Journal of invertebrate pathology最新文献

Entomopathogenic fungi (EPF) are promising biocontrol agents that can also function as plant endophytes, mediating interactions within plant-insect-pathogen systems. Here, we evaluated four EPF isolates, two endemic (Metarhizium brunneum strain GxABT-2 and Metarhizium majus strain GxABT-3) and two reference strains (M. brunneum ARSEF4556 and V275), for their efficacy against the green peach aphid (Myzus persicae) and their ability to limit Beet Mild Yellowing Virus (BMYV) transmission. Concentration-dependent bioassays assessed aphid mortality, fecundity, and post-mortem fungal development, while seed treatments evaluated the endophytic colonization and impact on BMYV establishment. All isolates caused > 80% aphid mortality at the highest concentration (1 × 10⁸ conidia ml^-1), whether applied directly (spray or immersion of aphids) or indirectly (spray or immersion of leaves), with GxABT-2 producing the greatest reduction in fecundity. Three post-mortem developmental stages (melanized, non-sporulating, and sporulating) were primarily observed at lower concentrations (1 × 10⁵ and 1 × 10⁶ conidia ml^-1). Overall, melanization was more frequent with endemic isolates, whereas sporulation predominated in V275 and ARSEF4556 treatments. Endophytically colonized plants exhibited significantly lower BMYV loads, with GxABT-2 being the most effective. These results highlight the potential of endemic Metarhizium spp. as sustainable biocontrol agents in a post-neonicotinoid era and underscore the importance of understanding and isolate-specific variability in plant-fungus interactions for optimizing viral suppression.

Contortylenchus genitalicola is a nematode species belonging to the family Allantonematidae that parasitizes the reproductive organs of Monochamus alternatus. This nematode was first reported in Japan, but the information regarding its occurrence in China remains limited, including parasitic insect species, geographical distribution, and suitable fungi for its reproduction. Here, we determined the nematode taxonomic status by observing its entomoparasitic and mycetophagous morphology and obtained 18S, 28S, and COI sequences. A total of 11 Cerambycid species were inspected, and nematodes were recovered only in M. alternatus and Spondylis buprestoides, with the former being the primary beetle host. Subsequently, M. alternatus were collected from 12 pine forests across 6 provinces, and it was found that M. alternatus distributed in 10 pine forests in 5 provinces were parasitized by this nematode. Among the eight fungal species screened for nematode propagation, isolates Colletotrichum siamense and Sphaeropsis sapinea are suitable fungi for C. genitalicola. Our findings define the beetle hosts and geographical distribution of C. genitalicola in China and confirm the suitable fungal host for nematode reproduction, thereby providing a solid scientific foundation for exploiting this nematode in biological control targeting M. alternatus.

In aquaculture, controlling emerging pathogenic bacteria is crucial, making the search for new antimicrobials a priority. We evaluated the antibacterial activity against Streptococcus iniae under in vitro and in vivo conditions of the bacteriocin Thurincin H (ThurH), recombinantly produced in Bacillus thuringiensis genotype Cry-B-pThur and purified via molecular weight screening. The results show that ThurH is stable in seawater and inhibits the growth of S. iniae by 100% at 70 µg/ml, with a MIC of 35 µg/ml. Bactericidal activity was observed within the first 10 min (16 MIC), eliminating 100% of viable cells. The in vivo assay with Artemia franciscana demonstrated that ThurH is non-toxic at 1000 µg/ml. Challenge tests with A. franciscana at 100 mL (4 artemias/mL) and histological analysis demonstrated the efficacy of ThurH in in vivo trials, improving organism survival with two doses (MIC). These results demonstrate for the first time in an in vivo assay that ThurH has potential as an antimicrobial against S. iniae in aquaculture.

Understanding the evolution of pathogen host range is a challenging problem but one that is important for emerging infections and for biocontrol. Theory predicts that sequential selection in multiple host species should select for broad host range. Using two genotypes of B. thuringiensis we tested whether selection in alternating host environments would produce bacteria with increased virulence in both hosts, relative to bacteria passaged in single host species (fall armyworm, Spodoptera frugiperda or diamondback moth, Plutella xylostella). Since the Cry toxins of B. thuringiensis are public goods that benefit groups of bacteria, not individual cells, we employed a passage design which provided reproductive benefits to groups of pathogens, based on infectivity. Passage of one bacterial genotype (Bt morrisoni) led to the loss of virulence, while the second genotype (Bt galleriae) evolved virulence that was dependent on selection treatment. In contrast to expectation, selection in P. xylostella produced lineages with increases in virulence in both hosts; selection in S. frugiperda led to very low virulence and the alternating host treatment produced intermediate levels of virulence. Modest increases in virulence were accompanied by a reduction in fitness, consistent with a cost of increased investment in virulence factors. In contrast, infection in S. frugiperda selected for cheaters that had reduced investment in Cry toxins and high competitive fitness within hosts. In conclusion, the selection favouring cheaters depended strongly on both host species and bacterial genotype. Importantly, the host (P. xylostella) that favoured cooperation produced mutants with gains in virulence across multiple hosts.

Papua, Indonesia, is an endemic region for malaria where the Anopheles punctulatus group serves as the primary vector. The endosymbiotic bacterium Wolbachia has shown promise as a biocontrol agent by manipulating host reproduction and inhibiting pathogen transmission, yet its presence in Papua's Anopheles mosquitoes remained undocumented. This study aimed to detect and genetically characterize Wolbachia infections in Anopheles punctulatus group mosquitoes collected from Keerom District, Papua. Among 1,071 specimens screened using nested PCR targeting 16S rRNA and wsp, 2.9% tested positive for Wolbachia, with An. punctulatus and An. koliensis showing intra-species infection rates of 4.6% and 2.5%, respectively. Phylogenetic analyses revealed the presence of Wolbachia supergroups A and B, suggesting multiple independent acquisition events. These findings provide preliminary molecular evidence of Wolbachia in Papua's malaria vectors and offer baseline data for evaluating its potential in vector control strategies.

Lithodid crabs constitute a valuable natural resource with commercial interest; however, their health status in South America is scarcely studied. The presence of pathogens may have a negative impact on affected populations, endangering the fishery. This study surveys the symbionts present in populations of the king crab, Lithodes santolla, and the stone/false king crab, Paralomis granulosa, using histology, transmission electronic microscopy, and molecular analyses to characterise various symbionts. The histological and molecular data revealed a wide range of infections in L. santolla, including prokaryotic microorganisms, Areospora rohanae (Microsporidia), apicomplexan gregarines, ciliated protozoans, ectoparasitic crustaceans, and various epibiotic associations. In the case of P. granulosa, apicomplexan gregarines, ciliated protozoans, and various ectoparasites were observed. Molecular analyses confirmed the presence of the microsporidian A. rohanae, occurring at high prevalences (30%) in L. santolla, and some bacterial associations. We use metagenomic tools to extract a partial genome of this parasite to aid in its identification and taxonomic position, which leads us to erect the taxonomic orders Astathelohaniida and Areosporida and further clarify the previously assigned: "Glugeida+". The results of this study represent the first broad survey for symbionts in both king crab species and take us another step forward to a more accurate microsporidian taxonomy.

Solenopsis invicta virus 6 (SINV-6; Cripavirus porteri) is a recently discovered dicistrovirus from the red imported fire ant, Solenopsis invicta. SINV-6 was detected in all stages of S. invicta including eggs, pupae, larvae, adult workers, male and female sexual alates, and queens. Electron microscopic examination of negatively stained samples from particles purified from SINV-6-infected fire ant workers revealed isometric particles with a mean diameter of 34.2 ± 2.1 nm. Field surveys of S. invicta nests in Alachua County, Florida, showed that the virus was present year-round. SINV-6 nest prevalence ranged from 37.5% in February to 100% in November. Among 171 nests surveyed throughout the year and over the 6-year period, 106 (62%) tested positive for SINV-6. Intra-colonial SINV-6 infection incidence and virus titer among worker ants exhibited a positive relationship. SINV-6 exhibited tissue tropism toward the abdomen where > 99% of SINV-6 was detected. Among the major tissues of the abdomen, the alimentary canal (crop, midgut, hindgut) contained 87.6% of SINV-6 with the midgut and hindgut accounting for 58.0 ± 28.7% of the total. Small quantities of SINV-6 were detected in fat body (8.4 ± 0.4%) and Malpighian tubules (4.0 ± 0.4%). SINV-6 infection did not have a significant impact on brood production in S. invicta over a 26-day period when held in the laboratory compared with uninfected control colonies. The host range of SINV-6 appears to be broad with the plus genome strand detected in six species of ants and the honey bee (Apis mellifera).