We are connected: flea–host association networks in the plague outbreak focus in the Rift Valley, northern Tanzania

Context. Plague is a serious health problem in northern Tanzania, with outbreaks since 2008 in two districts located in Rift Valley. There is dearth of knowledge on diversity of small mammal and flea fauna occurring in this plague focus. Knowledge on interactions between fleas and rodent species that harbour the plague bacterium, Yersinia pestis, is important for developing strategies for control and prevention of plague. Aims. This study aims to show how rodents and fleas are associated with each other in the plague focus. Methods. Animals were trapped bimonthly from 2009 to 2012 in different habitats. The fur of animals was brushed to collect fleas, which were identified and quantified. Network analysis methods, randomisation and rarefaction curves were used to show how hosts and fleas are associated. Key results.Thirteen species of rodentswere associatedwith 26 species offleas ofwhichDinopsyllus lypusus, Xenopsylla brasiliensis and X. cheopis are confirmed efficient vectors of Y. pestis. Randomisation and rarefaction curves established that Lophuromys flavopunctatus had significantly higher flea species richness (n= 9) than did all other hosts, whereas Xenopsylla cheopis andDinopsyllus spp. showed greater host species richness than did other species of fleas. There was no significant correlation between host sex andflea abundance (c = 0.8, d.f. = 6,P = 0.371), but significant differences between reproductive states (adults had more fleas than did subadults) were observed, which probably reflected typical positive correlation between size and flea abundance (c = 4.1955, d.f. = 1, P= 0.040). Conclusions. The plague outbreak focus in northern Tanzania has a diverse fauna of rodents and fleas with multiple patterns of association and connectivity. Implications. Existence of diverse populations of rodents associated with a large number of flea species, some of which are efficient plague vectors, increases the potential for persistence and transmission of plague to humans in northern Tanzania. Additional keywords: Karatu, Mbulu, rodents, Yersinia pestis. Received 12 December 2014, accepted 10 May 2015, published online 12 June 2015