Interactions between Balantidium ctenopharyngodoni and microbiota reveal its low pathogenicity in the hindgut of grass carp

BACKGROUND

Hosts, parasites, and microbiota interact with each other, forming a complex ecosystem. Alterations to the microbial structure have been observed in various enteric parasitic infections (e.g. parasitic protists and helminths). Interestingly, some parasites are associated with healthy gut microbiota linked to the intestinal eubiosis state. So the changes in bacteria and metabolites induced by parasite infection may offer benefits to the host, including protection from other parasitesand promotion of intestinal health. The only ciliate known to inhabit the hindgut of grass carp, Balantidium ctenopharyngodoni, does not cause obvious damage to the intestinal mucosa. To date, its impact on intestinal microbiota composition remains unknown. In this study, we investigated the microbial composition in the hindgut of grass carp infected with B. ctenopharyngodoni, as well as the changes of metabolites in intestinal contents resulting from infection.

RESULTS

Colonization by B. ctenopharyngodoni was associated with an increase in bacterial diversity, a higher relative abundance of Clostridium, and a lower abundance of Enterobacteriaceae. The family Aeromonadaceae and the genus Citrobacter had significantly lower relative abundance in infected fish. Additionally, grass carp infected with B. ctenopharyngodoni exhibited a significant increase in creatine content in the hindgut. This suggested that the presence of B. ctenopharyngodoni may improve intestinal health through changes in microbiota and metabolites.

CONCLUSIONS

We found that grass carp infected with B. ctenopharyngodoni exhibit a healthy microbiota with an increased bacterial diversity. The results suggested that B. ctenopharyngodoni reshaped the composition of hindgut microbiota similarly to other protists with low pathogenicity. The shifts in the microbiota and metabolites during the colonization and proliferation of B. ctenopharyngodoni indicated that it may provide positive effects in the hindgut of grass carp.

The energy metabolism of Balantidium polyvacuolum inhabiting the hindgut of Xenocypris davidi

Anaerobic parasitic ciliates are a specialized group of ciliates that are adapted to anoxic and oxygen-depleted habitats. Among them, Balantidium polyvacuolum, which inhabits the hindgut of Xenocyprinae fishes, has received very limited scientific attention, so the molecular mechanism of its adaptation to the digestive tract microenvironment is still unclear. In this study, transmission electron microscopy (TEM) and single-cell transcriptome analysis were used to uncover the metabolism of B. polyvacuolum. Starch granules, endosymbiotic bacteria, and multiple specialized mitochondrion-related organelles (MROs) of various shapes were observed. The MROs may have completely lost the electron transport chain (ETC) complexes I, III, IV, and V and only retained succinate dehydrogenase subunit A (SDHA) of complex II. The tricarboxylic acid (TCA) cycle was also incomplete. It can be inferred that the hypoxic intestinal environment has led to the specialization of the mitochondria in B. polyvacuolum. Moreover, carbohydrate-active enzymes (CAZymes), including carbohydrate esterases, enzymes with a carbohydrate-binding module, glycoside hydrolases, and glycosyltransferases, were identified, which may constitute evidence that B. polyvacuolum is able to digest carbohydrates and starch. These findings can improve our knowledge of the energy metabolism and adaptive mechanisms of B. polyvacuolum.

Balantidiasis in humans: A systematic review and meta-analysis

Balantioides coli is a protozoan that infects different hosts species, including humans, with zoonotic transmission. The parasite, which lives in the large intestine and in other organs, can lead to serious infections that may culminate in death. Information about human balantidiasis is generally still very scanty. In view of the above, the purpose of this study was to analyze the epidemiological, clinical and laboratory characteristics of human balantidiasis based on a systematic review and meta-analysis. The scientific articles were retrieved from various databases and were subjected to descriptive analyses, chi-squared tests, and summarized on a forest plot and the heterogeneity index (I²). A total of 103 articles were eligible and included in this review. Out of these 103 articles, 75 were clinical case reports and 28 were epidemiological studies, indicating a frequency of 997 (3.98%) people potentially infected with B. coli. The publication dates of the analyzed articles ranged from 1910 to 2020, but the majority (68.9%) were published between 1998 and 2020. A considerable number of these articles were published in South America and Asia, mostly in Brazil and India, respectively. However, in Africa, Ethiopia, was observed the higher number of infected people (47.5%). A significant association (p < 0.05) was identified between proximity to pigs and positivity for B. coli, since more than 16% infected people were in proximity with pigs and/or their excreta. Infection by the protozoan was classified mainly as intestinal, and the predominant symptom was dysentery. Extraintestinal infections were found in 27 individuals, with colonization of the genitourinary tract frequently highlighted. Direct examination (17.2%), followed by an association of direct examination and sedimentation (45.7%), were the most commonly performed parasitological techniques, and the most frequently diagnosed form was trophozoites, corresponding to 22.5% of cases. The most common treatment for parasitized individuals (11.8%) was an association of tetracycline drugs with nitroimidazole derivatives. The articles retrieved, mainly epidemiological ones, used in meta-analysis showed high heterogeneity (I²> 50%, p < 0.05), impairing the retrieval and comparison of results. Some articles were found to provide incomplete information, making it difficult to retrieve and analyze variables. However, this review enabled us to compile and restate factors that appear to be associated with cases of human balantidiasis.

Milk composition varies in relation to the presence and abundance ofBalantidium coli in the mother in captive rhesus macaques (Macaca mulatta)

Primate infants require extensive maternal investment, and lactation is the most expensive aspect of this investment. However, the relationship between maternal condition and milk composition has been largely uninvestigated in primates. To better understand this relationship, I collected mid-lactation milk samples from 46 captive multiparous rhesus macaques (Macaca mulatta) at the Caribbean Primate Research Center, Sabana Seca Field Station, Puerto Rico. The maternal variables assessed were age, weight, weight for crown-rump length (CRL), and presence of parasites. Additionally the analysis included infant age, weight, and sex. Protein concentration in milk showed little interindividual variation, whereas fat had a high variance. Mothers without the lower intestinal parasite Balantidium coli had a significantly higher fat concentration in milk than mothers with B. coli, but other parasite species (Trichuris trichiura and Strongyloides fulleborni) were not associated with milk fat concentration. Females with younger infants had a higher fat concentration in their milk than mothers with older infants; however, the association between B. coli and milk fat remained significant after controlling for infant age. These results, obtained from a well fed captive population, indicate that even small differences among mothers are associated with milk composition.

Prevalence of Cryptosporidium infections in pigs in Aragón (northeastern Spain)

Faecal samples from 620 pigs randomly selected from 27 farms throughout Aragón were examined to determine the prevalence of Cryptosporidium infections. Detection of oocysts was performed using the ethyl-acetate stool concentration method and the modified Ziehl-Neelsen technique. Cryptosporidium parvum oocysts were identified in 136 (21.9%) pigs from 21 (77.8%) farms. Infected animals ranged from 1 to 6 months old and oocysts were not detected in suckling piglets or adults. Infection rates were significantly higher in weaned, 1-2 month old piglets (59.2%) than in fattening, 2-6 month old pigs (34.3%) (P < 0.001). Cryptosporidial infections were asymptomatic in most of the pigs (90.4%) and usually of low intensity, since 92.6% of the infected pigs excreted few oocysts (0-1 oocysts per field at x 200 magnifications). Although 24.1% of weaned and 5.6% of fattening pigs infected by C. parvum had diarrhoea, it was not found to be statistically associated with infection. In fact, infection rates were higher in non-diarrhoeic than in diarrhoeic pigs, in both weaned (64.7% and 46.7%, respectively) and fattening pigs (34.3% and 33.3%).

Invasive balantidiasis presented as chronic colitis and lung involvement

A unique case of chronic balantidiasis is described, presenting with chronic colitis and inflammatory polyposis of the rectum and sigmoid colon and an intrapulmonary mass. Histology of the colonic polyps showed Balantidium coli, and both Aspergillus and Balantidium coli were found in the aspirate of the pulmonary mass. The patient was treated with doxycycline HCl 100 mg/day for 10 days with complete clinical recovery and marked improvement of the endoscopic appearance of the colonic mucosa.