Listeria Infections

Listeria monocytogenese is a bacterial infection that multiplies in the soil. It is found in plant material and the faeces of ruminants where it can become concentrated and overwhelm the defense mechanisms of some individuals if they are forced to eat contaminated feed. The listeria bacteria can multiply readily at low temperatures, but it will not grow in acid conditions where the pH falls below 5. It should not be a problem if you feed well made pit silage. Baled silage is more of a problem as it is difficult to exclude air completely through out the bale and there is likely to be contamination at the edges. The infection manifests itself in several ways and can be terminal if it is not treated promptly. If the immune system of the host animal is overwhelmed the infection will develop in the blood stream and result in either paralysis of some of the facial muscles or more seriously meningitis.

If this happens the membranes that surround the brain become inflamed and the front part will get compressed. Individuals with meningitis will often press their head up against the wall of a building or a solid object, they will loose some or all of their vision and may stand alone as they will not be aware of the where their companions are. Animals that are heavily pregnant when first infected may abort. Because listeria is essentially a soil organism it responds readily to most antibiotics, high doses are needed initially to get therapeutic levels of a drug into the brain. Oxytetra cycline in an elevated dose does work against this disease but we often find that crystalline penicillin works better initially as it can be given straight into the blood stream.

Eye Infections

This is the same bacteria that will cause a cloudy, very inflamed eye in cattle of all ages fed on baled silage. Here the bacteria get established on the surface of the eye and will cause a painful ulcer before the infection spreads to the eye itself. These eyes look terrible because of the way they react to this infection. They will normally respond to antibiotics and anti inflammatory drugs injected into the outer surface. Cattle with silage eye must develop some sort immunity to the infection as it is un usual to find an animal that gets a subsequent infection to either the same or the other eye. It is always difficult to decide what to do with silage that seems to be contaminated with listeria as normally you would be reluctant to dump it. Certainly sheep seem to be sensitive to this disease and they will abort if they are pregnant so the best compromise would be to feed it to store cattle and treat any infected eyes or animals that are in the early stages of meningitis promptly.

Orf Infections

Have you seen cases of Orf in your sheep in the past month? Most cases occur in the spring and can be serious for young lambs if the infection gets inside their mouths. At this time of the year Orf flares up if the lips of the sheep are damaged by the fodder they eat. There are a lot of thistles about at the moment that can take the infection deep into the skin and make it difficult to treat. Orf is a nuisance, particularly if you want to sell animals at this time of the year. If possible you should carefully inspect the mouths and teats of any breeding sheep that you buy in as sometimes the scabs can be quite small and seem innocuous until the incomers are mixed with animals that have never had the infection before. If you only have a few animals with symptoms the Orfoid capsules still seem to work well as long as you can give them without exposing your fingers to the infection. For breeding animals, and if you notice small scabs on brought in animals, it is far better to vaccinate the whole flock so that all of the ewes will be immune before the first lambs arrive next year. Recently we have seen a serious out break of Orf in a small goat herd and it is not apparent where the infection came from as no new animals have been added to the herd for some time.

Pasturella Infections

The most common cause of pneumonia in sheep is Pasteurella multocida. Pneumonia is one of the most common respiratory problems in small ruminants throughout the world. Although pneumonia often occurs in lambs, illness and deaths also occur in adult animals. Pneumonia occurs when infectious and non-infectious agents cause the lungs of sheep to become inflamed. The most frequent cause of respiratory infection and death is Pasteurella multocida. The bacteria are commonly found in the upper respiratory tract of healthy sheep. The infections are subdivided in two groups, A and T. Type A is most prevalent and is associated with severe pneumonia. Sheep that survive the acute stage may recover or become chronically infected with reduced lung capacity. Pneumonia caused by P. multocida can lead to significantly decreased growth performance. Transportation stress, viral infections, lung parasites, prior bacterial infections, overcrowded pens, poor housing conditions and sudden environmental changes increase susceptibility to P. multocida. At this time of the year acute disease occurs after a pasture change when sheep are turned onto better grazing. Pasturella is the main cause of sudden death after a pasture change. If you have this problem in animals that have not been vaccinated the best thing to do is to move them back to poorer grazing and inject any individuals with respiratory symptoms with long acting oxytetra cycline. Care must be taken not to stress the flock when the treatments are given.

Coping with Fluke

Ten years ago it was unusual here to get losses from fluke. Now after a series of wet summers it has become common place in both sheep and cattle. Faciola hepatica has a complicated life cycle that involves a small snail in the summer months. In the past that has been the way to tackle the problem, if it was possible to control the snail by taking away its wet habitat the life cycle of the fluke was blocked so it could not cause problems to its animal host in the winter. In the past you were encouraged to drain wet areas and fence off ditches, now environmental schemes have moved in the other direction and this has made it more difficult to cope with fluke. Fortunately there are better drugs now that can be used for fluke control by either injection, pour on or drench so it is easier to treat. At the moment the larval stages will be starting to move towards the liver and you will need to start treatments on farms that have heavy infestations of fluke. On some farms you may be able to keep on top of things if you give a single treatment in January. Fluke can be a hidden problem, try to get feedback from abattoirs and use treatments in the winter if you are getting reports of livers being rejected at meat inspection. There are blood and bulk milk tests that can help with monitoring this parasite.

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