Veterinary Services

Nutritional and metabolic disorders

Cobalt deficiency was diagnosed in two groups of young cattle at grass in the far north of Scotland as the serum vitamin B12 levels were below the minimum assay level. It is accepted that the results of vitamin B12 assays in cattle have to be interpreted with caution because of variable binding of the vitamin in bovine blood. However, if the mean vitamin B12 level falls below 54ng/l for a group, as in this case, cobalt supplementation can be justified. Following treatment, rapid improvement in appetite and general demeanor was evident. In the north of Scotland this year many cattle were still being fed conserved food at the beginning of July with variable levels of vitamin and mineral supplementation.

Generalised and systemic conditions

A number of calves aged up to 21 days were presented as sudden deaths to the Thurso Centre this month. In one case of navel ill, Listeria monocytogenes was cultured from the navel and liver. It transpired that the cows were calving in an area where old silage, hay and straw had been dumped and this was considered to be the likely source of infection.

Bacillus licheniformis was isolated from two calves which died within the first five days of life. The organism was isolated from lung and liver in both cases and infection was presumably acquired in utero, the dams still receiving winter-feed of dubious value in June and early July.

A range of clostridial diseases were diagnosed at the Ayr Centre this month. Sudden death in a dairy heifer calf within 30 hours of birth was suspected to be due to clostridial infection at necropsy. Histopathology of the intestine confirmed clostridial enteritis and abomasitis. Both Clostridium septicum and C sordellii were demonstrated by fluorescent antibody testing (FAT) in abomasal and intestinal lesions. Tissue hypoxia following dystokia may have been a contributory factor.

The "cardiac form" of blackleg due to Clostridium chauvoei was confirmed in a six-month-old suckled calf at grass, the second sudden death in one week in a group of 50 suckler cows and calves. The only gross lesions detected were fibrinous pericarditis and splenomegaly.

A nine-month-old heifer in Argyllshire showed central nervous signs (including a high stepping gait and incoordination), and pyrexia prior to death within 24 hours. Neuropathology revealed changes consistent with enterotoxaemia due to Clostridium perfringens type D.

A neonatal Charolais calf, one of two casualties, was submitted for post mortem examination from a herd in Ross-shire The calf had been bright and standing, but was seen to be fitting shortly before it died, at less than twenty-four hours old. There was no evidence that the calf had sucked and the cerebellum appeared to be swollen. On neuropathological examination the brain was found to have very severe, extensive focal symmetrical encephalomalacia (fse) affecting the internal capsule, midbrain and pons with meningeal and perivascular serum leakage. The lesion was consistent with that caused by the epsilon toxin of Clostridium perfringens type D, considered unusual in a calf less than 24 hours old at the time of death.

During a five-day period in mid July at least 15 cattle of all ages died due to lightning strike in Caithness. Animals examined post mortem showed classical signs of internal burn injuries and no evidence of other causes of sudden death such as blackleg or hypomagnesaemia.

Respiratory tract conditions

An increased number of outbreaks of infectious bovine rhinotracheitis (IBR) due to herpes virus type 1 (BHV1) and the start of the expected seasonal increase in outbreaks of parasitic bronchitis (husk) were recorded this month. A first lactation Holstein cow which presented with severe tachypnoea, dyspnoea, pyrexia, anorexia and milk drop was examined at the Dumfries Centre. Sporadic milk drop with respiratory signs was reported in the herd over the previous 1-2 months with small numbers of cows affected at any one time. Post mortem examination identified severe muco-purulent, necrotising tracheitis, plus concurrent lungworm infection, fasciolosis and abomasal lesions consistent with type 1 ostertagiosis. Although FAT for IBR proved negative on tracheal samples (presumably due to the severe necrosis), BHV1 was isolated from the trachea and spleen suggesting systemic viraemia. The cow had been recently purchased and was the most severely affected with other cases recovering under veterinary treatment. It was considered likely that this cow had no immunity to BHV1 prior to entry to the herd and the change in herd management systems may have increased susceptibility to parasitic infection.

Mastitis

A summary of mastitis diagnoses for SAC Veterinary Services from 1996- 2004 is shown in figure 1 (click on PDF link in right hand column), illustrating the increasing importance of Streptococcus uberis as a cause of clinical and sub-clinical mastitis. Staphylococcus aureus continues to be the most common isolate from milk samples identified in Scotland and this is likely to reflect the higher proportion of samples submitted for the investigation of high somatic cell count rather than clinical cases.

Urinary tract diseases

An on-farm investigation was carried out into an outbreak of urinary tract disease in an autumn calving suckler herd in Dumfriesshire. Since April 2005, 5 cows had died (with some presenting as sudden deaths) and 6 had recovered with antibiotic therapy. Clinical examination of the chronically affected cows showed them to be in poorer condition compared to the rest of the group (0.5-1 body condition score thinner), and in two cases there was evidence of passing discoloured urine with floccules present. Culture of urine samples identified only E coli and rectal examination by ultrasound identified bladder wall thickening and hyper-echoic areas within the urine presumed to be the floccules seen clinically. Blood samples collected from the entire group revealed blood urea and creatinine levels within reference ranges for both affected and unaffected cows. It was concluded therefore that the main clinical presentation was of cystitis. Post mortem examination of any further casualties is proposed. The high morbidity and mortality for the group was considered unusual and possible risk factors were considered to be the availability of water during the winter housing period, which is being reviewed.

Sudden onset severe periorbital, preputial and scrotal oedema in a two-year- old Charolais stock bull was associated with marked elevation of blood urea and creatinine consistent with renal failure. The animal showed a marked clinical deterioration despite intensive therapy and the veterinary surgeon confirmed that he was unable to palpate the bladder per rectum. Urolithiasis and/or urethral/bladder rupture was suspected and the animal was euthanased on welfare grounds.

A two-month-old Simmental bull calf from a herd in Inverness-shire died suddenly. Severe bilateral pyelonephritis was detected post-mortem with thickening of the walls of the ureters and severe cystitis. A profuse growth of Arcanobacterium pyogenes was isolated from kidney and bladder.

Diseases of the circulatory system

A three-month-old Stabilizer calf died acutely with evidence of respiratory disease. Post mortem examination at the Dumfries Centre identified severe lung consolidation, pericarditis, endocarditis, myocarditis and fibrosis of the navel. In addition the carcass was jaundiced, the liver enlarged and yellow, the kidneys enlarged and the urine dark red/brown in colour. Salmonella Dublin infection, tick pyaemia and copper poisoning were considered to be the main differential diagnoses. Staphylococcus aureus was isolated from lung and heart tissue and the systemic changes were considered secondary to sudden onset bacteraemia and septicaemia.

Nervous system disorders

Investigations into the possible aetiology of congenital blindness in Holstein Friesian dairy calves were carried out by the Dumfries Centre. The affected herd had a series of cases in 1999-2000 with no reported cases since that time. Three calves had been born in July 2005 with bilateral opacities in the eyes (figure 2; click on PDF link in right hand column) and clinical signs varying from partial to complete blindness. One affected heifer calf was sacrificed for post mortem examination. The calf was considered to be clinically blind with no other clinical signs noted.

Gross pathology was considered to be unremarkable, however histopathological examination of the eyes revealed a severe semi-suppurative uveitis and retinitis with a marked infiltrate of polymorphonuclear neutrophils and macrophages.

Neuropathology also identified a mild mononuclear cell infiltrate in the meninges. It was considered that these findings represented a subacute infectious process, likely to be bacterial, occurring in utero.

Further investigations of this case are in progress, and the case raises the possibility that eyes are a useful tissue for screening for possible infectious pathogens from abortion and stillbirth cases. Further monitoring of cases is planned to examine this possibility in more detail.