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.

Variation of the CD4, CD8, and MHC II cell population in granulomas of immunocompetent and immunosuppressed rabbits in Encephalitozoon cuniculi infection.

Encephalitozoon cuniculi (E. cuniculi) is a fungi-related, obligate, zoonotic, spore-forming intracellular eukaryotic microorganism. This emerging pathogen causes granulomas in brain and kidneys of infected individuals. The objective of this study was to detect the distribution of CD4, CD8 and MHCII-positive cells within granulomas in these organs in infected immunocompetent (group A) and infected immunosuppressed (group B) New Zealand white rabbits using immunohistochemistry. In brain, labeled CD4 immune cells were mainly located in the periphery of granulomas in group B. Kidneys of groups A and B, displayed CD4-positive in granulomas and were significant different when compared to brain. CD8 immune cells in brain and kidneys were disseminated in the granulomas in groups A and B; however, no significant difference was observed. MHCII-positive cells were more numerous in brain sections of group B and were significantly different when compared to kidney sections. Granulomas were not observed in control animals of group C and D. In conclusion, we identified CD4-positive cells in both the brain and kidneys of immunocompetent and immunosuppressed animals; CD8-positive cells were more numerous in brain of immunosuppressed rabbits and MHCII cells were more predominant in brain of immunocompetent rabbits. Apparently, the immunosuppression stimulated a change in the cellular phenotype of Th1- to Th2-like granulomas in brain and kidneys by an unknown mechanism. These results increase our understanding of CD4, CD8 and MHCII positive cells within the E. cuniculi granuloma microenvironment and will help in future microsporidian granulomas studies of both immunocompetent and immunosuppressed individuals.

Increased phagocytosis and growth inhibition of Encephalitozoon cuniculi by LPS-activated J774A.1 murine macrophages.

Encephalitozoon cuniculi is an obligate macrophage parasite of vertebrates that commonly infects rodents, monkeys, dogs, birds, and humans. In the present study, we aimed to assess the phagocytosis and intracellular survival of E. cuniculi spores using untreated and lipopolysaccharide (LPS)-activated J774A.1 murine macrophages and assess the macrophage viability. The experimental groups comprised untreated spores, spores killed by heat treatment at 90 °C, and spores killed by treatment with 10% formalin. LPS-activated macrophages significantly increased the phagocytosis of spores and reduced their intracellular growth after 24 and 48 h (P < 0.01); however, after 72 h, we observed an increase in spore replication but no detectable microbicidal activity. These results indicate that LPS activation enhanced E. cuniculi phagocytosis between 24 and 48 h of treatment, but the effect was lost after 72 h, enabling parasitic growth. This study contributes to the understanding of the phagocytosis and survival of E. cuniculi in murine macrophages.

An Alternative Treatment Against Acanthocephala ( Prosthenorchis elegans) in Captive Squirrel Monkeys ( Saimiri sciureus) in Mexico.

We provide the first report of Acanthocephala ( Prosthenorchis elegans) in Mexican non-human primates. There has been no known treatment against this parasite except for surgical removal, and this has been relatively ineffective because of the small juveniles. We report the presence of P. elegans in a captive breeding colony of squirrel monkeys ( Saimiri sciureus) in Mexico, and we describe a successful treatment protocol. Treatment involved 2 steps: oral administration of the drugs loperamide chlorhydrate (0.5 mg/0.9 kg/3 days) and niclosamide (0.2 mg/0.9 kg/3 days) followed by surgical removal of adult worms from the intestine. Fecal examination during treatment revealed live adults but no living juveniles and no eggs. Surgery after 1 wk of treatment revealed the presence of adults and an absence of juvenile parasites. All adults were physically extracted during the surgery. All subjects recovered from surgery within 1 wk.

Disseminated paracoccidioidomycosis in a Southern two-toed sloth (Choloepus didactylus).

A Southern two-toed sloth (Choloepus didactylus), originally acquired from French Guiana, died while maintained in quarantine in a pet store in Monterrey, Mexico. Large yeast cells with multiple buds compatible with Paracoccidioides brasiliensis were observed in disseminated granulomatous lesions in the lungs, liver, spleen and kidney. Transmission electron microscopical examination supported the diagnosis. This is the first report of paracoccidioidomycosis in a two-toed sloth.

Chlorella infection in a sheep in Mexico and minireview of published reports from humans and domestic animals.

Algal infections are rare in humans and domestic animals. Prototheca spp. and Chlorella spp. are among the most commonly reported. Herein, we present a brief review on Chlorella spp. infections and related pathologies and discuss this information including a natural case in a sheep in Mexico with a disseminated form of the disease.

First report of Oxyspirura sp. from a captive fulvous owl (Strix fulvescens) in Mexico.

Nematodes similar to Oxyspirura sp. were recovered from the cornea and nictitating membrane of a fulvous owl (Strix fulvescens). The bird had been captive for several months, but died suddenly. It had no clinical history of prior diseases, including ocular lesions.

Cellular immunity in salmonids infected with the microsporidial parasite Loma salmonae or exposed to non-viable spores.

Following a per os challenge of naive rainbow trout with live spores of Loma salmonae, head kidney mononuclear cells (MNC) in culture were able to proliferate in response to crude soluble parasite extract or intact dead spores. A significant response was seen by week 2 post-exposure and a maximum response developed by week 6 or 8, respectively. During this initial challenge, spore filled cysts developed on the gills of challenged fish, and the cysts ruptured by week 12 as is typical for microsporidial gill disease of salmonids (MGDS). Two weeks following this, fish were re-challenged with live spores, and in these fish an enhanced in vitro proliferative response of MNC was immediately apparent, and spore filled cysts did not develop. In contrast, when naive trout were given dead spores by intraperitoneal injection, the most pronounced proliferative responses of MNC developed earlier (week 2 PE) and the response was greater when cells were incubated in vitro with dead spores rather than with crude soluble extract. When these fish were re-challenged per os with live spores, a heightened proliferation in MNC was observed 4 weeks after this exposure and the fish likewise resisted development of xenomas. In fish infected orally or injected intraperitoneally with spores, a marked increase in the response to the mitogen concanavalin A was seen for 22 weeks post-exposure when compared to controls not receiving any spores.

Predictive modelling of post-onset xenoma growth during microsporidial gill disease (Loma salmonae) of salmonids.

Loma salmonae, an obligate intracellular microsporidian parasite, is the causal agent of microsporidial gill disease of salmon (MGDS), characterized by the production, growth and eventual rupture of spore-filled xenomas. MGDS in farmed chinook salmon remains occult until xenoma rupture, at which time the infected fish respond with intense branchitis and high rates of mortality. The present study showed that in experimentally infected fish the rate of change of xenoma diameter could be modelled through regression analysis, particularly through the period of 4-9 weeks post-infection, yielding the predictive equation: xenoma diameter=-42.9 microns +15.3 microns x (number of weeks post-infection). This provides a tool for diagnosticians to predict the time to xenoma rupture and hence to the initiation of the clinical phase of MGDS.

Ultrastructural study of the late stages of Loma salmonae development in the gills of experimentally infected rainbow trout.

The main objective of this investigation was to examine the ultrastructural features of gills from rainbow trout experimentally infected with Loma salmonae to determine the morphological events that occur during the late stages of development of this parasite. Peripheral distribution of the mature parasites inside round xenomas was observed at weeks 5 and 6 postexposure (PE), but eventually the parasite occupied the entire xenoma. Degenerative changes were observed only in immature parasites at week 7 PE, and eventually an inflammatory reaction with a cellular infiltration was directed against mature spores. Round, flattened, and irregular shaped xenomas were observed at week 8 PE. The round xenomas showed a severe inflammatory response with disintegration of the xenoma membrane. This event was accompanied by eversion of polar tubes within the attacked xenoma and by the simultaneous presence of 2 tubular appendages, the type I and II tubules. Flattened xenomas were observed below the endothelium of gill lamella arteries. The irregular xenomas were located in the connective tissue of the gill filament and showed multiple projections occupied by spores. Both flattened and irregular xenomas showed no evidence of inflammatory reaction. An earlier proposed hypothesis is expanded to explain how L. salmonae is implanted beneath lamellar endothelium and within filament connective tissue.

Ultrastructural study of the early development and localization of Loma salmonae in the gills of experimentally infected rainbow trout.

The early ultrastructural stages of Loma salmonae were studied in the gills of experimentally infected rainbow trout. No parasitic stages were identified during the first 2 wk of the infection. By week 3 postexposure (PE), uninucleate and binucleate meronts were recognized within host cells (no xenomas) associated with the capillary channels of secondary lamellae and lamellar arteries. An inflammatory reaction was absent. In secondary lamellae, infected cells were isolated from the capillary lumen, and some were recognized as pillar cells. In lamellar arteries, infected cells were localized beneath the endothelium and not in the lumen. Inflammatory reaction and destruction of parasites inside blood cells in the lumen of secondary lamellae were observed by week 4 PE. Three hypotheses, i.e., isolation, internalization, and evasion, are proposed to explain the localization of the infected cells in the gills. It is concluded that meronts are the earliest parasitic stage observed by week 3 PE, pillar cells are secondarily infected by phagocytosis of infected cells in the blood, endothelial cells of gills are not infected, and inflammatory response to the parasite starts by week 4 PE.