Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Parasite Control”

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 1,135 records · Page 63Linked to original sources
PubMed1983

Plasmodium falciparum: attenuation by irradiation.

The effect of irradiation on the in vitro growth of Plasmodium falciparum was investigated. The cultured malarial parasites at selected stages of development were exposed to gamma rays and the sensitivity of each stage was determined. The stages most sensitive to irradiation were the ring forms and the early trophozoites; late trophozoites were relatively insensitive. The greatest resistance was shown when parasites were irradiated at a time of transition from the late trophozoite and schizont stages to young ring forms. The characteristics of radiosensitive variation in the parasite cycle resembled that of mammalian cells. Growth curves of parasites exposed to doses of irradiation upto 150 gray had the same slope as nonirradiated controls but parasites which were exposed to 200 gray exhibited a growth curve which was less steep than that for parasites in other groups. Less than 10 organisms survived from the 10(6) parasites exposed to this high dose of irradiation; the possibility exists of obtaining radiation-attenuated P. falciparum.

Animals↗
PubMed2005

Mosquito immunity against Plasmodium.

Understanding the molecular mechanisms of the innate immune responses of Anopheles gambiae against Plasmodium parasites is of great importance for current efforts to develop novel strategies for malaria disease control. The parasite undergoes substantial stage-specific losses during its development in the mosquito, which in some cases lead to complete refractoriness of the mosquito against the parasite. The underlying genetics of refractoriness are complex and multifactorial. Completion of the genome sequence of An. gambiae 2 years ago, together with the development of DNA microarrays in this species and the extension of the RNAi technique to adult mosquitoes, has allowed comparative and functional genomic approaches of the mosquito innate immune system. A variety of factors were shown to negatively affect the development of Plasmodium parasites in the mosquito, in some cases leading to complete transmission blockage. In addition, mosquito factors have been identified that play positive roles and are required for successful transmission of the parasite. These findings indicate a highly complex interplay between parasite and vector. Research is continuing to identify new factors involved in this interaction and to decipher the interplay of these molecules and their regulation.

Animals↗
PubMed2000

Uptake of apoptotic cells drives the growth of a pathogenic trypanosome in macrophages.

After apoptosis, phagocytes prevent inflammation and tissue damage by the uptake and removal of dead cells. In addition, apoptotic cells evoke an anti-inflammatory response through macrophages. We have previously shown that there is intense lymphocyte apoptosis in an experimental model of Chagas' disease, a debilitating cardiac illness caused by the protozoan Trypanosoma cruzi. Here we show that the interaction of apoptotic, but not necrotic T lymphocytes with macrophages infected with T. cruzi fuels parasite growth in a manner dependent on prostaglandins, transforming growth factor-beta (TGF-beta) and polyamine biosynthesis. We show that the vitronectin receptor is critical, in both apoptotic-cell cytoadherence and the induction of prostaglandin E2/TGF-beta release and ornithine decarboxylase activity in macrophages. A single injection of apoptotic cells in infected mice increases parasitaemia, whereas treatment with cyclooxygenase inhibitors almost completely ablates it in vivo. These results suggest that continual lymphocyte apoptosis and phagocytosis of apoptotic cells by macrophages have a role in parasite persistence in the host, and that cyclooxygenase inhibitors have potential therapeutic application in the control of parasite replication and spread in Chagas' disease.

Amino Acid Chloromethyl Ketones↗
PubMedDate not supplied

[Toxic effects and in vitro inefficacy of deltamethrin on larvae of Rhipicephalus sanguineus from Goiânia, Goiás, Brazil].

It has been observed that formulations of deltamethrin developed for disinsectization of infested places and control of parasitic arthropods of bovines and equines have frequently been used by breeders of dogs to control ticks in their animals and kennels, but without due consideration of the correct dosage or means of application. With the purpose of evaluating the efficacy of this product on Rhipicephalus sanguineus, bioassays were realized with larvae at 27+/-1 degrees C, UR>80% and light period of 12 hours. The mortality and toxicological effects were observed for 30 h, at 6 h intervals. Important toxicological effects were observed on the larvae, such as lack of co-ordination, knock-down and paralysis followed by death, although the lethal capacity of the product after 30 h was low, with mean mortality of only 34%, 40.2%, 46% and 57.6% respectively, for the 0.5 ml/l; 1 ml/l; 2 ml/l/; and 3 ml/l dosages. There was no mortality in the control group. The results obtained did not indicate the use of this formulation, in the tested dosages, as a method of choice for R. sanguineus control.

Animals↗
PubMed1996

Antigenic variation and the within-host dynamics of parasites.

Many parasites exhibit antigenic variation within their hosts. We use mathematical models to investigate the dynamical interaction between an antigenically varying parasite and the host's immune system. The models incorporate antigenic variation in the parasite population and the generation of immune responses directed against (i) antigens specific to individual parasite variants and (ii) antigens common to all the parasite variants. Analysis of the models allows us to evaluate the relative importance of variant-specific and cross-reactive immune responses in controlling the parasite. Early in the course of infection within the host, when parasite diversity is below a defined threshold value (the value is determined by the biological properties of the parasite and of the host's immune response), the variant-specific immune responses are predominant. Later, when the parasite diversity is high, the cross-reactive immune response is largely responsible for controlling the parasitemia. It is argued that increasing antigenic diversity leads to a switch from variant-specific to cross-reactive immune responses. These simple models mimic various features of observed infections recorded in the experimental literature, including an initial peak in parasitemia, a long and variable duration of infection with fluctuating parasitemia that ends with either the clearance of the parasite or persistent infection.

Animals↗
PubMed2005

Foodborne protozoan parasites.

This report addresses Cryptosporidium, Giardia, Cyclospora, and more briefly, Toxoplasma as the main parasitic protozoa of concern to food production worldwide. Other parasitic protozoa may be spread in food or water but are not considered as great a risk to food manufacture. The protozoan parasites Cryptosporidium, Giardia, and Cyclospora have proven potential to cause waterborne and foodborne disease. Toxoplasma gondii has been considered a risk in specific cases, but humans are not its primary host. Cryptosporidium and Giardia are widespread in the environment, particularly the aquatic environment, and major outbreaks of cryptosporidiosis and giardiasis have occurred as a result of contaminated drinking water. Large outbreaks of waterborne cyclosporiasis have not been identified. Cryptosporidium, Giardia, and Cyclospora have potential significance in the preparation and consumption of fresh produce and in catering practice, in which ready-to-eat foods may be served that have not received heat treatment. None of the three organisms Cryptosporidium, Giardia, and Cyclospora has been shown to be a problem for heat processed food or tap water that has undergone appropriate treatment at a water treatment works. All three are sensitive to standard pasteurisation techniques. Although humans are not a primary host for T. gondii, the potential exists for both waterborne and foodborne toxoplasmosis. Parasitic protozoa do not multiply in foods, but they may survive in or on moist foods for months in cool, damp environments. Their ecology makes control of these parasites difficult. For general control of parasitic protozoa in the food chain, the following steps are necessary: - Follow good hygienic practice in food service and catering industries.- Minimise dissemination of cysts and oocysts in the farming environment and via human waste management.- Include these microorganisms in Hazard Analysis Critical Control Point (HACCP) plans of water suppliers, industries or sectors that use fresh produce, and operations in which contaminated process or ingredient water could end up in the product (e.g., where water supplies may become contaminated).

Animals↗
PubMed1975

Jejunal biopsies in protein-calorie malnutrition and intestinal parasitic infestation in Brazil.

Jejunal biopsies were performed in 71 subjects, who were classified into three groups as follows: Forty-one patients, on a poor diet, without clinical signs of malnutrition, with and without parasitic infestation; nineteen patients with severe protein-calorie malnutrition, with and without parasitic infestation; control group, ten medical students and one of the authors on a normal diet and without parasitic infestation. The dissecting microscope appearance showed mild alteration of the intestinal villi of Group A patients with parasitic infestation and severe alteration on Group B patients, especially those with parasitism. On histological examination, only the total mucosal thickness showed statistically significant differences between the Group B (severe protein malnutrition) and the other groups.

Adolescent↗
PubMed2001

Health promotion approach for the control of food-borne parasitic zoonoses in Nepal: emphasis on an environmental assessment.

Green and Kreuter define health promotion as the use of both education and ecology to encourage and support living conditions conducive to good health. Their PRECEDE-PROCEED model delineates a practical way to cope with health problems using this definition. Applying PRECEDE to Nepal helps identify the steps needed to control the ever-increasing incidence of food-borne parasitic zoonoses (FBPZ) there and in other South Asian countries. In executing the first five steps of the model, we focused on behavioral and environmental assessments to find a method for controlling FBPZ. Through these two assessments, we identified the following behavioral and environmental objectives: establish a meat inspection system by 2003, establish training programs on safe meat production and selling practices by 2003, improve slaughterhouses and slaughtering practices by 2003. The educational and ecological assessments revealed that the necessary predisposing, reinforcing and enabling factors for appropriate control of FBPZ are present in Nepal, while an administration and policy assessment shows Nepal meets PRECEDE requirements through its recent meat inspection legislation. Although the data for each element of the PRECEDE-PROCEED model are limited in Nepal, they clearly tell us to move forward to the PROCEED stage to control FBPZ there as well as in all of South Asia.

Abattoirs↗
PubMed1979

Babesia divergens: the immunisation of splenectomised calves during irradiated piroplasms.

Groups of three splenectomised calves were inoculated with 1 . 2 x 10(10) Babesia divergens-infected erythrocytes irradiated at 24, 28, 32, 36 and 40 kilorads. Control calves were inoculated with 1 . 2 x 10(7) or 1 . 2 x 10(4) non-irradiated parasites. While control animals all experienced severe reactions, animals receiving blood irradiated at 24, 28 and 32 kilorads had mild reactions and were solidly immune to an homologous challenge of 1 . 1 x 10(4) Babesia-infected erythrocytes. Animals receiving parasites irradiated at 36 and 40 kilorads had limited ability to resist the challenge.

Animals↗
PubMed2003

Tritrichomonas foetus: the role played by iron during parasite interaction with epithelial cells.

The aim of this work was to investigate the role played by iron during interaction of Tritrichomonas foetus with cultured epithelial cells. We have observed that the growth rate of T. foetus is influenced by the amount of iron available into culture medium. When organisms maintained for 24h in iron-depleted medium were transferred to an iron-rich one, many protozoan cells exhibited a cytokinesis blockage. Parasites maintained in iron-depleted medium exhibited a significant increase in cytoadhesion when compared with both controls and parasites that had been cultured in medium in which iron was replaced. T. foetus collected from iron-depleted medium also exhibited a reduction in its ability to destroy epithelial cell monolayers and a reduction in the activity of several cysteine proteases. Taken together, the results presented here demonstrate that iron may be an extracellular signal, which seems to modulate the ability of T. foetus to interact with host epithelial cells.

2,2'-Dipyridyl↗
PubMed1987

Evaluation of the morantel sustained release bolus in cows and calves.

The efficacy of the morantel sustained release bolus (MSRB) in controlling gastrointestinal parasitism in beef cattle was assessed during the 1982 spring-autumn grazing season. Forty-eight cows and their calves were allotted to three equal groups. One group (T-1) served as a nonmedicated control group. One MSRB was administered to each calf of the T-2 group, and to each cow and calf of the T-3 group at the beginning of the study. The efficacy of the bolus was assessed by comparison of weight gain performance and parasitological data (fecal worm egg counts, herbage larval counts, worm counts from tracer and principal trial calves, and plasma pepsinogen level determinations). Though not statistically significant, treated calves from Group T-2 had a numerical mean weight gain advantage of 2.6 kg, and those from Group T-3 of 4.7 kg, over control calves. Average daily gains (ADG) for the three groups of calves were 0.69, 0.72, and 0.73 kg, respectively. Untreated cows from Group T-2 and treated cows from Group T-3 outperformed the control cows by 12.3 and 7.5 kg, respectively. Fecal worm egg counts from both groups of treated calves were significantly (P less than 0.01) lower than counts from control calves during the entire 169-day trial; notably, egg counts were reduced by 99% 28 days after MSRB administration to both groups of calves. There were no significant differences in the number of eggs counted from the three groups of cows, probably because of the very low numbers of eggs encountered. Mean total worm burdens of principal calves (six per group) necropsied at trial termination indicated a 91% (P less than 0.01) reduction in Group T-2 and an 87% reduction (P less than 0.01) in Group T-3. Worm-free tracer calves were introduced onto pastures every 28 days to monitor availability of infective larvae. The mean number of worms recovered at necropsy from tracer calves that grazed with control cattle increased as the season progressed. However, the numbers of parasites recovered each month from mid-August through mid-October from tracers that grazed pastures with treated cattle were lower (P less than 0.05) than those levels displayed at trial initiation. In addition, the mean numbers of worms from treated group tracers were lower than from the controls for each necropsy period.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of Variance↗
PubMed1996

Vaccination against hydatidosis using a defined recombinant antigen.

Echinococcus granulosus is the causative agent of hydatid disease in humans and animals. Natural transmission of the parasite occurs between dogs as definitive hosts and animal intermediate hosts. There is an urgent need for improved methods to control the parasite's transmission. Here we describe the development of a vaccine based on a cloned recombinant antigen from the parasite egg (oncosphere). Sheep-vaccinated with the antigen, designated EG95, are protected (mean 96-98%) against hydatidosis developing from an experimental challenge infection with E. granulosus eggs. The vaccine will provide a valuable new tool to aid in control of transmission of this important human pathogen. It also has the potential to prevent hydatid disease directly through vaccination of humans.

Amino Acid Sequence↗
PubMed2004

Seroprevalence of Dictyocaulus viviparus in first grazing season calves in Sweden.

A serological survey was carried out to determine the prevalence and geographical distribution of Dictyocaulus viviparus in calves after their first grazing season in Sweden. A total of 754 animals from 76 randomly selected herds in seven geographical regions were examined between September 24 and December 19, 2001. To get an indication about the geographical distribution of the infection 41 herds with beef-suckler calves were investigated. On each farm, blood was collected from 8 to 10 animals after an average of 26 +/- 24 days post-housing to determine specific IgG1 levels against a possible lungworm sperm antigen that is highly specific against patent infections of D. viviparus. We also investigated the seroprevalence of lungworm infection in relation to cattle management. In one region additional samples were analysed from 35 herds either with: (a) beef-suckling calves that were dewormed at housing, (b) untreated organically raised dairy calves, and finally from conventionally raised dairy calves either, (c) with or, (d) without a prophylactic anthelmintic treatment programme against gastrointestinal parasites on pasture. A questionnaire was used to obtain information about herd size and management, including measures to control nematode parasites on the farm. A total of 86 (11.8%) out of 754 animals had antibodies against D. viviparus, and at least one infected individual was detected in 30 (39.5%) of the 76 herds examined. Lungworm infected animals were found throughout the country and there was no significant differences between regions, although in southern and southwestern Sweden 70.0% of the herds were infected. Furthermore, there were no major differences in the seroprevalence in relation to management. Between 40.0 and 44.4% of the herds were infected irrespective of management, with the exception of calves from organic herds where no seropositive samples were found (0%). This result is in contrast to previous findings of lungworms in Sweden, and indicates that the parasite status on organic farms is diverse.

Animal Husbandry↗
PubMed1998

Drug resistance in Leishmania: similarities and differences to other organisms.

The main line of defense available against parasitic protozoa is chemotherapy. Drug resistance has emerged however, as a primary obstacle to the successful treatment and control of parasitic diseases. Leishmania spp., the causative agents of leishmaniasis, have served as a useful model for studying mechanisms of drug resistance in vitro. Antimonials and amphotericin B are the first line drugs to treat Leishmania followed by pentamidine and a number of other drugs. Parasites resistant against all these classes of drugs have been selected under laboratory conditions. A multiplicity of resistance mechanisms has been detected, the most prevalent being gene amplification and transport mutations. With the tools now available, it should be possible to elucidate the mechanisms that govern drug resistance in field isolates and develop more effective chemotherapeutic agents.

Journal Article↗
PubMed2006

Molecular technologies in parasitology, with an emphasis on genomic approaches for investigating parasitic nematodes.

In the last years, there have been substantial and rapid technological advances in the areas of genomics and genetics. These advances provide unique opportunities for exploring parasite development and reproduction at the molecular level and offer prospects for developing novel methods for the diagnosis and control of parasitism. The present keynote address illustrates the importance and impact of 'targeted' genomic studies of parasites in the wake of this technological revolution.

Animals↗
PubMed1987

Maternal transmission by Alaria marcianae (Trematoda) and the concept of amphiparatenesis.

The term amphiparatenic host was coined originally for hosts of Alaria marcianae that as adults are paratenic hosts, but as juveniles serve as definitive hosts. In this study the concept of amphiparatenesis is placed in a theoretical context, maternal transmission shown to be the basic mechanism, and the concept extended to include Toxocara canis, T. cati, T. pteropodis, Neoascaris vitulorum, Ancylostoma caninum, Uncinaria lucasi, various species of Strongyloides, Pharyngostomoides procyonis, and P. adenocephala. Alaria marcianae mesocercariae were used in a feline model to show that male and nonlactating female cats are definitive hosts, but lactating cats are primarily paratenic hosts. Inoculation of 1 female cat resulted in the infection of 21 of her offspring via the milk over the course of 5 litters and after a 3-yr period she still had viable larvae in her tissues. The ability of parasites to remain immature in amphiparatenic hosts is believed to be an adaptation on the part of the parasite to promote dissemination through maternal transmission and not the result of resistance, immunological or otherwise, on the part of the host. The amphiparatenic concept has important implications that include: the use of pregnant and lactating females as reservoirs of infection for the offspring; infection transmitted through a contagious transplacental or transmammary pathway; a parasite population structure in which adult worms are in greater abundance in neonate than adult hosts; and the effective control of parasites utilizing this strategy proving to be very difficult.

Animals↗