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Abortion vaccination a critical practice on Laois sheep farm
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Abortion vaccination a critical practice on Laois sheep farm

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Vaccination against toxoplasmosis, one of the two major causes of abortion in sheep, is an integral part of the herd health programme for Laois farmer Paul McDonald.
Vaccination against toxoplasmosis, one of the two major causes of abortion in sheep, is an integral part of the herd health programme for Laois farmer Paul McDonald.

Paul and his father JJ run a flock of 250 ewes at Tankardstown. They have been using the vaccine for the past 20 years, following a massive outbreak of the disease. It happened before Paul got involved, but his father and mother Kathleen have vivid memories of the “horror story”.

“Nearly every one of a bunch of 50 hoggets aborted. Every day we went out to the shed, we were just tripping over aborted lambs. It was absolutely shocking,” said Kathleen.

All breeding sheep entering the flock are given the one-shot vaccine at least one month before they go to the ram.

A few years ago, the vaccine was not available and this caused major worries.

“We kept the bought-in ewe hoggets completely separate from the main flock. We bought two rams specially for the hoggets and we lambed them separately from the rest of the flock. Thankfully, we had no problems. We were very relieved when supplies of the vaccine returned the following year,” said Paul.

They buy in around 50 ewe hoggets each year to meet their replacement needs. When we called to the farm in the third week of July, 45 hoggets had already been bought by JJ at Tullow Mart. They averaged just under €200/head.

Main flock

The rams were due to be let out with this year’s main flock of 193 ewes on 1 August, with lambing due to start just after Christmas.

The bought-in hoggets will go to the rams on 1 September. They get their toxoplasmosis vaccination at least one month in advance of breeding.

They use Charollais and Texel rams, which, according to Paul, give excellent lamb performance and remarkably low lambing difficulties. “This year, we had to assist just a tiny number of ewes at lambing,” he said.

Just under 1.6 lambs/ewe to the ram were sold off the farm this year. All but 13 of almost 400 lambs were sold by the third week of July. They averaged €124.

Ewes and lambs go on to rape immediately after lambing. “It is excellent for milk yield and lamb growth,” said Paul.

Cats the big culprits

Toxoplasmosis, caused by a microscopic parasite Toxoplasma gondii (T. gondii), is most commonly caused by contaminated cat faeces in feed, bedding or manure or directly on to pasture.

“A single cat dropping can contain enough eggs to infect more than 5,000 ewes. It takes only one brief visit from a cat to contaminate the farmyard or pasture and almost 75% of ewes are believed to come in contact with T. gondii during their lifetime,” said veterinarian Joanne Cregg.

She added that vaccination is the only way to effectively build uniform immunity to toxoplasmosis in the flock.

“Where the risk of infection is high on a heavily contaminated farm populated with previously unexposed sheep, initial whole-flock vaccination is cost effective.

“As each situation is different, farmers should consult their vet about the most effective vaccination strategy for their flock,” advised Joanne, who is veterinary adviser with MSD Animal Health.

Protecting against enzootic abortion

Enzootic abortion (EAE) is another serious threat to sheep. Caused by a bacteria-type organism called Chlamydophila abortus, it can result in 30% of sheep aborting.

It is usually caused by infected bought-in replacements, but it can also be spread by wildlife carrying infected placentae from farm to farm.

Unlike toxoplasmosis, it is highly infectious and organisms are passed from ewe to ewe in infected afterbirth, on new lambs and in vaginal discharges for up to three weeks after lambing.

Lambs can also be born already infected from mothers carrying the disease.

“When a ewe aborts she sheds large numbers of organisms, which can infect any in-contact ewe or lamb. These newly infected sheep will not show any signs of infection.

“The organisms remain dormant in the body until late in the next pregnancy when reactivation occurs. In infected lambs, the organism can remain dormant for up to two years.

“Typically, about three weeks before lambing, the placenta becomes inflamed and abortion occurs,” said Joanne Cregg.


She said that while ewes that aborted often continue to have a normal lambing in subsequent years, they are carriers of the disease and may still shed organisms resulting in infection of other sheep and lambs.

“Vaccination will effectively reduce the risk of enzootic abortion as part of a flock health plan. Because there is no test to identify latently infected sheep, it is important to vaccinate all breeding sheep in the first year. After that, only replacements need to be vaccinated,” advised Joanne.

Making a football comeback

Paul McDonald was a member of the Laois team that won the Leinster Senior Football Championship in 2003, the first and only time since 1946 that the county lifted the Delaney Cup.

He also played on the Laois team that won the All-Ireland minor championship in 1997. He won three intermediate county championships with his club Arles-Killeen.

He retired a couple of years ago because of farming and family commitments.

He and his wife Mary Emily, a midwife in Portlaoise hospital, have three children, Jack (9), Aoife (6) and Aaron (2).

However, because of a shortage of players in the club, he was persuaded to make a comeback and, at 37, is back playing senior football with Arles-Killeen this year.

Beef and tillage enterprise

The McDonalds also run a beef and tillage enterprise on the farm at Tankardstown.

They have a herd of 40 suckler cows with all progeny reared to beef. They also buy-in weanlings and stores for fattening.

The tillage enterprise consists of 100 acres of winter and spring barley and winter wheat.

The winter barley was cut in the middle of July and averaged 3.75t/acre. They use their own combine and also cut a couple of hundred acres on contract for neighbours.

Toxo and Enzo vaccination advice

The separate vaccines for toxoplasmosis and enzootic abortion (EAE) can be given to breeding ewes and lambs (from five months of age) during the non-pregnancy season. Vaccination must be completed at least four weeks before sheep go to the ram.

The two vaccines can be administered at the same time, but not mixed, and must be given in separate injection sites. Due to the long lasting immunity induced by both of these vaccines, generally just one shot of each vaccine is required during the lifetime of the ewe*.

*Immunity against enzootic abortion is maintained for at least three years after vaccination and immunity to Toxoplasmosis post-vaccination is maintained for two years and its boosted by natural exposure to the parasite.

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