Formalin Inactivation of Virus for Safe Downstream Processing of Routine Stool Parasite Examination during the COVID-19 Pandemic

• Published in: Diagnostics (Basel) Vol. 13; no. 3; p. 466
• Main Authors: Chinabut, Pisith, Sawangkla, Nuntiya, Wattano, Suphaluck, Thavorasak, Techit, Bootsongkorn, Weluga, Tungtrongchitr, Anchalee, Ruenchit, Pichet
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27.01.2023; MDPI
• Subjects: Control; Coronaviruses; COVID-19; Epidemics; Formaldehyde; formalin; Health aspects; inactivation; infectious diseases; Influence; isotonic formalin; Laboratories; normal saline solution; Pandemics; Parasites; Thailand; Viruses; Thailand; Austria; Grand Island New York; United States > US; COVID-19; isotonic formalin; white blood cell; formalin; inactivation; infectious diseases; normal saline solution; stool examination; red blood cell
• ISSN: 2075-4418; 2075-4418
• DOI: 10.3390/diagnostics13030466

During the COVID-19 pandemic, the parasitology laboratories dealing with fecal samples for the diagnosis of gastrointestinal parasitic infections are confronting the unsaved virus-containing samples. To allow for safe downstream processing of the fecal samples, a protocol for preparing a fecal smear is urgently needed. Formalin was tested with or without isotonic forms for virus inactivation using porcine epidemic diarrhea virus (PEDV) as a representative, as it belongs to the Coronaviridae family. The results revealed complete inactivation activity of 10% formalin and 10% isotonic formalin on coronavirus after 5 min of treatment at room temperature. Both also inhibited growth after 5 min of treatment at 37 °C without disruption of the structure. In addition to these key findings, it was also found that isotonic formalin could stabilize both red and white blood cells when used as a solution to prepare fecal smears comparable to the standard method, highlighting its value for use instead of 0.9% normal saline solution for the quantification of blood cells without active virus. The 10% isotonic formalin is useful to safely prepare a fecal smear for the diagnosis of parasites and other infections of the gastrointestinal tract during the COVID-19 pandemic.