The remerging nature of plague requires detailed understanding of the plague flea vectors and small mammal reservoir interactions. Therefore, this study is aimed at assessing flea vector composition, diversity, prevalence, abundance, and phylogeny in selected villages of Lushoto, Mbulu, and Morogoro Rural districts in Tanzania. Small mammals were captured from households and different habitats, and flea ectoparasites were collected, processed, and identified morphologically. Furthermore, seven specimens of the most collected flea species Ctenophthalmu s sp. and Xenopsylla cheopis were submitted for advanced molecular identification and phylogenetic relatedness. The prevalence between predictors such as habitat type, host species, host sex, and locality was compared using chi‐square tests, and also, generalized linear models (GLMs) were used to check the variation between flea abundance and different predictors. A total of 302 small mammals were captured with Mastomys natalensis ( n = 163, 54.0%), Rattus rattus ( n = 41, 13.6%), and Crocidura spp. ( n = 31, 10.3%) dominating the total capture. The collected fleas belonged to nine species, and the most prevalent and abundant species were Ctenophthalmus spp. ( n = 84, 31.0%), Pulex irritans ( n = 82, 30.3%), Dinopsylla lypusus ( n = 78, 28.8%), and Nosopsyllus incisus ( n = 11, 4.1%) from rodents, and more so on males than females. The highest flea diversity was in crop fields ( H ^′ = 1.05) followed by near‐natural forests ( H ^′ = 1.03) and fallow land ( H ^′ = 0.7). Phylogenetic analysis of ITS1 sequences for Ctenophthalmus sp. and Xenopsylla cheopis from Lushoto and Mbulu districts showed strong nucleotide identity. These findings highlight the need for continuous flea and rodent surveillance to mitigate potential plague outbreaks and protect public health in endemic areas.

Fleas are important vectors of numerous pathogens, including bacteria, viruses, helminths and protozoa, and their abundance on small mammals may be influenced by various biotic and abiotic factors. This study investigated the associations between gastrointestinal helminth infections, selected haematological parameters and flea abundance in small mammals from three selected districts of Tanzania. Two wards and two villages within each district were purposively selected for sampling in Mbulu, Lushoto and Morogoro District Council. Small mammals were captured from households, fallow lands, crop fields, plantation forests and bush habitats and identified to species or genus level using morphological keys. Fleas, blood samples and gastrointestinal tracts were collected to determine flea infestation, gastrointestinal helminth infections, packed cell volume (PCV) and haemoglobin concentration (Hb). Associations between gastrointestinal helminths, haematological parameters and flea abundance were assessed using generalised linear mixed models. A total of 302 rodents and shrews were captured, with Mastomys natalensis (54.4%, n = 163), Rattus rattus (13.6%, n = 41) and Crocidura spp. (10.3%, n = 31) being the most abundant hosts. Overall gastrointestinal helminth prevalence was 71.2% (95% CI: 65.7–76.2), with Trichuris spp. (33.3%, n = 100), Hymenolepis diminuta (29.1%, n = 88), Angiostrongylus spp. (19.9%, n = 60) and Hymenolepis nana (15.2%, n = 46) being the most prevalent helminths. A total of 271 fleas were collected, predominantly Ctenophthalmus spp. (31.0%, n = 84), Pulex irritans (30.3%, n = 82), Dinopsyllus lypusus (28.8%, n = 78) and Nosopsyllus incisus (4.1%, n = 11). Overall gastrointestinal helminth prevalence was significantly associated with total flea abundance ( p < 0.05), whereas PCV and Hb showed no significant associations ( p > 0.05). These findings suggest that coinfections involving gastrointestinal helminths and fleas are common in small mammals and that helminth infections may influence flea abundance. Understanding these host–parasite interactions may improve our understanding of pathogen transmission dynamics and inform surveillance strategies for zoonotic diseases in Tanzania.