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At least 109 records · Page 6Linked to original sources
PubMed1994

Parasitic control in intensive vs. non-intensive systems--ruminants.

The acquisition and intensity of infection with gastrointestinal nematodes and with Oestrus ovis are compared over 2 years in sheep grazed intensively (26-36 sheep ha-1) or non-intensively (12 sheep ha-1) in the winter rainfall Overberg region of South Africa. Sheep grazing intensively on grass/legume pastures, spray irrigated in summer, acquired massive mixed infections of Trichostrongylus, Haemonchus and Teladorsagia. Infections were fatal for sucking lambs. Lambs from ewes grazed non-intensively on dry land lucerne in winter became infected with Nematodirus and then with Teladorsagia and Trichostrongylus spp.; resistance to Nematodirus was apparent after 12 weeks; spontaneous cure of Teladorsagia began in hoggets grazing on safe wheat stubble pasture; but Trichostrongylus survived in the sheep. Helminth-induced host mortality was not observed on the non-intensive farm. The efficacy of various methods of control was examined in the intensively managed sheep. Removal from pasture, mixed grazing (cattle before sheep) and an albendazole slow release bolus all significantly (P < 0.05) reduced levels of infection in animals so treated, compared with control sheep which were treated periodically with anthelmintics as standard farm management practice. Removal of sheep from the pasture for 30 days in the summer seemed to have beneficial effects. Treatment of sheep weekly with albendazole increased levels of infection in the sheep over controls. The status of vaccination is described and the potential of intergenic competition in grazing management and perhaps vaccination is discussed. Resistance of nematodes to anthelmintics was relatively wide-spread. In both intensive and non-intensive systems. Oestrus ovis larvae were present in flock sheep for 10-12 months per year. Imagines failed to develop from 27 April-9 August and it was concluded that larvae had to overwinter in sheep to survive. Recommendations for integrated control are made for both intensive and non-intensive systems.

Animal Husbandry↗
PubMed1979

Equine parasite control using pyrantel embonate.

Over a period of several years the use of pyrantel embonate in the control of helminth infections on three equine establishments was monitored by the examination of faecal samples collected immediately before each anthelmintic treatment. With a monthly interval between treatments for three years the faecal egg output of the horses remained at a very low level. One one establishment this was maintained when the treatment interval was extended to one-and-a-half months after treating monthly for two years. If a treatment interval of one-and-a-half months was used continuously for a number of years there was a cumulative effect, and the benefits, in terms of reduced faecal egg output of the horses, were more apparent during the second year of the control programme.

Animals↗
PubMed2002

Expansion of NK cells with reduction of their inhibitory Ly-49A, Ly-49C, and Ly-49G2 receptor-expressing subsets in a murine helminth infection: contribution to parasite control.

Natural killer cell-associated direct cytotoxicity and cytokine production are crucial mechanisms for early innate host resistance against viruses, bacteria, or protozoa. The engagement of inhibitory NK cell receptors can influence host responses to viruses. However, these receptors have not been investigated to date in parasitic infections, and little is known about the role of NK cells in the defense against helminths. Therefore, we have correlated the frequencies of cells expressing the pan-NK marker DX5 and subsets bearing inhibitory Ly-49 receptors with worm survival and cytokine production during infection with Litomosoides sigmodontis in BALB/c mice (H2(d)), the only fully permissive model of filariasis. A marked influx of DX5(+)/CD3(-) NK cells and DX5(+)/CD3(+) T cells into the pleural cavity, where the parasites were located, was observed. The frequency of pleural NK cells expressing the H2(d)-reactive inhibitory receptors Ly-49A, Ly-49C, or Ly-49G2 declined most strongly compared with spleen and blood. In the peripheral blood, longitudinal analysis revealed an early and stable reduction of Ly-49C(+) and Ly-49G2(+) NK cells, a subsequent significant increase of the entire NK cell and DX5(+)/CD3(+) T cell populations, and a reduction in the Ly-49A(+) subset. The in vivo depletion of NK cells strongly enhanced the worm load and influenced IL-4 and IL-5 plasma levels. These data demonstrate a new role for NK cells in the host defense against filariae and, for the first time, alterations of Ly-49 receptor-expressing NK cell subsets in a parasitic infection.

Animals↗
PubMed2001

Internal parasite control strategies.

To maintain the general health of small ruminants, owners, managers, and clinicians should be familiar with the body condition-scoring [table: see text] methods, general health, and overall appearance of the animals in their care. Any changes in the overall health of individual animals or the flock should be noted immediately, the cause determined, and immediate measures should be taken to correct any problems. Parasite management in small ruminants is a difficult and arduous task. When a program that reduces parasite infestation is discovered, it should be carefully implemented, maintained with vigilance, and constantly "tweaked" to maximize its effectiveness.

Animals↗
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↗
PubMed2004

Both IL-12 and IL-18 contribute to small intestinal Th1-type immunopathology following oral infection with Toxoplasma gondii, but IL-12 is dominant over IL-18 in parasite control.

Oral infection of C57BL/6 mice with Toxoplasma gondii results in small intestinal Th1-type immunopathology mediated by local production of IFN-gamma, TNF-alpha, and NO. To analyze whether the proinflammatory cytokines IL-12 and IL-18 play a role in the induction of immunopathology, IL-12p35/p40(-/-) and IL-18(-/-) mice were orally infected with T. gondii. Wild-type mice developed massive necrosis in their small intestines and died 7-10 days post infection. Even though IL-12p35/40(-/-) mice did not develop the necrosis they all died between day 9 and 11 after infection. In contrast, 50% of IL-18(-/-) mice died during the acute phase of infection. Compared to wild-type mice, IL-12p35/p40(-/-) but not IL-18(-/-) mice showed significantly higher parasite numbers in their small intestines and significantly higher numbers of parasite-associated inflammatory foci in their livers. IFN-gamma production was similar in infected wild-type and IL-18(-/-) mice but significantly decreased in IL-12p35/p40(-/-) mice. Treatment of mice with anti-IL-12- or anti-IL-18 antibodies after infection prevented the development of intestinal necrosis. These results reveal that both IL-12 and IL-18 play an important role in the development of intestinal immunopathology following oral infection with T. gondii. However, IL-12 is dominant over IL-18 in the host defense against parasite replication. Therefore, neutralization of IL-18 (rather than TNF-alpha, IL-12, and IFN-gamma) may be a safe strategy for the treatment of Th1-associated diseases.

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↗