We applied a novel framework based on network theory and a concept of modularity that estimates congruence between trait-based ( = functional) co-occurrence networks, thus allowing the inference of co-occurrence patterns and the determination of the predominant mechanism of community assembly. The aim was to investigate the relationships between species co-occurrence and trait similarity in flea communities at various scales (compound communities: across regions within a biogeographic realm or across sampling sites within a geographic region; component communities: across sampling sites within a geographic region; and infracommunities: within a sampling site). We found that compound communities within biogeographic realms were assembled via environmental or host-associated filtering. In contrast, functional and spatial/host-associated co-occurrence networks, at the scale of regional compound communities, mostly indicated either stochastic processes or the lack of dominance of any deterministic process. Analyses of congruence between functional and either spatial (for component communities) or host-associated (for infracommunities) co-occurrence networks demonstrated that assembly rules in these communities varied among host species. In component communities, stochastic processes prevailed, whereas environmental filtering was indicated in 4 and limiting similarity/competition in 9 of 31 communities. Limiting similarity/competition processes dominated in infracommunities, followed by stochastic mechanisms. We conclude that assembly processes in parasite communities are scale-dependent, with different mechanisms acting at different scales.

We studied the relationships between functional alpha and beta diversities of fleas and their small mammalian hosts in 4 biogeographic realms (the Afrotropics, the Nearctic, the Neotropics and the Palearctic), considering 3 components of alpha diversity (functional richness, divergence and regularity). We asked whether (a) flea alpha and beta diversities are driven by host alpha and beta diversities; (b) the variation in the off-host environment affects variation in flea alpha and beta diversities; and (c) the pattern of the relationship between flea and host alpha or beta diversities differs between geographic realms. We analysed alpha diversity using modified phylogenetic generalized least squares and beta diversity using modified phylogenetic generalized dissimilarity modelling. In all realms, flea functional richness and regularity increased with an increase in host functional richness and regularity, respectively, whereas flea functional divergence correlated positively with host functional divergence in the Nearctic only. Environmental effects on the components of flea alpha diversity were found only in the Holarctic realms. Host functional beta diversity was invariantly the best predictor of flea functional beta diversity in all realms, whereas the effects of environmental variables on flea functional beta diversity were much weaker and differed between realms. We conclude that flea functional diversity is mostly driven by host functional diversity, whereas the environmental effects on flea functional diversity vary (a) geographically and (b) between components of functional alpha diversity.

Combining the biogeography and phylogenetic patterns of parasite-host associations allows a better understanding of the history of parasite–host interactions, which can be achieved via biogeographic regionalization incorporating phylogenetic information. Recently, the concepts of evoregions (regions where a majority of species evolved from one or several ancestors inhabiting these regions) and evolutionary transition zones (regions of high phylogenetic turnover) have been proposed, coupled with a classification approach for these concepts. We applied this approach to 206 flea species and 265 host species of the Palearctic and aimed to identify evoregions and evolutionary transition zones for both fleas and hosts and to understand whether these evoregions and transition zones match each other. We identified 5 evoregions with 3 transition zones for either fleas or hosts, but neither the positions and boundaries of the flea and host evoregions nor the transition zones coincided. Indications of multiple geographic centres of diversification of the same flea lineages suggested that (a) the common evolutionary history of fleas and hosts was characterized by multiple events other than codiversification and that (b) dispersal played an important role in flea and host assemblies. Barriers to dispersal could be represented by landscape features (deserts and mountain ranges) and/or climate differences.

We investigated phylogenetic patterns in flea assemblages from 80 regions in 6 biogeographic realms and asked whether (a) flea phylogenetic turnover is driven by host phylogenetic turnover, environmental dissimilarity or geographic distance; (b) the relative importance of these drivers differs between realms; and (c) the environmental drivers of flea phylogenetic turnover are similar to those of host phylogenetic turnover. We also asked whether the phylogenetic originality of a flea species correlates with the degree of its host specificity and whether the phylogenetic originality of a host species correlates with the diversity of its flea assemblages. We found that host phylogenetic turnover was the best predictor of flea phylogenetic turnover in all realms, whereas the effect of the environment was weaker. Environmental predictors of flea phylogenetic turnover differed between realms. The importance of spatial distances as a predictor of the phylogenetic dissimilarity between regional assemblages varied between realms. The responses of host turnover differed from those of fleas. In 4 of the 6 realms, geographic distances were substantially better predictors of host phylogenetic turnover than environmental gradients. We also found no general relationship between flea phylogenetic originality and its host specificity in terms of either host species richness or host phylogenetic diversity. We conclude that flea phylogenetic turnover is determined mainly by the phylogenetic turnover of their hosts rather than by environmental gradients. Phylogenetic patterns in fleas are manifested at the level of regional assemblages rather than at the level of individual species.

We used data on the species composition of regional assemblages of fleas and their small mammalian hosts from 6 biogeographic realms and applied a novel method of step-down factor analyses (SDFA) and cluster analyses to identify biogeographic (across the entire globe) and ecological (within a realm across the main terrestrial biomes) clusters of these assemblages. We found that, at the global scale, the clusters of regional assemblage loadings on SDFA axes reflected well the assemblage distribution, according to the biogeographic realms to which they belong. At the global scale, the cluster topology, corresponding to the biogeographic realms, was similar between flea and host assemblages, but the topology of subtrees within realm-specific clusters substantially differed between fleas and hosts. At the scale of biogeographic realms, the distribution of regional flea and host assemblages did not correspond to the predominant biome types. Assemblages with similar loadings on SDFA axes were often situated in different biomes and vice versa. The across-biome, within-realm distributions of flea vs host assemblages suggested weak congruence between these distributions. Our results indicate that dispersal is a predominant mechanism of flea and host community assembly across large regions.

Stenoponia tripectinata tripectinata (Tiraboschi, 1902) is the most prevalent subspecies, within the genus Stenoponia, in the Mediterranean area. This rodent flea is widely distributed throughout southwestern Europe and the North of Africa including Mediterranean islands and the Canary Islands. Nevertheless, from a taxonomical and systematic point, this flea group has been neglected over the years. Therefore, the aim of this study was to carry out a comparative morphometric, phylogenetic, and molecular study of two populations of S. t. tripectinata isolated from rodents collected from different islands from the Canary Archipelago and from Corsica to clarify the taxonomic status of these two isolated populations and to assess the morphological and molecular differentiation between them. For this purpose, we have analyzed several morphological traits and sequenced five molecular markers (EF1-α, ITS2, cox1, cox2, and cytb). We observed slight differences in the overall body size between females of both populations, and two well-defined geographical genetic lineages. This suggests the existence of two cryptic subspecies within S. t. tripectinata corresponding to two different island groups. Furthermore, we bring to light the necessity to provide new and updated morphological, molecular, and phylogenetic data to clarify the taxonomic status of S. tripectinata.

While the desire for systemic repellents is high, ineffective repellents put one at risk of insect-vectored pathogens. Vitamin B1, or thiamine, has been touted as a systemic insect repellent since 1943, and denounced as an ineffective placebo for just as long. This paper presents a scoping review of 104 relevant case reports, research studies, and review articles to trace the evolution of this idea and identify an evidence-based, scientific consensus. Reports of thiamine's systemic repellency are primarily anecdotal and based on uncontrolled trials and/or used bite symptoms as a proxy for reduced biting. Controlled experiments on insect landing and feeding found no evidence of repellency. Of the 49 relevant review papers, 16 insect bite prevention guidelines, and 4 government documents, none after the 1990s claimed thiamine is a repellent. The findings of this review are that thiamine cannot repel arthropods in any dosage or route of administration. Due to limited available evidence, the possibility that thiamine reduces the subjective symptoms of insect bites cannot currently be ruled out. Unfortunately, many medical professionals and travelers today still believe thiamine may be effective despite the evidence stating otherwise. Continued promotion of debunked repellents on the commercial market poses a serious risk in countries with the endemic, mosquito-vectored disease.

We investigated the patterns of phylogenetic and functional (dis)similarity in the species composition of host spectra between co-habitating generalist flea species in regional assemblages from four continents (Europe, Asia, North America and Africa) using a recently developed ordination approach (Double Similarity Principal Component Analysis). From the functional perspective, we considered physiological [body mass and basal metabolic rate (BMR)] and ecological (shelter depth and complexity) host traits. We asked (a) whether host phylogeny, physiology or ecology is the main driver of (dis)similarities between flea host spectra and (b) whether the patterns of phylogenetic and functional (dis)similarity in host spectra vary between flea assemblages from different continents. Phylogenetic similarity between the host spectra was highest in Africa, lowest in North America and moderate in Europe and Asia. In each assemblage, phylogenetic clusters of hosts dominating in the host spectra could be distinguished. The functional similarity between the host spectra of co-occurring fleas was low for shelter structure in all assemblages and much higher for body mass and BMR in three of the four assemblages (except North America). We conclude that host phylogeny and shelter structure are the main drivers of (dis)similarity between the host spectra of co-habitating fleas. However, the effects of these factors on the patterns of (dis)similarity varied across continents.

In the present study, we identified the ectoparasite communities of red foxes in three regions of Poland that encompassed two endemic regions for the occurrence of Dermacentor reticulatus, as well as a region that is free of this tick species (‘gap’ area). Our study sites were selected to enable the role of foxes as hosts for juvenile (nest dwelling) and adult (exophilic) D. reticulatus ticks to be determined, and to assess their contribution to the spread of this important vector of Babesia canis. We compared also ectoparasite communities between adult foxes with those of fox cubs. Finally, we carried out a systematic search for subcutaneous ticks determining their prevalence and abundance. In 2016–2018, 366 adult foxes and 25 live-trapped cubs were examined for ectoparasites. Ectoparasites were identified based on morphological features, PCR amplification and sequencing. The total prevalence of ectoparasites was higher in cubs (68%) than in adults (62.8%). In adults, 15 parasite species were recorded, including four tick species, seven flea species, scabies, and one Anopluran species each in the genera Felicola and Lipoptena. In cubs, six ectoparasite species were found, including Ixodes kaiseri, a species not found in adults. Although Ixodes ricinus and D. reticulatus were the dominant tick species on adult foxes, no D. reticulatus ticks were found on cubs. Subcutaneous ticks were common (38%) and abundant in all areas. Molecular analysis of subcutaneous nodules allowed the identification of 17 I. ricinus and five D. reticulatus. In conclusion, red foxes play a minor role as hosts of D. reticulatus.

To model the colonization of a novel host by fleas, Synosternus cleopatrae and Xenopsylla ramesis, we established experimental lines maintained for 15 generations on a principal or a novel host (either co-occurring with a flea or not). We compared the blood meal size and the energy expended for digestion by fleas from the 15th generation of each line on these hosts between hosts within a line and between lines within a host asking (a) whether fleas adapt to a novel host (increased blood consumption/decreased energy expended for digestion); (b) if yes, whether this adaptation leads to the loss of ability to exploit an original host, and (c) whether the success of adaptation to a novel host depends on its ecological co-occurrence with a flea. The blood consumption and digestion energetics of fleas fed on the principal host differed from those on other hosts. The effect of the principal host on feeding performance differed between fleas, with S. cleopatrae consuming less blood and expending more energy for digestion on the principal than on any other host, whereas the opposite was true for X. ramesis. No changes in feeding performance on a novel host over generations were found. We propose several explanations for the lack of adaptation to a novel host over time. We explain the poor performance of S. cleopatrae on its principal host via its immune response mounting pattern. We argue that the principal host of a parasite is not necessarily the host on which the parasite demonstrates the best performance.

Essential oils (EOs) are considered a new class of ecological products aimed at the control of insects for industrial and domestic use; however, there still is a lack of studies involving the control of fleas. Ctenocephalides felis felis, the most observed parasite in dogs and cats, is associated with several diseases. The aim of this study was to evaluate the in vitro activity, the establishment of LC50 and toxicity of EOs from Alpinia zerumbet (Pers.) B. L. Burtt & R. M. Sm, Cinnamomum spp., Laurus nobilis L., Mentha spicata L., Ocimum gratissimum L. and Cymbopogon nardus (L.) Rendle against immature stages and adults of C. felis felis. Bioassay results suggest that the method of evaluation was able to perform a pre-screening of the activity of several EOs, including the discriminatory evaluation of flea stages by their LC50. Ocimum gratissimum EO was the most effective in the in vitro assays against all flea stages, presenting adulticide (LC50 = 5.85 μg cm−2), ovicidal (LC50 = 1.79 μg cm−2) and larvicidal (LC50 = 1.21 μg cm−2) mortality at low doses. It also presented an excellent profile in a toxicological eukaryotic model. These findings may support studies involving the development of non-toxic products for the control of fleas in dogs and cats.

The β-diversity of fleas parasitic on small mammals in 45 regions of the Palearctic was partitioned into species [species contributions to β-diversity (SCBD)] and site ( = assemblage) contributions [local contributions to β-diversity (LCBD)]. We asked what are the factors affecting SCBD and LCBD and tested whether (a) variation in ecological, morphological, life history and geographic traits of fleas can predict SCBD and (b) variation in flea and host community metrics, off-host environmental factors, host species composition of flea assemblages can predict LCBD. We used spatial variables to describe geographic distribution of flea assemblages with various LCBD values. SCBD significantly increased with an increase in abundance and a decrease in phylogenetic host specificity of a flea as well as with size and latitude of its geographic range, but was not associated with any morphological/life history trait. LCBD of flea assemblages did not depend on either flea or host species richness or environmental predictors, but was significantly affected by compositional uniqueness ( = LCBD) of regional host assemblages and variables describing their species composition. In addition, variation in LCBD was also explained by broad-to-moderate-scale spatial variables. We conclude that SCBD of fleas could be predicted via their ecological and geographic traits, whereas LCBD of their assemblages could be predicted via host composition.

Diseases and host dynamics are linked, but their associations may vary in strength, be time-lagged, and depend on environmental influences. Where a vector is involved in disease transmission, its dynamics are an additional influence, and we often lack a general understanding on how diseases, hosts and vectors interact. We report on the occurrence of six zoonotic arthropod-borne pathogens (Anaplasma, Bartonella, Borrelia, Coxiella, Francisella and Rickettsia) in common voles (Microtus arvalis) throughout a population fluctuation and how their prevalence varies according to host density, seasonality and vector prevalence. We detected Francisella tularensis and four species of Bartonella, but not Anaplasma, Borrelia, Coxiella or Rickettsia. Bartonella taylorii and B. grahamii prevalence increased and decreased with current host (vole and mice) density, respectively, and increased with flea prevalence. Bartonella doshiae prevalence decreased with mice density. These three Bartonella species were also more prevalent during winter. Bartonella rochalimae prevalence varied with current and previous vole density (delayed-density dependence), but not with season. Coinfection with F. tularensis and Bartonella occurred as expected from the respective prevalence of each disease in voles. Our results highlight that simultaneously considering pathogen, vector and host dynamics provide a better understanding of the epidemiological dynamics of zoonoses in farmland rodents.

To understand existence, patterns and mechanisms behind phylogenetic heritability in the geographic range size (GRS) of parasites, we measured phylogenetic signal (PS) in the sizes of both regional (within a region) and continental (within a continent) geographic ranges of fleas in five regions. We asked whether (a) GRS is phylogenetically heritable and (b) the manifestation of PS varies between regions. We also asked whether geographic variation in PS reflects the effects of the environment's spatiotemporal stability (e.g. glaciation disrupting geographic ranges) or is associated with time since divergence (accumulation differences among species over time). Support for the former hypothesis would be indicated by stronger PS in southern than in northern regions, whereas support for the latter hypothesis would be shown by stronger PS in regions with a large proportion of species belonging to the derived lineages than in regions with a large proportion of species belonging to the basal lineages. We detected significant PS in both regional and continental GRSs of fleas from Canada and in continental GRS of fleas from Mongolia. No PS was found in the GRS of fleas from Australia and Southern Africa. Venezuelan fleas demonstrated significant PS in regional GRS only. Local Indicators of Phylogenetic Association detected significant local positive autocorrelations of GRS in some clades even in regions in which PS has not been detected across the entire phylogeny. This was mainly characteristic of younger taxa.

Anaplasmataceae agents comprise obligate intracellular bacteria that can cause disease in humans and animals. Between August 2013 and March 2015, 31 Nasua nasua (coati), 78 Cerdocyon thous (crab-eating fox), seven Leopardus pardalis (ocelot), 110 wild rodents, 30 marsupials, and 42 dogs were sampled in the Pantanal wetland, Brazil. In addition, ectoparasites found parasitizing the animals were collected and identified. The present work aimed to investigate the occurrence of Anaplasmataceae agents in wild mammals, domestic dogs and ectoparasites, by molecular and serological techniques. Overall, 14 (17·9%) C. thous, seven (16·6%) dogs and one (3·2%) N. nasua were seroreactive to Ehrlichia canis. Nine dogs, two C. thous, one N. nasua, eight wild rodents, five marsupials, eight Amblyomma sculptum, four Amblyomma parvum, 13 A. sculptum nymphal pools, two Amblyomma larvae pools and one Polygenis (Polygenis) bohlsi bohlsi flea pool were positive for Ehrlichia spp. closely related to E. canis. Seven N. nasua, two dogs, one C. thous, one L. pardalis, four wild rodents, three marsupials, 15 A. sculptum, two Amblyomma ovale, two A. parvum and one Amblyomma spp. larval pools were positive for Anaplasma spp. closely related to A. phagocytophilum or A. bovis. The present study provided evidence that wild animals from Brazilian Pantanal are exposed to Anaplasmataceae agents.

We revisited the role of dissimilarity of host assemblages in shaping dissimilarity of flea assemblages using a non-linear approach. Generalized dissimilarity models (GDMs) were applied using data from regional surveys of fleas parasitic on small mammals in four biogeographical realms. We compared (1) model fit, (2) the relative effects of host compositional and phylogenetic turnover and geographic distance on flea compositional and phylogenetic turnover, and (3) the rate of flea turnover along gradients of host turnover and geographic distance with those from earlier application of a linear approach. GDMs outperformed linear models in explaining variation in flea species turnover and host dissimilarity was the best predictor of flea dissimilarity, irrespective of scale. The shape of the relationships between flea compositional turnovers along host compositional turnover was similar in all realms, whereas turnover along geographic distance differed among realms. In contrast, the rate of flea phylogenetic turnover along gradients of host phylogenetic turnover differed among realms, whereas flea phylogenetic turnover did not depend on geographic distance in any realm. We demonstrated that a non-linear approach (a) explained spatial variation in parasite community composition better than and (b) revealed patterns that were obscured by earlier linear analyses.

We studied nestedness and its relationships with beta-diversity in flea communities harboured by three closely related rodent species (Rhabdomys pumilio, Rhabdomys intermedius, Rhabdomys dilectus) at two spatial scales (within and among host populations) in South Africa and asked (a) whether variation in species composition of flea communities within and among host populations follows a non-random pattern; if yes, (b) what are the contributions of nestedness and species turnover to dissimilarity (= beta-diversity) among flea communities at the two scales; and (c) do the degree of nestedness and its contribution to beta-diversity differ among host species (social vs solitary) and between scales. We found that nestedness in flea assemblages was more pronounced (a) in social than solitary host species and (b) at lower (among host individuals within populations) than at higher scale (among host populations). We also found that higher degree of nestedness was associated with its higher contribution to beta-diversity. Our findings support earlier ideas that parasite community structure results from the processes of parasite accumulation by hosts rather than from the processes acting within parasite communities.

We tested Szidat's rule (the more primitive the host, the more primitive the parasites it harbours) by analysing the relationships between phylogenetic clade ranks of fleas and their small mammalian hosts in four biogeographic realms (Afrotropics, Neotropics, Nearctic and Palearctic). From the host perspective, we tested the association between host clade rank and the mean clade rank of all fleas collected from this host. From the flea perspective, we tested the relationships between flea clade rank and the mean clade rank of hosts on which this flea was recorded. First, we tested whether the analysis of the relationships between host and flea clade ranks should be controlled for phylogenetic dependence among either host or flea species. Then, we tested for the associations between host and flea clade ranks separately for each realm using either a phylogenetic general least-squares analysis or an ordinary least-squares analysis. In all realms, the mean clade rank of fleas parasitic on a given host increased with an increase of this host's clade rank, and the mean clade rank of hosts recorded on a given flea increased with an increase of this flea's clade rank, suggesting that Szidat's rule, at least to some extent, holds for fleas.

Habitat disturbance often results in alterations in community structure of small mammals. Additionally, the parasites harboured by these small mammals may be impacted by environmental changes or indirectly affected by changes in available hosts. To improve our understanding of this interplay, we examined the patterns of parasitism in small mammal communities from a variety of habitats in forested Uganda. Small mammals were collected from areas experiencing variable habitat disturbance, host density and species richness. The analysis focused on 3 most abundant rodent species, Lophuromys aquilus, Praomys jacksoni and Hylomyscus stella, and a diverse group of parasites they harbour. The impact of various habitat and host community factors on parasite prevalence was examined using linear regression and Spearman's rank-order correlation. We further investigated the parasite communities associated with each individual using correspondence analysis. We determined that, parasite prevalence and richness may be occasionally influenced by community and habitat factors, but taxonomy is a driving force in influencing the parasite community harboured by an individual host. Ultimately, applying general principles across a broad range of disturbance levels and diverse host communities needs to be approached with caution in complex communities.