Current Findings in the Regional Veterinary Laboratories November 2007
Cattle The laboratories received a total of 255 bovine foetal submissions during the month. Salmonella dublin was isolated from 47 (18%) of the submissions, making it the most common bacterial pathogen isolated. Figure 1 gives a break down of the results of culture for bacteria (only) from foeti for the month.
Septicaemia associated with Salmonella dublin was diagnosed by Dublin in calves dying within the first week of life. Histopathological findings included vasculitis with thrombosis, typhoid nodules in the liver, acute diffuse interstitial pneumonia, fibrinous arthritis, suppurative meningitis and suppurative interstitial nephritis. Salmonella Dublin was cultured from lung, liver, blood, brain, kidney, spleen and faeces. The zinc sulphate turbidity (ZST) results in the two calves submitted indicated that colostral immunoglobulin absorption was less than adequate.
A weanling bought three days previously at a mart, and with a short history of severe respiratory distress, was presented to Athlone. Post mortem examination revealed lesions of acute pneumonia with tracheal congestion and a fibrinous exudate in the airways. Lesions were most severe in the ventral aspect of the cranial lobes but oedema and congestion were seen throughout the lungs. Bovine respiratory syncytial virus (BRSV) was detected and Mannheimia haemolytica was isolated on routine culture. Another weanling, which had been treated for pneumonia a number of times prior to death was presented to Athlone. Gross examination revealed severely abscessed and emphysematous lungs with almost no area of unaffected lung. The right lung was partially gangrenous and a localised fibrinous pericarditis was present. Culture of the lung tissue yielded Pasteurella multocida and PCR was positive for BRSV.
Malignant oedema was diagnosed in a heifer submitted to Athlone. A traumatic injury several weeks previously may have provided the suitable conditions for entry and growth of the anaerobic pathogen. Gross post mortem revealed gelatinous oedema, haemorrhage and gassy change in the subcutaneous tissue and musculature from the shoulder region to the thoraco-lumbar area. A fluorescent antibody test (FAT) was positive for Clostridium novyi. Athlone also diagnosed blackleg in four weanlings from four different herds. Clostridium chauvoei was detected (using an FAT) in the affected muscle of two of the four animals.
Limerick suspected that hypomagnasemic tetany resulted in the sudden death of a thirty-month old suckler heifer. It was the third death in a group of twelve that were bought in September. Biochemical analysis of an aspirate of cerebrospinal fluid gave a Magnesium reading of 0.67 mmol/l. This is at the bottom of the ‘normal’ reference range, but because of the length of time since death, the result was not considered to be conclusive. Blood samples from five in-contact animals gave magnesium readings as low as 0.4 mmol/l (normal range: 0.65-1.2 mmol/l). Athlone also suspected that hypomagnesaemia was responsible for the death of a twelve-year old cow. A sample of the aqueous humor of the eye was analysed and found to be low in Magnesium in that case. Carcass parts from a bullock were submitted to Athlone following a field post mortem by the referring vet. A history of incoordination and ataxia was reported by the owner following release of the animals onto a field of maize stubble. This animal was the third loss. Histopathology revealed necrotising hepatitis, mild interstitial pneumonia and globular thrombi (“shock bodies”) in the blood vessels of the brain. These changes, when considered with the history, suggested a tentative diagnosis of ruminal acidosis.
A heifer with a history of abortion, pyrexia, congested mucous membranes, photophobia, ocular discharge and dermatitis was euthanased and submitted to Cork for post mortem examination. Malignant Catarrhal Fever (MCF) was one of the differential diagnoses considered but this was ruled out following a negative test result. A test for BVD viral antigen was positive.
Sheep Athlone diagnosed acute fascioliasis that resulted in the death of two ewes. Numerous mature liver fluke within hypertrophied bile ducts and associated with localised peritonitis surrounding the liver were observed by Dublin in a ewe which was one of 28 ewes that died within a 100-ewe flock. Twenty-seven of the 28 ewes were found dead without any prior clinical signs observed and the ewe presented was in very good body condition with normal faeces. The flockowner considered his land as relatively dry and initially suspected clostridial disease but submitted a ewe for post mortem when vaccination failed to halt the losses. Fascioliasis is being reported on a frequent basis this year, probably due to the wet summer on some farms, where the disease had not caused significant clinical problems in previous years.
Pigs Weaned pigs with a history of diarrhoea and high mortality were submitted to Limerick. Post mortem examination showed lesions of necrotic typhilitis and colitis. Salmonella typhimurium was isolated on culture. One of the four piglets submitted also showed lesions of septicaemia. Fibrinonecrortic gastritis and typhilitis was observed in a weaned pig submitted to Dublin. Salmonella typhimurium was also isolated from that case.
Other Species Salmonella typhimurium was isolated from the faeces of a foal submitted to Athlone. The foal had a history of scour and depression. Salmonella typhimurium had been isolated on the stud farm twice in the previous 15 months. At least thirty mares had passed through the farm in 2007, many of which were kept on farm for a number of weeks. The same paddock has been used for a number of those staying on the farm so advice was given about how this could be better managed. Limerick diagnosed acute suppurative pneumonia in a seven-month old donkey. Streptococcus equi subspecies zooepidemicus was isolated on culture.
A five-month old farmed deer was presented to Athlone following a sudden death. Large numbers of very small lungworm were evident on the cut surface of the lungs. Treatment of other deer in the group was advised. A red kite (Milvus milvus) was submitted to Dublin with a fractured wing, ruptured proventriculus and liver and aspiration pneumonia. It was thought to have been hit by a train while scavenging on a dead pheasant. Trace levels of alphachloralose were found in tissue samples but it was considered that this poison did not play a role in the bird's death.
Limerick was presented with a five-month old greyhound showing clinical signs of hind limb ataxia that had worsened over a two-month period. The pup was one of a litter of seven, the dam of which had been purchased in England after a leg injury had prematurely ended a promising racing career. Two of the littermates had died within a few days of birth and another two had been killed following an attack by another dog. The two other surviving littermates appeared to be normal. Gross post mortem examination did not reveal any significant lesions, but histopathological examination of the brain revealed multifocal lesions of non-suppurative encephalomyelitis. Scattered throughout the brain also were numerous tissue cysts (figure 2) that were consistent with those seen in protozoan infection. Immunohistochemical staining using Neospora caninum antibody was positive (figure 3). Following this result the two surviving littermates were blood sampled and were found to be serologically positive for Neospora caninum antibodies. The dam (pregnant again) is now being tested.
CAPTIONS FOR PHOTOS
Figure 1