VLA Update June 2010

Ketosis and fatty liver syndrome are frequently diagnosed during the summer months, particularly among dairy cows, says the Veterinary Laboratory Agency's UK animal health update.
calendar icon 18 September 2010
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Reproductive diseases

Campylobacter fetus

Penrith diagnosed infection with Campylobacter fetus venerealis intermedius as the cause of five abortions in a herd of 300 dairy cows over a two week period; all at approximately five months gestation. The isolation of this organism suggested that there may also be an impact on herd fertility as natural service was used on this farm.

Salmonella Montevideo

Leahurst isolated Salmonella Montevideo from liver and visceral peritoneum of a foetus from a dairy cow aborted at approximately 7 months gestation. Its dam was a heifer, the second to abort in 3 days in a group of 20 at grass,

Alimentary tract diseases

Coccidiosis

Coccidiosis was frequently diagnosed in June, with 56 incidents reported by 14 regional laboratories. Nationally there was little change in incidence for the period April to June compared the previous year. Thirsk reported that the disease was commonly diagnosed in two to four-month-old suckler calves out at grass. Affected individuals typically presented with blood stained diarrhoea and tenesmus. In most cases the coccidial oocyst counts were between 100 and 2,000 oocysts per gram of faeces.

Luddington investigated cases of sudden death in suckler calves due to Eimeria zuernii infection. In one case two 10-12-week-old South Devon suckler calves in a group of 32 had died without prior signs within a week. Starcross diagnosed coccidiosis in an outdoor group of four-month-old Jersey replacement heifers. One animal had a faecal oocyst count of 3,730,000 opg. And although coccidial speciation was not carried out an oocyst count of this magnitude is characteristic of Eimeria alabamensis, which can cause severe diarrhoea, dehydration and death in grazing cattle.

Langford identified Coccidiosis as the primary enteric diagnosis in older calves. In one notable outbreak all forty housed three-to-four-month old dairy calves were scouring and counts of 13,000 and 3,000 oocysts per gram were detected.

Clostridial enterotoxaemia (type D)

Clostridial enterotoxaemia type D was diagnosed as the cause of sudden death of a 9 month old dairy heifer submitted to Aberystwyth for necropsy examination. Two heifers had died on consecutive days, in a group of 57 heifers aged 5-18 months, 10 days after having been turned out to grass.

BVD and Johne’s Disease in Imported Heifers

The death of an imported Holstein heifer from the Netherlands was found to be due a combination of Johne’s disease, acute BVD; and sepsis following surgery to correct a left displaced abomasum. The animal had recently calved and had very low blood albumin (17.6 g/l; reference range 27-39 g/l) having demonstrated submandibular oedema prior to the surgery; diarrhoea had not been reported. Another imported heifer was positive by BVD antigen ELISA indicating likely persistent viraemia and a potential source of infection to the herd.

Salmonellosis

Shrewsbury diagnosed Salmonella Montevideo infection as the cause of acute enteritis post calving in 4 dairy cows in two Cheshire dairy herds, where several previous cases had occurred over the last year. In another case Salmonella Dublin infection was demonstrated as the cause of acute haemorrhagic enteritis in two cows, one of which died, in a north Staffordshire dairy herd.

Parasitic Gastroenteritis (PGE)

Langford diagnosed Parasitic Gastroenteritis (PGE) as the cause of all eight of a group of six-month old weaned dairy calves, turned out ten weeks previously, developing profuse scour with one dying. Older calves in the same pasture were unaffected. One calf was submitted for post mortem in which large numbers of Ostertagia ostertagi (in the abomasum) and Nematodirus sp. and Cooperia sp. (in the small intestine) were detected.

Respiratory Diseases

Lungworm

Carmarthen diagnosed lungworm infection (Dictyocaulosis) in a group of 50 calves, seven weeks after turnout in mid June. The calves had reportedly been treated with a long acting anthelmintic which should have protected them against lungworm. On examination, most of the group were found to be coughing, and the submission of two faeces samples confirmed the diagnosis, with large numbers of Dictyocaulus viviparus larvae seen following the Baerman test. It was recommended that the details of the treatment were reviewed and if confirmed, reported as an adverse reaction (possible lack of efficacy) to the Veterinary Medicines Directorate.

Musculoskeletal Diseases

White Muscle Disease

Thirsk investigated the sudden deaths of two calves from a group of 20 cows and calves which had been turned out four days earlier. Reportedly calves had galloped about excessively and one calf died suddenly within an hour of turnout. Two more showed respiratory signs which appeared to respond to symptomatic treatment. Necropsy revealed muscle lesions consistent with a myopathy (fig. 1) and histopathological evidence and a demonstration of low serum vitamin E (0.5 µmol/l - reference range >2.3 µmol/l) confirmed a diagnosis of white muscle disease. Sutton Bonnington also diagnosed white muscle disease on post-mortem examination of a two-month-old suckler calf which had died following a week of malaise with recumbency.

Figure 1
Pale linear lesions typical of myopathy in a suckler calf

Metabolic Diseases

Fatty Liver Syndrome

Luddington investigated an increased incidence of periparturient disease, such as retained foetal membranes, endometritis, ketosis and left displaced abomasum in a 330-cow dairy herd. The cows were on very restricted grazing plus dry cow minerals before calving and on a semi total mixed ration (TMR) plus grazed grass after calving. Twelve blood samples were collected from cows 10-20 days post calving. Eight samples revealed an elevated Non Esterified Fatty Acid (NEFA) concentration and six of these were >1000µmol/l, consistent with clinical hepatic lipidosis. A review of the rations was advised. Langford also reported five diagnoses of fatty liver syndrome (based on raised NEFA) this month with clinical signs including malaise, milk drop and non-responsive milk fever.

Preston investigated a problem of anorexia and milk drop in cows approximately 3-6 weeks (inclusive) post calving. Blood samples revealed a BHB level of 4.37 mmol/l (reference range 0-1.2 mmol/l) with evidence of biliary stasis. It was not known whether the ketosis was primary or secondary. Ketosis was also diagnosed (BHB 4.59 mmol/l) in an ataxic cow which had been calved approximately 1 week and now had evidence of a left displaced abomasum (LDA.) Starcross diagnosed nervous ketosis in a dairy cow on detection of markedly elevated BHB levels of 6.61mmol/l (ref range 0-1.2mmol/l)

Hypermagnesaemia (Magnesium poisoning)

Hypermagnesaemia was diagnosed in a group of eight dry dairy cows turned into a field two weeks previously. Three cows died and the remaining five cows later developed diarrhoea and appeared very thirsty despite free access to water. Affected animals were either found dead, recumbent or staggering, and aggressive. In addition to dry cow mineral buckets being fed, magnesium sulphate flakes were added to the water trough resulting in over supplementation of magnesium. This is the second case of deaths in the Langford area in two months in dry cows through over supplementation of magnesium.

Copper poisoning

After copper poisoning was suspected following post mortem examination of a dairy cow, a number of liver biopsies were taken for copper analysis, and a portion of liver was also submitted from a further dead cow. The copper results in the biopsy samples ranged from 9952 – 28,531 µmol/kg DM and the liver from the dead cow registered 36,497 µmol/kg DM (reference range 300 – 8000 µmol/kg DM). This latter figure was sufficient to trigger an investigation to protect the food chain. It transpired that the farm’s nutrition chemist had advised doubling the copper content of the ration fed. The trigger factor initiating the terminal haemolytic crisis was thought to be liver fluke damage and fatty infiltration/degeneration of liver parenchyma caused by a falling plane of nutrition (due to limited grass intake).

Further Reading

September 2010
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