Biology subjects

Diekmann, I.

Publications and source records attributed to Diekmann, I..

4 recordsLinked to original sources

bioRxiv2026

Detection of Plasmodium infections in macaques from areas endemic for brugian filariasis in Belitung District, Indonesia

Background Malaria caused by Plasmodium knowlesi and lymphatic filariasis caused by Brugia malayi are mosquito-borne infections with non-human primates as reservoirs. P. knowlesi has emerged as a significant cause of human malaria in Southeast Asia over the past two decades. Belitung district, Indonesia, was until recently assumed to have eliminated B. malayi until infections were detected in humans and long-tailed macaques. To investigate whether the local reservoir of B. malayi is also a reservoir for malaria we screened macaques from 4 areas in Belitung for malaria parasites. Methods and findings Blood samples from 163 long-tailed macaques (Macaca fascicularis) that had been tested for B. malayi were examined by quantitative PCR assays specific for Plasmodium spp., P. knowlesi, P. inui, P. coatneyi and P. cynomolgi. A total of 130 macaques (79.8%) tested positive in the pan-Plasmodium qPCR assay. Plasmodium inui was most prevalent (41.7%), followed by P. knowlesi (38.7%), P. coatneyi (24.5%) and P. cynomolgi (13.5%). Multiple species infections, with 2-3 Plasmodium species were detected in 37% of macaques. Notably, 20 (91%) of 22 B. malayi-positive macaques were co-infected with at least one Plasmodium species. We sequenced the complete mitochondrion from 9 samples diagnosed by qPCR as mono-infections. Phylogenetic analysis confirmed 7 as P. knowlesi, and the other two as P. inui and P. coatneyi. Phylogenetic and pairwise analysis revealed that P. knowlesi isolates from Belitung were closely related to each other and to P. knowlesi from humans and monkeys from Thailand, Malaysia and Indonesia. Conclusions Molecular evidence shows high prevalence of zoonotic malaria parasites in macaques from Belitung, emphasizing the risk of human transmission. Increased surveillance, improved diagnostics, and targeted interventions are needed to prevent zoonotic spillover of P. knowlesi as it has been observed for B. malayi in Belitung.

microbiology↗

bioRxiv2026

Mitochondrial genomes of individual microfilariae: Undescribed Dirofilaria-like filariae from Malaysian cats and two filaria species related to Dirofilaria and Mansonella from Indonesian macaques

Three molecularly undescribed filarial species were co-detected, while screening animals for Brugia malayi, the agent of lymphatic filariasis. Single microfilariae (Mf) isolated from blood samples of crab-eating macaques (Macaca fascicularis) from Belitung, Indonesia, and from pet dogs and cats in Sabah, Malaysia, were analyzed. Among 163 macaques, 33 (20.2%) were positive for large Mf (mean length 498.9 {micro}m) similar to Dirofilaria ( Belitung I). One macaque was infected with small Mf (mean length 150.4 {micro}m) ( Belitung II), with a high density of 17,150 Mf/mL. In two cats co-infected with B. malayi, Mf of a Dirofilaria species ( Sabah) with an average length of 299.1 {micro}m were detected. Morphometric analysis of Mf showed distinct differences between these three species and other Mf described in the area. Whole genome amplification and genome sequencing of 24 individual Mf enabled phylogenetic analysis of mitochondrial genomes, and analysis of specific mitochondrial and nuclear barcode regions. The three Mf groups formed distinct clusters and did not match any currently available reference sequence. Cluster Belitung I from macaques formed a sister group to all other Dirofilaria. Cluster Belitung II included bird filariae and primate filariae of the genus Mansonella as close relatives. The cluster Sabah formed a monophyletic group with the zoonotic species D. asiatica and Dirofilaria sp. Thailand. DNA of Wolbachia endobacteria was detected in Mf of Belitung I and Sabah, but not in Belitung II. These findings highlight the limited understanding of filarial diversity in macaques and cats in Asia and underscore the need for a more comprehensive approach that combines morphological and molecular data to identify and assess the pathogenicity and zoonotic potential of these parasites. Author summaryFilarial worms are parasitic nematodes that infect humans and animals and are often transmitted by the same vector mosquito. We identified three molecularly undescribed filarial species while investigating animals as reservoirs for the agent of lymphatic filariasis, Brugia malayi on Belitung Island, Indonesia, and in Sabah, Malaysia. Blood samples were collected from Indonesian macaques and Malaysian pet cats. Out of 163 macaques, 20.2% tested positive for exceptionally large microfilariae (Mf) of an unclassified Dirofilaria-like species (Belitung I). Another filarial species ( Belitung II) with very small Mf, but with a remarkably high density of 17,150 Mf/mL was detected in one macaque. Two cats harbored medium sized Mf of a Dirofilaria species (Sabah). Genetic analysis revealed unique phylogenetic clusters that did not match any reference sequence. Dirofilaria sp. Sabah was closely related to the zoonotic D. asiatica complex, whereas Belitung I clustered as a sister group to Dirofilaria. Belitung II Mf clustered next to but not within the Mansonella spp. cluster. DNA of Wolbachia endobacteria was only detected in Mf of Belitung I and Sabah. These findings highlight the limited understanding of filarial diversity in animals and underscore the need for a comprehensive approach that combines morphological and molecular data to identify and assess the pathogenicity and zoonotic potential of these parasites.

microbiology↗

bioRxiv2025

Cytochrome c oxidase I deep amplicon sequencing for metabarcoding of equine strongyle communities: unexpectedly high Strongylus spp. burden in treated horses

Equines are parasitized by complex communities of Strongylidae (Nematoda) comprising multi-species infections. Currently, the Cyathostominae are most prevalent, while the Strongylus species are only rarely detected. Since eggs and, in most cases, infective larvae cannot be differentiated to species level, with the exception of Strongylus spp., species-specific knowledge of the pathology, epidemiology and ecology of these parasitic nematodes is limited. Reference sequence data for several cyathostomin species are limited or missing. Deep amplicon sequencing of internal transcribed spacer 2 (ITS-2) regions of nematodes has been used in equines previously, although barcoding studies demonstrate a better species resolution for the cytochrome c oxidase subunit I (COI) region. The present study introduces a nemabiome method based on the sequencing of COI fragments. This method was applied to compare third stage larvae, representing strongyle communities, derived from regularly treated (RT) and never treated (NT) equine populations from Brazil, France (only RT), Germany, Ukraine, the UK, and the USA. Samples were predominantly from horses, but some were obtained from Przewalskis horses (Ukraine), donkeys (Germany, Ukraine) and kulans (Ukraine). Most sequence reads (87.7%) were identified to the species level, but unclassified reads occurred more frequently in donkeys and kulans than horses. No obvious difference in species diversity and richness was observed between RT and NT equines. However, there were significant differences in species composition between the RT and NT groups. While Strongylus spp. were significantly more abundant in the NT groups, Cylicocyclus nassatus, Cylicostephanus longibursatus, and Cyathostomum catinatum were more abundant in the RT group, suggesting that strongyle communities in domestic equines may have been shaped by anthelmintic treatments in the last decades. The decreased classification success for reads from non-caballine equines suggests that there are more strongyle species specific for this rarely-investigated group and that additional efforts are needed to improve the sequence database, particularly for these hosts. Author summaryThis study shows that long-term deworming treatments have influenced strongyle nematode communities in equines. Our findings showed that regular deworming does not always reduce species richness and diversity. Noteworthy, we observed that the more pathogenic species such as Strongylus vulgaris and Strongylus edentatus were still present but in low abundance in equines. Due to their low abundance, less sensitive diagnostic methods, such as morphological examination of larval cultures might not detect these species, which would lead to an underestimated threat in equine herds. We applied an effective metabarcoding approach based on a reliable gene marker region to accurately detect these and other strongyle species in equines. The detection of various species was more effective for horse samples than for those from donkeys and kulans. An expansion of the current database that includes more specimens from more rare species obtained from different equine species can improve identification and understanding of these complex multi-species communities in the future. In summary, the study underscores the importance of continuing monitoring equine herds based on sensitive methods such as metabarcoding to evaluate the current nematode communities and to adapt and develop treatment strategies for managing strongyle infections in equines.

microbiology↗

bioRxiv2022

Evaluation of the nemabiome approach for the study of equine strongylid communities

Basic knowledge on the biology and epidemiology of equine strongylid species remains insufficient although it would contribute to the design of better parasite control strategies. Nemabiome is a convenient tool to quantify and to identify species in bulk samples that could overcome the hurdle that cyathostomin morphological identification represents. To date, this approach has relied on the internal transcribed spacer 2 (ITS-2) of the ribosomal RNA cistron and its predictive performance and associated biases both remain unaddressed. This study aimed to bridge this knowledge gap using cyathostomin mock communities and comparing performances of the ITS-2 and a cytochrome c oxidase subunit I (COI) barcode newly developed in this study. The effects of bioinformatic parameters were investigated to determine the best analytical pipelines. Subsequently, barcode predictive abilities were compared across various mock community compositions. The replicability of the approach and the amplification biases of each barcode were estimated. Results were also compared between various types of biological samples, i.e. eggs, infective larvae or adults. Overall, the proposed COI barcode was suboptimal relative to the ITS-2 rDNA region, because of PCR amplification biases, a reduced sensitivity and higher divergence from the expected community composition. Metabarcoding yielded consistent community composition across the three sample types, although infective larvae may remain the most tractable in the field. Additional strategies to improve the COI barcode performances are discussed. These results underscore the critical need of mock communities for metabarcoding purposes.

ecology↗