In a recent study published on Research Square* preprint server, researchers explored the clinical and epidemiological features of coronavirus disease 2019 (COVID-19) in dogs and cats.
Many beneficial effects of pet ownership, including mental health benefits, have been scientifically established. Companion animals account for 60% of all animals reported to the World Organization for Animal Health (WOAH) worldwide between February 29, 2020 and December 31, 2021, making them the second most common group of animals. often reported to be infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after farmed mink. Nationally and internationally, however, surveillance efforts are limited to identify zoonotic disease transmission of pathogens, such as SARS-CoV-2, in companion animals.
Study: Clinical and epidemiological characteristics of SARS-CoV-2 in dogs and cats compiled as part of national surveillance in the United States. Image Credit: Lindsay Helms / Shutterstock
About the study
In the present study, researchers from the United States. The Centers for Disease Control and Prevention (CDC), the US Department of Agriculture (USDA) and Texas A&M University have described the clinical and epidemiological features of SARS-CoV-2 in companion animals in the United States that have been discovered through passive and active methods. surveillance.
Animal cases of SARS-CoV-2 are detected in the United States through passive or aggressive surveillance. For example, when pet owners bring their pets to veterinary clinics or hospitals, case identification is often initiated through passive surveillance. Samples are then sent to various veterinary diagnostic laboratories for SARS-CoV-2 testing. Additionally, animals with known exposure to SARS-CoV-2 or clinical symptoms suggestive of SARS-CoV-2 infection are actively sought by health officials or researchers through active surveillance. . These include joint One Health studies of SARS-CoV2 transmission in households, zoos, animal shelters, animal rescues, animal rehabilitation facilities and veterinary clinics involving both people and animals.
According to the U.S. case definition, an animal is declared positive for SARS-CoV-2 by the U.S. Department of Agriculture’s National Veterinary Services Laboratories (USDA-NVSL) if any of the following conditions are true : (1) the SARS-CoV-2 CoV-2 sequence was generated directly from suspected or presumptive positive animal samples or indirectly from a virus isolate obtained from that animal, or (2 ) a serological sample from a suspected or presumptive positive animal showed the presence of SARS-CoV-2 neutralizing antibodies.
All dog and cat samples that met the following conditions were required to be submitted for USDA-NVSL: (1) high-sequencing candidates with a SARS reverse transcription-polymerase chain reaction (RT-PCR) cycle threshold -CoV-2 in real time (Ct) values less than 30; (2) related to unusual morbidity and mortality events; or (3) suspected or known to be infected with SARS-CoV-2 variants, including Alpha, Delta, and Omicron variants.
Based on the body systems affected, the researchers divided the clinical indicators into three categories: respiratory signs, including cough, shortness of breath, difficulty breathing, sneezing, runny nose and eye discharge, gastrointestinal symptoms, including vomiting and diarrhea , and non-specific symptoms such as lethargy, inappetence, fever). Additionally, ct values and virus neutralization (VN) titers were measured after exposure to a COVID-19 infected person to understand the infection timeline and immune response of COVID-19 infected pets. SARS-CoV-2.
The results of the SARS-CoV-2 RT-PCR and SARS-CoV-2 VN titers were compared to those observed at the presumed date of exposure. Geometric mean titer and lowest Ct values among oral and nasal swabs were calculated every other day. For animals confirmed to be infected with COVID-19, mean Ct values and log-transformed geometric mean viral neutralizing antibody titers were determined.
Approximately 345 animals observed in 33 states in the United States tested positive for SARS-CoV-2 between March 2020 and December 2021. Nearly 59% of them, including 109 cats and 95 dogs, were pets , while 94% of pet cases discovered through passive surveillance involved initial contact with a COVID-19 positive person.
Clinical signs reported in cats (n=55; A) and dogs (n=42; B). Of 97 animals showing clinical signs, the proportion of each clinical sign displayed is indicated within each species. Since a given animal may show more than one clinical sign, the percentages are calculated based on the number of signs displayed and not per individual animal.
Study results showed that 52% of pets had no documented clinical indication at the time of sampling, while 48% had clinical signs consistent with SARS-CoV-2 infection. This differed significantly depending on the type of monitoring used; although 72% of animals discovered by passive surveillance showed clinical symptoms, only 27% of those discovered by active surveillance reported signs.
Animals with clinical signs were most often reported as having respiratory symptoms versus non-specific and gastrointestinal symptoms. Of animals with clinical symptoms, 21% and 16% of cats exhibited sneezing and lethargy, while 16% and 20% of dogs had cough and lethargy, respectively.
Of the 204 confirmed COVID-19 positive pets, 45% tested positive by VN alone, 33% by RT-PCR only, and 23% by VN and RT-PCR. For all pets that tested positive using RT-PCR data, the mean Ct value was 28.6. All pets confirmed positive for COVID-19 had median VN titers of 64, ranging from 8 to 512. Of these, dog titers ranged from 8 to 128 with a median titer of 32, while those of cats ranged from 32 to 512 with a median titer of 128.
The study results showed that companion animals like dogs and cats are infected with SARS-CoV-2 after being exposed to a COVID-19 infected person who is often their owner. Therefore, case studies and surveillance involving both humans and animals are essential to understand the transmission and viral development of zoonotic diseases like SARS-CoV-2.
Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.