title: No evidence for lymphatic filariasis transmission in big cities affected by conflict related rural-urban migration in Sierra Leone and Liberia.
abstract: BACKGROUND
  In West Africa, the principal vectors of lymphatic filariasis (LF) are Anopheles species with Culex species playing only a minor role in transmission, if any. Being a predominantly rural disease, the question remains whether conflict-related migration of rural populations into urban areas would be sufficient for active transmission of the parasite.
  
  
  RESULTS
  We examined LF transmission in urban areas in post-conflict Sierra Leone and Liberia that experienced significant rural-urban migration. Mosquitoes from Freetown and Monrovia, were analyzed for infection with Wuchereria bancrofti. We also undertook a transmission assessment survey (TAS) in Bo and Pujehun districts in Sierra Leone. The majority of the mosquitoes collected were Culex species, while Anopheles species were present in low numbers. The mosquitoes were analyzed in pools, with a maximum of 20 mosquitoes per pool. In both countries, a total of 1731 An. gambiae and 14342 Culex were analyzed for W. bancrofti, using the PCR. Two pools of Culex mosquitoes and 1 pool of An. gambiae were found infected from one community in Freetown. Pool screening analysis indicated a maximum likelihood of infection of 0.004 (95% CI of 0.00012-0.021) and 0.015 (95% CI of 0.0018-0.052) for the An. gambiae and Culex respectively. The results indicate that An. gambiae is present in low numbers, with a microfilaria prevalence breaking threshold value not sufficient to maintain transmission. The results of the TAS in Bo and Pujehun also indicated an antigen prevalence of 0.19% and 0.67% in children, respectively. This is well below the recommended 2% level for stopping MDA in Anopheles transmission areas, according to WHO guidelines.
  
  
  CONCLUSIONS
  We found no evidence for active transmission of LF in cities, where internally displaced persons from rural areas lived for many years during the more than 10 years conflict in Sierra Leone and Liberia.
authors: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
authors: Dziedzom K
authors: DK
authors: de Souza
authors: Ministry of Health and Sanitation, Freetown, Sierra Leone.
authors: Santigie
authors: S
authors: Sesay
authors: Ministry of Health and Social Welfare, Monrovia, Liberia.
authors: Marnijina G
authors: MG
authors: Moore
authors: Mercy Hospital Research Laboratory, Bo, Sierra Leone ; Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors: Rashid
authors: R
authors: Ansumana
authors: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
authors: Charles A
authors: CA
authors: Narh
authors: Ministry of Health and Social Welfare, Monrovia, Liberia.
authors: Karsor
authors: K
authors: Kollie
authors: Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors: Maria P
authors: MP
authors: Rebollo
authors: Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors: Benjamin G
authors: BG
authors: Koudou
authors: Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors: Joseph B
authors: JB
authors: Koroma
authors: Liberian Institute for Biomedical Research, Charlesville, Liberia.
authors: Fatorma K
authors: FK
authors: Bolay
authors: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
authors: Daniel A
authors: DA
authors: Boakye
authors: Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors: Moses J
authors: MJ
authors: Bockarie
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology; D002947:Cities; D003465:Culex / Q000469:parasitology; D004605:Elephantiasis, Filarial / Q000453:epidemiology / Q000469:parasitology / Q000635:transmission*; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology; D007988:Liberia / Q000453:epidemiology; D008297:Male; D011157:Population Dynamics / Q000706:statistics & numerical data*; D012424:Rural Population; D012807:Sierra Leone / Q000453:epidemiology; D014857:Warfare; D014958:Wuchereria bancrofti / Q000235:genetics / Q000302:isolation & purification