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  • Journal article
    Smith G, Grenfell BT, Anderson RM, Beddington Jet al., 1987,

    Population biology of Ostertagia ostertagi and anthelmintic strategies against ostertagiasis in calves.

    , Parasitology, Vol: 95 ( Pt 2), Pages: 407-420, ISSN: 0031-1820

    Five chemoprophylactic or chemotherapeutic strategies against bovine ostertagiasis are compared using a mathematical model of the population biology of Ostertagia ostertagi. The model offers a means of screening novel strategies prior to their further investigation in the field. Under conditions of climate and management typical of many regions in Northern temperate Europe, the model indicates that all of the tested prophylactic strategies will result in a profound reduction in the intensity of infection in grazing beef calves when compared with an untreated control group or the simple therapeutic protocol. Not all of those strategies which caused diminution in the scale of the midsummer rise in pasture larval contamination resulted in progressively less contaminated pastures in subsequent years. Moreover, the reproductive potential of the parasite is so great that the principal advantage of the 'pasture cleaning' effect that is the consequence of some protocols is not that the pasture may eventually be used to graze untreated calves but that the treated animals are subjected to a progressively smaller parasitic challenge with the concomitant pay-off in production gains.

  • Journal article
    GRENFELL BT, SMITH G, ANDERSON RM, 1987,

    THE REGULATION OF OSTERTAGIA-OSTERTAGI POPULATIONS IN CALVES - THE EFFECT OF PAST AND CURRENT EXPERIENCE OF INFECTION ON PROPORTIONAL ESTABLISHMENT AND PARASITE SURVIVAL

    , PARASITOLOGY, Vol: 95, Pages: 363-372, ISSN: 0031-1820
  • Journal article
    Smith G, Grenfell BT, Anderson RM, 1987,

    The regulation of Ostertagia ostertagi populations in calves: density-dependent control of fecundity.

    , Parasitology, Vol: 95 ( Pt 2), Pages: 373-388, ISSN: 0031-1820

    The decline in faecal egg counts, characteristic of calves which have been experimentally infected with Ostertagia ostertagi, is analysed using a mathematical model in which parasite fecundity is assumed to be an inverse function of both the duration and intensity of infection. The model incorporates a description of the frequency distribution of mature parasites between hosts (which is less over-dispersed than is usual for many other helminth infections). The model provides a good overall description of the decline in faecal egg production observed during trickle and single infection experiments. The main discrepancy between a comparison of the model predictions and the results of the most detailed available series of trickle infection experiments occurs at the initial peak of egg production. The magnitude of this difference appears to be related to the worm burden at the peak of egg production. The possible mechanisms underlying density-dependent regulation of the fecundity of O. ostertagia are discussed.

  • Journal article
    GRENFELL BT, SMITH G, ANDERSON RM, 1987,

    A MATHEMATICAL-MODEL OF THE POPULATION BIOLOGY OF OSTERTAGIA-OSTERTAGI IN CALVES AND YEARLINGS

    , PARASITOLOGY, Vol: 95, Pages: 389-406, ISSN: 0031-1820
  • Journal article
    SMITH G, GRENFELL BT, ANDERSON RM, 1987,

    THE REGULATION OF OSTERTAGIA-OSTERTAGI POPULATIONS IN CALVES - DENSITY-DEPENDENT CONTROL OF FECUNDITY

    , PARASITOLOGY, Vol: 95, Pages: 373-388, ISSN: 0031-1820
  • Journal article
    HASWELLELKINS MR, ELKINS DB, MANJULA K, MICHAEL E, ANDERSON RMet al., 1987,

    THE DISTRIBUTION AND ABUNDANCE OF ENTEROBIUS-VERMICULARIS IN A SOUTH INDIAN FISHING COMMUNITY

    , PARASITOLOGY, Vol: 95, Pages: 339-354, ISSN: 0031-1820
  • Journal article
    Haswell-Elkins MR, Elkins DB, Manjula K, Michael E, Anderson RMet al., 1987,

    The distribution and abundance of Enterobius vermicularis in a South Indian fishing community.

    , Parasitology, Vol: 95 ( Pt 2), Pages: 339-354, ISSN: 0031-1820

    The distribution and abundance of Enterobius vermicularis in a fishing community in South India, as determined by counting worms expelled following mass anthelmintic chemotherapy, was examined in samples of patients stratified by age, sex and family grouping. The results of a worm expulsion study in January 1984 are compared with those of a second expulsion programme in November 1984, following an 11-month period of reinfection. The prevalence of Enterobius infection was consistently high in all age groups of both males and females. A comparison of the overall prevalence and intensity of infection in the January and November surveys revealed significant increases in both the percent infected and the mean number of worms harboured in November relative to the initial level. No significant trends in the intensity of Enterobius according to host age or sex were detected in either survey. The frequency distribution of Enterobius was found to be highly aggregated in the population as a whole and within age groups. At both sampling dates, the most heavily infected 25% of the community harboured over 90% of the total pinworms recovered. There was a significant pattern within most age groups for individuals to re-acquire worm burdens of a similar magnitude to their initial pre-treatment burdens. Heavy infections were found to be associated with household. A selective or targetted approach to treatment of heavily infected individuals or households is likely to be an efficient means of reducing parasite abundance on a community-wide basis. It must be stressed, however, that treatment must be applied at frequent intervals in order to achieve a long-term reduction in pinworm abundance and to avoid the possibility of increasing the intensity of infection, as was observed in this community.

  • Journal article
    SMITH G, GRENFELL BT, ANDERSON RM, BEDDINGTON Jet al., 1987,

    POPULATION BIOLOGY OF OSTERTAGIA-OSTERTAGI AND ANTHELMINTIC STRATEGIES AGAINST OSTERTAGIASIS IN CALVES

    , PARASITOLOGY, Vol: 95, Pages: 407-420, ISSN: 0031-1820
  • Journal article
    HASWELLELKINS MR, ELKINS DB, ANDERSON RM, 1987,

    EVIDENCE FOR PREDISPOSITION IN HUMANS TO INFECTION WITH ASCARIS, HOOKWORM, ENTEROBIUS AND TRICHURIS IN A SOUTH INDIAN FISHING COMMUNITY

    , PARASITOLOGY, Vol: 95, Pages: 323-337, ISSN: 0031-1820
  • Journal article
    Grenfell BT, Smith G, Anderson RM, 1987,

    The regulation of Ostertagia ostertagi populations in calves: the effect of past and current experience of infection on proportional establishment and parasite survival.

    , Parasitology, Vol: 95 ( Pt 2), Pages: 363-372, ISSN: 0031-1820

    A mathematical model of the parasitic phase of the life-cycle of Ostertagia ostertagi in calves is described. The model is used in the re-analysis of previously published data from a long-term trickle infection experiment in which groups of calves were infected daily with graded doses of 3rd-stage (L3) larvae. The results of the analysis are consistent with the hypothesis that the observed changes in the intensity of infection in the calves were the result of a decline in the proportional establishment of ingested L3 larvae, and a rise in the death rate of the 5th-stage worms as the duration of exposure to infection increased. The proportion of ingested L3 larvae that become established in the mucosa can be described as an exponential decay function of the duration of the infection. Within the range of trickle intensities investigated, the function appears to vary independently of the level of exposure to infection. In contrast, the rate of mortality of the 5th-stage worms appears to be an increasing linear function of the total cumulative number of 3rd-stage larvae administered.

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

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