Effect on lambing percentage of vaccinating ewes with Toxoplasma gondii

Authors: O'Connell E, Wilkins MF
Publication: New Zealand Veterinary Journal, Volume 31, Issue 10, pp 181-182, Oct 1983
Publisher: Taylor and Francis

Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Animal remedies/veterinary medicines, Reproduction, Immune system/immunology, Pregnancy, Reproduction - female, Vaccination
Article class: Correspondence

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Abstract: Because Toxoplusma gondii is frequently identified in dead lambs and placentas from ewes which have aborted, this association is often interpreted as one of cause and effect. However, T. gondii is a well-adapted parasite and may in fact be isolated from the placenta at lambing even when the lamb survives and is reared normally. Unless the frequency of infection can be determined in both the surviving and non-surviving neonates, it is not possible to estimate the prevalence of abortion and perinatal mortality due to toxoplasmosis. One simple approach would be to use an effective vaccine on a split-flock basis and compare differences in lambing records of vaccinated and non-vaccinated ewes. Such a trial has been conducted by us on a commercial farm near Masterton. The flock had a poor lambing in the previous season, with losses being attributed to both campylobacteriosis and toxoplasmosis. Serological tests on a sample of the two-tooth flock indicated that about half had had previous exposure to toxoplasma. Of this flock of 1002 two-tooth ewes, half were randomly selected and vaccinated with an “incomplete” strain of T. gondii about six weeks before tupping commenced. (The “incomplete” strain appears to have lost its capacity to reproduce sexually in cats.) Lamb numbers at docking were compared between groups and results are shown…

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