National survey shows increased toxoplasmosis threat

Intervet’s annual FlockCheck survey has highlighted a 28% increase in the number of flocks that have been exposed to toxoplasmosis since this time last year. This could lead to a significant increase in abortions and barrenness over the winter months if action, in the form of vaccination, to prevent infection of pregnant ewes is not taken prior to tupping.

FlockCheck, which annually looks at blood samples from around 350 farms, aims to determine the cause or causes of lack of ewe productivity. It examines whether flocks have been exposed to toxoplasmosis and/or enzootic abortion (EAE). The 2007 results show exposure to toxoplasmosis to be the highest since FlockCheck records began in 1994 (82% compared to eight-year average of 71%), with a fairly even distribution across England, Scotland and Wales.

This contrasts to the threat posed by EAE, where levels of detection have fallen for the past two years. However, they are still relatively high at 49% compared to an eight-year average of 54%.

Flocks testing positive for both EAE and toxoplasmosis have increased to 41%, compared with an eight-year average of 37.5%.

Fig 1 – FlockCheck results (1994-2007) showing the threat posed to ewe productivity by EAE and toxoplasmosis.

Toxoplasma infection only a threat if it is picked up by ewes when they are pregnant. Exposure at different stages of pregnancy will determine the outcome.

• First 60 days
  • foetus re-sorbed and the ewe appears barren
• 60 days to full term
  • abortion in late pregnancy
  • mummified foetuses
  • stillbirths at term
  • weak and sickly lambs that often die
• Any other time
  • the ewe will develop her own natural immunity

To protect the entire flock, it is usually necessary to vaccinate all animals once (with a single injection). Thereafter, only replacement females need to be vaccinated. The only vaccines to prevent both these diseases which are licensed to be given at the same time are Enzovax^® and Toxovax^®, both of which are available from your vet.