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AHVLA Disease Surveillance Report - September 2012

13 December 2012

UK - Penrith isolated Campylobacter fetus venerealis intermedius from two aborted calves of approximately five months gestation which were received from a dairy herd where four abortions were reported over a month, according to AHVLA's Disease Surveillance Report for September 2012.

Reproductive diseases

The exact role and epidemiology of C. fetus venerealis intermedius is uncertain. It is believed to be spread, like its namesake C. fetus venerealis, by coitus, with infertility and abortions as possible outcomes.

Coxiella burnetii infection (‘Q-fever’) was diagnosed as the cause of an abortion in a herd of 130 Holsteins vaccinated against BVD and IBR. Examination at Shrewsbury confirmed infection by MZN staining and PCR examination, with a purulent and necrotic placentitis identified on histopathology. Although five recent abortions were reported in the herd, Q-fever is usually regarded to be a cause of sporadic abortion and may not have been the cause of the previous losses. Q fever is a zoonotic infection, with a low infectious dose for humans so measures to reduce risk of infection of personnel are advised.

Systemic diseases

A series of deaths was investigated by Aberystwyth in a group of 31 weaned suckler cattle aged about 15 months. The earlier cases were either found dead or showed an acute onset of haemorrhagic diarrhoea, or anal bleeding, epistaxis, and in one, lameness, with death occurring within a few hours. The possibility of anthrax was considered and ruled out. Blackleg was suspected after the initial postmortem examinations undertaken by the practitioner and on a carcase which was submitted to the regional laboratory. Fluorescent antibody testing for Clostridium chauvoei on muscle lesions was positive. However, deaths continued after the animals were moved and vaccinated for clostridial disease, and muscle lesions were not a feature in subsequent postmortem examinations. Examination of two more carcases at Aberystwyth revealed widespread haemorrhages on many viscera and exposure of the affected animals to bracken was confirmed. Anthrax was again excluded and it was concluded that both blackleg and bracken poisoning had contributed to the disease outbreak. Vaccination for clostridial disease was completed; however, a total of 14 animals died over a period of 4 weeks.

Evidence of acute Schmallenberg virus clinical disease was identified by several Regional Laboratories using the PCR for detection of viral RNA on acute phase blood samples, or by ELISA demonstration of seroconversion. Milk drop was the most consistent clinical sign with pyrexia, malaise and diarrhoea reported in some animals. The morbidity in the herds varied, with Langford reporting that between 10 and 20 per cent of cows were affected in one herd of 150 cows whereas more than 30 per cent were affected in a susceptible group of 50 animals in a second herd.

Enteric diseases

Winchester investigated diarrhoea in a dairy herd. Faecal samples were received from recently calved cows Two of the samples had coccidial oocyst counts of 15,950 and 24,250 oocysts per gram, and speciation of the oocysts from the animal with the highest count revealed that 67 per cent of the oocysts were Eimeria alabamensis and 28 per cent were Eimeria zuerni. Both coccidial species are usually associated with disease in calves; however, occasionally outbreaks have been attributed to E alabamensis in older animals particularly when at grass.

Salmonella Enteritidis PT2 was isolated at Sutton Bonington from a faeces sample which was submitted from a dairy cow. It was reported that two animals had developed diarrhoea and pyrexia soon after calving. They were isolated and treated with antibiotic and both recovered. Advice was given on appropriate measures to mitigate the risk of zoonotic infection. Samples collected at an advisory farm visit confirmed environmental contamination by S Enteritidis PT2 in the collecting yard and shed where the cows had been isolated. No further disease was reported in the cattle.

Skin disease

Investigation of a 250 cow dairy herd with foot lesions in six dry cows was undertaken at Thirsk. The affected animals exhibited foot swelling, with or without lameness, with rapid development of skin crusts, predominantly affecting the hind feet of recently dried off cows at grass. The lesions became alopecic and then gradually resolved over four weeks. The problem had also affected six different animals in a group of dry cows at a similar time last year, although in different fields. Skin scrapings and biopsies were collected but no infectious agents or ectoparasites were identified. Histopathology revealed a moderate perivascular eosinophilic dermatitis, which by its localised nature suggested that insect bites may have lead to a hypersensitivity response.

Further Reading

Find out more information on the diseases mentioned here by clicking here.

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