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AHVLA Scanning Surveillance Report – June 2011

29 July 2011
AHVLA

UK - Unusual dermatitis in dairy cows and outbreaks of lead poisoning in cattle were some of the reported illness's in cattle over the last month, according to the Monthly Scanning Surveillance Report from the Animal Health and Veterinary Laboratories Agency (AHVLA).

Reproductive diseases

Dystokia

A dairy calf, born unassisted but found dead the next day, was diagnosed by Penrith with neonatal respiratory distress syndrome thought to be associated with perinatal hypoxia.

Extensive bronchiolar epithelial necrosis with hyaline membrane formation was seen on pathological examination. In another case dystokia was diagnosed as the cause of death of a 64kg stillborn calf with fractured lumbar vertebrae and in a 49kg calf with evidence of lingual oedema and bleeding into the meninges and neuroparenchyma.

Bacillus licheniformis abortion

Carmarthen identified Bacillus licheniformis as the cause of abortion in two out of a group of 60 permanently housed dairy cows. The husbandry system was described as ‘high input’ with the cows fed maize and grass silage, beet pulp and soya meal.

It is possible that mouldy, poorly conserved feed components were the source of infection that caused these, and one other abortion that occurred over a three day period.

Listeria monocytogenes

Starcross diagnosed Listeria monocytogenes as the cause of three abortions in a group of suckler cows over a period of one week. Abortions had appeared to coincide with the recent introduction of a new batch of silage which was of questionable quality.

Alimentary tract diseases

Fasciolosis

Luddington diagnosed fasciolosis as the cause of weight loss and/or diarrhoea in adult cows from two suckler herds and Thirsk diagnosed the condition in two dairy cows demonstrating similar clinical signs. Shrewsbury investigated incidents in Staffordshire and Gwynedd. They also identified rumen fluke (Paramphistomum species) ova in the pooled faeces of two dairy cows with diarrhoea and weight loss.

Coccidiosis

Seven laboratories diagnosed coccidiosis in calves. A typical case was described by Winchester who received a faecal sample from a ten-week-old Hereford-cross calf with a history of sudden onset diarrhoea.

A coccidial oocyst count revealed 36,800 oocysts pg, 100 per cent of which were identified as the pathogenic species Eimeria zuernii. Sutton Bonington also diagnosed the condition as the cause of an outbreak of the disease in a group of 20 animals at grass, in which 50 per cent had developed tenesmus and diarrhoea.

Shrewsbury diagnosed six cases including a two year old diarrhoeic dairy heifer which had an oocyst count of 256,000 per gram although most cases they diagnosed were in the typical age range of five weeks to three months.

Respiratory Diseases

Lungworm (Husk)

Sutton Bonington diagnosed patent lungworm (Dictyocaulus viviparous) infestation in a one-year-old suckler animal at grass in a group of 200. The animal had been presented to the attending veterinarian with rapid onset dyspnoea but was not pyrexic on examination.

Shrewsbury also identified lungworm infestation as a predisposing factor in the death of a 123 kg Simmental heifer which died from pneumonia caused by Pasteurella multocida.

Shrewsbury also reported two further cases. The first was an investigation of an outbreak of non productive coughing in a dairy herd which revealed positive serological results indicating husk to be a possible cause.

The second involved disease in two groups of mixed age dairy animals in a north Shropshire herd, with around 50 per cent of the animals reported to have developed acute coughing.

Bacterial pneumonia

Sutton Bonington necropsied a four-month-old weaned dairy calf which had demonstrated acute, severe respiratory signs. It was the fifth recorded death in a calf-rearing unit, where three deaths had been recorded in a group of 20 calves within a week.

Clinical signs included frothing at the mouth, hyperpnoea and severe illness. The calves had been at pasture for some time before the outbreak started and all affected calves had been performing well.

A severe acute bacterial suppurative bronchopneumonia was diagnosed with Pasteurella multocida and Histophilus somni isolated on culture and Mycoplasma dispar identified by DGGE.

Infectious Bovine Rhinotracheitis (IBR)

Thirsk diagnosed IBR as the cause of severe respiratory disease in two calves in a group reared on an automatic feeder. Clinical signs included slavering and malaise and gross post mortem examination revealed widespread ulceration and diphtheresis affecting the laryngeal ventricles, pharynx and nasal mucosa together with evidence of acute pneumonia.

The diagnosis was confirmed by FAT testing on tracheal mucosa. Subsequent bulk milk antibody testing revealed evidence indicating a recent introduction of the virus into the herd. Vaccination was recommended.

Carmarthen also diagnosed acute IBR infection in a recently imported 20 month old heifer. It was the only animal affected and had been found dead. At necropsy examination, there were sub mucosal ecchymotic haemorrhages along the length of the trachea, and patchy consolidation affecting approximately 70 per cent of all lung lobes. The diagnosis was confirmed by FAT.

Other Diseases

Unusual dermatitis

Shrewsbury investigated an unusual outbreak of skin disease after swellings on the neck area of dairy cows had been brought to the attention of the attending vet during TT tests.

Approximately 40 out of 480 milking cows in one management group were affected over a two week period with variablesized swellings on the skin of the neck, some of which discharged purulent material leaving raised, scaly, and firm, resolving lesions.

All of the milking cows had heat-time detector neck collars which had been used for some time.

Lesions were only associated with the region of the neck where the collar could rub.

Staphylococcus aureus was isolated from discharging lesions and punch biopsies of affected areas showed severe, multifocal, necrotising, eosinophilic and purulent dermatitis, consistent with a diagnosis of dermatitis caused by ectoparasites, most likely insect bites.

Some cows had shown irritation and rubbing of the area but otherwise appeared unaffected and there was no loss in production.

The distribution of the lesions suggested that the collars were involved in the mechanical spread of infection. At the time of an investigative visit the lesions were resolving and no new cases had occurred. The likely sequence of events was considered to be insect bites causing irritation which was exacerbated by the rubbing of the collar and Staphylococcal infection.

Lead poisoning

Access to sump oil was found to be the cause of an outbreak of lead poisoning investigated by Luddington.

Two 14-month-old fattening cattle died in a group of 15 at grass; one was found dead and one died following an episode of trembling, convulsing and disorientation of a few hours duration. A third animal was reported to be affected but did not die.

Winchester also investigated an outbreak affecting a group of 40 suckler cows grazing heath land. The affected animals had been found dead and necropsy of one revealed metallic fragments in the reticulum which were thought to be the source of the lead.

Preston diagnosed lead toxicity following the submission of two blood samples from six month old suckler calves which had demonstrated blindness, frothing at the mouth and death. Lead batteries were found in the field.

Newcastle and Carmarthen also diagnosed cases associated with discarded car batteries. In all of these cases, a risk assessment was carried out and appropriate measures were put in place to protect the human food chain.

A guidance leaflet containing advice on how to avoid lead contamination of farm livestock is available at http://vla.defra.gov.uk/science/docs/sci_lead_prevent.pdf

Gangrenous mastitis

A mastitis sample was submitted to Thirsk from a herd of approximately 300 cows, in which six cases in five months of per acute gangrenous mastitis had occurred.

The herd was vaccinated with a combined E. coli and Staphylococcus aureus vaccine.

This particular animal had been vaccinated in March 2011 and dried off on the same date using a cephalosporin-based dry cow preparation together with an internal teat sealant.

Anaerobic culture of the milk produced a profuse growth of Clostridium perfringens which was identified as type A on toxin testing by ELISA. This is a recognised cause of gangrenous mastitis that has previously been reported in the literature (Can Vet J 1990 31:523-524).

Tetanus

A diagnosis of tetanus was made based on clinical signs, and exclusion of other potential causes of death, in a bulling dairy heifer submitted to Carmarthen. It was one of four to die in a short period from a management group of 60. All animals were either found dead, or with a stiff neck and hind legs, raised tail head and protruding third eye lids.

Blackleg

Truro diagnosed blackleg in a 10 month-old Charolais cross calf, one of six animals to have died either with no premonitory clinical signs or shortly after acute onset of clinical signs.

The animal had been observed to have a swollen neck that failed to respond to penicillin 24 hours prior to death. Necropsy revealed subcutaneous haemorrhages and oedema extending from the brisket to the mandible and a distinct 10 cm diameter swelling present in the muscle at the angle of the jaw which, on sectioning, was found to contain several dry haemorrhagic lesions.

Extensive dry haemorrhages and necrosis also were present in muscles along the entire ventral and ventrolateral neck from the jaw to the brisket and the oesophagus, larynx and trachea were adhered to surrounding necrotic tissue.

Clostridium chauvoei was detected by FAT in neck muscle, consistent with a diagnosis of blackleg.

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