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PubMed2002

HIV infection and tropical parasitic diseases - deleterious interactions in both directions?

HIV and parasitic infections interact and affect each other mutually. Whereas HIV infection may alter the natural history of parasitic diseases, impede rapid diagnosis or reduce the efficacy of antiparasitic treatment, parasitoses may facilitate the infection with HIV as well as the progression from asymptomatic infection to AIDS. We review data on known interactions for malaria, leishmaniasis, Human African Trypanosomiasis, Chagas' disease, onchocerciasis, lymphatic filariasis, schistosomiasis and intestinal helminthiases. The common immunopathogenetic basis for the deleterious effects parasitic diseases may have on the natural history of HIV infection seems to be a particular type of chronic immune activation and a preferential activation of the T helper (Th)2 type of help. Control of parasitic diseases should complement the tools currently used in combating the HIV pandemic.

Female↗
PubMedDate not supplied

Central venous catheters: infection and patient susceptibility.

Infection is a major cause of morbidity in haemodialysis patients, of which between 25% and 50% of infections are related to vascular access, most commonly central venous catheters (CVCs) (Kessler et al, 1993). The morbidity associated with CVC infection provides a focus for research investigation, as there is limited knowledge available in relation to physiological and psychological parameters that may increase the probability of haemodialysis patients acquiring a CVC-related infection. This study explores these issues and discusses various factors that influence infection. It then describes how organisms which live on and inside our bodies can become parasitic, thus causing an infection. The precautions taken by healthcare professionals to reduce colonization and infection are enumerated, and the value of considering patients' physiological and psychological parameters alongside the more traditional extrinsic infection control approaches is discussed.

Bacterial Infections↗
PubMed1986

The population dynamics and epidemiology of intestinal nematode infections.

The paper reviews recent studies on the population biology, transmission dynamics and epidemiology of intestinal nematode infections. Particular attention is given to patterns of change in average intensity of infection with age, the possible role of acquired immunity assessed via reinfection studies after chemotherapy, evidence of predisposition to heavy (or light) infection by single and multiple species of parasites and control by mass, selective and targetted chemotherapy.

Adolescent↗
PubMed1990

Primary biliary cirrhosis in the mouse: induction by human mycoplasma-like organisms.

Human intraocular and orbital chronic inflammatory disease with autoimmune features has been reported to be caused by mycoplasma-like organisms (MLO). MLO are intracellular cell-wall deficient pathogenic bacteria, closely related to rickettsia, with a characteristic ultrastrural pleomorphic tubulo-spherical and filamentous appearance. No culture system has been developed for MLO and diagnosis of MLO disease is made by detecting these bacteria within infected cells using a transmission electron microscope. In human MLO ocular and orbital disease the organisms are found in parasitized leucocytes at the disease site. Inoculation of human MLO into mouse eyelids produces a high incidence of orbital and introcular disease. MLO disseminate to produce randomly distributed lethal systemic disease with infected leucocytes found in all disease sites and with similar histologic features in all disease sites. Microvasculitis is the initial lesion. Disease progression results in lysis of vascular and parenchymal structures, stromal lymphocytic infiltrates, granulomas, and fibrosis. This report describes the hepatic portal chronic progressive inflammatory disease in 11 of 100 of those mice versus 0 in 200 controls. MLO parasitized portal leucocytes are present in all 11 inflamed livers versus 0 in 5 control livers (P less than 0.05). The resemblance of the animal liver disease induced by MLO to human primary biliary cirrhosis and rifampin treatment of MLO disease are discussed.

Animals↗
PubMed2006

A multicenter evaluation of the effectiveness of Quest Gel (2% moxidectin) against parasites infecting equids.

Controlled trials with a common protocol were conducted in Idaho, Illinois and Tennessee to evaluate anthelmintic effectiveness of Quest Gel (QG; 2% moxidectin) against lumenal parasites in horses. Candidate horses were required to have naturally acquired nematode infections, as confirmed by presence of strongylid eggs in feces. At each site, 24 equids were blocked on the basis of pretreatment strongyle fecal egg counts (EPG) and randomly assigned to treatments within blocks. Within each block of two animals, one received QG on Day 0 at a dosage of 0.4 mg moxidectin/kg b.w. and one was an untreated control. Body weights measured the day before treatment served as the basis for calculating treatment doses. Horses assigned to treatment with QG received the prescribed dose administered orally with the commercially packaged Sure Dial syringe. Horses were necropsied 12-14 days after treatment, and lumenal parasites and digesta were harvested separately from each of five organs, including the stomach, small intestine, cecum, ventral colon and dorsal colon. Parasites from stomachs and small intestines were identified to genus, species and stage. Micro- (i.e., < 1.5 cm) and macroparasites (i.e., > 1.5 cm) in aliquots from the cecum, ventral colon and dorsal colon were examined in aliquots of approximately 200 parasites until at least 600 parasites had been identified to genus, species and stage or until all parasites in the 5% aliquot were examined, whichever occurred first. Data were combined across sites and analyzed by mixed model analysis of variance to assess the fixed effect of treatment and random effects of site and block within site. Because QG does not contain a cestocide, efficacy of QG against tapeworms was not significant (P > 0.05). Based on geometric means, however, efficacy of QG was greater than 90% (P < 0.05) against 38 species and developmental stages of cyathostomes, strongyles, bots, larval pinworms and ascarids encountered in at least 6 of 36 control horses in the combined data set. None of the horses treated with moxidectin exhibited evidence of adverse effects. Study results demonstrate QG, administered to horses with naturally acquired endoparasite infections at a dosage of 0.4 mg moxidectin/kg b.w., was highly effective against a broad range of equine parasitic infections.

Analysis of Variance↗
PubMed2004

Emerging parasitic infections.

Parasitic infections are felt by most individuals to have little impact on the health and well being of most inhabitants of Canada, Western Europe, and the United States. As the authors show in this article, parasites are always "emerging" somewhere and have a significant impact on those areas of the world. Moreover, as we are becoming an ever-smaller global village, catastrophes and instability in the Third World affect control of parasitic diseases endemic to those areas, ensuring greater chances of transmission to visitors there. The foundation of successful limitation of parasitic diseases in both developing and developed regions is still accurate and rapid diagnosis.

Communicable Diseases, Emerging↗
PubMed1999

Humoral response of Meriones libycus to experimental infection with Leishmania major.

The humoral responses of laboratory-reared jirds (Meriones libycus) to inoculation with various doses of Leishmania major were determined. The animals were inoculated intradermally with 10(2), 10(3), 10(5) or 10(7) promastigotes of a strain of L. major originally isolated from a Jordanian patient. The jirds were then bled at various intervals throughout the 26 weeks of the study, and the sera checked, by IFAT, for antibodies to homologous parasites. There were no detectable humoral responses in the animals inoculated with 10(2) promastigotes each or in parasite-free controls but a positive response was apparent in each of the other jirds. The animals given 10(3) promastigotes each required 3 months to become IFAT-positive whereas those given 10(5) and 10(7) parasites only needed 4 and 2 weeks, respectively. More than 50% of the animals inoculated with 10(3) parasites each developed strongly positive sera 2 months post-infection, whereas > 50% of the animals inoculated with 10(5) or 10(7) parasites each had strongly or very strongly positive sera 4 and 2 weeks post-inoculation, respectively. The data indicate that, in M. libycus inoculated with L. major, the time required for the humoral response to develop and its intensity are both dose-related.

Animals↗
PubMed1998

Schistosomiasis control in Brazil.

In 1975 the Special Programme for Schistosomiasis Control was introduced in Brazil with the objective of controlling this parasitic disease in six northeastern states. The methodology applied varied largely from state to state, but was based mainly on chemotherapy, This Programme was modified about ten years after it beginning with the main goals including control of morbidity and the blockage of establishment of new foci in non-endemic areas. In two states, Bahia and Minas Gerais, the schistosomiasis control programme started in 1979 and 1983, respectively. The recently made evaluation of those two programmes is the main focus of this paper. It must also be pointed out, that the great majority of the studies performed by different researchers in Brazil, at different endemic areas, consistently found significant decrease on prevalence and incidence, when control measures are repeatedly used for several years. Significant decrease of hepatosplenic forms in the studied areas is well documented in Brazil. After more than 20 years of schistosomiasis control programmes in our country, chemotherapy has shown to be a very important tool for the control of morbidity and to decrease prevalence and incidence in endemic areas. Nevertheless, in medium and long terms, sanitation, water supply, sewage draining and health education seem to be the real tools when the aim is persistent and definitive schistosomiasis control.

Brazil↗
PubMed1996

Effects of formalin, chloramine-T, and low salinity dip on the behavior and hemolymph biochemistry of the American lobster.

The purpose of this research was to investigate the salinity and formalin sensitivity of a ciliate parasite (Anophryoides haemophila) of the American lobster (Homarus americanus), and to examine the target-animal (lobster) safety of chemical-bath treatments involving low salinity, formalin, or chloramine-T that could be used to control this parasite in lobster pounds. "Bumper car" disease, caused by An. haemophila, is an important concern to lobster pound operators in eastern North America, because of the implicated lobster mortality rate and the general lack of preventive and therapeutic intervention regimes. We determined, using an in vitro method, that formalin at 50 mg/L, or low salinity at 8.0 parts per thousand (ppt) for 1 hour killed 100% of the parasites. When healthy lobsters were exposed to formalin at 200 mg/L, there were no negative behavioral responses and no significant differences in a panel of hemolymph biochemical indices. Similar results occurred when lobsters were exposed to chloramine-T, a common finfish therapeutic agent for topical bacteria and protozoa, at 10 mg/L for 1 hour. The low salinity treatment (8.0 ppt) resulted in significant adverse changes in lobster behavior and biochemical indices; however, these changes did not persist for more than 1 week after treatment ended. Although these treatments are unlikely to kill parasites that have already invaded the lobster carapace, they should be effective in reducing parasite loads on the gill and carapace surface of the lobster and in the environment of the impoundment housing.

Animals↗
PubMed1987

Evaluation of the parasitological and production responses of a cow/calf operation to an anthelmintic program with ivermectin.

The efficacy of a treatment schedule using ivermectin, given subcutaneously at the rate of 200 micrograms kg-1, to control gastrointestinal parasitism and its effect on liveweight gains was assessed. Two herds with a total of 466 Hereford X Brangus cow/calf pairs were used. Each herd was on six pasture plots of comparable size, stocking rate, and quality and quantity of forage. Pasture groups were paired across the two herds. Pasture groups from one herd were randomly assigned to nonmedicated control and the other three to ivermectin treatment. Treatment assignments per pasture group were reversed in the other herd. The control group contained 118 cows and 112 calves and the medicated group 121 cows and 115 calves. Cows were treated in early July and the calves in late July or early August. Cattle from one herd were weighed on Days -28, 0 (day of cow treatment), 30 (day of calf treatment), 58, and 86, while the other herd was weighed on Days -29, 0 (day of cow treatment), 27 (day of calf treatment), 61, and 89. Day 0 was not the same calendar day for the two herds. Fecal samples for parasite egg counts were obtained from the rectum on weight days from five cows and six calves from each pasture; in most cases the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves between day of treatment for cows and the end of the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Experimental visceral leishmaniasis: production of interleukin 2 and interferon-gamma, tissue immune reaction, and response to treatment with interleukin 2 and interferon-gamma.

During the first 2 to 4 weeks of progressive visceral infection with the intracellular protozoan, Leishmania donovani, spleen cells from BALB/c mice failed in response to leishmanial antigen to produce either of the activating T cell-derived lymphokines, interleukin 2 (IL 2) or gamma-interferon (IFN-gamma). Four weeks after infection, however, antigen-induced IL 2 and IFN-gamma secretion emerged and coincided with the onset of control over parasite replication and the subsequent killing of greater than 80% of intrahepatic L. donovani. The development of this immunosecretory activity correlated with the hepatic tissue response at the site of parasitized Kupffer cells. This response progressed from Kupffer cell fusion (week 1) to fusion plus a mononuclear cell infiltrate (week 2) to well-organized granuloma formation (weeks 4 to 8). In contrast, T cell-deficient nude BALB/c mice exerted no control over L. donovani, their spleen cells failed to generate antigen-induced IFN-gamma, and at 4 weeks, their livers were devoid of any tissue reaction. Since spleen cells from 2-week infected normal mice did not produce antigen-stimulated IL 2 or IFN-gamma, these mice were treated with recombinant (r) lymphokines. Various protocols using both high and low dose human rIL 2 had no antileishmanial effect. Hepatic parasite replication was completely halted, however, by macrophage-activating doses of murine rIFN-gamma. These results reemphasize that an intact T cell-dependent response is required for successful defense against L. donovani, indicate that this immune response can be measured at both the cellular (secretory) and tissue levels, and confirm that IFN-gamma can exert an antileishmanial effect in vivo.

Animals↗
PubMed2004

Efficacy and pharmacokinetics of intravenous nanocapsule formulations of halofantrine in Plasmodium berghei-infected mice.

The efficacy and pharmacokinetics of a new parenteral formulation of halofantrine were studied in mice infected with Plasmodium berghei. The formulation consisted of nanocapsules with an oily core, prepared from either poly(D,L-lactide) (PLA) homopolymer or PLA that was surface modified with grafted polyethylene glycol chains. They were compared with a previously described intravenous halofantrine preparation. No toxic effects were observed with halofantrine in form of nanocapsules after intravenous administration for doses of up to 100 mg/kg, whereas the solubilized form in polyethylene glycol-dimethylacetamide was toxic at this dose. The halofantrine-loaded nanocapsules showed activity that was similar to or better than that of the solution in the 4-day test and as a single dose in severely infected mice, with only minimal differences between the two nanocapsule formulations. Halofantrine pharmacokinetics were determined in parallel with parasite development in severely infected mice. Nanocapsules increased the area under the curve for halofantrine in plasma more than sixfold compared with the solution throughout the experimental period of 70 h. Furthermore, nanocapsules induced a significantly faster control of parasite development than the solution in the first 48 h posttreatment. While the parasitemia fell more rapidly with PLA nanocapsules, the effect was more sustained with the surface-modified ones. This is consistent with surface-modified nanocapsules remaining longer in the circulation. These results suggest that nanocapsule formulations could provide a more favorable halofantrine profile in the plasma and reduce the intravenous dose necessary and therefore the toxicity, thus suggesting the use of halofantrine by a parenteral route in severe malaria.

Animals↗
PubMed1995

Natural resistance to infection with intracellular parasites: molecular genetics identifies Nramp1 as the Bcg/Ity/Lsh locus.

Natural resistance to infection with intracellular parasites is controlled in the mouse by the expression of a locus or group of loci on chromosome 1 alternatively named Bcg, Lsh, and Ity. Bcg affects the capacity of mature tissue macrophages to restrict the intracellular proliferation of ingested parasites in the reticuloendothelial organs of the host during the early phase of infection. This review summarizes our molecular genetic approach to the isolation and characterization of the Bcg locus. We have used a positional cloning strategy based on genetic and physical mapping, YAC cloning, and exon trapping to isolate a candidate gene for Bcg, named Nramp1, which codes for a macrophage-specific polytopic protein with 12 predicted transmembrane domains and a consensus transport motif. Sequence analysis of Nramp1 cDNA clones from 27 Bcgs and Bcgr mouse strains reveals that susceptibility to infection (Bcgs) is associated with a single nonconservative Gly to Asp substitution at position 169 within predicted transmembrane domain 4 of the Nramp protein. Cloning experiments and homology search in available databases demonstrated that the Nramp1 gene belongs to a small gene family with several members in vertebrates and in such distantly related species as yeast and plants. Nramp proteins share a remarkable degree of similarity, with strong amino acid sequence conservation in the transmembrane domains, suggesting a common transport function for the Nramp family. Finally, we generated Nramp1-/- gene knockout mice, and analysis of their phenotypic characteristics established that (1) Nramp1 plays a key role in natural defense against infection with intracellular parasites and therefore demonstrated allelism between Nramp1 and Bcg/Ity/Lsh, (2) Nramp1 functions by a novel cytocidal/cytostatic mechanism distinct from those expressed by the activated macrophage, and (3) the Nramp1Asp169 allele of Bcgs inbred strains is a null allele, pointing to a critical role of this residue in Nramp1 function.

Animals↗
PubMed2004

Innate and acquired immunity in the pathogenesis of Chagas disease.

The apparent discrepancy between the intensity of inflammatory reaction and scarce number of parasites in chronic chagasic myocarditis prompt several investigators to hypothesize that an autoimmune process was involved in the pathogenesis of Chagas disease. Here, we recapitulate diverse molecular and cellular mechanisms of innate and acquired immunity involved in the control of parasite replication and in the build up of myocarditis observed during infection with Trypanosoma cruzi. In addition, we review the immunoregulatory mechanisms responsible for preventing excessive immune response elicited by this protozoan parasite. Ongoing studies in this research area may provide novel therapeutic strategies that could enhance the immunoprotective response while preventing the deleterious parasite-elicited responses observed during Chagas disease.

Animals↗
PubMed1999

Virulence and transmission success of the malarial parasite Plasmodium falciparum.

Virulence of Plasmodium falciparum is associated with the expression of variant surface antigens designated PfEMP1 (P. falciparum erythrocyte membrane protein 1) that are encoded by a family of var genes. Data presented show that the transmission stages of P. falciparum also express PfEMP1 variants. Virulence in this host-parasite system can be considered a variable outcome of optimizing the production of sexual transmission stages from the population of disease-inducing asexual stages. Immunity to PfEMP1 will contribute to the regulation of this trade-off by controlling the parasite population with potential to produce mature transmission stages.

Animals↗