This study describes the rapid detection of polioviruses in environmental waters by a simple reverse transcriptase-polymerase chain reaction (RT-PCR) using two primer pairs for differentiation of poliovirus from non-polio enteroviruses in a single reaction with a one-step method, combining RT and PCR in a single tube. The detection by agarose gel electrophoresis yielded 2 bands of 153-bp and 293-bp for poliovirus tested without the need for further hybridization. The detection sensitivity of this one-step duplex RT-PCR, as measured with RNA extracted by heat treatment from supernatant of infected cell extracts, was 10^-1 50% tissue culture effective doses (TCID₅₀). This assay was used to evaluate the ability of sample concentration by membrane filter-based adsorption and elution, and purification by a simple RNA isolation based on guanidine isothiocyanate-phenol-chloroform extraction; the system yielded a detection limit of 5 X 10^-1 TCID₅₀ seeded in 5 liters of tap water. This protocol was applied to the poliovirus detection in environmental water collected from 2 communities in Bangkok, Thailand during February and May 1998. Of 100 samples tested, 2 water samples collected from the same opening sewage pipeline at one location were positive for polioviruses and one sample collected from another sewage pipeline was positive for non-polio enterovirus while a further 97 water samples were negative for both polioviruses and non-polio enteroviruses. With poliovirus detection by cell culture technique, none of the 100 samples tested was positive for poliovirus type 1, 2 or 3. RT-PCR was more sensitive, rapid, simple and cost-effective than the cell culture technique since the two water samples which were positive for polioviruses by RT-PCR failed to be detected by cell culture. Sequence data of 293-bp amplicons from positive samples were compared with those of reference poliovirus strains of the Genbank and the EMBL databases and identity to the sequence of type 1 strain Sabin was found to be 99%.

(SEA J Trop Med and Pub Hlth 2000; 31 (1): 47-56.)

  Diagnosis of Wuchereria bancrofti infection in endemic 
  populations : Diagnostic  approaches to control and 
  elimination (NO. 543)

Key words : Wuchereria bancrofti, microfilariae, diethylcarbamazine, polymerase chain reaction, ultrasonography, Og4C3 ELISA, ICT Filariasis

                    The detection of Wuchereria bancrofti microfilariae in populations of risk communities is essentially important for disease surveillance and monitoring the effectiveness of control programmes. Traditional thick smear for night blood survey and evaluating diethylcarbamazine (DEC)-efficacious therapy may not be reliable enough to identify the areas where interruption of transmission and elimination of the human infection are completely achieved. The authors have reviewed and focused on medical advances in currently simplier diagnosis of W. bancrofti infection. Diagnosis methods including parasitological, serological and clinical diagnostic methods are arbitrarily qualitatively assessed in terms of sensitivity, specificity, technical difficulty and cost, so as to provide a general guideline of diagnostic approaches (or “direct assessment tools”) accessible to the integrated laboratory- and field-based surveillances (ILFS) of bancroftian filariasis. Direct assessment tools include evaluation and monitoring of the human and mosquito infections by polymerase chain reaction (PCR) assay and of human infection and effective treatments with antifilarial drugs by ultrasonography, by Og4C3 ELISA, and by ICT Filariasis. All are considered to highlight the advantages for use in lymphatic filariasis control and elimination, and chief obstacles when they are applied in demonstrated areas where to target community-wide mass treatment under the national programme of the elimination of lymphatic filariasis, and internationally within endemic countries.

(Publication: Mahidol J 2000; 7: 101-7. Financial Support: Department of Communicable Disease Control, Ministry of Public Health, Thailand)

  Field trial of the ICT Filariasis for diagnosis of Wuchereria 
  bancrofti infections in an  endemic population of Thailand 
  (NO. 544)

                    The ICT Filariasis, a rapid card test format, which is based on qualitative detection by monoclonal antibody of the circulating antigen of Wuchereria bancrofti adult worm, is a new diagnostic test of choice for determining the infections under field conditions. By using clinical and recall techniques and microscopy (thick smear and capillary tube technique) as reference, we assessed the efficiency of the ICT card test in sera from 225 subjects living in W. bancrofti-endemic villages of Tak Province, Thailand, who were recruited during a cross-sectional community survey. The ICT card test gave 20% antigen positive rate as other tests gave lower positive rates of the same 5.8% by clinical and recall techniques and thick smear, and 5.3% by capillary tube technique, respectively. The ICT card test had a specificity of 100% when sera from microfilaremic subjects were positive, as when sera from W. bancrofti non-endemic subjects either with Brugia malayi microfilaremia or with other parasites, and those from normal controls were all negative by the test. When done in W. bancrofti microfilaremia sera, the ICT card test had a sensitivity of 100% using a microscopy as reference, and 84.6% when using clinical and recall techniques. However, the ICT card test was more sensitive than the others when done in endemic normal sera (14% positive). Such findings compared well with findings in endemic area of South America, suggested its usefulness to detect W.