29 research outputs found

    Parasites of domestic and wild animals in South Africa. XLV. Helminths of dairy calves on dry-land Kikuyu grass pastures in the Eastern Cape Province

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    Successive pairs of approximately 4-month-old Friesland bull calves, raised under worm-free conditions, were exposed to helminth infection for 14 days on dry-land Kikuyu grass pastures at 28-day to monthly intervals, on a coastal farm in a non-seasonal rainfall region of the Eastern Cape Province. With the exception of one pair of calves exposed for 28 days, this procedure was repeated for 28 consecutive months from December 1982 to March 1985. The day after removal from the pastures one calf of each pair was slaughtered and processed for helminth recovery and the other 21 days later. Both members of the last four pairs of calves were killed 21 days after removal from the pastures. Sixteen nematode species were recovered from the calves, and infection with Ostertagia ostertagi was the most intense and prevalent, followed by Cooperia oncophora. The calves acquired the greatest number of nematodes from the pastures from June to October of the first year and from June to August of the second year of the survey. Few worms were recovered from the tracer calves examined from November or December to March or April in each year of the survey. The seasonal patterns of infection with Cooperia spp., Haemonchus placei, Nematodirus helvetianus, Oesophagostomum spp., O. ostertagi and Trichostrongylus axei were all similar and were negatively correlated to atmospheric temperature and evaporation. Slight to moderate arrest in the development of fourth stage larvae occurred from July to September in Cooperia spp., April to July in H. placei, and August to October in O. ostertagi and Trichostrongylus spp. during the first year of the survey. Too few worms were present in the second year to determine a seasonal pattern of arrest. Species survival during the hot and windy summer months appeared to be achieved via a combination of arrested larval development and an ageing residual population of adult worms in the host, and a small extant population of infective larvae on the pastures

    Heartwater : past, present and future : proceedings of a workshop held at Berg en Dal, Kruger National Park, on 8-16 September 1986

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    As a result of a personal survey in 1982, interviewing veterinarians from Louis Trichardt to Uitenhage, it was concluded that bovine heartwater is currently regarded as the most serious tick-borne disease problem in South Africa. A combination of long-acting oxytetracycline and prednisolone is regarded as the most effective therapy. The disease is almost inevitable in unprotected young high-grade susceptible stock introduced into endemic areas such as the northern Transvaal and the Valley Bushveld of Natal and the Eastern Cape. A series of trials was conducted at Settlers, Pietermaritzburg and East London on farms representative of these areas and it was demonstrated that 4 injections of 20 mg/kg of long-acting oxytetracycline on Days 0, 7, 14 and 21 after introduction enabled such stock to be introduced without the disease occurring. A further trial was carried out on the Pietermaritzburg farm, where it was shown that the number of injections could be reduced to 3, on Days 7, 14 and 21 or Days 7, 12 and 17, or even 2 on Days 7 and 14. Two points need stressing. First, these results were obtained in areas of high heartwater endemicity. Second, in order to be confident that the regime will be effective it is necessary to have acquired knowledge of the epidemiology of the disease at the farm. Thus in the 2nd year at Pietermaritzburg we were able to use a reduced treatment regime because we knew the pattern of disease occurrence. Problems are perceived for the large scale introduction of such a prophylactic regime, namely: (1) a 100% challenge must occur in the first 4 weeks of exposure; (2) immunologically distinct strains of heartwater may occur on the same farm at different times of year; (3) the duration of immunity acquired as a result of the regime has not yet been established, and (4) the attritive Theileria mutans-type pathogen which is very common in South Africa may cause breakdowns in heartwater immunity. Since oxytetracycline is known to be active against all major tick-borne pathogens of cattle, and even apparently against the ticks themselves, some form of prolonged administration of the drug could be used to overcome the problems enumerated above.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
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