Dear Editor,
In June 2021, Udom et al. published their article in Transboundary and Emerging Diseases performing a serological survey revealed evidence of anti-N-IgG antibodies suggesting SARS-CoV-2 exposure in both dogs and cats during the first and second coronavirus disease 2019 (COVID-19) outbreaks in Thailand (Udom et al. 2021). Seroprevalence studies have proven an important tool to monitor the progression of the COVID-19 pandemic (Cuellar et al. 2020). The duration of immunity of SARS-CoV-2 is crucial for the course of the pandemic and for this reason the monitoring of antibodies against SARS-CoV-2 is important. The serum samples from different periods and regions were valuable in terms of scientific significance for serological survey of SARS-CoV-2 and emerging infectious diseases (Deng et al. 2020; Stranieri et al. 2021; Van Aart et al. 2021; Zhao et al. 2021). In order to preserve the remaining serum samples and ensure the stability of anti-virus antibodies in storage serum samples, we strongly suggest that standard serum banks should be established worldwide.
The key to this study was the 3215 serum samples from dogs (n = 2102) and cats (n = 1113), which were collected from six zones of Bangkok and nearby provinces (Nakhon Pathom, Nonthaburi, Pathum Thani, Samut Sakhon and Samut Prakan) in Thailand. According to the manuscript, “Approximately 3 ml of blood was collected from each animal, and serum was separated by centrifugation and then stored at -20℃ until use”. Notably, the transportation conditions and time between blood sampling and detection of the serum samples were not mentioned in the manuscript. There is no evidence regarding the stability of SARS-CoV-2-specific antibodies during different storage temperature and time. The stability of the anti-SARS-CoV-2 immunoglobulin may influence the results and conclusion of the study. The transportation storage conditions of the serum samples should be included in description of serological surveys of SARS-CoV-2 in the future (Weidinger et al. 2021).
Besides the SARS-CoV-2, the samples from the serum bank should be used for serological studies of other emerging infectious diseases in the future (Ayouba et al. 2019; Barua et al. 2021; Kumar et al. 2020). The establishment of serum banks should consider the following three points. First, the samples should be collected from people, animals and bats from different regions and times, especially the remaining serum samples from previously serological surveys (Ayouba et al. 2019; Barua et al. 2021; Deng et al. 2020; Kumar et al. 2020). Second, the serum samples should be evaluated using formulated exclusion and inclusion criteria before being included in the serum bank. Third, serum banks should include standard preservation conditions and sample background (Cuellar et al. 2020). All steps from blood sample collection to cold-chain transportation should be in accordance with the standard operating procedures (Weidinger et al. 2021).
Thank you for your attention in considering this comment and we are looking forward to your response.