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At least 55 records · Page 3Linked to original sources
PubMed1992

Intensity of reinfection with Ascaris lumbricoides and its implications for parasite control.

Intestinal helminths are among the most common and widespread of human infections. Because it is typical to find that most worms are aggregated in a few potential hosts it has been suggested that some individuals are predisposed to heavy infections and that morbidity could be controlled by the treatment of heavily infected individuals only. We have studied the prevalence and intensity of reinfection with the intestinal nematode Ascaris lumbricoides among people living in Dhaka, Bangladesh. 880 people were treated with pyrantel pamoate three times at six month intervals, and on each occasion they collected all their stools for 48 h after treatment. Worms expelled by each subject were counted and weighed. The prevalence of infection at round 1 of treatment was 89% and the mean burden was 18.5 worms. Reinfection was rapid and at rounds 2 and 3 the prevalence was 82% and 80%, respectively, with mean burdens of 14.0 and 11.5 worms. The intensity of reinfection was not random: more subjects than expected became heavily reinfected (greater than or equal to 15 worms) and more subjects than expected remained lightly infected (less than or equal to 14 worms) (p less than 0.001). Worms were highly aggregated at each round of treatment but although just over 10% of all subjects were heavily infected at each and every round of treatment, over 60% of all subjects were heavily infected at least once. The findings show that some individuals seem to be susceptible to heavy infection whereas others are not, that deworming has a greater effect on the intensity of infection than on the prevalence, and that mass chemotherapy is likely to be a more effective means to control morbidity than is selective treatment of heavily infected individuals only.

Adolescent↗
PubMed1986

Serum protein changes in ponies on different parasite control programmes.

Serum protein responses were examined in 52 ponies divided into five groups and subjected to various control strategies that resulted in pasture infectivity ranging from 706 to 18,486 infective third stage, cyathostome and Trichostrongylus axei larvae per kilogram of herbage (L3/kg) by 17 September 1984. Major protein changes occurred only in young ponies (Groups 4 and 5) and were observed before exposure to maximum numbers of pasture larvae (Group 4; 10,210 L3/kg, Group 5: 10,042 L3/kg) on 17 September. It appeared that a primary infection of T axei was a greater stimulus to serum beta-globulin and immunoglobulin (Ig)G(T) responses that provided by continued infection with cyathostome (small strongyle) worms. The large strongyles (Strongylus vulgaris, S edentatus and S equinus) were not detected in any larval cultures or on pastures grazed by the young ponies. A fall in beta-globulin and IgG(T) concentrations of Group 5 ponies one month after treatment with ivermectin indicated a larvicidal action against T axei and/or the cyathostomes. A subsequent rise in serum albumin concentrations of Group 5 ponies suggested that a protein-losing gastroenteropathy had been alleviated by the larvicidal action of ivermectin. Mature control ponies (Group 1) showed little beta-globulin response and only a modest IgG(T) response in six of the 10 ponies after exposure to heavily infected lawns (18,486 L3/kg) in September 1984. It was concluded that serum protein and IgG(T) responses were of limited value as an aid to diagnosis of parasitism because of numerous difficulties of interpretation.

Animals↗
PubMed1976

Live mass gains and wool production of merino sheep: three treatment programmes for parasite control.

A trial is described comparing the live mass gains and wool production of three groups of Merino sheep treated either at four-weekly intervals, strategically or not at all for the control of helminths and Oestrus ovis during a 19 month period. The group treated at four-weekly intervals had the greatest gain in masass was not greater than that of the group treated strategically. At both shearings the four-weekly treated group produced more wool than did the strategically treated group. The latter group produced more wool in total than did the untreated group. The seasonal incidence of nematodes, cestodes and Oestrus ovis on the trial farm was determined by the slaughter of tracer lambs at regular intervals.

Animals↗
PubMed1992

Production responses to internal parasite control in dairy cattle.

A significant increase in milk production, averaging 164 litres per cow per lactation (a 4.8% increase), was seen after cows infected with gastrointestinal nematodes, paramphistomes and Fasciola hepatica were treated with broad-spectrum anthelmintics. Three hundred and ninety pairs of cows from eight herds with year-round calving were studied. One cow in each matched pair was given 7.5 mg/kg fenbendazole, 7.5 mg/kg levamisole hydrochloride and 15 mg/kg oxyclozanide in March, May and August of one year; the other cow in the pair received no anthelmintic. The number of nematode and trematode eggs was significantly decreased in the faeces of treated cows.

Animals↗
PubMed1991

The effect of parasite control on fertility in beef heifers.

The effect of anthelmintic treatment on the growth and conception rate in beef heifers was studied in southwestern Virginia, USA. Forty mixed-breed heifers were divided into two groups at weaning and placed on experimental pastures. Control heifers did not receive anthelmintic treatment, while animals in the treatment group were given ivermectin (200 micrograms kg-1) at the time of allocation to groups in October and again in April the following year. Supplemental feed was provided throughout the winter to ensure adequate weight gains. In May, the heifers were exposed to bulls for natural breeding for a period of 6 weeks. Weight gains, fecal egg counts, serum pepsinogen levels and pasture larvae counts were monitored throughout the experiment. No difference in conception rate was observed between the two groups, although the cumulative weight gain was significantly greater in treated than non-treated animals. Serum pepsinogen levels and fecal egg counts were also generally lower in treated than non-treated heifers.

Animals↗
PubMed1989

The effect of stocking rate and parasite control on the performance of replacement beef heifers on pasture.

This study was designed to compare the animal production per unit area and per animal at 3 different stocking rates in combination with two deworming programs. Due to drought conditions, fecal egg output, serum pepsinogen levels and herbage larval counts were low throughout the grazing season. The beneficial effects of the strategic deworming program were, however, indicated by lower fecal egg counts and serum pepsinogen levels in the treated groups during most of the grazing season. Differences in weight gain, favoring the treated groups, were also observed and a clear effect of stocking rate was demonstrated. The lowest stocking rate groups continuously had the lowest egg output and serum pepsinogen levels and the highest average weight gain per animal. The experiment also clearly showed that the production per unit area increased with an increase in stocking rate. The medium and high stocking rate groups had a production per unit area exceeding that of the conventional stocking rate group by 15 and 45%, respectively.

Animals↗
PubMed1994

Ageing alters the competence of the immune system to control parasitic infection.

The elderly are more susceptible to infections with various pathogenic organisms that are young-adults or middle-aged individuals. Certain microorganisms that are non-pathogenic in adults may cause serious infections in the elderly. This heightened susceptibility of the elderly is most likely a reflection of the age-associated decline in the competence of the immune system. It appears that the population of T cells is altered with advanced age and, possibly, the efficiency of the monocyte/macrophage cells to destroy microbial invaders declines. There is a small, but compelling, body of literature which shows that the elderly are particularly susceptible to protozoan and metazoan parasites. We have studied the markedly increased severity of infections in aged mice with the mouse-specific Trypanosoma musculi; both the parasite burden and the duration of infection are substantially greater in old compared to young mice. It appears that this difference is due, to a large extent, to the relatively weak ability of aged animals to generate cytokines associated with the TH1 subset of CD4+ T cells; in particular, the weak ability to generate IL-2 and IFN gamma which are involved in the selective expression of curative, parasite-specific antibody of the IgG2a isotype. A striking difference between young and aged mice is in the response of IL-3 producing cells to the parasite infection; IL-3-producers decline during infection in young mice but increase markedly in aged animals. There are several advantages to using T. musculi as a prototype pathogen for studying age-related susceptibility to infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1982

The ecological basis of parasite control: ticks and flies.

Tick and fly control programmes have undergone radical review in recent years. Insecticidal control measures are now often seen as a means of reducing target populations to a level sufficiently low for final eradication by biological or ecological techniques, the sterile male method (SIRM) being particularly favoured. As a preliminary, the new range of insecticidal application techniques includes insecticidal tags, bands, blouses, implants and pheromone baits. The final eradication programme could then involve the use of sterile flies or sterile hybrid ticks, for example. Immunization of cattle against ticks, the use of tick-resistant crossbreeds of cattle, tick-repellent grasses and dung burying beetles are among the additional techniques now being actively investigated.

Animals↗