Isospora belli infection associated with acalculous cholecystitis in a patient with AIDS

Acalculous Cholecystitis in COVID-19 Patients: A Narrative Review

Acute acalculous cholecystitis (AAC) represents cholecystitis without gallstones, occurring in approximately 5-10% of all cases of acute cholecystitis in adults. Several risk factors have been recognized, while infectious diseases can be a cause of cholecystitis in otherwise healthy people. Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has spread worldwide, leading to an unprecedented pandemic. The virus enters cells through the binding of the spike protein to angiotensin-converting enzyme 2 (ACE2) receptors expressed in many human tissues, including the epithelial cells of the gastrointestinal (GI) tract, and this explains the symptoms emanating from the digestive system. Acute cholecystitis has been reported in patients with COVID-19. The purpose of this review is to provide a detailed analysis of the current literature on the pathogenesis, diagnosis, management, and outcomes of AAC in patients with COVID-19.

Intestinal Parasitic Infections in 2023

Intestinal parasites include intestinal protozoa and intestinal helminths. Intestinal parasitic infections (IPIs) pose a global health problem affecting over one billion people worldwide. Although these infections are predominantly seen in the developing world, they are frequently seen in the developed countries, particularly in immunocompromised patients. Patients' clinical presentations generally include diarrhea, dysentery, abdominal pain, nausea, vomiting, nutritional deficiency, iron deficiency anemia, anal and perianal itching, and rarely intestinal obstruction. The intestinal parasites have similarities in their mode of transmission and life cycle. The stool test is the primary way of diagnosing IPIs. Treatment is given with various anti-parasitic agents. However, appropriate preventive measures are essential for successfully controlling the IPIs.

Cystoisospora belli, liver disease and hypothesis on the life cycle

Cystoisospora belli causes chronic diarrhoea, acalculous cholecystitis, cholangiopathy and disseminated cystoisosporosis in patients with AIDS. Clinical manifestations and histological stages during C. belli infection in a patient with AIDS and liver disease were described. It was possible to identify sporozoite-like structures in the villus epithelium of the duodenum, close to the vascularization that underlies the basal membrane and unizoite tissue cysts near to the vascularization in the lamina propria. Unizoite tissue cysts were found inside of sinusoids in the liver communicating with the central vein and with a bile canaliculus and portal spaces. Based on these findings a hypothesis on C. belli life cycle could consider that the route of migration of unizoite tissue cysts up the liver is via the portal blood. The unizoite tissue cysts located in hepatic portal vein could migrated via sinusoid to central vein and general circulation through the venous system. The unizoite tissue cysts could also return via bile canaliculus to bile duct to portal triad. This hypothesis allows to understand the presence of unizoite stages in blood, the pathway by which the bile ducts become infected and unizoites in the liver being able to behave like hypnozoites that favour relapses and treatment failures.

Acute acalculous cholecystitis due to infectious causes

Acute acalculous cholecystitis (AAC) is an inflammation of the gallbladder not associated with the presence of gallstones. It usually occurs in critically ill patients but it has also been implicated as a cause of cholecystitis in previously healthy individuals. In this subgroup of patients, infectious causes comprise the primary etiology. We, herein, discuss the pathophysiological mechanisms involved in AAC, focusing on the infectious causes. AAC associated with critical medical conditions is caused by bile stasis and gallbladder ischemia. Several mechanisms are reported to be involved in AAC in patients without underlying critical illness including direct invasion of the gallbladder epithelial cells, gallbladder vasculitis, obstruction of the biliary tree, and sequestration. We emphasize that multiple pathogenic mechanisms may concurrently contribute to the development of AAC in varying degrees. Awareness of the implicated pathogens is essential since it will allow a more focused examination of the histopathological specimens. In conclusion, additional research and a high degree of clinical suspicion are needed to clarify the complex spectrum of mechanisms that are involved in the pathogenesis of AAC.

Pitfalls in Morphologic Diagnosis of Pathogens: Lessons Learned From the Pseudo-Cystoisospora Epidemic

Multiple groups have recently reported involvement of the gallbladder mucosa of immunocompetent patients by cystoisospora organisms. However, this has recently been disproved with the support of molecular and ultrastructural studies. Here we present a summary of these events, recounting how this pseudo-Cystoisospora epidemic began and ended. This review also highlights the important role played by ancillary techniques in supplementing the morphologic diagnosis of pathogens.

Ultrastructural Characteristics of Gallbladder Epithelial Inclusions Mimicking Cystoisospora

OBJECTIVES

There is recently reported increased prevalence of Isospora organisms in cholecystectomy specimens from immunocompetent patients, especially in acalculous cholecystectomies. We performed an ultrastructural and molecular evaluation of these specimens.

METHODS

From 28 gallbladders with intraepithelial inclusions, two specimens with diffuse involvement of the gallbladder epithelium were analyzed by electron microscopy. Polymerase chain reaction was performed on five samples for the ITS2 region of C belli and eukaryotic 18S region. The 18S products were sequenced by next-generation sequencing.

RESULTS

Electron microscopic analysis showed cytoplasmic condensations leading to vacuole formation. In contrast with true C belli, there were no identifiable organelles or organization. None of these cases showed amplified products other than human on molecular analysis.

CONCLUSIONS

Electron microscopic analysis demonstrates that the inclusions are condensed cytoplasmic material and not true organisms.

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.

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.

Unexpectedly High Prevalence of Cystoisospora belli Infection in Acalculous Gallbladders of Immunocompetent Patients

Objectives

Indications for cholecystectomy have changed dramatically over the past three decades. Cystoisospora belli has been reported in cholecystectomy specimens of immunocompetent patients. The present study was designed to determine the prevalence and clinical association of C belli in the gallbladder.

Methods

The study included retrospective review of cholecystectomy specimens (n = 401) removed for various indications, and a prospective cohort of cholecystectomy specimens (n = 22) entirely submitted for histologic evaluation. Correlations of presence of C belli with age, sex, clinical indication, and abnormalities of preoperative laboratory values were assessed by Fisher exact test.

Results

C belli was identified in 39/401 (9.7%) of the retrospective cohort, and 6/22 (27.3%) of the entirely submitted specimens. The presence of C belli showed no correlation with age, sex, clinical indication, or laboratory abnormalities.

Conclusions

C belli resides in a latent state in the gallbladder and may be best considered a commensal organism.

Epithelial Inclusions in Gallbladder Specimens Mimic Parasite Infection: Histologic and Molecular Examination of Reported Cystoisospora belli Infection in Gallbladders of Immunocompetent Patients

Recent publications have described epithelial cytoplasmic vacuoles and inclusions incidentally noted within gallbladder epithelium and concluded that they represent coccidian parasite infection, in particular, Cystoisospora belli. We identified 8 gallbladder specimens from our institution in the past 3 years in which this diagnosis was suggested or in which similar epithelial alterations were prominent. Molecular analysis was performed on the 8 gallbladder specimens and on 3 positive control specimens: small bowel biopsies from acquired immunodeficiency syndrome patients with diarrhea. Polymerase chain reaction using primers designed to amplify an internal transcribed spacer (ITS2) in the C. belli ribosomal gene cluster was performed on the DNA samples. All 8 gallbladder specimens were negative for amplification, while a product consistent with C. belli was amplified from all 3 positive controls. Histologically, the gallbladder cytoplasmic inclusions stained diffusely positive for Grocott-Gomori's methenamine silver and Periodic acid-Schiff with diastase. In contrast, sections from a positive control small bowel biopsy demonstrated organisms that were negative for Grocott-Gomori's methenamine silver and showed a distinct capsular and punctate internal staining on Periodic acid-Schiff with diastase in various parasite forms. Together, the lack of molecular evidence of C. belli and the distinct morphologic and special staining patterns in these gallbladders compared with positive control small bowel suggest that these epithelial changes do not represent true C. belli infection. Our results suggest that gallbladders of immunocompetent patients may occasionally show epithelial changes that can morphologically mimic C. belli infection. Pathologists should be aware of this histologic variant to minimize unnecessary treatment, testing, and patient anxiety.

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.

Acalculous Cholecystitis Due to Histoplasma capsulatum in a Patient With HIV Infection

Although acalculous cholecystitis typically occurs in critically ill individuals, it has been described in patients with HIV infection. Recognition of AIDS-related acalculous cholecystitis is important for gastroenterologists to provide optimal therapy, since many different opportunistic pathogens may be involved. Histoplasma capsulatum causes a wide spectrum of infectious sequelae, including disseminated histoplasmosis in patients with HIV infection, but biliary tract involvement has been described infrequently. We present a case of acalculous cholecystitis caused by H. capsulatum in a patient with HIV infection.

First detection of acalculous cholecystitis associated with Sarcocystis infection in a patient with AIDS

Acalculous cholecystitis and cholangitis are increasingly being recognized as complications of AIDS. The opportunistic parasites that have been most commonly associated with these disorders are Cryptosporidium species, Isospora belli, Cyclospora cayetanensis and Enterocytozoon bieneusi. The authors performed a parasitological survey on the gallbladder tissue sections of patients underwent cholecystectomy due to chronic acalculous cholecystitis at the Shiraz University of Medical Sciences, Iran. Light microscopic investigation in more than three hundred archived histopathological slides revealed the presence of sexual stages (i.e., mature sporocysts) of a coccidial protozoan in a patient with AIDS who developed acalculous cholecystitis as confirmed by histological, parasitological and molecular tests in which Sarcocystis species was the only identifiable pathogen in gallbladder sections. In the best of our knowledge it's the first documented case of chronic non-calculous cholecystitis due to Sarcocystis parasite in an Iranian AIDS patient from worldwide.

Isospora belli associated recurrent diarrhea in a child with AIDS

Persistent diarrhea is a major manifestation of Acquired Immunodeficiency Syndrome (AIDS) which might be more complicated in Human Immunodeficiency Virus (HIV) infected children especially those from developing countries. There are numerous reports showing the emergence of intestinal opportunistic coccidian parasites, mostly Cryptosporidium parvum and Isospora belli in HIV-infected individuals. The prevalence of isosporiasis is probably underestimated in developing countries because routinely not all HIV-infected patients are examined for the presence of this protozoan infection. Here we report a case of HIV-infected isosporiasis presenting with failure to thrive and persistent diarrhea. Since I. belli infection in children responds well to therapy with trimethoprim-sulfamethoxazole, isosporiasis should be considered as a treatable infection in AIDS, if it is detected at proper time.

Molecular characterization of Cystoisospora belli and unizoite tissue cyst in patients with Acquired Immunodeficiency Syndrome

Cystoisospora belli is a coccidian protozoan that can cause chronic diarrhoea, acalculous cholecystitis and cholangiopathy in AIDS patients. We applied molecular methods to identify Cystoisospora at species level in AIDS patients presenting with and without the presence of unizoites in lamina propria. Coprological and histological analyses were performed in stool and/or biopsy samples from 8 Cystoisospora-infected patients. DNA from the same samples was used to amplify 2 fragments of the SSU-rRNA gene and the ITS-1 region. Sequencing of the resulting amplicons identified C. belli infections in all cases, independent of the presence or absence of unizoite tissue cysts. Further work should be considered in order to find molecular targets related to strain variations in C. belli.

Does HIV-related cholangiopathy exist in the setting of liver transplantation?

Biliary tract complications after liver transplantation represent a source of morbidity and mortality. Performing an analysis to evaluate whether HIV infection and its related comorbidities, such as HIV-related cholangiopathy, could be an unknown risk factor for biliary stricture, we found that HIV-positivity could lead to greater susceptibility to biliary damage. The pathogenesis of the damage seems to involve the pretransplant immunological status and the number and type of posttransplant infections, although further studies are needed.

Refractory isosporiasis

The authors describe a case of severe debilitating diarrhea due to isosporiasis in a two year old child, a known case of systemic vasculitis receiving prolonged corticosteroids therapy, an association rarely reported previously. It was refractory to treatment with dihydrofolate reductase inhibitor combined with sulfonamide such as cotrimoxazole to which isosporiasis usually responds well and is being described here for clinical interest and uniqueness of its presentation and laboratory findings.

Cholestasis in HIV-infected patients

Cholestasis is frequently observed in the HIV-infected population and can be caused by drugs, such as highly active antiretroviral therapy (HAART) and antimicrobial agents, and by opportunistic infections of the liver. Less common causes such as HIV-related malignancies or biliary tract disease are also encountered. Most disorders respond to medical management, but patient outcome was often dictated by the stage of the HIV infection and concomitant illnesses in the pre-HAART era. Prompt recognition and specific treatment may improve the outcome for these patients in the HAART era.

[Extraintestinal finding of Isospora belli unizoic cysts in a patient with AIDS: case report]

This report describes the presence of Isospora belli unizoic cysts in mesenteric lymph nodes and of gametocytes in the gallbladder epitelium of a 26 year-old Brazilian male patient with Acquired Immune Deficiency Syndrome. This patient had received treatment for several times with sulfamethoxazole-trimethoprim. It is discussed the significance of I. belli tissue cysts as possible foci of resistance of the parasite and their association with the infection relapse even post-treatment with anticoccidian medication.

Gastrointestinal infections in the immunocompromised host

Gastrointestinal disease is a significant cause of morbidity and mortality in the immunocompromised patient. This article focuses on the infectious gastrointestinal complications associated with the treatment of malignant disease and with solid organ transplantation but not HIV. Gastrointestinal defenses and the various mechanisms by which they are impaired are reviewed. The major pathogens and malignancies of this patient population and an approach to their diagnosis, treatment, and prevention are discussed.

Isosporosis and unizoite tissue cysts in patients with acquired immunodeficiency syndrome

Isospora belli, a coccidian parasite in humans, has been described as causing chronic diarrhea and acalculous cholecystitis in patients with the acquired immunodeficiency syndrome (AIDS). Diagnosis can be made at the tissue level in the epithelium of the small bowel and by fecal examination. Disseminated extraintestinal forms are uncommon. We studied 118 adult patients with AIDS and chronic diarrhea using stool analysis and endoscopy with duodenal biopsy specimen collection. These samples were processed by routine histology and transmission electron microscopy. Isosporosis was diagnosed in 8 cases. In 2 of them, unizoite tissue cysts were present in the lamina propria, with negative results in stool materials. The cysts were located within a large parasitophorous vacuole. There were no structural means of differentiating the species level of Isospora based on morphology using light or electron microscopy. We believe further work should be done to determine if unizoite tissue cysts are part of the cycle of I belli or of other species of Isospora that could be pathogenic in immunocompromised hosts.

Prevalence of intestinal parasitic infections in patients with acquired immunodeficiency syndrome in Brazil

OBJECTIVES

To evaluate the prevalence of intestinal parasitic infections and to investigate the possible associations of clinical status and laboratory findings with the different parasites found in stool samples.

METHODS

Each patient was provided with one standard fecal collection vial containing 10% formalin for detecting ova, larvae, and cysts. To detect Cryptosporidium parvum and Isospora belli, the acid-fast Kinyoun stain and fluorescent auramine-rhodamine stain were used.

RESULTS

A total of 200 patients with acquired immunodeficiency syndrome participated in this study; 40% were infected with at least one pathogenic species. The total prevalence of parasites was 16% for Giardia lamblia, 13% for Entamoeba coli, 7% for Cryptosporidium parvum, 3.5% for Endolimax nana, 2.5% for Ascaris lumbricoides, 2.5% for Strongyloides stercoralis, 2% for Isospora belli, and 0.5% for Blastocystis hominis. Results showed that diarrhea was significantly associated with cryptosporidiosis, giardiasis, and isosporiasis. However, no association was observed between the CD4+ cell counts and the manifestation of any particular parasite.

CONCLUSIONS

The data support the value of standard fecal examinations in human immunodeficiency virus-infected patients, even in the absence of diarrhea, since these examinations easily can be performed, with low costs, and frequently disclose treatable conditions.

Enteric parasites and AIDS

OBJECTIVE

To report on the importance of intestinal parasites in patients with AIDS, showing relevant data in the medical literature, with special emphasis on epidemiology, diagnosis and treatment of enteroparasitosis, especially cryptosporidiosis, isosporiasis, microsporidiasis and strongyloidiasis.

DESIGN

Narrative review.

Cholangiopathy in HIV-infected patients

HIV cholangiopathy is a disease of advanced-stage AIDS that presents with biliary symptoms and anicteric cholestasis. An abnormal ultrasound examination in a patient with low CD4 count is evaluated by endoscopic retrograde cholangiopancreatography, which demonstrates the characteristic cholangiographic abnormalities. Besides being the gold standard for diagnosis, it offers therapeutic intervention and possible pain relief in the presence of papillary stenosis. An infectious pathogen is identifiable in a majority of patients, suggesting infection-related damage to the biliary tree. Anti-infective therapy, however, usually is ineffective, and prognosis is related to the underlying stage of AIDS.

Surgical therapy for 101 patients with acquired immunodeficiency syndrome and symptomatic cholecystitis

BACKGROUND

Hepatobiliary disease in patients with acquired immunodeficiency syndrome (AIDS) has been well documented. Cytomegalovirus and Cryptosporidium are the pathogens most frequently associated. Previous reports of cholecystectomies and AIDS have had conflicting results on morbidity and mortality.

METHOD

Retrospective review of 101 patients with AIDS and symptomatic cholecystitis who underwent cholecystectomy from December 1989 to May 1995.

RESULTS

All patients had symptoms characteristic of gallbladder disease, the most common being abdominal pain and fever. Thickening of the gallbladder was the most common diagnostic finding. Fifty-six patients underwent open cholecystectomy and 45 laparoscopic cholecystectomy. Pathologic examination revealed an abnormal gallbladder in all cases and gallstones in 29%. A specific pathogen or malignancy was identified as the etiologic agent in 44% of patients. Perioperative morbidity was similar (<5%) in both surgical groups. Perioperative mortality was 4% among all the patients treated.

CONCLUSIONS

Both open and laparoscopic cholecystectomy improved the quality of life of these patients and should be considered as the treatment for persistent hepatobiliary symptoms in patients with AIDS.

Gallbladder and biliary tract disease in AIDS

Biliary disease occurs in a subset of AIDS patients with CD4 counts of less than 100 per mm3. These patients present with right upper quadrant and epigastric pain, cholestasis, and usually abnormal findings on imaging. In 75% of patients, an associated opportunistic infection can be identified. In patients with biliary disease, pain is often relieved following endoscopic sphincterotomy, whereas cholecystectomy provides pain relief in patients with acalculous cholecystitis.

Parasites and Diarrhea. I: Protozoans and Diarrhea

Intestinal parasitism is extremely common, with approximately 70% of all people harboring one or more intestinal parasite. Parasitism and diarrhea are both hyperendemic in areas where sanitation is suboptimal. Many clinicians assume that the identification of intestinal parasites in patients with diarrhea implies that the parasites are the cause. This approach is frequently misguided. Some intestinal parasites such as Giardia lamblia and Entamoeba histolytica certainly do cause diarrhea. Others, for example Entamoeba coli and Ascaris lumbricoides, almost certainly do not. In addition, there are a number of other organisms that have been associated with diarrheal illness in some cases, which may or may not be important pathogens. In this article, we will review the role of protozoans as definite and possible causes of diarrhea. In Part II, we review the role of helminths in diarrhea.

Agents of diarrhea

Diarrhea is a common problem for AIDS patients, and is chronic and debilitating. A thorough evaluation will reveal a pathogen in the majority of patients, and the organisms most frequently identified in AIDS patients with chronic diarrhea are Cryptosporidium, microsporidia, and Mycobacterium avium complex. Bacterial pathogens are more common in AIDS patients than in the general population and may present in different ways from infections in immunocompetent hosts. Other pathogens, including Cryptosporidium and microsporidia, are difficult to diagnose and have no effective therapy. Moreover, enteric viruses and HIV itself may contribute to the diarrhea. In addition to microbes, other factors such as medication, immune dysregulation, automatic dysfunction, and nutritional supplementation play a substantial role in diarrhea of AIDS patients.

Waterborne protozoan pathogens

Protozoan parasites were the most frequently identified etiologic agents in waterborne disease outbreak from 1991 to 1994. The waterborne parasites Giardia lamblia, Naegleria fowleri, Acanthamoeba spp., Entamoeba histolytica, Cryptosporidium parvum, Cyclospora cayetanesis, Isospora belli, and the microsporidia are reviewed. For each parasite, the review includes history, life cycle, incidence, symptoms, and therapy. Clinical detection methods are compared, and emerging technologies are discussed. Information on the association of these parasites with waterborne outbreaks is reviewed. Current information on protozoan parasites identified as etiological agents in waterborne outbreaks is discussed. Water industry issues related to recent disease outbreaks are examined in the context of water quality testing regulations for G. lamblia and those proposed for C. parvum. The review identifies the limitations of the American Society of Testing and Materials water-testing method for these parasites. An overview of federal regulations affecting the water industry and laboratories that test for water quality is also provided. The article highlights the importance of the clinical laboratory as a frontline defense for the detection of infectious organisms. The review points to the need for clinical laboratories, physicians, and public health personnel to cooperatively plan and assess the challenge of meeting this potential public health threat.

Biology of Isospora spp. from humans, nonhuman primates, and domestic animals

Coccidial parasites of the genus Isospora cause intestinal disease in several mammalian host species. These protozoal parasites have asexual and sexual stages within intestinal cells of their hosts and produce an environmentally resistant cyst stage, the oocyst. Infections are acquired by the ingestion of infective (sporulated) oocysts in contaminated food or water. Some species of mammalian Isospora have evolved the ability to use paratenic (transport) hosts. In these cases, infections can be acquired by ingestion of an infected paratenic host. Human intestinal isosporiasis is caused by Isospora belli. Symptoms of I. belli infection in immunocompetent patients include diarrhea, steatorrhea, headache, fever, malaise, abdominal pain, vomiting, dehydration, and weight loss, blood is not usually present in the feces. The disease is often chronic, with parasites present in the feces or biopsy specimens for several months to years. Recurrences are common, Symptoms are more severe in AIDS patients, with the diarrhea being more watery. Extraintestinal stages of I. belli have been observed in AIDS patients but not immunocompetent patients. Treatment of I. belli infection with trimethoprim-sulfamethoxazole usually results in a rapid clinical response. Maintenance treatment with trimethoprim-sulfamethoxazole is needed because relapses often occur once treatment is stopped.

Biliary cryptosporidiosis in HIV-infected people after the waterborne outbreak of cryptosporidiosis in Milwaukee

BACKGROUND

In March 1993, the municipal water supply in Milwaukee became contaminated with cryptosporidium and a widespread outbreak of cryptosporidiosis occurred.

METHODS

We retrospectively studied the relations among the clinical presentation, CD4 count, and survival in a group of 82 patients infected with the human immunodeficiency virus (HIV) in whom cryptosporidiosis developed during the outbreak. Infection was documented by the finding of cryptosporidium in stool.

RESULTS

There was a sharp increase in the number of HIV-infected patients with cryptosporidiosis after the period of water contamination. Four of 24 patients with biliary symptoms (17 percent) and 30 of 58 without biliary symptoms (52 percent) were alive one year after the outbreak (P = 0.003). Twenty-one of the patients with biliary symptoms had CD4 counts < or = 50 per cubic millimeter, as compared with 36 of 57 patients without biliary symptoms (88 percent vs. 63 percent, P = 0.03). The CD4 count was not available for one patient in the latter group. Within one year, 41 of the patients with CD4 counts < or = 50 per cubic millimeter had died, as compared with 6 of those with higher counts (72 percent vs. 25 percent, P < 0.001). After adjustment for the CD4 count, independent predictors of death were older age and the presence of nausea and vomiting.

CONCLUSIONS

When HIV-infected patients are exposed to cryptosporidium, those with CD4 counts < or = 50 per cubic millimeter are at increased risk for biliary symptoms and for death within one year after the infection.