Livestock
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Plan to avoid abortion
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| Sporadic cases of abortion caused by Bacillus licheniformis can occur in late pregnancy although a small live calf may be born at full-term |
NADIS (National Animal Disease Information Service) is a network of 59 veterinary pracrices and six veterinary colleges monitoring diseases in cattle, sheep and pigs in the UK.
This month Phil Scott DVM&S, DipECBHM, CertCHP, DSHP, FRCVS talks about abortion in cattle
IN UK all abortions, and premature births (before day 271 of gestation) must be reported to DEFRA/SEERAD who will then decide upon the necessary course of action.
The number of abortion enquiries reported by 31 NADIS veterinary practices throughout the UK is very low and probably represent under-reporting of farmers of abortions now that Brucellosis has been eradicated from the UK.
However, complacency can result in serious disease problems and significant financial loss unless the cause(s) of abortion is recognised at the outset of the problem.
Infectious agents causing infertility/abortion may affect one or two individual animals in the herd but often cause widespread problems within a herd. It is very important to remember that many infectious causes of abortion can be transmitted to humans (referred to as zoonotic infections). Young children, pregnant women and the elderly are especially vulnerable to such infections.
Recognition of the problem
Loss of the foetus before three months may not be detected until the cow unexpectedly returns to oestrus. Thereafter, the foetus may be found (Picture 1) but in certain cases, retained foetal membranes may be the only evidence of abortion (Picture 2).
Common causes
Control of infectious bovine rhinotracheitis (IBR) and bovine virus diarrhoea (BVD/MD) is best achieved by either maintenance of a disease-free herd and strict biosecurity or much more commonly by completion of the recommended vaccination programme before heifers and bulls enter the breeding programme.
Bacteria
Campylobacter foetus venerealis can cause abortion. The first sign of a problem is a large number of returns to oestrus following service by the carrier bull; cattle bred by artificial insemination are not affected. Only later may abortions be seen (at 4-7 months of pregnancy).
Brucella abortus
Officially eradicated Britain in 1983 though small outbreaks have occurred since. Typically, abortion occurs during the seventh month of pregnancy. The causal organism can persist for long periods outside the body especially in organic debris. Control measures in the UK include testing all breeding stock over 24 months old (normally every two years) except lactating cows where monthly tests of the bulk milk are performed.
Salmonella
Most salmonellae-induced abortions occur in late pregnancy. In cattle, S. dublin is responsible for 80% of these, usually during the late summer months. The period between ingestion and abortion is around six to eight weeks.
Control measures include isolation of all aborted cows, thorough disposal of products of abortion and disinfection. Vaccination can be considered where S. dublin is a persistent problem.
Listeria monocytogenes
Abortions are seen sporadically during winter months when feeding very poor quality silage (high pH) (Picture 4). Review silage making/feeding practises for future where appropriate.
Bacillus licheniformis
Frequently diagnosed cause of abortion, especially in N W England and Scotland.
Bacillus spp. thrive in mouldy hay, straw, feed, and silage.
Sporadic cases of abortion occur in late pregnancy although a small live calf may be born at term (Picture 3). Control is difficult because the organism is ubiquitous and the condition occurs sporadically. Avoidance of poor quality feed and straw is recommended but rarely practical.
Neospora caninum
This is the most commonly diagnosed cause of bovine abortion in the UK. (12.5% of all abortions investigated). Neospora caninum has a very complicated life cycle where dogs/foxes act as the definitive host with the cow becoming accidentally infected by contact with faeces. Abortion is most common at 5-6 months of pregnancy.
Keep dogs away from calving areas and products of calving, abortion, etc. Don't feed dogs raw meat. Careful disposal of products of abortion/stillbirth to avoid foxes gaining access. There is no vaccine available in UK.
Mycotic (fungal) abortion
In UK the highest incidence is in the West during the winter months and is related to heavy rainfall during haymaking and straw baling. Abortions are usually sporadic, but can involve 10% of herd. Abortion around the seventh month is usual commonly accompanied by placental retention. Control measures include taking care with baling and storing food and bedding, avoidance of contaminated material, improving ventilation, and reducing overcrowding.
Conclusion
Strict biosecurity and disease-free status are over-used phrases often under-achieved at farm level. Only through strict adherence to a comprehensive herd plan can abortion be prevented. Prevention of a single abortion will pay for almost all prevention measures.
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