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At least 937 records · Page 52Linked to original sources
PubMed1998

Developmental switching in the parasitic nematode Strongyloides stercoralis is controlled by the ASF and ASI amphidial neurons.

Parasitic nematodes of the genus Strongyloides are remarkable for their ability to switch between alternative free-living developmental pathways in response to changing internal environmental conditions. After exiting the host, soil-dwelling larval stages may develop either to infectivity via 2 microbiverous stages (homogonic development) or to free-living adulthood via 4 microbiverous larval stages (heterogonic development). The progeny of these adults then give rise to the infective stage. In the latter case, free-living existence is extended in time and the number of infective larvae is greatly amplified. Anterior chemosensory neurons (amphidial neurons) are thought to respond to environmental cues and via signal transduction pathways control the direction of larval development. We now demonstrate by laser microbeam ablation that 2 classes of amphidial neurons (ASF and ASI), acting together, control the direction of free-living larval development. Larvae in which the neurons were killed developed to infectivity via the homogonic route rather than to adulthood via the otherwise predominant heterogonic route. These neurons are probable homologues of neurons ADF (=ASF) and ASI in Caenorhabditis elegans, suggesting the control of development at the cellular level is conserved among divergent taxa of nematodes. These observations also have important implications for the evolution of nematode parasitism and the design of new prophylactic measures against parasitic nematodes of medical and veterinary medical importance.

Animals↗
PubMed1995

Eradication of dracunculiasis from Pakistan.

In 1986 the World Health Organization targeted dracunculiasis (Guinea-worm disease), which seriously impairs socioeconomic development in 16 African countries, India, Pakistan, and Yemen, to be eradicated globally. The target date for eradication by the end of 1995 was established in 1991. Pakistan eradicated dracunculiasis from the country in October, 1993, after a national campaign which began in 1987 with a nationwide village-by-village search for cases. The infection, which is transmitted by drinking water from ponds containing infected water fleas, was eradicated by using health education, cloth filters, and the cyclopsicide, temephos; and in the later stages, by case containment. Methods pioneered in Pakistan's National Guinea Worm Eradication Program are now being applied in remaining endemic countries.

Communicable Disease Control↗
PubMed1991

Residues of organochlorine pesticides in human milk from mothers living in the greater Harare area of Zimbabwe.

Residue levels of the chlorinated hydrocarbons p,p -DDT, p,p, -DDE, p,p TDE, p,p -DDT, alpha-beta-gamma-hexachlorocyclohexane (HCH), heptachlor epoxide, dieldrin and polychlorinated biphenyls (PCBs) were determined in human milk of 40 Zimbabwean mothers living in the greater Harare area. Three municipal clinics and one main hospital were randomly selected as collecting points. The main organochlorine contaminants found in all the samples analysed were p,p -DDT and p,p -DDE and the mean levels of sum DDT and DDT/DDE ratio were 6 mg/kg milk fat and 0.74 respectively. In general, relatively low residue levels of alpha-beta-,gamma-HCH, heptachlorepoxide and dieldrin were detected in 58,100,63,13 and 65pc, respectively of all the milk samples analysed. Trace of the PCB congener 2,2,4,5,5'-pentachlorobiphenyl (PCB 101) were found in 15 samples and only one sample contained traces of 2,3',4,4',5-pentachlorobiphenyl (PCB 118). The results were examined with regard to health ad living condition of the mothers. From the small population observed around the greater Harare area--social status, educational background an living conditions could be described as important demographic variables influencing the frequency distribution of residual levels of sum DDT in the mother's milk.

Educational Status↗
PubMed1994

Schistosomiasis control in China.

Well-organized programmes combining local involvement and major government projects have been successful in controlling schistosomiasis to a large extent in China. The task is far from complete, however, especially in some lacustrine and mountainous areas, where conditions are highly favourable for the vector snails, and difficult to modify. A long-term programme of health education, medical care and infrastructure development is needed.

Animals↗
PubMed2001

Genomic tools to improve parasite resistance.

The natural genetic variability of the ruminant immune system provides a feasible means to control gastrointestinal (GI) parasite infection without anthelmintics. However, the paradigm of traditional selection has not been effectively applied to the moderately heritable traits of parasite resistance (h approximately equal to 0.3) due to the difficulty and expense of gathering accurate phenotypes in a commercial production setting. These characteristics make host traits related to GI nematode infection ideal candidates for genomics-based research. To initiate explanation of important allelic differences, economic trait loci (ETL) are being identified and mapped using a resource population of Angus cattle segregating for GI nematode resistance and susceptibility to the two most common nematode parasites of US cattle, Ostertagia ostertagi and Cooperia oncophora. The population is composed of five generations of half-sib progeny with complete phenotypic records produced from controlled infections. To detect the genomic locations of the three distinct phenotypic traits being expressed (innately immune, acquired immune, and immunologically non-responsive), genotypes have been generated for DNA markers (N=199) spaced at regular intervals (approximately 20cm intervals) throughout the entire genome (3000cm). Although initial ETL detection may be limited by half-sib family size, the unique structure of this population provides additional statistical power for refining map position of potential ETL. After allele frequency and contribution to phenotype are determined in this population, marker tests associated with ETL most beneficial for controlling parasite infection can be accurately used for selection. Comparative map and functional genomic information from humans and other species of biomedical importance will be utilized in further investigations to elucidate the genes underlying ETL.

Animals↗
PubMed1994

A kala-azar control programme for remote tribal communities.

Indigenous people have been trained to provide a culturally appropriate kala-azar control programme for the tribal population of Sahibganj, Bihar, India. Cultural resistance to modern medicine has been overcome and the influence of village witch-doctors has been countered.

Animals↗
PubMed1987

Demonstration and partial characterization of parasite-specific immunoglobulin A responses in human strongyloidiasis.

By using an enzyme-linked immunosorbent assay, serum immunoglobulin A (IgA) responses directed against Strongyloides stercoralis larvae antigens were measured in 104 presumably immunocompetent individuals with chronic uncomplicated strongyloidiasis and in 15 immunocompromised patients with S. stercoralis infection. Fifty healthy North American adults and 18 patients with other helminthic parasites served as controls. All 50 healthy controls were negative for antibody responses (mean absorbance +/- standard deviation = 0.0724 +/- 0.040). The mean absorbance of the 18 parasitized controls was 0.230 +/- 0.087; two individuals parasitized by Ascaris lumbricoides showed positive antibody responses. The mean absorbance of the immunocompetent patients with strongyloidiasis was 0.680 +/- 0.364, with 91 subjects (87.5%) having a positive value (greater than 0.300). Of the immunocompromised patients (mean absorbance +/- standard deviation = 0.735 +/- 0.538), 11 (73%) had a positive antibody response test. When the IgA responses of these two groups were compared, they were not significantly different. There was no correlation between the levels of total serum IgA and the concentration of specific IgA in the infected patients. Both IgA and IgG immunoreactive bands were detected on immunoblots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated larval antigen protein blots. Nineteen bands were recognized by IgG, and 13 were recognized by IgA from sera of infected patients. Several bands displayed specific IgG or IgA reactivity. The present work shows that most patients with strongyloidiasis mount specific IgA responses against filariform larval antigens. These responses are, for the most part, directed against antigens that are different from those recognized by IgG. The lack of correlation between the magnitude of the specific serum IgA responses and the clinical aspects of the infection suggests that these antibodies may not play a central role in the regulation of this parasitosis.

Antibody Specificity↗
PubMed1992

Insecticide-impregnated bed nets for malaria control: a review of the field trials.

Insecticide-impregnated bed nets act as a physical barrier to repel and kill mosquitos. Community intervention trials suggest that these nets are effective in preventing malaria-related mortality and morbidity--but not malaria infection--in areas of low and moderate transmission; the results from areas of high transmission are not so encouraging. Comparison of the results from these trials and their interpretation are difficult because of variations in the epidemiology of malaria and several methodological flaws. Problems such as defining appropriate health indicators, monitoring bed-net usage, introducing bed nets randomly, selecting adequate controls, performing statistical analysis, and comparing bed nets with other available interventions are considered. Further community intervention trials are needed, paying attention to the methods and to assessment of their impact on malaria.

Animals↗
PubMedDate not supplied

Epidemiology and detection as options for control of viral and parasitic foodborne disease.

Human enteric viruses and protozoal parasites are important causes of emerging food and waterborne disease. Epidemiologic investigation and detection of the agents in clinical, food, and water specimens, which are traditionally used to establish the cause of disease outbreaks, are either cumbersome, expensive, and frequently unavailable or unattempted for the important food and waterborne enteric viruses and protozoa. However, the recent introduction of regulatory testing mandates, alternative testing strategies, and increased epidemiologic surveillance for food and waterborne disease should significantly improve the ability to detect and control these agents. We discuss new methods of investigating foodborne viral and parasitic disease and the future of these methods in recognizing, identifying, and controlling disease agents.

Animals↗
PubMed1997

Successful control of onchocerciasis vectors in San Vicente Pacaya, Guatemala, 1984-1989.

Between 1984 and 1989, the onchocerciasis-vector control zone on the pilot area of San Vicente Pacaya, Guatemala, which had been subject to experimental control since 1979, was extended from 91.3 to 148.6 km2. Temephos was used as a larvicide against Simulium ochraceum s.l. the target species. As a new strategy, only breeding sites with water discharges of 0.1-10 litres/s were treated, every 2 weeks. This approach provided a substantial reduction in effort, number of treated sites, time and cost. To assess the effect of the temephos, nine sites were selected in which standardized collections of adult Simulium were made twice a month, by human bait. There was an obvious difference between the pre- and post-control mean densities of flies at each site. In the northern area, which includes the Lavaderos, Barretal, Colina and Rodeo sites, the biting density in 1979, before treatment, varied between 10 and 64 flies/man-hour (FMH). Four years later, this had been reduced to 0.1-3.2 FMH, and by the end of the present study, in 1989, the mean density was zero FMH. In the southern area, which lies south-east of Lavaderos (and includes Guachipilin, Ingerto, Pena Blanca and Sierra Morena), the density during the pre-control phase was 24 FMH at one of the two sites investigated at the time and 39.3 FMH at the other. It fell to 0.1-0.5 FMH after 5 years of control and to zero (three sites) or close to zero (< or = 0.5 FMH; one site) for the last 4 years of the present study. To assess the effect of vector control on onchocerciasis prevalence and incidence, 1280 residents from six endemic communities, out of 12,000 permanent inhabitants, were examined. In Santa Cruz, Patrocinio and Los Rios, the prevalence of skin microfilariae in the subjects from each community fell from 8.1%-37.8% during the pretreatment, base-line period to 0.0%-31.5% when the study foci were totally integrated into the vector-control operation following treatment. Incidence among children (aged < or = 9 years) varied from 0%-25% for the period 1982-1984 but, thereafter, not a single case appeared in four of the six study communities (Santa Cruz, Patrocinio, Los Rios and Berlin). Incidence in Guachipilin did not decline appreciably, probably because of human migration into the area from other onchocerciasis foci. The prevalence of nodules followed a similar trend to those of the prevalence and incidence of skin microfilariae, falling from 9.1%-45.0% pre-control to 1.8%-14.3% 10 years later.

Animals↗
PubMed1997

An attempt to control lungworm disease and parasitic gastroenteritis on commercial dairy farms by the use of an adaptation of Michel's dose-and-move system.

On seven dairy farms an attempt was made to control lungworm disease in calves by turnout on a pasture grazed earlier by cows, followed by a move to aftermath and ivermectin treatment 2 months later. Transmission of lungworm was observed on all farms. Lungworm disease occurred on four farms at treatment. Coughing re-occurred on three of these farms in some animals 2 months later. Owing to poor performance between turnout and treatment, weight gain was below the norm on the farm with the highest infections and most severe respiratory signs. On the other farms respiratory signs did not result in poor weight gain. Gastrointestinal nematode infections remained low on all farms. The conclusion is that this dose and move scheme cannot be recommended for the control of lungworm.

Animals↗
PubMed2001

The epidemiology of nematode infections of sheep.

Nematode parasites have been a major factor limiting sheep production in New Zealand for more than 100 years. Twenty-nine species of nematodes were unintentionally introduced with sheep into New Zealand, but it is principally species of Haemonchus, Ostertagia, Trichostrongylus, Nematodirus and Cooperia that are associated with production losses and clinical disease. The seasonal dynamics of nematode infection are the consequence of complex inter-relationships between the sheep, their husbandry and the prevailing climate. The patterns of pasture contamination by nematode eggs and then larvae and the subsequent levels of infection in ewes and lambs are broadly similar throughout New Zealand. Numbers of infective larvae on pasture build up over summer to a peak in autumn/early winter with, in some years, a spring peak derived from the parturient rise in faecal nematode egg counts (FEC), expressed in eggs per gram of faeces (epg), in lactating ewes. The immune capability of lambs is initially low but increases with the magnitude and duration of exposure to infection. Once significant immunity has developed (usually by 10-12 months of age), sheep are capable of markedly restricting parasite infection, except during times of disease, malnutrition or stress. For the effective control of nematode parasites, farmers have come to rely almost exclusively on broad-spectrum anthelmintics. However, issues relating to resistance, residues and eco-toxicity increasingly threaten the sustainability of chemotherapy. In order to maintain present levels of parasite control and productivity in the long term, farmers need to integrate management practices aimed at minimising animal exposure to parasites with reduced reliance on anthelmintics.

Journal Article↗
PubMed1993

Role of primary health care in the control of schistosomiasis. The experience in Riyadh, Saudi Arabia.

The control programme for schistosomiasis in Saudi Arabia was started in 1975 as a central vertical programme. With the adoption of the primary health care approach a pilot scheme that integrated the control of all endemic diseases, including schistosomiasis, within the functions of primary health care centres was carried out. In Riyadh, the scheme was started in 1984 when subcentres for the control programme were established as a first step for complete integration. A training programme was extended to personnel in primary health care centres, including physicians, nurses, and health inspectors with the help of experts from World Health Organization (WHO). A survey of the population at risk in areas with high prevalence was done regularly accompanied by treatment of cases. Snail control was an important activity of the health inspectors with a three months repeat of the control procedures. The result of this programme is a significant reduction in the prevalence of both urinary and intestinal schistosomiasis, from 13.2% in 1983 to 0.17% in 1989. Among the 7453 water sources surveyed in 1989, only 7 were positive for snails (0.1%). About two thirds of those who were affected were expatriates coming from areas of high prevalence of schistosomiasis. Details of the control programme and its impact on the control of the disease are presented in this paper.

Animals↗