A comparison of the spring-rise phenomenon in the faecal nematode-egg counts of housed sheep with that of sheep grazing infective pasture

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Abstract
Extract Among the various aspects of the seasonal fluctuations of worm egg counts of sheep investigated by research workers, the “spring-rise” phenomenon has aroused considerable interest and has focused attention on the role played by the ewe in trichostrongyle population dynamics. Studies on this phenomenon have been summarized by several workers (Crofton, 1954 Crofton, H.D. 1954. Nematode parasite populations in sheep on low-land farms. I. Worm egg counts in ewes. Parasitol., 44: 465–477. [Crossref], [PubMed], [Web of Science ®] [Google Scholar] , 1958 Crofton, H.D. 1958. Nematode parasite populations in sheep on low-land farms. V. Further observations on the post-parturient rise and a discussion of its significance. Parasitol., 48: 243–250. [Google Scholar] , 1963 Crofton, H.D. 1963. Nematode parasite population irr sheep and on pasture, Tech. Comm. No. 35. 104–104. St. Albans: Commonwealth Bureau of Helminthology. [Google Scholar] ; Field et al., 1960 Field, A.C. , Brambell, M.R. and Campbell, J.A. 1960. Spring rise in faecal worm-egg counts of housed sheep and its importance in nutritional experiments. Parasitol., 50: 387–399. [Crossref], [PubMed], [Web of Science ®] [Google Scholar] ; Soulsby, 1962 Soulsby, E.J.L. 1962. “Immunity to helminths and its effect on helminth infections”. In Animal Health and Production, 165–188. London: Butterworths. [Google Scholar] ; Spedding, 1962 Spedding, C.R.W. 1962. Modern trends in animal health and husbandry. The agricultural ecology of sheep grazing. Brit. vet. J., 118: 461–481. [Google Scholar] ). The occurrence of a spring-rise in breeding ewes in New Zealand was recorded by Brunsdon ( 1964 Brunsdon, R.V. 1964. The seasonal variations in the nematode egg counts of sheep A comparison of the spring rise phenomenon in breeding and unmated ewes. N.Z. vet. J., 12: 75–80. [Taylor & Francis Online] [Google Scholar] ) who has also demon- strated the importance of the contamination deposited by the ewe at the time of the spring-rise, in affecting the speed and degree of build-up of trichostrongyle infestation in lambs (Brunsdon, 1966 Brunsdon, R.V. 1966. Importance of the ewe as a source of trichostrongyle infection for lambs Control of the spring rise phenomenon by a single post-lambing anthelmintic treatment. N.Z. vet. J., 14: 118–125. [Taylor & Francis Online] [Google Scholar] ).