Coccidian infections in AIDS. Toxoplasmosis, cryptosporidiosis, and isosporiasis

SEROPREVALENCE OF TOXOPLASMA GONDII INFECTION IN PIGS FROM SOUTHWESTERN MISSISSIPPI

Toxoplasma gondii infection of swine is a potential public health concern because it can be acquired by humans through the handling and consumption of contaminated raw meat. Infections in immunocompromised individuals and fetuses are the most severe and these individuals are most likely to develop clinical toxoplasmosis. Since Mississippians consume a lot of pork, there was a significant need to know the extent to which it poses a health problem in the State. This study focused on the southwestern region of Mississippi. Between July 2003 and March 2004, blood samples were collected from slaughterhouses in southwestern Mississippi and the Alcorn State University swine farm in Churchill, Mississippi. The collected blood samples were centrifuged and the sera were collected, labeled, and stored in a freezer at -20 C. The modified agglutination test was performed at dilutions of 1:25, 1:50, and 1:500. A titer of 25 was considered seropositive. Of a total of 302 samples tested, 48 (16%) were positive at a titer of 25; 29 (10%) were positive at 50; 11 (4%) were positive at 500. The seroprevalence of T. gondii in pigs in southwestern Mississippi is not as high as previous studies done in Mississippi. This could be attributed to the sample size. However, the potential for infection still exists.

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 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.

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.

SCL-Epred: a generalised de novo eukaryotic protein subcellular localisation predictor

Knowledge of the subcellular location of a protein provides valuable information about its function, possible interaction with other proteins and drug targetability, among other things. The experimental determination of a protein's location in the cell is expensive, time consuming and open to human error. Fast and accurate predictors of subcellular location have an important role to play if the abundance of sequence data which is now available is to be fully exploited. In the post-genomic era, genomes in many diverse organisms are available. Many of these organisms are important in human and veterinary disease and fall outside of the well-studied plant, animal and fungi groups. We have developed a general eukaryotic subcellular localisation predictor (SCL-Epred) which predicts the location of eukaryotic proteins into three classes which are important, in particular, for determining the drug targetability of a protein-secreted proteins, membrane proteins and proteins that are neither secreted nor membrane. The algorithm powering SCL-Epred is a N-to-1 neural network and is trained on very large non-redundant sets of protein sequences. SCL-Epred performs well on training data achieving a Q of 86 % and a generalised correlation of 0.75 when tested in tenfold cross-validation on a set of 15,202 redundancy reduced protein sequences. The three class accuracy of SCL-Epred and LocTree2, and in particular a consensus predictor comprising both methods, surpasses that of other widely used predictors when benchmarked using a large redundancy reduced independent test set of 562 proteins. SCL-Epred is publicly available at http://distillf.ucd.ie/distill/ .

ANTICORPOS IgG ANTI-TOXOPLASMA GONDII EM SUÍNOS ABATIDOS EM MATADOUROS DA REGIÃO METROPOLITANA DO RECIFE, PERNAMBUCO, BRASIL

RESUMO Objetivou-se avaliar a frequência da infecção por Toxoplasma gondii em suínos abatidos para o consumo humano em dois matadouros na Região Metropolitana do Recife, Pernambuco com inspeção Sanitária Estadual. A pesquisa de anticorpos foi realizada por meio da reação de Imunofluorescência indireta, adotando-se o ponto de corte 1:64. Foram analisados 327 animais provenientes de seis cidades, Abreu e Lima, Igarassu e Paulista, Carpina, Paudalho e Tracunhaém. Observou-se frequência de 9,78% de soros positivos, com diluições iguais ou superiores a 1: 64. Os resultados obtidos alertam sobre os riscos de infecção por T. gondii pela ingestão da carne suína crua ou mal cozida, pois é provável que os suínos soropositivos abriguem cistos teciduais, ressaltando a importância de um manejo de criação adequado, visando a diminuição do risco de infecção nesta espécie.

Criptosporidiose: uma revisão sobre a sua implicação na conservação dos mamíferos aquáticos

A criptosporidiose é uma doença parasitária emergente que vem sendo relatada em diversas espécies de mamíferos, incluindo os aquáticos. Esta revisão trata da epidemiologia da infecção por Cryptosporidium spp. em mamíferos aquáticos. A idade dos animais, dose infectante e o estado imunológico podem influenciar na apresentação clínica, e quando associados a outros patógenos pode levar o animal a óbito. A contaminação dos recursos hídricos constitui um dos principais meios de disseminação do parasito, que foi identificado por diferentes técnicas de análise. A adequação das estruturas de saneamento, utilização de métodos apropriados para a inativação dos oocistos e garantia das normas de higiene pessoal constituem algumas das maneiras recomendadas para minimizar a disseminação do Cryptosporidium entre os mamíferos aquáticos.

Optic nerve toxoplasmosis and orbital inflammation as initial presentation of AIDS

PURPOSE

To report a case of toxoplasmosis with optic nerve and orbital involvement as the initial presentation of HIV infection.

METHOD

Case report.

RESULTS

A 46-year-old zookeeper, who had had right central retinal vein occlusion (CRVO) 2 weeks previously, presented with painless lid and conjunctival swelling and profound visual loss in his right eye (RE). Examination revealed no light perception (NLP) RE with axial proptosis and ocular motility restriction; fundal examination revealed a clinical picture of an ischaemic CRVO. MRI of the brain and orbit showed ring-enhancing targetoid lesions in the brain and inflammatory changes in the right optic nerve, extraocular muscles and orbital fat. He was subsequently found to be HIV positive and had positive toxoplasma IgG serology.

CONCLUSIONS

Immunocompromised individuals have an increased likelihood for more severe and atypical presentations; this highlights the need for increased index of suspicion for HIV infection as ocular or orbital disease may be the first manifestation of life-threatening systemic toxoplasmosis.

Seroprevalence of Toxoplasma gondii in Swine From Slaughterhouses in Lima, Peru, and Georgia, U.S.A

Toxoplasma gondii is an important pathogen transmitted by food, with raw or undercooked meat as the main foodborne source of toxoplasmosis. In Peru, 2-4 million people have antibodies to T. gondii. It is believed that more than 60 million people in the United States are infected with T. gondii. In this study, the prevalence of T. gondii in pigs from Peru and the United States was determined by Western blot. The presence of IgG antibodies to T. gondii from serum samples was determined. Blood samples were collected from 137 pigs at a slaughterhouse in Lima, Peru, and 152 pigs at a slaughterhouse in Georgia. Of the serum samples collected from swine, 27.7% (n = 38) from Peru and 16.4% (n = 25) from the United States were positive for T. gondii. Swine represent a significant source of human infection with T. gondii in Peru and the United States.

Isospora belli infection and chronic electrolyte disturbance in a child with fetal alcohol syndrome

We report an 11-year-old boy with fetal alcohol syndrome and immunodeficiency, whose longstanding malnutrition, diarrhoea with steatorrhoea, symptomatic electrolyte loss and eosinophilia were attributed to renal tubular disease and recurrent worm infestation. The symptoms resolved with diagnosis and treatment of infection by the protozoan Isospora belli, although immunodeficiency persisted.

New insights into human cryptosporidiosis

Cryptosporidium parvum is an important cause of diarrhea worldwide. Cryptosporidium causes a potentially life-threatening disease in people with AIDS and contributes significantly to morbidity among children in developing countries. In immunocompetent adults, Cryptosporidium is often associated with waterborne outbreaks of acute diarrheal illness. Recent studies with human volunteers have indicated that Cryptosporidium is highly infectious. Diagnosis of infection with this parasite has relied on identification of acid-fast oocysts in stool; however, new immunoassays or PCR-based assays may increase the sensitivity of detection. Although the mechanism by which Cryptosporidium causes diarrhea is still poorly understood, the parasite and the immune response to it probably combine to impair absorption and enhance secretion within the intestinal tract. Important genetic studies suggest that humans can be infected by at least two genetically distinct types of Cryptosporidium, which may vary in virulence. This may, in part, explain the clinical variability seen in patients with cryptosporidiosis.

A clinicopathologic analysis of AIDS-related cryptosporidiosis

OBJECTIVE

To characterize the histology of AIDS-associated cryptosporidiosis and identify features that explain the clinical variability.

DESIGN

A retrospective analysis of HIV-positive individuals with cryptosporidiosis who underwent endoscopy at the Johns Hopkins Hospital between 1985 and 1996.

METHODS

The histologic features (intensity of Cryptosporidium infection, inflammation, mucosal damage, copathogens) of gastrointestinal biopsies from 37 HIV-positive individuals with cryptosporidiosis were systematically graded. These histologic features were correlated with the severity of the diarrheal illness obtained from a patient chart review.

RESULTS

Histologic features associated with Cryptosporidium infection include a neutrophilic infiltrate in the stomach, villus blunting in the duodenum, cryptitis and epithelial apoptosis in the colon, and reactive epithelial changes in the stomach and duodenum. The nature and intensity of the inflammatory response varied widely; however, duodenal biopsies from a subset of patients (37%) revealed marked acute inflammation that was associated with concomitant cytomegalovirus infection. Although duodenal infection was common (93% of individuals), infection of other sites was variable (gastric cryptosporidiosis in 40% and colonic cryptosporidiosis in 74%). Widespread infection of the intestinal tract, which included both the large and small intestine, was associated with the most severe diarrheal illness.

CONCLUSIONS

Cryptosporidium infection produces histologic evidence of gastrointestinal mucosal injury. The inflammatory response to the infection is variable, and may be modified by copathogens such as cytomegalovirus. The clinical manifestations are influenced, in part, by the anatomic distribution of the infection, with extensive infections involving both small and large intestines producing the most severe illness.

Cryptosporidium parvum is cytopathic for cultured human biliary epithelia via an apoptotic mechanism

While the clinical features of sclerosing cholangitis secondary to opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which microbial pathogens such as Cryptosporidium parvum associated with this syndrome actually cause disease are obscure. We established an in vitro model of biliary cryptosporidiosis employing a human biliary epithelial cell line. Using morphological and biochemical techniques, we examined the interaction of C. parvum with cultured human cholangiocytes. When the apical plasma membrane of polarized, confluent monolayers of human biliary epithelial cells was exposed to C. parvum oocysts that had been excysted in vitro, sporozoites attached to and invaded the cells in a time-, dose-, temperature-, and pH-dependent manner. The infectious process was both plasma membrane domain- and cell-specific, because no attachment or invasion occurred when the basolateral membrane of cholangiocytes was exposed to the parasite, or when a human hepatocyte cell line (HepG2) was used. Time-lapse video microscopy and scanning electron microscopy (SEM) showed that sporozoite attachment was rapid, involved extensive cholangiocyte membrane ruffling, and culminated in parasite penetration into a tight-fitting vacuole formed by invagination of the plasma membrane similar to those found in naturally occurring infection in vivo. Transmission electron microscopy (TEM) showed that C. parvum organisms formed parasitophorus vacuoles and were able to undergo a complete reproductive cycle, forming both asexual and sexual reproductive stages. Unexpectedly, direct cytopathic effects were noted in infected monolayers, with widespread programmed cell death (i.e., apoptosis) of biliary epithelial cells as assessed both morphologically and biochemically beginning within hours after exposure to the organism. The novel finding of specific cytopathic invasion of biliary epithelia by C. parvum may be relevant to the pathogenesis and possible therapy of the secondary sclerosing cholangitis seen in AIDS patients with biliary cryptosporidiosis.

Cholestatic jaundice due to congenital Toxoplasma gondii infection

A case of congenital toxoplasmosis manifesting as hepatosplenomegaly and cholestatic jaundice in a 4 month old child is reported. To the best of our knowledge this is the first report of cholestatic jaundice due to congenital toxoplasmosis from India. The child was successfully treated with sulphadiazine and pyremethamine combination.

Prevalence of IgG and IgM anti-Toxoplasma antibodies in patients with HIV and acquired immunodeficiency syndrome (AIDS)

With the emergence of the human immunodeficiency virus (HIV), in patients with acquired immunodeficiency syndrome (AIDS), Toxoplasma gondii has arisen as an important opportunist pathogenic agent, especially in the central nervous system, being the most common cause of intracerebral lesions. The incidence of Toxoplasma gondii in HIV-infected patients depends principally on the existence of latent Toxoplasma parasitosis in the population affected. Through the enzyme-linked immunosorbent assay (ELISA), IgG and IgM anti-Toxoplasma antibodies were found in 92 patients of which 46 (50.0%) were IgG seropositive, and only one case (1.0%) had IgM antibodies. Of the 92 patients: 53 were HIV seropositives and 39 had AIDS. The detection and monitoring of anti-Toxoplasma antibodies in HIV patients is essential, since in this group there is a high percentage risk of developing cerebral toxoplasmosis, which is the second cause of death in this type of patients.

Molecular diagnosis of gastrointestinal infections associated with HIV infection

Developments in medical microbiology in the past 20 years have had a profound impact on our understanding of infectious diseases and have led the way in the development of new diagnostic techniques. Molecular diagnostic techniques are generally more sensitive, specific, and rapid than conventional methods by which infectious agents are detected. For many of the opportunistic infectious agents of the gastrointestinal tract found in HIV-infected individuals, the application of molecular diagnostic techniques to the clinical laboratory is in its infancy. In this article, methods by which these techniques can be evaluated are demonstrated, and the current status and potential future application of these techniques for each gastrointestinal opportunistic pathogen are described.

The pancreas in AIDS

Although autopsy studies reveal significant pancreatic lesions in about 10% of AIDS patients, pancreatic lesions infrequently produce symptoms and are rarely recognized premortem. Patients with AIDS can develop pancreatic disease from causes not related to AIDS or AIDS-specific lesions. AIDS-specific causes include opportunistic infection, AIDS-associated neoplasia, and medications used to treat complications of AIDS. Pancreatic involvement is usually part of a widely disseminated tumor and rarely produces clinical symptoms.

Persistent diarrhea caused by Isospora belli: therapeutic response to pyrimethamine and sulfadiazine

A 54-year-old human immunodeficiency virus (HIV)-positive homosexual man developed overwhelming watery diarrhea and marked weight loss over a 3-week period. Although Entamoeba histolytica and other nonpathogenic enteric protozoa were observed along with Isospora belli in this patient's stool specimens, they were promptly eradicated after metronidazole (flagyl) treatment. The presence of I. belli oocysts in various stages of development in the stool and clinical symptoms related to Isospora infection persisted for 10 more months despite treatment with combined chemotherapeutic agents. Clinical and parasitiological resolution was ultimately achieved through an 8-week course of pyrimethamine and sulfadiazine.

Jejunal water and electrolyte transport in human cryptosporidiosis

Cryptosporidiosis may have severe clinical consequences in both immunocompromised and immunocompetent individuals. However, pathophysiological mechanisms that are responsible for diarrhea are poorly understood. We performed jejunal perfusion studies in patients with human immunodeficiency virus-related cryptosporidial diarrhea to measure water and electrolyte transport in vivo. Five patients with human immunodeficiency virus-related cryptosporidiosis and nine healthy volunteers were studied using a triple-lumen steady-state jejunal perfusion technique. Stool volume measurement and distal duodenal biopsy showed that the patients had diarrhea (600-1500 ml/24 hr) and morphological abnormalities of small intestinal mucosa. Net water, sodium, and chloride movement in the jejunum was not significantly different from healthy controls. In these patients with watery diarrhea and morphological mucosal abnormalities, we found no evidence that cryptosporidial diarrhea was due to a secretory state in the proximal small intestine. We conclude that diarrhea may be due to secretion of electrolytes and water efflux more distally or to other abnormalities of gastrointestinal function.

Prevalence, detection and control of Cryptosporidium parvum in food

The role of Cryptosporidium parvum as a foodborne pathogen has not been well documented. Epidemiological features of this parasitic protozoon lead to the assumption that the incidence of cryptosporidiosis due to contaminated food is under-estimated. The high prevalence of C. parvum among dairy herds has increased the spread of oocysts in the farm environment, and their potential presence in raw milk and other raw foods. In October 1993, the first well-documented foodborne outbreak was reported in Maine, USA, and was caused by contaminated hand-pressed apple cider. Although various cases of cryptosporidiosis among humans have pointed to raw milk and other raw foods as possible sources of infection, a conclusive demonstration of foodborne cryptosporidiosis has rarely been established. The limited numbers of oocysts in the suspected samples and the lack of sensitive detection methods adapted for oocyst detection in food contribute to this under-reporting. This review paper discusses various aspects of Cryptosporidium spp. and cryptosporidiosis, including the routes of transmission, the control of oocysts in food, and the available detection methods. The polymerase chain reaction (PCR) combined with DNA probe hybridization is a promising detection method. Recent knowledge on the molecular biology of the parasite for the development of new PCR assays and their potential use in the detection of C. parvum in food are described.

Intracellular protozoan infection in small intestinal biopsies of patients with AIDS. Light and electron microscopic evaluation

Small intestinal biopsies of 21 patients with acquired immunodeficiency syndrome (AIDS) with light microscopic findings diagnostic or suspicious for parasite infection were investigated by transmission electron microscopy (TEM). TEM allowed us to identify and specify the genus and species of involved parasites in 16 out of the 21 cases: 7 Cryptosporidium parvum, 5 Enterocytozoon bieneusi and 4 Isospora belli. Cryptosporidium was easily identified on light microscopy (LM), and only slightly influenced by parasite burden in all the 7 cases; TEM confirmed LM diagnosis and made it possible to characterize the parasites as C. parvum. The identification of Microsporidium on LM in our cases was related to the burden of parasite; its presence was certainty identified in 2 cases and suspected in 3. TEM allowed to identify these parasites as E. bieneusi. Intracytoplasmic coccidia could be detected with certainly in semithin sections in all 4 cases, but TEM was always needed to specify the infectious agent as I. belli. In 5 cases the suspicious of protozoan infection on LM (3 microsporidia, 1 intracytoplasmic coccidia and 1 Cryptosporidium) was not confirmed by TEM. Our data suggest that TEM is an appropriate diagnostic tool in this field of pathology and necessary in most of the cases.

Precipitous visual loss secondary to optic nerve toxoplasmosis as an unusual presentation of AIDS

Life-threatening conditions requiring urgent medical treatment rarely present to the ophthalmologist. This case report describes a patient with precipitious visual loss as the primary complaint and which subsequently led to the diagnosis of Toxoplasmic papillitis and life-threatening cerebral involvement as an initial manifestation of AIDS.

The relevance of laboratory diagnosis of human cryptosporidiosis and other coccidia

Human infection by Cryptosporidium spp and other coccidia are due to opportunist non-host specific microorganisms. In HIV seropositive patients, the gastrointestinal symptoms accompanying such infections may be serious and prolonged and may include nausea, low-grade fever, abdominal cramps, anorexia and watery diarrhoea. We studied 188 stool samples from 111 patients (84 men and 27 women) with diarrhoea. A modified Ziehl-Nielsen technique for the detection of Cryptosporidium spp and Isospora belli was employed. The mean age of the patients was 31 years. Cryptosporidium spp was seen in 18% (n = 20) of the patients, 90% (n = 18) of whom were HIV seropositive. Isospora belli was recorded only from HIV seropositive patients (5.4% of all the patients studied and 6.5% of those who were HIV seropositive). These data confirm the good results obtained with this technique for the identification of Cryptosporidium spp and other coccidia and also reaffirm the clinical importance of correctly diagnosing the cause of diarrhoea, particularly in HIV seropositive patients.

Toxoplasma gondii--an unusual cause of myocarditis in old age

We report the case of an 86-year-old man who was admitted with congestive cardiac failure and chronic renal failure. He was previously known to have a thoracic aortic aneurysm and chronic bronchitis. There was no history of myocardial infarction but his heart failure was assumed to be due to ischaemic heart disease. Despite treatment of the heart failure the patient died. At post-mortem he was found to have Toxoplasma gondii myocarditis.

Intestinal and extraintestinal Isospora belli infection in an AIDS patient. A second case report

A 30-year-old black female, from Burkina Faso, had AIDS in 1990. She died in March 1993 following a cachexia secondary to a chronic intestinal isosporiasis. The autopsy revealed a massive parasitic infection by I. belli of the small intestine mesenteric and mediastinal lymph nodes and liver and spleen. The parasite stage observed in extra intestinal sites corresponded to unizoite tissue cysts. This is the first report of I. belli infection in liver and spleen.

Cryptosporidium antigen detection in human feces by reverse passive hemagglutination assay

A reverse passive hemagglutination (RPH) assay was developed for Cryptosporidium oocyst antigen with an antioocyst monoclonal antibody (MAb; MAb-C1) coupled to stabilized sheep erythrocytes. RPH was compared with microscopy of auramine-phenol-stained smears of 56 oocyst-positive fecal samples, each of which was tested blindly by RPH with two oocyst-negative samples received on the same day (a total of 112 controls). Thirty-nine additional fecal samples from human immunodeficiency virus type 1 antibody-positive patients with diarrhea (10 of which were positive in auramine-phenol-stained smears) were stored at -20 degrees C before testing. Thirty specimens with a variety of other fecal pathogens (all negative for oocysts) were also tested. Of the 237 samples tested, 69 were positive by one or both methods: 65 by RPH and 66 by microscopy. The kappa coefficient of agreement between the methods was very high at 0.926. The sensitivity of RPH was 93.9%, the specificity was 98.2%, the positive predictive value was 95.4%, and the negative predictive value was 97.7%. Visible oocyst numbers and RPH titers were measured after storage of fecal samples and oocyst concentrates for 8 days at 4 degrees C. Oocyst morphology was generally poor in specimens from the human immunodeficiency virus type 1 antibody-positive group, and it degenerated during the 8-day storage experiments. MAb-C1-reactive antigen eluted from oocysts to give progressively higher reciprocal titers during storage, and it was partially removed from the oocysts by concentration. RPH is a promising technique for the detection of Cryptosporidium antigen in human feces and may be useful when specimens are stored before testing. Studies of the sensitivity of Cryptosporidium immunoassays should take into account the possible release of antigen from oocysts.

Municipal drinking water and cryptosporidiosis among persons with AIDS in Los Angeles County

To assess unfiltered drinking water as a source of cryptosporidium infection in patients with the acquired immunodeficiency syndrome (AIDS) the prevalence of cryptosporidiosis among persons with AIDS in Los Angeles County was assessed by water service area. One water distributor, serving approximately 60% of the county's residents (area B), has consistently employed filtration. The other company, which serves the remainder of the county (area A), did not institute filtration until mid-December 1986. This difference provided a 'natural experiment' in which to assess the effect of municipal water filtration on the level of cryptosporidiosis among persons with AIDS. The prevalence of cryptosporidiosis among AIDS patients was compared for the two water service areas for the time period (1983-6) preceding the implementation of filtration in area A. From 1983 to 1986 the age-standardized prevalence of cryptosporidiosis among AIDS patients was 32% lower in area A (4.2%), which received unfiltered water, than in area B (6.2%). Following addition of filtration in area A, the prevalence of cryptosporidiosis among AIDS patients decreased by 20%; however, a decline, of 47%, was also observed in area B. The similar baseline levels of cryptosporidiosis and the corresponding post-filtration decline in both areas suggest that filtration had no effect on levels of cryptosporidiosis among persons with AIDS. Thus it does not appear that municipal drinking water is an important risk factor for cryptosporidiosis in AIDS patients residing in Los Angeles County.

Parasitic gastroenteritis

Parasitic causes of diarrhea are common in pediatric patients and have important public health implications. Therefore, diagnosis should be pursued vigorously in the appropriate clinical setting. Giardia and Cryptosporidium infections are the most common causes of disease in the United States, and stool examination for ova and parasites is the best way to make the diagnosis. This should be performed three times, on alternate days, in order to rule out parasitic disease with confidence. In treatment of Giardia, it is important to interrupt transmission, particularly in the day-care setting. Because of the potential for major outbreaks, patients with cryptosporidiosis should be kept out of day care until their symptoms resolve. Although amebiasis is not a common problem in the United States, all patients with bloody diarrhea who have traveled to, or are from, endemic areas should be tested for amebiasis by serology and stool examination. If patients with suspected inflammatory bowel disease are being considered for therapy with corticosteroids, mucosal scrapings of colonic lesions should be examined for amoebae, because corticosteroid therapy can lead to more invasive amoebic disease. Acquired immunodeficiency syndrome patients with diarrhea can be infected with a number of pathogens and a specific diagnosis should be pursued aggressively. These patients are often infected with one or more of the parasites described in this article. The approach to diarrhea in these children is described in a separate article of this issue (Deveikis A. 'Gastrointestinal Disease in Immunocompromised Children," pages 562-569).

Submicroscopic profile of Isospora belli enteritis in a patient with acquired immune deficiency syndrome

Small bowel mucosal fragments from a human immunodeficiency virus-positive female patient with chronic diarrhea were investigated by transmission electron microscopy, and Isospora belli enteritis was documented. The submicroscopic profile was characterized by a moderate abnormality of mucosal architecture with reduction in height of villi and hypertrophy of crypts. Stages of both asexual (trophozoite, schizont and merozoite) and sexual (macrogametocyte) phases of the life cycle of the parasite were identified in the epithelium, always enclosed within a parasitophorous vacuole. Moreover, the presence of occasional extracellular merozoites in the intestinal lumen and in the lamina propria near or within lymphatic vessels was documented. These findings expand the current knowledge of this parasite regarding its capacity to survive in an extracellular environment and document a possible mechanism by which extraintestinal infection can take place.

Update on the management of intestinal cryptosporidiosis in AIDS

OBJECTIVE

To update readers on the pharmacotherapeutic management of cryptosporidiosis in patients with AIDS.

DATA SOURCES

A MEDLINE search was used to identify pertinent literature. Additionally, programs and abstracts from the 33rd Interscience Conference on Antimicrobial Agents and Chemotherapy; the 1st International Conference on Macrolides, Azalides, and Streptogramins; the 93rd American Society for Microbiology Meeting; and the 6th and 7th International Conferences on AIDS were used.

DATA EXTRACTION

Available data from in vitro, animal, and human experiments were reviewed.

DATA SYNTHESIS

Intestinal cryptosporidiosis in patients with AIDS can be a life-threatening opportunistic infection. However, there can be significant variability in disease expression, including spontaneous remission. Supportive care with hydration and nutritional supplementation remains a hallmark of therapy. Unfortunately, there is no proven specific pharmacotherapy of cryptosporidiosis in patients with AIDS. Numerous agents have been analyzed for in vitro activity and efficacy in experimental animal models and actual human cases of the infection, including paromomycin, azithromycin, clarithromycin, octreotide, hyperimmune bovine colostrum, bovine transfer factor, and many others. Because limited numbers of controlled trials have been conducted with potential therapeutic agents, the majority of the information to date is preliminary in nature.

CONCLUSIONS

Despite the availability of some evolving and potentially promising treatment modalities, further controlled clinical trials are necessary to evaluate the role of pharmacotherapy for intestinal cryptosporidiosis in patients with AIDS.

Infection dynamics and clinical features of cryptosporidiosis in SCID mice

Cryptosporidial infections in severe combined immune deficient (SCID) mice produce a chronic disease state which in the later stages leads to extraintestinal involvement and hepatic dysfunction. To further characterize the infection dynamics in this model and monitor the changes in the hepatic system, a dose titration of the oocyst inoculum was performed and alkaline phosphatase levels in the sera were assayed. Ten SCID mice per dose were inoculated with 10(3), 10(4), 10(5), 10(6), or 10(7) oocysts. Oocyst shedding in the feces was quantified by microscopic enumeration. Mice inoculated with 10(6) oocysts and those inoculated with 10(7) oocysts demonstrated similar oocyst shedding patterns, but the 10(7)-oocyst group exhibited signs of distress (e.g., weight loss and icterus) earlier. The intensity of the infection increased markedly approximately 14 days postinoculation (p.i.) and continued to increase steadily over the next 6 weeks. Inoculation with lower oocyst doses produced a delay in patency (e.g., it occurred 7 days later with the 10(5)-oocyst inoculum and 14 days later with the 10(4)-oocyst inoculum). Mean serum alkaline phosphatase levels in the 10(7)-oocyst group were more than twice control values at 5 weeks p.i. and continued to increase over the next 8 weeks. Oocyst doses and alkaline phosphatase levels were positively correlated with hepatobiliary colonization (r = 0.71) and liver necrosis (r = 0.65) at 13 weeks p.i. A strong positive correlation between hepatobiliary colonization and liver necrosis at 13 weeks p.i. (r = 0.87) was observed.

Retinochoroiditis in the acquired immune deficiency syndrome. Findings in consecutive post-mortem examinations

A number of opportunistic agents may cause retinitis or retinochoroiditis in patients with the acquired immunodeficiency syndrome. Minimal consecutive data is available on the histopathologically confirmed prevalence of these ocular infections. A total of 48 consecutive patients with acquired immunodeficiency syndrome-related death underwent autopsy and had their eyes submitted for histopathological examination. Conventional light microscopy combined with immunohistochemistry revealed cytomegalovirus retinitis in 15 patients, toxoplasma gonddi retinochoroiditis in 3 patients and mycobacterial choroiditis in one individual with some infections being coexistent. Clinical examination prior to death was highly accurate in detecting cytomegalovirus retinitis, but failed to determine all non-cytomegalovirus causes of retinochoroiditis. Ten of 15 patients with cytomegalovirus retinitis had associated non-cular cytomegalovirus infections, most often in the brain and adrenals. After clinical detection of cytomegalovirus retinitis the median survival time was 5.5 months, not adversely affected by additional non-ocular cytomegalovirus infection.

Toxoplasma gondii: susceptibility and development of resistance to anticoccidial drugs in vitro

Anticoccidial drugs were evaluated for activity and for the development of resistance in a model of Toxoplasma gondii growing in human fibroblast cultures. Of 13 anticoccidial drugs tested, 9 had selective antitoxoplasma activity (50% inhibitory concentration, in micrograms per milliliter): decoquinate (0.005), arprinocid-N-oxide (0.015), robenidine (0.03), the aryl triazine CP-25,415 (0.2), toltrazuril (0.4), clopidol (1), dinitolmide (Zoalene; Dow) (10), and the carboxylic acid ionophores monensin (0.001) and salinomycin (0.04). Glycarbylamide, amprolium, nicarbazin, and the 6-(p-bromophenoxy)-7-chloro analog of halofuginone (Stenorol; Roussel-UCLAF) (CP-63,567) were toxic for the fibroblasts. Since Eimeria tenella has a similar drug susceptibility profile, anticoccidial drugs can be viewed as a potential source of new antitoxoplasma therapies. The development of resistance has limited the usefulness of most of these drugs as anticoccidial agents; in coccidia, resistance to all except the ionophores occurs readily in vivo. We explored the development of resistance in T. gondii by attempting to select mutants in vitro from parasites mutagenized with ethylnitrosourea. Mutants that had 20- to 50-fold-reduced susceptibility to decoquinate, arprinocid-N-oxide, and CP-25,415 were obtained. Ionophore-resistant T. gondii mutants were also selected in vitro; however, there was only a twofold difference in susceptibility between these mutants and the wild type. For three drugs (clopidol, robenidine, and toltrazuril), we were unable to select resistant mutants. For experimental anticoccidial drugs, there is currently no in vitro method for assessing the risk of development of resistance in Eimeria species. Our results suggest that T. gondii may offer a useful surrogate for this assessment.