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PubMed2002

Insights into fish host-parasite trophic relationships revealed by stable isotope analysis.

Trophic relationships between 10 species of fish host and their associated nematode, cestode, and copepod parasites were investigated using stable isotopes of carbon and nitrogen. Nematodes and cestodes were consistently depleted in 15N with respect to their host, and such fractionation patterns are unlike those conventionally observed between consumers and their diets. Species of copepod parasite were sometimes depleted and sometimes enriched in 15N with respect to fish hosts, and this confirms earlier reports that the nature and magnitude of ectoparasite-host fractionations can vary. Significant differences in delta15N and delta13C were observed among fish tissues, and the isotopic signature of parasites did not always closely correspond to that of the tissue with which the parasite was found most closely associated, or on which the parasite was thought to be feeding. Several possible explanations are considered for such discrepancies, including selective feeding on specific amino acids or lipids, migration of the parasite among different fish tissues, changes in the metabolism of the parasite associated with life history and migration between different host animals.

Animals↗
PubMed2004

Parasitism in species of Bathymodiolus (Bivalvia: Mytilidae) mussels from deep-sea seep and hydrothermal vents.

Bivalve species, especially mussels, are biomass dominants in many deep-sea chemosynthetic ecosystems. As in shallow-water environments, parasites are likely to be important factors in the population dynamics of bivalve communities in chemosynthetic ecosystems, but there has been little study of parasitism in deep-sea seep or vent molluscs. In this study, parasite types, diversity, prevalence, infection density and non-infectious indicators of stress or disease as related to host age, reproductive condition, and endosymbiont density were assessed in mussels (Bathymodiolus heckerae) from 2 seep sites and mussels (B. puteoserpentis) from 2 vent sites. We identified 10 microbial or parasitic agents in histological sections. Parasite types included 3 viral-like gut inclusions, 2 rickettsia-like gill inclusions, a rickettsia-like mantle inclusion, a bacterial gill-rosette, a chlamydia-like gut inclusion, gill-dwelling ciliates, and an unidentified inclusion in gut tissues. Parasite species richness was greater in seep mussels than in vent mussels, with the seep mussels possessing 9 types of parasites compared to 2 in the vent mussels. One of the viral-like inclusions infecting the seep mussel B. heckerae was pathogenic, causing lysis of the digestive tubules. The prevalence and intensity of infection by this pathogen were greater in hosts with shell lengths less than 100 mm. Mussels from all 4 sites also exhibited intense infiltration of tissues and blood spaces by enlarged hemocytes. Hemocytic infiltration (hemocytosis) showed variable degrees of severity that were not associated with other host factors examined.

Age Factors↗
PubMed1981

Intestinal parasites in Indochinese immigrants.

Fifty-two percent of 419 recent Indochinese refugees, most of whom were studied because they had symptoms, signs, or hematologic findings suggestive of parasitism, had intestinal parasites. The frequency of parasitism was comparable in Vietnamese vs. other Indochinese (Cambodians and Laotians), but other Indochinese were more often found to have multiple parasites. The most common parasite in Vietnamese was Ascaris lumbricoides, hookworm was the most common parasite in Cambodians and Laotians, and opisthorchid flukes were only found in Laotians. Age and sex were not related to infection except for Giardia, which has more prevalent in children. Based on public or personal health hazards and treatability, 33% of patients had parasites judged to warrant therapy, even in a clinically normal host.

Ambulatory Care Facilities↗
PubMed2006

Oral fecal parasites and personal hygiene of food handlers in Abeokuta, Nigeria.

BACKGROUND: Ingestion of infective eggs and cysts of faecal orally transmissible parasites has been linked with the level of environmental and personal hygiene. The possibility of contamination of food with eggs and cysts by infected food vendors has also been recorded. OBJECTIVES AND METHODS: This study was aimed at assessing the prevalence of parasites with direct transmission and the level of hygiene among food vendors. Stools of randomly selected food vendors selling in schools and streets in Abeokuta were examined for ova and cysts of parasites using formo-ether concentration method. Questionnaires, interviews, and field observation were also used to assess the activities of food vendors. RESULTS: Ninety-seven (97%) percent of the food vendors were infected with one or more faecal-orally transmissible parasites while 3% were free from such parasites; Parasites observed were Entamoeba histolytica with a prevalence of 72% Ascaris lumbricoides (54%), Enterobius vermicularis (27%), Trichuris trichiura (24%) and Giardia duodenalis (13%). School food vendors recorded lower prevalence of infection (92%) than the street food vendors (98.7%) (P>0.05) Fifty-two percent (52%) of the food vendors have dewormed in the last four years; Eighty percent (80%) of this were school food vendors. Infections with helminthes were recorded in 63.5% of the dewormed food vendors. Food vendors involved in child care activities were found to be more infected than those not involved in such activities. Toilet facilities available to the vendors were mainly pit latrine and other related structure (75%) while 25% had access to water system closets. During hawking, dung hills were majorly used for defaecation. Hand washing after defaecation did not include the use of soap in the few vendors that were involved in hand washing. CONCLUSION: There is need to enact food handling policies and implementation of such policies ensured in order to reduce transmission of oral faecal parasites.

Adolescent↗
PubMed1998

[Intestinal parasitic diseases in an urban environment in Sahel. A study in a district of Niamey, Niger].

Health and environment in Niamey, a capital in Sahel, are particularly linked owing to population growth, promiscuity and large pollution induced by human and animal excreta. One district, located in the centre of the town, was surveyed for drinking water quality (ammoniac and bacterial count) and use, as well as for the prevalence of parasites through both a random sample (fixed tools with methiolate-iodine-formaldehyde) and a systematic one (scotch-test). Water consumption was 16.5 litres/day/man from fresh water supplies (87%) and private wells (13%). Ammoniac measures were low in the wells but high in running water (pool and river). It was the same for faecal coliform bacteria. These results give evidence of biotope faecal pollution. The random sample (322 persons, male/female sex ratio 0,85, average age 20,6 years) showed a 42.1% parasitic prevalence. Amoeba was the most frequent parasite (53.6%); and Giardia (14.9%) was the most frequent pathogenic parasite. In the second sample (161 children under 10 years), 24.2% were carriers of oxyuris. This large intestinal parasitism, without any change in connection with previous data in Niger, points to an important fecal contamination of the people more by the way of "dirty hands" than consumption of drinking water. The parasites observed have a short biological cycle, not necessitating long-term maturation in the environment. Those whose ova or larvae must complete their cycle outside have no possibility of surviving in Sahel, thanks to the beneficial effect of sunlight (heat and ultraviolet light). The inhabitants of this district seem to have adapted to intestinal parasitism. But the occurrence of malnutrition linked to a new drought could lead rapidly to a very serious adverse result.

Adaptation, Physiological↗
PubMed2002

Resistance to cadmium and parasite infection are inversely related in two strains of a freshwater gastropod.

Phenotypes that are either resistant or susceptible to infection by the trematode parasite Schistosoma mansoni exist in the tropical freshwater snail Biomphalaria glabrata. We tested the hypothesis that a cost of parasite resistance in B. glabrata is greater sensitivity to cadmium toxicity, using parasite-resistant and parasite-susceptible strains exposed to cadmium in the laboratory. Survival analysis showed that time to death for cadmium was significantly shorter in eggs, juveniles, and adults of the parasite-resistant BS90 strain in comparison with the parasite-susceptible NMRI strain. Cadmium exposure increased time to hatch in both strains, but the effect was greater in BS90. Percentage hatch decreased with increased cadmium; BS90 was again more sensitive than NMRI. Comparison of the median effective concentration (EC50) for hatching and median lethal concentrations (LC50s) for survival of juveniles and adults showed that the order for cadmium resistance was adults > juveniles > eggs in NMRI and adults > eggs > juveniles in BS90. Cadmium resistance of F1 and F2 progeny of BS90/NMRI crosses was intermediate to that of parental strains. Numerical estimates indicated that a single genetic factor was responsible for the difference in cadmium resistance in the two strains. These findings were consistent with the hypothesis that greater sensitivity to cadmium is a cost of resisting parasitic infection.

Animals↗
PubMed2002

A comparative study of the intestinal parasites prevalent among children living in rural and urban settings in and around Chennai.

A comparative analysis of the various intestinal parasites detected among children attending schools was carried out in a rural and urban location in and around Chennai. A total of 324 stool samples were examined by routine microscopy using normal saline and Lugol's iodine preparation as well as by saturated sodium chloride flotation technique. All suspicious samples were subjected to zinc sulphate concentration technique as well as modified Ziehl Neelson stain and Trichrome stains to identify the other uncommon intestinal parasites. Out of 125 specimens tested from the rural location, the overall prevalence of intestinal parasites was 91%. Ascaris lumbricoides was the most common helminthic parasite detected (52.8%) followed by Trichuris trichura (45.6%), Ancylostoma duodenale (37.6%), Strongyloides stercoralis (3.2%) and Hymenolepis nana (1.6%). Giardia lamblia was the most common protozoan parasite detected (16%), followed by Entamoeba histolytica (4%). In contrast under urban settings, out of the 199 stool specimens tested the positivity rate was 33%. Giardia was the most common parasite detected (22.6%) followed by Entamoeba histolytica (10.6%). All other intestinal parasites such as T. trichura (2.01%), H. nana (1.01%) and A. lumbricoides (0.50%) were found to have much lower prevalence in comparison to the rural area tested. Enterobius vermicularis (0.50%) was also detected. Ancylostoma duodenale and Strongyloides stercoralis were not encountered at all in the urban setting studied.

Adolescent↗
PubMed1992

[Parasitic diseases in patients with impaired immune response. Clinical picture and diagnosis].

Patients with impaired immune system are frequently infected with various parasitic diseases. The clinical picture is characterized by unusual manifestations and frequently severe recurrences of infections which are not normally serious. Some almost parasitic microorganisms produce symptoms exclusively in patients with impaired immune system. Parasitic infections have become increasingly common with the increasing number of patients who live for prolonged periods with impaired immune systems, often as a result of infection with HIV. Among the numerous parasitic infections which are observed in man, there are a few which occur particularly frequently in patients with impaired immune systems. This is a brief review of the clinical pictures and diagnostic options in parasitic disease in individuals with impaired immune system with particular emphasis on infections caused by: Pneumocystis carinii, Toxoplasma gondii, Cryptosporidium ssp., Microspora, Entamoeba histolytica, Leishmania ssp., and Strongyloides stercoralis. In patients with impaired immunity, parasitic infections frequently cause nonspecific symptoms and, on account of the impaired immunity, antibodies to the parasite are not always produced. The diagnosis of these infections is, therefore, based on morphological demonstration of the microorganism concerned, culture, specific antigen or DNA defections.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Malaria parasite interactions with the human host.

The interaction between the malaria parasite and the human host involves a number of interactions that result in the parasite evading the human immune system. Since the stages of the malaria lifecycle are complex, this allows the use of various immune evasion strategies by the malaria parasite and has major implications in the development of a vaccine for malaria endemic areas. The present review highlights key host:parasite interactions. Plasmodia puts selection pressure on human gene frequencies, and studies into host genetic factors such as the Duffy blood group and sickle cell anaemia offer insight into the host- parasite relationship. In addition, parasite interactions with the different effector arms of the immune system can result in altered peptide ligand (APL) antagonism which alters the immune response from a pro- to an anti-inflammatory T cell response. Recent insights into the interaction between professional antigen presenting cells, dendritic cells (DCs), and malaria parasites is discussed in detail.

Animals↗
PubMedDate not supplied

[Investigation of intestinal parasites in AIDS patients].

In this study, enteric parasites were investigated in the stool samples of 38 AIDS patients (23 with chronic diarrhea and 15 without diarrhea) prospectively. At least three stool samples from each patient were investigated microscopically for ova or trophozoites. The samples were concentrated with formol-ether method and wet preparations stained with lugol were examined. In addition, the concentrated samples were stained with modified asid-fast (Kinyoun's), rhodamine-auramine, modified trichrom and calcoflor methods. Enteric parasites were detected in 18 (47%) of the 38 patients, 16 patients harbored a single parasite, and 2 patients were found to be infected with more than one parasite. Only one (7%) of 15 AIDS patients without diarrhea, were found to be infected with Giardia lamblia. On the other hand, 17 (74%) of 23 AIDS patients with chronic diarrhea were found to be infected with various enteric parasites. Cryptosporidium spp. was detected in 9 (39%) of these 23 patients, and in 2 of them Microsporidium spp. accompanied Cryptosporidium. In 2 (9%) of these 23 patients G. lamblia were detected, while Isospora belli, Blastocystis hominis, Entamoeba histolytica, Strongyloides stercoralis and Trichuris trichiura were detected in one patient each. As a result, the detection rate of emerging parasites, including Cryptosporidium spp, Microsporidium spp, I. belli, B. hominis, and S. stercoralis was significantly higher than conventional parasites (39% versus 13%; z=2.34, p=0.01), and CD4 T cell counts were found to be significantly lower among AIDS patients with chronic diarrhea than those without diarrhea (x2=34.33, p<0.001).

AIDS-Related Opportunistic Infections↗
PubMed2004

[Histology in diagnosis of parasitic diseases].

Many pathogenic organisms cause inflammatory lesions and microscopic findings are a useful diagnostic tool for the aetiological diagnosis. However, the histological lesions are limited in respect to many biological agents that can damage the tissues. The histologic hallmark of parasitic diseases is mostly granulomatous inflammation. It is characterized by a focal infiltration of macrophages and epithelioid cells. Many giant cells, lymphocytes, plasma cells, fibroblasts and granulocytes can be found. Agents inducing granulomas include helminths and parasites that replicate intracellularly. Some special stains are utilized in histopathology, for example Giemsa's stain is useful to identify Leishmania. Using specific antibodies, immunohistochemical methods provide an aetiological diagnosis. Sometimes, tissue damage can be immuno-mediated depending on deposit of circulating immunocomplexes or T-lymphocytes involvement rather than by direct parasitic injury. Generally, the lesions which can be observed are respectively vasculitis and inflammatory reactions predominantly composed of mononuclear cells, as observed in many viral or bacterial diseases. In these cases, aetiological diagnosis is improved by in situ-PCR. For microscopic identification of parasites in tissues it is also important to be familiar with the kind of parasites most likely to be found in the examined tissue and in that particular host. Localization of parasites can induce hyperplastic-neoplastic lesions. Many parasites have been associated with the occurrence of specific types of neoplasms, but the mechanisms involved are still not well defined. Chronic inflammation and/or immune suppression seem to induce neoplastic proliferation.

Animals↗
PubMed2004

Avian coccidiosis: a disturbed host-parasite relationship to be restored.

The co-evolution of Eimeria and its host the domestic chicken has resulted in a delicate balance of mutual understanding and respect. This balance has been broken by the complete change of the environment in which the parasite was able to reproduce to such an extent that the host, stressed and weakened by heat, crowding and concurrent infections could not combat the shear numbers of organisms. The use of drugs to control the situation has been shown to only temporarily create relief. Resistance widely developed by the flexible genome of the parasite returned new drugs at a greater speed than they had been developed. Improved hygienic measures, better facility management and good understanding of epidemiology of the parasites spreading and proliferation seem the first and most promising set of tools to control the balance. Reduction of stock density may only provide any relief if this is done at a factor of 10 or higher and this is not a realistic measure in relation to the profit. Free-range chickens are an alternative if only animal welfare is at stake. However, in terms of prevalence of parasitic infections, such as coccidia, helminthes or ectoparasites, chickens do not seem to be better off (Permin et al., 2002). Immunological surveillance and the development of safe, effective and economical vaccines are further refinements that can be used to restore the relationship between parasite and host. Several live vaccines are effective and applied, but certainly have drawbacks in safety and production. New technology such as recombinant vectors together with a better understanding of the cell biology of the parasite from biological and genomic information should provide improved vaccines for the future. The strong genetically determined characteristics involved in the induction and maintenance of a sustainable protective immune response might turn out to be of decisive importance for the success of these strategies. The consequences for the physiology of the parasite remain to be understood.

Animals↗
PubMed2004

Cryptosporidiosis and other intestinal parasitic infections in patients with chronic diarrhea.

OBJECTIVE: To consider the relationship of the parasitic infections including cryptosporidium with chronic diarrhea. Also the effect of chronic disease as pulmonary tuberculosis (TB) and nosocomial infection on the occurrence rate of parasites in cases of chronic diarrhea. METHODS: Stool samples were collected from 205 patients in teaching, general, child and maternity hospitals in Basrah, Iraq, suffering from chronic diarrhea during 2000. Out of these patients, there were 40 patients with pulmonary TB and 50 inpatients with nosocomial infection. Also 175 apparently healthy individuals who have no episodes of diarrhea for at least 2-months were served as a control group. Direct smear method and then formalin ether sedimentation method were carried out for stool samples to detect intestinal parasites. Fecal smears were prepared from the sediment and stained by the modified Ziehl Neelsen stain for the recovery of red pink oocysts of cryptosporidium. RESULTS: Out of the 205 examined patients, cryptosporidium oocysts were found to be excreted in 20 (9.7%) patients in comparing to 1.1% of the control group. The difference is statistically significant. There were 109 (53.2%) patients found to be positive for intestinal parasitic infections compared to 26 (14.8%) of the control group. The difference is also statistically significant. Out of the 40 TB patients, 2 (5%) were found to excrete cryptosporidium oocysts and also 27 (67.3%) were positive for intestinal parasites. In addition, there were 4 (8%) excreting cryptosporidium oocysts and 23 (46%) infecting by intestinal parasites among the in patients with nosocomial infection. CONCLUSION: Both acid and non-acid fast parasites should be considered in the differential diagnosis of undiagnosed chronic diarrhea especially among patients with pulmonary TB or nosocomial infection.

Adolescent↗
PubMed2004

Intestinal parasitic infections and micronutrient deficiency: a review.

Malnutrition including vitamin A and iron deficiency and parasitic diseases have a strikingly similar geographical distribution with the same people experiencing both insults together for much of their lives. Parasitic infections are thought to contribute to child malnutrition and micronutrient deficiency through subtle reduction in digestion and absorption, chronic inflammation and loss of nutrients. Parasites may affect the intake of food; it's subsequent digestion and absorption, metabolism and the maintenance of nutrient pools. The most important parasites related to nutritional status are intestinal parasites especially soil transmitted helminthes, Giardia duodenalis, Entamoeba histolytica, followed by other parasites such as the coccidia, Schistosoma sp. and malarial parasites.

Anemia, Iron-Deficiency↗
PubMed2005

Host-parasite and genotype-by-environment interactions: temperature modifies potential for selection by a sterilizing pathogen.

Parasite-mediated selection is potentially of great importance in modulating genetic diversity. Genetic variation for resistance, the fuel for natural selection, appears to be common in host-parasite interactions, but responses to selection are rarely observed. In the present study, we tested whether environmental variation could mediate infection and determine evolutionary outcomes. Temperature was shown to dramatically alter the potential for parasite-mediated selection in two independent laboratory infection experiments at four temperatures. The bacterial parasite, Pasteuria ramosa, was extremely virulent at 20 degrees C and 25 degrees C, sterilizing its host, Daphnia magna, so that females often never produced a single brood. However, at 10 degrees C and 15 degrees C, the host-parasite interaction was much more benign, as nearly all females produced broods before becoming sterile. This association between virulence and temperature alone could stabilize coexistence and lead to the maintenance of diversity, because it would weaken parasite-mediated selection during parts of the season. Additionally, highly significant genotype-by-environment interactions were found, with changes in clone rank order for infection rates at different temperatures. Our results clearly show that the outcome of parasite-mediated selection in this system is strongly context dependent.

Animals↗
PubMed2005

Dispersal in a parasitic worm and its two hosts: consequence for local adaptation.

Characterizing host and parasite population genetic structure and estimating gene flow among populations is essential for understanding coevolutionary interactions between hosts and parasites. We examined the population genetic structure of the trematode Schistosoma mansoni and its two host species (the definitive host Rattus rattus and the intermediate host Biomphalaria glabrata) using microsatellite markers. Parasites were sampled from rats. The study was conducted in five sites of the Guadeloupe Island, Lesser Antilles. Mollusks display a pattern of isolation by distance whereas such a pattern is not found neither in schistosomes nor in rats. The comparison of the distribution of genetic variability in S. mansoni and its two host species strongly suggests that migration of parasites is principally determined by that of the vertebrate host in the marshy focus of Guadeloupe. However, the comparison between genetic differentiation values in schistosomes and rats suggests that the efficacy of the schistosome rat-mediated dispersal between transmission sites is lower than expected given the prevalence, parasitic load and migration rate of rats among sites. This could notably suggest that rat migration rate could be negatively correlated to the age or the infection status of individuals. Models made about the evolution of local adaptation in function of the dispersal rates of hosts and parasites suggest that rats and mollusks should be locally adapted to their parasites.

Animals↗
PubMed2006

Intestinal parasitic infections among school children of the Dhahira Region of Oman.

OBJECTIVE: To determine the prevalence of intestinal parasitic infections among primary school children in Dhahira region of Oman. METHODS: The study took place in the Dhahira region of Oman from September 2004 to March 2005. We randomly recruited 436 students of 9-10 years of age. Their anthropometric measurements were noted. We collected the stool sample of each student and examined for different intestinal parasites. Stereoscopic microscopy and the World Health Organization's approved KATO-KATZ technique were used. RESULTS: Of the 436 students examined, 65 children (15%) were undernourished (body mass index (BMI) <14 kg/m(2)). The prevalence of intestinal parasitic infections was 38.7% (95% CI 33.2-42.2). The prevalence of protozoan infection was 36% while helminth infection was 9.4%. The prevalence of Entamoeba histolytica/Entamoeba dispar was 24%, Giardia species 10.5% and Escherichia coli 1.4%. The hookworm (Ancylostoma duodenale, Necator americanus), Ascariasis lumbricoides, Trichuris trichiura, Hymenolepiasis nana, Taenia species, Enterobius vermicularis and Strongyloides infections in our study had very low prevalence. Only 29 (6.4%) students had parasitic infection by more than one parasite. The wet zone was significantly associated to the intestinal parasitic infections [Adjusted odds ratio (OR)=3.2 (95% CI 1.9-5.2)]. CONCLUSION: Dhahira region could be classified as low prevalence and low intensity area for soil transmitted helminths infections. However, the magnitude of the protozoan infection was high. The school health program should focus on parasitic infection treatment and addressing the underlying causes of this problem.

Animals↗
PubMed2006

[Seed germination characteristics of parasitic plant and its host recognition mechanisms].

Parasitic plants are widely distributed in various ecological environments, with different growth habits and host recognition mechanisms. This paper discussed the distinctive seed germination characteristics of root parasitic plants such as Orobanche and Striga, summarized the signals for parasitic seed germination discovered up to now, and reviewed the effects of various germination signals, plant hormones and several fungal metabolites on the host recognition of parasitic plants, as well as the respiration characteristics during the conditioning, and the activating mechanism of the signals for parasitic seed germination. The induction of various differentiated calli in different Orobanche species, and the establishment of novel in vitro aseptic infection system and its application in the host recognition of parasitic plants were also discussed, with the present problems in researching the recognition mechanisms between parasitic plants and hosts put forward, and the further work prospected.

Germination↗