Encephalitozoon cuniculi: Grading the Histological Lesions in Brain, Kidney, and Liver during Primoinfection Outbreak in Rabbits

Occurrence of Encephalitozoon cuniculi and Encephalitozoon hellem in European Wild Rabbits (Oryctolagus cuniculus) in Southern Germany (Bavaria)

Encephalitozoon cuniculi and Encephalitozoon hellem are fungus-related, obligate intracellular pathogens belonging to the microsporidia. Both microorganisms occur in mammals, birds and even humans, thus revealing a zoonotic potential. Knowledge of their relevance in wild rabbits is very limited so far. Thus, the aim of the present study was to investigate the occurrence of E. cuniculi and E. hellem in wild rabbit populations in southern Germany (Bavaria). Therefore, blood and organ samples (brain/kidney) of 158 wild rabbits were investigated by immunofluorescence and PCR-based assays. Antibodies to E. cuniculi were detected in 24 of the 158 (15.2%) wild rabbits, while DNA of E. cuniculi was found in 7 (4.4%) and DNA of E. hellem was found in 3 (1.9%). Sequencing identified E. cuniculi genotype 1. This study provides the first E. cuniculi genotype determination in free-living wild rabbits worldwide and the first evidence of E. hellem in rabbits worldwide. Wild rabbits should, therefore, be regarded as a reservoir for both pathogens and, on the basis of molecular evidence from kidney tissue and presumed urine excretion, also as a source of infection for E. cuniculi for animals and humans.

Diseases of domestic rabbits by purpose; a retrospective study of 2,583 cases received at 4 diagnostic laboratories in California, USA, 2013-2022

Domestic rabbits (Oryctolagus cuniculus) are commonly kept as pets or bred for laboratory investigation, meat, fur production, or a combination of these purposes. We conducted a retrospective study to assess the prevalence of diseases in domestic rabbits according to purpose. We retrieved results of autopsies, biopsies, and cytologies from 2,583 cases received at 4 diagnostic laboratories in California from 2013-2022. Rabbits were classified as pets (2,241; 86.8%), laboratory animals (92; 3.6%), meat-production animals (60; 2.3%), or multipurpose animals (190; 7.4%). A final diagnosis was reached in 2,360 (91.4%) cases and was classified by system, etiology, and type of process. Pet rabbits had the highest median age (5.9 y; vs. 3 y, 0.67 y, and 0.25 y in meat, multipurpose, and laboratory rabbits, respectively), and most of the neoplasms were diagnosed in this group (872 of the total 896 neoplasms in the study; 97.3%), with tumors of the skin, female reproductive tract, and hematolymphoid system being the most common. Laboratory rabbits had a high prevalence of infectious enterotyphlocolitis (40 of 92; 43.4%), and ~45% of those cases were due to opportunistic colibacillosis. Infectious and parasitic pneumonias were common in meat rabbits (18 of 60; 30%); pneumonic pasteurellosis accounted for >60% of those cases. Infectious cholangiohepatitides were common in multipurpose rabbits (61 of 110; 55.5%), with rabbit hemorrhagic disease representing the most common etiology (82.4% of those cases). Our results demonstrate that purpose of use can predict prevalence of disease in rabbits submitted to diagnostic laboratories.

Distribution of M1 and M2 macrophages in cerebral granulomas caused by Encephalitozoon cuniculi

Encephalitozoon cuniculi spores cause severe granulomatous inflammation in the brain where mononuclear cells and macrophages infiltrate. Here, we orally infected New Zealand white rabbits with 1 × 10⁶E. cuniculi viable spores to study the recruitment and localization of macrophages in brain granulomas. At day 30 post-infection, the positive phenotype markers iNOS (M1) and Arg-1 (M2) were located in the periphery and center of granulomas, respectively. Live intracytoplasmic spores were found only in positive Arg-1 cells. This is the first work to describe the recruitment and distribution of M1 and M2 macrophages in the brain granulomas of rabbits infected with E. cuniculi.

Apigeninidin-rich Sorghum bicolor (L. Moench) extracts suppress A549 cells proliferation and ameliorate toxicity of aflatoxin B1-mediated liver and kidney derangement in rats

Sorghum bicolor plant has a high abundance of 3-deoxyanthocyanins, flavonoids and other polyphenol compounds that have been shown to offer numerous health benefits. Epidemiological studies have linked increased intake of S. bicolor to reduced risk of certain cancer types, including lung adenocarcinoma. S. bicolor extracts have shown beneficial effects in managing hepatorenal injuries. This study investigated the cytotoxic potential of three apigeninidin-rich extracts of S. bicolor (SBE-05, SBE-06 and SBE-07) against selected cancer cell lines and their ameliorative effect on aflatoxin B₁ (AFB₁)-mediated hepatorenal derangements in rats. We observed that, among the three potent extracts, SBE-06 more potently and selectively suppressed the growth of lung adenocarcinoma cell line (A549) (IC₅₀ = 6.5 μg/mL). SBE-06 suppressed the expression of STAT3 but increased the expression of caspase 3. In addition, SBE-05, SBE-06 and SBE-07 inhibited oxidative and nitrosative stress, inflammation, and apoptosis and preserved the histoarchitectural networks of the liver and kidney of rats treated with AFB₁. These in vitro and in vivo studies indicate the potential of these cheap and readily accessible extracts for cancer therapy and as chemo-preventive agents in preventing aflatoxin-related health issues.

Tracking microeukaryotic footprint in a peri-urban watershed, China through machine-learning approaches

Microeukaryotes play a significant role in biogeochemical cycling and can serve as bioindicators of water quality in freshwater ecosystems. However, there is a knowledge gap on how freshwater microeukaryotic communities are assembled, especially that how terrestrial microeukaryotes influence freshwater microeukaryotic assemblages. Here, we used a combination of 18S rRNA gene amplicon sequencing and community-based microbial source tracking (MST) approaches (i.e., SourceTracker and FEAST) to assess the contribution of microeukaryotes from surrounding environments (i.e., soils, river sediments, swine wastewater, influents and effluents of decentralized wastewater treatment plants) to planktonic microeukaryotes in the main channel, tributaries and reservoir of a peri-urban watershed, China in wet and dry seasons. The results indicated that SAR (~ 49% of the total communities), Opithokonta (~ 34%), Archaeplastida (~ 9%), and Amoebozoa (~ 2%) were dominant taxa in the watershed. The community-based MST analysis revealed that sewage effluents (7.96 - 21.84%), influents (2.23 - 13.97%), and river sediments (2.56 - 11.71%) were the major exogenous sources of riverine microeukaryotes. At the spatial scale, the downstream of the watershed (i.e., main channel and tributaries) received higher proportions of exogenous microeukaryotic OTUs compared to the upstream reservoirs, while at the seasonal scale, the sewage effluents and influents contributed higher exogenous microeukaryotes to river water in wet season than in dry season. Moreover, the swine and domestic wastewater led to the presence of Apicomplexa in wet season only, implying rainfall runoff may enhance the spread of parasitic microeukaryotes. Taken together, our study provides novel insights into the immigration patterns of microeukaryotes and their dominant supergroups between terrestrial and riverine habitats.

Chronic Infections in Mammals Due to Microsporidia

Microsporidia are pathogenic organism related to fungi. They cause infections in a wide variety of mammals as well as in avian, amphibian, and reptilian hosts. Many microsporidia species play an important role in the development of serious diseases that have significant implications in human and veterinary medicine. While microsporidia were originally considered to be opportunistic pathogens in humans, it is now understood that infections also occur in immune competent humans. Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Enterocytozoon bieneusi are primarily mammalian pathogens. However, many other species of microsporidia that have some other primary host that is not a mammal have been reported to cause sporadic mammalian infections. Experimental models and observations in natural infections have demonstrated that microsporidia can cause a latent infection in mammalian hosts. This chapter reviews the published studies on mammalian microsporidiosis and the data on chronic infections due to these enigmatic pathogens.

Betulinic acid reduces the complications of autoimmune diabetes on the body and kidney through effecting on inflammatory cytokines in C57BL/6 mice

Autoimmune diabetes is one of the most common metabolic diseases with increasing prevalence in the past decades in which pancreatic Langerhans β cells are destroyed and lead to lack of insulin due to increased blood sugar. One of the consequences of diabetes is glomerular disease of the kidney, also called diabetes nephropathy. Different studies have been carried out on the effects of triterpenoids and their medicinal effects on diabetes mellitus. betulinic acid, a pentacyclic triterpenoid of Terpenes, is found in bushes and trees. Its medical effects are also approved by many studies. In this survey, we studied the effect of betulinic acid on diabetic inbred C57BL/6 male mice. They were randomly divided to three groups. Group A: Consisted of healthy mice which received citrate buffer. Group B: Diabetic mice without any treatment and group C: Treated diabetic mice with betulinic acid. The level of blood insulin level, fasting blood glucose, C-peptide, TNF-α, IFN-γ, and IL-1 cytokines were measured and pathologic studies of the kidney were performed. The results showed that betulinic acid could increase insulin and C-peptide, and decrease fasting blood sugar, kidney lesions and TNF-α, IFN-γ, IL-1 in the treated groups. The differences were significant except for IL-1. Betulinic acid through reduction of inflammatory cytokines could have positive effects on inflammatory and autoimmune disease including autoimmune diabetes.

Immunohistochemical localization of TNF-α and IL-4 in granulomas of immunocompetent and immunosuppressed New Zealand white rabbits infected with Encephalitozoon cuniculi

Encephalitozoon cuniculi is a fungi-related, obligate, zoonotic, spore-forming intracellular eukaryotic microorganism. This emerging pathogen causes granulomas to form in the brain and kidneys of infected individuals. The objective of the current study was to detect the distribution of TNF-α- and IL-4-positive cells using immunohistochemistry within these granulomas in both infected immunocompetent (group A) and immunosuppressed (group B) New Zealand white rabbits. In the brain, labeled TNF-α immune cells were mainly located in the granuloma peripheries in group B. Granulomas examined in the kidneys of groups A and B were TNF-α positive, but were significantly different (p < 0.001) when compared with the brain. IL-4-producing immune cells in the brain and kidneys were disseminated within granulomas in groups A and B; however, no significant difference (p > 0.05), was observed. IL-4 positive cells were more numerous in brain sections of group B and differed significantly (p < 0.05) when compared with kidneys. Granulomas were not observed in control animals (groups C and D). In conclusion, we identified TNF-α positive cells in both the brain and kidneys of immunocompetent and immunosuppressed animals; IL-4 positive cells were numerous in the brains of immunosuppressed rabbits; however, in terms of percentage were numerous in the brains of immunocompetent rabbits. Immunosuppression appeared to stimulate a change in the cellular phenotype of Th1- to Th2-like granulomas in the brain and kidneys via an unknown mechanism. Expression of pro- and pre-inflammatory cytokines in microsporidian granulomas suggests a mechanism by which E. cuniculi evades the immune response, causing more severe disease. These results increase our understanding of TNF-α and IL-4-positive cells within the E. cuniculi granuloma microenvironment.

Encephalitozoon cuniculi infection in farmed rabbits in Egypt

BACKGROUND

Encephalitozoon cuniculi is an important microsporidian parasite with zoonotic potential. The present study highlights the impact of encephalitozoonosis on rabbit health in Egypt. Three rabbit farms in Giza, with a total of 16,400 rabbits were investigated due to occurrence of rabbits displaying clinical signs consistent with encephalitozoonosis.

RESULTS

Clinical signs observed during a 4 months observation period in 2018 included vestibular disease, paresis, limb paralysis, cataracts, phacoclastic uveitis, frequent urination, marked decrease in body weight and in some pregnant females, also repeated abortions. The total morbidity rates in adult and young rabbits were 76.7% and 81.5%, respectively. The highest mortality rate was recorded in offspring (12.3%), followed by dams (5.6%), and the lowest recorded mortality rate was in males (0.04%). Post-mortem findings included enteritis, pale enlarged kidneys, congested leptomeninges, focal brain necrosis, and endometrial congestion. Histopathological examination revealed nonsuppurative meningoencephalitis and glial nodules with central necrosis in the brain, vacuolation and necrosis of renal tubular epithelium, and corneal ulceration and ruptured lens capsule with fragmentation of lenticular fibres. E. cuniculi were observed in the brain, retinal ganglion cells, kidneys, and liver. Transmission electron microscopy examination revealed the presence of different developmental stages of E. cuniculi in the brain and kidney. Presence of E. cuniculi was confirmed by conventional polymerase chain reaction using a universal 16S gene for Encephalitozoon spp. followed by sequencing and sequence analysis.

CONCLUSIONS

The presence of E. cuniculi in rabbits was confirmed at three farms in Egypt. Nervous signs and ocular lesions were the most predominant findings in these farms.

Encephalitozoon cuniculi in rabbits: Serological screening and histopathological findings

Serological prevalence of E. cuniculi infection was assessed in 183 rabbits from central Italy. In seropositive deceased rabbits, histopathological lesions were also evaluated. Sera from 118 rabbits from 6 intensive farms, 10 rabbits from 6 family farms, 16 rabbits from a zoo, 30 rabbits from 5 research laboratories and 9 pet rabbits from 9 different owners, were tested by an enzyme-linked immunosorbent assay. Data were statistically analysed. Tissue samples from brain and kidney of 10 deceased rabbits were formalin-fixed and subsequently analysed by histopathology and immunohistochemistry. Anti-E. cuniculi antibodies were found in 129/183 (70.5%) analysed sera. At statistical analysis, E. cuniculi seropositivity was significantly higher (p<0.05) in industrial and zoo rabbits. At histology, different degrees of pathological lesions were found in serological positive (9) deceased animals. In three rabbits deceased after showing neurological signs, the severity of the lesions was interpreted as a likely cause for their death.