Cryptosporidium species a "new" human pathogen

Sheep as a source of human cryptosporidiosis

Studies in north Wales on human cryptosporidiosis since 1983 have indicated that the infection may be acquired both from animals and by person-to-person transmission. Examination of veterinary data revealed a marked coincidence of the spring peak of infection in human beings with that seen in sheep. A case-control study was therefore set up to test the hypothesis that some of the human infections may have been acquired from contact with sheep. The results of the study confirmed a significant association.

Cryptosporidiosis in children of eastern India

Cryptosporidium infection was found in association with acute diarrhoeal disease in ten patients (13%) of a total of 77 children below the age of 8 years admitted over a period of 1 year to Bhubaneswar Capital Hospital, Orissa state, India. Contrary to another report from South India, there were no asymptomatic cryptosporidium oocyst excretors detected either in the matched control group of 42 children without diarrhoea or in a group of 113 healthy school children investigated. A clustering of seven cases occurred in the months of the rainy season and of three cases in the winter months. Nine out of 63 children (14.3%) below the age of 2 years were infected. Seven of the ten infected children were significantly below their expected weight-for-age, but the mean weight-for-age did not differ from those of the uninfected children. The possible epidemiological factors in the transmission of cryptosporidium are discussed.

Cryptosporidiosis in Great Yarmouth--the investigation of an outbreak

A community outbreak of 36 cases of Cryptosporidium infection which occurred during Spring 1986 in Great Yarmouth and Waveney is described. A period prevalence study suggested that there was a more widespread outbreak of diarrhoeal illness in the locality although only 3/68 stool samples obtained at a median time interval of 38 days from the onset of symptoms contained Cryptosporidium oocysts. The distribution of cases of cryptosporidiosis in time and place suggested person to person spread rather than a common vehicle. A retrospective matched case-control study provided no evidence of water borne spread.

Comparison of three methods for detection of Cryptosporidium oocysts in a low-prevalence population

Four hundred fecal specimens which had been received for routine ova and parasite examination were concentrated by Formalin-ether sedimentation. Sediments were examined as saline and iodine-stained wet preparations and were stained with rhodamine-auramine O and a commercially available monoclonal fluorescent-antibody stain for oocysts of Cryptosporidium species. Examination with the fluorescent stains detected cryptosporidia in both positive specimens (0.5% prevalence), and routine direct wet-preparation examination detected cryptosporidia in one of them. Detection of only low numbers of positive specimens in our nonrisk population argues against routine use of specific and expensive stain reagents.

Investigating gastroenteritis: the Merseyside experience 1983-1987

Outbreaks of gastroenteritis may lead to serious disruption when many persons are absent from work or school. The illness may be life-threatening, particularly in the very young and very old. Control of gastroenteritis associated with microbial infection is therefore an important aspect of preventive medicine. Laboratory investigations are necessary to establish the source of an outbreak, to determine whether chemotherapy is necessary as it is in, for example, Giardia lamblia infection and to identify long-term changes in the pattern of infections related to altered dietary habits and other social factors. In this survey we draw attention to the many infective agents which have to be considered in the investigation of cases and outbreaks of gastroenteritis. The examination of faecal samples in the microbiology laboratory is becoming increasingly complex requiring as it does the use of additional new techniques for previously unrecognised bacterial, viral and protozoal causes of gastroenteritis including, in the last two decades, Campylobacter, Clostridium difficile, rotavirus, Norwalk virus and Cryptosporidium. These investigations are however expensive and in the face of increasing pressure to economise, it is of paramount importance that the best use should be made of the resources available. To this end we make recommendations about the information that should accompany faecal and other samples submitted to the laboratory from outbreaks of gastroenteritis.

Susceptibility of germfree or antibiotic-treated adult mice to Cryptosporidium parvum

Adult mice are more resistant than neonatal mice to intestinal colonization with the protozoan parasite Cryptosporidium parvum. Development of a mature intestinal flora may play a role in this resistance. We compared susceptibilities to colonization with C. parvum in adult conventional mice, adult germfree mice, and adult conventional mice treated with oral antibiotics to deplete the intestinal flora. Germfree mice of both CD1 and BALB/c strains were colonized at day 7 following inoculation with C. parvum oocysts isolated from the feces of an infected, diarrheic calf. Age-matched conventional mice of the same strains were comparatively resistant to colonization. Conventional mice treated with antibiotics remained resistant to colonization. These results suggest that the microflora in the intestine was not the sole determinant of resistance or susceptibility to colonization. The germfree adult mouse as an experimental model of cryptosporidiosis is discussed.

Human cryptosporidiosis in North Queensland

During a 12-month period, feces from 780 persons from the Townsville region were evaluated by the Kinyoun acid-fast strain, and 36 (4.6%) immunocompetent patients were found to have Cryptosporidium oocysts. Twenty-five index cases were identified; 13 (8.6%) cases from 151 patients were from Palm Island, an isolated Aboriginal community in the wet tropics and 12 (1.9%) cases from 629 patients were from the dry tropics of Townsville. All 11 secondary cases were associated with a person-to-person outbreak in the nursery of a Townsville day-care centre. Infection occurred mainly in two distinct age groups: the under five-year-old (27 cases), and the 25 to 35-year-old (six cases). A prodrome of dry cough, rhinorrhea and vomiting often preceded symptoms of fever, weight loss, abdominal pain, persistent cough and vomiting, and acute diarrhea with frequent, non-bloodstained, watery, mucous stools. Although 13 patients were hospitalised because of their illness, the infection was self-limiting and all 36 patients recovered with symptomatic treatment. Cryptosporidium was the third most commonly identified enteric pathogen after Rotavirus and Giardia. Infection did not appear to depend on seasonal variation and no animal or environmental sources of infection were identified. Cryptosporidiosis in immunocompetent persons is endemic and common in North Queensland and routine investigations for this parasite in symptomatic patients are warranted.

Protozoal infections in the acquired immunodeficiency syndrome

Several protozoa have emerged as the major opportunistic infections and cause of death in patients with acquired immunodeficiency syndrome (AIDS). Pneumocystis carinii pneumonia is the leading cause of death in AIDS patients. Electron microscopy (EM) usually shows numerous trophozoites and cysts of Pneumocystis filling up the entire alveolar space, while only cysts are seen under the light microscope. The focal thickening of cyst wall of Pneumocystis, as demonstrated by EM and manifested as a "parentheses" shaped structure with silver stain, serves as a diagnostic marker for Pneumocystis. Freeze-fracture EM has demonstrated the intimate contact between Pneumocystis trophozoites and the type I pneumocytes, which may contribute to the alveolar-capillary block, leading to severe respiratory distress. However, EM is seldom needed for the diagnosis of this infection. Toxoplasma encephalitis, which is an unusual clinical manifestation in cases of toxoplasmosis reported previously, has become a common complication and one of the major causes of death in patients with AIDS. Because subclinical infection by Toxoplasma is common, serologic tests usually offer no definite answers as to whether the infection is acute or chronic, active or past. The small size and its non-specificity in both morphology and tissue affinity make light microscopic diagnosis of toxoplasmosis difficult. Only immunologic staining, such as immunoperoxidase and immunofluorescence, can help to achieve a definite positive identification of the organism. When special antibodies or facility for such staining is not available, EM is the final resort for identifying Toxoplasma by showing the apical complex with the characteristic sausage-shaped rhoptries. Cryptosporidiosis, practically unknown before the AIDS outbreak, has become one of the most common intestinal protozoa in both immunocompromised and immunocompetent patients. The protracted and sometimes fatal course of cryptosporidiosis in immunocompromised patients can be explained by the presence of autoinfective oocysts (thin-walled oocysts), as detected by EM, and by recycling of first-generation schizonts observed experimentally. While diagnosis of cryptosporidiosis can be made by detection of oocysts in stools in most cases, EM is still the last resort for a definitive identification of Cryptosporidium species. While the incidence of isosporiasis is still low, it has been found more frequently in patients with AIDS than in the general population. The parasite, Isospora belli, being a coccidian as is the Cryptosporidium species, is similar to the latter in its life cycle and clinical manifestations.(ABSTRACT TRUNCATED AT 400 WORDS)

Cryptosporidiosis in perspective

In this review I have examined the vast literature which has accumulated on Cryptosporidium, particularly in the past 3 years, in an attempt to highlight areas in which progress has been made in relation to the organism and the disease, and to indicate areas in which knowledge is still lacking. Since 1982, a global effort by scientists and clinicians has been directed towards determining the nature of the disease in humans and the relative contribution of cryptosporidiosis to gastroenteritis. From published data, the incidence of diarrhoea is 1-5% in most developed countries, and 4-7% in less developed countries, when measured throughout the year and in all age groups. The frequency of cryptosporidiosis is highest in children aged between 6 months and 3 years, and in particular locations (e.g., day-care centres) and at particular times of the year. Although susceptibility to infection is life-long, one suspects that the lower prevalence among older children and adults is due to immunity acquired from frequent exposure. Other important factors contributing to higher prevalence are the season--it is more frequent in a wet, warm climate--association with travel to particular destinations, poor hygiene, intimate contact with certain animals, and congregation of large numbers of young previously unexposed children in day-care centres. The association between cryptosporidiosis and giardiasis presumably results from the existence of a common source of infection. The immune status of the host appears to be a major determinant of whether the infection is self-limiting or persistent. It is clear that both branches of the immune system are required for complete recovery, since T-lymphocyte dysfunction or hypogammaglobulinaemia can both lead to persistent illness. Chronic diarrhoea and malabsorption attributed to cryptosporidiosis also occur in the absence of evidence of immune defect. The importance of respiratory tract infection in humans, other than in the terminal stages of chronic illness, requires investigation. The infection has now been identified in all classes of vertebrates; it has been observed in all domestic animals including pets, and a wide range of wildlife including birds. Cryptosporidiosis seems to cause diarrhoea in young ruminants, less frequently in pets. In birds the parasite has been observed in the gastrointestinal tract, without ill effect, and in the respiratory tract, in which clinical symptoms of variable severity have been described. The mucosal response of the gastrointestinal tract to infection appears to vary among mammals and may be the key to the variable clinical manifestations observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Human cryptosporidiosis

Cryptosporidium is an enteric coccidial protozoan recognized in humans in 1976. Since its manifestation as an acquired immunodeficiency syndrome (AIDS)-related infection, new diagnostic techniques have improved recognition of Cryptosporidium oocysts, making apparent its true prevalence in human populations. Cryptosporidium represents 5 to 15% of all enteric pathogens in children in warm climate countries. It is responsible for both endemic and epidemic disease. Day-care center spread is well known, and evidence is strong for person-to-person transmission. The spectrum of illness caused by Cryptosporidium is broad, and while self-limited in immunocompetent individuals, gastrointestinal symptoms can be severe. Asymptomatic infection has been described in population surveys and outbreak investigations. Severe dehydration with malabsorption and failure-to-thrive in children from developing countries has been attributed to this organism. Intractable, incurable diarrhea can be fetal in immunosuppressed adults. Cryptosporidiosis in human immunodeficiency virus-infected individuals is declining in frequency in New York City, possibly reflecting changing sexual behaviors and comparatively low infectivity. No effective treatment for Cryptosporidium has been documented, but clinical trials are in progress.

Cryptosporidiosis in the acquired immunodeficiency syndrome: a case report

A case of cryptosporidiosis in a male homosexual man with AIDS is reported. The clinical manifestations were anorexia, mild fever, abdominal pain and profuse watery diarrhea. The diagnosis was made in fecal smears by using a modified Ziehl-Neelsen method and a safranin-methylene blue staining technique.

Infectivity and neutralization of Cryptosporidium parvum sporozoites

Cryptosporidiosis, a diarrheal disease of calves and humans caused by the coccidian parasite Cryptosporidium parvum, is terminated in hosts with normal immune systems. To assess the mechanisms of immunity in cryptosporidiosis, it is necessary to isolate and quantitate sporozoites, the infective stage of Cryptosporidium spp. Here we report the (i) separation of infective C. parvum oocysts from calf feces by ether extraction, sieving, and hypochlorite treatment; (ii) separation of viable C. parvum sporozoites from intact and excysted oocysts by anion-exchange chromatography; and (iii) quantitation of sporozoite infectivity in vivo by direct intraintestinal injection of isolated sporozoites in 7-day-old BALB/c mice. When isolated sporozoites were incubated with heat-inactivated immune bovine serum, 25 times the 50% infective dose for 7-day-old mice was completely neutralized. Sporozoites incubated with preimmune bovine serum were infectious for 7-day-old mice.

The antibody response to Cryptosporidium: development of a serological test and its use in a study of immunologically normal persons

The demonstration of an immune response in the relatively newly recognised infection of human beings, cryptosporidiosis, is essential for assessing pathogenicity, for diagnostic purposes, and for epidemiological studies. In addition, serological methods may be applied to the detection and definitive identification of the parasite. Earlier reports were of histologically based methods with tissue from experimentally infected animals and did not define the nature of the response. The method described here is simple and rapid. It may be done in laboratories not equipped to perform the earlier methods. Results confirm that oocysts may be used to detect antibody in the blood of human beings, to determine when sero-conversion takes place and to define the nature of the response in terms of the class of immunoglobulin. Some sero-epidemiological observations have been made.

Acquired immunodeficiency syndrome of childhood

AIDS of childhood is reviewed in this timely article, including care of the child with infectious complications, and other current and future management concerns.

Cryptosporidium among children with acute diarrhoea in the west of Ireland

During a period of 12 months beginning on 18 February 1985, 1246 specimens of faeces from 935 children aged 3 weeks to 12 years with acute diarrhoea of varying severity were examined for the presence of cryptosporidium oocysts. Twenty-six patients required admission to hospital; four of them needed intravenous rehydration. Predominant clinical features were diarrhoea, often watery, and vomiting. Diarrhoea varied in duration between 7-15 days. Cryptosporidium oocysts were found in specimens from 41 patients, an incidence of 4.3%. In four patients an additional enteropathogen was identified (Campylobacter species in two and enteropathogenic Escherichia coli in two - serotypes 0126: K71 (B16) and 018C: K77 (B12]. None of the patients had recently travelled abroad. Of the children 23 were from a farming or rural background. Eight of the farms had recently had significant outbreaks of diarrhoea among calves. There was a marked seasonal variation with 27 of the cases arising between 18 February and 18 June, an incidence during this period of 8%.

Cryptosporidium spp. and cryptosporidiosis

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Remission of diarrhoea due to cryptosporidiosis in an immunodeficient child treated with hyperimmune bovine colostrum

A boy aged 6 months who presented with poor weight gain, diarrhoea, and infection with Pneumocystis carinii was found to have congenital hypogammaglobulinaemia, which did not improve despite monthly treatment with intravenous gammaglobulin. At the age of 3 years and 2 months he developed severe vomiting and diarrhoea due to cryptosporidiosis, which failed to respond to conventional treatment. Infusion of hyperimmune bovine colostrum produced against parasite antigen, given by nasogastric tube, was started after symptoms had persisted for three weeks. His vomiting and diarrhoea resolved within five days of treatment, and oocysts were no longer seen in the stools after eight days. Later, however, he developed a rare complication, and oocysts were found in the common bile duct. Hyperimmune bovine colostrum may be useful in the treatment of many patients with immunodeficiency disorders.

Experimental intrauterine infection of adult BALB/c mice with Cryptosporidium sp

Inoculation of adult, female BALB/c mice with 2 X 10(5) bleach-treated Cryptosporidium sp. oocysts isolated from calf feces resulted in infection of the uterine mucosa in more than 50% of the animals. Cryptosporidium sp. completed the entire life cycle in the uterus, and infectious oocysts were passed into the vagina. Two methods of application were used to establish intrauterine infection. The inoculum was either injected into the uterus after abdominal surgery or intracervically instilled. Mice were susceptible at all phases of the sexual cycle, but the highest infection rates were obtained during estrus and diestrus. Parasites were demonstrated as early as 5 days postinfection. Phagocytic cells in the uterine lumen and in the vagina contained Cryptosporidium sp. Phagocytosis may be an important immune response and a mechanism of parasitic clearance. These results suggest that Cryptosporidium sp. is a potential pathogen of the reproductive tract.