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.