Detangling the Crosstalk Between Ascaris, Trichuris and Gut Microbiota: What´s Next?

Parasite-microbiota interactions: a pathway to innovative interventions for Chagas disease, leishmaniasis, and ascariasis

Parasitic infections are a major global health challenge, driven in part by complex interactions between parasites, host microbiota, and immune responses. Recent advances in microbiome research highlight the critical role of microbiota in influencing disease outcomes and treatment effectiveness. This review examines how changes in the microbiota impact parasite transmission, disease progression, and responses to treatment, focusing on key parasitic diseases such as Chagas disease, leishmaniasis, and ascariasis. The microbiota can either exacerbate or mitigate disease severity, depending on its composition, providing critical insights for novel therapeutic strategies. Emerging approaches discussed include the use of targeted probiotics, prebiotics, and microbiota-modulating drugs to influence parasite dynamics and enhance conventional therapies. The review also explores the potential of integrating microbiota knowledge into vaccine design and immunotherapy, aiming to develop vaccines that elicit stronger immune responses and identify new therapeutic targets. A multidisciplinary approach is essential for translating these findings into effective clinical solutions, with future research focusing on validating microbiota-based interventions in clinical settings. In conclusion, the interaction between microbiota and parasitic infections presents a promising avenue for innovative therapies, with the potential to significantly improve global health outcomes.

Nematode-bacteria interactions in bovine parasitic otitis

Bovine parasitic otitis poses challenges in diagnosis, treatment and involves various agents, such as bacteria, fungi, mites, and nematodes. This study focused on the nematodes and bacteria isolated from the auditory canals of dairy cattle. A total of twenty samples were collected from dairy cattle in two states of Brazil. The results showed that Metarhabditis freitasi and M. costai nematodes were identified in 75% of samples. Bacterial species from the ear, identified via mass spectrometry, revealed that different strains were present in 65% of the cattle. Mycoplasma spp. were identified in 45% of samples through molecular techniques. Gram-negative bacteria and Mycoplasma spp. were exclusively found in nematode-infected cattle. Furthermore, the bacteria exhibited resistance to multiple antimicrobial classes, and demonstrating multiresistance. Electron microscopy revealed biofilm aggregates on the cuticle of Metarhabditis spp., suggesting a potential role of these nematodes in bacterial migration and interaction with nervous tissue. Thirteen bacterial strains demonstrated biofilm formation ability, indicating their potential pathogenic role. This research highlights the persistent and complex nature of parasitic otitis, emphasizing the significant role of nematode-bacteria associations in its pathogenicity. The presence of resistant strains and biofilm formation underscores the challenges in managing the diagnosis and treatment of bovine parasitic otitis.

In Vitro Filaricidal Properties of Aqueous Extracts of Combretum nigricans (Combretaceae) on Onchocerca ochengi (Onchocercidae)

Aim

Onchocerciasis is an endemic parasitic disease in sub-Saharan Africa that significantly impacts animal and human health. In Northern Cameroon, medicinal plants from the Combretum genus are used for onchocerciasis traditional treatment although there is no scientific evidence of their antifilarial potential. This study evaluates the in vitro macro- and microfilaricidal properties of water extracts from Combretum nigricans in Onchocerca ochengi. Material and Methods. O. ochengi microfilariae and adult male worms were recovered from cowhide fragments. Oxidative stress indicators and motility tests were used to assess the filaricidal impact. Female albino rats were used to test for acute toxicity. The contents of secondary metabolites were quantified.

Results

The bark aqueous extract was more active on macrofilariae at 1 mg/mL for 24 h (100%) than the leaf (63.9%) and root (75%) extracts at the same concentration. Likewise, a stronger microfilaricidal effect was found with this extract at 0.5 mg/mL for 1 h (100%) compared to root and leaf extracts. The dose-response effect with the bark extract gave an inhibitory concentration 50 (IC50) of 351 μg/mL vs. 113 μg/mL for flubendazole after 24 h incubation, while the microfilaricidal efficacy revealed an IC50 of 158.7 μg/mL vs. 54.09 μg/mL for ivermectin after one-hour incubation. Examining stress indicators on parasite homogenates showed that macrofilaricidal activity is associated with a significant increase in nitric oxide, glutathione, and malondialdehyde generation and a decrease in catalase activity. At 2000 mg/kg, rats showed no harm. The phytochemical investigation revealed that the barks contained more phenolic acids, condensed tannins, flavonoids, and saponins than the leaves (p < 0.001).

Conclusion

These findings support C. nigricans' antifilarial activity and identify oxidative stress indicators as prospective treatment targets in O. ochengi. It would be interesting to conduct in vivo studies to understand their antifilarial activity better.

Microbiota and parasite relationship

The diversity of microbiota is different in each person. Many health problems such as autoimmune diseases, diabetes, cardiovascular diseases, and depression can be caused by microbiota imbalance. Since the parasite needs a host to survive, it interacts closely with the microbiota elements. Blastocystis acts on the inflammatory state of the intestine and may cause various gastrointestinal symptoms, on the contrary, it is more important for gut health because it causes bacterial diversity and richness. Blastocystis is associated with changes in gut microbiota composition, the ultimate indicator of which is the Firmicutes/Bacteroidetes ratio. The Bifidobacterium genus was significantly reduced in IBS patients and Blastocystis, and there is a significant decrease in Faecalibacterium prausnitzii, which has anti-inflammatory properties in Blastocystis infection without IBS. Lactobacillus species reduce the presence of Giardia, and the produced bacteriocins prevent parasite adhesion. The presence of helminths has been strongly associated with the transition from Bacteroidetes to Firmicutes and Clostridia. Contrary to Ascaris, alpha diversity in the intestinal microbiota decreases in chronic Trichuris muris infection, and growth and nutrient metabolism efficiency can be suppressed. Helminth infections indirectly affect mood and behavior in children through their effects on microbiota change. The main and focus of this review is to address the relationship of parasites with microbiota elements and to review the data about what changes they cause. Microbiota studies have gained importance recently and it is thought that it will contribute to the treatment of many diseases as well as in the fight against parasitic diseases in the future.

Helminth-host-environment interactions: Looking down from the tip of the iceberg

In 1978, the theory behind helminth parasites having the potential to regulate the abundance of their host populations was formalized based on the understanding that those helminth macroparasites that reduce survival or fecundity of the infected host population would be among the forces limiting unregulated host population growth. Now, 45 years later, a phenomenal breadth of factors that directly or indirectly affect the host-helminth interaction has emerged. Based largely on publications from the past 5 years, this review explores the host-helminth interaction from three lenses: the perspective of the helminth, the host, and the environment. What biotic and abiotic as well as social and intrinsic host factors affect helminths? What are the negative, and positive, implications for host populations and communities? What are the larger-scale implications of the host-helminth dynamic on the environment, and what evidence do we have that human-induced environmental change will modify this dynamic? The overwhelming message is that context is everything. Our understanding of second-, third-, and fourth-level interactions is extremely limited, and we are far from drawing generalizations about the myriad of microbe-helminth-host interactions.Yet the intricate, co-evolved balance and complexity of these interactions may provide a level of resilience in the face of global environmental change. Hopefully, this albeit limited compilation of recent research will spark new interdisciplinary studies, and application of the One Health approach to all helminth systems will generate new and testable conceptual frameworks that encompass our understanding of the host-helminth-environment triad.

Opisthorchis viverrini, Clonorchis sinensis and Opisthorchis felineus liver flukes affect mammalian host microbiome in a species-specific manner

BACKGROUND

Opisthorchis felineus, Opisthorchis viverrini and Clonorchis sinensis are epidemiologically significant food-borne trematodes endemic to diverse climatic areas. O. viverrini and C. sinensis are both recognized to be 1A group of biological carcinogens to human, whereas O. felineus is not. The mechanisms of carcinogenesis by the liver flukes are studied fragmentarily, the role of host and parasite microbiome is an unexplored aspect.

METHODOLOGY/PRINCIPAL FINDINGS

Specific pathogen free Mesocricetus auratus hamsters were infected with C. sinensis, O. viverrini and O. felineus. The microbiota of the adult worms, colon feces and bile from the hamsters was investigated using Illumina-based sequencing targeting the prokaryotic 16S rRNA gene. The analysis of 43 libraries revealed 18,830,015 sequences, the bacterial super-kingdom, 16 different phyla, 39 classes, 63 orders, 107 families, 187 genera-level phylotypes. O. viverrini, a fluke with the most pronounced carcinogenic potential, has the strongest impact on the host bile microbiome, changing the abundance of 92 features, including Bifidobacteriaceae, Erysipelotrichaceae, [Paraprevotellaceae], Acetobacteraceae, Coriobacteraceae and Corynebacteriaceae bacterial species. All three infections significantly increased Enterobacteriaceae abundance in host bile, reduced the level of commensal bacteria in the gut microbiome (Parabacteroides, Roseburia, and AF12).

CONCLUSIONS/SIGNIFICANCE

O. felineus, O. viverrini, and C. sinensis infections cause both general and species-specific qualitative and quantitative changes in the composition of microbiota of bile and colon feces of experimental animals infected with these trematodes. The alterations primarily concern the abundance of individual features and the phylogenetic diversity of microbiomes of infected hamsters.

Metabarcoding of bacteria and parasites in the gut of Apodemus agrarius

BACKGROUND

The striped field mouse Apodemus agrarius is a wild rodent commonly found in fields in Korea. It is a known carrier of various pathogens. Amplicon-based next-generation sequencing (NGS) targeting the 16S ribosomal RNA (rRNA) gene is the most common technique used to analyze the bacterial microbiome. Although many bacterial microbiome analyses have been attempted using feces of wild animals, only a few studies have used NGS to screen for parasites. This study aimed to rapidly detect bacterial, fungal and parasitic pathogens in the guts of A. agrarius using NGS-based metabarcoding analysis.

METHODS

We conducted 18S/16S rDNA-targeted high-throughput sequencing on cecal samples collected from A. agrarius (n = 48) trapped in May and October 2017. Taxa of protozoa, fungi, helminths and bacteria in the cecal content were then identified.

RESULTS

Among the protozoa identified, the most prevalent was Tritrichomonas sp., found in all of the cecal samples, followed by Monocercomonas sp. (95.8% prevalence; in 46/48 samples) and Giardia sp. (75% prevalence; in 36/48 samples). For helminths, Heligmosomoides sp. was the most common, found in 85.4% (41/48) of samples, followed by Hymenolepis sp. (10.4%; 5/48) and Syphacia sp. (25%; 12/48). The 16S rRNA gene analysis showed that the microbial composition of the cecal samples changed by season (P = 0.005), with the linear discriminant analysis effect size showing that in the spring Escherichia coli and Lactobacillus murinus were more abundant and Helicobacter rodentium was less abundant. Helicobacter japonicus was more abundant and Prevotella_uc was less abundant in males. The microbial composition changed based on the Heligmosomoides sp. infection status (P = 0.019); specifically, Lactobacillus gasseri and Lactobacillus intestinalis were more abundant in the Heligmosomoides sp.-positive group than in the Heligmosomoides sp.-negative group.

CONCLUSIONS

This study demonstrated that bacterial abundance changed based on the season and specific parasitic infection status of the trapped mice. These results highlight the advantages of NGS technology in monitoring zoonotic disease reservoirs.