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Co-invasion, characterized by the simultaneous introduction of hosts and parasites with the latter establishing themselves in native hosts, is a phenomenon of ecological concern. Rattus rattus, a notorious invasive species, has driven the extinction and displacement of numerous avian and mammalian species and serves as a key vector for diseases affecting both humans and wildlife. Among the parasites hosted by R. rattus are fleas, which exhibit obligate parasitic behaviour, a generalist nature and high prevalence, increasing the likelihood of flea invasion. Simultaneously, invasive species can serve as hosts for native parasites, leading to potential amplification or dilution of parasite populations in the environment. In Chile, R. rattus has been present since the 17th century because of the arrival of the Spanish colonizers through the ports and has spread throughout urban, rural and wild Chilean territories. This study aims to evaluate whether co-invasion of native fleas of invasive rats occurs on native rodents in Chile and to determine whether black rats have acquired flea native to Chile during their invasion. For this, we captured 1132 rodents from 26 localities (20° S-53° S). Rattus rattus was found coexisting with 11 native rodent species and two species of introduced rodents. Among the native rodents, Abrothrix olivacea and Oligoryzomys longicaudatus exhibited more extensive sympatry with R. rattus. We identified 14 flea species associated with R. rattus, of which only three were native to rats: Xenopsylla cheopis, Leptopsylla segnis and Nosopsyllus fasciatus. These three species presented a higher parasite load in black rats compared to native fleas. Leptopsylla segnis and N. fasciatus were also found associated with native rodent species that cohabit with R. rattus. The remaining species associated with R. rattus were fleas of native rodents, although they were less abundant compared to those associated with native rodents, except for Neotyphloceras pardinasi and Sphinctopsylla ares. Although there has been evidence of flea transmission from rats to native species, the prevalence and abundance were relatively low. Therefore, it cannot be definitively concluded that these fleas have established themselves in native rodent populations, and hence, they cannot be classified as invasive fleas. This study underscores R. rattus' adaptability to diverse environmental and geographical conditions in Chile, including its capacity to acquire fleas from native rodents. This aspect has critical implications for public health, potentially facilitating the spread of pathogens across various habitats where these rats are found.

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En el presente estudio se informa sobre los parásitos encontrados en un venado de cola blanca, Odocoileus virginianus peruvianus, capturado en el bosque seco del distrito de Paccha, provincia de Chota, departamento de Cajamarca. El Servicio Nacional Forestal y de Fauna Silvestre recuperó los parásitos de un espécimen macho adulto y las remitió al Centro de Investigación en Medicina Tropical de la Universidad Nacional de Cajamarca para la identificación taxonómica de helmintos y artrópodos, y análisis coproparasitológico. Se identificaron dos metacéstodos correspondientes a Cysticercus tenuicollis. En los análisis coproparasitológicos cualitativos se hallaron huevos de Nematodirus spp. en una carga de 10 por gramo de heces (h.p.g.) y 40 h.p.g. tipo Strongílidos que no pudieron diferenciarse por la baja carga en el coprocultivo. No se detectaron huevos de trematodos en la sedimentación. De ectoparásitos, se identificaron ocho garrapatas duras Rhipicephalus (Boophilus) microplus y cinco piojos chupadores Solenopotes binipilosus. Varios de los ejemplares fueron depositados en el Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos, Lima. Los hallazgos representan el primer reporte formal de la garrapata común del ganado en esta subespecie de cérvido. Además, se registra por primera vez la presencia del piojo Solenopotes binipilosus en territorio peruano.

In the present study, findings regarding parasites discovered in a white-tailed deer, Odocoileus virginianus peruvianus, captured in the dry forest of the Paccha district, Chota province, Cajamarca department, are reported. The Servicio Nacional Forestal y de Fauna Silvestre recovered parasites from an adult male specimen and forwarded them to the Tropical Medicine Research Center at the Universidad Nacional de Cajamarca for taxonomic identification of helminths and arthropods, as well as coproparasitological analysis. Two metacestodes corresponding to Cysticercus tenuicollis were identified. Qualitative coproparasitological analyses revealed Nematodirus spp. eggs at a concentration of 10 eggs per gram of feces (EPG) and 40 EPG of Strongylid type that could not be differentiated due to low counts in the coproculture. No trematode eggs were detected in the sedimentation. Among ectoparasites, eight hard ticks Rhipicephalus (Boophilus) microplus and five sucking lice Solenopotes binipilosus were identified. Several specimens were deposited in the Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos, Lima. These findings represent the first formal report of the common cattle tick in this subspecies of cervid. Additionally, the presence of the Solenopotes binipilosus louse in Peruvian territory is reported for the first time.

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Parasites are integral members of the global biodiversity. They are useful indicators of environmental stress, food web structure and diversity. Ectoparasites have the potential to transmit vector-borne diseases of public health and veterinary importance and to play an important role in the regulation and evolution of host populations. The interlinkages between hosts, parasites and the environment are complex and challenging to study, leading to controversial results. Most previous studies have been focused on one or two parasite groups, while hosts are often co-infected by different taxa. The present study aims to assess the influence of environmental and host traits on the entire ectoparasite community composition of the rodent Akodon azarae. A total of 278 rodents were examined and mites (Mesostigmata), lice (Phthiraptera), ticks (Ixodida) and fleas (Siphonaptera) were determined. A multi-correspondence analysis was performed in order to analyze interactions within the ectoparasite community and the influence of environmental and host variables on this assembly. We found that environmental variables have a stronger influence on the composition of the ectoparasite community of A. azarae than the host variables analyzed. Minimum temperature was the most influential variable among the studied. In addition, we found evidence of agonistic and antagonistic interactions between ticks and mites, lice and fleas. The present study supports the hypothesis that minimum temperature plays a major role in the dynamics that shape the ectoparasite community of A. azarae, probably through both direct and indirect processes. This finding becomes particularly relevant in a climate change scenario.

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Laelaps mazzai Fonseca, 1939 (Mesostigmata, Laelapidae) parasitizes several species of the widespread South American rodent genus Calomys Waterhouse, 1837. Morphological variation has been noticed within this laelapid but has yet to be analyzed. Since several other species of laelapids that initially were considered generalists have resulted in host-specific species, after further analyses, herein we explored, through morphology and genetics, the variation of this parasite across six species of Calomys, trying to establish if it constitutes a polymorphic species or a complex of cryptic host specific-species. An integrative approach was applied, including principal component and discriminant analyses of females and males and DNA sequences (nuclear region ITS and the COI gene). The obtained results indicate that female mites tend to differentiate only the sizes of their dorsal shield among host species but with extensive overlapping. At the same time the males lack metrical differentiation, and the genetic evidence failed to resolve specific-species clades. We conclude that L. mazzai is a single widespread mite with little genetic and phenotypic differentiation.

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We applied a step-down factor analysis (SDFA) and multi-site generalised dissimilarity modelling (MS-GDM) to local flea communities harboured by small mammals (i.e., collected at small sampling sites over a short time period) in two South American regions (Patagonia and the Northwestern Argentina) with the aim of understanding whether these communities were assembled via niche-based or dispersal-based processes. The SDFA allows us to determine whether clusters of flea assemblages across different types of climates, vegetation and soils can be distinguished (suggesting niche-based assembly). MS-GDM allows us to determine whether a substantial proportion of the variation in flea species turnover is explained by specific climate-associated, vegetation-associated and soil-associated variables (indicating niche-based assembly) or host turnover (indicating dispersal-based assembly). Mapping of assemblages on climate, vegetation and soil maps, according to their loadings on axis 1 or axis 2 of the SDFA, did not provide clear-cut results. Clusters of similar loadings could be recognized within some, but not other, climate, vegetation and soil types. However, MS-GDM demonstrated that the effect of environmental variables (especially air temperature) on flea compositional turnover was much stronger than that of host turnover, indicating the predominance of niche-based processes in local community assembly. A comparison of our results with those on the mechanisms that drive species assembly in regional communities allows us to conclude that local and regional communities result from the joint action of niche-based and dispersal-based processes, with the former more important at a smaller spatial scale and the latter at a larger spatial scale.

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The haematophagous mite Ornithonyssus sylviarum may cause important economic losses in commercial poultry farms whilst also potentially affecting the health of farm workers. The dynamics of this ectoparasite has been linked to several factors, including wild birds, fomites, farm workers, management of hen houses, and host traits. Along two consecutive years, we carried out systematic sampling at three laying hen farms located in Santa Fe province, Argentina, with the aim of identifying factors that may influence O. sylviarum prevalence and intensity. We found that the density of feathers around the hen vent area and the presence of Menoponidae lice were negatively associated with mite abundance. We also found that the density of hens in the cages was negatively associated with mite prevalence, suggesting a possible dilution effect, whereas prior reports found a positive association with hen density. In addition, summer was the season with minimum mite prevalences and intensities, contrary to previous studies in northern farms where warm weather appeared to prompt an increase in mite populations. Another factor associated with mite intensity was age, but this effect varied depending on the season, which hints that the association between hen's age and mites is complex. Basic epidemiological knowledge on O. sylviarum in poultry farms from South America may aid in a more efficient and integrative approach to its control.

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We investigated the patterns of flea infestation in wild populations of eight Sigmodontinae rodent species: Akodon azarae, Calomys callidus, Calomys venustus, Holochilus chacarius, Necromys lasiurus, Oligoryzomys flavescens, Oligoryzomys nigripes and Oxymycterus rufus. Rodents were captured in systematic trapping sessions carried out along 2 years at two localities from El Espinal Ecoregion, Argentina. Mean flea intensity, occurrence (presence/absence) of flea infestation, richness and diversity were compared for different ages, body condition, sex and rodent tribes (Akodontini, Oryzomyini and Phyllotini). A total of 376 fleas of the following species and subspecies were collected: Craneopsylla minerva wolffhuegeli, Polygenis (Neopolygenis) pradoi, Polygenis (Polygenis) axius axius, and Polygenis (Polygenis) byturus. The most important factor driving flea infestation was the rodent tribe, with Phyllotini showing the highest values of occurrence, abundance and species richness. Only C. m. wolffhuegeli was affected by the sex of the host. Age and body condition of the hosts did not affect flea infestation. Our results contribute to knowledge of the ecology of fleas on rodent hosts in El Espinal Ecoregion. The relevance of host taxonomy as driver of flea dynamics highlight the importance of considering host community structures at the time of studying the ecology of parasites.

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BACKGROUND: Rickettsial diseases are considered important in public health due to their dispersal capacity determined by the particular characteristics of their reservoirs and/or vectors. Among the latter, fleas play an important role, since the vast majority of species parasitize wild and invasive rodents, so their detection is relevant to be able to monitor potential emerging diseases. The aim of this study was to detect, characterize, and compare Rickettsia spp. from the fleas of micromammals in areas with different human population densities in Chile. METHODS: The presence of Rickettsia spp. was evaluated by standard polymerase chain reaction (PCR) and sequencing in 1315 fleas collected from 1512 micromammals in 29 locations, with different human population densities in Chile. A generalized linear model (GLM) was used to identify the variables that may explain Rickettsia prevalence in fleas. RESULTS: DNA of Rickettsia spp. was identified in 13.2% (174 of 1315) of fleas tested. Fifteen flea species were found to be Rickettsia-positive. The prevalence of Rickettsia spp. was higher in winter, semi-arid region and natural areas, and the infection levels in fleas varied between species of flea. The prevalence of Rickettsia among flea species ranged between 0-35.1%. Areas of lower human density showed the highest prevalence of Rickettsia. The phylogenetic tree showed two well-differentiated clades with Rickettsia bellii positioned as basal in one clade. The second clade was subdivided into two subclades of species related to Rickettsia of the spotted fever group. CONCLUSIONS: To our knowledge, this is the first report of the occurrence and molecular characterization of Rickettsia spp. in 15 flea species of micromammals in Chile. In this study, fleas were detected carrying Rickettsia DNA with zoonotic potential, mainly in villages and natural areas of Chile. Considering that there are differences in the prevalence of Rickettsia in fleas associated with different factors, more investigations are needed to further understand the ecology of Rickettsia in fleas and their implications for human health.

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The aim of this study was to detect and identify the presence of Rickettsia in fleas associated with cricetid rodents from northeastern Buenos Aires Province, Argentina. Sixteen fleas belonging to three species of Polygenis were collected from 56 cricetid rodents and analyzed for the presence of Rickettsia performing the conventional polymerase chain reaction (PCR) technique. Only one specimen of Polygenis (Polygenis) axius axius collected from Oxymycterus rufus was positive for Rickettsia felis using the gltA gene, and to ompA gene. This is the first report of R. felis in a Rhopalopsyllidae flea from Argentina, and the first detection of this bacterium in P. (P.) a. axius. Since both, O. rufus and P. (P.) a. axius, are common in areas close to humans, and enzootic cycle of R. felis is not fully understood, the results herein obtained might be of epidemiological importance. Further studies are needed in order to analyze the capacity of the species of Polygenis to transmit R. felis.

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Wild birds may be considered a possible source of parasitic mesostigmatid mites for poultry, but only few studies explored this hypothesis. In addition, there is very little information about the parasitic mites present in commercial poultry systems from southern South America. To contribute with data on parasitic mesostigmatid mites at the domestic-wildlife interface, we conducted a study in which samples were systematically collected from laying hens and wild birds (adults and nestlings), for two years at three commercial laying hen farms. The occurrence of mesostigmatid mites were compared among hosts. A proportion of the collected mites were morphologically identified to the species level, finding that host preference varied greatly depending on mite species: laying hens were only parasitized by Ornithonyssus sylviarum, wild bird nestlings were mostly parasitized by Ornithonyssus bursa, and in small proportion, by O. sylviarum, while adult passerines were parasitized by both Ornithonyssus species, and sporadically by Pellonyssus cf. reedi and Dermanyssus cf. triscutatus. In laying hens, there was intra- and inter-annual variability in mite occurrence, but no consistent seasonal pattern, whereas in adult wild birds, mites showed the highest prevalence in spring and the lowest in summer. Not coinciding with this general pattern, the occurrence of O. bursa matched the reproductive activity of wild birds. A phylogenetic analysis based on a fragment of the 16S rRNA gene was carried out for a subsample of the mites collected, showing that the O. sylviarum mites present on adult wild birds and laying hens had the same haplotype (100% identity). Additionally, mites obtained from wild birds morphologically identified as O. bursa presented two distinctive haplotypes (89.8% identity), one phylogenetically related to O. sylviarum and the other to O. monteiroi. These findings show that in central Argentina commercial laying hens are parasitized mainly by O. sylviarum while wild birds are also hosts to other mite species. Adult wild passerines, especially house sparrows, may be a source of O. sylviarum for commercial poultry.

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