July 2010 RVL Monthly Report
Dublin diagnosed cerebro-cortical necrosis (CCN) in a four-month-old calf, which also had a very high strongyle egg count of 11,400 eggs per gram of faeces. Sligo also diagnosed CCN in a group of four-month-old calves which had presented with scour and blindness antemortem.
Dublin diagnosed a case of pituitary abscessation in an adult dairy cow which presented antemortem with head tilt, disorientation and ataxia. The cow responded to antibiotic therapy, but the symptoms recurred upon completion of the course. On post mortem examination the pituitary abscess was found to track caudally underneath the dura mater to form an abscess at the foramen magnum (Figure 1). Arcanobacterium pyogenes was cultured from the abscess. Pituitary abscesses in cattle are rare and their epidemiology is unclear. Dublin also diagnosed summer mastitis in an adult dairy cow; Arcanobacterium pyogenes was isolated from mammary tissues.
Figure 1: Abscessation at the foramen magnum of an adult dairy cow.
Clostridial diseases were diagnosed on a number of occasions in July. Limerick was presented with a two-year-old bull with a history of inappetence and swelling on the side of the neck shortly before death. Post mortem examination revealed severe subcutaneous oedema around the head and neck area and large volumes of blood stained fluid were found in thoracic and abdominal cavities; these findings were consistent with malignant oedema (Clostridium novyi infection). Athlone found a severe emphysematous abomasitis in a six-week-old calf which presented with acute abdominal swelling antemortem. Clostridium septicum was detected in affected tissue using the fluorescent antibody technique.
Limerick diagnosed mucosal disease in an 18-month-old Charolais cross heifer with a history of watery diarrhoea and buccal ulcerations; the animal had become moribund ante mortem. Post mortem examination of the heifer revealed buccal and oesophageal ulceration and oedema of the abomasal mucosae. BVDV antigen was detected in tissues and testing of others in the group was advised, particularly as other members of the group were affected by diarrhoea. Sligo diagnosed persistent BVDV infection in both a cow and her calf. Both were found to be viraemic. The calf had a history of chronic pneumonia, while earlier progeny of the same cow had histories of ill-thrift.
Pneumonia was a frequent finding in July. Kilkenny isolated Haemophilus somnus from the lungs of a five-month-old calf with a history of pneumonia. Gross examination of the carcass revealed that over 90% of the lung tissue was consolidated. No other pathogen was detected. From a separate outbreak of pneumonia in a different herd, two calves were submitted to Kilkenny for post mortem examination. One of them was three weeks of age and the second was six weeks old. Haemophilus somnus was isolated from the three-week-old calf, and Mannheima haemolytica was isolated from the six-week-old calf. Histopathology revealed a fibrinosuppurative necrotising bronchopneumonia in both of these calves. Athlone diagnosed chronic diffuse fibrosing alveolitis in a seven-year-old cow which had clinical symptoms of pneumonia for four days ante mortem. Extensive pulmonary consolidation was found on gross examination of the carcass, and the diagnosis was based on histopathology. Diffuse fibrosing alveolitis is a chronic progressive respiratory disease of undetermined cause, but it may represent the end stage of a hypersensitivity pneumonitis. Cork necropsied a five-month-old calf, which suffered respiratory distress ante mortem. This calf was one of a group of 47, which had suffered from ill-thrift and pneumonia over the summer. The five-month-old calf had consolidated lungs, emphysema was evident and lungs worms were found in the airways (Figure 2). Histological examination of tissues revealed the presence of lungworm larvae in the alveoli.
Figure 2: A lungworm (Dictyocaulus viviparous - arrowed) within the lumen of a pulmonary bronchiole of a five-month-old calf. H&E stain, magnification x20.
Like pneumonia, Salmonellosis is a common finding in cattle, and July was no exception. Kilkenny diagnosed salmonellosis in two emaciated calves from the same herd, one was two months of age and the second was three months old. One of the two had a navel abscess while both had a fibrinous enteritis. Salmonella dublin was isolated from several organs in both calves. Kilkenny frequently isolated Salmonella dublin from adult cows also. Most had similar clinical signs ¿ pyrexia, severe watery diarrhoea which often contained blood, and these cows frequently presented with tenesmus. Intestinal incarceration in an umbilical hernia was also diagnosed as the cause of the death in a calf submitted to Kilkenny. Mesenteric torsion was diagnosed in two calves, each from two separate premises. Both had similar histories of sudden death.
Athlone investigated an outbreak of ragwort poisoning which resulted in the deaths of 12 cattle approximately 18 months of age. Clinical signs included scouring, ill-thrift, stiffness, stupor and rectal prolapse. Fibrosis, megalocytosis and necrosis was evident on histopathological examination of the liver, while spongiform change consistent with hepatic encephalopathy was found in the brain. Hyoalbuminaemia was a consistent finding in affected animals, most probably due to impaired protein synthesis by the damaged liver of affected animals. The silage was considered to have been the most likely source of the ragwort. Limerick diagnosed chronic copper poisoning in a four-year-old cow. Investigations into possible sources of the copper are ongoing.
Liver fluke and rumen fluke eggs were detected regularly in submitted bovine faeces samples in July. Kilkenny, for example, detected liver fluke and rumen fluke eggs in faeces from cows on good grass, which suffered from milk drop. Given the greater pathogenicitu of liver fluke, it is most likely that it was responsible for their production losses, as is the case in most mixed infections of liver fluke and rumen fluke.
Dublin investigated ill-thrift and mortality in a group of three-month-old lambs. One lamb was submitted for post mortem examination and was found to have a subcutaneous abscess in the submandibular area. This abscess was communicating with the lumen of the pharynx adjacent to the left tonsil. The lamb also had a secondary bacterial aspiration pneumonia. The changes encountered were consistent with dosing gun injury and the herdowner confirmed that the lambs were being dosed on a fortnightly basis with a cobalt drench.
Kilkenny found toxic levels of cobalt in the liver of a lamb, while Athlone diagnosed copper poisoning in the case of a four-year-old ewe submitted with a history of sudden death. `Port wine coloured¿ urine was found in the urinary bladder of this ewe and the kidneys were dark in colour. Copper in both liver and kidney was found to be at toxic levels. Athlone again diagnosed copper poisoning in a two-year-old ewe from a separate flock. This ewe had a history of sudden death and, on PM examination, dark discoloration of the kidneys was evident while tissue copper levels in samples orf fresh liver and kidney were very high.
Athlone diagnosed severe liver fluke infection in a two-year-old ewe with a history of sudden death. Post mortem examination revealed severe acute and severe chronic liver fluke damage in the liver with adult flukes present in the gall bladder and liver fluke eggs in the faeces. Athlone also diagnosed this condition in a five-year-old ewe from a separate flock. Salmonellosis was confirmed in sheep in July by Kilkenny; Salmonella dublin was from a three-month-old lamb which died suddenly.
Dublin diagnosed colisepticaemia in hens with fibrinous peritonitis, while Athlone diagnosed egg peritonitis in a broiler with a history of sudden death. Post mortem examination of the broiler revealed a large volume of fluid pus in the abdomen and an egg lodged in the oviduct; Escherichia coli was isolated from the pus. Sligo diagnosed aspergillosis in a Striated Carcara chick from a zoological collection that had a history of food regurgitation, weakness and death. Sligo also diagnosed Histomonas meleagridis (blackhead) infestation in a group of six peafowl which all died over a period of one month. The most striking lesion was bilateral necrotic typhilitis with caseous cores (Figure 3).
Figure 3: Bilateral necrotic typhlitis in a peafowl infected with Histomonas meleagridis.
Dublin investigated unilateral inguinal hernias in a pig herd, which was resulting in high condemnation rates at the abattoir. These congenital hernias increased in size as the pigs got older and resulted in peritonitis. The hernias were most likely genetic in origin (Figure 4). Limerick saw a six-month-old piglet with a history of pyrexia and dyspnoea. Post mortem examination revealed diffusely consolidated lungs and Mannheima haemolytica was isolated from affected tissues.
Figure 4: Inguinal herniation in a pig.
Athlone examined a three-month-old foal which was reported to have been lethargic over a period of 24 hours ante-mortem. The carcass was dehydrated and there was unilateral right-sided pulmonary congestion and consolidation. Histology revealed a diffuse suppurative bronchopneumonia and Streptococcus equi zooepidemicus was isolated from the lung tissue. Streptococcus equi zooepidemicus is a commensal of the upper respiratory tract which can act as an opportunistic pathogen in pneumonia.