Epidemiology of malaria in a village in the Rufiji River Delta, Tanzania: declining transmission over 25 years revealed by different parasitological metrics

Malaria Journal

Research

Anders Björkman¹  Zulfiqarali G Premji²  Manijeh Vafa Homann³  Victor Yman³  Anna Färnert³  Grace Wandell³  Johanna Sandlund³  Ingegerd Rooth⁴  Salome Jesaja⁵  Leah Mhoja⁵  Marita Johansson⁵  Kazuyuki Tanabe⁶  Ulf Hammar⁷  Matteo Bottai⁷ 

[1] Department of Microbiology and Tumour Biology, Karolinska Institutet, Stockholm, Sweden;Department of Parasitology and Entomology, Muhimbili University College of Health Science, Dar es Salaam, Tanzania;Department of Pathology, Aga Khan University Hospital, Nairobi, Kenya;Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden;Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden;Nyamisati Malaria Research, Rufiji, Tanzania;Nyamisati Malaria Research, Rufiji, Tanzania;Osaka Institute of Technology, Osaka, Japan;Unit of Biostatistics, Department of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden;

关键词: Malaria;    Parasite prevalence;    PCR;    Microscopy;    Spleen;    Epidemiology;    Transmission;    Tanzania;   

DOI  :  10.1186/1475-2875-13-459

 received in 2014-08-30, accepted in 2014-11-17,  发布年份 2014

来源: Springer

【 摘 要 】

BackgroundAssessments of the epidemiology of malaria over time are needed to understand changes in transmission and guide control and elimination strategies.MethodsA longitudinal population study was established in 1985 in Nyamisati village in the Rufiji River Delta, Tanzania. A physician and research team lived in the village 1984–2000. Parasite prevalence by microscopy and two PCR methods, spleen rates and haemoglobin levels were measured in repeated cross-sectional surveys between 1985 and 2010. Passive surveillance of malaria cases was maintained until end 1999. Bed nets were distributed after the surveys 1993, 1999 and 2010.ResultsIn 1985, overall parasite prevalence by microscopy was 70% (90% in children ages two to nine years). The prevalence decreased gradually by microscopy (38.9% 1994, 26.7% 1999) and msp2-PCR (58.7% 1994, 44.8% 1999), whereas real-time PCR prevalence remained higher throughout the 1990s (69.4% 1994, 64.8% 1999). In 2010, parasite prevalence was 17.8% by real-time PCR and 16.3% by msp2-PCR, and estimated to 4.8% by microscopy. Spleen rates in children ages two to nine years decreased earlier than parasite prevalence, from >75 to 42% in the 1980s, to nil during the 1990s. The prevalence of severe and moderate anaemia decreased from 41.1 to 13.1%. No deaths at the time of acute malaria were recorded when the research team lived in the village.ConclusionsA marked decline in malaria transmission was observed over 25 years. The decrease was detected after the arrival of the research team and continued gradually both before and after distribution of bed nets. Spleen rates and microscopy identified early changes when transmission was still intense, whereas real-time PCR was a more sensitive metric when transmission was reduced. The study provides historical data on malaria within a closely monitored rural village and contributes to the understanding of changing epidemiology in sub-Saharan Africa.

【 授权许可】

CC BY   
© Färnert et al.; licensee BioMed Central Ltd. 2014