Epidemiology and Infection

Transmission of the nocturnal periodic strain of Wuchereria bancrofti by Culex quinquefasciatus: establishing the potential for urban filariasis in Thailand

a1 Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
a2 Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
a3 Filariasis Division, CDC, Ministry of Public Health, Bangkok, Thailand
a4 The Johns Hopkins University School of Public Health, Baltimore, MD 21205


Control programmes have reduced the prevalence of Bancroftian filariasis in Thailand to low levels. Recently, there has been an influx of more than one million Myanmar immigrants into urban centres of Thailand. The prevalence of patent Wuchereria bancrofti infection in these immigrants (2–5%) has prompted concern in the public health community that the potential now exists for a re-emergence of Bancroftian filariasis in Thailand. It is possible that an urban cycle of transmission could become established. The Myanmar immigrants are infected with the nocturnal periodic (urban) type W. bancrofti for which Culex quinquefasciatus serves as the main vector. The Thai strains of Cx. quinquefasciatus have never been reported to transmit Bancroftian filariasis. Our results of feeding experiments demonstrated that the Thai Cx. quinquefasciatus are permissive for the development of Myanmar W. bancrofti to infective third-stage larvae thus establishing the potential for establishing an urban cycle of transmission in Thailand. We also adapted the SspI repeat PCR assay for the identification of infective mosquitoes that was capable of detecting a single infective stage larvae in a pool of 100 mosquitoes.

(Accepted March 14 2000)

c1 Author for correspondence.