[Grey rats as hosts of intestinal pathogenic parasites].
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Total serum IgE level was determined by the radioactive single radial diffusion technique in blood donors, nurse-aid students with the stool positive and negative for parasites, and in patients with helminthic infections. A geometric mean of 445.1 IU/ml in the sera from blood donors was found. Patients with helminthic infections had significantly higher levels than the blood donors and the nurse-aid students with the stool negative for parasites. Intestinal protozoal infections did not cause an increase in IgE level.
Intestinal parasites continue to be a significant health problem in both developed and developing countries. In developed countries, protozoans are more commonly the cause of gastrointestinal infections than are helminths. Some protozoan parasites have stages in which, in addition to being resistant to chemicals used for water treatment, they are small enough to pass through commonly used filtration processes. The relatively large size of helminth eggs increases the likelihood of their removal during water filtration. The direct impact of protozoan parasites on both human and animal health is considerable, and there is some evidence that infection may contribute to the development of various forms of intestinal dysregulation as well as disseminated infection, especially in AIDS patients. Protozoans of special interest, due to either their frequency of isolation or their role as emerging pathogens, include Giardia duodenalis, Cryptosporidium parvum, Cyclospora cayetanensis, and the microsporidians, Enterocytozoon bieneusi and Encephalitozoon intestinalis.
During a study of intestinal parasitic infections in human immunodeficiency virus-positive patients, a parasite belonging to the phylum Myxozoa, recently described from human samples, was identified in one sample. When this parasite was stained by the modified Ziehl-Neelsen staining method, the features of the spores were identified: they were pyriform in shape, had thick walls, and had one suture and two polar capsules, with each one having four or five coils. The suture and two polar capsules were observed with the chromotrope-modified stain. The number of stools passed was more than 30 per day, but oocysts of Isospora belli were also found. Upon reexamination of some formalin- or merthiolate-iodine-formaldehyde-preserved samples an identical parasite was found in another sample from a patient presenting with diarrhea. Strongyloides stercoralis larvae and eggs of Hymenolepis nana and Ascaris lumbricoides were also found in this sample. Given that both patients were also infected with other pathogens that cause diarrhea, the possible pathogenic role of this parasite could not be established. The probable route of infection also could not be established.
The following intestinal parasites: Dipylidium caninum, Taenia hydatigena, Trichocephalus vulpis, Ancylostoma caninum, Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, Ascaris sp. have been found on the basis of coprological investigations of 120 dogs from the Wrocłow shelter, 20 dogs from Wrocłow flats and 20 dogs from rural area of Kielce district. Total extensity of infection of rural dogs was 100% and 40-48% in town. These differences, according to the authors, are connected with different breeding conditions as well as with the specific contacts of investigated animals with others in various environments in Poland.
Fascioliasis and other food-borne trematodiases are included in the list of important helminthiases with a great impact on human development. Six plant-borne trematode species have been found to affect humans: Fasciola hepatica, Fasciola gigantica and Fasciolopsis buski (Fasciolidae), Gastrodiscoides hominis (Gastrodiscidae), Watsonius watsoni and Fischoederius elongatus (Paramphistomidae). Whereas F. hepatica and F. gigantica are hepatic, the other four species are intestinal parasites. The fasciolids and the gastrodiscid cause important zoonoses distributed throughout many countries, while W. watsoni and F. elongatus have been only accidentally detected in humans. Present climate and global changes appear to increasingly affect snail-borne helminthiases, which are strongly dependent on environmental factors. Fascioliasis is a good example of an emerging/re-emerging parasitic disease in many countries as a consequence of many phenomena related to environmental changes as well as man-made modifications. The ability of F. hepatica to spread is related to its capacity to colonise and adapt to new hosts and environments, even at the extreme inhospitality of very high altitude. Moreover, the spread of F. hepatica from its original European range to other continents is related to the geographic expansion of its original European lymnaeid intermediate host species Galba truncatula, the American species Pseudosuccinea columella, and its adaptation to other lymnaeid species authochthonous in the newly colonised areas. Although fasciolopsiasis and gastrodiscoidiasis can be controlled along with other food-borne parasitoses, fasciolopsiasis still remains a public health problem in many endemic areas despite sustained WHO control programmes. Fasciolopsiasis has become a re-emerging infection in recent years and gastrodiscoidiasis, initially supposed to be restricted to Asian countries, is now being reported in African countries.
The spectrum of intestinal parasites present in the Swiss Webster, C57B1/6 and DBA/2 mice strains from different animal houses was identified and prevalences compared. Three parasites were observed during the course of this study, namely the cestode Vampirolepis nana (Siebold, 1852) Spasskii, 1954 (= Hymenolepis nana) and the nematodes Aspiculuris tetraptera (Nitzsch, 1821) Schultz, 1924 and Syphacia obvelata (Rudolphi, 1802) Seurat, 1916. The scope of this investigation has been widened to also include morphometric data on the parasites, to further simplify their identification, since the presence of helminths in laboratory animals is regarded as a restricting factor for the proper attainment of experimental protocols.
Intestinal parasites were investigated in 396 diarrheal stool samples collected from individuals aged 1 to 68 years (males: 239 and females: 157) in Nepal. Samples were collected at different medical centers located in Kathmandu and from two public schools in a village setting in Kathmandu Valley and outside, during October 1999 to January 2001. The stool samples were mixed with 2% dichromate solution and transported to Japan for investigations. Parasites were detected by employing the formal-ether sedimentation technique. Of a total of 396 fecal samples investigated, 193 (49%) were positive for some kind of parasite. Altogether, 15 species of parasites were detected. Giardia intestinalis topped the list of protozoa, whereas Trichuris trichiura was the most frequently detected among helminth parasites. Of the 193 positive samples, 109 (56%) had single parasite infections, whereas 84 (43%) had multiple infections with a maximum of five species. Of the total positive, 45 (23%) had both protozoa and helminths whereas 37 (19%) had only protozoa. Females (52%) and children (15 years and under) (52%) had a marginally higher prevalence compared with males (46%) and adults (45%), respectively (p > 0.05). Samples collected from two public schools in a village setting inside Kathmandu Valley and outside had a significantly higher positive rate compared with those observed in individuals visiting different medical centers in the city and suburban areas in Kathmandu (p < 0.05).
A survey for blood and intestinal parasites was carried out in the Banggai Kabupaten Central Sulawesi, Indonesia. A total of 336, stool specimens were obtained from 182 males and 154 females ranging in age from 2 to 90 years. Hookworm, Trichuris trichiura and Ascaris lumbricoides were the most common helminths encountered. Schistosoma japonicum was noticeably absent in the population sampled. The following intestingl protozoa were detected: Entamoeba coli, E.histolytica, Iodamoeba bütschlii, Giardia lamblia, Chilomostix mesnili and Endolimax nana. A total of 650 blood smears were examined and both Plasmodium falciparum and P. vivax were found in 5 % of the populations sampled. In addition, Brugia malayi microfilariae were detected in 3% of the blood smears examined.
Mice exposed to primary infections with the parasite intestinal nematode Nematospiroides dubius failed to show the mucosal mast cell (MMC) response which is characteristic of infections with other species of intestinal nematode and which was readily induced in these mice by infections with Nippostrongylus brasiliensis or Trichinella spiralis. The failure to generate a mucosal mastocytosis was independent of host strain or sex. When infections with N. dubius were established before, or concurrently with, T. spiralis or N. brasiliensis, the MMC response elicited by these species was delayed and/or depressed as was expulsion of the worms themselves. Infection with N. dubius given when a MMC response was already established, by exposure to T. spiralis, had no effect on MMC numbers. The possibility that the effects of N. dubius upon MMC responses reflect a lack of mastocytopoietic potential, rather than an active interference, was excluded by showing that SJL mice, which expel primary infections with N. dubius and express strong immunity to reinfection, developed marked mastocytosis during secondary infections. The depression of MMC responses by N. dubius is discussed in relation to the known immunosuppressive properties of this parasite and in relation to the T cell mediated control of MMC development.
Because of the tremendous impact that parasitic infections have on the health and productivity of humans and domestic animals, considerable research effort has been focused upon understanding the mechanisms of host-parasite coexistence, host resistance and immunopathology. Studies have employed a range of approaches including: kinetic analysis of parasite establishment, development, fecundity and survival in naive and previously-infected hosts; correlation between parasite survival and histopathologic responses at the site of infection; vaccination with attenuated parasites or their products; cellular and serum transfer of immunity to naive or immunocompromised hosts; pharmacologic manipulation of potential mediators of host defense using agonistic and antagonistic drugs. However, it is becoming increasingly clear that to understand the mechanisms associated with host resistance and parasite survival, one must define the characteristics of the local microenvironment at the host-parasite interface. One of the approaches by which such studies can be made involves the isolation and characterization of cells derived from the local infection site. This manuscript reviews some of these studies on local aspects of mucosal immune responses in parasitic infections. Examples that will be discussed include IgA antibody, intraepithelial leukocytes from the intestine, intestinal mast cell populations, macrophages derived from bronchoalveolar lavage, and local immunoregulatory responses during respiratory and intestinal parasitic infection. These studies have established unequivocally that local responses to mucosal parasitic infection can only be appropriately investigated using cells derived from the specific microenvironment. This conclusion should encourage others to further study these local responses and to be innovative in investigating unexplored aspects of the host-parasite interface.
Treatment of Strongyloides stercoralis infection was investigated in 2 dogs with naturally acquired, chronic-active infections, and in 3 dogs with corticosteroid-enhanced, experimentally induced hyperinfections. A single oral dose of ivermectin was given to naturally infected (200 micrograms/kg of body weight) and experimentally infected (800 micrograms/kg) dogs. Five dogs with experimental hyperinfections served as controls. Dogs with naturally acquired infections ceased to shed first-stage larvae in the feces 1 week after treatment, but 1 dog had recrudescence and required a second dose. Ivermectin was 100% effective in removing adult S stercoralis from the intestinal tract of the experimentally infected dogs, but it was not effective in removing third-stage larvae from parenteral sites. Ivermectin-treated dogs had few intestinal parasites of any stage, whereas at necropsy, 4 of 5 experimentally infected dogs not treated had massive infections (greater than 100,000 adults, greater than 92,000 larvae) in the intestinal tract, and 3 of 5 had larvae (greater than 2,500) in parenteral sites.
The intestinal nematode parasite, Nippostrongylus brasiliensis, triggers potent type 2 immunity. Using OVA peptide as a model Ag, we have examined the adjuvant effects of this parasite on the in vivo development of Ag-specific Th2 cells from naive DO11.10 T cells. Our findings show that Th2 cells can develop from transferred naive OVA-specific DO11.10 T cells in recipient IL-4-/- mice inoculated with N. brasiliensis plus OVA. However, autocrine IL-4 is required for in situ Th2 cell differentiation since transferred IL-4Ralpha-deficient DO11.10 T cells showed greatly reduced Th2 cell development in inoculated IL-4-/- recipient mice. Surprisingly, we also found that IL-2 blockade promoted B7-dependent T cell cycling, but inhibited the development of OVA-specific Th2 cells. Furthermore, the effects of IL-2 occurred independently of CD25+ T regulatory cells. These studies establish a previously unrecognized requirement for autocrine IL-4 and IL-2 in Th2 responses elicited by nematode parasites.
Blood counts of healthy juvenile and adult llamas (Lama glama) and guanacoes (L guanacoe) showed that guanacoes have higher red cell counts, haemoglobin values and packed cell volumes than llamas. In both species, the numbers of lymphocytes and platelets were higher in juveniles than in adults. By reference to the values found in normal animals, abnormal haematological variations were detected in a number of sick individuals. Neutrophilia, hyperfibrinogenaemia and a tendency to develop regenerative hypochromic anaemia were observed in animals with acute and chronic inflammatory diseases and hypochromic macrocytic anaemia occurred in animals with parasitic infections. Many individuals in which subclinical intestinal parasitic infections were suspected had relatively high eosinophil counts although their other haematological values were normal.
Expulsion of the gastrointestinal nematode Trichinella spiralis is associated with pronounced mastocytosis mediated by a Th2-type response involving IL-4, IL-10, and IL-13. Here we demonstrate that IL-18 is a key negative regulator of protective immune responses against T. spiralis in vivo. IL-18 knockout mice are highly resistant to T. spiralis infection, expel the worms rapidly and subsequently develop low levels of encysted muscle larvae. The increased speed of expulsion is correlated with high numbers of mucosal mast cells and an increase in IL-13 and IL-10 secretion. When normal mice were treated with rIL-18 in vivo, worm expulsion was notably delayed, and the development of mastocytosis and Th2 cytokine production was significantly reduced. The treatment had no effect on intestinal eosinophilia or goblet cell hyperplasia but specifically inhibited the development of mastocytosis. Addition of rIL-18 to in vitro cultures of bone marrow-derived mast cells resulted in a significant reduction in cell yields as well as in the number of IL-4-secreting mast cells. In vivo treatment of T. spiralis-infected IFN-gamma knockout mice with rIL-18 demonstrated that the inhibitory effect of IL-18 on mastocytosis and Th2 cytokine secretion is independent of IFN-gamma. Hence, IL-18 plays a significant biological role as a negative regulator of intestinal mast cell responses and may promote the survival of intestinal parasites in vivo.
A survey of blood and intestinal parasites in a coastal and a mountainous area of the remote island of Alor, southeastern Indonesia revealed widespread infection with pathogenic intestinal protozoa and helminths, malaria and filaria. Amoebiasis (31.2%), ascariasis (35.3%) and hookworm infections (28.6%) were common, reflecting primitive sanitation and hygiene. Trichuriasis rates (6.8%) were less than expected perhaps due to the prolonged dry season and soil factors in the area. Timor filariasis was found in coastal villagers (10.5%), but not in persons living at an elevation of 500 meters; a low rate of bancroftian filariasis (1.8%) was found in both areas. Malaria, caused by P. vivax, P. falciparum and P. malariae was mesoendemic. Soil-transmitted and vector-borne parasitic infections are an important health problem in the populations examined.
OBJECTIVE: To report on the importance of intestinal parasites in patients with AIDS, showing relevant data in the medical literature, with special emphasis on epidemiology, diagnosis and treatment of enteroparasitosis, especially cryptosporidiosis, isosporiasis, microsporidiasis and strongyloidiasis. DESIGN: Narrative review.