Does longevity of adult Wuchereria bancrofti increase with decreasing intensity of parasite transmission? Insights from clinical observations.
To interrupt transmission of Wuchereria bancrofti, a parasite that causes lymphatic filariasis, mass treatment of at-risk populations with antifilarial drugs is recommended for 4-6 years, the minimum estimated adult worm lifespan. Factors associated with adult worm longevity are unknown. In Recife, Brazil, we conducted a retrospective cohort study of 57 men whose adult W. bancrofti were not sensitive to diethylcarbamazine and who were followed with semi-annual physical examinations (to detect intrascrotal nodules, indicative of adult worm death) and ultrasound examinations (to detect the 'filaria dance sign' (FDS), indicative of living adult worms). After 5 years, the FDS remained detectable in 10 (24.4%) of 41 adult worm nests in 25 men from areas of high filariasis transmission intensity and in 30 (90.9%) of 33 nests in 32 men from areas of low transmission (P<0.001). New nodules and adult worm nests were detected only in men from high-transmission areas. Of 30 men who were microfilaria-positive initially and whose FDS remained detectable after 5 years of follow-up, 19 (63.3%) remained microfilaria-positive in 5 ml blood (mean density, 0.4 per ml). In conclusion, survival of adult W. bancrofti is inversely associated with transmission intensity. These findings have implications for filariasis elimination and research.
Dreyer
Gerusa
G
Centro de Pesquisas Aggeu Magalhães, FIOCRUZ, and NEPAF, Hospital das Clínicas, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego s/n, Cidade Universitária, CEP 50670-420, Recife PE, Brazil. dreyer-g@uol.com.br
Addiss
David
D
Norões
Joaquim
J
D000293:Adolescent; D000328:Adult; D000818:Animals; D001938:Brazil; D002908:Chronic Disease; D004049:Diethylcarbamazine / Q000494:pharmacology; D004351:Drug Resistance; D004605:Elephantiasis, Filarial / Q000000981:diagnostic imaging / Q000469:parasitology* / Q000635:transmission*; D004812:Epidemiologic Methods; D005369:Filaricides / Q000494:pharmacology; D006790:Host-Parasite Interactions; D006801:Humans; D008136:Longevity; D008297:Male; D012611:Scrotum / Q000469:parasitology; D014463:Ultrasonography; D014958:Wuchereria bancrofti / Q000187:drug effects / Q000302:isolation & purification* / Q000502:physiology
D005369:Filaricides; D004049:Diethylcarbamazine