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January 2009 RVL Monthly Report

Cattle

Athlone reported a case of foetal anasarca (hydrops foetalis) in a male foetus (figure 1) aborted in the eighth month of gestation. There was subcutaneous oedema of the carcass, with numerous pockets full with fluid. Internally the gall bladder was hugely distended but the other organs, including the brain, appeared normal. There was no other case in the herd. Hydrops foetalis is defined as a state of excessive fluid accumulation in the extravascular compartment of the foetus, leading to widespread soft tissue oedema and/or accumulation of fluid in the foetal body cavities.  A search in the literature relates the condition in some cases to circulatory malfunction and in others, to a recessive gene.

Bovine foetal anasarca

Figure 1: Bovine foetal anasarca (photo: John Fagan).

Campylobacter foetus subspecies foetus was isolated from a foetus submitted to Kilkenny. Listeria monocytogenes was isolated by Dublin from one of two foetuses submitted from the same herd, one of which had myocardial hypertrophy. Bovine viral diarrhoea (BVD) virus was identified in a newborn calf presented to Kilkenny with microphthalmos, torticollis and nystagmus. In another case, Kilkenny examined a newborn calf with cleft palate (figure 2), the aetiology of which was not found.

Cleft palate in a newborn calf

Figure 2: Cleft palate in a newborn calf (photo: Donal Toolan).

A five-day old, bucket-fed, Friesian calf with a history of scour over a period of 24 hours was presented to Dublin for post mortem examination. Three other calves from this group had died in a similar manner. The main gross findings were dehydration and enteritis, with the large intestine containing foul-smelling faeces and fibrin clots. Salmonella dublin was isolated from all organs cultured. A twelve-day old calf was submitted to Athlone, alive and convulsing. The animal was euthanased. Grossly, a purulent arthritis of the tarsus was evident. There was also a bloody exudate in the meninges and around the brain. Micrococcus species was isolated in pure growth from the joint. Micrococcus spp. are skin commensals and opportunistic pathogens. Histology supported a diagnosis of septic suppurative meninoencephalitis. A zinc sulphate turbidity (ZST) test result of 2 units (normal: >20 units) in this animal indicated inadequate absorbtion of colostrums antibodies.

Athlone examined a one-month old calf that had been treated for pneumonia, appeared to respond, but relapsed, pined away and eventually died. Gross post mortem examination revealed lesions of pulmonary oedema and antero-ventrally distributed pneumonia. There were no other specific lesions. Bovine herpes virus type 1 (BHV1) was detected in lung tissue. Histopathological examination showed foci of coagulative necrosis in the liver, which is consistent with congenital BHV1 infection. This cow had also lost one of her two previous calves.

Cerebrocortical necrosis (CCN) was diagnosed by Dublin in a six-week old calf from a suckler unit where a number of calves had developed sudden-onset nervous signs, including head pressing and blindness. Two of the affected calves responded to vitamin B1 injections. The dams were being fed maize silage to which the calves also had access.

Virology division identified Bovine Coronavirus (BoCo) and Bovine Respiratory Syncytial virus (BRSV) in lung tissue from a three-week old calf that was submitted to Kilkenny with a history of cough and pneumonia. BoCo has been isolated from cases of shipping fever in North America but it is not clear whether it is a primary cause of pneumonia, or a secondary invader. Kilkenny isolated Histophilus somnus from the lungs of a six-month old weanling with a history of respiratory distress prior to death. Respiratory syncytial virus (RSV) was also detected in this case.

A nine-month old continental-type weanling was presented alive to Athlone. It had a history of lameness/stiffness over the previous two months and had been moved from a slatted house to a bedded pen, but had not improved. The lameness worsened over the course of a fortnight. On post mortem examination gross lesions were confined to the stifle joints. There was marked synovial hyperplasia (pannus) in both stifle joints. This was associated with multiple defects in the articular cartilage of the lateral condyle of the left tibia, and the medial condyle of the right tibia, with subchondral bone loss. The findings were consistent with a diagnosis of osteochrondrosis with secondary changes of early degenerative joint disease (figure 3). Osteochondrosis is reported in cattle but is unusual. As in other species it is associated with rapid growth of large breed animals. In some breeds there may be a genetic predisposition.

Osteochondrosis in a weanling   

Figure 3: Osteochondrosis in a nine-month old Continental weanling (photo: Jim O'Donovan).

Kilkenny examined a ten-month old weanling, the fourth to die in the group. It was reported that animals became very thin before death. Severe chronic fluke infection was found on gross examination, with over 200 parasites found in the liver and gall bladder. Salmonella Dublin was isolated from the intestine. Many of the in-contact animals were blood sampled. Consistent findings included hypoalbuminaemia and raised enzymes- aspartate aminotransferase (AST), gamma glutamyltransferase (GGT) and glutamate dehydrogenase (GLDH).

A five-year old cow submitted to Kilkenny had been treated for pneumonia after calving three weeks earlier. There was a poor response to the treatment and pleurisy was diagnosed one week later. Euthanasia was eventually decided upon after the animal developed left-sided displacement of the abomasum. On post mortem examination the lungs were overinflated and there were lesions of interlobular oedema and emphysema. Many hoose larvae were seen in the airways, leading to a diagnosis of verminous pneumonia. Pyelonephritis was diagnosed by Dublin in a continental suckler cow that was passing blood-stained urine before death. Two other cows in the herd, which were also housed in straw-bedded housing, were reported to have had similar clinical signs.

Sheep

Toxoplasma gondii antibody titres of up to 1/1024 were detected by Dublin in three blood samples from ewes in a flock with a history of abortion over two lambing seasons. In twin lamb foetuses submitted to Athlone, Salmonella dublin was isolated from the stomach contents of one and from the foetal membranes of the other.

A three-week old lamb with a history of sudden death was presented to Athlone. Intestinal contents were fluid and haemorrhagic in appearance, and the small and large intestine were severely congested. The abomasal mucosa was hyperaemic and oedematous. Clostridium septicum was isolated and a diagnosis of clostridial enterotoxaemia was made.

Polioencephlalomalacia was diagnosed in a twelve month-old lamb that was submitted to Limerick. The group had been housed and introduced to concentrate feeding two weeks previously.

An adult ewe that exhibited unilateral neurological signs was submitted to Athlone, where Listeria monocytogenes was isolated from the brainstem. Histology showed microabscessation and perivascular cuffing in the cerebrum, lesions consistent with a diagnosis of listerial meningoencephalitis.

All laboratories reported on cases of acute and chronic fascioliasis in adult ewes.

Pigs

Two sows were submitted to Kilkenny from a group of 39 sows that had all been found dead in two adjoining pens. Electrocution was the suspected cause of these deaths as a live wire was found close to the pens. Skin lesions consistent with scorch marks were detected on the lower jaw of one of the sows.

Poultry

Coccidiosis was diagnosed by Dublin in four-week old broilers with stunted growth.

Ten laying hens from a flock where eggs were exhibiting poor shell formation were submitted to Dublin for post mortem examination. Infectious bronchitis was suspected but no evidence of the virus was found. The main finding was the presence of poorly digested food material in the large intestine and rectum. It was suspected that the poor shell formation may have been secondary to malnutrition associated with poor digestion of the food supplied. Investigations are ongoing.

Other Species

An equine foetus and placenta was submitted to Athlone for examination. The placenta exhibited fibrous, nodular "pearls" following the path of  the blood vessels. Streptococcus equinus was isolated from the stomach contents of the foetus. Tests for Equine Herpesvirus 1 and 4 were negative. The isolation of Streptococcus equinus from stomach contents indicated the presence of an intrauterine infection in this mare.

Limerick investigated an outbreak of Salmonella typhimurium infection in a group of fifty horses. The presenting signs included ventral oedema and profuse diarrhoea, with eventual recumbency and death. Hypoalbuminemia, due to protein-losing enteropathy, was seen in blood samples submitted from clinical cases. The morbidity rate was about forty percent with a mortality rate of fifty percent of those affected.  The horses were housed on slats and were being fed silage of dubious quality.  Antibacterial therapy in the early stages had some success.

Kikenny diagnosed lead poisoning in four whooper swans (Cygnus Cygnus). Many had impaction of the oesophagus and proventriculus. Liver lead was measured as 107, 74, 105 and 171micromol/kg wet matter. Values over 30micromol/kg are consistent with lead poisoning.

A nine-month old chinchilla (Chinchilla lanigera) was presented to Athlone. It had a history of dribbling and had been treated for teeth problems. The owner had reported that the animal had poor energy for the previous 3 weeks. On gross post mortem there was no evidence of trauma. The lungs, heart and liver were normal in appearance. The stomach was empty and intestinal contents had a pasty consistency. Routine culture of the liver isolated Salmonella typhimurium. This is a zoonosis and of particular concern as this was a child's pet.