A new challenge moving south

By Rachael Fouhy

In Livestock6 Minutes

Many farmers have dealt with facial eczema (FE) for years, however for those of us in the lower North Island this has become more of a challenge in recent years. FE is a disease that used to affect the Tararua district once every 10 years, however, three of the last four years have provided eczema challenges for us. With that in mind, this article is written for farmers in the lower North Island and all the South Island for whom FE is not a regular occurrence.

FE is a fungal toxin that grows in pasture from late summer onwards. The fungus Pithomyces chartarum lives in the pasture all year round and when the conditions are right it rapidly proliferates. The two things needed for FE growth are warm weather and moisture. In our area we often see these conditions in March when there are still warm night temperatures (12°C plus) and recent rain. When these conditions occur, the fungal growth produces spores that sit deep in the litter base. It is these spores that the animals ingest and which cause the damage. Areas that tend to have higher fungal growth include sheltered areas and warmer north-facing areas.

When the fungal spores are ingested they release a toxin – sporidesmin which causes damage to the liver and bile ducts. This can lead to blockage of bile ducts and build up of bile in the liver, and in the bloodstream the bile and waste products build up resulting in the photosensitivity that we commonly associate with FE. These toxins also cause damage and scarring to the liver. The liver does have the ability to regenerate, however, FE can cause significant damage and scarring to the liver and this isn’t reparable. This impacts an animal’s lifetime performance.

People most commonly recognise FE as an issue when they see sheep with peeling skin or floppy ears. However, subclinical or unseen eczema is a much bigger issue. In these cases the liver still suffers a significant amount of damage, just not enough to cause skin lesions. This damage can result in decreased growth rates, poor condition and decreased reproductive performance. This will often be evident as a decreased scanning percentage (fewer multiples). The impact of eczema can show up in the spring, as often animals can pack up after a period of stress, e.g. lambing. These animals may be found dead or might waste away. If an animal gets eczema year on year, the damage can be cumulative.

How do you know if you might have challenges with eczema? Kill sheets are able to provide information about the liver and may give an indication that eczema is an issue. Other approaches include doing some post mortems on ill-thrifty sheep or taking blood samples pre- or post-scanning.

GGT, the liver enzyme that becomes elevated with FE damage can remain high for a long time. So if your scanning was back, blood testing the dries is a cheap and simple approach. Most vet clinics run a spore counting service: check what’s happening in your area.

Options for preventing eczema include:

  • Making use of spore counts in your area to understand the risk. Counts can vary greatly between properties so the best advice is to test paddocks on the farm. Test this weekly.
  • Using zinc capsules as a preventative tool. These need to be given prior to the risk period. There are two products available: Time Capsules and Faceguard. They can only be given for a set period, so it is important to give them at the right time.
  • Spraying fungal sprays on pasture to provide up to six weeks protection.
  • Genetics – this is the way to progress as we look to increase tolerance to eczema. Many breeders have been selecting for this for a long time and have built up some excellent tolerance. Rams are tested by AgResearch and given estimated breeding values based on their results. Ram breeders will test their rams at different levels based on the flock’s level of tolerance. When talking to breeders about FE tolerance and testing it’s important to ask how long they have been testing for, what levels they are being tested at and how many rams they are testing? FE tolerance has a high heritability compared with some other genetic traits and is worthwhile investing in. For more information check out www.fegold.co.nz
  • Rachael Fouhy is head vet at Tararua Veterinary Services, Pahiatua.