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Giardia intestinalis is one of the most common causes of parasite-induced diarrhea, abdominal pain, flatulence, and malabsorption. Yet, data on the epidemiology of G. intestinalis infections in North Africa are limited. The purpose of this study was to carry out a retrospective survey on the level of intestinal parasitism with a particular emphasis on G. intestinalis in children and adults in Algiers, Algeria. A total of 2,054 individuals from outpatient clinics or hospitalized at Beni-Messous University Hospital of Algiers undergoing stool microscopy for ova and parasites were included. The overall parasite infection rate was 28%. In the 567 parasite-positive samples, Blastocystis was found most frequently (57.3%), followed in frequency by Endolimax nana (41.0%), Entamoeba histolytica/dispar (19.6%), G. intestinalis (17.1%), Entamoeba coli (13.9%), Chilomastix mesnili (1.0%), Iodamoeba bütschlii (0.7%), Entamoeba hartmanni (0.5%), and Cryptosporidium spp. (0.2%). Intestinal parasites were generally more common in adults than in children, except for Giardia, which was more common in children (P = 0.0001). Giardia infection was independent of gender (P = 0.94). Compared with other intestinal parasitic infections, clinical manifestations, such as abdominal pain (P = 0.28) and diarrhea (P = 0.82), were found not to be significantly linked to Giardia infection. In conclusion, G. intestinalis is common in individuals referred to the University Hospital of Beni-Messous with digestive symptoms, particularly so in children. However, in our study, intestinal symptoms appeared not to be more linked to Giardia than to other intestinal parasites.

A prospective, comparative study of the prevalence of enteric protozoa was determined among human immunodeficiency virus (HIV)-positive and HIV-negative men who have sex with men (MSM) in Sydney, Australia. A total of 1,868 patients submitted stool specimens; 1,246 were from MSM (628 HIV positive and 618 HIV positive) and 622 from non-MSM were examined over a 36-month period. A total of 651 (52.2%) stool specimens from MSM were positive for protozoa compared with 85 (13%) from non-MSM. There was a significant difference in the prevalence of Blastocystis hominis, Endolimax nana, Entamoeba histolytica/dispar complex, Entamoeba hartmanni, Iodamoeba butschlii, and Enteromonas hominis detected between MSM and non-MSM (P < 0.001). The only notable difference between HIV-negative and HIV-positive MSM was that HIV-infected MSM were found to more likely have a Cryptosporidium parvum infection. Entamoeba histolytica was found in 3 patients, E. dispar in 25, and E. moshkovskii in 17, all of whom were MSM. When compared with a control group, MSM were significantly more likely to harbor intestinal protozoa and have multiple parasites present. The results of this study show high rates of enteric parasites persist in MSM and highlight the importance of testing for intestinal parasites in MSM. This is the first report of E. moshkovskii from MSM. Copyright © 2007 by The American Society of Tropical Medicine and Hygiene.

Conclusions and Summary In a series of 202 post-mortem examinations conducted on accident cases in New Orleans within four hours after death, thirteen infections of Endamoeba histolytica (6.44 per cent) were demonstrated by the recovery of the organism within the bowel. In five of these cases the ameba was found in scrapings of lesions in the bowel wall. In two additional cases the organism was identified from mucus removed from the surface of lesions or nearby. In four more cases E. histolytica was recovered from feces or mucus throughout extensive lengths of the large intestine, and in each of two instances only a single cyst was diagnosed. Thus, in five of the thirteen individuals positive for E. histolytica, and possibly in two more, there was concrete evidence of tissue invasion; in four cases large numbers of amebae were found without direct proof of associated lesions; and in each of two additional cases the discovery of a single cyst in hematoxylinstained fecal films of intestinal feces suggested minimal infection without evidence of tissue invasion or possibly in one case transit of the cyst through the digestive tract without excystation. There was no evidence of a relationship between the racial size of the amebae and their ability to invade the intestinal wall. The highest percentage of positive diagnoses was made on iodine-stained fresh wet preparations filmed from feces and mucus taken at representative levels of the bowel. However, hematoxylin films of intestinal feces were responsible for three positive diagnoses which would otherwise have been missed. Fresh wet films prepared from feces and mucus in the lumen and superficial scrapings of the mucosa at different levels of the bowel constitute a reliable, rapid technic for recovery and diagnosis of E. histolytica in post-mortem examinations made within four hours after death. Moreover, this method provides a more accurate diagnosis than routine gross inspection of the bowel wall for lesions supplemented by sections of fixed material. The intestinal lesions demonstrated in this series were confined exclusively to the mucosa, and consisted of three varieties, (1) minute pinpoint lesions, (2) shallow craters, and (3) rather extensive, superficial erosive processes. In each of these types of tissue involvement amebae were demonstrated and in no instance was there evidence of leukocytic infiltration suggesting secondary invasion by bacteria, or of fibrous repair processes. No amebiasis of the liver was discovered in any of the members of this series. Although previous investigators have studied the pathology in so-called “symptomless carriers” of Endamoeba histolytica, they have invariably reported appreciable involvement of the bowel wall with “typical amebic ulceration.” The amebic processes demonstrated in this series constitute much milder, less advanced pathology and suggest a better balance between host tissue and the parasite. As in early experimental amebic lesions in the dog, so in this series there is a preponderance of lesions in the cecum-appendix area. In addition to Endamoeba histolytica the following intestinal parasites were identified in the present series: E. coli, 6.44 per cent; Endolimax nana, 9.4 per cent; Iodamoeba butschlii, 1.0 per cent; Dientamoeba fragilis, 0.5 per cent; Giardia lamblia, 4.5 per cent; Trichomonas hominis, 1.0 per cent; flagellate sp. inq., 0.5 per cent; Necator americanus, 1.9 per cent; Ascaris lumbricoides, 1.5 per cent; Trichocephalus trichiurus, 1.9 per cent; Enterobius vermicularis, 0.5 per cent, and Strongyloides stercoralis, 0.5 per cent. Forty-two members of the series were positive for one or more parasites, giving a parasite index of 0.36 for the entire group of 202 and an index of 1.74 for the infected individuals.

Summary The trophozoites of E. histolytica, E. coli and E. nana and of Dientamoebae fragilis have been observed in aqueous smears and the essential findings recorded. Material for a similar study of the trophozoites of Iodamoeba butschlii has not been available. The observations indicate that certain features in the morphology of the amoebae can be demonstrated in the aqueous medium, such as (1) the distensibility of the ectoplasm of the E. histolytica, (2) the relative fragility of the ectoplasm of the E. coli and E. nana, (3) the resiliency of the ectoplasm of the Dientamoeba fragilis, (4) the remarkable strength of the nuclear membrane of the E. histolytica and E. coli. Some of these characteristics together with the visibility of the nuclei help to differentiate the species of amoebae in the human stool. It also has been recorded that the annoyance of Blastocystis hominis can be eliminated by the use of the aqueous smear. I have been unable to find any reference in the literature to the use of aqueous smears in the study of the amoebae of man. However, it does not seem possible that such a simple procedure has not been used by some workers. It is my pleasure to acknowledge the generous and valuable advice of Dr. C. M. Johnson, protozoologist at the Gorgas Memorial Laboratory and the efficient assistance of J. F. Buckner and H. A. Down of the Hospital Corps, U. S. Navy.

Summary A study of Endamoeba histolytica and other intestinal parasites was conducted in two very similar urban housing projects, one inhabited by Negro and the other by white families, with the following results: 1. Observed prevalences of the intestinal parasites for this urban population were: E. histolytica, 3.5 per cent; Endamoeba coli, 13.9 per cent; Endolimax nana, 11.9 per cent; Iodamoeba butschlii, 1.1 per cent; Giardia lamblia, 5.0 per cent; and Chilomastix mesnili, 0.7 per cent. 2. The higher prevalence rates for E. histolytica and E. nana and the lower rate for E. coli in the white population were not significant statistically; however, other factors operating in the two populations which suggest the possibility of real racial differences are discussed. 3. Overall prevalence rates were much lower than those found in rural communities of the mid-south but the sex and age distributional patterns were, in general, the same. 4. The helminths occurred infrequently probably because of the excellent sanitary facilities. 5. The occurrence of diarrhea and E. histolytica infection were associated to a marked degree, but no further association between symptoms and parasites could be established.

Summary and Conclusions Estimations of efficiency of the formalin-ether sedimentation concentration procedure for the detection of ten common intestinal parasites have been determined from an analysis of data obtained in multiple-stool examination series. Approximately 1,000 residents of four, rural, Japanese villages were examined in two five-stool series and findings were analyzed by the maximum-likelihood method of Sawitz and Karpinos. Mean estimates of efficiency for the detection of protozoan cysts were comparable to those computed by other investigators for the ZnSO4 centrifugation-flotation technic. These estimates, in per cent, for the formalin-ether procedure were 60.2 for Entamoeba histolytica; 75.1 for E. coli; 60.4 for Endolimax nana; 55.7 for Iodamoeba butschlii; and 44.5 for Giardia lamblia. Corresponding figures for helminths were: 91.9 for Ascaris lumbricoides; 92.2 for Trichuris trichiura; 78.9 for hookworm; 41.1 for Trichostrongylus sp.; and 47.6 for Schistosoma japonicum. The efficiency of the formalin-ether procedure for the detection of some organisms, especially protozoan cysts, was observed to vary and, in some instances, the differences were probably significant. These variations are assumed to be due to a combination of factors including technical error, limitations of the analytical method and the examination procedure itself, possible biologic characteristics of the organisms that might affect their detection, and normal fluctuations in the mean infection intensity in the different population groups. Re-examination of about one-half of the people within 60 days after the initial examination series permitted a better estimate of the reliability of the technic. The number of additional infections detected in the second examination series was about equal in all instances to the number of cases present in the first series, but absent in the second. The rate of misses for E. histolytica was no greater than the rate for more easily recognized forms. On the basis of the latter data, it was estimated that examination of five separate stools by the formalin-ether technic will detect about 97 per cent of amebiasis cases in a population. Similar data were also obtained for the other nine parasites.