Once the lameness is well-established the majority of affected animals remain permanently unthrifty despite treatment.The adoption of hygienic conditions at docking and castration will go a long way to eliminating the disease. Lambs appear to have abdominal pain, are reluctant to move and, when they do so, walk with a stilted gait and tucked-up abdomen. The onset of an outbreak is sudden and dramatic with a number of lambs being affected simultaneously. Affected animals have a severe diarrhoea which soils the hindquarters and tail and is followed by the passing of variable amounts of mucus. Deaths from this condition are rare but the lameness can persist for a long time resulting in marked unthriftiness.This form of arthritis usually follows docking and castration when the organism which is present in the soil of particular farms or even particular fields, gains entry through the wounds. If possible a severely affected animal should be post mortemed. Such animals can shortly be found lying in sternal recumbency and appear as if asleep but if disturbed by a noise, they become hyperaesthetic and show twitching of the eyes and ears. Clinically affected sheep die within 3 months after onset of the disease.The disease is spread by the respiratory route after the introduction of clinically normal but infected animals into a susceptible flock. A single drench of a cobalt salt solution is unsatisfactory.Because of the continuous need for cobalt in the diet, attempts must be made to provide this element on a permanent basis.Cobalt can be applied to pasture as a dressing every 3 or 4 years or so depending on the climatic and environmental factors which allow its persistence. A wide range of mammals can become infected and infection can produce a very painful lesion in man.The incubation period depends on the amount of virus introduced and ranges from less than 24 hours to 10 days.Once an outbreak is under way there is little that can be done to control the spread of the disease. Adult sheep brought in from non-louping-ill areas are also susceptible.The disease is spread by the tick vector, Ixodes ricinus. It has clearly defined age and seasonal incidences, occurring in lambs between early May and late June, although some later outbreaks have recently been reported.The small intestinal nematode, Nematodirus battus, whose life cycle is similar to that of the other trichostrongyes, except in one important respect, which is that the egg does not hatch until the larvae is present.Outbreaks of disease occur in lowland flocks from late May until mid-July, the time of onset varying with the locality and the year, and are confined to that season*s lamb crop.
Veterinary examination is very important to diagnose lung abscesses.Figure 12. Where a sufficient degree of grazing control is practised, as in most lowland flocks, treated sheep should be moved to pasture ungrazed by sheep in that grazing season.Control is generally based on strategic use of wormers, often combined with specific grazing management.The most important source of infection for the lamb crop is the periparturient rise in the ewe faecal egg count; prophylaxis will only be efficient if this rise is kept to a minimum.This may be achieved by the use of a ruminal bolus containing albendazole which removes existing infections and provides 100 days protection against reinfection. The situation may become more complicated if secondary infection e.g.
Lambs can be protected by two doses of vaccine administered from 10 days-old as colostral antibody does not interfere with the development of active immunity.
Sheep may be affected by several types of the organism, but the commonest type is probably the same as that causing disease in cattle.Under field conditions the organism is very persistent and can survive on grass for months.Johne*s disease is predominantly a disease of the young adult animal although it may also be observed in older sheep. A condition of sporadic occurrence in sheep due to ingestion of the causal organism Campylobacter fetus or C. jejuni. After the onset of the diarrhoea, deterioration is rapid.Adult sheep frequently carry a worm burden which does not appear to affect their general health provided the animals receive an adequate diet. The earliest clinical sign is often apparent hindleg lameness/stiffness as the ewe tries to protect the painful udder and/or an obviously hungry lamb.
The Ministry of Agriculture have therefore been able to develop a formula for forecasting the likely incidence and severity of fasciolosis based mainly on rainfall figures from the preceding months. Do not feed mouldy areas of silage, feed silage from troughs not from the ground and empty uneaten silage from troughs after 24 hours. Ewes suffering from metritis will look depressed, will not eat, or show interest in her lambs and she will often have a swollen vulva. Affected animals often appear blind as they are unable to avoid walking into objects and frequently bump into anything put in their path.