Virus replication in the honey bee parasite, Varroa destructor.

IMPORTANCE: The parasitic mite Varroa destructor is a significant driver of worldwide colony losses of our most important commercial pollinator, the Western honey bee Apis mellifera. Declines in honey bee health are frequently attributed to the viruses that mites vector to honey bees, yet whether mites passively transmit viruses as a mechanical vector or actively participate in viral amplification and facilitate replication of honey bee viruses is debated. Our work investigating the antiviral RNA interference response in V. destructor demonstrates that key viruses associated with honey bee declines actively replicate in mites, indicating that they are biological vectors, and the host range of bee-associated viruses extends to their parasites, which could impact virus evolution, pathogenicity, and spread.

Host-multiparasite interactions in amphibians: a review.

Parasites, including viruses, bacteria, fungi, protists, helminths, and arthropods, are ubiquitous in the animal kingdom. Consequently, hosts are frequently infected with more than one parasite species simultaneously. The assessment of such co-infections is of fundamental importance for disease ecology, but relevant studies involving non-domesticated animals have remained scarce. Many amphibians are in decline, and they generally have a highly diverse parasitic fauna. Here we review the literature reporting on field surveys, veterinary case studies, and laboratory experiments on co-infections in amphibians, and we summarize what is known about within-host interactions among parasites, which environmental and intrinsic factors influence the outcomes of these interactions, and what effects co-infections have on hosts. The available literature is piecemeal, and patterns are highly diverse, so that identifying general trends that would fit most host-multiparasite systems in amphibians is difficult. Several examples of additive, antagonistic, neutral, and synergistic effects among different parasites are known, but whether members of some higher taxa usually outcompete and override the effects of others remains unclear. The arrival order of different parasites and the time lag between exposures appear in many cases to fundamentally shape competition and disease progression. The first parasite to arrive can gain a marked reproductive advantage or induce cross-reaction immunity, but by disrupting the skin and associated defences (i.e., skin secretions, skin microbiome) and by immunosuppression, it can also pave the way for subsequent infections. Although there are exceptions, detrimental effects to the host are generally aggravated with increasing numbers of co-infecting parasite species. Finally, because amphibians are ectothermic animals, temperature appears to be the most critical environmental factor that affects co-infections, partly via its influence on amphibian immune function, partly due to its direct effect on the survival and growth of parasites. Besides their importance for our understanding of ecological patterns and processes, detailed knowledge about co-infections is also crucial for the design and implementation of effective wildlife disease management, so that studies concentrating on the identified gaps in our understanding represent rewarding research avenues.

Symbiotic bracovirus of a parasite manipulates host lipid metabolism via tachykinin signaling.

Parasites alter host energy homeostasis for their own development, but the mechanisms underlying this phenomenon remain largely unknown. Here, we show that Cotesia vestalis, an endoparasitic wasp of Plutella xylostella larvae, stimulates a reduction of host lipid levels. This process requires excess secretion of P. xylostella tachykinin (PxTK) peptides from enteroendocrine cells (EEs) in the midgut of the parasitized host larvae. We found that parasitization upregulates PxTK signaling to suppress lipogenesis in midgut enterocytes (ECs) in a non-cell-autonomous manner, and the reduced host lipid level benefits the development of wasp offspring and their subsequent parasitic ability. We further found that a C. vestalis bracovirus (CvBV) gene, CvBV 9-2, is responsible for PxTK induction, which in turn reduces the systemic lipid level of the host. Taken together, these findings illustrate a novel mechanism for parasite manipulation of host energy homeostasis by a symbiotic bracovirus gene to promote the development and increase the parasitic efficiency of an agriculturally important wasp species.

A novel positive single-stranded RNA virus from the crustacean parasite, Probopyrinella latreuticola (Peracarida: Isopoda: Bopyridae).

A positive, single-stranded RNA virus is identified from the transcriptome of Probopyrinella latreuticola Gissler, 1882; a bopyrid isopod parasite of the Sargassum shrimp, Latreutes fucorum Fabricius, 1789. The viral sequence is 13,098 bp in length (including polyA), encoding four open reading frames (ORF). ORF-1 encodes a polyprotein, with three computationally discernible functional domains: viral methyltransferase; viral helicase; and RNA-directed RNA polymerase. The remaining ORFs encode a transmembrane protein, a capsid protein and a protein of undetermined function. The raw transcriptomic data reveal a low level of background single nucleotide mutations within the data. Comparison of the protein sequence data and synteny with other viral isolates reveals that the greatest protein similarity (<39%) is shared with the Negevirus group, a group that exclusively infects insects. Phylogenetic assessment of the individual polyprotein domains revealed a mixed prediction of phylogenetic origins, suggesting with low confidence that the novel +ssRNA virus could be present in multiple places throughout the individual gene trees. A concatenated approach strongly suggested that this new virus is an early diverging isolate, branching before the Negevirus and Cilevirus groups. Alongside the new isolate are other marine viruses, also present toward the base of the tree. The isopod virosphere, with the addition of this novel virus, is discussed relative to viral genomics/systematics. A great diversity of nege-like viruses appears to be present in marine invertebrate hosts, which require greater efforts for discovery and identification.

Viruses of protozoan parasites and viral therapy: Is the time now right?

Infections caused by protozoan parasites burden the world with huge costs in terms of human and animal health. Most parasitic diseases caused by protozoans are neglected, particularly those associated with poverty and tropical countries, but the paucity of drug treatments and vaccines combined with increasing problems of drug resistance are becoming major concerns for their control and eradication. In this climate, the discovery/repurposing of new drugs and increasing effort in vaccine development should be supplemented with an exploration of new alternative/synergic treatment strategies. Viruses, either native or engineered, have been employed successfully as highly effective and selective therapeutic approaches to treat cancer (oncolytic viruses) and antibiotic-resistant bacterial diseases (phage therapy). Increasing evidence is accumulating that many protozoan, but also helminth, parasites harbour a range of different classes of viruses that are mostly absent from humans. Although some of these viruses appear to have no effect on their parasite hosts, others either have a clear direct negative impact on the parasite or may, in fact, contribute to the virulence of parasites for humans. This review will focus mainly on the viruses identified in protozoan parasites that are of medical importance. Inspired and informed by the experience gained from the application of oncolytic virus- and phage-therapy, rationally-driven strategies to employ these viruses successfully against parasitic diseases will be presented and discussed in the light of the current knowledge of the virus biology and the complex interplay between the viruses, the parasite hosts and the human host. We also highlight knowledge gaps that should be addressed to advance the potential of virotherapy against parasitic diseases.

Viral Diversity of Tick Species Parasitizing Cattle and Dogs in Trinidad and Tobago.

Ticks are vectors of a wide variety of pathogens that are implicated in mild to severe disease in humans and other animals. Nonetheless, the full range of tick-borne pathogens is unknown. Viruses, in particular, have been neglected in discovery efforts targeting tick-borne agents. High throughput sequencing was used to characterize the virome of 638 ticks, including Rhipicephalus microplus (n = 320), Rhipicephalus sanguineus (n = 300), and Amblyomma ovale (n = 18) collected throughout Trinidad and Tobago in 2017 and 2018. Sequences representing nine viruses were identified, including five novel species within Tymovirales, Bunyavirales, Chuviridae, Rhabdoviridae, and Flaviviridae. Thereafter the frequency of detection of viral sequences in individual tick species was investigated.

Disentangling host-parasite-pathogen interactions in a varroa-resistant honeybee population reveals virus tolerance as an independent, naturally adapted survival mechanism.

The ectoparasitic mite, Varroa destructor, is unarguably the leading cause of honeybee (Apis mellifera) mortality worldwide through its role as a vector for lethal viruses, in particular, strains of the Deformed wing virus (DWV) and Acute bee paralysis virus (ABPV) complexes. This multi-level system of host-parasite-pathogen interactions makes it difficult to investigate effects of either the mite or the virus on natural host survival. The aim of this study was to remove confounding effects of varroa to examine the role of virus susceptibility in the enhanced survival of a naturally adapted Swedish mite-resistant (MR) honeybee population, relative to mite-susceptible (MS) honeybees. Caged adult bees and laboratory reared larvae, from varroa-free colonies, were inoculated with DWV and ABPV in a series of feeding infection experiments, while control groups received virus-free food. Virus infections were monitored using RT-qPCR assays in individuals sampled over a time course. In both adults and larvae the DWV and ABPV infection dynamics were nearly identical between MR and MS groups, but MS adults suffered significantly higher mortality than MR adults. Results suggest virus tolerance, rather than reduced susceptibility or virus resistance, is an important component of the natural survival of this honeybee population.

The different faces of mass action in virus assembly.

The spontaneous encapsulation of genomic and non-genomic polyanions by coat proteins of simple icosahedral viruses is driven, in the first instance, by electrostatic interactions with polycationic RNA binding domains on these proteins. The efficiency with which the polyanions can be encapsulated in vitro, and presumably also in vivo, must in addition be governed by the loss of translational and mixing entropy associated with co-assembly, at least if this co-assembly constitutes a reversible process. These forms of entropy counteract the impact of attractive interactions between the constituents and hence they counteract complexation. By invoking mass action-type arguments and a simple model describing electrostatic interactions, we show how these forms of entropy might settle the competition between negatively charged polymers of different molecular weights for co-assembly with the coat proteins. In direct competition, mass action turns out to strongly work against the encapsulation of RNAs that are significantly shorter, which is typically the case for non-viral (host) RNAs. We also find that coat proteins favor forming virus particles over nonspecific binding to other proteins in the cytosol even if these are present in vast excess. Our results rationalize a number of recent in vitro co-assembly experiments showing that short polyanions are less effective at attracting virus coat proteins to form virus-like particles than long ones do, even if both are present at equal weight concentrations in the assembly mixture.

Viruses of parasites as actors in the parasite-host relationship: A "ménage à trois".

The complex parasite-host relationship involves multiple mechanisms. Moreover, parasites infected by viruses modify this relationship adding more complexity to the system that now comprises three partners. Viruses infecting parasites were described several decades ago. However, until recently little was known about the viruses involved and their impact on the resulting disease caused to the hosts. To clarify this situation, we have concentrated on parasitic diseases caused to humans and on how virus-infected parasites could alter the symptoms inflicted on the human host. It is clear that the effect caused to the human host depends on the virus and on the parasite it has infected. Consequently, the review is divided as follows: Viruses with a possible effect on the virulence of the parasite. This section reviews pertinent articles showing that infection of parasites by viruses might increase the detrimental effect of the tandem virus-parasite on the human host (hypervirulence) or decrease virulence of the parasite (hypovirulence). Parasites as vectors affecting the transmission of viruses. In some cases, the virus-infected parasite might facilitate the transfer of the virus to the human host. Parasites harboring viruses with unidentified effects on their host. In spite of recently renewed interest in parasites in connection with their viruses, there still remains a number of cases in which the effect of the virus of a given parasite on the human host remains ambiguous. The triangular relationship between the virus, the parasite and the host, and the modulation of the pathogenicity and virulence of the parasites by viruses should be taken into account in the rationale of fighting against parasites.

Cryptosporidium spp., Giardia lamblia y encephalitozoon intestinalis, oportunistas emergentes / Cryptosporidium spp., Giardia lamblia y encephalitozoon intestinalis emergent opportunists

Es un hecho conocido que las infecciones oportunistas por protozoos y hongos han aumentado en los últimos años, debido especialmente al aumento de las infecciones por VIH. Cryptosporidium spp., Giardia lamblia y Encephalitozoon intestinalis son protozoos y hongo, respectivamente, mundialmente reconocidos como agentes oportunistas emergentes, responsables de brotes epidémicos provocados por la ingestión de agua potable contaminada, incluso después de una correcta desinfección. La ingestión de estos protozoos puede provocar diferentes grados de enfermedad, entre aguda o leve (población sana) hasta situaciones más graves y agresivas, hasta a veces mortales (pacientes inmunocomprometidos y/o inmunodeprimidos). A pesar de ser responsables de muchos brotes epidémicos, su diagnóstico de laboratorio permanece arduo y trabajoso, incluso utilizando las nuevas técnicas desarrolladas en los últimos años. En esta revisión se resumen las consideraciones generales de estos oportunistas emergentes, así como los métodos de diagnóstico más usuales, incluso los más recientes y específicos.

Epidemiological data, regarding parasitic and fungi opportunist infections, have changed in the last years, especially due to HIV infection. Cryptosporidium spp., Giardia lamblia and Encephalitozoon intestinalis are protozoan and fungi, respectively, worldwide known as opportunistic emergent agents, being responsible by epidemic outbreaks after ingestion of contaminated water, even following a correct disinfection treatment. Its ingestion can cause different effects on individuals’ health, from light or acute among the healthy population, to serious, aggressive or even deadly among the immunodepressed or immunocompromised patients. Contaminated water ingestion can result in outbreaks but protozoa laboratory diagnosis still remains very laborious, even after the development of more sensitive and specific techniques in the last years. In this paper, a revision of these emergent opportunists, their main characteristics and diagnostic tools are described, including the most recent and specific techniques.

Adaptive selection on bracovirus genomes drives the specialization of Cotesia parasitoid wasps.

The geographic mosaic of coevolution predicts parasite virulence should be locally adapted to the host community. Cotesia parasitoid wasps adapt to local lepidopteran species possibly through their symbiotic bracovirus. The virus, essential for the parasitism success, is at the heart of the complex coevolutionary relationship linking the wasps and their hosts. The large segmented genome contained in the virus particles encodes virulence genes involved in host immune and developmental suppression. Coevolutionary arms race should result in the positive selection of particular beneficial alleles. To understand the global role of bracoviruses in the local adaptation or specialization of parasitoid wasps to their hosts, we studied the molecular evolution of four bracoviruses associated with wasps of the genus Cotesia, including C congregata, C vestalis and new data and annotation on two ecologically differentiated populations of C sesamie, Kitale and Mombasa. Paired orthologs analyses revealed more genes under positive selection when comparing the two C sesamiae bracoviruses belonging to the same species, and more genes under strong evolutionary constraint between species. Furthermore branch-site evolutionary models showed that 17 genes, out of the 54 currently available shared by the four bracoviruses, harboured sites under positive selection including: the histone H4-like, a C-type lectin, two ep1-like, ep2, a viral ankyrin, CrV1, a ben-domain, a Serine-rich, and eight unknown genes. Lastly the phylogenetic analyses of the histone, ep2 and CrV1 genes in different African C sesamiae populations showed that each gene described differently the individual relationships. In particular we found recombination had happened between the ep2 and CrV1 genes, which are localized 37.5 kb apart on the wasp chromosomes. Involved in multidirectional coevolutionary interactions, C sesamiae wasps rely on different bracovirus mediated molecular pathways to overcome local host resistance.

Fleas and smaller fleas: virotherapy for parasite infections.

Bacteriophages are viruses of bacteria that are used for controlling bacterial food-borne pathogens and have been proposed for more extensive usage in infection control. Protists are now recognised to harbour viruses and virus-like particles. We propose that investigation of their prevalence in parasites be intensified. We also propose that such viruses might be considered for virotherapy to control certain parasite infections of man and animals.

Endobiont viruses sensed by the human host - beyond conventional antiparasitic therapy.

Wide-spread protozoan parasites carry endosymbiotic dsRNA viruses with uncharted implications to the human host. Among them, Trichomonas vaginalis, a parasite adapted to the human genitourinary tract, infects globally ∼250 million each year rendering them more susceptible to devastating pregnancy complications (especially preterm birth), HIV infection and HPV-related cancer. While first-line antibiotic treatment (metronidazole) commonly kills the protozoan pathogen, it fails to improve reproductive outcome. We show that endosymbiotic Trichomonasvirus, highly prevalent in T. vaginalis clinical isolates, is sensed by the human epithelial cells via Toll-like receptor 3, triggering Interferon Regulating Factor -3, interferon type I and proinflammatory cascades previously implicated in preterm birth and HIV-1 susceptibility. Metronidazole treatment amplified these proinflammatory responses. Thus, a new paradigm targeting the protozoan viruses along with the protozoan host may prevent trichomoniasis-attributable inflammatory sequelae.

[Approaches to developing a procedure for mapping water basin regions, by using the parasitological criteria].

The structure of a parasite system is formed and its functioning takes place in qualitatively different environments. The aquatic environment serves as a source of new elements and modules, energy, and information for parasite systems. And the parasite systems, for their part, affect the physical and biological parameters of the environment. Many intestinal infections caused by pathogenic microorganisms generally characterized by an acute disease course are related to a water factor. Such are typhus, typhoids, dysentery, cholera, salmonellosis, virus hepatitis, and others. Many parasitic diseases caused by pathogenic intestinal protistae (lambliasis, amebiasis, balantidiasis), blood parasite protistae (malaria), helminthes (opisthorchiasis, fascioliasis, diphyllobothriasis, cercariosis, pseudoamphistomosis) are also closely related to a water factor. Ascaridiasis, hymenolepiasis, trichocephalosis, and echinococcosis have a less close but still self-evident relationship to a water factor. The clbse relationships of many parasitic diseases to a water factor are also determined by the fact that the life cycles of many parasites necessarily include various intermediate hosts and parasite vectors, such as fishes, mollusks, crustaceans, and insects, which are aquatic organisms at some stages of their life. The results of continuous exposure of people to parasitic diseases are quite similar to the suppressive effects of the environment in the ecologically troublesome regions. The most prognostically useful information is formed while mapping by medical and ecological regions, by employing a combination of current mathematical and cartographical methods. The former include cluster analysis, quartering method, informational logical analysis, which are all described in this article and others. Regional mapping using the parasitological criteria should achieve at least two goals: 1) a scientific one that aids in finding causative connections and to prognosticate a situation; 2) a practical one that assists in developing regional programs for disease control and prevention. It is necessary to use the recommendations described in detail in the article in order to have the maximum results during medical and ecological mapping by the regions with a future goal of obtaining useful prognostic information.