Indian Journal of Pathology and Microbiology

: 2014  |  Volume : 57  |  Issue : 2  |  Page : 272--274

Isosporiasis in a tertiary care center of North India

Neha Gautam1, Sumeeta Khurana1, Aman Sharma2, Rakesh Sehgal1,  
1 Department of Parasitology, Post Graduate Institute of Medical Education and Research, Chandigarh, Punjab and Haryana, India
2 Department of Internal Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh, Punjab and Haryana, India

Correspondence Address:
Sumeeta Khurana
Department of Medical Parasitology, Post Graduate Institute of Medical Education and Research, Chandigarh, Punjab and Haryana


Background: Cystoisospora (Isospora) belli is a coccidian, protozoan parasite that resides in the gastrointestinal tract of humans. It is mainly reported from HIV-positive individuals. However, a few cases have been reported in other immunosuppressed individuals including renal transplant patients, and those with lymphoma and leukemia. Materials and Methods: During a period of 5 years (2008-2012), approximately 1700 stool samples of immunosuppressed patients were screened for the presence of opportunistic parasitic infections by a modified acid fast staining technique. Results: A total of 41 C. belli were reported, out of which 30 were HIV-positive individuals while 11 were HIV negative. The latter individuals were also immunosuppressed due to prolonged use of steroids or other immunosuppressive drugs. Twenty-six out of 30 HIV-positive patients and all the HIV-negative individuals with C. belli infection had diarrhea. Conclusion: All immunosuppressed individuals should be examined for the presence of opportunistic coccidian parasitic infections and treated accordingly and alternatively, isolation of opportunistic parasites should trigger a hunt for immunocompromised state to reduce the morbidity and mortality in such patients.

How to cite this article:
Gautam N, Khurana S, Sharma A, Sehgal R. Isosporiasis in a tertiary care center of North India.Indian J Pathol Microbiol 2014;57:272-274

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Gautam N, Khurana S, Sharma A, Sehgal R. Isosporiasis in a tertiary care center of North India. Indian J Pathol Microbiol [serial online] 2014 [cited 2022 Sep 28 ];57:272-274
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Cystoisospora belli (previously called Isospora belli) is a coccidian, unicellular protozoan parasite that resides in the gastrointestinal tract. It usually causes non-bloody diarrhea in tropical and subtropical countries. The disease course is mild and usually transient in immunocompetent hosts whereas the disease varies from a chronic intermittent illness to life-threatening diarrheal illness in immunocompromised individuals. Though the disease is commonly reported in HIV-positive patients, there are limited number of case reports from patients immunocompromised due to factors other than HIV infection such as lymphoproliferative disorders including adult T-cell leukemia, acute lymphoblastic leukemia, Hodgkin's lymphoma and thymoma [1],[2],[3],[4] and post transplant patients. [5],[6],[7]


Stool samples from the immunosuppressed patients and children received in the Department of Medical Parasitology from year 2008 to 2012 for investigation of parasitic etiology were included in our study. All samples were subjected to formalin-ether concentration (centrifugation at 500 × g for 10 min) and examined by microscopy of wet mount, iodine mount, cold-strong Ziehl-Nielsen-stained smears for coccidian parasites and modified trichrome-stained smears for microsporidia. [8] The records of patients found to be excreting Cystoisospora cysts in their stool were analyzed for their demographic details, HIV status, history of diarrhea, any opportunistic infections and other comorbid conditions.


Patient characteristics

Approximately 1700 stool samples were received in the Department of Parasitology from the above mentioned group of patients during the study period out of which 940 were HIV positive as per National AIDS control organization (NACO) testing guidelines.

Prevalence of gastrointestinal parasites

Microsporidia were the most common parasites detected in both HIV and non-HIV patients with Giardia duodenalis being the next most common, followed by Cryptosporidium spp and Cystoisospora. Significantly higher number of HIV positive patients were infected with Giardia, Microsporidia and Cystoisospora. [Table 1] shows the frequency of intestinal pathogens in relation to the HIV status of the study group.{Table 1}

Prevalence of Cystoisospora belli

A total of 41 (2.4%) patients were found to excrete C. belli cysts in their stool. The age of the patients infected with C. belli ranged from 3.5 to 48 years (mean 33.6 years) of which three patients were children aged, 3.5, 5 and 12 years. There was male preponderance in this group, the male to female ratio being 6.6:1.The occurrence of isosporiasis was highest (63.41%) during the months of May to August during all these years.

Out of these 41 patients, 30 were HIV positive and 11 were HIV negative. The mean age of the HIV-positive patients was 32.73 years, while that of the HIV-negative group was 31.5 years. The male to female sex ratio in the HIV-positive group was 14:1 in comparison to HIV-seronegative patients in whom it was 2.3:1.

Thirty-seven patients had a history of diarrhea. Twenty-six out of 30 HIV-positive patients and all the HIV-negative individuals with C. belli infection had diarrhea. Chronic diarrhea was most common in the HIV positives [Table 2] while most (63.6%) of the HIV-seronegative subjects had persistent diarrhea.

Twenty-two (73.3%) HIV-positive patients were on anti-retroviral therapy (zidovudine/lamivudine, stavudine and nevirapine) at the time of presentation. Seven of these patients also had other opportunistic infections like oropharyngeal candidiasis, Pneumocystis jirovecii pneumonia, herpes zoster, pulmonary tuberculosis and genital ulcers. The HIV-negative patients with Cystoisospora infection were immunosuppressed either due to medications (steroids or immunosuppressants) for chronic diseases like inflammatory bowel disease, interstitial lung disease, polymyositis, or post transplant or were children with nephrotic syndrome and malnutrition. The clinical details of 8 of these 11 patients are given in [Table 3].{Table 2}{Table 3}

Out of these 11 HIV-seronegative patients, 3 (27.3%) were females and 8 (72.7%) were males. The median age of the patients was 30.2 years. All these patients had history of diarrhea with most patients having persistent or chronic diarrhea. All these patients had Cystoisospora as the sole pathogen detected, and bacterial cultures and other parasitic agents were negative. The patients were treated with trimethoprim 160 mg and sulfamethoxazole 800 mg (one double strength tablet) four times a day for 2 weeks with which the diarrhea improved and follow-up samples were negative.


C. belli is an opportunistic pathogen that mainly causes diarrhea in HIV/AIDS patients. In India, the prevalence of C. belli infection ranges from 2.5% to 14% in HIV-positive patients. [9],[10],[11],[12] Though the data regarding the prevalence of isosporiasis is abundant in HIV-positive patients there is scarcity of information about the prevalence of the disease in HIV-negative patients. There are case reports available in the literature demonstrating the observation of intestinal isosporiasis in patients with liver and intestinal transplant, [5],[7] patients with lymphoproliferative disorders [1],[2],[3],[4] and sickle-cell anemia. [13] However from India, there are limited number of reports in non-HIV patients namely in a renal transplant patient, a patient with Evan's syndrome and a malnourished child. [6],[14],[15] In our study, most of the patients were HIV positive and those negative were either on long-term steroids or other immunosuppressive drugs like tacrolimus and mycophenolate mofetil, thereby predisposing them to isosporiasis. The prevalence of isosporiasis may be much more in non-HIV patients. Since isosporiasis is not routinely looked for in these group of patients therefore the clinicians must be attentive towards Cystoisospora as a cause for diarrhea in immunosuppressed patients in our setting where the pathogen is endemic.

C. belli responds well to treatment with trimethoprim-sulfamethoxazole (TMP-SMX). Alternative treatment regimens include pyrimethamine-sulfadoxine or nitazoxanide. Diarrhea frequently recurs in AIDS patients hence secondary prophylaxis is recommended. Various studies in HIV-positive patients have explained the need and effectiveness of secondary prophylaxis with TMP-SMX. [12],[16] However, no such recommendation is available for other immunocompromised or immunosuppressed conditions. Therefore, repeated stool examination should be carried out in immunosuppressed patients to pick up any opportunistic infections and thereafter to ensure eradication. In fact, the presence of a parasitic agent like Cystoisospora should trigger the search for some underlying immunosuppressive condition. And vice versa, immunosuppressed individuals should get their stools routinely examined for opportunistic pathogens.


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