How to deal with Toxoplasmosis abortion
Three mistakes are often made when ewes abort: Failure to quickly isolate aborted ewe(s) & potentially infectious material; Failure to clearly identify the cause of abortion; Failure to put in place prevention methods; Edward Egan, Teagasc Advisor, Co. Meath has advice on dealing with Toxoplasmosis
If abortion levels in your flock are greater than 2% then you need to find out why. Toxoplasmosis (Toxo for short) is one of the most common causes of infectious abortion. Problems due to Toxo involve embryo/foetal loss, barrenness, late lambers, late abortions, weak lambs & the most sickening job of lambing - helping a ewe to lamb rotten lambs.
How are ewes infected?
Toxo is “not” spread from sheep-to-sheep. Young cats spread it to sheep. The young cat first becomes infected from eating an infected mouse or bird (mice or birds do not spread Toxo to sheep). The infected young cat then spreads the disease to sheep by dunging in meal, fodder, straw, water or pasture. The infected cat remains infectious for a week or so after which it develops life long immunity & no longer spreads Toxo while it is healthy.
How does Toxo affect your ewes?
The time the ewe is infected decides how she is affected and what the farmer sees. The infection of a non-pregnant ewe results in immunity within 4 weeks of first infection. Infection in early–pregnancy results in embryo loss without visible signs. These ewes will return to the ram & lamb late or appear barren if the ram has been removed.
The most common time of infection is mid-pregnancy as ewes are coming in contact with infection in meal, straw, housing or fodder. If ewes are infected in mid-pregnancy they abort 45 days later i.e. late-pregnancy.
Infection in mid to late pregnancy results in affected ewes lambing a few days early. A large % of lambs although outwardly normal, will be still–born & sometimes accompanied by a small mummified chocolate brown lamb. Twin lambs may be very uneven in size, one being smaller & less developed than the other. In addition, a proportion of the lambs born alive will be weak & die within the first few days of life, despite your best efforts. Such lambs have brain damage. Another common form of late abortion is a high incidence of one live lamb born with a dead lamb. Mummification & leathery or white spotted placenta is an important indication of Toxo abortion.
Standard procedure for dealing with “all” aborted ewes
7 key steps to dealing with any aborted ewes.
- Abortions should “always” be considered infectious until otherwise proven. Act fast.
- Isolate & permanently mark the ewe as blood samples maybe taken later.
- Remove aborted lambs & cleanings. Adequately disinfect after inspecting aborted ewes or dealing with infected material.
- Contact your vet for advice.
- Collect samples of the foetus/lamb & cleanings, & arrange testing through your vet.
- Carefully dispose of bedding & all other infected materials.
- Once the cause has been identified, consult your vet for the best control methods.
Toxoplasmosis is a serious treat to the unborn child if the mother is infected while pregnant. Pregnant women or those of child bearing age should avoid all contact with lambing ewes, lambing sheds & lambing clothes.
Standard diagnosis procedure
Farmers often remark they sent a dead lamb to the lab but did not get a clear result. There are 5 key steps to improve your chances of clearly identifying the cause.
- Send 3-4 fresh samples rather than just 1 to the Regional Veterinary Lab in clean bags.
- Samples should be as “fresh” as possible. Sending off cleanings or a lamb that has been lying around for a few days reduces the likelihood of a clear result & you will still be charged for it.
- Cleanings from aborted ewes should also be sent to the lab. The tendency among farmers who do send in aborted lambs is to keep the cleanings. Cleanings can play an important role in identifying the type of abortion.
- Vaginal discharge & ewe blood samples maybe useful. However blood sample results can be difficult to interpret. They can show infection occurred but not when. Toxo antibodies persist for several years & often remain high into the following breeding season.
- A copy of the test results are sent to your vet & not to the farmer. Consult your vet about the best control methods based on the results.
A PCR test can also help diagnose the abortion agent. For more advice consult your vet.
Removing all cats is not completely successful as a control method. You may only be making room for new young cats to move in, particularly if you’re near a town. Also infected dropping from removed cats can remain infectious for up to 2 years. Neutering the existing farm cats helps reduce the risk of infection as it allows an aged population of cats to develop on the farm. These older neutered cats will keep out strays & avoid kittens. Ideally feed stores should be cat proof. However cat droppings on hay, silage or bedding can also cause infection.
Mixing ewes – no advantage
There is “no” advantage in placing non-pregnant ewe hogget’s or two-tooth’s ewe where Toxo abortion have occurred in the hope of inoculating them as Toxo is not spread from sheep-to-sheep. Ewes that abort due to Toxo can be kept for future breeding as they have life long immunity & do not spread this disease.
Vaccinating to prevent Toxo
A vaccine is available. One injection usually gives life long protection. Generally it is only necessary to vaccinate replacements. However this will depend on the type of outbreak, so consult your vet for the best advice. The ewes most at risk are those replacement ewe lambs or hogget ewes joining the breeding flock for the first time. Because they are the most at risk the greatest financial return will be gained from vaccinating them. If you’re using Toxovax, you must give this vaccine at least 3 weeks before mating starts. Always follow the product label.
Other infectious abortions
Remember there are other important but less common causes of infectious abortion.
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