Ecology of the interaction between Ixodes loricatus (Acari: Ixodidae) and Akodon azarae (Rodentia: Criceridae)

Parasite species co-occurrence patterns on Peromyscus: Joint species distribution modelling

Hosts are often infested by multiple parasite species, but it is often unclear whether patterns of parasite co-occurrence are driven by parasite habitat requirements or parasite species interactions. Using data on infestation patterns of ectoparasitic arthropods (fleas, trombiculid mites, cuterebrid botflies) from deer mice (Peromyscus maniculatus), we analyzed species associations using joint species distribution modelling. We also experimentally removed a flea (Orchopeas leucopus) from a subset of deer mice to examine the effect on other common ectoparasite species. We found that the mite (Neotrombicula microti) and botfly (Cuterebra sp.) had a negative relationship that is likely a true biotic species interaction. The flea had a negative association with the mite and a positive association with the botfly species, both of which appeared to be influenced by host traits or parasite life-history traits. Furthermore, experimental removal of the flea did not have a significant effect on ectoparasite prevalence of another species. Overall, these findings suggest that complex parasite species associations can be present among multiple parasite taxa, and that aggregation is not always the rule for ectoparasite communities of small mammals.

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A negative species interaction was identified between a mite and botfly species.

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Additional parasite associations appear to be influenced by host traits or parasite life-history traits.

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Removal of the flea species did not have an effect on prevalence of another species.

Host-parasite association between Didelphis albiventris (Didelphimorphia: Didelphidae) and Ixodes loricatus (Acari: Ixodidae) in their southern ranges

The parasitism of Ixodes loricatus Neumann on white-eared opposum, Didelphis albiventris Lund, was analysed in the southern ranges of both. In central Argentina, 118 wild opossums were captured from 2005 to 2012. Adults of I. loricatus were collected (prevalence = 66.1%, mean = 7.03, median = 4), but no immature stage. Tick infestation was not affected by sex (p = 0.27) or age (p = 0.37) of hosts. In line with previous studies about seasonality of larvae and nymphs of I. loricatus, adult tick infestation showed no seasonal trend. This lack of seasonal pattern of infestation for all parasitic stages of I. loricatus may indicate a life cycle governed by nidicolous behaviour, in such a way that this habit would contribute to minimize the influence of external environmental variables. The tick sex ratio was female biased, with two females per one male (p = 0.002). The absence of I. loricatus immatures on D. albiventris suggests that in the study region there is clear segregation of immatures in rodents and adults in marsupials.

Novel Babesia and Hepatozoon agents infecting non-volant small mammals in the Brazilian Pantanal, with the first record of the tick Ornithodoros guaporensis in Brazil

Taking into account the diversity of small terrestrial mammals of the Pantanal, the present study aimed to verify the occurrence of infection by Ehrlichia spp., Anaplasma spp., Rickettsia spp., Hepatozoon spp., Babesia spp. and parasitism by ticks in non-volant small mammals collected in the Brazilian Pantanal. Samples of blood, liver and spleen were collected from 64 captured animals, 22 marsupials and 42 rodents. Pathogen detection was performed by the use of genus-specific Polymerase Chain Reaction (PCR) assays. Ticks collected from the animals consisted of Amblyomma sculptum and Amblyomma triste nymphs, and Ornithodoros guaporensis larvae. None of the vertebrate samples (blood, liver, or spleen) yielded detectable DNA of Rickettsia spp. or Ehrlichia spp. The blood of the rodent Hylaeamys megacephalus yielded an Anaplasma sp. genotype (partial 16S rRNA gene) 99% similar to multiple Anaplasma spp. genotypes around the world. The blood of three rodents of the species Calomys callosus were positive for a novel Hepatozoon sp. agent, phylogenetically related (18S rDNA gene) to distinct Hepatozoon genotypes that have been detected in rodents from different parts of the world. One marsupial (Monodelphis domestica) and three rodents (Thrichomys pachyurus) were positive to novel piroplasmid genotypes, phylogenetically (18S rDNA gene) related to Theileria bicornis, Cytauxzoon manul, and Cytauxzoon felis. The present study provides the first molecular detection of Hepatozoon sp. and piroplasmids in small mammals in Brazil. Additionally, we expanded the distribution of O. guaporensis to Brazil, since this tick species was previously known to occur only in Bolivia.