Recurrent isosporiasis over a decade in an immunocompetent host successfully treated with pyrimethamine

Cystoisospora belli infections in humans: the past 100 years

Cystoisospora belli is a coccidian parasite of humans, with a direct fecal-oral transmission cycle. It is globally distributed, but mainly found in tropical and subtropical areas. Many cases of C. belli infections have been reported in patients with HIV, and in patients undergoing immunosuppressive therapy for organ transplants or those treated for tumours worldwide. Unsporulated or partially sporulated oocysts of C. belli are excreted in feces. When sporulated oocysts in contaminated water or food are ingested, asexual and sexual stages of C. belli are confined to the epithelium of intestines, bile ducts and gallbladder. Monozoic tissue cysts are present in extra-intestinal organs (lamina propria of the small and large intestine, lymph nodes, spleen, and liver) of immunosuppressed humans. However, a paratenic host has not been demonstrated. Cystoisospora belli infections can be persistent, lasting for months, and relapses are common; the mechanism of relapse is unknown. Recently, the endogenous stages of C. belli were re-examined and attention was drawn to cases of misidentification of non-protozoal structures in the gallbladder of patients as C. belli. Here, we review all aspects of the biology of C. belli, including morphology, endogenous stages, prevalence, epidemiology, symptoms, diagnosis and control.

A road less travelled: Clinical comparison of HIV seropositive and seronegative patients with cystoisosporiasis - An 11-year experience from a tertiary care centre in Northern India

Background

Cystoisospora is a well-known opportunistic enteric parasite among human immunodeficiency virus (HIV) seropositive patients but there is a paucity of data among HIV negative patients. This study investigated Cystosporiasis on both HIV positive and negative patients, with or without diarrhea, presenting to a tertiary care and super specialty center of northern India.

Methodology

Oocysts of Cystoisospora were detected on light microscopy, by modified Kinyoun staining of stool specimens, over an 11-year study period.

Results

Of the 10,233 stool specimens evaluated, Cystoisospora was detected in 64 patients, 37 (57.81%) of whom were HIV positive. Year-wise analysis showed an overall declining trend of cystoisosporiasis. Maximum cases were detected in May and June in HIV positive patients and February and September among HIV negative patients. Among HIV positive patients, the mean CD4 count was 152.04 ± 81.12cells/μL, mean absolute eosinophil count (AEC) was 229.16 ± 175.62 cells/μL and 12.5% patients had mild eosinophilia. Tuberculosis was the most common co-morbidity. Dual infections of Cystoisospora with Cryptosporidium and Giardia were also seen. Among HIV negative patients, eight had primary autoimmune disorders, seven were solid organ transplant recipients and the rest had chronic bowel diseases. The mean AEC was 485.47 ± 414.88 cells/μL, with 14.81% patients showing mild and 11.11% showing marked eosinophilia. Dual infection with Giardia was seen. Recurrent cystoisosporiasis was noted, despite cotrimoxazole treatment in a single case.

Conclusion

The epidemiology of cystoisosporiasis differs between HIV seropositive and seronegative patients in terms of year-wise and month-wise trends, co-infections and most importantly, AECs.

Endogenous development of Cystoisospora belli in intestinal and biliary epithelium of humans

Cystoisospora(Isospora)belliis a coccidian parasite of humans. It can cause serious digestive disorders involving infection of intestines, biliary tract and gallbladder, especially in those with depressed immunity. It has a direct fecal–oral transmission cycle. After ingestion of sporulated oocysts, the parasite multiplies asexually and sexually within host epithelial cells, resulting in unsporulated oocysts that are excreted in feces. The details of asexual and sexual stages are not known and certain inclusions in epithelial cells in biopsy samples have been erroneously identified recently asC. belli. Here, we provide details of developmental stages ofC. belliin two patients, in duodenal biopsy of one and biliary epithelium of the other. Immature and mature asexual stages (schizonts/meronts) were seen in epithelial cells. The merozoites were seen singly, in pairs and in groups in single parasitophorous vacuole (pv) in host cytoplasm. Immature and mature meronts were seen together in the same pv; up to eight nuclei were seen in meronts that retained elongated crescent shape; round multinucleated schizonts, seen in other coccidians, were not found. Meronts were up to 25µm long and contained up to ten merozoites that were 8–11µm long. The merozoites and meronts contained PAS-positive granules. Microgamonts (male) contained up to 30 nuclei that were arranged at the periphery and had condensed chromatin; 1–3 PAS-positive, eosinophilic, residual bodies were left when microgametes were formed. The microgametes were 4µm long and PAS-negative. All stages of macrogamonts, including oocysts were PAS-positive. The detailed description of the life cycle stages ofC. bellireported here should facilitate in histopathologic diagnosis of this parasite.

Cystoisospora belli Gallbladder Infection in a Liver Transplant Donor

Introduction

Cystoisospora belli (previously Isospora belli) is a parasitic protozoan of the human gastrointestinal system. It rarely causes symptoms in immunocompetent hosts but can cause severe diarrhea in immunocompromised patients, with a rate of recurrence and risk of dissemination. Gallbladder infections are however rare. The treatment of choice for symptomatic patients is a 7–10-day course of trimethoprim-sulfamethoxazole.

Case

In this case, we report on an incidental finding of Cystoisospora belli organisms in the donor gallbladder following a transplant cholecystectomy. There was no report of symptoms in the donor. The recipient was treated with a course of trimethoprim-sulfamethoxazole, without evidence of cystoisosporiasis. Given the risk of recurrence in immunocompromised hosts, the patient will continue to be monitored for reactivation in the future.

Conclusion

Despite advances in transplant protocols and screening, disease transmission from the donor to recipient still occurs in about 0.2% of all organ transplants. With the increased use of organs from drug overdose victims and other high-risk donors, practitioners (including pathologists, hepatologists, and surgeons) must maintain a high index of suspicion for such potentially harmful organisms.

Chronic Cystoisospora belli infection in an immunocompetent Myanmar refugee - microscopy is not sensitive enough

BACKGROUND

Cystoisosporiasis is an opportunistic infection seen more commonly in patients with acquired immunodeficiency syndrome. Although uncommon, Cystoisospora infection can occur in immunocompetent individuals but tend to be benign and self-limiting. Chronic infection however, has been described but diagnosis can often be challenging and requires a high clinical index of suspicion.

CASE PRESENTATION

We present a case of delayed diagnosis of Cystoisospora belli (C. belli) in an immunocompetent 28-year-old refugee from Myanmar. She had a history of chronic diarrhea where exhaustive investigations over many years failed to reveal a diagnosis. Cystoisospora belli cysts were finally detected in stool 4 years after investigation commenced, and PCR testing on stored colon biopsies amplified a molecular product with 99 % sequence homology to C. belli. The patient improved promptly with trimethoprim-sulfamethoxazole treatment.

CONCLUSION

In the appropriate clinical context we suggest molecular testing for C. belli or an empirical therapeutic trial.

Failure to eradicate Isospora belli diarrhoea despite immune reconstitution in adults with HIV--a case series

Isospora belli causes diarrhoea in patients with AIDS. Most respond to targeted therapy and recommendations are that secondary prophylaxis can be stopped following immune reconstitution with ART. We report eight cases of chronic isosporiasis that persisted despite standard antimicrobial therapy, secondary prophylaxis, and good immunological and virological response to ART. Median CD4 nadir was 175.5 cells/mm(3) and median highest CD4 while symptomatic was 373 cells/mm(3). Overall 34% of stool samples and 63% of duodenal biopsy specimens were positive for oocytes. Four patients died, two remain symptomatic and two recovered. Possible explanations for persistence of symptoms include host factors such as antigen specific immune deficiency or generalised reduction in gut immunity. Parasite factors may include accumulating resistance to co-trimoxazole. Research is required to determine the optimum dose and duration of co-trimoxazole therapy and whether dual therapy may be necessary. Mortality was high and pending more data we recommend extended treatment with high-dose co-trimoxazole in similar cases.

Isospora belli superinfection in a patient with eosinophilic gastroenteritis--a diagnostic challenge

Isospora belli infection, characterized by peripheral blood eosinophilia, is often seen as an opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS). It is also reported in patients with underlying lymphoproliferative disorders including lymphoma and leukemia. Eosinophil-associated gastrointestinal disorders (EGID), including eosinophilic gastroenteritis (EGE), is characterized by eosinophilic infiltration of the gastrointestinal (GI) tract with various GI symptoms. We report a case of a 50-year-old male who developed Isospora superinfection of the small bowel while receiving systemic corticosteroids for EGE. He presented with worsening diarrhea, abdominal pain, nausea and vomiting with worsening peripheral eosinophilia. I. belli infection was diagnosed by the detection of oocysts in stool samples and by the presence of the parasite on duodenal biopsy in the background of tissue eosinophilia. I. belli can cause severe chronic diarrhea in immunocompromised patients on corticosteroids. Trimethoprim-sulfamethoxazole often provided rapid cure. Even though peripheral blood eosinophilia was seen in both EGE and Isospora infection, the identification of subnuclear protozoal inclusions as a new histologic finding, as well as the absence of this finding in previous duodenal biopsies coupled with the continued presence of tissue eosinophilia, favored a parasitic superinfection in the setting of underlying EGE.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Isospora cholangiopathy: case study with histologic characterization and molecular confirmation

Isospora belli is an intracellular protozoan parasite that causes diarrhea worldwide and is endemic in the tropics. In the United States, it is an uncommon cause of traveler's diarrhea and a relatively rare opportunistic pathogen among the immunocompromised, particularly AIDS patients. Isospora infects the small intestine, where both sexual and asexual replication occur, and oocysts are shed in the stool. Isosporiasis of the gallbladder has also been described in AIDS patients. We report a case of diffuse biliary isosporiasis in a West African man who presented with acute illness and was found to have dilated bile ducts. He had no history of hepatobiliary disease; his HIV status was unknown. Endoscopic retrograde cholangiopancreatography demonstrated markedly abnormal intrahepatic and extrahepatic bile ducts, with radiologic findings reminiscent of primary sclerosing cholangitis. However, common bile duct biopsies revealed Isospora belli, which was confirmed by both electron microscopy and polymerase chain reaction-based molecular analysis.

Food- and waterborne pathogens: you are (infected by) what you eat!

Coccidia are protozoan parasites responsible for disease worldwide. The orally transmissible stages of coccidia make them food- and waterborne threats. The occurrence of multiple, human-infectious coccidia with diverse life cycles suggests that alterations in host range are a frequent occurrence, and can underlie the rapid emergence of pathogens.