Unexpected Cases in Field Diagnosis of African Swine Fever Virus in Vietnam The Needs Consideration When Performing Molecular Diagnostic Tests

• Published in: Open veterinary journal (Tripoli, Libya) Vol. 10; no. 2; pp. 189 - 197
• Main Authors: Chu , Thi Nhu, Tran , Ha Thi Thanh, Truong , Anh Duc, Nguyen , Thi Chinh, Dang , Hoang Vu, Vu , Thi Hao, Ly , Duc Viet, Pham , Ngoc Thi, Nguyen , The Vinh, Hoang , Van Tuan, Nguyen , Huyen Thi
• Format: Journal Article
• Language: English
• Published: Tarabulus - Libya Faculty of Veterinary Medicine, University of Tripoli 01-01-2020; Faculty of Veterinary Medicine; Tripoli University
• Subjects: african swine fever; African Swine Fever - diagnosis; African Swine Fever - pathology; African Swine Fever - virology; African Swine Fever Virus - genetics; African Swine Fever Virus - isolation & purification; Animals; BIOCHEMISTRY; False Negative Reactions; Macrophages, Alveolar - virology; Molecular Diagnostic Techniques - veterinary; Original Research; pcr; PESTIVIRUS; pigs; Polymerase Chain Reaction - veterinary; real-time pcr; Real-Time Polymerase Chain Reaction - veterinary; Swine; SWINE FEVER; VETERINARY MEDICINE; VIET NAM; Vietnam; الطب البيطري; الكيمياء الحيوية; حمى الخنازير; فيتنام; فيروس الطاعون; Vietnam; Pigs; Vietnam; African swine fever; Real-time PCR; PCR
• ISSN: 2226-4485; 2218-6050; 2218-6050
• DOI: 10.4314/ovj.v10i2.8

The first confirmed case of African swine fever (ASF) in Vietnam was reported officially in February 2019. To date, ASF virus (ASFV) have been detected in 63/63 provinces in Vietnam. Currently, real-time polymerase chain reaction (PCR) is considered to be a powerful tool for viral detection in field samples, including ASFV. However, some recent reports have suggested that mismatches in primer and probe binding regions may directly affect real-time PCR qualification, leading a false-negative result.
This study aims to further examine a conflicting result obtained from two OIE recommended methods, conventional PCR and real-time PCR, for ASFV detection.
Two ASF suspected pigs from different provinces in the north of Vietnam were selected for this study based on clinical signs and postmortem lesions. The different results obtained by OIE-recommended conventional PCR and real-time PCR were further analyzed by the Sanger sequencing method and virus isolation in combination with hemadsorption (HAD) test using porcine alveolar macrophages cells.
The results showed that when the primer sequence matched perfectly with the sequences of field isolates, a mutation in probe binding region was found, indicating that a single mismatch in the probe binding site may cause a false-negative result by real-time PCR in detecting ASFV in clinical samples in Vietnam. An agreement between conventional PCR, using PPA1/PPA2 primers and two golden standard methods, virus isolation in combination with HAD assay, and sequencing method was observed in this study.
A single mismatch in the probe binding site caused a failse-negative result by realtime PCR method in field diagnosis of ASFV. The needs consideration when selecting the appropriate molecular diagnostic methods is based on the current databases of ASFV sequences, particularly for epidemiological surveillance of ASF.