ECTOPARASITES AND OTHER EPIFAUNISTIC ARTHROPODS OF SYMPATRIC COTTON MICE AND GOLDEN MICE: COMPARISONS AND IMPLICATIONS FOR VECTOR-BORNE ZOONOTIC DISEASES

The Coevolution Effect as a Driver of Spillover

Global habitat fragmentation is associated with the emergence of infectious diseases of wildlife origins in human populations. Despite this well-accepted narrative, the underlying mechanisms driving this association remain unclear. We introduce a nuanced hypothesis, the 'coevolution effect'. The central concept is that the subdivision of host populations which occurs with habitat fragmentation causes localized coevolution of hosts, obligate parasites, and pathogens which act as 'coevolutionary engines' within each fragment, accelerating pathogen diversification, and increasing pathogen diversity across the landscape. When combined with a mechanism to exit a fragment (e.g., mosquitoes), pathogen variants will spill over into human communities. Through this combined ecoevolutionary approach we may be able to understand the fine-scale mechanisms that drive disease emergence in the Anthropocene.

Host species influence on flea (Siphonaptera) infection parameters of terrestrial micromammals in a temperate forest of Mexico

Studies of abundance and distribution of organisms are fundamental to ecology. The identity of host species is known to be one of the major factors influencing ectoparasitic flea abundance, but explanations are still needed regarding how host taxa influence abundance parameters of different flea species. This study was carried out at La Malinche National Park (LMNP), Tlaxcala, Mexico, where previously 11 flea species had been recorded on 8 host species. Our aims were to list micromammal flea species, to determine flea infection parameters [flea prevalence (FP) and flea mean abundance (FMA)] and to analyse the influence of host species on these parameters. A total of 16 species of fleas were identified from 1178 fleas collected from 14 species of 1274 micromammals captured with Sherman® traps from March 2014 to December 2015 in 18 sites at LMNP. Some host species influence FP and FMA, in particular, Microtus mexicanus and Peromyscus melanotis showed particularly higher infection values than other host species. Plusaetis aztecus and Plusaetis sibynus were identified as the most abundant flea species.

Ectoparasites from some Myocastor coypus (Molina, 1782) populations (Coypus or Nutria) in Argentina

The occurrence of ectoparasites in wild nutria is poorly understood. Fifty-five livetrapped wild nutria (Myocastor coypus) from its indigenous region were examined for ectoparasites after capture from December 2013 to December 2014. The captures came from the Buenos Aires Province, by far the area of the country most densely populated by nutria, characterized as a temperate grassland, which are prime areas for sustained agriculture. Only one species of chewing lice (Pitrufquenia coypus, Marelli, 1932), one flea (Nosopsyllus fasciatus, Bosc, 1800) and one tick (Rhipicephalus sanguineus, Latreille, 1806) were collected. Fourteen percent of the animals were infested and P.coypus, an obligate parasite of the nutria, which was the most prevalent ectoparasite. N. fasciatus and R. sanguineus occurrence remains controversial as they may or may not be some accidental host species. To our knowledge, this is the first comprehensive and systematic survey of ectoparasites in wild nutria from the southern hemisphere, the indigenous region of this species.

Prevalencia de Borrelia burgdorferi sensu lato en roedores sinantrópicos de dos comunidades rurales de Yucatán, México

<p><strong>Introducción.</strong> La enfermedad de Lyme es una zoonosis multisistémica causada por Borrelia burgdorferi sensu lato. Esta espiroqueta circula en un ciclo enzoótico entre un reservorio vertebrado primario y las garrapatas. Diferentes especies de roedores están identificadas por ser eficientes reservorios naturales para B. burgdorferi s.l.</p><p><strong>Objetivo.</strong> Estimar la prevalencia de B. burgdorferi s.l. en roedores sinantrópicos empleando dos comunidades rurales de Yucatán, México.</p><p><strong>Materiales y métodos.</strong> Se capturaron 123 roedores (94 Mus musculus y 29 Rattus rattus) para obtener muestras de tejidos de oreja y vejiga. Para detectar la presencia de B. burgdorferi s.l. en la muestras, se amplificaron los genes de la flagelina B (fla B) y las lipoproteínas de membrana externa, ospC y p66, empleado la reacción en cadena de la polimerasa. Los amplicones obtenidos fueron secuenciados.</p><p><strong>Resultados.</strong> La frecuencia de infección de B. burgdorferi s.l. en roedores fue de 36,5% para flaB (45/123), 10,5% (13/123) para p66 y 3,2% (4/123) para ospC. R. rattus tuvo una frecuencia de infección de 17,2% y M. musculus de 42,5%. La frecuencia de infección de B. burgdorferi s.l. en los tejidos estudiados fue de 11,3% (14/123) en vejigas y 17,0% (21/123) en orejas. No se encontraron diferencias estadísticas (p &gt; 0,05) en la frecuencia de infección entre las dos muestras de tejido utilizadas para el diagnóstico. El gen ospC presentó un 98% de homología con la especie  Borrelia garinii, una de las especies heterogéneas del complejo B. burgdorferi s.l.</p><p> </p><p><strong>Conclusiones.</strong> Se concluye que los roedores presentan alta prevalencia de infección con B. burgdorferi s.l., y ambas especies, M. musculus y R. rattus, podrían estar jugando un papel importante en el mantenimiento de esta bacteria en comunidades rurales de Yucatán, México.</p><pre style="line-height: 200%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"><strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES">Introducción.</span></strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES"> La enfermedad de Lyme es una zoonosis multisistémica causada por <em>Borrelia burgdorferi</em> sensu lato. Esta espiroqueta circula en un ciclo enzoótico entre un reservorio vertebrado primario y las garrapatas. Diferentes especies de roedores están identificadas por ser eficientes reservorios naturales para <em>B. burgdorferi</em> s.l.</span></pre><pre style="line-height: 200%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"><strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES">Objetivo.</span></strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES"> Estimar la prevalencia de <em>B. burgdorferi</em> s.l. en roedores sinantrópicos empleando dos comunidades rurales de Yucatán, México.</span></pre><pre style="line-height: 200%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"><strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES">Materiales y métodos.</span></strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES"> Se capturaron 123 roedores (94 <em>Mus musculus</em> y 29 <em>Rattus rattus</em>) para obtener muestras de tejidos de oreja y vejiga. Para detectar la presencia de<em> B. burgdorferi</em> s.l. en la muestras, se amplificaron los genes de la flagelina B (<em>fla B</em>) y las lipoproteínas de membrana externa, <em>ospC</em> y <em>p66</em>, empleado la reacción en cadena de la polimerasa. Los amplicones obtenidos fueron secuenciados.</span></pre><pre style="line-height: 200%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"><strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES">Resultados.</span></strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES"> La frecuencia de infección de <em>B. burgdorferi</em> s.l. en roedores fue de 36,5% para <em>flaB</em> (45/123), 10,5% (13/123) para <em>p66 </em>y 3,2% (4/123) para <em>ospC</em>. <em>R. rattus</em> tuvo una frecuencia de infección de 17,2% y <em>M. musculus</em> de 42,5%. La frecuencia de infección de <em>B. burgdorferi</em> s.l. en los tejidos estudiados fue de 11,3% (14/123) en vejigas y 17,0% (21/123) en orejas. No se encontraron diferencias estadísticas (p &gt; 0,05) en la frecuencia de infección entre las dos muestras de tejido utilizadas para el diagnóstico. El gen <em>ospC</em> presentó un 98% de homología con la especie  <em>Borrelia garinii, </em>una de las especies heterogéneas del complejo<em> B. burgdorferi s.l</em>.</span></pre><pre style="line-height: 200%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"><strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES">Conclusiones.</span></strong><span style="font-size: 12.0pt; line-height: 200%; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: ES-MX;" lang="ES"> Se concluye que los roedores presentan alta prevalencia de infección con <em>B. burgdorferi</em> s.l., y ambas especies, <em>M. musculus</em> y <em>R. rattus, </em>podrían estar jugando un papel importante en el mantenimiento de esta bacteria en comunidades rurales de Yucatán, México.<strong></strong></span></pre>

Synanthropic rodents and their ectoparasites as carriers of a novel haemoplasma and vector-borne, zoonotic pathogens indoors

Background

Despite their close association with human dwellings, the role of synanthropic rodents in the epidemiology of vector-borne infections is seldom studied. The aim of the present study was to compensate for this lack of information, by the molecular investigation of vector-borne bacteria in peridomestic rodents and their ectoparasites.

Findings

Fifty-two rodents (mainly house mice and brown rats) were caught alive in buildings and checked for blood-sucking ectoparasites; followed by molecular analysis of these, together with spleen samples, for the presence of vector-borne agents. Haemoplasma infection was significantly more prevalent among brown rats, than among house mice. A novel haemoplasma genotype (with only 92-93% similarity to Candidatus Mycoplasma turicensis and M. coccoides in its 16S rRNA gene) was detected in a harvest mouse and a brown rat. Sporadic occurrence of Rickettsia helvetica, Anaplasma phagocytophilum, Borrelia burgdorferi s.l. and Bartonella sp. was also noted in rodents and/or their ectoparasites.

Conclusions

These results indicate that synanthropic rodents, although with low prevalence, may carry zoonotic and vector-borne pathogens indoors.

From population structure to genetically-engineered vectors: New ways to control vector-borne diseases?

Epidemiological studies on vectors and the pathogens they can carry (such as Borrelia burgdorferi) are showing some correlations between infection rates and biodiversity highlighting the "dilution" effects on potential vectors. Meanwhile other studies comparing sympatric small rodent species demonstrated that rodent species transmitting more pathogens are parasitized by more ectoparasite species. Studies on population structure and size have also proven a difference on the intensity of the parasitic infection. Furthermore, preliminary results in genetic improvement in mosquitoes (genetic markers, sexing, and genetic sterilization) will also increase performance as it has already been shown in field applications in developing countries. Recent results have greatly improved the fitness of genetically-modified insects compared to wild type populations with new approaches such as the post-integration elimination of transposon sequences, stabilising any insertion in genetically-modified insects. Encouraging results using the Sterile Insect Technique highlighted some metabolism manipulation to avoid the viability of offspring from released parent insect in the wild. Recent studies on vector symbionts would also bring a new angle in vector control capabilities, while complete DNA sequencing of some arthropods could point out ways to block the deadly impact on animal and human populations. These new potential approaches will improve the levels of control or even in some cases would eradicate vector species and consequently the vector-borne diseases they can transmit. In this paper we review some of the population biology theories, biological control methods, and the genetic techniques that have been published in the last years that are recommended to control for vector-borne diseases.

Covariance in species diversity and facilitation among non-interactive parasite taxa: all against the host

Different parasite taxa exploit different host resources and are often unlikely to interact directly. It is unclear, however, whether the diversity of any given parasite taxon is indirectly influenced by that of other parasite taxa on the same host. Some components of host immune defences may operate simultaneously against all kinds of parasites, whereas investment by the host in specific defences against one type of parasite may come at the expense of defence against other parasites. We investigated the relationships between the species diversity of 4 higher taxa of ectoparasites (fleas, sucking lice, mesostigmatid mites, and ixodid ticks), and between the species richness of ectoparasites and endoparasitic helminths, across different species of rodent hosts. Our analyses used 2 measures of species diversity, species richness and taxonomic distinctness, and controlled for the potentially confounding effects of sampling effort and phylogenetic relationships among host species. We found positive pairwise correlations between the species richness of fleas, mites and ticks; however, there was no association between species richness of any of these 3 groups and that of lice. We also found a strong positive relationship between the taxonomic distinctness of ecto- and endoparasite assemblages across host species. These results suggest the existence of a process of apparent facilitation among unrelated taxa in the organization of parasite communities. We propose explanations based on host immune responses, involving acquired cross-resistance to infection and interspecific variation in immunocompetence among hosts, to account for these patterns.

The reproductive success of the parasitic bat fly Basilia nana (Diptera: Nycteribiidae) is affected by the low roost fidelity of its host, the Bechstein’s bat (Myotis bechsteinii)

We studied the reproductive ecology of the bat fly Basilia nana on free-ranging colonial female and solitary male Bechstein's bats (Myotis bechsteinii) during one reproductive season. The reproduction of B. nana took place from April to September, and the production of puparia in bat roosts was high. The metamorphosis of the flies took a minimum of 30 days, and at least 86% of the puparia metamorphosed successfully. However, only about 30% of flies from puparia deposited in female roosts and 57% of flies from puparia deposited in male roosts emerged in the presence of Bechstein's bats and were thus able to survive. The significantly higher emergence success of bat flies in male roosts was caused by the higher roost fidelity of the solitary males compared with the social females. Our results indicate that bats can control the reproductive success of bat flies by switching and selecting roosts.