-inoculated subadult cat and in the nasal turbinate, soft palate, tonsils, and trachea of the other virus-inoculated subadult cat but was not detected in any organs or tissues of the two exposed subadult cats (
Fig. 3B). Antibodies against SARS-CoV-2 were detected in all three virus-inoculated subadult cats and one exposed cat via an ELISA and neutralization assay (
Fig. 3, C and D).
We repeated the replication and transmission studies in juvenile cats (aged 70 to 100 days) (
Figs. 2, E to H, and
3, E to G, and fig. S6). Histopathologic studies performed on samples from the virus-inoculated juvenile cats that died or were euthanized on day 3 p.i. revealed massive lesions in the nasal and tracheal mucosa epitheliums and lungs (fig. S7). These results indicate that SARS-CoV-2 can replicate efficiently in cats and that younger cats are more vulnerable than older ones. Notably, our findings also reveal that the virus is transmissible between cats via the airborne route.
We next investigated the replication and transmission of SARS-CoV-2 in dogs. Five 3-month-old beagles were intranasally inoculated with 10
5 PFU of CTan-H and housed with two uninoculated beagles in a room. Oropharyngeal and rectal swabs from each beagle were collected on days 2, 4, 6, 8, 10, 12, and 14 p.i. for viral RNA detection and virus titration in Vero E6 cells. Viral RNA was detected in the rectal swabs of two virus-inoculated dogs on day 2 p.i. and in the rectal swab of one such dog on day 6 p.i. (
Table 1). One dog that was positive for viral RNA by rectal swab on day 2 p.i. was euthanized on day 4 p.i., but viral RNA was not detected in any organs or tissues collected from this animal (fig. S8). Additionally, infectious virus was not detected in any swabs collected from any of these dogs. Sera were collected from all dogs on day 14 p.i. for antibody detection by an ELISA. Two virus-inoculated dogs seroconverted; the other two virus-inoculated dogs and the two contact-exposed dogs were all seronegative for SARS-CoV-2 (
Table 1 and fig. S9). These results indicate that dogs have low susceptibility to SARS-CoV-2.
We also investigated the susceptibility of pigs, chickens, and ducks to SARS-CoV-2 by using the same strategy as that used to assess dogs. However, viral RNA was not detected in any swabs collected from these virus-inoculated animals or from naïve contact animals (
Table 1). In addition, all of these animals were seronegative for SARS-CoV-2 when tested by ELISA with sera collected on day 14 p.i. (
Table 1). These results indicate that pigs, chickens, and ducks are not susceptible to SARS-CoV-2.
In summary, we found that ferrets and cats are highly susceptible to SARS-CoV-2; dogs have low susceptibility; and pigs, chickens, and ducks are not susceptible to the virus. Unlike influenza viruses and the other SARS-coronavirus known to infect humans (SARS-CoV-1), which replicate in both the upper and lower respiratory tract of ferrets (
20,
22–
24,
26,
27), SARS-CoV-2 replicates only in the nasal turbinate, soft palate, and tonsils of ferrets. SARS-CoV-2 may also replicate in the digestive tract, as viral RNA was detected in the rectal swabs of the virus-infected ferrets, but virus was not detected in lung lobes, even after the ferrets were intratracheally inoculated with the virus. It remains unclear whether the virus causes more severe disease in male ferrets than in female ferrets, as has been observed among humans (
13,
28).
Several studies have reported that SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as its receptor to enter cells (
3,
29–
31). ACE2 is mainly expressed in type II pneumocytes and serous epithelial cells of tracheo-bronchial submucosal glands in ferrets (
25). Ferrets and cats differ by only two amino acids in the SARS-CoV-2 spike-contacting regions of ACE2 (table S1); therefore, the underlying mechanism that prevents the replication of SARS-CoV-2 in the lower respiratory tract of ferrets remains to be investigated. The fact that SARS-CoV-2 replicates efficiently in the upper respiratory tract of ferrets makes them a candidate animal model for evaluating the efficacy of antiviral drugs or vaccines against COVID-19.
The cats we used in this study were outbred and were susceptible to SARS-CoV-2, which replicated efficiently and was transmissible to naïve cats. Cats in Wuhan have been reported to be seropositive for SARS-CoV-2 (
32). Surveillance for SARS-CoV-2 in cats should be considered as an adjunct to elimination of COVID-19 in humans.
Acknowledgments
We thank S. Watson for editing the manuscript.
Funding: This work was supported by the National Key R&D Program of China (2020YFC0846500, 2018YFC1200601, and 2016YFD0500301).
Author contributions: J.S., Z.W., G.Z., H.Y., C.W., B.H., R.L., X.H., L.S., Z.S., Y.Z., P.L., L.L., P.C., J.W., X.Z., and Y.G. performed experiments; J.S., Z.W., G.Z., H.Y., C.W., W.T., G.W., H.C., and Z.B. analyzed data; and Z.B. and H.C. designed the study and wrote the manuscript.
Competing interests: None of the authors have any competing interests.
Data and materials availability: All data are available in the manuscript or the supplementary materials. Sequences of the viruses used in this study have been deposited in GISAID previously with the accession numbers EPI_ISL_402119 and EPI_ISL_408514. Two strains of 2019 novel coronavirus (CTan-H and F13-E) were obtained from the China CDC under a material transfer agreement that allows use only in P3+ or P4 facilities, prevents live virus sharing, and prevents commercial use. This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit
https://creativecommons.org/licenses/by/4.0/. This license does not apply to figures/photos/artwork or other content included in the article that is credited to a third party; obtain authorization from the rights holder before using such material.
Is the evidence enough to discard pigs as a possible source of COVID-19 infections to humans?
The identity of the intermediate host for SARS-CoV-2 remains unknown. A survey of pigs, which are susceptible to many coronaviruses, detected SARS‐CoV RNA and antibodies in one and two pigs (n=242), respectively (1). Hence, pigs were hypothesized as a vector for SARS-CoV-2 (2).
However, Shi et al. (3) indicated that pigs are not susceptible to SARS-CoV-2, but did so on the basis of an experiment with very low sample size (7 pigs). I, therefore, submit that their indication that pigs are not susceptible to SARS-CoV-2 may be premature.
Pigs stand out as a prevalent source of zoonosis, such as hepatitis E (4), to humans. Residues and slurries of acutely infected pigs act as sources of infections, such as the African swine fever (5) and the Aujeszky's disease (6)viruses, although infectivity is assumed to decay exponentially after death, elapsing a few days (5).
I, therefore, encourage Shi et al. (3) and scientists elsewhere to further test the putative role of pigs as vectors of SARS-CoV-2 infections. While awaiting conclusive results, I recommend a cautionary approach be adopted.
.
References and Notes:
1. W. Chen et al. Emerg. Infect. Dis. 11, 446-448 (2005)
2. T. Opriessnig, and Y.W. Huang. Xenotransplantation 27, e12591 (2020). https://doi.org/10.1111/xen.12591
3. J. Shi et al. Science 368, 1016-1020 (2020).
4. L. Christou, and M. Kosmidou, M. Clinical Microbiology and Infection 19, 600-604 (2013)
5. T. Halasa et al. Front. Vet. Sci. 3:6. doi: 10.3389/fvets.2016.00006 (2016)
6. E.C. Hahn et al. Vet. Microbiol. 55, 123-130 (1997).
7. J.W. Dyal et al. MMWR Morb Mortal Wkly Rep 69, 557–561 (2020).
8. E.M. Leroy et al. Science 303, 387-390 (2004).
RE: SARS CoV vaccine trials in ferrets, whole killed and live virus
We reported SARS CoV vaccine trials in ferrets in 2008. Ferrets make a good respiratory model and develop significant disease with hemorrhage in internal organs, especially the lungs and thymus (See, et al J Gen Virol 2008). Inactivated whole killed virus and Adenovirus vectored spike (S) and nucleocapsid (N) induced neutralizing antibodies and T lymphocyte responses (measured in mice, See et al, J Gen Virol 2006). Both vaccines reduced viral shedding from the nose, reduced lung titers (both RNA and live virus), and reduced organ damage. However, neither vaccine protected animals from significant organ and lung damage, even after receiving vaccination and boost, suggesting that improved vaccine strategies will be needed. Edema, hemorrhage, goblet cell hyperplasia and monocyte and lymphocyte infiltrate were seen. Importantly, the inactivated vaccine induced neutralizing antibodies 15 times the amount induced by Ad S/N but did not protect better. Vaccine developers should not over emphasize the importance of neutralizing antibodies when non neutralizing antibodies and T lymphocytes also play key roles in the anti-viral immune response
RE: SARS CoV vaccine trials in ferrets, whole killed and live virus
We reported SARS CoV vaccine trials in ferrets in 2008. Ferrets make a good respiratory model and develop significant disease. Even though inactivated virus and Adenovirus vectored spike (S) and nucleocapsid (N) induced neutralizing antibodies and T lymphcyte responses, the vaccines did not protect from significant organ and lung damage. The inactivated vaccine induced neutralizing antibodies 15 times the amount induced by Ad S/N, but did not protect better
R. H. See, M. Petric, D. J. Lawrence, C. P.Y. Mok, T. Rowe, L. A. Zitzow, K. P. Karunakaran, T. G. Voss, J. Gauldie, R. C. Brunham, B. B. Finlay, and R.L. Roper*. 2008. Severe Acute Respiratory Syndrome Vaccine Efficacy In Ferrets: Whole Killed Virus And Adenovirus-Vectored Vaccines. J. Gen. Virol. Sept, 89:2136-2146.
RE:Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS–coronavirus 2
Dear Sirs, I am currently a practicing small animal veterinarian and I found your article interesting. I have been having some questions coming to mind lately about Covid 19. Things may not have gotten to the point that the answers are available yet, but I wanted to share the questions I have and get some suggestions as to where to look for answers.
The question occurred to me that perhaps some of the corona viruses in dogs and cats that we deal with in the course of veterinary practice may provide some crossover protection to Covid 19 so I began looking for information about veterinary professionals and and their staff relating to their representation in the current outbreak. I assume that occupational data is among some of the data being compiled, but the only thing I can find are ratings of occupations and their probabilities of exposure based on specific factors like forward facing businesses, working in health care, first responders and the like. I haven seen anything working at it from the other end. What occupations are not represented? I really don't know if I'm just looking in the wrong place or whether that information just isn't out there yet. If they do come up with a serum neutralizing antibody test that is fairly accurate, that's probably where the answer will lie.
I remember the story of the link between milk maids exposed to cowpox, from milking cows with active lesions, being immune to smallpox and the first vaccination were by using crusts from bovine lesions. It took someone to notice and wonder why the milk maids were not affected.
One of the things that I feel may support the idea is the fact that the big cats at the Bronx Zoo were obviously very susceptible to infection, showing basically the same list of symptoms as humans and theoretically acquired it from community transmission from humans. I have read reports of two domestic cats in New York showing respiratory symptoms that were documented as Covid 19 positive. If human to feline transmission is possible and that obviously appears to be the case, why haven we seen it sweep through the domestic cat population. I would guess that a fair number of the million positive humans in the US own and live with cats. The garden variety cat that shows up at the back door and decides it wants to live with you and those from shelter situations would have a much higher probability of being exposed to FCoV than the relatively isolated big cats at the zoo. Is that the reason we are not seeing more of an issue in our domestic cats? If so couldn't it go the other way. Maybe practicing small animal veterinarians have a leg up by having been exposed over and over to animal coronaviruses like the milk maids with the pox virus of cow pox. It also makes me interested in the level of isolation of the two cats and their history of potential exposure to FCoV. Were they street cats, from a shelter situation, or were they born and bred in high-rise apartments.
I was watching something recently about how the out break of polio in the 50s affected the higher socioeconomic demographic and when it was all over with they thought it possibly had to do with increased sanitary conditions and those folks were more naive due to not dealing with the numbers and types of infections of less sanitary populations earlier in life. Part of the hygiene theory and microbiome information that has been gaining ground in the last decade or so. City folk don't deal with some of the organisms that us country folk come into contact with on a more or less daily basis.
I also read an article talking about not being able to explain why the spread is where it is and doesn't seem to be affecting places like Calcutta where people are crammed together cheek by jowl and sanitation is poor. Why is Iraq seemingly low infection, yet Iran is inundated.
The question of can humans become infected by living in close proximity with domesticated cats is a valid question, but in my way of thinking the question of does living in close proximity to domesticated cats and exposure to their FCoV provide any crossover protection to Covid 19 in humans may deserve a good hard look as well. If that were to be the case it might come in pretty handy about now.
Thanks
Your article makes me more interested about the questio
RE: A questionable report
I am writing to you on behalf of myself and 3 colleagues, 2 Anaesthesiologists (Emilio Feltri and Paul Coppens) and 1 Laboratory Director(Emanuele Minetti).
We are in full agreement with Dr Niesman comments about the paper Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS–coronavirus 2 published on April 8, 2020.
To her valuable criticisms we want to add that infecting cats under anesthesia means invalidating the results of the experiment due to the inevitable hypothemia and the lowering of the immune defenses. The choice of Telazol implies an arterial hypertension that we know to be one of the factors that facilitate the entry of the virus into the cells. For us, this a very questionable study.
Best regards,
CoViD-19, pathologists are making the difference!
CoViD-19, pathologists are
making the difference!
Dear and Esteemed Editor,
As a citizen of Italy, where the effects of the SARS-CoV-2 pandemic have been (and are still) particularly devastating, with the deaths' toll among CoViD-19-affected patients exceeding 21,000, I suffer very much from the extremely painful season that my Country and the entire world - with the only exceptions of the Arctic and Antarctic Regions - is experiencing.
As a pathologist, however, I feel "reassured" by the increasing amount of data originating from the autopsies and the ancillary histopathologic and immunohistochemical investigations performed on SARS-CoV-2- infected individuals. To this aim, the comparative pathology data obtained from experimentally challenged animals like non-human primates (macaques and marmosets) as well as cats and ferrets, both of which - as herein reported - susceptible to experimental infection (1), may prove additionally useful in dissecting viral pathogenesis among CoViD-19-affected humans. In this respect, vasculitis and intravascular coagulation, along with pulmonary endoalveolar fibrin leakage, have been recently described in the aforementioned animal disease models (1). Noteworthy, abnormal coagulation parameters compatible with disseminated intravascular coagulation (DIC) have been linked to a poor prognosis in SARS-CoV-2-infected patients, who may suddenly develop very severe forms of CoViD-19 disease often leading them to death (2). This most likely results from viral endothelial cell targeting, provided that SARS-CoV-2 gains access into host cells through the "angiotensin-converting enzyme (ACE)2 receptor" (3), which is widely expressed also by endothelial cells (4). The prominent damage induced by the virus on the inner vascular wall all throughout the body, including the blood-brain-barrier endothelial cell lining, may well explain the DIC and the "cytokine storm" experienced by those individuals who suddenly develop very severe forms of CoViD-19 disease rapidly progressing toward fatality. Indeed, while endothelial cells are immunologicaly active elements serving as antigen-presenting cells, on one side, heparin administration has been also suggested, on the other hand, as a therapeutic option efficiently counteracting the systemic coagulopathy due to SARS-CoV-2-induced endothelial cell damage (5). In other words, the "popular" medical view of CoViD-19 as a "viral pneumonia" is being progressively complemented by that of an infectious disease process characterized by a generalized coagulopathy (DIC), coupled with an exacerbated host's immune reaction (cytokine storm), both of which leading to a severe and rapidly progressing "multiorgan dysfunction". We should be very grateful for all the above to pathologists, who - hard to believe - have been and are still being left apart from the "media scene" in Italy and (I suspect) in many other Countries, a paradoxical and "two-faced Janus-like situation"!
References
1) Shi J., et al. (2020) - Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS-coronavirus 2. Science (sou: 10.1126/science.abb7015).
2) Tang N., Li D., Wang X., Sun Z. (2020) - Abnormal coagulation parameters associated with poor prognosis in patients with novel coronavirus pneumonia. J. Thromb. Haemost. 18: 844-847.
3) Lan J., et al. (2020) - Structure of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor. Nature (doi: https://doi.org/10.1038/s41586-020-2180-5).
4) Donoghue M. (2000) - A novel angiotensin converting enzyme-related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9. Circ. Res. 87: E1-E9.
5) Lin L., Lu L., Cao W., Li T. (2020) - Hypothesis for potential pathogenesis of SARS-CoV-2 infection: A review of immune changes in patients with viral pneumonia. Emerg. Microbes Infect. 9: 727-732.
Giovanni Di Guardo, DVM, Dipl. ECVP,
Professor of General Pathology and Veterinary Pathophysiology,
University of Teramo,
Faculty of Veterinary Medicine,
Località Piano d'Accio,
64100 Teramo, Italy
(E-mail address: [email protected])
Effect of coronavirus (COVID-19) on domestic animals
In December 2019, China faced a novel corona virus (COVID-19) outbreak which has become a global health emergency. The virus can cause a severe respiratory illness, like SARS and MERS, and demonstrate human-to-human transmission. The researchers say that COVID-19 not only infect humans but also infect felines and spreads from one cat to another cat- not in dogs [1]. However it has been proved that virus causes some clinical manifestation such as conjunctivitis, retinitis, anterior uveitis and optic neuritis in felines but no study is available on human ocular implications [2].
Additionally, domestic birds and animals like ducks, chicken and pigs may not harbor the infections [3]. For this purpose some experiments were conducted by giving high doses of SARS-CoV-2 in few domestic animals. The results showed that cats were not so much cause of infection to human beings so there is no need to become panic to those people having contact with felines. A study demonstrated that prevalence in domestic and wild cat is approximately 20-60% and 90% respectively. Feline CoV (FCoV) has two biotypes names as feline enteric CoV (FECV) and feline infectious peritonitis virus (FIPV). FECV causes mild diarrhea which is usually self-limiting. Due to infection in feline caecum, the virus is rapidly shed in feline feces and is the cause of fecal-oral transmission to other susceptible cats [4].
Apparently 5% cats get feline infectious peritonitis infection. FECV can also affect blood monocytes. Due to the infection to these cells clinical manifestations were observed in such cases. The Feline Infectious Peritonitis (FIP) manifestations are granulomatous serositis, protein rich serous fluids in body cavities and other granulomatous lesions as well [5]. Major clinical signs in infected felines were fever, anorexia and mild loss of body weight. However, experimental transmission resulted in death of felines within 4-5 weeks. The ocular form of the disease caused infection in various ocular segments like conjunctiva and the tissues and fluids potentially harbor the infection. Apart from conjunctivitis other manifestations were uveitis, chorioditis and retinal vasculitis [6]. So it can be concluded that ocular manifestation have poor prognosis visually and systemically.
References
1. Smriti Mallapaty, Coronavirus can infect cats — dogs, not so much. Nature, 2020, (doi: 10.1038/d41586-020-00984-8)
2. Hohdatsu T, Okada S, Ishizuka Y, Yamada H, Koyama H. The prevalence of types I and II feline coronavirus infections in cats. J Vet Med Sci. 1992;54(3):557–562. doi:10.1292/jvms.54.557.
3. Pedersen NC, Boyle JF, Floyd K, Fudge A, Barker J. An enteric coronavirus infection of cats and its relationship to feline infectious peritonitis. Am J Vet Res. 1981;42:368–377.
4. Jaimes JA, Whittaker GR. Feline coronavirus: insights into viral pathogenesis based on the spike protein structure and function. Virology. 2018;517:108–121. (doi:10.1016/j.virol.2017.12.027).
5. Chang HW, Egberink HF, Rottier PJ. Sequence analysis of feline coronaviruses and the circulating virulent/avirulent theory. Emerg Infect Dis. 2011;17(4):744–746. (doi:10.3201/eid1704.102027).
6. Pedersen, N.C., Liu, H., Scarlett, J., Leutenegger, C.M., Golovko, L., Kennedy, H. and Kamal, F.M., 2012. Feline infectious peritonitis: role of the feline coronavirus 3c gene in intestinal tropism and pathogenicity based upon isolates from resident and adopted shelter cats. Virus research, 165(1), pp.17-28.
ACE2 isoforms explain the host susceptibility of SARS-CoV-2
ACE2 isoforms explain the host susceptibility of SARS-CoV-2
Shan Gao, Junwen Luan, Haoran Cui, Leiliang Zhang*
Institute of Basic Medicine, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250062, Shandong, China
*Corresponding Author
Contact Information:
Leiliang Zhang, PhD
Institute of Basic Medicine, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250062, Shandong, China. Email: [email protected]
In their report "Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS-coronavirus-2", J. Shi et al found that cat/ferret but not dog/pig are permissive to SARS-CoV-2 (1). However, ACE2 proteins from cat, dog, ferret and pig were all predicted to be able to associate with SARS-CoV-2 S (2, 3). There must be other factors involved in determining host range of SARS-CoV-2.
Alternative splicing of protein generates isoforms of different sizes. Thus, we looked up and compared the potential isoforms of ACE2 from cat, dog, ferret and pig in UniProt (https://www.uniprot.org/).
There are five dog isoforms, one of which lacks transmembrane domain and so it is a soluble dog ACE2. Soluble human ACE2 was reported to block the interaction between ACE2 and SARS-CoV-2 S (4). We think that soluble dog ACE2 could play a competitive inhibitory role for interaction between ACE2 and S, leaving dog not susceptible for SARS-CoV-2 infection. Pig has one ACE2 isoform lacking the N terminal 1-122 residues of ACE2, which contains critical sites for S binding (5). The dimer formed by the N terminal deletion isoform and pig ACE2 would not recognize S protein, resulting in the consequence that pig is not susceptible for SARS-CoV-2.
Ferret has only one ACE2 isoform. Cat has three isoforms, all of which maintain the critical residues for S binding. Above animals are predicted to support SARS-CoV-2 infection, which is consistent with the experimental evidences (4).
Acknowledgements
This work was supported by grants from Academic promotion programme of Shandong First Medical University [2019LJ001] and the Innovation Project of Shandong Academy of Medical Sciences.
RE: Artificial and unnatural viral dose
Dear Science Editors
Even as a BioRxiv release last week, this paper drew the ire of every major Veterinary society globally. It lacked quality controls, sufficient cat numbers and questionable housing conditions to reach any solid conclusions. Maybe the authors intentions were to quickly screen a large number of species and they did their studies as fast as possible to yield results to follow up in more rigorous studies. But, releasing these types of results only inflames public distrust of science and endangers all cats, owned, sheltered or feral. We do not know the human dose of virus that causes disease. Giving <900g 2-3 month old kittens 100,000 live virions deep in the exact site we know can elicit infection and watching them die is hardly the kind of study Science should be reporting. I expect better from a top-tier journal. Reporting 1 out of 3 pairs as possible cat-cat transmission is also suspect. We know that cage cleaning is a major route of all feline viral transmission. Dr. Kate Hurley from UC-Davis advocates use of low stress dual compartment cages to prevent viral spread between housed cats. It is unclear what practices were used on the exposed/naïve pairs. A more likely scenario is that keepers transferred the virus to the previously uninfected cat.
Yes, at some point we will want to understand how cats may acquire this virus. So far, it is still unclear if domestic cats show Covid-19 symptoms. The only reported case from Belgium could easily have been the result of any other number of known feline respiratory viruses. It was not test for others. No matter how you look at the information, two things are indisputable; any cat infected is from humans and if infectious was rampant, we would have significant numbers of reported cases. Next time wait until there is a better, more controlled and more natural method of infection to publish such a controversial and poor quality paper.
We have 1.5 million positive humans and one cat – one tiger. And, we had to forcibly infect cats. That should tell you all we need to know.