RAPID DIAGNOSIS AND VIREMIA DURATION STUDY IN DENGUE HEAMORRHAGIC FEVER BY RT/PCR
(Reverse-Transcriptase/Polymerase Chain Reaction)

 

Vu Thi Que Huong1, Do Quang Ha1, Nguyen Trong Lan2, Nguyen Thanh Hung2,

Vo Dinh Tham3, Claudine Roche4, Eliane Chungue4 vař Vincent Deubel5.

1 Pasteur Institute of HoChiMinh - 2, 3 Pediatric Hospital No. 1 & 2 - Grall,

4 Institut Territorial des Recherches Medicales Louis-Malarde’, Tahiti, 5 Institut Pasteur Paris.

 

Dengue hemorrhagic fever (DHF), caused by the 4 serotypes of dengue viruses, is a major problem of public health in South Vietnam. The epidemiological and clinical studies of DF/DHF were based on virological and serological diagnosis. However, it is very difficult to recover the dengue virus from the DHF patients’ specimens which had the anti-dengue antibodies or were transported in bad conditions.

In this study, we applied the RT/PCR method using a pair of consensus oligonucleotide primers (d1, d2), then continued by a semi-nested-PCR using the serotype-specific primers (TS1, TS2, TS3, TS4) (Lanciotti et al., 1992) for the detection of dengue virus serotypes from DHF patients’ sera. The rapidity, sensitivity and specificity of the RT-PCR were demonstrated in the identification of dengue isolates (Chung et al., 1993).

99 DHF patients (from 8 to 15 years) selected in 2 pediatric hospitals No.1 and 2 in HoChiMinh City (1995–1996), their grades were classified as: 2 DF cases, 43 DHF cases et 54 DSS cases. The percentage of the primary and the secondary infections were 20% and 78%, respectively. For studying the viraemia, their sequencial sera were tested by RT/PCR and by viral isolation on C6/36 cells. Nine strains of dengue viruses (1 dengue-1, 6 dengue-2 and 2 dengue-3) were isolated by cell culture. These 9 sera were also positive in RT/PCR. Of 57 sera which were negative in viral isolation, there were 32 sera positive in RT/PCR. Moreover, viral ARN were detected by RT/PCR in patient sera obtained on the third day of fever (6/6 cases).

The mean clearance of the viral RNA detection in sera was 5 days and 17% of DHF patients maintained their positive results from 5th to 9th day of the illness. Viral RNA detection rate was higher in primary dengue infections (p=0.003). The mean viremia duration (which was detected by RT/PCR) for each dengue virus serotype did not correlate with disease severity (grade) (p=0.23) or antibody responses (p=0.4).