Diagnosis and molecular typing of Enterocytozoon bieneusi: the significant role of domestic animals in transmission of human microsporidiosis

Enterocytozoon bieneusi is an obligate intracellular fungus-like parasite with high genetic diversity among mammalian and avian hosts. Based on polymorphism analysis of the ribosomal internal transcribed spacer (ITS), nearly 500 genotypes were identified within E. bieneusi. Those genotypes form several genetic groups that exhibit phenotypic differences in host specificity and zoonotic potential and probably have varying public health implications. Some of the genotypes in Group 1 (e.g., D, EbpC, and Type IV) and Group 2 (e.g., BEB4, BEB6, I, and J) are the most common ones that infect a variety of hosts including humans and thus are of public health importance. By contrast, those genotypes in other genetic groups (Groups 3-11) are mostly restricted to the hosts from which they were originally isolated, which would have unknown or limited impacts on public health. Advances on diagnosis and molecular typing of E. bieneusi are introduced in this review. Genotype distribution pattern of E. bieneusi in major domestic animal groups (pigs, cattle, sheep, goats, cats, and dogs), the role of those animals in zoonotic transmission of microsporidiosis, and food and water as potential vehicles for transmission are interpreted here as well. This review highlights the importance of including more genetic or epidemiological data obtained in the same geographical areas and using more reliable genetic markers to analyze the actual extent of host specificity in E. bieneusi, for the purpose of fully appreciating zoonotic risks of those domestic animals in close contacts with men and enhancing our understanding of the modes of transmission.

Molecular epidemiology of a fatal sarcoptic mange epidemic in endangered San Joaquin kit foxes (Vulpes macrotis mutica)

Background

In 2013, sarcoptic mange, caused by Sarcoptes scabiei mites, precipitated a catastrophic decline of the formerly stable urban population of endangered San Joaquin kit foxes (Vulpes macrotis mutica) in Bakersfield, California, USA. In 2019, a smaller sarcoptic mange outbreak affected kit foxes 58 km southwest of Bakersfield in the town of Taft, California. To determine whether the Taft outbreak could have occurred as spillover from the Bakersfield outbreak and whether epidemic control efforts must involve not only kit foxes but also sympatric dogs (Canis lupus familiaris), coyotes (Canis latrans), and red foxes (Vulpes vulpes), we evaluated genotypes and gene flow among mites collected from each host species.

Methods

We used 10 Sarcoptes microsatellite markers (SARM) to perform molecular typing of 445 S. scabiei mites collected from skin scrapings from twenty-two infested kit foxes, two dogs, five coyotes, and five red foxes from Bakersfield, Taft, and other nearby cities.

Results

We identified 60 alleles across all SARM loci; kit fox- and red fox-derived mites were relatively monomorphic, while genetic variability was greatest in Bakersfield coyote- and dog-derived mites. AMOVA analysis documented distinct mite populations unique to hosts, with an overall F_ST of 0.467. The lowest F_ST (i.e. closest genetic relationship, F_ST = 0.038) was between Bakersfield and Taft kit fox-derived mites while the largest genetic difference was between Ventura coyote- and Taft kit fox-derived mites (F_ST = 0.843).

Conclusions

These results confirm the close relationship between the Taft and Bakersfield outbreaks. Although a spillover event likely initiated the kit fox mange outbreak, mite transmission is now primarily kit fox-to-kit fox. Therefore, any large-scale population level intervention should focus on treating kit foxes within the city.

Host-specificity factors in plant pathogenic fungi

Fortunately, no fungus can cause disease on all plant species, and although some plant-pathogenic fungi have quite a broad host range, most are highly limited in the range of plant species or even cultivars that they cause disease in. The mechanisms of host specificity have been extensively studied in many plant-pathogenic fungi, especially in fungal pathogens causing disease on economically important crops. Specifically, genes involved in host specificity have been identified during the last few decades. In this overview, we describe and discuss these host-specificity genes. These genes encode avirulence (Avr) proteins, proteinaceous host-specific toxins or secondary metabolites. We discuss the genomic context of these genes, their expression, polymorphism, horizontal transfer and involvement in pathogenesis.

Distribution of host-specific parasites in hybrids of phylogenetically related fish: the effects of genotype frequency and maternal ancestry?

Background

Host specificity is one of the outputs of the coevolution between parasites and their associated hosts. Several scenarios have been proposed to explain the pattern of parasite distribution in parental and hybrid genotypes ranging from hybrid resistance to hybrid susceptibility. We hypothesized that host-parasite co-adaptation limits the infection of host-specific parasites in hybrid genotypes even under the condition of the high frequency of hybrids. The experimental monogenean infection in pure breeds of Blicca bjoerkna and Abramis brama and cross-breeds (the F1 generation of hybrids) under the condition of similar frequencies of pure and hybrid genotypes was investigated. We also examined the potential effect of the maternal origin of hybrids (potential co-adaptation at the level of mitochondrial genes) on monogenean abundance.

Methods

Pure breeds of two cyprinids and two cross-breeds (one with B. bjoerkna, the next with A. brama in the maternal positions) were exposed to infection by monogeneans naturally occurring in B. bjoerkna and A. brama. The experiment was run under similar frequencies of the four breed lines.

Results

We showed similar levels of monogenean infection in B. bjoerkna and A. brama. However, each species harboured specific monogenean fauna. Hybrids harboured all monogenean species specifically infecting one or the other species. Monogenean infection levels, especially those of Dactylogyrus specific to A. brama, were lower in hybrids. For the majority of host-specific parasites, there was no effect of the maternal origin of hybrids on monogenean abundance. Asymmetry was found in the distribution of specific parasites in favour of specialists of B. bjoerkna in the monogenean communities of hybrids.

Conclusions

Our results indicate that the maternal mtDNA of hybrids is not an important predictor of host-specific monogenean infection, which may suggest that mitochondrial genes are not strongly involved in the coadaptation between monogeneans and their associated hosts. The asymmetry of species-specific parasites suggests similarity between the molecular components of the immune mechanisms in hybrids and B. bjoerkna. Our results revealed a difference between the degree of host-parasite coadaptation in specific parasites of A. brama and the degree of host-parasite coadaptation in specific parasites of B. bjoerkna and their associated hosts.

Review of the global distribution and hosts of the economically important fish parasitic isopod genus Ceratothoa (Isopoda: Cymothoidae), including the description of Ceratothoa springbok n. sp. from South Africa

Fish parasites from the isopod family Cymothoidae have, in recent years, received increased global attention due to both their ecological and economic importance. This is particularly true for the buccal inhabiting genus Ceratothoa Dana, 1852, whose members have been implicated in negatively impacting the health of both farmed and wild-caught fishes. As research on this group increases, so does our understanding of their host specificity and distribution. The aims of this paper were thus to review the current distribution and host records of Ceratothoa and describe a new species, Ceratothoa springbok n. sp. from South Africa. Including the new species described here, there are currently 25 accepted Ceratothoa spp. known from eight of the 12 marine biogeographical realms of the world. The majority of Cymothoidae species are known to occur in the tropical realms, whereas our analyses show that the greatest diversity of Ceratothoa spp. can be found in temperate realms. These results indicate the possibility that Ceratothoa is more diverse in temperate regions. This review also highlights the low diversity of Ceratothoa from the oceans around both North and South America. Current records indicate that species of Ceratothoa parasitise 108 fish species in 76 genera and 41 families. Eleven Ceratothoa spp. demonstrate host specificity up to host genus or family level. Amongst the hosts, members of the Sparidae are parasitised by 13 species of Ceratothoa, making it the host family with the highest diversity of parasites from this genus. The new species, C. springbok n. sp., also parasitises a sparid and was found in the buccal cavity of the carpenter seabream, Argyrozona argyrozona. This new species, the largest of all recorded Ceratothoa (up to 65 mm) and amongst the largest of all Cymothoidae, is characterised by its truncate and ventrally folded frontal margin, pereonite 1 with medial indentations, the wide anterolateral margins of pereonite 1 with an inwardly produced point, and a well-developed carina on the basis of pereopod 7. A key to the southern African Ceratothoa is provided.

Epiphytic and Endophytic Bacteria on Olive Tree Phyllosphere: Exploring Tissue and Cultivar Effect

Variation on bacterial communities living in the phyllosphere as epiphytes and endophytes has been attributed to plant host effects. However, there is contradictory or inconclusive evidence regarding the effect of plant genetics (below the species' level) and of plant tissue type on phyllosphere bacterial community assembly, in particular when epiphytes and endophytes are considered simultaneously. Here, both surface and internal bacterial communities of two olive (Olea europaea) cultivars were evaluated in twigs and leaves by molecular identification of cultivable isolates, with an attempt to answer these questions. Overall, Proteobacteria, Actinobacteria and Firmicutes were the dominant phyla, being epiphytes more diverse and abundant than endophytes. Host genotype (at cultivar level) had a structuring effect on the composition of bacterial communities and, in a similar way, for both epiphytes and endophytes. Plant organ (leaf vs. twig) control of the bacterial communities was less evident when compared with plant genotype and with a greater influence on epiphytic than on endophytic community structure. Each olive genotype/plant organ was apparently selective towards specific bacterial operational taxonomic units (OTUs), which may lead to specific feedbacks on fitness of plant genotypes. Bacterial recruitment was observed to happen mainly within epiphytes than in endophytes and in leaves as compared with twigs. Such host specificity suggested that the benefits derived from the plant-bacteria interaction should be considered at genetic levels below the species.

Distinct adaptations of a gametocyte ABC transporter to murine and human Plasmodium parasites and its incompatibility in cross-species complementation

Parasites of the genus Plasmodium infect a wide range of mammalian hosts including humans, primates, bats and arboreal rodents. A hallmark of Plasmodium spp. is the very narrow host range, indicative of matching parasite-host coevolution. Accordingly, their respective genomes harbour many unique genes and gene families that typically encode proteins involved in host cell recognition and remodelling. Whether and to what extent conserved proteins that are shared across Plasmodium spp. also exert distinct species-specific roles remains largely untested. Here, we present detailed functional profiling of the female gametocyte-specific ATP-binding cassette transporter gABCG2 in the murine parasite Plasmodium berghei and compare our findings with data from the orthologous gene in the human parasite Plasmodium falciparum. We show that P. berghei gABCG2 is female-specific and continues to be expressed in zygotes and ookinetes. In contrast to a distinct localization to Iipid-rich gametocyte-specific spots as observed in P. falciparum, the murine malaria parasite homolog is found at the parasite plasma membrane. Plasmodium berghei lacking gABCG2 displays fast asexual blood-stage replication and increased proportions of female gametocytes, consistent with the corresponding P. falciparum knock-out phenotype. Strikingly, cross-species replacement of gABCG2 in either the murine or the human parasite did not restore normal growth rates. The lack of successful complementation despite high conservation across Plasmodium spp. is an indicator of distinct adaptations and tight parasite-host coevolution. Hence, incompatibility of conserved genes in closely related Plasmodium spp. might be more common than previously anticipated.

Identification of reliable marker genes for the detection of canine fecal contamination in sub-tropical Australia

Animal fecal contamination in aquatic environments is a major source of zoonotic diseases in humans. While concerns are focused on livestock, companion animals such as dogs can also be a source of a wide range of zoonotic pathogens. Therefore, detection of dog or canine fecal contamination in aquatic environments is important for mitigating risks. In this study, host-sensitivity and specificity of four canine fecal-associated marker genes were evaluated by analyzing 30 canine and 240 non-canine fecal samples. The application of these markers was also tested in water from an urban river under dry weather conditions. The host sensitivity values of the Bacteroides BacCan-UCD, DogBact, DF113 and DF418 were 1.00, 0.90, 0.83, and 0.90, respectively. The host specificity value of the BacCan-UCD, DogBact, DF113 and DF418 were 0.87, 0.98, 0.83, and 0.41, respectively. The mean concentrations of DF418 were highest (7.82 ± 1.13 log₁₀ gene copies (GC)/g of feces) followed by BacCan-UCD (7.61 ± 1.06 log₁₀ GC/g) and DogBact (7.15 ± 0.92 log₁₀ GC/g). The mean concentration of DF113 (5.80 ± 1.25 log₁₀ GC/g) was 1.5 to 2.5 orders of magnitude lower than the other marker genes. The DogBact marker gene was not detected in any other animal feces other than a small number of untreated sewage samples. The BacCan-UCD marker gene cross-reacted with cat, chicken, and pig fecal samples, while the DF113 marker gene cross-reacted with cat, chicken, cattle fecal and untreated sewage samples. The DF418 marker gene was detected in all sewage and animal feces and deemed not suitable for canine fecal contamination tracking in sub-tropical Australia. Canine fecal contamination was infrequently detected in environmental water samples. Based on the results obtained in this study, we recommend that at least two canine feces-associated marker genes should be used in field studies.

Phylogenetic relationships among Toxocara spp. and Toxascaris sp. from different regions of the world

Toxocara and Toxascaris are parasitic nematodes that infect canids and felids although species of the genus Toxocara also infect humans. This work aimed to establish the phylogenetic and phylogeographic relationship between specimens of T. canis, T. cati, T. malaysiensis and Toxascaris leonina and to evaluate the degree of host specificity. In total, 437 samples (adults and pools of eggs) were collected from canids and felids from eight countries. Parasites were identified by morphology, PCR linked Restriction Fragment Length Polymorphism (PCR-RFLP) and partial sequencing of the mitochondrial gene cox1. Phylogenetic trees were constructed and genetic distance among isolates was estimated. Based on the molecular characterization all worms were identified in agreement with their respective hosts with the exception of three samples; two from cats and one from dogs identified as T. canis and T. cati, respectively. There was no clear geographical clustering of the samples despite this study including parasites from three continents. This is the first study, to our knowledge, to use molecular methods to identify T. canis in cats and T. cati in dogs with host specificity being the most common finding. Our developed PCR-RFLP method was found to be a facile and reliable method for identifying Toxocara species.

Cryptosporidium hominis infections in non-human animal species: revisiting the concept of host specificity

Parasites in the genus Cryptosporidium, phylum Apicomplexa, are found worldwide in the intestinal tract of many vertebrate species and in the environment. Driven by sensitive PCR methods, and the availability of abundant sequence data and reference genomes, the taxonomic complexity of the genus has steadily increased; 38 species have been named to date. Due to its public health importance, Cryptosporidium hominis has long attracted the interest of the research community. This species was initially described as infectious to humans only. This perception has persisted in spite of an increasing number of observations of natural and experimental infections of animals with this species. Here we summarize and discuss this literature published since 2000 and conclude that the host range of C. hominis is broader than originally described. The evolving definition of the C. hominis host range raises interesting questions about host specificity and the evolution of Cryptosporidium parasites.

Morphology, molecular characterization, and virulence of Beauveria pseudobassiana isolated from different hosts

Beauveria pseudobassiana has great potential for use in the management of various insect pests. In the present study, we aimed to explore the the virulence of B. pseudobassiana isolated from a diversity of hosts to Bombyx mori and Tenebrio molitor larvae. To this end, 15B. pseudobassiana isolates from 10 different geographical locations were identified based on morphological characteristics and molecular data. The phylogenetic positions of the isolates were evaluated according to morphological features and phylogenetic inferences based on six loci (nrSSU, nrLSU, TEF, RPB1, RPB2 and Bloc). In addition to growth in soil, the B. pseudobassiana isolates in our study were isolated from a wide host range that extended to 5 orders, 11 families, and 14 species. Moreover, anamorphically typified B. pseudobassiana was grown for the first time from teleomorph stromata. Pathogenicity of the B. pseudobassiana isolates from the different hosts was determined with two bioassays using B. mori and T. molitor larvae. The results indicated that mortality of B. mori caused by the lepidopteran isolates was significantly higher than that of isolates from other hosts, and virulence of the coleopteran isolates to T. molitor was significantly higher than that of isolates from other hosts. The host specificity of B. pseudobassiana should be studied in more detail before future consideration of isolates for use in biological control of pests.

Investigations into the carrier-state of Theileria sp. (buffalo) in cattle

The Theileria are apicomplexan parasites transmitted by ticks to vertebrate hosts. Most Theileria species exhibit some form of host or vector specificity, since under endemic conditions only a limited number of tick species act as vectors and not all vertebrate hosts are able to maintain a persistent carrier state. Data for Theileria sp. (buffalo) suggest host specificity for African buffalo (Syncerus caffer). However, T. sp. (buffalo) infections in cattle co-grazing with African buffalo have been reported in Kenya and schizonts were cultured from these infected cattle, raising questions regarding host specificity. A Corridor disease outbreak in 2013 on a ranch in South Africa where cattle co-grazed with Theileria parva and T. sp. (buffalo) infected buffalo presented the opportunity to investigate the possible carrier-state of T. sp. (buffalo) in cattle using real-time PCR analysis. Almost all buffalo (n = 19, 95%) were infected with T. sp. (buffalo) and showed CP values (22-20) indicative of high parasitemia similar to that observed for buffalo in endemic areas. Conversely, only ~14-27% cattle (n = 69, 100, 96) were positive with CP values (31-40) suggesting low parasitemia and a carrier state epidemiology different from African buffalo. Long term monitoring of T. sp. (buffalo) positive cattle showed that most cattle lost their parasitemia or presented fluctuating parasitemia around the PCR assay detection limit. A single splenectomized animal showed a persistent carrier state. The general trends and epidemiology observed in cattle infected with T. sp. (buffalo) are similar to that seen for buffalo-adapted T. parva, for which a defined carrier state in cattle has not yet been proven. The study suggests that cattle may be infected by T. sp. (buffalo) but are not definitive hosts that play an important part in the epidemiology of this parasite.

The diversity of microsporidian parasites infecting the Holarctic amphipod Gammarus lacustris from the Baikal region is dominated by the genus Dictyocoela

Microsporidia are a highly diverse group of single-celled eukaryotic parasites related to fungi and infecting hosts belonging to all groups of eukaryotes, including some protists, invertebrate and vertebrate animals. We investigated the diversity of microsporidia in the Holarctic amphipod species Gammarus lacustris from mostly, but not limited to, water bodies in the Lake Baikal region. Ribosomal DNA sequencing and host transcriptome sequencing data from various works show that this species is predominantly infected by representatives of the genus Dictyocoela and probably has some features underlying this specific interaction.

Diversity and microhabitat associations of Labyrinthula spp. in the Indian River Lagoon System

Seagrasses create foundational habitats in coastal ecosystems. One contributing factor to their global decline is disease, primarily caused by parasites in the genus Labyrinthula. To explore the relationship between seagrass and Labyrinthula spp. diversity in coastal waters, we examined the diversity and microhabitat association of Labyrinthula spp. in 2 inlets on Florida's Atlantic Coast, the Indian River Lagoon (IRL) and Banana River. We used amplicon-based high throughput sequencing with 2 newly designed primers to amplify Labyrinthula spp. from 5 seagrass species, water, and sediments to determine their spatial distribution and microhabitat associations. The SSU primer set identified 12 Labyrinthula zero-radius operational taxonomic units (ZOTUs), corresponding to at least 8 putative species. The ITS1 primer set identified 2 ZOTUs, corresponding to at least 2 putative species. Based on our phylogenetic analyses, which include sequences from previous studies that assigned seagrass-related pathogenicity to Labyrinthula clades, all but one of the ZOTUs that we recovered with the SSU primers were from non-pathogenic species, while the 2 ZOTUs recovered with the ITS1 primers were from pathogenic species. Some of the ZOTUs were widespread across the sampling sites and microhabitats (e.g. SSU ZOTU_10), and most were present in more than one site. Our results demonstrate that targeted metabarcoding is a useful tool for examining the relationships between seagrass and Labyrinthula diversity in coastal waters.

Parasite-host specificity: A cross-infection study of the parasite Ophryocystis elektroscirrha

Many parasites are constrained to only one or a few hosts, showing host specificity. It remains unclear why some parasites are specialists and other parasites are generalists. The parasite Ophryocystis elektroscirrha (OE) is a neogregarine protozoan thought to be restricted to monarch butterflies, Danaus plexippus (Nymphaliae) and D. gilippus. Recently, we found OE-like spores in other Lepidoptera, specifically in three noctuid moths: Helicoverpa armigera, H. assulta and H. punctigera, as well as another nymphalid, Parthenos sylvia. To our knowledge, this is the first report of OE-like parasite infections in species other than the genus Danaus. In sequencing 558 bp of 18S rRNA, we found the genetic similarity between OE from D. plexippus and OE-like parasite from the moths H. armigera and H. punctigera to be 95.2%. When we conducted cross-species infection experiments, we could not infect the moths with OE from D. plexippus, but OE-like parasite from H. armigera did infect D. plexippus and a closely related moth species Heliothis virescens. Interestingly, we did not find the OE-like parasite in the H. armigera population from Spain. Inter-population infection experiments with H. armigera demonstrated a higher sensitivity to OE-like infection in the population from Spain compared to the populations from Australia and China. These results suggest geographic variation in OE-like susceptibility and coevolution between parasite and host. Our findings give important new insights into the prevalence and host specificity of OE and OE-like parasites, and provide opportunities to study parasite transmission over spatial and temporal scales.

Prevalence and multilocus analysis of Giardia duodenalis in racehorses in China

Giardia duodenalis is a zoonotic intestinal parasite infecting humans and mammals worldwide. In this study, we evaluated the prevalence of G. duodenalis in racehorses in China and genetically characterized it. In total, 621 fecal samples were collected from racehorses at 17 equestrian clubs in 15 cities in China. Forty-eight (7.7%) animals from 11 equestrian clubs were positive for G. duodenalis of assemblages A (n = 10), B (n = 36), and E (n = 2), based on the small subunit ribosomal RNA (SSU rRNA) gene. Statistically significant differences in the prevalence of this parasite were detected among the different equestrian clubs (χ² = 49.55, df = 16, p < 0.01), whereas no significant differences were detected according to age (χ² = 0.64, df = 1, p > 0.05) or sex (χ² = 1.41, df = 2, p > 0.05). The G. duodenalis-positive samples were further subtyped based on three other genes, which identified 5, 4, and 4 genotypes at the triose phosphate isomerase (tpi), glutamate dehydrogenase (gdh), and β-giardin (bg) loci, respectively. Subassemblage BIV was the predominant genotype. A phylogenetic analysis of the concatenated sequences of subassemblage BIV showed that the multilocus genotypes from the horses were genetically different from those of humans and nonhuman primates, indicating the evolution of host separation in G. duodenalis subassemblage BIV. Our study extends our understanding of the transmission of G. duodenalis between animals and humans.

Feeding intensity of insect herbivores is associated more closely with key metabolite profiles than phylogenetic relatedness of their potential hosts

Determinants of the host ranges of insect herbivores are important from an evolutionary perspective and also have implications for applications such as biological control. Although insect herbivore host ranges typically are phylogenetically constrained, herbivore preference and performance ultimately are determined by plant traits, including plant secondary metabolites. Where such traits are phylogenetically labile, insect hervivore host ranges are expected to be phylogenetically disjunct, reflecting phenotypic similarities rather than genetic relatedness among potential hosts. We tested this hypothesis in the laboratory with a Brassicaceae-specialized weevil, Ceutorhynchus cardariae Korotyaev (Coleoptera: Curculionidae), on 13 test plant species differing in their suitability as hosts for the weevil. We compared the associations between feeding by C. cardariae and either phenotypic similarity (secondary chemistry—glucosinolate profile) or genetic similarity (sequence of the chloroplast gene ndhF) using two methods—simple correlations or strengths of association between feeding by each species, and dendrograms based on either glucosinolates or ndhF sequence (i.e., a phylogram). For comparison, we performed a similar test with the oligophagous Plutella xylostella (L.) (Lepidoptera: Plutellidae) using the same plant species. We found using either method that phenotypic similarity was more strongly associated with feeding intensity by C. cardariae than genetic similarity. In contrast, neither genetic nor phenotypic similarity was significantly associated with feeding intensity on the test species by P. xylostella. The result indicates that phenotypic traits can be more reliable indicators of the feeding preference of a specialist than phylogenetic relatedness of its potential hosts. This has implications for the evolution and maintenance of host ranges and host specialization in phytophagous insects. It also has implications for identifying plant species at risk of nontarget attack by potential weed biological control agents and hence the approach to prerelease testing.

Chemical Deception and Structural Adaptation in Microdon (Diptera, Syrphidae, Microdontinae), a Genus of Hoverflies Parasitic on Social Insects

Various organisms, especially arthropods, are able to live as parasites in ant nests and to prey upon ant broods without eliciting any aggressive behaviour in the hosts. Understanding how these intruders are able to break the ants' communication codes in their favour represents a challenging and intriguing evolutionary question. We studied the chemical strategies of three European hoverfly species, Microdon mutabilis (parasitic on Formica cunicularia), M. analis (parasitic on Lasius emarginatus) and M. devius (parasitic on L. distinguendus). The peculiar slug-like larvae of these three species live inside ant nests feeding upon their broods. Gas chromatography-mass spectrometry analyses show that: 1) these parasites mimic the host brood rather than the ant workers, although each differs distinctly in the extent of chemical mimicry; 2) isolation experiments indicate that after 14 days the responsible cuticular hydrocarbons (CHCs) are not passively acquired but synthesized by the fly larvae. Additionally, Microdon larvae show an array of protective structural features, such as a thick and multi-layered cuticle, retractable head, dome-shaped tergum and a flat and strongly adhesive "foot" (sternum). This combination of protective chemical and structural features represents a successful key innovation by Microdon species, and one that may facilitate host switching. The results of a preliminary adoption analysis confirm that Microdon larvae of at least some species can readily be accepted by different species of ants.

Morphological comparison of genetically differentiated Polymorphus cf. minutus types

In the present study, we analyzed the morphology of three genetic types of the bird-infecting acanthocephalan Polymorphus cf. minutus (PspT1, PspT2, PspT3), mainly based on the cystacanth-stage obtained from amphipods (Gammarus fossarum, Gammarus pulex, Gammarus roeselii, Echinogammarus spp.). Males and females were pooled as there was no considerable difference between the sexes concerning the hook measurements. Additionally, we conducted a laboratory infection of one domestic duck for each Polymorphus type, to compare their performance and localization in this host species, and to obtain adult specimens for morphological comparison. The recovery rate from the ducks 4 weeks after infection was 16% for PspT1, 23.8% for PspT2, and 25% for PspT3. The adult worms were gravid, and the females contained mature eggs. Hook size did not differ considerably between cystacanths and adults of the respective type. The three Polymorphus types could be distinguished based on the cystacanth stage by a linear discriminant analysis that included hook measurements, proboscis length, proboscis width, and number of longitudinal hook rows and hooks per row. Furthermore, PspT3 was more different from PspT1 and PspT2 than the latter types from each other. Mainly the number of longitudinal hook rows differed in PspT3 from the existing descriptions of P. minutus (mainly 14 vs. mainly 16 rows). Potentially, PspT3 could be a non-indigenous parasite that was introduced with G. roeselii and that adapted to use the indigenous G. pulex as a host, while PspT2 might have been introduced to central Europe together with Echinogammarus spp.

Insect trypanosomatids in Papua New Guinea: high endemism and diversity

The extreme biological diversity of Oceanian archipelagos has long stimulated research in ecology and evolution. However, parasitic protists in this geographic area remained neglected and no molecular analyses have been carried out to understand the evolutionary patterns and relationships with their hosts. Papua New Guinea (PNG) is a biodiversity hotspot containing over 5% of the world's biodiversity in less than 0.5% of the total land area. In the current work, we examined insect heteropteran hosts collected in PNG for the presence of trypanosomatid parasites. The diversity of insect flagellates was analysed, to our knowledge for the first time, east of Wallace's Line, one of the most distinct biogeographic boundaries of the world. Out of 907 investigated specimens from 138 species and 23 families of the true bugs collected in eight localities, 135 (15%) were infected by at least one trypanosomatid species. High species diversity of captured hosts correlated with high diversity of detected trypanosomatids. Of 46 trypanosomatid Typing Units documented in PNG, only eight were known from other geographic locations, while 38 TUs (~83%) have not been previously encountered. The widespread trypanosomatid TUs were found in both widely distributed and endemic/sub-endemic insects. Approximately one-third of the endemic trypanosomatid TUs were found in widely distributed hosts, while the remaining species were confined to endemic and sub-endemic insects. The TUs from PNG form clades with conspicuous host-parasite coevolutionary patterns, as well as those with a remarkable lack of this trait. In addition, our analysis revealed new members of the subfamilies Leishmaniinae and Strigomonadinae, potentially representing new genera of trypanosomatids.

Evaluation of the rust fungus Puccinia rapipes for biological control of Lycium ferocissimum (African boxthorn) in Australia: Life cycle, taxonomy and pathogenicity

Fungal plant pathogens are increasingly recognised as being among the most effective and safe agents in classical weed biological control programs worldwide. Suitability of the rust fungus P. rapipes as a classical biological control agent for Lycium ferocissimum (African boxthorn) in Australia was assessed using a streamlined agent selection framework. Studies with P. rapipes were undertaken to elucidate its life cycle, confirm its taxonomic placement and determine its pathogenicity to L. ferocissimum and seven closely-related Solanaceae species that occur in Australia. Field surveys in the native range of South Africa, experiments in a containment facility in Australia and DNA sequencing confirmed that P. rapipes is macrocyclic and autoecious, producing all five spore stages on L. ferocissimum. The stages not previously encountered, spermogonia and aecia, are described. Sequencing also confirmed that P. rapipes is sister to Puccinia afra, in the 'Old World Lineage' of Puccinia species on Lycieae. Two purified isolates of the fungus, representing the Eastern and Western Cape distributions of P. rapipes in South Africa, were cultured in the containment facility for use in pathogenicity testing. L. ferocissimum and all of the Lycium species of Eurasian origin tested ‒ Lycium barbarum (goji berry), Lycium chinense (goji berry 'chinense') and Lycium ruthenicum (black goji berry) - were susceptible to both isolates of P. rapipes. The Australian native L. australe and three more distantly related species in different genera tested were resistant to both isolates. The isolate from the Western Cape was significantly more pathogenic on L. ferocissimum from Australia, than the Eastern Cape isolate. Our results indicate that P. rapipes may be sufficiently host specific to pursue as a biological control agent in an Australian context, should regulators be willing to accept damage to the Eurasian goji berries being grown, albeit to a limited extent, in Australia.

Validation of the Chemotaxis of Plant Parasitic Nematodes Toward Host Root Exudates

Plant parasitic nematodes (PPN) are microscopic soil herbivores that cause damage to many economic crops. For the last century, it has been proposed that chemotaxis is the primary means by which PPN locate host plant roots. The identities and modes of action of chemoattractants that deliver host-specific messages to PPN, however, are still elusive. In this study, a unique multidimensional agar-based motility assay was developed to assess the impacts of root exudates on the short-range motility and orientation of PPN. Three PPN (Rotylenchulus reniformis, Meloidogyne incognita and Heterodera glycines) and root exudates from their respective host and non-host plants (cotton, soybean, and peanut) were used to validate the assay. As predicted, R. reniformis and M. incognita were attracted to root exudates of cotton and soybean (hosts), but not to the exudates of peanut (non-host). Likewise, H. glycines was attracted to soybean (host) root exudates. These results underpinned the intrinsic roles of root exudates in conveying the host specificity of PPN. In particular, PPN selectively identified and targeted to hydrophilic, but not hydrophobic, fractions of root exudates, indicating that groundwater should be an effective matrix for chemotaxis associated with PPN and their host plant interactions.

Genomic content of chemosensory genes correlates with host range in wood-boring beetles (Dendroctonus ponderosae, Agrilus planipennis, and Anoplophora glabripennis)

Background

Olfaction and gustation underlie behaviors that are crucial for insect fitness, such as host and mate selection. The detection of semiochemicals is mediated via proteins from large and rapidly evolving chemosensory gene families; however, the links between a species’ ecology and the diversification of these genes remain poorly understood. Hence, we annotated the chemosensory genes from genomes of select wood-boring coleopterans, and compared the gene repertoires from stenophagous species with those from polyphagous species.

Results

We annotated 86 odorant receptors (ORs), 60 gustatory receptors (GRs), 57 ionotropic receptors (IRs), 4 sensory neuron membrane proteins (SNMPs), 36 odorant binding proteins (OBPs), and 11 chemosensory proteins (CSPs) in the mountain pine beetle (Dendroctonus ponderosae), and 47 ORs, 30 GRs, 31 IRs, 4 SNMPs, 12 OBPs, and 14 CSPs in the emerald ash borer (Agrilus planipennis). Four SNMPs and 17 CSPs were annotated in the polyphagous wood-borer Anoplophora glabripennis. The gene repertoires in the stenophagous D. ponderosae and A. planipennis are reduced compared with those in the polyphagous A. glabripennis and T. castaneum, which is largely manifested through small gene lineage expansions and entire lineage losses. Alternative splicing of GR genes was limited in D. ponderosae and apparently absent in A. planipennis, which also seems to have lost one carbon dioxide receptor (GR1). A. planipennis has two SNMPs, which are related to SNMP3 in T. castaneum. D. ponderosae has two alternatively spliced OBP genes, a novel OBP “tetramer”, and as many as eleven IR75 members. Simple orthology was generally rare in beetles; however, we found one clade with orthologues of putative bitter-taste GRs (named the “GR215 clade”), and conservation of IR60a from Drosophila melanogaster.

Conclusions

Our genome annotations represent important quantitative and qualitative improvements of the original datasets derived from transcriptomes of D. ponderosae and A. planipennis, facilitating evolutionary analysis of chemosensory genes in the Coleoptera where only a few genomes were previously annotated. Our analysis suggests a correlation between chemosensory gene content and host specificity in beetles. Future studies should include additional species to consolidate this correlation, and functionally characterize identified proteins as an important step towards improved control of these pests.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-6054-x) contains supplementary material, which is available to authorized users.

Indel-informed Bayesian analysis suggests cryptic population structure between Plasmodium knowlesi of humans and long-tailed macaques (Macaca fascicularis) in Malaysian Borneo

Plasmodium knowlesi is an important causative agent of malaria in humans of Southeast Asia. Macaques are natural hosts for this parasite, but little is conclusively known about its patterns of transmission within and between these hosts. Here, we apply a comprehensive phylogenetic approach to test for patterns of cryptic population genetic structure between P. knowlesi isolated from humans and long-tailed macaques from the state of Sarawak in Malaysian Borneo. Our approach differs from previous investigations through our exhaustive use of archival 18S Small Subunit rRNA (18S) gene sequences from Plasmodium and Hepatocystis species, our inclusion of insertion and deletion information during phylogenetic inference, and our application of Bayesian phylogenetic inference to this problem. We report distinct clades of P. knowlesi that predominantly contained sequences from either human or macaque hosts for paralogous A-type and S-type 18S gene loci. We report significant partitioning of sequence distances between host species across both types of loci, and confirmed that sequences of the same locus type showed significantly biased assortment into different clades depending on their host species. Our results support the zoonotic potential of Plasmodium knowlesi, but also suggest that humans may be preferentially infected with certain strains of this parasite. Broadly, such patterns could arise through preferential zoonotic transmission of some parasite lineages or a disposition of parasites to transmit within, rather than between, human and macaque hosts. Available data are insufficient to address these hypotheses. Our results suggest that the epidemiology of P. knowlesi may be more complicated than previously assumed, and highlight the need for renewed and more vigorous explorations of transmission patterns in the fifth human malarial parasite.

Possible transmission of Sarcoptes scabiei between herbivorous Japanese serows and omnivorous Caniformia in Japan: a cryptic transmission and persistence?

Background

Two transmission patterns of Sarcoptes scabiei in host mammal communities have been reported based on microsatellite-level genetic studies in the last two decades. While one involves restrictions among different host taxa, the other is associated with predator–prey interactions between different host taxa. In contrast to these observations, the present study reports a possible irregular case of transmission of S. scabiei between herbivorous Japanese serow and omnivorous Caniformia mammals in Japan, though under very weak predator–prey relationships.

Methods

DNA from 93 Sarcoptes mites isolated from omnivorous Caniformia (such as the domestic dog, raccoon dog, raccoon and Japanese marten), omnivorous Cetartiodactyla (wild boar) and herbivorous Cetartiodactyla (Japanese serow) in Japan were analyzed by amplifying nine microsatellite markers. Principal components analyses (PCA), Bayesian clustering analyses using STRUCTURE software, and phylogenetic analyses by constructing a NeighborNet network were applied to determine the genetic relationships among mites associated with host populations.

Results

In all the analyses, the genetic differentiation of Sarcoptes mites from wild boars and Japanese serows was observed. Conversely, considerably close genetic relationships were detected between Caniformia-derived and Japanese serow-derived mites. Because the predator–prey interactions between the omnivorous Caniformia and herbivorous Japanese serow are quite limited and epidemiological history shows at least a 10-year lag between the emergence of sarcoptic mange in Japanese serow and that in Caniformia, the transmission of S. scabiei from Caniformia to Japanese serow is highly suspected.

Conclusions

The close genetic relationships among mites beyond Host–taxon relationships and without obvious predator–prey interactions in Caniformia and Japanese serow deviate from previously reported S. scabiei transmission patterns. This type of cryptic relationship of S. scabiei populations may exist in local mammalian communities worldwide and become a risk factor for the conservation of the remnant and fragmented populations of wild mammals.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3630-5) contains supplementary material, which is available to authorized users.