Kurzbeschreibung
(Englisch)
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Globally, Haemonchus contortus is the most important nematode parasite of sheep and goats. Whereas vaccination of sheep against haemonchosis has been developed to a successful stage, there is yet no information if this strategy is also applicable in goats. As goat husbandries are even more affected worldwide by the development of anthelmintic resistance compared with sheep, vaccination against the most important nematode species should therefore be added to the spec-trum of potential alternative control measures beside the chemical route. The planned study is divided into two parts comprising the proof of principle in artificially infected animals and an antigen-dose-titration experiment with pastured animals. In Trial 1 the degree of protection is investigated in young goats after a standard vaccination regime derived from sheep and challenge with an artificial Haemonchus-infection. In Trial 2 a dose-titration experiment will investigate the dose de-pendency of the induced protection. Therefore 3 groups of young goats will undergo a different vaccination regime with respect to the antigen dose per single application. Protection is measured after natural infection from pasture and compared with infected control animals. The results of Trials 1 and 2 will provide us with the essential data to subsequently perform vaccination studies in privately owned goat farms.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, DE, DK, ES, FR, GR, HR, HU, IL, IT, LT, MK, NO, PT, RO, RS, SE, SK, UK
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Abstract
(Englisch)
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Infections with gastrointestinal nematodes represent a major health problem in grazing goats. The blood-feeding nematode Haemonchus contortus is regarded as the most pathogenic species. During the grazing season of 2012 an experimental vaccine against this parasite was tested in two goat herds using two different experimental designs. In farm A the vaccine was administered at four-week-intervals to young and adult animals whereas two comparable groups remained unvaccinated. The adults of both groups were naturally infected from the previous season. During the entire season the mean egg output in the faeces of the vaccinated adults ranged below that of the respective control animals. The young animals shed eggs on a considerably higher level than the adults and the overall ratio between the groups was about 1:4.5 in favour of the vaccinated animals. Statistical comparison of all measured parameters will be completed in 2013. Altogether, Haemonchus represented about 60% of the total egg output, a number which is typical for the epidemiological conditions in Switzerland. A special situation occurred due to the unexpected presence of another blood-feeding nematode, Bunostomum trigonocephalum. This species is inhabiting the small intestine and, beside H. contortus, influences the haematological parameters, with the consequnces that the respective analyses will be more complex. The results obtained so far indicate, that Bunostomum was not affected by the vaccine. In the second farm (B) young goats (n = 40) were grazed on pastures which had been artificially seeded with Haemonchus larvae before turnout of the experimental animals. This procedure provided a system, where Haemonchus was the only trichostrongylid species and results were not influenced by other gastrointestinal nematodes. Two of the vaccinated groups and the unvaccinated controls were kept together on the same pasture, whereas a third vaccinated group was grazed separatly. The mean egg output of the commonly grazed groups developed very similar with a sharp increase at the beginning of June and marked decline until the end of July. The unexpected decrease of the egg output in the controls independent of treatment must be explained with an untypical strong development of immunity in this age group. The level of infection in the vaccinated group which was grazed separatly was much lower compared with the other groups. After the end of the grazing period all animals received anthelmintic treatment and were artificially challenged with Haemonchus larvae. After slaughter of all animals, worm populations were quantified. The vaccinated animals showed a 66% reduction of the adult worm population compared with the controls. The remaining analyses will include the determination of the individual antibody titers against the vaccine antigen. These data will be essential for the interpretation of the parasitological data.
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