Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “parasite”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89Linked to original sources
PubMed2004

Nutritional factors, parasite infection and allergy in rural and suburban Vietnamese school children.

Urban areas often have more allergy than rural areas. Dietary patterns and parasite infection have been suggested as possible related factors. This study evaluated the prevalence of allergy in school children in one rural and suburban area of Vietnam where parasite infection is common. A total of 195 children aged 9 to 13 years old completed a self-administered allergy questionnaire and provided blood and stool samples for analysis. Nutritional status, dietary intake and parasite infection were determined in all participants. Allergy was more common in girls (10.7% vs. 7.6%), suburban children (11.8% vs. 6.9%), children with weight-for-age (16.7% vs. 6.0%) and height-for-age (14.8% vs. 4.9%) in the 10th to 75th percentile compared to <3rd percentile, and in children without trichuriasis compared to light trichuriasis (12.5% vs. 9.3%), although none of these comparisons were statistically significant. Logistic regression adjusted for sex, age and area of residence revealed no association between allergy and nutritional status, food intake or parasite infection. Intake of riboflavin, however, was negatively associated with allergy (OR=0.00, 95% CI:0.00-0.65, p=0.038). In conclusion, we were unable to detect any association between allergy and nutritional status, diet, or parasite infection. However, in a population with high undernutrition and parasite infection, the prevalence of allergy was low and the extremely low intake of riboflavin was associated with a higher risk of allergy.

Adolescent↗
PubMed2006

Immune responses to asexual blood-stages of malaria parasites.

The blood stage of the malaria parasite's life cycle is responsible for all the clinical symptoms of malaria. The development of clinical disease is dependent on the interplay of the infecting parasite with the immune status and genetic background of the host. Following repeated exposure to malaria parasites, individuals residing in endemic areas develop immunity. Naturally acquired immunity provides protection against clinical disease, especially severe malaria and death from malaria, although sterilizing immunity is never achieved. Given the absence of antigen processing in erythrocytes, immunity to blood stage malaria parasites is primarily conferred by humoral immune responses. Cellular and innate immune responses play a role in controlling parasite growth but may also contribute to malaria pathology. Here, we analyze the natural humoral immune responses acquired by individuals residing in P. falciparum endemic areas and review their role in providing protection against malaria. In addition, we review the dual potential of cellular and innate immune responses to control parasite multiplication and promote pathology.

Animals↗
PubMed2002

The interfaces of oligomeric proteins as targets for drug design against enzymes from parasites.

Millions of people worldwide are infected by some kind of parasite and millions are in risk of contracting infection. In addition, it is now accepted that parasites are rapidly developing resistance to drugs that a few years ago were effective. This gloom picture underscores the urgent need to develop new drugs against parasitic diseases. Fortunately, the important technological advances that have been made in the past years will, in principle, facilitate the discovery of new and effective agents against parasitic diseases. In many of the approaches for drug design the basic premise is the identification of a macromolecule that is central to the life of the parasite. Because the life of all living organisms depends on multiple protein-protein interactions and the function of oligomeric proteins, it is worthwhile to explore if protein interfaces could be exploited for drug design. Here we review some of the work that has been done in this direction, and attempt to call attention to the richness of protein-protein interfaces for the design of agents that could lead to the development of drugs against parasitic diseases.

Animals↗
PubMed2006

Immunological aspects of nematode parasite control in sheep.

Gastrointestinal nematode parasitism is arguably the most serious constraint affecting sheep production worldwide. Economic losses are caused by decreased production, the costs of prophylaxis and treatment, and the death of the infected animals. The nematode of particular concern is Haemonchus contortus, which can cause severe blood loss resulting in anemia, anorexia, depression, loss of condition, and eventual death. The control of nematode parasites traditionally relies on anthelmintic treatment. The evolution of anthelmintic resistance in nematode populations threatens the success of drug treatment programs. Alternative strategies for control of nematode infections are being developed, and one approach is to take advantage of the host's natural or acquired immune responses, which can be used in selection programs to increase the level of resistance in the population. Vaccination can also be used to stimulate or boost the host's acquired immunity. The induction of protective resistance is dependent on the pattern of cytokine gene expression induced during infection by two defined CD4+ T-helper cell subsets, which have been designated as Th1 or Th2. Intracellular parasites most often invoke a Th1-type response, and helminth parasites a Th2-type response. Breeds of sheep resistant to infection have developed resistance over a much longer term of host-parasite relationship than genetically selected resistant lines. The immune components involved in these different responses and types of host-parasite relationships will be reviewed. The potential for using vaccines has been investigated, with variable results, for several decades. The few successes and potential new antigen candidates will also be reviewed.

Animal Husbandry↗
PubMed1994

Intestinal parasites in refugees and asylum seekers entering the Stockholm area, 1987-88: evaluation of routine stool screening.

In order to evaluate the results of routine screening for intestinal parasites, the medical records of 4592 refugees and asylum seekers arriving in the Stockholm area from January 1987 to December 1988 were reviewed. 3938/4592 (86%) delivered stool specimens for examination and intestinal parasites were demonstrated in 651/3938 (17%). Protozoa, mainly Giardia intestinalis, were found in 403/3938 (10%) and helminths, mainly nematodes, in 277/3938 (7%). Intestinal parasites were most frequently recovered in subjects coming from the Indian subcontinent/Southeast Asia and Africa (infection rates 39% and 25%, respectively). Extensive variations in the prevalence of intestinal parasite infection in various ethnic groups (range 4%-39%) were largely attributable to variations in prevalence of helminthic infections (range 2%-34%). Origin from the tropics or subtropics as well as low age, male sex, rural region of domicile before/during exile and short length of stay in Sweden were related to intestinal parasitic infection. Lack of data on morbidity in untreated asymptomatic carriers, limited risks for transmission of the recovered parasites in Sweden as well as the expenses for screening indicate a need for reconsideration of the present praxis of mass screening in favour of a selective screening of high-risk groups based on country of origin and age.

Adolescent↗
PubMed2005

Joint effects of parasitism and pollution on oxidative stress biomarkers in yellow perch Perca flavescens.

Yellow perch Perca flavescens were collected from a contaminated site and a reference site in the St. Lawrence River, Quebec, Canada. Fish were assessed for oxidative stress (lipid peroxidation and reduced glutathione levels) and parasitism by the nematode Raphidascaris acus and metacercariae of the digenean Apophallus brevis. Lipid peroxidation is not only considered a measure of oxidative stress, but of stress in general, and thus serves as an indicator of fish health. Fish from the contaminated site exhibited higher levels of lipid peroxidation than those from the reference site, independent of parasitic infections. However, fish infected with R. acus at the contaminated site tended to have higher levels of lipid peroxidation than uninfected fish at the same site, whereas no difference was observed between infected and uninfected fish at the reference site. Yellow perch infected with > 10 metacercariae of A. brevis expressed higher levels of lipid peroxidation than those infected with < 10 metacercariae at both the contaminated and the reference sites. No differences were found in levels of reduced glutathione in liver or muscle in relation to site or either parasite species. Results support the use of lipid peroxidation as a biomarker of water contamination. They further suggest that lipid peroxidation may be used as a biomarker of pathological effects caused by parasitism. Most importantly, results demonstrate that contaminants and parasites occurring together exacerbate oxidative stress in fish, suggesting that parasitized fish in polluted environments are in a poorer state of health than uninfected fish.

Analysis of Variance↗
PubMed2005

Myxidium mackiei (Myxosporea) in Indo-Gangetic flap-shelled turtles Lissemys punctata andersonii: parasite-host interaction and ultrastructure.

Myxosporeans are common parasites of fish, and uncommon parasites of amphibians, reptiles and invertebrates, that can cause significant morbidity and mortality. The common genus Myxidium infects the excretory system of turtles, yet knowledge of its pathogenicity in these hosts is limited. We offer new knowledge of morphological and ultrastructural aspects of host-parasite interactions in Myxidium infections from our recent diagnostic investigations on captive freshwater turtles listed in CITES (Appendix II). We investigated the cause of death of 2 adult Indo-Gangetic flap-shelled turtles Lissemys punctata andersonii from a zoo collection. After post-mortem examination, tissues were processed for histopathology, and special stains were used to demonstrate morphology of myxosporean spores. Additional kidney tissue, immersion-fixed in formalin, was processed for transmission electron microscopy. Both turtles were infected with a myxosporidian, Myxidium mackiei, in the kidney, which occluded 5 to 10% of the renal proximal convoluted tubules. The polysporic plasmodia contained pairs of developing and mature spores. Each mature, spindle-shaped spore had 2 asymmetric valves (1 overlapping, 1 overlapped), with 10 to 13 and 10 to 14 longitudinal ridges per valve, and 2 polar capsules each containing a polar filament with 4 to 5 turns. A pair of spores, each surrounded by a membrane-bound electron-lucent matrix, lay in an enclosing cell within the plasmodium. Regions of the parasite-host interface consisted of undulations of the parasite surface, with intense pinocytotic activity beneath, intermingled with the hosts' microvilli, and endocytotic channels at the apex of renal epithelial cells. The microvilli of the renal epithelial cells of infected tubules were frequently sheared or compressed, or occasionally missing; we did not detect other pathology induced by the parasite. Our report of M. mackiei in L. punctata is a new host record. Both individuals also had disseminated pale yellow nodules (bacterial granulomas) present in lung, heart, kidney, and skeletal muscle, and both were infected with coccidia (tentatively identified as Eimeria sp.) in multiple organs. The cause of death for one turtle was septicemia, but remained unknown for the other individual.

Animals↗
PubMed2026

Molecular mechanisms underlying drug resistance in protozoan parasites: emerging mechanisms and therapeutic perspectives.

Protozoan parasitic infections, including malaria, leishmaniasis, and human African trypanosomiasis, remain major global public health challenges. In the absence of highly effective vaccines, disease control relies primarily on chemotherapy; however, the emergence and spread of drug-resistant parasite populations increasingly threaten treatment efficacy. This review synthesizes current evidence on the molecular mechanisms underlying drug resistance in Plasmodium, Leishmania, and Trypanosoma species through a systematic analysis of literature. The review identifies four interconnected mechanisms that drive the evolution of drug resistance. First, altered drug transport enables parasites to regulate intracellular drug concentrations through mutations, loss, or amplification of membrane transporters, including PfCRT in Plasmodium and AQP2 in Trypanosoma brucei. Second, target modification and genomic plasticity promote resistance through point mutations in drug targets, such as dhfr and dhps in Plasmodium, while kinetoplastids, particularly Leishmania, exploit extensive genomic plasticity, including aneuploidy, gene amplification, and translational reprogramming, to facilitate rapid adaptation under drug pressure. Third, metabolic reprogramming enhances parasite survival by increasing intracellular thiol production, strengthening antioxidant defense systems, and reshaping central carbon and lipid metabolism to mitigate drug-induced stress. Finally, stress response and persistence mechanisms enable subpopulations of parasites to enter dormant, persister-like states characterized by reduced metabolic activity and slowed proliferation, thereby evading both host immune responses and chemotherapeutic agents. Collectively, these findings demonstrate that drug resistance is a dynamic, multifactorial evolutionary process rather than a single molecular event. Addressing this growing challenge requires integrating genomic surveillance, molecular diagnostics, mathematical modeling of resistance transmission, and mechanistic insights into parasite persistence into future drug discovery and disease control strategies. Such an integrated approach is essential for improving the durability of antiprotozoal therapies and advancing global efforts to control neglected protozoan diseases.

antiprotozoal therapy↗
PubMed1994

Eosinophilia caused by parasites.

Eosinophilia is defined as an absolute count of > 500 eosinophils per mm3 of peripheral blood. Eosinophilia is associated with many disorders, limiting its usefulness as a diagnostic tool in screening expatriates for parasite infections. In addition, only tissue-invasive helminthic parasites cause eosinophilia, which limits its general application as a screening tool for parasitic infections. Because eosinophilia may resolve spontaneously over time, the life cycle of parasites must be considered when evaluating eosinophilic patients, and repeated stool examinations or appropriate serology may be necessary to make the correct diagnosis. Future work on the risks associated with subclinical parasite infections would be helpful to place eosinophilia and other screening tests in proper perspective. Referral of difficult cases to specialists in travel medicine should be considered because detailed information about the geographic distribution and life cycle of helminthic parasites is often crucial to making the correct diagnosis.

Eosinophilia↗
PubMed2005

Stage-specific expression of surface antigens by Toxoplasma gondii as a mechanism to facilitate parasite persistence.

Toxoplasma persists in the face of a functional immune system. This success critically depends on the ability of parasites to activate a strong adaptive immune response during acute infection with tachyzoites that eliminates most of the parasites and to undergo stage conversion to bradyzoites that encyst and persist predominantly in the brain. A dramatic change in antigenic composition occurs during stage conversion, such that tachyzoites and bradyzoites express closely related but antigenically distinct sets of surface Ags belonging to the surface Ag 1 (SAG1)-related sequence (SRS) family. To test the contribution of this antigenic switch to parasite persistence, we engineered parasites to constitutively express the normally bradyzoite-specific SRS9 (SRS9(c)) mutants and tachyzoite-specific SAG1 (SAG1(c)) mutants. SRS9(c) but not wild-type parasites elicited a SRS9-specific immune response marked by IFN-gamma production, suggesting that stage-specificity of SRS Ags determines their immunogenicity in infection. The induction of a SRS9-specific immune response correlated with a continual decrease in the number of SRS9(c) cysts persisting in the brain. In contrast, SAG1(c) mutants produced reduced brain cyst loads early in chronic infection, but these substantially increased over time accompanying a hyperproduction of IFN-gamma, TNF-alpha, and IL-10, and severe encephalitis. We conclude that stage-specific expression of SRS Ags is among the key mechanisms by which optimal parasite persistency is established and maintained.

Animals↗
PubMed1998

Intestinal parasitic infections in human immunodeficiency virus (HIV)-positive and HIV-negative individuals in San Pedro Sula, Honduras.

Honduras has at least five-times more human immunodeficiency virus (HIV)-infected individuals than any other country in Central America. The relationship between HIV status and the presence of intestinal parasites in this part of the world is unknown. This study presents the results from a prospective, comparative study for the presence of parasites in 52 HIV-positive and 48 HIV-negative persons in San Pedro Sula, Honduras. Infection with HIV was determined by microagglutination and confirmed by Western blot analysis. Parasites were detected in stools using formalin-ether concentration, and Kinyoun and trichrome staining. Age, sex, and clinical state of HIV infection were recorded for each study participant. Our results indicate that Cryptosporidium parvum and Strongyloides stercoralis, which are intracellular or live in the mucosa, were found exclusively in persons infected with HIV. In comparison, the prevalence of the extracellular parasites Giardia lamblia, Ascaris lumbricoides, and Trichuris trichiura was significantly higher (P < 0.05) in persons who were HIV-negative. Trichuris worms are in contact with the gut epithelium and less so with the mucosa, whereas Strongyloides lives within the gut mucosa. It is possible that changes in the gut epithelium due to HIV infection do not affect the mucosa and therefore would not affect Strongyloides. We conclude that infection with HIV may selectively deter the establishment of certain intestinal parasites. This may be due to the fact that HIV-induced enteropathy does not favor the establishment of extracellular parasites. Intracellular and mucosal dwelling organisms, however, may benefit from pathologic changes and reduced local immune responses induced by the virus, which, in turn, may lead to higher prevalence among HIV-infected individuals.

Adolescent↗
PubMed2002

Pathogenic intestinal parasites and bacterial agents in solid wastes.

OBJECTIVE: To determine the profile of potentially pathogenic enteric parasites and bacterial agents in municipal refuse dumps in Ibadan, Nigeria. DESIGN: A cross-sectional survey. SETTING: Five major market places refuse dumps in Ibadan municipality, Nigeria. METHODS: The major market places in Ibadan city were randomly selected by lottery method. The refuse sludge were sampled and examined parasitologically and bacteriologically using the methods as described. Data analysis was done by using chi-square test where applicable. RESULTS: Cases of multiple intestinal parasites and bacterial agents were commonly encountered in the sludge refuse samples. The commonly found parasitic agents were of both human and veterinary importance. These include Ascaris Lumbricoides (9.3 egp), Entamoeba histolytica (8.07 cyst per gram), Hookworm/strongyle (6.27 egp) and Ascaris suum (1.07 egp). Others were Ascaris vitolorum (1.09 epg), Strongyloides papillosu (0.52 larvae per gram.), Schistosoma suis (0.31 epg) Dicrocoelium dendriticum (0.9 egp). The most commonly found bacterial agents were Klebsiella species, Escherichia Coli, Proteus species, streptococci, and other gram-positive organisms. Climatic conditions affected the distribution of both parasites and bacterial agents in the sludge (P<0.001). More intestinal parasites 2423 (53.4%) and bacterial agents 2150 (27.2%) were encountered at mean air temperature 26.1 +/- 0.6, mean relative humidity of 72 +/- 3.5%. The degree of contamination by market locations varies significantly (P<0.001). CONCLUSION: A high degree of contamination of solid waste dumpsites with bacterial and parasitic agents was observed in the present study. As a result of the public health importance of the organisms isolated it is opined that well planned waste management and health education programs will go a long way to reduce the potential epidemic risks posed by such sites in Ibadan, Nigeria.

Animals↗
PubMed1982

Blood parasites of some birds from the Lorraine region, France.

A total of 1650 birds of 56 species representing 21 families (primarily Passeriformes), was examined for blood parasites in the Lorraine region of France. Only 120 (7.3%) birds were infected, with members of the Paridae, Sylviidae and Turdidae the most frequently parasitized. Haemoproteids were the most commonly encountered parasites followed by the leucocytozoids. Other avian hematozoon genera were uncommon. Prevalence of parasitism was closely similar each year over a three-year period. Immature birds were first noted to be infected with Leucocytozoon in mid-June, suggesting transmission in late May to early June. Haemoproteids were first noted in immature birds in early July, suggesting transmission in mid-June. A review of the literature indicates that the prevalence of parasitism by avian blood parasites has decreased in western Europe since the turn of the century and is currently much lower than the prevalence encountered in Scandinavia, central Russia and eastern North America.

Animals↗
PubMedDate not supplied

[The effect of lactation on the parasitism of rats by Strongyloides ratti (author's transl)].

In lactating females of many animal species infested by Nematoda, the self-cure is, if not suppressed, at least very distinctly delayed. It does not appear that an immunological deficiency is the cause of this. We show that this phenomenon also exists in lactating female rats with Strongyloides ratti parasites. In fact, for Strongyloides ratti, the maintenance of the worms is not the only notable modification determined by lactation; much more important is the decrease in the intensity of the parasitism. This aspect is not mentioned by writers who have only studied the different parasitic states in their final phase. Parallel to these alterations in the parasitism, the evolution of the corticosteronemy differs, from two points of view, from that described in infested virgin rats: --Suppression of the hypercorticosteronemy which normally appears 48 hours after infestation; --Attenuation of the hypocorticosteronemy which usually sets in from the tenth day of infestation. This opposition of lactation to the variations in the corticosteronemy induced by the worms is explained by the effect of lactation on the secretion of gluco-cortico-steroids, described under the term of "buffer effect of lactation". The decrease in the intensity of the parasitism may be explained by the fact that lactation, by preventing the hypercorticosteronemy normally caused by larval migration, permits the intervention of aspecific defences. As for the prolongation of the parasitism, it would seem to result on one hand, from a reduced solicitation of the means of defence owing to a smaller number of worms and, on another hand, from the slowing down of the hypocorticosteronemy through the buffer effect of lactation with all the consequences flowing from this at the level of the specific and aspecific defence reactions.

Adrenal Cortex Hormones↗
PubMed1976

Incidence of intestinal parasites in children of different socio-economic population of Dacca city.

Stool samples of 1500 children of different socio-economic status of Dacca city was examined for the presence of intestinal parasites. Samples were collected on voluntary basis which may be treated as randomised. Out of these 1500 children, 816 were male and 684 were female. The overall incidence of parasites was 65.80%, the male children slightly prepondering over the female children. Children of age group 6-10 years showed high incidence of almost all the parasites. Children of Basti area showed the highest incidence (about 90%) and most of them harboured multiple parasites. About 27.13% of infants under the age of one year (mostly from Basti area) harboured parasites. Intestinal parasites were observed that both housing and economic status played vital roles in the occurrence of intestinal parasitosis but the housing and environmental conditions were found to be in a stronger position than economic status.

Adolescent↗
PubMed1998

Eosinophilia, anemia and parasitism in a rural region of northwest Thailand.

Parasitic infections are prevalent in Thailand. The parasites' relationship with anemia and eosinophilia has been rarely reported due to limited health care access, especially in rural areas. We studied the prevalence and relationship between eosinophilia, anemia and parasitism in 169 Thai-Karens from Mae Lamung and Mae Chan subdistricts, Umphang district, Tak Province, using an automated complete blood counter, and microscopic examination for intestinal parasites and microfilaria. In Mae Chan, 5 individuals were microfilaremic, 72% of individuals examined were infected with at least one kind of intestinal parasites, and 50% were anemic, with normal mean red cell volume (MCV). In Mae Lamung, 46% were parasitized (Triteeraprapab et al, 1997) but none were microfilaremic or anemic. In both populations, eosinophilia was prevalent (77%). Hookworm infection was found to be significantly associated with eosinophilia, but not anemia nor microcytosis of red cells.

Adolescent↗
PubMed1999

Transmission stages of Plasmodium: does the parasite use the one same signal, provided both by the host and the vector, for gametocytogenesis and sporozoite maturation?

Among the microorganisms that strictly depend upon other organisms (hosts or vectors) for achieving their life cycle, protozoan and metazoan parasites have been often primarily distinguished through the major pathogenic processes they could induce. A variety of different mechanisms linked to parasitism can indeed systemically (e.g. Plasmodium falciparum) or locally (e.g. Toxoplasma gondii) induce important alterations of tissue homeostasis. But more than obvious pathogenicity, it is the capacity to be transmitted that is essential for parasite survival and there is increasing evidence that certain parasites can achieve their life cycle to the point of transmission in the absence of clinically detectable processes. For this, constitutive microenvironments of the host or vector can be exploited. Moreover, parasites are sometimes able to highjack effectors of the host's immune response towards conditioning the microenvironments which are permissive to differentiation of transmissible developmental stages. Based on a few examples taken from studies on the transmission stages of Leishmania, Toxoplasma and Plasmodium, we have here attempted to formulate a few hypothesis on the biology of the transmission stages of P. falciparum, i.e. on gametocytogenesis and sporozoite maturation. As discussants, we may have been somewhat dwarfed by issues evoked by the organizers of this meeting in the title of the session, i.e. 'Vector-parasite-man interactions'!... In reaction, we may have taken refuge in somewhat over-selective comments, biased by the objects of our personal research....

Animals↗
PubMed2000

The role of parasitic diseases as causes of mortality in cattle in a high potential area of central Kenya: a quantitative analysis.

Postmortem records of cattle brought to the Veterinary School in Kabete near Nairobi were examined for a period of 15 years (1984-1998, inclusive) in order to establish the role that parasitic diseases played as causes of death. The cattle were mainly of exotic breeds but a few were crosses or of indigenous breeds. There was a total of 1413 cases of deaths from various diseases of which 177 (13%) were due to parasites. The tick-borne diseases were in high proportions and accounted for 84,7% among the parasitic causes, which represented 10,6% of all the deaths recorded. The main tick-borne disease was East Coast fever (ECF) (65%) followed by heartwater (10,2%), babesiosis (5,1%) and anaplasmosis (4,5%). Hydatidosis was responsible for 7,3% of deaths from parasitic causes. Deaths from ECF were recorded in all the 15 years and in high proportions compared to those due to heartwater (8/15), babesiosis (7/15) and anaplasmosis 5/15). Over the period under consideration, no decline was noted among various disease conditions despite advances made in controlling tick vectors and in the treatment of various parasitic conditions. The area covered by this study has the advantage of having several veterinary-related institutions close by. Hence knowledge and awareness about livestock diseases is relatively high compared to other parts of the country. It is therefore challenging to the Veterinary Department to examine the service delivery systems and other factors that may contribute to the persistent presence of these fatal parasitic conditions of cattle.

Animals↗