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At least 991 records · Page 55Linked to original sources
PubMed1989

Chemotherapy of fish parasites.

There are few agents on the market that control fish parasites. These are substances that are mainly used in other hosts; due to the different metabolism of fish, they often have only moderate effects on fish parasites. Therefore, the research and development of fish-specific antiparasitic compounds is needed to avoid the high losses suffered by commercial fish hatcheries. Drugs similar to toltrazuril would perhaps be promising, due to their broad spectrum of efficacy.

Animals↗
PubMed2000

The cell cycle in protozoan parasites.

Research into cell cycle control in protozoan parasites, which are responsible for major public health problems in the developing world, has been hampered by the difficulties in performing classical genetic analysis with these organisms. Nevertheless, in a large part thanks to the data gathered in other eukaryotic systems and to the acquisition of the sequences of parasite genes homologous to cell cycle regulators, many molecular tools required for an in-depth study of the cell cycle in protozoan parasites have been collected over the past few years. Despite the considerable phylogenetic divergence between these organisms and other eukaryotes, and notwithstanding important specificities such as the apparent lack of checkpoints during cell cycle progression, available data indicate that the major families of cell cycle regulators appear to operate in protozoan parasites. Functional studies are now needed to define the precise role of these regulators in the life cycle of the parasites, and to possibly validate cell cycle control elements as potential targets for chemotherapy.

Animals↗
PubMed1982

Structuring information systems for more effective disease control programs.

The design of effective health programs involves a complex set of information flows needed to support the planning, implementation, and evaluation of alternative intervention strategies. While several information system models are available, few have actually been applied to specific disease cycles. The objective of this paper is to consider the design of information systems in terms of organizational contextual factors and user/decision-maker preferences relevant to the structure and operation of such information systems. A heuristic procedure is developed and applied to the design of information systems responsible for supporting effective parasitic disease control efforts. Recent research based on this application indicates substantial technical advantages to an intersectoral, multidimensional approach to parasitic disease control. In particular, analysis reveals that information system designs can significantly enhance the effectiveness of disease intervention through a higher level of sensitivity to such factors as disease etiology, socioeconomic conditions, and population health beliefs and perceptions.

Communicable Disease Control↗
PubMed1997

Role of macrophages in experimental malaria: IV--Bioassay of silica in immunity against Plasmodium berghei infection.

Silica treated mice when challenged with Plasmodium berghei showed increase in duration of prepatent(PP) and survival period (SP) and median survival day(MSD) as compared with controls. Daily parasite density curve during the course of infection was similar to control. Response to the parasite challenge, however, was dependent on the dose of silica. No increase in SP at 0.7 mg and in PP at 35 mg (cumulative doses) dose was observed. A dose upto 5 mg per mouse before challenge resulted in protection of the animal. No mortality was recorded in mice which received silica alone (35 mg; 5 mg/day x 7 days). Death due to lethal P.berghei infection could be delayed or prevented by altering/reducing the functional activities of macrophages during the course of infection.

Animals↗
PubMed1998

Trypanotolerance, an option for sustainable livestock production in areas at risk from trypanosomosis.

Trypanosomosis is one of the major constraints on animal production in areas of Africa which have the greatest potential for significant increases in domestic livestock populations and livestock productivity. While the eradication of trypanosomosis from the entire continent is an unrealistic goal, considerable effort has been invested in the control of this disease through the use of trypanocidal drugs, management of the vector and exploitation of the genetic resistance exhibited by indigenous breeds. There is little hope that a conventional, anti-infection vaccine will be produced in the near future. Drug resistance is developing faster than generally thought. The control of the tsetse fly has been attempted over many decades. The decreasing efficacy of available trypanocidal drugs and the difficulties of sustaining tsetse control increase the imperative need to enhance trypanotolerance through selective breeding, either within breeds or through cross-breeding. Trypanotolerance has been defined as the relative capacity of an animal to control the development of the parasites and to limit their pathological effects, the most prominent of which is anaemia. A major constraint on selection for trypanotolerance in cattle, for both within-breed and cross-breeding programmes, has been the absence of practical reliable markers of resistance or susceptibility. Distinct humoral immune response to trypanosome infection is the major feature of bovine trypanotolerance. The role that these responses play in the control of infection or disease is being addressed by ongoing research, but remains a matter of speculation at present. Results in recent years have shown that packed cell volume (PCV) in particular and parasitaemia, the two principal indicators of trypanotolerance, are strongly correlated to animal performance. However, although direct effects of trypanosome infections on PCV and growth are obvious, more sensitive diagnostic methods for reflecting parasite control are required so that individual animals can be categorised reliably for their parasite control capability. One key finding is the major contribution made by each of the indicators evaluated to the overall trypanotolerance variance. Preliminary genetic parameters for PCV provide evidence that trypanotolerance is not only a breed characteristic but is also a heritable trait within the N'Dama population; this brings new opportunities for improved productivity through selection for trypanotolerance. More reliable estimation of genetic parameters of the indicators may well show that these parameters must be handled simultaneously for optimal progress. This would require diagnostics for assessing parasite control capability that identify trypanosome species more accurately, especially in mixed infections. A major advantage of trypanotolerant livestock, particularly N'Dama cattle, is the resistance or adaptation of this breed to many of the important pathogenes which prevail in the sub-humid and humid tropics. Research on practical indicators of resistance to these conditions will be required to establish relevant integrated strategies based on disease-resistant livestock. Selective breeding will require the integration of the traits that farmers hold important for their production systems.

Africa↗
PubMed2000

Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana.

The effectiveness of Duddingtonia flagrans in reducing the free living third stage larvae (L(3)) of equine cyathostomes on pasture when fed to horses has been demonstrated in cold temperate climates. The objective of this experiment was to assess the efficacy of D. flagrans against equine cyathostomes in the subtropical environment of southern Louisiana. Fecal pats were prepared by mixing feces obtained from a parasite-free horse fed D. flagrans at a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cyathostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fecal pats were placed on pasture in six replicates at 4-week intervals from March 1997 until January 1998. Comparison of recoveries of L(3) from non-treated control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L(3) survival on pasture was reduced during the months of May, June, July, August and September. The efficacy of the fungus was determined by L(3) recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L(3) during the months of April, May, and October 1997 to January 1998 (range 66-99% reduction, p=0.0001), and for the year as a whole (p=0.0001).

Animals↗
PubMed1993

Suppression by dietary alcohol of resistance to Cryptosporidium during murine acquired immune deficiency syndrome.

Significant immunological changes occur following LP-BM5 murine leukemia retrovirus infection as well as chronic alcohol consumption. Retrovirus infection which has proceeded to murine AIDS permitted persistent Cryptosporidium infection, while non-retrovirus infected mice were resistant. Dietary alcohol provided until the day before parasite challenge did not affect resistance in controls, but increased the numbers of oocysts in the feces of retrovirus suppressed mice. Mortality was significant in retrovirus infected mice, and exacerbated slightly by dietary ethanol, while all controls survived parasite challenge. The retrovirus infected mice had greatly reduced numbers of intestinal CD4+ T helper cells and IgA+ B cells, which may explain their loss of intestinal resistance. Clearly, the severely immunosuppressed animals with murine AIDS were more sensitive to alcohol consumption than uninfected controls. This suggests that alcohol can synergize with murine retrovirus infection to exacerbate loss of resistance to an opportunistic pathogen common in human AIDS patients.

Animals↗
PubMed1998

Eradication of schistosomiasis in Guangxi, China. Part 1: Setting, strategies, operations, and outcomes, 1953-92.

Reported are the results of an analysis of a 40-year programme leading to eradication of schistosomiasis in Guangxi, China, a large, poor autonomous region of the country that had the heaviest global burden of the disease. We used historical county data and maps showing the initial distribution and density of Oncomelania snails and the initial prevalence of schistosomiasis to assess the correlation between snail occurrence and human infection. All annual county schistosomiasis reports were collected and analysed, including information on snail abundance and infection, human and animal infection control, stool examinations and patient treatments, clinical and serology examinations, skin test surveillance, patient follow-up, patient treatments, animal examinations, water supply and sanitation, and environmental modification. The findings bear witness to the laborious, systematic and scientific basis of the control programme and how it changed over the 40 years. Of note is the continual search for and treatment of cases, the killing of snails, and the permanent alteration of their habitats using mass community participation and methods adapted to local conditions. The programme has freed more than 10 million people from the risk of schistosomiasis and boosted rural economic development and health. The persistence, good record keeping, evolving and locally flexible strategies, and the clear focus of the control programme were crucial to its eventual success.

Animals↗
PubMed1995

The impact of control measures on urinary schistosomiasis in primary school children in northern Cameroon: a unique opportunity for controlled observations.

As part of a program to integrate schistosomiasis control into the primary health care system in northern Cameroon, an unexpected opportunity to undertake a controlled evaluation of the impact of interventions was recognized. Inadvertently, a large part of Mindjil, one of four assessment villages, had been essentially excluded from the program, creating a unique natural control. The prevalence of infection with Schistosoma hematobium in school-aged children was 7% in the areas where the control program was implemented, and 71% in the excluded areas (P < 0.0002). High intensity infection was 1% and 26% in the two areas, respectively (P < 0.0002). Children in the school where the control interventions were implemented had a significantly lower prevalence of infection with Schistosoma hematobium (P < 0.005). Subjects in intervention areas demonstrated greater knowledge about the transmission of schistosomiasis than those in the control area. This study documented and quantified program impact in a controlled manner not usually possible in field studies and also illustrated how unrecognized intracultural diversity (within culture differences) in target populations may effect disease control programs in communities.

Adolescent↗
PubMed1999

Agricultural policy and sustainable livestock development.

Future agricultural and rural development is, to a large extent, influenced by the projected food needs of 2.5 billion people expected to swell the world population by 2020. This increase will require more food in general and, in view of recent experience in East Asia, more animal products. To achieve this increase will require judicious use of resources, and trade, especially in those countries where natural resources are insufficient to support food production. Achieving food sufficiency in a sustainable manner is a major challenge for farmers, agro-industries, researchers and governments. The latter play an important role as many of the farmers' choices are, to a large extent, directed by government or supra-government, often through macro- and micro-economic policy. In many countries the economic, environmental, trade and agricultural policies have not been conducive to an agricultural development that is risk-free with respect to the environment, animal welfare or public health. The recent decline of government support in agriculture forced farmers in Western countries to think about more risk adverse agricultural practices and more efficient production systems. On the other hand, many countries in Eastern Europe and the former Soviet Union, as well as other developing countries, are still going through a painful process of adjustment to new market conditions. International banks and development agencies have a mandate to help developing countries, but are somewhat restricted both by needing to work directly with governments and by their perceived dogmatic approach to development. Changing policies do, now and in the future, also affect the development of animal disease control programmes, including the control of parasitic diseases. On the one hand there is an increasing interest in risk-free control practices, and on the other hand a demand for greater regulatory control over the production process. As parasitic diseases of animals are closely linked to the environment (i.e. grazing and waste management) and public health (i.e. parasitic zoonoses), the new interest in sustainable agriculture provides a challenge for those concerned with the control and prevention of animal parasitism.

Agriculture↗
PubMed1991

The use of monoclonal antibody-based ELISAs to monitor the efficacy of drugs against male Onchocerca gibsoni in vitro.

Four monoclonal antibodies directed against antigens of Onchocerca gibsoni were used in antigen detection ELISAs to monitor the efficacy of CGP 20309, CGP 20376, CGP 21833, CGP 24589 and CGP 26702 at 5 micrograms/ml against male O. gibsoni in vitro. No significant differences (P less than 0.05) in antigen output between treated and control groups of parasites were recorded. However, consistently higher levels of antigen from treated (CGP 21833) as compared to control parasites were measured with all four assays, with differences being higher in the first 2 to 3 days post treatment than subsequently. The sensitivity of comparisons between groups was reduced by the high variability in output of antigen both between worms and also from the same worm, in part as a result of mechanical damage to worms sustained during collection or manipulation in vitro. This problem was reduced by zero handling once worms were established in vitro and it is recommended that future work should include a 24 to 48 hour period before treatment commences to detect raised antigen levels associated with physically damaged parasites so they can be excluded. It was concluded that this type of assay has no intrinsic technical or logistical advantage over other published methods of assessing drug-related damage in in vitro filarial screens. Nevertheless, further work using antigen detection ELISAs in this context is justified since these assays, unlike all other methods of assessing drug-induced damage in vitro, have direct application for use in identifying chemotherapeutic effects against similar parasites in vivo.

Animals↗
PubMed1996

Finding genetic markers for complex phenotypic traits in parasites.

The identification, mapping and eventual cloning of genes which determine or influence important epidemiological traits in parasites can have great benefits for the control of parasitic disease. In this review, strategies are outlined for identifying genetic markers for complex, quantitative traits. A genetic marker is a variable DNA sequence which co-occurs with a variable quantitative trait. Candidate markers are chosen because they are thought to directly influence the trait whereas random markers are expected to be linked to another DNA sequence which influences the trait. Association studies compare the value of a quantitative trait between different marker genotype classes in a population, without regard to family structure. Linkage studies compare the value of a quantitative trait between marker genotype classes within families or within a population (usually derived from a cross between inbred lines) which is segregating for both marker and quantitative trait loci. The most commonly used analytical methods for determining the significance of association or linkage between marker and quantitative trait loci, and for estimating parameters such as recombination rate and quantitative gene action, are least-squares and maximum likelihood. Both methods may be used to test either single markers or the interval between flanking markers, and both suffer from the need to minimize type I and type II error rates with multiple tests.

Animals↗
PubMed2006

Skin mast cells control T cell-dependent host defense in Leishmania major infections.

Mast cells (MCs) initiate protective immunity against bacteria. Here we demonstrate that MCs also contribute to the control of parasitic skin infections by Leishmania major. L. major-infected MC-deficient Kit(W)/Kit(W-v) mice developed markedly larger skin lesions than did normal Kit+/+ mice (>2-fold), and cutaneous reconstitution with MCs resulted in normalization of lesion development. Kit(W)/Kit(W-v) lesions contained significantly more parasites, and infections resulted in enhanced spreading of parasites to the spleens as compared to controls. In addition, recruitment of proinflammatory neutrophils, macrophages, and dendritic cells (DCs) in infected mice was MC dependent. In the absence of MCs, reduced numbers of lesional DCs were associated with decreased production of Th1-promoting interleukin (IL)-12. Antigen-specific T cell priming was delayed in Kit(W)/Kit(W-v) mice and cytokine responses were skewed towards Th2. Notably, local skin MC reconstitution at sites of infection was sufficient for the induction of systemic protection. Thus, MC-mediated control of L. major infections is not limited to the induction of local inflammation. Instead, MCs contribute significantly to local DC recruitment, which mediates protective immunity. These findings extend the view of MCs as salient sentinels of innate immunity to complex host defense reactions against intracellular pathogens.

Animals↗