Farm Animal Medicine and Surgery - Graham R Duncanson

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wet ground in the previous autumn Johne’s disease Adult cows over 3 years of age Infected soon after birth Mucosal disease Yearlings Always persistently infected (PI) Necrotic enteritis Suckler calves up to 4 months Clostridium perfringens type C Parasitic gastroenteritis Yearlings or 2 year olds which have been turned out for the first time At grass in late summer or autumn Rotavirus Calves Neonatal high morbidity, low mortality Type 2 Ostertagia ostertagia Yearlings or 2 year olds which must have been out grazing in the previous late summer or autumn January to March Salmonellosis Cows and calves Salmonella typhimurium in calves, S. dublin in cows and calves

      Diseases of the liver

      • Abscesses are a common finding in the liver of healthy cattle at slaughter (see Chapter 4).

      • Black’s disease (see above).

      • Fasciolisis (see above).

      • Fatty liver syndrome. This is a disease of dairy cows which are too fat at parturition, and their livers cannot cope with the demands of lactation. Treatment is with dexamethasone and glucose by injection iv and orally, in severe cases.

      • Plant toxicity. Toxic plants include: blue-green algae (which contain Cyanobacteria spp.), bog asphodel (Narthecium ossifragum, found on marshy ground and dangerous in hay (Angell and Ross, 2011), fungi containing mycotoxins (mainly aflatoxins), Panicum spp. (grown as a fodder crop in tropical and subtropical areas and dangerous only when fed to excess), ragwort (Senecio jacobea, particularly dangerous to cattle in hay) and St John’s wort (Hypericum perforatum, consumed after ditch clearing).

      • Rift Valley fever (RVF) (mainly a disease of sheep and goats found in Africa, but causes abortion in cattle, see below).

      • Tumours of the liver are rare (they are mainly adenomas or adenocarcinomas).

      Diseases of the pancreas

       Fat necrosis

      The aetiology of this disease is obscure and in the author’s experience it only occurs in the two Channel Island breeds of cattle. Large lumps of hard fat will be felt in the abdomen on rectal examination. The cows do not appear to be ill.

      Diseases of the Neurological System

      These can usefully be divided into three categories: conditions of calves; conditions of adult cattle; and ocular conditions.

      Neurological conditions of calves

       Bacterial meningitis

      The most common isolates are E. coli and Streptococcus spp. The signs are ataxia, hyperaesthesia, neck pain, star gazing, wandering and vocalization. These will lead to recumbency, opisthotonous, convulsions and death. Treatment should be florfenicol 20 mg/kg iv twice daily and intensive nursing.

       Brain abscess

      This is likely to be caused by haematogenous spread of Arcanobacterium pyogenes. Diagnosis may be difficult as the calf will show neurological signs but may not have a raised rectal temperature. The choice of antibiotic is difficult. Trimethropin/sulfadiazine is suggested for a minimum of 10 days, together with NSAIDs.

       Cerebrocortical necrosis (CCN)

      In the author’s experience this is the most common neurological disease of calves in the UK. Calves will appear blind and will wander around aimlessly. Treatment with thiamine, often in combination with other B vitamins, is very effective. The aim should be to give 350 mg thiamine hydrochloride (vitamin B1) daily for 5 days. Ideally, the first dose should be given iv. The disease can be confirmed on post-mortem by observing the fluorescence of the brain under ultraviolet light.

       Femoral nerve damage

      This occurs in large calves which have a difficult parturition and are subjected to large amounts of traction in the final stages of delivery. Atrophy of the quadriceps soon becomes apparent with the calf having difficulty in walking. The prognosis is guarded and related to the severity of the clinical signs. Treatment is with NSAIDs and nursing.

       Lead poisoning

      Fifty years ago this was a common condition as there were still gates and doors painted with lead paint. The condition is rare today. Calves would lick the flaking paint and show acute neurological signs without a pyrexia. Treatment is an iv injection of calcium edetate (EDTA) to act as a chelating solution for the lead ions. This is very effective but should be given for 3 days to remove the lead that may still be in the gastroenteric tract.

       Middle ear infection

      Calves with this condition will have a head tilt, a staggering gait and a raised rectal temperature. If the infection has come from the outer ear, which is the normal manifestation, calves will show pain when the ear is squeezed and the clinician will perceive a crackling on palpation. Several organisms may be involved so a broad-spectrum antibiotic should be give parenterally together with aural antibiotics licensed for dogs. The prognosis is good. However, if the infection has come from a haematogenous spread with no outer ear infection, the prognosis is poor even with prolonged parenteral antibiotics.

       Radial paralysis

      This condition is common, and is usually a result of a calf being trapped in a gate or creep. It can also occur after a kick from a cow. The calf will be fracture lame, but when the leg is placed on the ground it will be able to bear weight on the affected leg without difficulty or pain. The calf should be given NSAIDs to reduce the inflammation but will normally learn to flick the leg forward as it walks and show a total recovery in 6 weeks.

      Neurological conditions of adult cattle

       Aujeszky’s disease

      Often called pseudorabies, this disease has a worldwide distribution but has been eliminated from the UK and many countries in western Europe. It is caused by a herpesvi-rus whose primary host is the pig. The main signs are intense pruritis, depression and lethargy. Diagnosis is from virus isolation and paired serum samples. There is no treatment. The disease is notifiable in the UK.

       Bovine spongiform encephalopathy (BSE)

      This condition was first diagnosed in the UK in 1986. It has been found in Europe, the Middle East, Japan, the USA and Canada. Cows become infected by eating infectious proteins in cattle feed contaminated from animal sources. Horizontal transmission is of minor importance. The incubation

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