Experimental manipulation of food availability and macroparasite prevalence reveal differential effects on space use in wild rodents.

Research Highlight: Mistrick, J., Veitch, J. S. M., Kitchen, S. M., Clague, S., Newman, B. C., Hall, R. J., Budischak, S. A., Forbes, K. M., & Craft, M. E. (2024). Effects of food supplementation and helminth removal on space use and spatial overlap in wild rodent populations. Journal of Animal Ecology. http://doi.org/10.1111/1365-2656.14067. The spread of pathogens has been of long-standing interest, even before dramatic outbreaks of avian influenza and the coronavirus pandemic spiked broad public interest. However, the dynamics of pathogen spread in wild populations are complex, with multiple effects shaping where animals go (their space use), population density and, more fundamentally, the resultant patterns of contacts (direct or indirect) among individuals. Thus, experimental studies exploring the dynamics of contact under different sets of conditions are needed. In the current field study, Mistrick et al. (2024) used a multifactorial experimental design, manipulating food availability and individual pathogen infection state in wild bank voles (Clethrionomys glareolus). They found that while food availability, individual traits and seasonality can affect how far individual voles moved, the degree of overlap between individual voles remained largely the same despite a high variation in population density-which itself was affected by food availability. These results highlight how biotic and abiotic factors can shape patterns of space use and balance the level of spatial overlap through multiple pathways.

Effects of food supplementation and helminth removal on space use and spatial overlap in wild rodent populations.

Animal space use and spatial overlap can have important consequences for population-level processes such as social interactions and pathogen transmission. Identifying how environmental variability and inter-individual variation affect spatial patterns and in turn influence interactions in animal populations is a priority for the study of animal behaviour and disease ecology. Environmental food availability and macroparasite infection are common drivers of variation, but there are few experimental studies investigating how they affect spatial patterns of wildlife. Bank voles (Clethrionomys glareolus) are a tractable study system to investigate spatial patterns of wildlife and are amenable to experimental manipulations. We conducted a replicated, factorial field experiment in which we provided supplementary food and removed helminths in vole populations in natural forest habitat and monitored vole space use and spatial overlap using capture-mark-recapture methods. Using network analysis, we quantified vole space use and spatial overlap. We compared the effects of food supplementation and helminth removal and investigated the impacts of season, sex and reproductive status on space use and spatial overlap. We found that food supplementation decreased vole space use while helminth removal increased space use. Space use also varied by sex, reproductive status and season. Spatial overlap was similar between treatments despite up to threefold differences in population size. By quantifying the spatial effects of food availability and macroparasite infection on wildlife populations, we demonstrate the potential for space use and population density to trade-off and maintain consistent spatial overlap in wildlife populations. This has important implications for spatial processes in wildlife including pathogen transmission.

Histopathological and morphological characterization of Cysticercus fasciolaris isolated from domestic and wild rodents in Morocco.

Cysticercus fasciolaris is a parasitic helminth that usually infects feline and canine mammal hosts. The intermediate hosts (rodents, occasionally lagomorphs, and humans) get infected by the consumption of feed or water contaminated with eggs. Rodents are vectors of disease and reservoirs of various zoonotic parasites. The current survey was aimed at determining endoparasitic helminth infections in rodents in central Morocco. Sampled rodents after specific identification were sacrificed and examined to identify parasitic helminths following ethical guidelines. Parasites were identified using morphological characteristics. A total of 197 specimens of rodents were collected and examined in this study. Ten rodent species were identified morphologically as Rattus rattus, R. norvegicus, Apodemus sylvaticus, Mus musculus, M. spretus, Mastomys erythroleucus, Meriones shawi, M. libycus, Gerbillus campestris, and Lemniscomys barbarus. The parasitological results showed that metacestode of tapeworms was found encysted in the liver, the larval stage of Taenia taeniaeformis develops large multinodular fibrosarcomas which envelope the tapeworm cysts in the liver of the R. rattus and R. norvegicus. Based on morphological data, the metacestode was identified as C. fasciolaris in 23 (23/80) R. rattus 2 (2/8) and R. norvegicus with a prevalence of 11.7 % and 1.0 %, respectively. Rodents are major vectors of human and domestic animal diseases worldwide, and therefore, important parasitic zoonotic agents (C. fasciolaris), which are transmitted by black rats (R. rattus) and brown rats (R. norvegicus), must be considered to prevent the infectivity of humans, domestic animals, and livestock such as cattle, sheep, and rabbits.

Phylogenetic analysis of a novel Hepatozoon species (Hepatozoon sp. SK3) and an additional yet unknown Hepatozoon species (Hepatozoon sp. BV2) besides H. erhardovae in small rodents from Central Europe.

Hepatozoon spp. are tick-borne apicomplexan parasites of terrestrial vertebrates that occur worldwide. Tissue samples from small rodents and their parasitizing fleas were sampled for molecular detection and phylogenetic analysis of Hepatozoon-specific 18S rRNA gene region. After alignment and tree inference the Hepatozoon-sequences retrieved from a yellow-necked mouse (Apodemus flavicollis) placed into a strongly supported single clade demonstrating the presence of a novel species, designated Hepatozoon sp. SK3. The mode of transmission of Hepatozoon sp. SK3 is yet unknown. It is important to note that this isolate may be identical with the previously morphologically described Hepatozoon sylvatici infecting Apodemus spp.; however, no sequences are available for comparison. Furthermore, the previously reported variants Hepatozoon sp. BV1/SK1 and BV2/SK2 were detected in bank voles (Clethrionomys glareolus). It has been suggested that these variants should be identified as Hepatozoon erhardovae leading to the assumption that BV1 and BV2 are paralogous 18S rRNA gene loci of this species. Evidence has also been presented that fleas are vectors of H. erhardovae. In this study, we show with high significance that only the Hepatozoon sp. BV1 variant, but not BV2, infects the studied flea species Ctenophthalmus agyrtes, Ctenophthalmus assimilis, and Megabothris turbidus (p < 0.001). This finding suggests that Hepatozoon sp. BV2 represents an additional species besides H. erhardovae (= Hepatozoon sp. BV1), for which alternative arthropod vectors or non-vectorial modes of transmission remain to be identified. Future studies using alternative molecular markers or genome sequencing are required to demonstrate that BV1/SK1 and BV2/SK2 are different Hepatozoon species.

Molecular characterizations of Cryptosporidium spp. in brown rat (Rattus norvegicus) from an animal feedlot in Xinjiang, China.

Cryptosporidium infection is a common occurrence in rodents worldwide. In this study, 435 wild brown rats were captured from an animal feedlot in Xinjiang, China, with a fecal sample obtained directly from the rectal contents of each rat. The DNA extracted from these fecal samples was analyzed for Cryptosporidium spp. using PCR targeting the SSU rRNA gene. The prevalence of Cryptosporidium infection in brown rats was found to be 5.5% (24 out of 435). Interestingly, the infection rates varied among different animal enclosures, with rates of 0% in the chicken coop (0/51), cowshed (0/3), and varying rates in other areas including the sheepfold (6.1%, 6/98), the pigsty (7.6%, 10/132), the dovecote (7.0%, 5/71), and outdoor environments (3.8%, 3/80). The study identified three species and one genotype of Cryptosporidium, namely C. occultus (n = 10), C. parvum (n = 4), C. ditrichi (n = 1), and Cryptosporidium rat genotype IV (n = 9). Additionally, two of the C. parvum isolates were successfully subtyped as IIdA19G1 (n = 2) at the gp60 gene. These results offer valuable insights into the prevalence and genetic diversity of Cryptosporidium in brown rats within the region.

Parasite infestation patterns differ between ticks and chigger mites on two rodent host species in Taiwan.

Parasites are typically concentrated on a few host individuals, and identifying the mechanisms underlying aggregated distribution can facilitate a more targeted control of parasites. We investigated the infestation patterns of hard ticks and chigger mites on two rodent species, the striped field mouse, Apodemus agrarius, and the lesser ricefield rat, Rattus losea, in Taiwan. We also explored abiotic and biotic factors that were important in explaining variation in the abundance of ticks and chiggers on rodent hosts. Ticks were more aggregated than chiggers on both rodent species. Factors important for the variation in parasitic loads, especially biotic factors, largely differed between ticks and chiggers. Variation partitioning analyses revealed that a larger proportion of variation in chiggers than in ticks can be explained, especially by abiotic factors. If, as proposed, the higher number of parasites in males is due to a larger range area or immunity being suppressed by testosterone, when A. agrarius males host more ticks, they are expected to also host more chiggers, given that chiggers adopt a similar host finding approach to that of ticks. Instead, the similar abundance of chiggers in male and female A. agrarius implies that a large home range or suppressed immunity does not predispose males to inevitably host more parasites. More variations were explained by abiotic than biotic factors, suggesting that controlling practices are more likely to be successful by focusing on factors related to the environment instead of host traits. Our study indicated that the extent of parasitism is rarely determined by a sole factor, but is an outcome of complex interactions among animal physiology, animal behavior, characteristics of parasites, and the environments.

Host specificity of flea parasites of mammals from the Andean Biogeographic Region.

Host specificity of fleas affects their biodiversity that plays a major role in determining the potential transmission routes by pathogens through vertebrate hosts, including humans. In the Biogeographic Andean region, numerous systematic and ecological studies have been conducted, revealing a high diversity of flea taxa of mammals and the presence of pathogenic organisms transmitted by fleas; however, the degree of preference with which each flea species associates with a mammal host remains poorly understood in this region. Herein, host specificity in mammal fleas from the Andean region was analysed. We employed the number of host species for each flea species and the index of host specificity STD *. Following the literature, 144 species and 13 subspecies of fleas (31 genera and 10 families) have been described in the Andean biogeographic region; 76 taxa are endemic to this region. To carry out the analyses of host specificity, we considered 1759 records of fleas collected from 124 species and 59 genera of wild and domestic mammals, mostly rodent species (85.9%). Our results indicate that typical Andean fleas are genus or family host specific (mostly STD * less than 3.0). More diverse mammal hosts are parasitized by more diverse flea genera and families and these hosts are phylogenetically related. Otherwise, these hosts are associated with different flea lineages, suggesting the interaction of ecological and evolutionary mechanisms (host-switching, ecological adaptations and co-evolutionary alternation). The fields of disease ecology and One Health are considering the host specificity of arthropod vectors as an important point to understand the mechanisms of emergence and re-emergence of diseases. Our results allow us to estimate the risk of diseases involving fleas in the Andean region.

Gastrointestinal parasite assemblages from the wild rodent capybara (Hydrochoerus hydrochaeris) inhabiting a natural protected area from Argentina.

Knowledge about parasitic diseases of wildlife will help us to understand the dynamics of parasites and their effects on host populations. The capybara (Hydrochoerus hydrochaeris) is the largest living rodent in the world, and its distribution is associated with the presence of tropical and subtropical wetlands in South America. The Los Padres Lake Integral Reserve (LPLIR) is an important conservation zone in the pampean region of Argentina. One of the emblematic species found within the reserve is the capybara. The objective of this study was to determine the gastrointestinal parasites present in wild capybaras of the LPLIR and to compare different coprological methodologies. Free-ranging capybara fresh feces from 57 individuals were randomly collected from the area of LPLIR in the summer of 2022. Three different techniques were applied: spontaneous sedimentation technique (SS), INTA modified McMaster technique (MM), and Mini-FLOTAC (MF) technique. Fifty-six samples from all samples analysed (56/57, 98%) were found to be positive for gastrointestinal parasites. Two species of Strongylida, Protozoophaga obesa, Echinocoleus hydrochaeris, one unidentified nematode, one unidentified spirurid, and at least two morphotypes of Eimeria spp. oocysts were recorded. There were found significant differences in the proportion of positive samples and in richness by technique, but no significant differences were found in parasite counting. In conclusion, the choice of methodology depends on the specific objectives of the study. This is the first parasitological study of capybaras from the LPLIR and represents an exploration of parasite communities present in these wild rodents at their southernmost distribution.

Parasitic nematodes of the genus Syphacia Seurat, 1916 infecting Cricetidae in the British Isles: the enigmatic status of Syphacia nigeriana.

Oxyurid nematodes (Syphacia spp.) from bank (Myodes glareolus) and field/common (Microtus spp.) voles, from disparate geographical sites in the British Isles, were examined morphologically and genetically. The genetic signatures of 118 new isolates are provided, based primarily on the rDNA internal transcribed spacers (ITS1-5.8S-ITS2) region and for representative isolates also on the small subunit 18S rDNA region and cytochrome c oxidase subunit 1 (cox-1) gene locus. Genetic data on worms recovered from Microtus spp. from the European mainland and from other rodent genera from the Palaearctic, North America and West Africa are also included. We test historical hypotheses indicating that S. nigeriana is a generalist species, infecting a range of different rodent genera. Our results establish that S. nigeriana is a parasite of both bank and field voles in the British Isles. An identical genotype was also recorded from Hubert's multimammate mouse (Mastomys huberti) from Senegal, but Mastomys spp. from West Africa were additionally parasitized by a related, although genetically distinct Syphacia species. We found no evidence for S. petrusewiczi in voles from the British Isles but isolates from Russia and North America were genetically distinct and formed their own separate deep branch in maximum likelihood molecular phylogenetic trees.

Update of Dicrocoeliidae (Digenea) parasitizing rodents from the Americas with a description of a new Platynosomoides species from Argentina.

Digeneans are common parasites of small mammals. Dicrocoeliidae is a family with a cosmopolitan distribution, with 18 genera previously recorded from mammals in the Americas, six of them parasitizing rodents in Argentina. In this study, an updated compilation is provided of Dicrocoeliidae from rodents in the Americas. Also, a new Platynosomoides species is described parasitizing the cricetid rodent Akodon montensis of the Atlantic Forest in Argentina. Digital repositories were used to search for Dicrocoeliidae from rodents in the Americas. Rodents were collected in four localities of the Atlantic Forest, Argentina. Digeneans were removed from the rodent's bile duct, and conventional studies were used for the morphological description. A total of 15 Dicrocoeliidae species were found parasitizing 18 rodent species from eight countries in the Americas. The new species of Platynosomoides from Akodon montensis differs from the other two species of genus by the size of body, testes, ovary, cecum length and position and length of the vitelline bands. Dicrocoeliidae show growing diversity, and the compilation of species in a rodent host base allows a clearer comparison and identification of new taxa in the future.

Variability of Calodium hepaticum eggs from sigmodontine host species through geometric morphometric analysis.

Calodium hepaticum is a zoonotic nematode with a worldwide distribution. Although the host range of C. hepaticum includes a wide spectrum of mammals (including humans), this parasite is predominantly associated with the families Muridae and Cricetidae. Several Sigmodontinae species from Argentina were found to be infected by C. hepaticum, with a high prevalence in Akodon azarae. The present study focuses on C. hepaticum eggs from natural infection of three species of sigmodontine rodents from Argentina. Eggs were genetically characterized (intergenic 18S rRNA region). The objectives of this work are: (i) to propose a new analytical methodology; and (ii) to morphologically characterize C. hepaticum eggs, from three Sigmodontinae species (A. azarae, Calomys callidus and Oligoryzomys flavescens). Analyses were made by the Computer Image Analysis System based on the new standardized measurements and geometric morphometric tools. The resulting factor maps clearly illustrate global size differences in the parasite eggs from the three Sigmodontinae species analysed. The degree of similarity between egg populations was assessed through pairwise Mahalanobis distances, showing that the largest distances were detected between parasite eggs from C. callidus and O. flavescens. Herein, the phenotypical plasticity of C. hepaticum eggs is shown. Significant positive correlations were obtained between each egg parasite principal component 1 and rodent corporal characteristics: weight; liver weight; rodent length; and rodent body condition. The usefulness of the geometric morphometric analysis in studies of the relationship between C. hepaticum and its host must be highlighted. The high prevalence observed in A. azarae, associated with the wide size range of the parasite eggs evidenced by principal component analysis, suggests A. azarae to be the Sigmodontinae host species that plays the most important role as reservoir host for C. hepaticum in the New World.

Two new genera and species of Nippostrongylinae (Nematoda: Heligmonellidae) parasites of two murine rodents (Muridae): from the Moluccas, Indonesia and Papua New Guinea with a comment on a pentastomatid.

Bisastrongylus multiovorum gen. nov., sp. nov. (Nematoda: Heligmonellidae: Nippostrongylinae) is described from a murid, Melomys obiensis, from the Moluccas, Indonesia. The new genus differs from all other Nippostrongylinae genera in having a synlophe of 12 unequal ridges with a type A carene, the dorsal ridge 1 being larger than the ventral ridge 1'. Pentastomid larvae, an acanthocephalan, Plagiorhynchus sp., and the nematodes Rictularia sp., a spirurid and the nippostrongylin Soricstrongylus obreensis gen. nov., sp. nov. were collected from the murid Pseudohydromys murinus from Central Province, Papua New Guinea. The new genus is distinguished by a combination of characters including a synlophe of 11-13 ridges at mid body, left ventral ridges larger and a sub frontal axis of orientation. The assemblage of P. murinus is discussed and a re-evaluation of nippostrongylin Odilia sp., previously reported from P. murinus indicates that the specimens were likely a Parasabanema sp.

Beta and phylogenetic diversities tell complementary stories about ecological networks biogeography.

The beta-diversity of interactions between communities does not necessarily correspond to the differences related to their species composition because interactions show greater variability than species co-occurrence. Additionally, the structure of species interaction networks can itself vary over spatial gradients, thereby adding constraints on the dissimilarity of communities in space. We used published data on the parasitism interaction between fleas and small mammals in 51 regions of the Palearctic to investigate how beta-diversity of networks and phylogenetic diversity are related. The networks could be separated in groups based on the metrics that best described the differences between them, and these groups were also geographically structured. We also found that each network beta-diversity index relates in a particular way with phylogenetically community dissimilarity, reinforcing that some of these indexes have a strong phylogenetic component. Our results clarify important aspects of the biogeography of hosts and parasites communities in Eurasia, while suggesting that networks beta-diversity and phylogenetic dissimilarity interact with the environment in different ways.

Angiostrongylus cantonensis infection of non-native rats in Mount Makiling Forest Reserve, the Philippines.

A number of studies had been conducted on rat species diversity in the Philippines, however, there is a dearth of information on the extent of Angiostrongylus spp. infection in various ecological niches. Collection of non-native rat samples occurred in various sampling sites categorized as residential, agricultural and agro-forest in Philippine Mount Makiling Forest Reserve (MMFR) and its adjacent areas . Three species of non-native rats were captured including Rattus tanezumi, Rattus norvegicus and Rattus exulans. Of the total 90 non-native rats collected, 24.4% were found infected with Angiostrongylus cantonensis. Statistical analysis showed significant difference among rat species with highest prevalence observed in R. exulans (42.9%) followed by R. tanezumi (29.8%) and R. norvegicus (7.7%) (P = 0.047). Angiostrongylus cantonensis infection was significantly higher in adults (29.4%) than in juvenile rats (9.1%) (P = 0.050). However, results showed no significant difference in A. cantonensis infection between male (43.3%) and female (18.3%) rats and between wet (31.6%) and dry seasons (19.2%) (P > 0.05). Moreover, this study also revealed that rats from agricultural and agro-forest areas showed significantly higher prevalence than residential areas. With urbanization and the everchanging landscape of MMFR watersheds and buffer zones, zoonotic transmission can pose health threats to the local people.

Variation in Angiostrongylus cantonensis infection in definitive and intermediate hosts in Hawaii, a global hotspot of rat lungworm disease.

Angiostrongylus cantonensis (rat lungworm) is a tropical and subtropical parasitic nematode, with infections in humans causing angiostrongyliasis (rat lungworm disease), characterized by eosinophilic meningitis. Hawaii has been identified as a global hotspot of infection, with recent reports of high infection rates in humans, as well as rat definitive and snail intermediate hosts. This study investigated variation in A. cantonensis infection, both prevalence and intensity, in wild populations of two species of rats (Rattus exulans and R. rattus) and one species of snail (Parmarion martensi). An overall infection prevalence of 86.2% was observed in P. martensi and 63.8% in rats, with R. exulans (77.4%) greater than R. rattus (47.6%). We found infections to vary with environmental and host-related factors. Body mass was a strong predictor of infection in all three species, with different patterns seen between sexes and species of rats. Infection prevalence and intensity for R. exulans were high in May 2018 and again in February 2019, but generally lower and more variable during the intervening months. Information on sources of variability of infection in wild host populations will be a crucial component in predicting the effectiveness of future disease surveillance or targeted management strategies.

Alternative pathways in Angiostrongylus cantonensis (Metastrongyloidea: Angiostrongylidae) transmission.

In order to elucidate the infection pathways of third stage larvae (L3) of Angiostrongylus cantonensis, we performed experiments to assess: (i) the shedding of L3 from two species of experimental veronicellid slugs drowned in water and the ratio of emerged larvae, (ii) the transmission of viable L3 from drowned terrestrial gastropods to aquatic snails, and (iii) the transmission of viable L3 between terrestrial snails. Molluscs were experimentally infected by first stage larvae (L1) of A. cantonensis. Significantly more L3 larvae were released from Veronicella cubensis than from Veronicella sloanei. Numerous L3 were observed in the muscular foot, and also in the connective tissue between internal organs. Experimental exposure of P. maculata to L3 of A. cantonensis liberated from other gastropod species led to their infection and the infectivity of larvae after intermediesis was demonstrated by infection of laboratory rats (Rattus norvegicus). The transmission of L3 was observed in three out of four experiment replications and L3 were retrieved from 6 out of 24 Subulina octona snails. The infected synanthropic molluscs represent a key component in the epidemiology of human infections by A. cantonensis. Escape of L3 larvae from bodies of dead snails or slugs and their ability to infect further gastropod hosts (intermediesis) represents a public health risk. Thus, control of molluscs living in peri-domestic environment is an essential part of prevention of human infections.

Angiostrongylus cantonensis (rat lungworm) in Florida, USA: current status.

Angiostrongylus cantonensis has been found in Florida, USA, from the panhandle in the north to Miami and surrounding areas in the southern parts of the state, in both definitive and intermediate hosts in a limited studies completed in 2015. Additional studies have identified this parasite in a variety of intermediate hosts, both native and non-native gastropod species, with new host species recorded. Many areas in Florida with higher A. cantonensis prevalence were those with a high human population density, which suggests it is a matter of time before human infections occur in Florida. Case reports in the state currently involve non-human primates and include a gibbon and orangutan in Miami. Here, we report the current status of A. cantonensis in the state, as well as the infection in a capuchin monkey and presumptive infection in a red ruffed lemur in Gainesville, Florida.

Functional traits shape small mammal-helminth network: patterns and processes in species interactions.

Understanding the role of species traits in mediating ecological interactions and shaping community structure is a key question in ecology. In this sense, parasite population parameters allow us to estimate the functional importance of traits in shaping the strength of interactions among hosts and parasites in a network. The aim of this study was to survey and analyse the small mammal-helminth network in a forest reserve of the Brazilian Atlantic Forest in order to understand (i) how functional traits (type of parasite life cycle, site of infection in their host, host and parasite body length, host diet, host locomotor habit and host activity period) and abundance influence host­parasite interactions, (ii) whether these traits explain species roles, and (iii) if this relationship is consistent across different parasite population parameters (presence and absence, mean abundance and prevalence). Networks were modular and their structural patterns did not vary among the population parameters. Functional traits and abundance shaped the interactions observed between parasites and hosts. Host species abundance, host diet and locomotor habit affected their centrality and/or vulnerability to parasites. For helminths, infection niche was the main trait determining their central roles in the networks.

Transmission networks and ectoparasite mite burdens in Oecomys paricola (Rodentia: Cricetidae).

The host contact network structure results from the movement and behaviour of hosts (e.g. degree of sociability; vagility and greater or lesser fidelity of shelters), which can generate heterogeneity in the transmission of parasites and influence the parasitic burden of individual hosts. In the current study, we tested the hypothesis that the burdens of Gigantolaelaps oudemansi mites are related to the characteristics of the transmission networks of individuals of Oecomys paricola, a solitary rodent. The study was carried out in a savannah habitat in north-eastern Brazil. In the dry season, the rodent network presented sub-groups of rodent individuals interacting with each other, whereas in the wet season, no modules were formed in the network. Mite burden was positively related to the number of connections that an individual host had with other host individuals in the dry season. The pairwise absolute difference between the mean mite burdens among individual rodents was negatively correlated with the similarities of node interactions. No relationships were observed during the wet season. There was a higher heterogeneity of mite burden among hosts in the dry season compare to that in the wet season. In solitary species, spatial organization may show seasonal variation, causing a change in the opportunities of host contacts, thereby influencing the transmission and dispersion of their ectoparasite burdens.

Spatial and temporal variation of compositional, functional, and phylogenetic diversity in ectoparasite infracommunities harboured by small mammals.

We studied patterns of compositional, functional, and phylogenetic α- and ß-diversity in flea and gamasid mite infracommunities of small Siberian mammals, taking into account host-associated (species) and environmental (biome or sampling period) factors. We asked: (a) How do these factors and their interactions affect infracommunity diversity? (b) Does infracommunity composition, in terms of species, traits, and phylogenetic lineages, deviate from random? (c) Are species, traits, and phylogenetic lineages in infracommunities clustered or overdispersed?, and (d) Do patterns of diversity differ between the three diversity facets and/or the two ectoparasite taxa? We found that the α-diversity of infracommunities was strongly affected by host species, biome, and sampling period. The highest proportion of infracommunity diversity in both taxa was associated with the interaction between either host species and biome or host species and sampling period. Infracommunities of both taxa within, as well as between, host species, biomes, and sampling periods were characterized by the clustering of species, traits and lineages. The patterns of the effects of host species, biome, and sampling period on infracommunity diversity were congruent among the three diversity facets in both fleas and mites. We conclude that the assembly patterns in ectoparasite infracommunities mirror those characteristics of component and compound communities.