Imported Bancroftian Filariasis: Parasitological and Serological Responses to a 300 mg Single-dose Diethylcarbamazine and Drug Resistance Monitoring - โรคหนอนพยาธิฟิลาเรียชนิดแบนครอฟเตียนสายพันธ์นำเข้า : การตอบสนองทางปรสิตวิทยาและทางซีโรโลยีต่อยาไดเอทธิลคาร์บามาซีน ขนาด 300 มิลลิกรัม ชนิดกินครั้งเดียว และการติดตามการดื้อยา

Abstract

                       One line approach of the National Program to Eliminate Lymphatic Filariasis (PELF) in Thailand during fiscal years 2002-2006 that focuses on multiple-dose diethylcarbamazine (DEC) mass treatment is to large-scale control imported bancroftian filariasis to prevent introduced infection in vulnerable local population. The disease caused by the nocturnally periodic strain of Wuchereria bancrofti is common among cross-border Myanmar migrant workers.  This study was aimed at evaluating drug responses (i.e., parasitological and serological) in both microfilaremics and amicrofilaremics, and to investigate resistance mutation of the W. bancrofti population in microfilaremic carriers. Of the 1,133 migrants whose blood samples were parasitologically and serologically determined, the 14 antigenemic cases including 7 microfilaremics and 7 matched amicrofilaremics were recruited. They were treated with a 300 mg single oral-dose DEC, and parasite loads (microfilaremia and/or antigenemia) were monitored at DEC-post treatment, 1, 2, and 3 months. Both groups had dramatic reduction of antigen loads in relation to time required to clear, but month 2 showed significant difference in antigen loads (p = 0.013). In microfilaremic group, reduction of microfilariae and antigen loads at individual level was independent of time required to clear infection and intensity. By W. bancrofti beta-tubulin gene-specific polymerase chain reaction, all the microfilariae isolates gave positive amplification of 607 bp amplicons which deduced amino acid sequences did not confer resistant mutations at position neither Phe 167 Tyr nor Phe 200 Tyr over a period of treatment. The principal outcomes would likely be beneficial for the PELFีs implementers at the provincial level to evaluate and monitor the PELF implementation effectiveness in drug response and resistance and in particular towards short-term migrants.

Key words:  imported bancroftian filariasis, long-term migration, multiple-dose diethylcarbamazine, Myanmar migrants, National Program to Eliminate Lymphatic Filariasis, resistant mutations, short-term migration, Wuchereria bancrofti