John A. Smart B.V.Sc
Clutha Vets Animal Health Centre
P.O. Box 231 Balclutha
There are a number of management practices farmers can carry out, which will reduce the chances of S.Brandenburg occurring on their property. These include:
1. Avoid where possible the purchase and/or grazing of stock from known affected farms as there will almost certainly be a small percentage of the stock carrying the organism but not actually showing symptoms. However be aware that supposedly unaffected farms can harbour the bacteria. The purchase of bobby calves from known affected areas should be avoided.
An exception to the above is the purchase of stud rams. Because of the low numbers involved (usually 1 - 6 animals) and the timing (January — February period) the chances of importing the Brandenburg organism, while not absent are certainly extremely low. The pros & cons of the right genetics for you versus the very small chance of importing S.Brandenburg need to be weighed up.
2. Vaccination - A vaccination programme using Salvexin + B (Schering Plough) can be set up. This involves vaccinating all breeding stock twice in the first year, the doses being given at 4 - 6 week intervals with the second dose occurring about four weeks prior to the main challenge period, which appears to start about the end of June, i.e. the second dose should be given by the end of May. In subsequent years all new stock will require two doses and all existing ewes will require one booster dose, again given by the end of May. There is some evidence that later vaccination (June onwards) is less effective. Vaccination should be avoided in the week prior to the rams going out.
Because vaccination is not 100% effective it is important that the “peripheral” factors surrounding the use of the vaccine are as ideal as possible. These include:
a) Correct timing – not too early – not too late.
b) No concurrent vaccinations – the mounting of an immune response to vaccination requires quite a bit of energy and it has been shown (with Yersiniavax in deer) that two vaccines given at the same time reduces the immune response to either.
c) Keep the vaccinating as “stress” free as possible – nutritional stress is probably the most important in this context.
The risk in pregnant hoggets appears much reduced so it is less important to vaccinate these.
Vaccination will result in: -
· A reduction in abortions and ewe deaths.
· A reduction in environmental contamination with the Brandenburg organism resulting in less risk of spread to other properties and less cross contamination occurring at freezing works.
3. Reduction in stocking density - Mob stocking systems through winter, while they usually result in good nutrition for the ewes, do carry an increased risk if there is a contagious disease such as S.Brandenburg going round. While not always desirable the more spread out you can graze your ewes the better from a contagious disease point of view.
4. Maintain adequate nutrition - Ewes not under nutritional stress are more likely to withstand infectious challenge. Draft off thin ewes and feed preferentially.
5. Minimise the time ewes are in yards — bring smaller groups in at a time. This will also result in less risk of metabolic problems in pregnant ewes.
6. Dampen down yards prior to yarding if they are dusty. S.Brandenburg has been isolated from yard dust many months after an outbreak and has also been isolated from yard dust on farms where there has thought to be no cases of Brandenburg. Salmonella has been shown in sheep to spread by inhalation – a lower dose is required to set up infection than with the oral route.
7. Ensure all stock have access to a fresh clean source of drinking water.
8. Should other farms in your locality become infected with S.Brandenburg, then during the disease occurrence (July – Sept) all visitors vehicles should stay in your farmyard and visitors footwear should be disinfected before going on to your property. The same would apply to sheep scanners equipment etc.
Treatment/Control: - i.e. limit its effects when it has occurred
If you are unfortunate enough to have an outbreak of S.Brandenburg abortions and deaths occur on your farm the following measures should help to reduce the severity of the outbreak.
1. Rapid disposal of aborted foetuses and placenta by burial. This is most important as black backed gulls and hawks can accelerate the spread of the organism to other mobs and neighbouring farms.
2. Pour disinfectant over the exact area where aborted foetuses and placenta were lying. Note that not all disinfectants are equal — some are inactivated in the presence of organic matter, e.g. faeces, blood, dirt. The best general-purpose farm disinfectants for this purpose are the quaternary ammonium compounds e.g. Varicide. See your vet clinic for advice here.
3. Rapid isolation of aborted ewes into a separate mob since these will be discharging millions of bacteria amongst other ewes.
4. Spread out affected mobs as far and wide as you can practically get away with.
5. Limit pre-lamb yardings to the absolute minimum in terms of number and length of time in the yards. One aborting ewe in a confined space has the potential to infect many others.
6. Control scavengers. These include black backed gulls, hawks and your own dogs. A dead gull or two left lying around often deters other gulls.
7. If only some mobs are affected go from unaffected to affected mobs on your daily rounds and then clean/water blast your vehicle tyres, wheel wells, farm bike trailer etc. Again use a disinfectant effective with high organic contamination.
8. Regarding antibiotic use to treat ewes suffering from S.Brandenburg there are pros and cons associated with this. While antibiotic treatment if given in time can markedly increase the survival rate of affected ewes, this treatment:
a) Can result in an increase in the carrier state, i.e. ewes carrying and shedding the organism but not actually showing any symptoms.
b) Has the potential to result in an increased incidence of antibiotic resistance.
The use or otherwise of antibiotics should be discussed with your local veterinarian. Note that penicillin is not effective against Salmonella infections.
S.Brandenburg (along with all Salmonella) have the potential to infect humans (i.e. they are a zoonosis) and cause a very nasty and debilitating illness. To reduce the chances of human infection if you have Brandenburg abortions occurring on your farm:
1. Use disposable gloves when handling any aborted material or lambing any suspect ewe. These are available at all vet clinics.
2. Avoid putting fingers, dog whistles etc. anywhere near your mouth until washed in disinfectant.
3. Wash hands in disinfectant prior to every meal.
4. Don’t bring contaminated clothing / footwear indoors.
5. Clean and disinfect your boots.
6. No smoking (at least until your hands are clean but preferably never again — you should live longer as a result!!)
7. Take care with young children with respect to exposing them to potentially contaminated material - they are particularly susceptible.
Prevention Of Freezing Works Contamination:
S.Brandenburg can cause contamination problems at freezing works and thus poses a risk to our meat export trade. If you have had the disease on your property, then to reduce the chances of cross contamination at the works:
1. Dampen down dusty yards prior to yarding. S.Brandenburg has been isolated from wool so damping down will reduce wool contamination from Salmonella in shed dust.
2. Ensure stock are clean - crutch if necessary.
3. Again minimise time in yards as much as possible.
4. Keep yarding stress on stock as low as possible, i.e. reasonable handling, avoid excessive dog use etc. Any stress can result in increased shedding of Salmonella organisms by carrier animals.
5. When sending cull ewes to the works that have survived a bout of Brandenburg earlier on, there are some precautions in addition to those already listed above. These include:
a) Keep these stock on the farm for as long as practically possible before sending to the works. Ideally these cull ewes should be kept until at least February. The longer the interval from disease occurrence to slaughter the less the chance of cross contamination. The meat regulations state that stock that has been in contact during the previous four weeks with stock affected with clinical Salmonellosis shall not be sent to the works, however as stated above a longer interval is necessary to reduce the contamination problem and waiting until February of each year would be desirable.
b) Shear surviving affected ewes prior to going to the works. This will reduce the potential for Salmonella contamination of the wool.
c) Notify the works buyer of these ewes status so they can take appropriate measures at the works.
Note that a, b and c above apply only to surviving ewes that were actually clinically affected by S.Brandenburg themselves, not necessarily to other ewes from the mob being culled for other reasons, age etc.
For more information on Salmonella Brandenburg, especially the incidence in your locality, please contact your local Veterinary Clinic – they will be happy to provide advice on this problem.
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