Health Problems and Diseases that are of Particular Importance for Persian Breeders
Worms. Worms are the most common cause of disease in Australia in sheep. There are 4 common types of nematode worms found in sheep in Australia. In these common types, adults live in the digestive tract of sheep. These adults release eggs that are passed in the sheep droppings. After a period of time- usually days to weeks, on the pasture, the eggs become infective and if then ingested by sheep while grazing are able to hatch in the digestive tract. The larvae that hatch from the eggs eventually mature to adult worms that in turn produce further eggs that are then passed in the droppings. In this way there is ongoing contamination of the pasture with fresh worm eggs. And the number passed can be amazing. Sometimes 10, 000 or more can be found in a single teaspoon of droppings. Worms compromise health by interfering with the bowel and stomach’s ability to efficiently absorb and assimilate nutrients and also by damaging the bowel and stomach lining that can then bleed and leak tissue protein. All sheep on pasture have worms. Symptoms vary depending on the type of worm and the severity of infection. Sometimes the sheep may just be failing to thrive. Often the main symptom is diarrhoea , for example with Trichostrongylus (or black scour worm). Sometimes, however there may be no diarrhea as is the case with Haemonchus (or Barbers Pole worm ) where bleeding from internal stomach ulcers leads to pale gums, general weakness and swelling in the legs and jaw. Even if worms are not the beginning and end of a problem they often are part of a problem and should always be considered when sheep appear weak, are thin or simply failing to thrive or have diarrhea. Your sheep veterinarian can examine your sheep droppings and tell you what type of worms are there and how many there are present.
Often what happens , particularly in low stocking and pet situations is that growing sheep are exposed to low numbers of worms as they mature. This ongoing low grade exposure may not lead to disease but allows the developing sheep to build up a natural immunity to the parasites. Disease comes either through high exposure or rather an exposure than the animals immune system cannot handle or if there is an error in the flocks management that weakens the animal and makes it more vulnerable to disease generally. This error most commonly is poor nutrition, however anything that weakens a sheep such as persistent cold or damp conditions may be involved.
When worms are a problem the immediate thing to do is worm the sheep. This however is likely to provide only a short term solution as sheep placed back on the same pasture will immediatey become reinfected and as the life cycle of most worms is completed in several weeks this means that within this time the sheep will once again be unwell.
Effective control of worms requires planning. To some extent the fact that sheep develop disease associated with worms means that inadequate planning has taken place. The first thing to do is to make sure that the sheep are generally well cared for so they are at their best to resist disease generally. The next thing is to decrease exposure to worm eggs principally through pasture rotation. What this means is that rather than letting sheep graze over an entire area, access to certain paddocks should be prevented at certain times. Doing this means that many of the worm eggs will die before there are sheep grazing again on that area. In this way potential for re-exposure and re- infection is reduced. Rotating every 6 weeks or more is often best and practical. The third thing is to strategically worm the sheep. Simply worming sheep again and again can actually be harmful. It encourages the development of worms that are resistant to worm medication and can fail to allow for the low grade ongoing exposure required for sheep to develop immunity to the worms. During hot dry conditions most worm eggs only survive on pasture for about 6 weeks. During cooler , wet times eggs can survive for many months. Recommended worming protocols vary from area to area but in the high rainfall area of southern Victoria, where I live, it is much more effective to give one or two drenches during our hot Summer usually about 6 weeks apart. Because of the hot, dry conditions at this time , most eggs on the pasture have died leading to a low re-infection rate and prolonged benefit. Lactating ewes pass large numbers of eggs and can expose their lambs to high levels of infection. Sometimes worming ewes during pregnancy can therefore also be beneficial. Effective worm control can be complex. Your local sheep vet will be able to advise what is best in your area.
Footrot and Scald Any sheep that is seen to be limping should be considered to have either footrot or scald until proven otherwise. These problems are common and can be difficult, if not impossible to eradicate from a property once present. Both diseases are caused by the same organism, a bacteria called Dichelobacter nodosus. There are many types (or serotypes ) of Dichelobacter and the disease which they cause ranges from severe to mild. In mild forms (called Scald) the area between the cleats (ie the sheep toes) become red ,swollen and can start to discharge. In the most severe forms (called Footrot) the infection caused by the bacteria extends between the outer hoof and flesh of the toe lifting the hoof away from the underlying structures. The hoof can separate and be lost. Animals with scald tend to remain in good condition but just limp. However as the severity of the infection increases so does the pain and more severely affected animals are reluctant to graze and loose condition. Dichelobacter is readily killed by dry heat, sunlight, cold and a dry environment. This means that in flocks with footrot bacteria present lameness is more likely to be noticed during the wetter times of year where conditions favour the growth of the organism. The incidence of lameness naturally reduces through the hot dry times of the year and even though the animals are not lame then , this is in fact the time to attempt to eradicate the disease.
Dichelobacter can only survive in 2 places , either on the pasture or on the sheep’s foot. Control aims to kill the organism in both of these areas. Dichelobacter can only survive on pasture for 14 days. This means that simply spelling a paddock by not allowing sheep to graze on it for 14 days results in eradication of Dichelobacter from that paddock. To eradicate Dichelobacter from a sheep’s foot however is much harder. There are however 4 common methods available. 1/ Dichelobacter likes the warm, moist nooks and crannies found in sheep feet. Trimming of overgrown cleats and removal of separated horn material is imperative to remove areas that the bacteria can survive in 2/Foot bathing- foot baths are prepared by diluting astringent/ antiseptic agents such as zinc sulphate in foot baths. Sheep ideally should stand in the bath for at least 20 seconds or alternatively the bath should be sufficiently long so that it takes the sheep at least 20 seconds to walk through it. About 20 meters is adequate. This can be done daily as required 3/ Antibiotics – individual sheep of value and severely affected sheep can be given antibiotics. Usually long acting injections that last for 3 days are given. These are repeated on a needs basis. Your local sheep vet will be able to advise here 4/ Vaccination – Dichelobacter vaccine has only become available recently and it has been a ‘game changer”. After vaccination antibodies produced as a result of the vaccination inhibit Dichelobacter invading the soft tissues of the foot. Vaccination by itself will not work but combined with the above measures is a great help. Different strains of Dichelobacter occur on every property. It is important that the ones on your property are identified so that the vaccine can be specifically prepared against these. To do this either your local vet or you, under veterinary guidance, will need to collect swabs from the feet of your sheep. These are forwarded to Sydney University where the type(s) of Dichelobacter present are identified. Once known these results are forwarded to the vaccine manufacturer ( Treidlia Biovet ) in Sydney where the vaccine is made. This may sound complex and expensive but it is not and in my opinion well worth it. Once the vaccine is prepared each sheep is vaccinated by an injection under the skin. A second injection can be given several weeks later if indicated.
Johne’s Disease. Johne’s is the disease that you don’t want to have. Uncommon 30 years ago it has now become one of the most prevalent diseases in some areas of Australia. Caused by the microorganism, Mycobacteria paratuberculosis it is passed in the droppings of sheep and contaminates the soil and indeed anything that comes in contact with droppings from infected sheep. When ingested during grazing it invades the bowel wall causing thickening and scarring. As this process progresses the bowel become increasingly non- functional, losing its ability to digest food and absorb nutrients. The result is that an infected sheep progressively wastes. Diarrhoea sometimes occurs and in hair breeds such as the Persian a “bottle jaw” becomes visible as a result of fluid developing below the jaw due to the associated hypoproteinaemia ( low protein in the blood ) . Eventually animals become too weak to graze and collapse in the paddock and die. There is no treatment.
Control focuses primarily on vaccination. The vaccine will stop sheep that do not have Johne’s from catching the disease in about 95% of cases. If sheep already have the disease it will not treat them, (although if the vaccine is given to sheep that are already infected it does appear to slow the progression of the disease in some cases). Lambs born into a contaminated environment are vulnerable to infection and the aim is to give the vaccine as young as possible (but old enough for the vaccine to work) and hopefully before the lamb is infected. The recommendation is that lambs are vaccinated as soon as possible after 4 weeks of age. A single vaccination confers life time immunity. Lambs vaccinated in this way are classified as approved vaccinates and can be ear tagged with approved vaccinate NLIS ear tags which are embossed with a large V.
The time to vaccinate against Johne’s is before the disease gets onto the farm. Once there are sick sheep and deaths many of the sheep will already be infected. The effect on the flock can be catastrophic. If the disease is already on the property then vaccinating the lambs at 4 weeks of age each year will see a gradual reduction in clinical disease as the older sheep die or are culled and the majority of lambs each year are approved vaccinates and develop protective immunity. To eradicate the disease, if indeed this is possible, is likely to take many years.
Ovine Brucellosis Brucellosis is a bacterial infection of the genital tract in sheep. It is spread from ram to ewe and from ewe to ram through mating and also from ram to ram through sodomy. Caused by the bacteria Brucella ovis, in rams the bacteria damages the testes and epididymus leading to palpable lumps and other abnormalities within the scrotum and causing either a reduction in fertility or sterility. In ewes infection of the uterus can lead to abortion. The significance of the disease is the reduced conception rate and also the loss of lambs that are conceived through abortion. Ewes do not carry the infection from one Spring to another and so simply not breeding from them for 12 months means that they will be clear of the infection. It is the rams that are the long term carriers of the disease and infected rams infect ewes and other rams. In some parts of Australia, for example the Mallee in Victoria, the disease is common. Your sheep vet can test rams through physical palpation of scrotal contents, examination of semen and through a blood test that checks for exposure to the disease. Preventative measures include only sourcing rams from OB free flocks, having a sheep veterinarian examine and test rams prior to entry and having good boundary fences. If present on a property the aim should be to eradicate the disease. This can be achieved through a protocol involving examination, blood testing and culling of positive animals. Dermo Dermo is a bacterial infection of the skin caused by the bacteria Dermatophilus congolensis. Clinically affected Persians develop flat , grey , crusty plaques on the face and ears. Dermo does not readily become established on dry healthy skin. For infection to occur the waxy layer on the skin must be broken. In Persians this occurs if the skin remains wet for 3 or more consecutive days so it becomes macerated. Most dermo infections start during winter with skin damage due to persistent wetting. Most affected animals are weaners and it tends to be the less robust animals that are more susceptible. Most infections self resolve with time and the start of warm dry weather. If necessary antibiotics , as prescribed by you local vet can be used to treat the more severely affected individuals.
Young Persian with “Dermo”
General Health and Disease Guide “ Sheep Diseases, The Farmers Guide”. An extremely useful summary of sheep health issues written for the farmer can be found on line titled “ Sheep Diseases, The Farmers Guide”. Originally produced by PIRSA in South Australia, it is written by Dr Tony Brightling, a sheep veterinarian and author of the book “Sheep Diseases” . It is an extremely useful and practical reference written in straightforward language and gives practical advice. As always your local sheep veterinarian and DPI office are the best people to contact when health issues arise.