Diversity and host specificity of coccidia (Apicomplexa: Eimeriidae) in native and introduced squirrel species

CHARACTERIZATION OF EIMERIA LANCASTERENSIS AND EIMERIA ONTARIOENSIS (APICOMPLEXA: EIMERIIDAE) FOUND IN EASTERN GRAY SQUIRRELS, SCIURUS CAROLINENSIS (RODENTIA: SCIURIDAE), FROM ARKANSAS AND OKLAHOMA

We report the morphological characteristics of oocysts of Eimeria lancasterensisJoseph, 1969, collected from 6 of 6 (100%) eastern gray squirrels, Sciurus carolinensis, collected in Arkansas (n = 3) and Oklahoma (n = 3), and Eimeria ontarioensisLee and Dorney, 1971, recovered from an individual of S. carolinensis from Arkansas. Oocysts of E. lancasterensis were ovoidal to ellipsoidal, measuring (L × W) 24.0 × 14.6 (18-29 × 12-16) µm; shape index (L/W) was 1.6 (1.3-1.8). A micropyle and an oocyst residuum were absent, but up to 2 polar granules were present. Oocysts of E. ontarioensis were piriform and measured 40.6 × 26.0 (37-44 × 23-28); L/W was 1.6 (1.5-1.7). These oocysts possessed a distinct micropyle and rarely a polar granule but lacked an oocyst residuum. The DNA was isolated from both eimerians, and the 18S rDNA genetic markers were PCR-amplified, cloned, sequenced, and analyzed. To our knowledge, this study represents the first time 18S DNA sequence data have been generated from E. lancasterensis and E. ontarioensis found in North American sciurid hosts, as well as new geographic distribution records for these coccidians. In addition, we also include a tabular summary of these 2 species of Eimeria from Sciurus spp. worldwide, with information on their hosts, distribution, and taxonomically important morphological characteristics, including key measurements of oocysts and sporocysts.

Shifts in immune responses of an invasive alien species: A test of the evolution of increased competitive ability hypothesis using American Eastern gray squirrels in Italy

Based on the Evolution of Increased Competitive Ability (EICA) hypothesis, a reduced investment in immunity, consequent to parasite loss, could partly explain the success of invasive alien species. We investigated variation in parasite load and immune responses of alien Eastern gray squirrels (Sciurus carolinensis) along the invasion wave of an expanding population. We first verified by fecal analyses that 1) parasite abundance decreased moving from the core towards the invasion front. Next, we used multiple measures of immunity to investigate whether, in response to the lower parasite pressure, individuals at the invasion front 2) dampened their costly inflammatory response, and 3) increased their investment in less expensive acquired immunity. We first explored variation in hematological variables related either to the inflammatory or the acquired response. On a subset of individuals, we carried out ex vivo cell cultures to analyse the basal expression of MHC class II genes and the expression of TNF-α genes in response to an immune challenge. Platelet counts and TNF-α expression suggested higher inflammation in individuals living at the invasion core, whereas parameters associated with an acquired response (lymphocyte counts and MHC II expression by spleen cells), conversely, were higher in squirrels at the front. Overall, our results suggest a shift between different immune strategies along the invasion wave, supporting a reduced investment in costly inflammatory responses and an increased investment in acquired immunity in individuals at the expanding edge of the range, which are subjected to high selective pressures for dispersal and reproduction.

Interactions between native and invasive species: A systematic review of the red squirrel-gray squirrel paradigm

The eastern gray squirrel (Sciurus carolinensis) has been labeled as one of the 100 worst invasive alien species by the IUCN. In Europe, the species has been introduced to Britain, Ireland and Italy, and its subsequent spread has resulted in wide-scale extinction of native Eurasian red squirrels (Sciurus vulgaris) from the areas colonized by the gray squirrel. This replacement of a native by an alien competitor is one of the best documented cases of the devastating effects of biological invasions on native fauna. To understand how this replacement occurs, we present a systematic review of the literature on competition and interactions between red and gray squirrels. We describe the patterns of red and gray squirrel distribution in those parts of Europe where gray squirrels occur and summarize the evidence on the different processes and mechanisms determining the outcome of competition between the native and alien species including the influence of predators and pathogens. Some of the drivers behind the demise of the red squirrel have been intensively studied and documented in the past 30 years, but recent field studies and mathematical models revealed that the mechanisms underlying the red-gray paradigm are more complex than previously thought and affected by landscape-level processes. Therefore, we consider habitat type and multi-species interactions, including host-parasite and predator-prey relationships, to determine the outcome of the interaction between the two species and to better address gray squirrel control efforts.

Exotic Pet Trade as a Cause of Biological Invasions: The Case of Tree Squirrels of the Genus Callosciurus

Simple Summary

The pet industry is a growing global multibillion dollar market. The increase of exotic and non-domesticated animal ownership has led to an increase in the number of non-native pets released that create invasive alien species (IAS) populations in the wild. IAS negatively impact the biodiversity, human health and countries’ economies. We use tree squirrels of the genus Callosciurus as a well-documented case study of pets that become IAS. We review the pathways and range of introduction and the challenge and legal importance of species identification. Next, we document how they negatively affect native plants and animals, their parasitic infections that can threat native wildlife and human health and their impact on human activities and productive systems. We discuss the diverse biological, social, political and economic reasons that make control/eradication of these charismatic species difficult in most countries. However, we also highlight the successful management of the IAS in two countries where the early detection and engagement of stakeholders were key to successful eradication. We conclude that efforts to educate and involve the broader public by actively engaging a diversity of stakeholders are more likely to build a consensus toward IAS management and should be a priority for each country.

Abstract

The trade of non-native pets, especially of non-domesticated and exotic animals, and their subsequent release and establishment of populations is one of the major pathways of introduction for invasive alien reptiles, amphibia, birds and mammals. Here, we use a group of arboreal mammals, tree squirrels of the genus Callosciurus, as a well-documented case study, reviewing the pathways of introduction, the current areas of non-native distribution, the rate of establishment success and the challenge and legal importance of species identification. We further illustrate the importance of early detection and effective monitoring methods and plans. Next, we document how they interfere with native species, their risk of acting as vectors for emerging infectious diseases and their potential role in maintaining parasitic infections that can affect human health. We conclude by reviewing the current management, or the lack of it, and highlight the diverse biological, social, political and economic reasons that make control/eradication of these charismatic species difficult or even impractical in most countries. However, reviewing the only two successful eradications of the IAS, we highlight the need to acknowledge the public opinion and the importance of communication, transparency and the engagement of a diversity of stakeholders to create a consensus about the actions to undertake.

Cytochrome c oxydase I phylogenetic analysis of Haemogregarina parasites (Apicomplexa, Coccidia, Eucoccidiorida, Haemogregarinidae) confirms the presence of three distinct species within the freshwater turtles of Tunisia

Species of Haemogregarina are apicomplexan blood parasites that use vertebrates as intermediate hosts. Due to limited interspecific morphological characters within the genus during the last decade, 18S rRNA gene sequences were widely used for species identification. As coinfection patterns were recently reported from nuclear molecular data for two sympatric freshwater turtles Mauremys leprosa and Emys orbicularis from Tunisia, our objectives were to design COI specific primers to confirm the presence of three distinct species in both host species. Blood samples were collected from 22 turtles, from which DNAs were extracted and used as templates for amplification. Following different rounds of PCR and nested PCR, we designed specific Haemogregarina COI primers that allowed the sequencing of nine distinct haplotypes. Phylogenetic Bayesian analysis revealed the occurrence of three well-differentiated sublineages that clustered together into a single clade. Based on pairwise genetic distances (p-distance), we confirmed the occurrence of three distinct but phylogenetically closely related species coinfecting M. leprosa and E. orbicularis in the same aquatic environments. Our results demonstrate that the use of fast evolving genes within Haemogregarina will help to investigate the parasite diversity within both intermediate vertebrate and definitive invertebrate hosts, and to assess the evolution, historical biogeography and specificity of haemogregarines.

Complex relationships between physiological stress and endoparasite infections in natural populations

Short-term elevation of glucocorticoids (GCs) is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors (stressors). However, when exposure to stressors occurs repeatedly or over a prolonged period of time, animals may experience chronic elevation of GCs, which reduces the immune response efficiency and can lead to higher intensity of parasitic infection. Here, we used invasive gray squirrels Sciurus carolinensis introduced in Northern Italy and their 2 most prevalent gastrointestinal parasites, the nematode Strongyloides robustus and coccidia of the genus Eimeria, as a model to investigate relationships among macroparasite infection and concentrations of fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs. Our results revealed an association of FGMs with infection by St. robustus, but not with coccidia. Individuals with higher FGMs appear to be responsible for the greatest St. robustus egg shedding within gray squirrel populations, thus possibly acting as superspreaders. However, FGMs were negatively associated with adult St. robustus, suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs, but is only affected by it through immune-mediated effects on its fecundity. Finally, the relationship between St. robustus (both eggs and adult parasites) and FGMs was not linear, suggesting that only high levels of physiological stress influence parasite infection. Our findings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific host-parasite system, but also on the different life stages of the same parasite.

Eimeria sciurorum (Apicomplexa, Coccidia) From the Calabrian Black Squirrel (Sciurus meridionalis): An Example of Lower Host Specificity of Eimerians

Host specificity plays one of the key roles in parasitism. It affects the evolution and diversification of both host and parasite, as well as it influences their geographical distribution, and epidemiological significance. For most of parasites, however, host specificity is unknown or misrepresented because it is difficult to be determined accurately. Here we provide the information about the lower host specificity of Eimeria sciurorum infecting squirrels, and its new host record for the Calabrian black squirrel Sciurus meridionalis, a southern Italian endemic species.

Spillover of an alien parasite reduces expression of costly behaviour in native host species

Understanding the effects of invasive alien species (IAS) on native host-parasite relationships is of importance for enhancing ecological theory and IAS management. When IAS and their parasite(s) invade a guild, the effects of interspecific resource competition and/or parasite-mediated competition can alter existing native host-parasite relationships and the dependent biological traits such as native species' behaviour. We used a natural experiment of populations of native red squirrels Sciurus vulgaris that were colonized by the alien grey squirrel Sciurus carolinensis, comparing repeated measurements of red squirrel parasite infection and personality with those taken in sites where only the native species occurred. We explored two alternative hypotheses: (a) individual differences in personality traits (activity and/or sociability) of native red squirrel positively affect the probability of macroparasite spillover and thus the likelihood to acquire the alien's parasitic helminth Strongyloides robustus; (b) the combined effects of grey squirrel presence and parasite infection result in a reduction of costly personality traits (activity and/or exploration). Using data from 323 arena tests across three experimental (native species and IAS) and three control sites (only native species), we found negative correlations between native species' activity and infection with S. robustus in the sites invaded by the alien species. Activity was also negatively correlated with infection by its native helminth Trypanoxyuris sciuri but only when grey squirrels were present, while in the red-only sites there was no relationship of T. sciuri infection with any of the personality traits. Moreover, individuals that acquired S. robustus during the study reduced their activity after infection, while this was not the case for animals that remained uninfected. Our results show that parasite-mediated competition is costly, reducing activity in individuals of the native species, and altering the native host-native parasite relationships.

Detection and quantification of house mouse Eimeria at the species level - Challenges and solutions for the assessment of coccidia in wildlife

Detection and quantification of coccidia in studies of wildlife can be challenging. Therefore, prevalence of coccidia is often not assessed at the parasite species level in non-livestock animals. Parasite species – specific prevalences are especially important when studying evolutionary questions in wild populations. We tested whether increased host population density increases prevalence of individual Eimeria species at the farm level, as predicted by epidemiological theory.

We studied free-living commensal populations of the house mouse (Mus musculus) in Germany, and established a strategy to detect and quantify Eimeria infections. We show that a novel diagnostic primer targeting the apicoplast genome (Ap5) and coprological assessment after flotation provide complementary detection results increasing sensitivity. Genotyping PCRs confirm detection in a subset of samples and cross-validation of different PCR markers does not indicate bias towards a particular parasite species in genotyping. We were able to detect double infections and to determine the preferred niche of each parasite species along the distal-proximal axis of the intestine. Parasite genotyping from tissue samples provides additional indication for the absence of species bias in genotyping amplifications. Three Eimeria species were found infecting house mice at different prevalences: Eimeria ferrisi (16.7%; 95% CI 13.2–20.7), E. falciformis (4.2%; 95% CI 2.6–6.8) and E. vermiformis (1.9%; 95% CI 0.9–3.8). We also find that mice in dense populations are more likely to be infected with E. falciformis and E. ferrisi.

We provide methods for the assessment of prevalences of coccidia at the species level in rodent systems. We show and discuss how such data can help to test hypotheses in ecology, evolution and epidemiology on a species level.

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Flotation and PCR provide complementary results for Eimeria detection in house mice.

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Genotyping PCRs confirm detections.

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E. ferrisi, E. falciformis, and E. vermiformis infect natural populations of M. musculus.

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Double infections and preferentially infected tissues could be identified using qPCR.

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Potential virulence prevalence trade-off for Eimeria of house mice.

A new species of Eimeria Schneider, 1885 (Apicomplexa: Eimeriidae) from the eastern gray squirrel, Sciurus carolinensis (Rodentia: Sciuridae: Sciurinae: Sciurini) from Oklahoma, USA

A new species of Eimeria Schneider, 1885 is described from an eastern gray squirrel (Sciurus carolinensis) from McCurtain County, Oklahoma, USA. Oöcysts of Eimeria lukfataensis n. sp. are ellipsoidal with a rough pitted bi-layered wall, measure 23.8 × 14.9 µm, and have a length/width (L/W) ratio of 1.6; a micropyle is absent but an oöcyst residuum and polar granule(s) are present. Sporocysts are ellipsoidal and measure 12.5 × 6.1 µm, L/W 2.0; Stieda and sub-Stieda bodies are present, but para-Stieda body is absent. The sporocyst residuum is composed of small indistinct granules along the edge or in the center of the sporocyst. This is the first species of coccidian reported from S. carolinensis from Oklahoma and only the fourth species from the sciurid tribe Sciurini with oöcysts possessing an oöcyst residuum.

A newly described strain of Eimeria arloingi (strain A) belongs to the phylogenetic group of ruminant-infecting pathogenic species, which replicate in host endothelial cells in vivo

Coccidiosis caused by Eimeria species is an important disease worldwide, particularly in ruminants and poultry. Eimeria infection can result in significant economic losses due to costs associated with treatment and slower growth rates, or even with mortality of heavily infected individuals. In goat production, a growing industry due to increasing demand for caprine products worldwide, coccidiosis is caused by several Eimeria species with E. arloingi and E. ninakohlyakimovae the most pathogenic. The aims of this study were genetic characterization of a newly isolated European E. arloingi strain (A) and determination of phylogenetic relationships with Eimeria species from other ruminants. Therefore, a DNA sequence of E. arloingi strain (A) containing 2290 consensus nucleotides (the majority of 18S rDNA, complete ITS-1 and 5.8S sequences, and the partial ITS-2) was amplified and phylogenetic relationship determined with the most similar sequences available on GenBank. The phylogenetic tree presented a branch constituted by bovine Eimeria species plus E. arloingi, and another one exclusively populated by ovine Eimeria species. Moreover, E. arloingi, E. bovis and E. zuernii, which all replicate in host intestinal endothelial cells of the lacteals, were found within the same cluster. This study gives new insights into the evolutionary phylogenetic relationships of this newly described caprine Eimeria strain and confirmed its close relationship to other highly pathogenic ruminant Eimeria species characterized by macromeront formation in host endothelial cells of the central lymph capillaries of the small intestine.

Native and introduced squirrels in Italy host different Cryptosporidium spp

The present study was undertaken to describe Cryptosporidium spp. infection in tree squirrels from 17 locations in Northern Italy. A total of 357 squirrels were examined, including species native to Europe (Sciurus vulgaris; n=123), and species introduced from North America (Sciurus carolinensis; n=162) and Southeast Asia (Callosciurus erythraeus; n=72). Faecal samples of all squirrels were examined for the presence of Cryptosporidium infection by microscopy (flotation method) and PCR/sequence analysis of the Cryptosporidium 18S rRNA, actin, and gp60 genes. Despite the overlapping ranges of native and introduced tree squirrel species in the study area, they host different Cryptosporidium spp. Sciurus vulgaris were exclusively infected with Cryptosporidium ferret genotype (n=13) belonging to three novel gp60 subtypes, VIIIb-VIIId. Sciurus carolinensis hosted C. ubiquitum subtype XIIb (n=2), Cryptosporidium skunk genotype subtype XVIa (n=3), and chipmunk genotype I subtype XIVa (n=1). Cryptosporidium chipmunk genotype I subtype XIVa was also found in two C. erythraeus. Comparing data from this and previous studies, we propose that Cryptosporidium skunk genotype and possibly C. ubiquitum subtype XIIb were introduced to Europe with eastern grey squirrels. Cryptosporidium chipmunk genotype I and ferret genotype were associated with high intensity infections, but there was no association with diarrhoea.