Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii.  It has a two stage life cycle.  Many species of warm blooded animals can act as host to the asexual stage of the life cycle, while only cats can be the host of the sexual stage of the life cycle.  Therefore, it is cats that amplify and spread the infection to sheep via their faeces contaminating feed. Spread from rams may also be an important route of spread

After ingestion of feed or water contaminated with Toxoplasma oocysts, susceptible sheep become and remain infected for life.  Infection of the placenta and foetus occurs only when the initial infection establishes in a susceptible pregnant ewe.

Toxoplasmosis in susceptible, previously naive pregnant ewes causes abortions, stillbirths and lamb deaths. Research indicates that ewes infected with Toxoplasma in early pregnancy experience foetal loss and therefore will be dry at scanning. This is often mistaken for ewe infertility and results in the unnecessary culling of otherwise fertile animals. Ewes infected in mid pregnancy or later are likely to abort, or give birth to still-born or weak lambs that fail to thrive.
Toxoplasmosis can cost you in three ways:
  • The loss of lambs by abortion; either by low-level unseen losses, or large-scale abortion storms.
  • The birth of weak lambs, which fail to thrive, or die.
  • The culling of fertile ewes, which because of undetected early abortion are presumed barren.
Toxoplasmosis occurs throughout New Zealand. Every sheep flock can be affected by ongoing insidious losses and abortion storms. Ewe hoggets and two tooths are at most risk, but any ewe that contracts Toxoplasmosis for the first time while she is pregnant is likely to lose her lamb/s.
Toxovax® is a single dose vaccine that provides breeding ewes with lifetime protection against the effects of Toxoplasmosis. Vaccination with Toxovax increases lambing percentage by an average of at least 3% and decreases the incidence of dry ewes by an average of 14%.
As Toxovax is a live vaccine it has a short shelf life and must be made to order. To ensure supply it is imperative that you order your requirements at least eight weeks in advance of putting the ram in. This will allow you to give Toxovax to 1st time breeding ewes at least four weeks before mating, but it can also be given any time prior to this.