AHVLA Scanning Surveillance Report – June 2011
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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