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February 2009 RVL Monthly Report

Cattle

Fibrinous pleurisy, caused by Arcanobacterium pyogenes, was observed in a bovine foetus submitted to Dublin. A. pyogenes may cause sporadic abortion at any stage of pregnancy. The bacterium is present in the nasopharynx of many clinically normal cows, and in abscesses. It is not normally present, even as a contaminant, in foetuses or foetal membranes, and isolation is almost always significant. It gains entry to the bloodstream and causes an endometritis and placentitis. The foetus is usually autolysed, with fibrinous pericarditis, pleuritis, or peritonitis possible. It is important to encourage farmers to submit placentae from abortion outbreaks along with the foetus as lesions might only be present in the placenta.

A calf was delivered to Athlone, alive, recumbent, head held in raised position and bilaterally blind. Ante mortem assessment indicated that the blindness was due to turbidity in the aqueous humour of both eyes. On gross post mortem examination, there was oedema and cloudinesss of the meninges of the cerebral hemispheres and some fibrin around the cerebellum and peduncles. Escherichia coli was isolated from the aqueous humour and mid-brain. A zinc sulphate turbidity (ZST) test result of 2 units (normal: >20 units) indicated poor transfer of immunity via colostrum. Multiple sections of brain (cerebrum, midbrain and brainstem) exhibited lesions of severe suppurative meningitis on histopathology. A diagnosis of colisepticaemia was made, with septic meningitis and septic opthalmitis. All centres reported frequent cases of colisepticaemia in calves less than one week of age. In many cases low ZST test results indicated hypogammaglobulinaemia associated with poor absorption of colostrum antibodies.

Sligo reported an interesting case of a human factor having a major impact on neonatal calf survival in a suckler herd.  Calf mortality had been low on the farm and there were no particular neonatal disease problems in previous years. Over a weekend in February, three young calves developed a severe scour, and died despite intensive intravenous fluid therapy, antibiotics and nursing, and with further cases over the next few days five of the first 20 calves born in 2009 died of a similar syndrome.  Post mortem examination of one of these calves revealed a heavy cryptosporidium spp. infection and a positive rotavirus result, as well as a ZST test result of three units.  Further samples from other calves in the batch revealed slightly higher but sub-optimal ZST values. It transpired that the suckler farmer who had a 100-cow herd and limited farm labour, had decided to give each 2009-born calf a feed of commercially produced "artificial colostrum" by stomach tube shortly after birth. This was done to save time, but it seems likely that this policy had the effect of depressing the calf's appetite, and may also have suppressed it's suck reflex. The farmer observed that calves often slept for over six hours after being fed the product, and frequently had to be wakened for the next feed. The practice has been abandoned, and artificial colostrum has been reserved for emergencies only. Other management deficits on the farm are also being addressed, including the failure to isolate sick calves.

All centers reported a sharp increase in the number of calf faeces samples submitted. Four hundred and seventy two samples were analysed during the month. Table 1 summarises the findings.

Analysis of calf faecal samples Feb 2009 (xls 19Kb) 

Table 1: Calf faecal sample analysis.

Sligo is investigating a case of malignant catarrhal fever (MCF) in an 18-month old bullock, housed in a slatted shed where sheep shared the same air space. The clinical signs progressed from lacrimation and depression to convulsions, prostration and death within a 72-hour period. The rectal temperature peaked at 107oF, and there was marked generalised lymphadenopathy. In addition, corneal opacity developed over the course of the illness. The diagnosis was confirmed as Ovine Herpesvirus 1 at the Central Veterinary Research Laboratory at Backweston.

Limerick examined a three year-old cow that presented clinically with depression and diffuse lymphadenopathy. A large tumour-type lesion was present in the sublumbar region of the abdominal cavity, and there were also involvement of the lymph glands and the pericardium. Histopathology confirmed a diagnosis of lymphosarcoma. An ante mortem blood sample was negative for enzootic bovine leucosis (EBL).

One four-year old cow, which was submitted to Dublin, had become recumbent one day after calving but had apparently recovered after treatment with intravenous calcium. However, it became recumbent again within a short time, and died within three days. A milk sample taken from one of the quarters of the mammary gland was brown and watery and contained clots. Escherichia coli was isolated from this sample. On gross post mortem, severe fibrinous pericarditis was the main finding, with congestion of meningeal blood vessels also noted. The main finding on histopathological examination of tissue was suppurative mastitis and multifocal necrosis in the liver, with an associated inflammatory infiltration comprised of macrophages and neutrophils. The histopathological and gross findings were consistent with septicaemic change. It was considered likely that the coliform mastitis had given rise to septicaemia.

Limerick examined a nine-year old cow that had a history of abnormal gait, anorexia and ill thrift. Traumatic reticulitis with abscessation of the liver and lung was diagnosed. Two three-inch long pieces of wire were recovered from the reticulum. Kilkenny reported a series of cases of traumatic reticulitis in cows from different farms. One cow had a wire in the reticular wall and a local abscess, with slight pericarditis. Another cow had intra-reticular haemorrhage as a result of a foreign body, while a third had a classical bread-and-butter pericarditis (Figure 1). A six-year old cow, which had been sick for one week with depression and dyspnoea, was submitted to Athlone. Traumatic reticulitis was suspected. However, there was no evidence of this on post mortem examination. Instead the liver was found to be moderately enlarged, and greasy and hard on palpation. There was no evidence of fluke infection. Intestinal contents were fluid and dark in colour. On histopathology, severe hepatic lipidosis was evident leading to a diagnosis of fatty liver disease.

Bread and butter pericarditis

Figure 1: "Bread and butter" pericarditis in a cow with foreign body reticulitis (photo: Donal Toolan).

Bovine Viral Diarrhoea (BVD) antigen was identified in the pleural fluid of a foetus submitted to Athlone. Advice was given regarding the testing of the dam to determine if she was persistently infected (PI).

A two-year pregnant heifer was submitted to Athlone with a history of sudden death. Epicardial haemorrhages were seen on gross examination, and there was abundant grain and fluid content in the rumen and abomasums, with segmental reddening of the mucosa of the duodenum and proximal jejunum. No significant lesions were noted in any other organs. The rumen pH was recorded at 3.5, supporting a diagnosis of acute rumenal acidosis due to grain overload.

Sheep

Two foetuses from separate ewes on one farm were submitted to Athlone. There had been six abortions up to then, in a flock of 360 ewes. The owner estimated that the ewes were one month from the due date. The foetal membranes exhibited pallor of the cotyledons and focal areas of hyperaemia in the intercotyledonary tissue. Sections of placenta from both submissions exhibited histological lesions of suppurative placentitis and vasculitis, with loss of trophoblast epithelium. A diagnosis of Chlamydophila abortus associated abortion was made. Athlone examined aborted twin foetuses from a farm with a history of a 1-2% annual abortion rate in the flock. There were no specific gross lesions seen but Listeria monocytogenes was isolated from the stomach contents of one of the lambs.

Suppurative metritis was diagnosed by Dublin as the cause of death of a four-year old ewe. Poor hygiene practices during an assisted lambing may have accounted for the metritis. The ewe also had a high faecal strongyle egg count. Myelopathy, characterised by myelin vacuolation in the cervical spinal cord, was also seen in this ewe, the cause and significance of which is unknown. This spinal cord lesion was similar to that seen in swayback; however, the liver copper concentration was within normal limits.

Sligo is investigating an outbreak of Sheep Pulmonary Adenomatosis (Jaagsiekte) in a housed Scottish Blackface sheep flock in county Donegal. Four sheep had died with a chronic progressive respiratory syndrome before the fifth sheep to develop clinical signs was presented to Sligo. There was a mild nasal discharge, and the trachea was filled with dense stable foam. There were multifocal discrete to coalescing firm masses in the lungs, ranging in size from 2 to 60 mm in diameter (Figure 2), and generalised pulmonary oedema. Histopathological analysis confirmed the diagnosis.

Pulmonary lesions associated with sheep pulmonary adenomatosis

Figure 2: Pulmonary lesions in an adult ewewith sheep pulmonary adenomatosis (photo: Mícheál Casey).

Two recumbent ewes that failed to respond to treatment with calcium and magnesium were submitted to Kilkenny, where listeriosis was diagnosed on histopathological examination of brain tissue. A three-week old lamb that lost the use of its hind limbs was euthanased and submitted to Kilkenny. An abscess was discovered in the vertebral canal of the anterior thoracic spinal column.

Pigs

Kilkenny isolated Escherichia coli (type O141) from pigs aged six weeks, which had a history of enteritis.

Two weaner pigs examined by Athlone had lesions of fibrinous pleuritis, with haemorrhage and consolidation of the underlying lung tissue. Actinobacillus pleuropneumoniae was isolated from the lungs of both pigs.

Other Species

Limerick examined a four-year old in-foal mare that died after a short illness. The mare showed pronounced anorexia and weight loss over a period of five days. A neoplastic growth weighing about thirteen kilograms and involving the spleen, was found on post-mortem examination. Secondary growths were also seen in different locations. A diagnosis of lymphoma was made.

A faecal sample from a circus camel was submitted to Limerick for examination. The camel had a history of diarrhoea and weight loss over a two-month period. The parasitic egg count was high, with strongyle, strongyloides and trichuris egg types seen. There was also a high coccidial oocyst count, but no significant bacterial pathogens were isolated on routine aerobic culture.

Sligo diagnosed equine hyperlipidaemia in a four-year old, pregnant, Shetland pony that presented with sudden onset diarrhoea, dullness and anorexia. The disease was refractory to treatment. There was a concommitent significant intestinal parasite infection. It has been suggested that pony hyperlipidemia occurs in animals with a degree of insulin resistance. Elevated cortisol and progesterone levels are thought to exacerbate the problem and lead to an abnormal accumulation of triglycerides within hepatocytes. Shetlands are the most susceptible breed and it is most commonly encountered in pregnant, lactating or over-weight females with hoof problems or parasitism.

Mixed cell lymphoma was diagnosed by Kilkenny in an eighteen-month old alpaca with a history of poor thrive. There was enlargement of the lymph nodes of the head and neck and multifocal pale lesions in the liver.

Sligo diagnosed adult-onset mega-oesophagus in a five-year old emaciated German Shepherd. There was a seven-centimetre spherical oesophageal diverticulum containing bone fragments, sand and decomposing fragments of ingesta in the cranial thorax.