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Late Cut Silage Increases Ergotism Cases - VLA

12 March 2012
AHVLA

UK - In the latest AHVLA Scanning Surveillance Report, late cut silage was associated with signs of ergotism, with 8/26 affected cattle euthanased, streptococcus suis type 2 remains a prominent cause of pig mortality and hypoglycaemia - spiking mortality syndrome was suspected in a three week old broiler flock.

Reproductive diseases

Penrith Regional Laboratory isolated E. coli in pure growth from the stomach contents of a freshly aborted fetus. There was pathological evidence of a bronchiolitis probably as a result of inhaled infected amniotic fluid.

Langford investigated an abortion outbreak in which approximately 20 heifers in a herd of 600 cattle aborted in a three week period. The affected animals were all imported and grazed turnips and rape. Cases of haemolytic anaemia had occurred in the group three to four weeks previously and Babesia had been found in blood smears prompting treatment of the group. Extensive testing for brucellosis consistently proved negative. Several other potential causes for the abortions were identified from submitted maternal and fetal samples, including Salmonella Dublin from several cases. Babesiosis may also have contributed to the abortions. Other differentials such as BVD, leptospirosis, neosporosis and IBR infection were ruled out.

Truro investigated the cause of abortion at five months gestation in a dairy cow. Listeria monocytogenes, a potential cause of abortion, was cultured in mixed growth from the fetal stomach contents and antibody to Neospora caninum was detected in body fluids. Neosporosis was considered likely following subsequent demonstration of non-suppurative myocarditis by histopathology. This abortion may have been due to both infections; abortion due to two or more infectious causes is rare in cattle.

Enteric diseases

As usual and at all Regional Laboratories, rotavirus infection and cryptosporidiosis were the most commonly diagnosed causes of diarrhoea in young calves.

Langford diagnosed coccidiosis on several occasions during December, mostly in post-weaned calves with signs varying including acute diarrhoea to more protracted wasting and malaise. Coccidiosis was diagnosed in a three year old, recently calved dairy heifer that had been housed about a month before the onset of haemorrhagic diarrhoea with thickening of the rectal wall. The coccidial oocyst count was 1,266,000 oocysts / gram. Speciation was not undertaken, but E. alabamensis is often associated with outbreaks in older animals.

Shrewsbury diagnosed Jejunal Haemorrhage Syndrome (JHS) in an adult dairy cow that was the sixth animal in the herd to die rapidly following the development of acute, non-specific enteric signs and milk drop. At post mortem the jejunum was dark-red and hugely distended with strands of fibrin over the surface. Internally the contents were a mixture of bloody fluid and large sausage-like blood clots. These findings were consistent with a diagnosis of JHS. The aetiology is unknown although Clostridium perfringens Type A has been implicated in clinical cases investigated in Canada and the United States (Abutarbush and Radostits 2005).

Respiratory diseases

Carmarthen diagnosed Histophilus somni and Mycoplasma bovis infection as the cause of peracute pneumonia and death of a two week old suckled calf. This was the only animal to die of 12 cows and calves in a building and had been found dead with no other clinical signs. At post mortem, there was consolidation of about 65% of the lung tissue with an antero-ventral distribution. A pure growth of Histophilus somni was isolated from lung and Mycoplasma bovis was also detected from lung by PCR/DGGE.

Other diseases

Carmarthen diagnosed endocarditis in a four and a half year old Holstein cow that was found dead a few weeks after treatment for a subcutaneous abscess near to her right hip. At post mortem, there was thickening of the right atrioventricular valves, many small abscesses throughout the lungs and a large subcutaneous abscess close to the right hip, the probable source of infection. Trueperella pyogenes (previously A. pyogenes) was isolated from the abscess, the valve lesion and the lung lesions.

Skin diseases

Thirsk diagnosed chorioptic mange, in association with dermatophytosis, in calves between one and two months of age, with crusting and alopecia, which persisted after some were vaccinated against ringworm. Samples from vaccinated and unvaccinated calves were examined: Chorioptes mites were observed in samples from vaccinated animals and Trichophyton verrucosum was cultured from unvaccinated calves and those which had not completed their primary course of vaccination. There was no evidence that the vaccine was ineffective and the presence of Chorioptes mites was probably exacerbating the clinical condition.

Other Diseases

Newcastle detected ergot in a sample of silage (see photo) from a farm where approximately 26 of 140 cows were reportedly affected with lameness associated with pain and swelling of the lower hind limbs. Eight of the 26 affected cows were killed on humane grounds due to the severity of the lameness and the remainder recovered. Some remained slightly lame. There had been a previous episode of ergot poisoning on this farm and the current contaminated silage had been cut late from a field adjacent to that responsible for the last outbreak. The contaminated silage was withdrawn. Ergotism can be prevented by ensuring that grass is cut before seed heads develop.

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