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PubMed1996

[Physiopathology of protozoan infections].

The pathophysiology of diseases produced by protozoal infections is caused not only by a direct effect of the parasites on their host (e.g. host cell lysis or parasite adherence), but also by indirect effects, where molecules of parasite origin exert an effect on host cells, which in turn produces a cascade of events (including the secretion of inflammatory cytokines, prostaglandins and nitric oxide) responsible for the symptomatology observed. The role of the host itself in the pathogenic events is not negligeable and its genetic background, nutritional and immunological status will influence the outcome of the infection (which will result in asymptomatic infections in some individuals and severe disease in others). The general and specific features of a variety of protozoal infections of medical and veterinary importance (including malaria, babesiosis, trypanosomiasis, toxoplasmosis, cryptosporidiosis, amoebiasis, giardiasis and trichomoniasis) are discussed in this review and a number of common patterns are identified.

Animals↗
PubMedDate not supplied

[Radioimmunologic dosage of total IgE serum in various helminthiases and protozoan infections (author's transl)].

The both purposes of our investigation were to determine initially the level of total serum IgE in various parasitic infections and the variations of this level after the initiation of specific treatment. In the study, III sera from black race patients with a clinical and biological diagnosis of helmintic or protozoal infections and without allergic diseases were tested by the commercially available "Radioimmunosorbent test" (Pharmacia Laboratories). In helmintic infections: the IgE concentration was higher than normal level: --in 100% of patients infested with ankylostoma, trichocephalus (mean concentration m: 2,961 UI/ml) or schistosoma (m: 1,578 UI/ml); --in 70% of patients infested with ascaris (m: 1,110 UI/ml). In protozoal infections: the abnormal IGE level was found only in 44% and 14% of cases respectively of malaria (m = 704 UI/ml) and of leishmaniasis (441 UI/ml). The time course of total serum IgE determined after the treatment initiation showed that: a) in patients with intracellular helminthiasis and protozoal infections serum IgE concentrations were gradually increased in a statistically highly significant way; b) in cases with intestinal helminthiasis, high levels disappeared ane returned rapidly to normal values.

Adolescent↗
PubMed1982

Macrophage induction of T-suppressor cells in pesticide-exposed and protozoan-infected mice.

The use of infectious pathogens has allowed the detection of the development of synergism between pathogens and ubiquitous environmental chemical contaminants. This synergism has been demonstrated to result in a state of immunosuppression which either did not occur in the independent and singular presence of the chemical or pathogen and/or was greater than additive when both were combined. The immunosuppression was distinct with regard to the organochloride used and, therefore, is not a ubiquitous characteristic of all organohalides. The production of a macrophage soluble factor which appeared to induce T-suppressor cells was demonstrated in hepatic Kupffer cells from mice administered 5 ppm of dieldrin for 10 weeks and then infected with Leishmania tropical promastigotes. The factor was not generated in mice administered dieldrin and infected with malaria nor in mice administered only dieldrin nor in mice only infected with Leishmania. Additional studies revealed a profound impairment in macrophage antigen processing with macrophages obtained from mice administered dieldrin. The use of pathogen models may allow the immunosuppressive potential of environmental chemical contaminants to be expressed in a more sensitive manner.

Animals↗
PubMed1992

Intestinal protozoan infections in Malaysia.

Intestinal protozoa are found in all communities in Malaysia and among all ethnic groups. Prevalence of intestinal protozoa is not affected by ethnicity but by living conditions. Communities with both basic amenities of safe water supply and proper toilets have lower prevalence than those with one or none of the amenity. Cryptosporidium is an important intestinal protozoon in Malaysia and should be included in future field and laboratory studies and also in laboratory diagnosis for pathogens. Much interest will be centered on Blastocystis hominis in future studies in view that it may be a cause of diarrhea.

Adolescent↗
PubMed1990

Therapy and prophylaxis of systemic protozoan infections.

This article summarises current therapy and prophylaxis for Pneumocystis carinii, Toxoplasma gondii, Leishmania species, African trypanosomes (Trypanosoma brucei gambiense and T. b. rhodesiense), and American trypanosome (Trypanosoma cruzi) infections. Each agent and the disease it causes is briefly reviewed, and current data on the structure, mode of action, indications for treatment, dosage, administration, duration of therapy, efficacy, toxicity, and necessary monitoring during therapy are discussed for each drug. Drugs considered include cotrimoxazole (trimethoprim + sulfamethoxazole), pentamidine, dapsone (diaphenylsulfone), trimetrexate, eflornithine (DFMO), and primaquine/clindamycin and pyrimethamine/sulphonamide combinations for Pneumocystis pneumonia; pyrimethamine/sulfadiazine, spiramycin, and clindamycin for toxoplasmosis; pentavalent antimonials ('Pentostam' and 'Glucantime'), pentamidine, amphotericin B, allopurinol, ketoconazole, and itraconazole for leishmaniasis; suramin, pentamidine, melarsoprol, tryparsamide, Mel W, berenil, and eflornithine (DFMO) for African trypanosomiasis; and nifurtimox, benznidazole and gentian violet for American trypanosomiasis.

Chagas Disease↗
PubMed1989

Implications of genetic exchange in the study of protozoan infections.

Genetic exchange is now known to occur during the life-cycle of many parasitic protozoa, including malaria parasites, coccidia and trypanosomes. The process is studied by making deliberate crosses between cloned organisms differing in clearly defined markers. In malaria parasites, crosses have been made between parasites differing in characters such as isoenzymes, antigens and other proteins, drug sensitivity, and chromosome and other DNA polymorphisms. Crosses are made by transmitting a mixture of gametes of each clone through mosquitoes to allow cross-fertilization to take place, and examining the resulting progeny by cloning for organisms exhibiting non-parental combinations of characters. The inheritance of many characters, such as antigen and protein variants, is in accordance with Mendelian expectations for a haploid organism. Recombination occurs at a higher than expected frequency. Studies on chromosomes have show that crossing-over events commonly occur following meiosis of hybrid zygotes. Repetitive DNA and subtelomeric regions of chromosomes appear to be particularly susceptible to such recombination events. In trypanosomes, crosses between clones of Trypanosoma brucei have shown that hybrids are formed during tsetse fly transmission. The organism appears to be mainly diploid, but some characters including certain chromosomes seem to be inherited in a non-Mendelian manner.

Animals↗
PubMedDate not supplied

Protozoan infections (Toxoplasma gondii, Neospora caninum and Sarcocystis spp.) in sheep and goats: recent advances.

The protozoan parasite Toxoplasma gondii is a serious cause of fetal mortality in sheep and goats. Oocysts, the parasite stage responsible for initiating infection, are produced following a primary infection in cats. A primary infection in pregnant sheep and goats can establish a placental and fetal infection which may result in fetal death and resorption, abortion or stillbirth. Diagnosis is aided by the clinical picture, the presence of characteristic small white necrotic foci in placental cotyledons, the possible presence of a mummified fetus and on fetal serology and histopathology. Development of the polymerase chain reaction (PCR) specific for T. gondii may also provide a valuable diagnostic tool. Measures to control abortion include improved management of farm cats, fodder and water. Vaccination of sheep with the live vaccine is an effective preventive measure and the use of decoquinate in feed may be useful in some situations. Neospora caninum is related to T. gondii and while its asexual life cycle is similar to that of the latter it is currently not known whether it has a similar sexual life cycle in a definitive host. Neospora is an important cause of fetal loss in cattle and parallels that of T. gondii infection in sheep and goats. While it does not appear to cause frequent losses in these latter animals, experimental infection is readily induced in them and if initiated during pregnancy provides a very good model of the bovine infection. Furthermore clinical signs and pathological lesions in sheep and goats are similar to those induced in them by T. gondii, although there are subtle histopathological differences. These changes will aid possible diagnosis as will specific serological tests such as the indirect immunofluorescent antibody test and the enzyme linked immunosorbent assay and the PCR. Sarcocystis, which exists as numerous species, undergoes a coccidian-like life cycle with each having a distinctive definitive (usually carnivore) host which excretes sporocysts into the environment. Clinical sarcocystiosis is much less commonly diagnosed than toxoplasmosis and neither is it normally associated with fetal infection or abortion in either sheep or goats. However, infection is extremely common throughout the world and follows ingestion of food or water contaminated with sporocysts. Clinical signs, when seen, include fever, anaemia, inappetance and weight loss or reduced weight gain. Central nervous signs (hind limb weakness, ataxia, paresis), acute myopathy and death may occur. Diagnosis is difficult as infection is so common and clinical signs absent, mild or non-specific. Serology may be useful in some situations and histopathology/immunohistochemistry is valuable for confirming the cause of death. Control relies on preventing contamination of pasture and water with faeces of dogs, foxes and cats or by controlling access of young susceptible stock to contaminated land. Relatively little is known of the immunity induced by infection with Sarcocystis spp. but research indicates that protective immunity does develop and that cell-mediated mechanisms are probably important. It is likely that sarcocystiosis is underdiagnosed as a problem and that better diagnostic methods are needed to show the true extent of the losses caused. Neosporosis on the other hand would appear not to be so common in sheep and goats. The value of experimental infections in these animals may be to provide a comparative model of the infection in cattle in the same way that our understanding of toxoplasmosis in sheep provides a superior model of human toxoplasmosis.

Animals↗
PubMed1983

Intestinal protozoan infection in a semicommunal group.

A survey was conducted to determine the prevalence of protozoan parasites in a large semicommunal group in Los Angeles. Protozoan parasites were observed in 151 (69%) of the 220 group members in the study. Parasites were observed in stool specimens from 105 (76%) of the 138 children and 46 (56%) of the 82 adults. Dientamoeba fragilis was observed in 115 (52%), Giardia lamblia in 50 (23%), Entamoeba histolytica in 9 (4%), and commensals in 61 (28%). Parasitic infection was infrequent in infants less than 1 year old, was demonstrated in 33 (89%) of the 2- to 4-year-olds, 69 (78%) of the 89 school age children 8-15 years of age, and in 46 (56%) of the 82 adults. G. lamblia was most prevalent in children younger than 6 years; whereas D. fragilis was common in all age groups. The fecal-oral route was the most likely means for parasite transmission. Since the group at times serves meals to the public, spread of parasites outside the community is a potential public health problems. Diagnosis of parasitic infection is dependent on optimal stool collection, proper laboratory techniques and trained personnel.

Adolescent↗
PubMed2006

Epidemiology of parasitic protozoan infections in Soay sheep (Ovis aries L.) on St Kilda.

The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

Age Factors↗
PubMed1996

[Protozoan infections and intestinal helminthiasis among the population of a village in the northern Sudan savannah area of Mali (West Africa)].

A cross sectional survey was carried out on intestinal parasites in a rural village located in a Sudan savannah area of Mali in September 1994. This survey was aimed to describe the prevalence of intestinal protozoa and helminths, and to evaluate the possible epidemiological impact of some sociobehavioural factors. A total of 209 stool specimens were examined with 3 methods: fresh stool examination, Kato thick smear technique and a formalin-ether concentration technique in a closed system. Cryptosporidium was also searched following the Ziehl-Neelsen staining and the immunofluorescence method using monoclonal antibody. Microsporidia were investigated by Trichrome staining technique. The concentration technique, as expected, was the more sensitive method: the protozoan cyst rate and the helminth egg rate were 70.3% and 11%, respectively. The low prevalence of intestinal nematodes, unexpected for this area, could be attributed to the improvement in sanitation (traditional WC present in 73.9% of the families), but also to the repeated treatments of the population against onchocercosis with ivermectin since 1992. We found no cases of isosporosis, cryptosporidiosis and microsporidiosis in our study population, neither significant association between socio-behavioural factors and parasitic infections.

Cross-Sectional Studies↗