Download Vital To Establish The Causes Of Sheep Aborting

Vital To Establish The Causes Of Sheep Aborting
Veterinary practitioner and Sligo sheep farmer Ronan Gallagher has direct experience
of the devastating impact of an abortion outbreak caused by either toxoplasmosis or
enzootic abortion (EAE).
“Last year, I dealt with a 500-ewe flock which had an outbreak of enzootic abortion.
Sixty ewes aborted, leading to the loss of 100 lambs. All the ewes that aborted were
culled and a strict vaccination programme for both enzootic abortion and
toxoplasmosis is now in place,” he said.
Problems with toxoplasmosis five years ago led Ronan to introduce vaccination of his
own flock at Carrowcarden, Enniscrone.
A well-known pedigree Texel breeder, his Enniscrone Texels consists of 60 pedigree
Texel ewes and 100 commercial ewes, which are used to carry embryos. His plan is to
produce 90% of his pedigree stock through embryo transfer within the next few years.
Currently, the split between “natural” and embryo transfer is 50/50.
“I vaccinated the entire flock for toxoplasmosis and enzootic abortion the first year.
After that, just the replacements are vaccinated at least a month before they are mated.
The one shot of both vaccines generally gives lifetime protection,” he said.
He has noticed that abortion problems are becoming more common in recent years. “It
is not spoken about very much but it is definitely becoming a bigger issue.”
“My advice to farmers is to always investigate the reasons for abortions. Contact your
veterinary practitioner who will arrange for swabs to be sent to FarmLab Diagnostics
in Elphin and for foetuses and placentae to be sent to the regional veterinary
laboratory,” he said.
Ronan is a member of the recently established expert working group on sheep
abortion. It consists of Teagasc specialists, veterinary practitioners and representatives
from industry including MSD Animal Health.
As well as running his pedigree sheep business, he is a veterinary practitioner with
Kilbride Veterinary Clinic in Swinford. Through his company ProStar Genetics, he
also provides a nationwide sheep AI, embryo transfer and ram testing service.
Advice on vaccination
The one-shot 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. Generally, just one shot of each vaccine is required
during the lifetime of the ewe. It is important to get veterinary advice on the most
appropriate vaccination strategy for your farm.
Toxoplasmosis a leading cause
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“As well as weak and sickly lambs that die soon after birth, many farmers also accept
barren ewes, leading to cumulative abortion rates of up to 10%. However, anything
above two percent is likely to be due to an infectious cause and should be
investigated,” said Sharon Magnier (pictured), veterinary adviser with MSD Animal
Health.
“Lambing time offers an ideal opportunity to establish the cause of losses.” She said
analysis by regional veterinary laboratories shows toxoplasmosis and enzootic
abortion (EAE) to be the leading causes of abortion in sheep.
“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 100 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,” she
added.
Symptoms of toxoplasmosis can include barren sheep, abortions, stillbirths, weakly
lambs and mummified foetuses. While heavy infections, typically in smaller groups of
sheep, can cause infertility in half or more of the flock, the impact is normally less
dramatic, with the number of lambs lost at around six percent. The disease is not
passed from sheep to sheep.
Sharon Magnier said that vaccination is the only way to effectively build uniform
immunity to toxoplasmosis in the flock. As older ewes are more likely than younger
ewes to have already been in contact with T. gondii, it may be an option to vaccinate
the younger sheep and then vaccinate all replacements as they enter 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,” said Sharon.
Enzootic abortion highly infectious
An outbreak of enzootic abortion (EAE), caused by a bacteria-type organism called
Chlamydophila abortus, can result in 30% of sheep aborting. The disease 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.
Sharon Magnier explained that 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.
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“The organisms remain dormant in the body until the ewe lambs again. In infected
lambs, they can remain dormant for up to two years. About three weeks before
lambing, the placenta becomes inflamed and abortion occurs,” she said.
“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,” she added.
Where enzootic abortion is diagnosed, she stressed the importance of keeping aborted
ewes separate from the rest of the flock and not fostering lambs on to aborted ewes.
She advised farmers to discuss the use of an antibiotic injection with their vet. It may
not stop the outbreak but may reduce the number of abortions in the current season.
“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,” she advised.
Use medicines responsibly
For further information, please contact your veterinary prescriber, the product SPC or
MSD Animal Health, Red Oak North, South County Business Park, Leopardstown,
Dublin 18.
Tel: +353 1 2970220. Email: [email protected];
(Source – Irish Farmers Journal - MSD Animal Health – 01/03/2017)
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