Free-living amoebae as opportunistic and non-opportunistic pathogens of humans and animals.

Giardia lamblia is both the most common intestinal parasite in the United States and a frequent cause of diarrheal illness throughout the world. In spite of its recognition as an important human pathogen, there have been relatively few agents used in therapy. This paper discusses each class of drugs used in treatment, along with their mechanism of action, in vitro and clinical efficacy, and side effects and contraindications. Recommendations are made for the preferred treatment in different clinical situations. The greatest clinical experience is with the nitroimidazole drugs, i.e., metronidazole, tinidazole, and ornidazole, which are highly effective. A 5- to 7-day course of metronidazole can be expected to cure over 90% of individuals, and a single dose of tinidazole or ornidazole will cure a similar number. Quinacrine, which is no longer produced in the United States, has excellent efficacy but may be poorly tolerated, especially in children. Furazolidone is an effective alternative but must be administered four times a day for 7 to 10 days. Paromomycin may be used during early pregnancy, because it is not systematically absorbed, but it is not always effective. Patients who have resistant infection can usually be cured by a prolonged course of treatment with a combination of a nitroimidazole with quinacrine.

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Treatment of Giardiasis

The coccidian parasite Cyclospora cayetanensis is recognized as an emerging pathogen that causes protracted diarrhea in humans. The first cases of Cyclospora infection were reported in the late 1970s and were observed among expatriates and travelers in regions where infections are endemic. Since then, Cyclospora has been considered a cause of traveler's diarrhea. Epidemiological investigations were reported and examined in areas of endemicity even before the true identity of Cyclospora was elucidated. Cyclospora was fully characterized in the early 1990s, but it was not until the 1995 Cyclospora outbreak in the United States and Canada that it caught the attention of the public and physicians. The biology, clinical presentation, epidemiology, diagnosis, treatment, and control of cyclosporiasis are reviewed, with a focus on diagnostic assays currently being used for clinical and environmental samples. Challenges and limitations in working with Cyclospora are also discussed.

Update on Cyclospora cayetanensis, a Food-Borne and Waterborne Parasite

https://www.cell.com/trends/parasitology/pdf/S1471-4922(13)00019-6.pdf

Acanthamoeba keratitis: an emerging disease gathering importance worldwide?

Giardia lamblia, the cause of human giardiasis, is among the most common intestinal protozoa worldwide. Human infection may range from asymptomatic shedding of giardial cysts to symptomatic giardiasis, being responsible for abdominal cramps, nausea, acute or chronic diarrhoea, with malabsorption and failure of children to thrive. At present, treatment options include the nitroimidazoles derivatives; especially metronidazole, which has been the mainstay of treatment for decades and is still widely used. The increasing number of reports of refractory cases with this group of drugs and other antigiardial agents, has raised concern and led to a search for other compounds, some of which have arisen due to the introduction of drugs initially addressed to other diseases. The present article examines some of the most important points of antigiardial pharmacotherapy available at present and the future prospects of development of new agents.

Giardiasis: a pharmacotherapy review

This study was designed to evaluate ImmunoCard STAT Cryptosporidium/Giardia rapid assay and ELISA copro-antigen assays in detecting Giardia lamblia and Cryptosporidium species in fecal samples in comparison to microscopy. Both ImmunoCard STAT and ELISA assays were evaluated with 90 stool specimens that were tested by the standard ova and parasite examination including staining with both iron hematoxylin stain and modified Ziehl Neelson stains. Counting the number of Giardia cysts and Cryptosporidia oocysts in the positive stool samples was done in order to quantify the lower limit of parasite number that was able to be detected by all included assays. Both ImmunoCard STAT and ELISA assays were compared on the basis of the attributes which are number of detected cases, sensitivity, specificity, time required for the procedure and screening, ease of performance and interpretation, and cost. Microscopic examination revealed that 13.3 % of the samples were positive for Giardia and 2.2 % for Cryptosporidium. By ELISA, 16.7 % of the samples were infected with Giardia and 3.3 % with Cryptosporidium, while by ImmunoCard STAT, 17.8 and 4.45 % of the samples were positive for Giardia and Cryptosporidium, respectively. There is no statistically significant difference between the results of ELISA and ImmunoCard STAT assays. The lowest concentration detected in the stool samples was 10.50 ± 1.05 Giardia cysts and 2.83 ± 1.72 Cryptosporidium oocysts. The ImmunoCard STAT was extremely easy to read, thus requiring much less time, but its cost was much higher than ELISA. We concluded that although the overall ranking of both assays was high, the ImmunoCard STAT rapid assay was a more desirable test despite its higher cost.

Evaluation of ImmunoCard STAT test and ELISA versus light microscopy in diagnosis of giardiasis and cryptosporidiosis

Ivermectin, a broad spectrum antiparasitic agent has become a promising drug for treating parasitic infection and infestation. This study was carried out to investigate its activity against two common protozoal infection, giardiasis and cryptsporidiosis in a rat model. The results of this study showed that ivermectin therapy is effective against both parasites at a dose of 200 micrograms/kg.

Effect of ivermectin on combined intestinal protozoal infection (giardiasis and cryptosporidiosis)

Samples from different water sources of Alexandria, and from nasal passages of 500 healthy children inhabiting areas nearby these sources were examined for the presence of free-living amoebae. These samples were cultured on 1.5% non nutrient agar streaked with bacteria. Amoebae were isolated and identified by means of their morphological characters and ability to produce flagellated forms. Characteristics of the cystic stages and pattern of excystation also aided in the identification of the various species. Nine species, Naegleria gruberi, N. fowleri, Acanthamoeba rhysodes, A. glebae, A. culbertsoni, A. astronyxis, A. palestinensis, V. avara and V. inornata were isolated from the water of canals and drains. N. gruberi and A. rhysodes were found in the nasal passages of six healthy children living near the contaminated canals. No amoebae were encountered in the drinking water, swimming pools, sea and lake water included in this study.

Isolation and identification of free-living amoebae from some water sources in Alexandria.

Hydatid antigen was demonstrated for the first time in urine of patients with hydatidosis by coagglutination test (Co-A). Urinary antigen was detected in all Co-A positive serum corresponding samples of surgically confirmed hydatid disease. The sensitivity and specificity were 100% in urine compared with the corresponding serum samples. These results clarified that the use of Co-A test for detection of hydatid antigen in urine is an easy, simple, rapid, non-invasive and efficient method for diagnosis of hydatidosis.

Urinary antigen detection for diagnosis of hydatid disease.

Swiss albino mice get Cyclospora infection after orally inoculated with sporulated oocysts. Two weeks post inoculation, most of them passed numerous acid fast immature oocysts in their stools. One week later, light microscopic examination of their intestinal H & E stained sections revealed parasitic stages in a supranuclear location within enterocytes. They were most prominent in the mucosal villi. Lamina propria was expanded by an inflammatory infiltrate. The combined parasitological and histopathological present studies helped in distinguishing Cyclospora which is often confused with Cryptosporidia in stool samples and with Isospora in intestinal sections. Electron microscopy demonstrated both sexual and asexual developmental stages of Cyclospora in ultrathin infected sections. Therefore, Cyclospora species require only a single host to complete its entire life cycle

H A Sadaka

Papers

Evaluation of ImmunoCard STAT test and ELISA versus light microscopy in diagnosis of giardiasis and cryptosporidiosis

Effect of ivermectin on combined intestinal protozoal infection (giardiasis and cryptosporidiosis)

Isolation and identification of free-living amoebae from some water sources in Alexandria.

Urinary antigen detection for diagnosis of hydatid disease.

Experimental studies on cyclosporiosis.