Seasonal and habitat dependence of fleas parasitic on small mammals in Tanzania

Abstract

We investigated host and flea species composition across different habitats during dry and rainy seasons in the Western Usambara Mountains in Tanzania. During both seasons, similarity in flea species composition increased with an increase in the similarity in host species composition. Nevertheless, between-season within-habitat as well as within-season between-habitat similarity in host species composition was higher than similarity in flea species composition. Ordination of habitats according to their host and flea species composition demonstrated that the pattern of between-habitat similarity in both host and flea species composition varied seasonally. Despite the relatively rich mammal and flea fauna of the study region, the major contribution to variation in species composition between seasons and among habitats was due to a few species only. Flea assemblages on Lophuromys kilonzoi Verheyen et al., 2007 and Praomys delectorum Thomas, 1910 in different habitats were equally similar in either season. In contrast, flea assemblages on Mastomys natalensis (Smith, 1834) occurring in different habitats were more similar in the dry than in the rainy season, whereas the opposite was the case for fleas on Grammomys sp. In different hosts, the main differences in species composition of flea assemblages between seasons as well as among habitats were due to different flea species. Although our results support the earlier idea that parasite species composition is determined by both host species composition and habitat properties, the former appears to explain variance in flea species composition between localities in the tropics better than between localities in temperate and arid zones.

Effects of Land Use on Plague (Yersinia pestis) Activity in Rodents in Tanzania

“…Such patterns are consistent with observations made in other contexts. 26,53 Rodent species other than M. natalensis also exhibited strong affinities for particular land-use types. However, all five rodent species captured in agricultural sites were also detected in conserved sites.…”

“…However vector competency of many of the other flea species has not been studied. 26 Further research on vector competence of each species, as well as their propensity to bite humans, is necessary to fully evaluate the importance of the observed changes in flea community composition on transmission risk. 58 These land-use-induced shifts in rodent community diversity and abundance had a strong effect on plague activity in our study region.…”

“…64,65 Aggregate rodent abundance was not related to predicted abundance of seropositive rodents, similar to other studies in East Africa that failed to detect differences in rodent abundance between villages with or without a history of plague. 26,66 On the basis of the biodiversity patterns exhibited in conserved versus agricultural lands, the dilution effect hypothesis would predict that there should be a reduced disease risk in conserved land. Our data indicate that the relationship between diversity (at the level of rodents) and plague risk (as measured using PAI) in this context depends entirely on the measure of biodiversity used: a strong negative relationship was observed using Simpson diversity index, the negative relationship approached significance but did not meet the threshold using Shannon diversity index, and no pattern observed when using Chao estimates of species richness.…”

“…4,23,24 Research on the eco-epidemiology of plague in East Africa has given relatively little direct attention to the role of land-use change in disease transmission, and has focused instead on the roles of factors such as climate, context, large mammal presence, and host abundance. 1,[25][26][27][28][29][30][31][32] One of the most common types of landscape change underway in East Africa, and elsewhere in the global tropics, is the conversion of wildlands to agricultural uses. [33][34][35][36] Cultivation in a variety of regions of East Africa has expanded by more than 70% in the last several decades.…”

Contribution of land use to rodent flea load distribution in the plague endemic area of Lushoto District, Tanzania

“…Some of these studies include those on persistence and continued outbreaks of plague (Kilonzo et al, 1997), patterns and spatial distribution of plague (Kamugisha et al, 2007), ecology and status of potential hosts and vectors (Laudisoit et al, 2007(Laudisoit et al, , 2009bLaudisoit, 2009). Other studies focused on the influence of rainfall patterns on plague occurrence (Debien et al, 2010) and variation of flea abundance within and among habitat types (Laudisoit et al, 2009a). Hubeau (2010) found plague occurrence to be closely related to activity spaces for a number of land uses such as fetching water and collecting firewood.…”