Assessment of FDA-approved drugs against Strongyloides ratti in vitro and in vivo to identify potentially active drugs against strongyloidiasis.

BACKGROUND: Infections with Strongyloides stercoralis belong to the most neglected helminth diseases, and research and development (R&D) efforts on novel drugs are inadequate. METHODS: A commercially available library containing 1600 FDA-approved drugs was tested in vitro against Strongyloides ratti larvae (L3) at 100 µM. Hits (activity > 70%) were then evaluated against S. ratti adult worms at 10 µM. Morantel, prasterone, and levamisole were tested in the S. ratti rat model using dosages of 1-100 mg/kg. RESULTS: Seventy-one of the 1600 compounds tested against S. ratti L3 revealed activity above 70%. Of 64 compounds which progressed into the adult screen, seven compounds achieved death of all worms (benzethonium chloride, cetylpyridinium chloride, Gentian violet, methylbenzethonium chloride, morantel citrate, ivermectin, coumaphos), and another eight compounds had activity > 70%. Excluding topical and toxic compounds, three drugs progressed into in vivo studies. Prasterone lacked activity in vivo, while treatment with 100 mg/kg morantel and levamisole cured all rats. The highest in vivo activity was observed with levamisole, yielding a median effective dose (ED50) of 1.1 mg/kg. CONCLUSIONS: Using a drug repurposing approach, our study identified levamisole as a potential backup drug for strongyloidiasis. Levamisole should be evaluated in exploratory clinical trials.

Flea infestation, social contact, and stress in a gregarious rodent species: minimizing the potential parasitic costs of group-living.

Both parasitism and social contact are common sources of stress that many gregarious species encounter in nature. Upon encountering such stressors, individuals secrete glucocorticoids and although short-term elevation of glucocorticoids is adaptive, long-term increases are correlated with higher mortality and deleterious reproductive effects. Here, we used an experimental host-parasite system, social rodents Acomys cahirinus and their characteristic fleas Parapulex chephrenis, in a fully-crossed design to test the effects of social contact and parasitism on stress during pregnancy. By analysing faecal glucocorticoid metabolites, we found that social hierarchy did not have a significant effect on glucocorticoid concentration. Rather, solitary females had significantly higher glucocorticoid levels than females housed in pairs. We found a significant interaction between the stressors of parasitism and social contact with solitary, uninfested females having the highest faecal glucocorticoid metabolite levels suggesting that both social contact and infestation mitigate allostatic load in pregnant rodents. Therefore, the increased risk of infestation that accompanies group-living could be outweighed by positive aspects of social contact within A. cahirinus colonies in nature.

Subtle short-term physiological costs of an experimental augmentation of fleas in wild Columbian ground squirrels.

Parasites affect many aspects of host physiology and behavior, and thus are generally thought to negatively impact host fitness. However, changes in form of short-term parasite effects on host physiological markers have generally been overlooked in favor of fitness measures. Here, we studied flea (Oropsylla idahoensis and Oropsylla opisocroistis tuberculata) parasitism on a natural population of Columbian ground squirrels (Urocitellus columbianus) in Sheep River Provincial Park, AB, Canada. Fleas were experimentally added to adult female U. columbianus at physiologically demanding times, including birth, lactation and weaning of their young. The body mass of adult females, as well as their oxidative stress and immunity were recorded multiple times over the active season under flea-augmented and control conditions. We also measured the prevalence of an internal parasite (Trypanosoma otospermophili). Doubly labeled water (DLW) was intra-peritoneally injected at peak lactation to examine energy expenditure. Effects of parasites on oxidative stress were only observed after offspring were weaned. There was no direct effect of experimentally heightened flea prevalence on energy use. A short-term 24 h mass loss (-17 g) was detected briefly after parasite addition, likely due to U. columbianus preferentially allocating time for grooming. Our parasite augmentation did not strongly affect hosts and suggested that short-term physiological effects were unlikely to culminate in long-term fitness consequences. Columbian ground squirrels appear to rapidly manage parasite costs, probably through grooming.

Assessment of the global pattern of genetic diversity in Echinococcus multilocularis inferred by mitochondrial DNA sequences.

The aim of this review was to assess our current knowledge on phylogeography and global genetic structure of Echinococcus multilocularis populations originating from rodents, wild canid hosts, and human. Six bibliographic databases were searched from 1990 to 2017, identifying a total of 110 publications. The cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) sequences of E. multilocularis from Asia, Europe, and North Americas were analyzed to estimate the diversity and neutrality indices, and genetic differentiation. A total of 69 (cox1, 36.7%) and 16 haplotypes (cytb, 19.2%) were grouped into various geographical clades. A parsimonious haplotype network demonstrated a star-like feature with haplo-groups Em2 (Asia: 36%), Em105 (Eastern Tibetan plateau: 4.8%), Em46 (Europe: 9.1%), Em73, (Europe: 2.7%) and Em92 (North Americas: 4.3%) as the most common haplotypes. A relatively high level of genetic diversity was detected in rodent-derived E. multilocularis isolates (Haplotype diversity: 0.944), wild canids (Hd: 0.912), and human origin (Hd: 0.704). The highest number of haplotypes (n = 59) and the highest haplotype diversity (0.969) were identified in the Asian and European populations, respectively. Cladistic phylogenetic tree indicated the European clade has a sister relationship with the Asian clade. However, some North American haplotypes were assigned to the European clade together with haplotypes from Poland. The statistically significant Fst values indicated that E. multilocularis populations of Asian-European, Asian-North American, and European-North American origins were genetically differentiated (Fst: 0.22624 to 0.43059). An occurrence of distinct parasite populations suggests that E. multilocularis derived from glacial refugia have been plausibly sustained by indigenous hosts during the Pleistocene Epoch.

New host, geographic records, and histopathologic studies of Angiostrongylus spp (Nematoda: Angiostrongylidae) in rodents from Argentina with updated summary of records from rodent hosts and host specificity assessment.

To date, 21 species of the genus Angiostrongylus (Nematoda: Angiostrongylidae) have been reported around the world, 15 of which are parasites of rodents. In this study, new host, geographic records, and histopathologic studies of Angiostrongylus spp in sigmodontine rodents from Argentina, with an updated summary of records from rodent hosts and host specificity assessment, are provided. Records of Angiostrongylus costaricensis from Akodon montensis and Angiostrongylus morerai from six new hosts and geographical localities in Argentina are reported. The gross and histopathologic changes in the lungs of the host species due to angiostrongylosis are described. Published records of the genus Angiostrongylus from rodents and patterns of host specificity are presented. Individual Angiostrongylus species parasitise between one-19 different host species. The most frequent values of the specificity index (STD) were between 1-5.97. The elevated number of host species (n = 7) of A. morerai with a STD = 1.86 is a reflection of multiple systematic studies of parasites from sigmodontine rodents in the area of Cuenca del Plata, Argentina, showing that an increase in sampling effort can result in new findings. The combination of low host specificity and a wide geographic distribution of Angiostrongylus spp indicates a troubling epidemiological scenario although, as yet, no human cases have been reported.

Time budget, oxygen consumption and body mass responses to parasites in juvenile and adult wild rodents.

BACKGROUND: The study of changes in a host's energy allocation in response to parasites is crucial for understanding parasite impact on both individual- and population-level processes. Experimental studies have explored such responses mainly in a single subsample of hosts per study, primarily adult males, and have only assessed either the overall energy acquisition or expenditure, rather than their different components simultaneously, or the behavioral responses. Accordingly, two fundamental questions arise: why have multiple host strategies evolved to cope with increased energy expenditure? and, which factors determine this variation (e.g. host species, identity, age)? This study provides an important step towards addressing both questions by experimentally disentangling the short-term physiological and behavioral responses of juvenile and non-reproductive adult rodents to natural levels of flea infestation. These two cohorts represent extreme cases of the energy demand continuum, as the former, in contrast to the latter, is involved in growth--a highly energy-demanding process--and may not be able to operate far below its upper limit of energy expenditure, and thus should reduce its energy expenses upon the occurrence of extra demands (e.g. due to parasitic pressure). Accordingly, we hypothesized that the response to fleas is age-dependent and varies according to the age-specific energy requirements and constraints. METHODS: We monitored the behavior and physiology of juvenile and non-reproductive adult rodents before and after experimental flea infestation. First, we used a model selection approach to search for the factors that best explained the variability in the time budget, oxygen consumption, and body mass change in response to fleas. Then, using a path analysis approach, we quantified the different pathways connecting the important associations revealed at stage 1. RESULTS: Compared to their flea-free counterparts, flea-infested adults groomed longer and had a higher oxygen consumption rate, but did not lose body mass. Infested juveniles also groomed longer but grew slower and had a similar rate of oxygen consumption. CONCLUSIONS: Results suggest that both juvenile and adult rodents suffer from natural flea infestation levels. However, the comparison between the responses of juveniles and adults to experimental infestation, also suggests that juveniles may reallocate their energy expenditure from growth to maintenance, while non-reproductive adults increase their energy acquisition. Such age-dependent responses suggest that juveniles may be constrained by their higher need to rest for full functioning or by an upper limit in energy expenditure. Taken together, our study provides experimental evidence that hosts can compensate for the costs incurred by parasitism through physiological and behavioral plasticity, depending on their age, which probably determines their requirements and constraints. These compensatory responses may have important implications for the population dynamics of hosts and their parasites.

New host, geographic records, and histopathologic studies ofAngiostrongylus spp (Nematoda: Angiostrongylidae) in rodents from Argentina with updated summary of records from rodent hosts and host specificity assessment

To date, 21 species of the genus Angiostrongylus (Nematoda: Angiostrongylidae) have been reported around the world, 15 of which are parasites of rodents. In this study, new host, geographic records, and histopathologic studies of Angiostrongylus spp in sigmodontine rodents from Argentina, with an updated summary of records from rodent hosts and host specificity assessment, are provided. Records of Angiostrongylus costaricensis from Akodon montensis andAngiostrongylus morerai from six new hosts and geographical localities in Argentina are reported. The gross and histopathologic changes in the lungs of the host species due to angiostrongylosis are described. Published records of the genus Angiostrongylus from rodents and patterns of host specificity are presented. Individual Angiostrongylusspecies parasitise between one-19 different host species. The most frequent values of the specificity index (STD) were between 1-5.97. The elevated number of host species (n = 7) of A. morerai with a STD = 1.86 is a reflection of multiple systematic studies of parasites from sigmodontine rodents in the area of Cuenca del Plata, Argentina, showing that an increase in sampling effort can result in new findings. The combination of low host specificity and a wide geographic distribution of Angiostrongylus spp indicates a troubling epidemiological scenario although, as yet, no human cases have been reported.

An Overview of Typical Infections of Research Mice: Health Monitoring and Prevention of Infection.

There are many reasons to keep research mice healthy and free from infections. The two most important of these are to protect the health and welfare of research mice and to prevent infections from negatively impacting research. Just as the genetic integrity of a mouse strain will influence the reproducibility and validity of research data, so too will the microbiologic integrity of the animals. This has been repeatedly demonstrated in the literature of laboratory animal sciences wherein the direct impact of infections on physiologic parameters under study have been described. Therefore, it is of great importance that scientists pay close attention to the health status of their research animal colonies and maintain good communications with the animal facility personnel at their institution about mouse health issues. This overview provides information about animal health monitoring (HM) in research mouse colonies including commonly monitored agents, diagnostic methods, HM program, risk assessment, and animal facility biosecurity. Lastly, matters of communication with laboratory animal professionals at research institutions are also addressed.

Positive co-occurrence of flea infestation at a low biological cost in two rodent hosts in the Canary archipelago.

Non-random assemblages have been described as a common pattern of flea co-occurrence across mainland host species. However, to date, patterns of flea co-occurrence on islands are unknown. The present work investigates, on one hand, whether the decrease in the number of species on islands affects the pattern of flea co-occurrence, and on the other hand, how the cost of higher flea burdens affects host body mass. The study was carried out in the Canary Islands (Spain) using null models to analyse flea co-occurrence on Rattus rattus and Mus musculus. Results supported aggregation of flea species in Mus but not in Rattus, probably due to the relationship between abundance and both prevalence and intensity of infection of the main flea species parasitizing Mus. In addition, heavy individuals of both rodent species showed the highest flea burdens as well as higher species richness, probably due to the continued accumulation of fleas throughout life and/or immunological resistance mechanisms. Whatever the mechanisms involved, it is clear that co-occurrence and high parasite intensities do not imply a detrimental biological cost for the rodents of the Canary Islands.

Energy expenditure for egg production in arthropod ectoparasites: the effect of host species.

We studied the energy cost of egg production in two flea species (Parapulex chephrenis and Xenopsylla ramesis) feeding on principal (Acomys cahirinus and Meriones crassus, respectively) and auxiliary (M. crassus and A. cahirinus, respectively) rodent hosts. We predicted that fleas feeding on principal as compared with auxiliary hosts will (a) expend less energy for egg production; (b) produce larger eggs and (c) live longer after oviposition. Both fleas produced more eggs and spent less energy per egg when exploiting principal hosts. Parapulex chephrenis produced larger eggs after exploiting auxiliary hosts, while the opposite was true for X. ramesis. After oviposition, P. chephrenis fed on the auxiliary hosts survived for a shorter time than those fed on the principal hosts, while in X. ramesis the survival time did not differ among hosts. Our results suggested that one of the proximate causes for lower reproductive performance and subsequent lower abundance of fleas on auxiliary hosts is the higher energy cost of egg production. However, in some species, lower offspring number may be compensated to some extent by their size, although this compensation may also compromise their future reproduction via decreased survival. In addition, the reproductive strategy of exploitation of low profitable (i.e. auxiliary) hosts may differ between flea species.

Laoxyuris laonasti n. gen., n. sp. (Nematoda: Syphaciinae) parasite of Laonastes aenigmamus (Rodentia: Diatomyidae): morphology, biology, taxonomy, phylogeny.

A new Oxyurid genus and species are described in a rodent recently discovered in Lao PDR: Laonastes aenigmamus which happens to be the single survivor of the Diatomyidae, a family considered to be extinct since the Miocene. The morphological characters of the new parasite species allow classifying it within the Syphaciinae Railliet, 1916, a subfamily whose members are exclusively parasites of Lagomorpha and Rodents. Male Syphaciinae have developed several types of ventral cuticular ornamentation used to firmly grip the female during mating. The ornamental characters observed in the new species include a finger like appendix, which, until now, has not been described in the subfamily. The originality of this apparatus justifies the creation of a new genus and a new species for the pinworm parasite of Laonastes. Using morphological characters, the new species is analyzed phylogenetically to describe its affinities with representatives of the main groups distinguished within the Syphaciinae. The phylogenetic study produces a cladogram similar to the phylogeny recently proposed for the hosts of the subfamily and in agreement with a close association of the Diatomyidae with the Ctenodactylidae. Such a phenomenon of cophylogeny is interpreted as the result of the existence of a strict specificity between the Syphaciinae and their respective hosts, due to the very close adaptation of their life cycle with the behaviors of their hosts. In Lagomorpha and Rodents, caecotrophy and grooming activities allow a direct transmission of the parasite eggs and favor successive self-infestations, increasing the chances for the parasite to maintain itself in the same host species but decreasing the probability of host switching. The resulting high host specificity allowed the Syphaciinae to out-compete other pinworms and maintain themselves in their specific host over millions of years.

Effects of deer density on tick infestation of rodents and the hazard of tick-borne encephalitis. I: empirical assessment.

Tick borne encephalitis (TBE) is endemic to eastern and central Europe with broad temporal and spatial variation in infection risk. Although many studies have focused on understanding the environmental and socio-economic factors affecting exposure of humans to TBE, comparatively little research has been devoted to assessing the underlying ecological mechanisms of TBE occurrence in enzootic cycles, and therefore TBE hazard. The aim of this study was to evaluate the effect of the main ungulate tick hosts on the pattern of tick infestation in rodents and TBE occurrence in rodents and questing adult ticks. In this empirical study, we considered three areas where endemic human TBE occurs and three control sites having no reported human TBE cases. In these six sites located in Italy and Slovakia, we assessed deer density using the pellet group count-plot sampling technique, collected questing ticks, live-trapped rodents (primarily Apodemus flavicollis and Myodes glareolus) and counted ticks feeding on rodents. Both rodents and questing ticks were screened for TBE infection. TBE infection in ticks and rodents was positively associated with the number of co-feeding ticks on rodents and negatively correlated with deer density. We hypothesise that the negative relationship between deer density and TBE occurrence on a local scale (defined by the minimum overlapping area of host species) could be attributed to deer (incompetent hosts) diverting questing ticks from rodents (competent hosts), know as the 'dilution effect hypothesis'. We observed that, after an initial increase, the number of ticks feeding on rodents reached a peak for an intermediate value of estimated deer density and then decreased. Therefore, while at a regional scale, tick host availability has already been shown to be directly correlated with TBE distribution, our results suggest that the interactions between deer, rodents and ticks are much more complex on a local scale, supporting the possibility of a dilution effect for TBE.

Field assessment of Trypanosoma cruzi infection and host survival in the native rodent Octodon degus.

Chagas disease is a zoonosis caused by the flagellated parasite Trypanosoma cruzi and transmitted by triatomine insects to several mammalian species acting as reservoir hosts. In the present study, we assess T. cruzi-prevalence, survivorship and T. cruzi-infection rate of the endemic rodent Octodon degus from a hyper-endemic area of Chagas disease in Chile. Parasite detection is performed by PCR assays on blood samples of individuals captured in austral summer of 2010, and on non-infected individuals recaptured in 2011 as well as on new captures. Results show a high infection level in this species (up to 70%). Infected O. degus have the same chance of surviving to the next reproductive season as uninfected individuals, irrespective of sex. We suggest that O. degus, an abundant long-lived rodent with high dispersal capability, could be considered an important native reservoir of T. cruzi in the wild transmission cycle of Chagas disease in Chile.

In vitro and in vivo assessment of the anti-malarial activity of Caesalpinia pluviosa.

BACKGROUND: To overcome the problem of increasing drug resistance, traditional medicines are an important source for potential new anti-malarials. Caesalpinia pluviosa, commonly named "sibipiruna", originates from Brazil and possess multiple therapeutic properties, including anti-malarial activity. METHODS: Crude extract (CE) was obtained from stem bark by purification using different solvents, resulting in seven fractions. An MTT assay was performed to evaluate cytotoxicity in MCF-7 cells. The CE and its fractions were tested in vitro against chloroquine-sensitive (3D7) and -resistant (S20) strains of Plasmodium falciparum and in vivo in Plasmodium chabaudi-infected mice. In vitro interaction with artesunate and the active C. pluviosa fractions was assessed, and mass spectrometry analyses were conducted. RESULTS: At non-toxic concentrations, the 100% ethanolic (F4) and 50% methanolic (F5) fractions possessed significant anti-malarial activity against both 3D7 and S20 strains. Drug interaction assays with artesunate showed a synergistic interaction with the F4. Four days of treatment with this fraction significantly inhibited parasitaemia in mice in a dose-dependent manner. Mass spectrometry analyses revealed the presence of an ion corresponding to m/z 303.0450, suggesting the presence of quercetin. However, a second set of analyses, with a quercetin standard, showed distinct ions of m/z 137 and 153. CONCLUSIONS: The findings show that the F4 fraction of C. pluviosa exhibits anti-malarial activity in vitro at non-toxic concentrations, which was potentiated in the presence of artesunate. Moreover, this anti-malarial activity was also sustained in vivo after treatment of infected mice. Finally, mass spectrometry analyses suggest that a new compound, most likely an isomer of quercetin, is responsible for the anti-malarial activity of the F4.

Fitness costs of disrupting circadian rhythms in malaria parasites.

Circadian biology assumes that biological rhythms maximize fitness by enabling organisms to coordinate with their environment. Despite circadian clocks being such a widespread phenomenon, demonstrating the fitness benefits of temporal coordination is challenging and such studies are rare. Here, we tested the consequences--for parasites--of being temporally mismatched to host circadian rhythms using the rodent malaria parasite, Plasmodium chabaudi. The cyclical nature of malaria infections is well known, as the cell cycles across parasite species last a multiple of approximately 24 h, but the evolutionary explanations for periodicity are poorly understood. We demonstrate that perturbation of parasite rhythms results in a twofold cost to the production of replicating and transmission stages. Thus, synchronization with host rhythms influences in-host survival and between-host transmission potential, revealing a role for circadian rhythms in the evolution of host-parasite interactions. More generally, our results provide a demonstration of the adaptive value of circadian rhythms and the utility of using an evolutionary framework to understand parasite traits.

Assessment of immune activation in mice before and after eradication of mite infestation.

Mite infestation of mice remains a persistent problem for many institutions, leading to numerous health problems and creating unknown and unwanted variables for research. In this study, mice with mite infestation demonstrated significantly higher levels of inflammatory cytokines, both at draining lymph nodes (axillary) and systemically, as compared with mice without mites. In addition, histologic evaluation revealed significant inflammation in mite-infested mice. Inflammatory changes were still present in the skin of mice at 6 to 8 wk after treatment, despite absence of detectable infestation at that time. Because these significant and lasting local and systemic changes have the potential to alter research findings, eradication of mites infestations should be an important goal for all institutions.

A cost-effective and efficacious method of pinworm treatment for large colonies of mice.

Rodent pinworm infestations are common in modern animal facilities, and treatments to eradicate these nematodes are often costly and labor-intensive. The authors describe a method they developed to treat rodents with ivermectin using the automatic watering system available at their facility. This delivery method proved an efficacious and cost-effective means of eradicating Aspiculuris tetraptera from a large colony of mice. The system might also be used to provide other orally administered agents to mice and other species.

Assessment of methods of destruction of Syphacia muris eggs.

An investigation was performed to identify methods suitable for decontamination of equipment being transferred from a facility contaminated with Syphacia muris to a new facility. Perianal samples were taken on clear sticky tape from rats known to be infected with S. muris. Tapes and attached worm eggs were treated with ethylene oxide, formaldehyde fumigation, potassium peroxysulphate, chlorine dioxide and didecyl di-methyl ammonium chloride, chlorine dioxide, alcohol/chlorhexidine, 100 degrees C dry heat for 30 min, ultraviolet light (UV), or left for 4 weeks at room temperature. The subsequent viability of the eggs was compared to untreated control samples. Heat and ethylene oxide produced a 100% kill rate of S. muris eggs. Formaldehyde gas and chlorine dioxide treatments showed marked effectiveness, with the number of eggs killed at 94% and 96%, respectively, while the other agents showed less efficacy (36-78% eggs killed). The percentage of eggs not hatching in the controls was 21%. Since so few agents were effective against S. muris eggs, care should be taken when choosing a method for decontaminating a facility.

Inferring infection processes of a parasitic nematode using population genetics.

The distribution of genetic differentiation in a population of the parasitic nematode Strongyloides ratti divided between rat hosts was determined. We applied population genetic theory to these data to determine the source of new infections. We estimate the rate at which a rat acquires a new infection from (a) the existing subpopulation of parasites within that rat ('self-reinfection') versus (b) the wider environment ('immigration'). We find that the observed levels of genetic diversity and differentiation in the study population are consistent with low to moderate rates of self-reinfection and inconsistent with high rates of self-reinfection.