July 2011 RVL Monthly Report
Sligo reported the frequent submission of large stillborn calves that had died as a result of dystocia. Some such calves survived for just a matter of hours or a few days post partum, and bore evidence of dehydration and metabolic acidosis. Umbilical infections with associated peritonitis in calves were also reported by Sligo. Dublin examined a three-day-old calf which had a history of collapse and pyrexia. Fibrinosuppurative peritonitis and low Zinc Sulphate Turbidity Test (ZST) levels were evident on post mortem examination and Escherichia coli was isolated from several organs, colisepticaemia linked with inadequate colostral antibody transfer was diagnosed. Kilkenny examined a calf which, at two days of age, had developed nervous signs and an unwillingness to suckle, necropsy revealed suppurative meningitis, and again the isolation of E. coli from several organs including the brain confirmed colisepticaemia. Dublin examined a pair of two-week-old calves from the same premises which had been suffering from chronic recurrent diarrhoea, Cryptosporidium oocysts were detected in faeces and inadequate maternal antibodies were detected in blood using ZST. Another calf from the same premises was submitted to Dublin with a history of recurrent diarrhoea and weakness. Post mortem examination revealed thickening of the ruminal and reticular walls. Examination of these lesions using histopathology confirmed a diagnosis of mycotic rumenitis. Functional failure of the oesophageal groove was considered the most likely cause of the pathological changes as a large clot of milk was found in the rumen. Limerick detected a low ZST level of just 11 units in a one-week-old calf with a history of depression and foul smelling diarrhoea. Rotavirus was detected in a faecal sample from the calf.
Diseases of the nervous system were frequently encountered by the veterinary laboratory service in July. Limerick diagnosed lead poisoning in a three-month-old suckler calf which had been found dead. Two other calves from the same group had died in similar circumstances. Lead assay revealed toxic levels of lead in a sample of fresh kidney, confirming the diagnosis. Dublin diagnosed lead poisoning in a nine-month-old Friesian heifer which was found laterally recumbent and frothing at the mouth. Four other cohort animals had also died after acute nervous illness, and a search of the pasture revealed battery cell remnants. Cork investigated the sudden death of a one-year-old heifer and found toxic levels of lead in renal tissue, in this case, however, the source of the lead was not found. Dublin investigated the death of a four-month-old calf which had suffered an acute episode of rigid paralysis of forelimbs and muscle tremors, three other cohort calves were also affected by similar clinical signs. Apple-green fluorescence was evident on UV illumination of a section of the brain (Figure 1), while histopathology of the brain confirmed the diagnosis of Cerebro-Cortical Necrosis (CCN). Limerick also diagnosed CCN in a five-month-old calf with a history of loss of balance and opisthotonos, and again UV fluorescence suggested CCN, which was confirmed by histopathology. Histopathology of the brain also confirmed CCN in an 18-month-old bullock submitted to Athlone; an acute episode of staggering ante mortem had been reported in this case.
Figure 1: Fluorescence of cut section of brain under UV illumination, taken from a four-month-old calf with Cerebro-Cortical Necrosis (CCN). Photo: Colm Brady
Clostridial disease was prevalent in July. Limerick examined a six-month-old weanling which was found in severe distress, with its head swollen and a bloody nasal discharge evident. The left masseter muscle was found to be dark and emphysematous on post mortem examination, and the detection of Clostridium chauveoi in smears from the affected muscle using the Fluorescent Antibody Technique (FAT) was confirmatory for clostridial myositis (Blackleg). Sligo also reported several cases of blackleg submitted in July. Limerick necropsied a four-week-old calf with a history of sudden death, and found emphysematous abomasitis consistent with clostridial infection. Sligo found oedematous abomasitis on necropsy of a two-month-old beef calf. Again FAT was applied to smears from the lesion and Clostridium sordelli was detected. Athlone investigated the sudden death of a six-year-old cow; rapid autolysis was evident and Clostridium sordelli was isolated from tissues. Prompt clostridial vaccination of the herd with a multivalent vaccine that included a C. sordellii component was advised. Athlone noted emphysematous myositis in the neck muscles of an 18-month-old bullock, and again Clostridium sordelli was isolated from the lesion. This pathogen has been implicated in the literature in such localised infections. Athlone investigated the death of a two-year-old heifer which had been reported to be recumbent and dyspnoeic ante mortem. On post mortem examination diffuse oedema of abdominal fat and mesentery was in evidence, while a focal brown lesion 2.5 cm in diameter was also found in the liver. Histopathology of the liver revealed evidence of liver fluke infection, while examination of the focal brown lesion revealed coagulative necrosis consistent with Infectious Necrotic Hepatitis (Black Disease).
Kilkenny investigated the death of a two-month-old calf with a history of poor thrive, where post mortem examination revealed cachexia. In further examinations, Salmonella Dublin was isolated from the tissues. In a separate case Kilkenny diagnosed salmonellosis in a five-month-old calf with a history of chronic scour. Salmonella Dublin was isolated from faeces and a high faecal strongyle egg count was also detected. Athlone necropsied a six-week-old calf which was severely dehydrated, with watery and haemorrhagic intestinal contents, Salmonella Dublin was isolated from these contents. Dublin isolated Salmonella Dublin from a faecal sample taken from a cow which had presented with watery diarrhoea, pyrexia and reduced milk yield.
Limerick diagnosed parasitic pneumonia (hoose pneumonia) in a calf with a history of poor thrive which had suffered an acute episode of respiratory distress ante mortem. Large numbers of lungworms were evident in the bronchial tree, while a faecal egg count of 5000 strongyle eggs per gram was indicative of poor parasite control practices on the farm. Dublin diagnosed parasitic pneumonia in a 20-month-old heifer which was one of a group of heifers which were reported to be coughing. While hoose more usually occurs in younger calves during their first grazing season, failure to develop immunity at this early stage of life, perhaps due to inadequate exposure to larvae, can result in disease during subsequent grazing seasons. Limerick isolated Histophilus somnus from the pneumonic lungs of a calf while Athlone diagnosed multifocal necrotising pneumonia in a two-month-old calf. The histological changes encountered by Athlone were consistent with Mycoplasma pneumonia while immunohistochemistry (IHC) was confirmatory for infection with Mycoplasma. Sligo reported a number of separate unconnected cases of pneumonia in calves caused by Mannheima haemolytica; necropsy revealed pneumonic lesions in all cases, with pleuropneumonia and pericarditis seen occasionally as sequelae.
The veterinary laboratory service encountered a number of cases of Bovine Viral Diarrhoea Virus (BVDV) infection in July. Limerick detected BVDV in the tissues of a one-day-old calf with a history of weakness since birth. Intra abdominal haemorrhage was evident on post mortem, which was associated with a ruptured kidney. Dublin investigated the death of a three-month-old calf with a history of chronic pneumonia which was unresponsive to antibiotic therapy. Post mortem examination revealed chronic necrotising pneumonia, and Arcanobacterium pyogenes was isolated from the lesion. Concurrent BVDV infection was also indicated by detection of the virus in tissues. Kilkenny investigated the death of a two-year-old heifer with a history of pining ante mortem. Post mortem examination revealed interdigital skin ulceration in both hind feet, tonsillar crypt necrosis, linear ulceration of oesophageal mucosal lining and pulmonary abscessation. BVDV was detected in the tissues using PCR and Mucosal disease with chronic suppurative pneumonia was diagnosed.
Renal disease, which is uncommon in cattle was reported from a number of cases. Athlone examined a three-year-old cow with a history of chronic pining ante mortem, where post mortem examination revealed cystic cavitation and suppuration of both kidneys. Purulent ureteritis and cystitis were also present and pyelonephritis was diagnosed. Kilkenny diagnosed pyelonephritis in a cow which had been recumbent for a few days ante mortem. Arcanobacterium pyogenes was isolated from the lesions. Kilkenny also identified kidney disease in an 18-month-old bull with a history of pining where post mortem examination revealed severe chronic nephritis.
Other interesting cases seen in July included a recently purchased six-week-old calf submitted to Dublin with a history of inappetence for three days ante mortem. Post mortem examination revealed fibrinosuppurative peritonitis (Figure 2) and a perforating abomasal ulcer. Athlone found a perforating abomasal ulceration and peritonitis at the necropsy of a two-month-old calf with a history of tenesmus and diarrhoea. Athlone also diagnosed hypertrophic cardiomyopathy in a two-month-old calf, where the heart was found to be enlarged on post mortem examination, with thickening of the right ventricular wall and endocardial fibrosis. Hepatomegaly was also observed, resulting from congestive heart failure. Kilkenny necropsied a five-month-old calf and found diffuse peritonitis and pericarditis. Scarring of the ruminal wall was suggestive of traumatic rumenal foreign body penetration, a likely portal of entry of infection. Kilkenny also diagnosed parasitic gastroenteritis in a five-month-old dehydrated calf with a severe scour. Faecal examination (McMaster technique) confirmed the diagnosis. Cork necropsied an eight- month-old calf with a history of ill thrift and found generalised symmetrical peripheral lymphadenopathy and bilateral multifocal well-demarcated raised white circular solid masses in the kidneys. Histology confirmed juvenile (multicentric) lymphoma where diffuse populations of large cleaved-type neoplastic cells infiltrated lymphoid tissue, and the liver and kidney (Figure 3). Sligo recorded a number of cases of babesiosis (redwater), where the carcasses presented with classical gross findings on post mortem: they were anaemic, dehydrated and icteric.
Figure 2: Diffuse fibrino-suppurative peritonitis in a six-week-old calf with a perforating abomasal ulcer. Photo: William Byrne
Figure 3: Photomicrograph of diffuse infiltration of large cleaved neoplastic cells into kidney of an eight-month-old calf with lymphoma. Photo: Cosme Sanchez
Kilkenny isolated Salmonella Dublin from the stomach contents and placenta of a five-month-old foetus, one of several abortions in the same herd. Dublin isolated Streptococcus bovis from the abomasal contents of a seven-month-old bovine foetus. This organism is associated with sporadic abortion in cattle.
Athlone necropsied a four-month-old lamb with a history of a stumbling gait and a presumptive diagnosis of CCN was indicated by fluorescence under UV light – histological confirmation is awaited. Dublin examined a five-month-old lamb from a flock with high lamb mortality. The lamb’s clinical history described weakness and inappetence. Hypoproteinaemia, cobalt deficiency and a high Nematodirus battus faecal egg count were found on post mortem examination. Athlone also diagnosed parasitic gastroenteritis in a number of submitted adult ewes an unusual finding in adult sheep. Athlone diagnosed copper poisoning in a 12-week-old lamb which was the eleventh lamb to die in the flock in a three week period. Dark discoloration of the kidneys and haemoglobinuria were noted. In a separate case, Athlone diagnosed copper poisoning in two ewes, where both carcasses were found to be jaundiced on post mortem examination. All of the kidneys were dark and biochemical analysis of tissues confirmed the diagnosis. Sligo diagnosed chronic bilateral pyelonephritis in an adult ewe with a history of passing bloody urine, on post mortem examination a cavernous outpouching of the right ureter was found, which contained a large volume of bloody purulent material, and similar material was found in the bladder.
Cork isolated Salmonella Typhimurium from three canaries which belonged to a colony of thirty which were experiencing ongoing losses; enteritis was evident on post mortem examination. Cork was also involved in an investigation into neurological disease in racing pigeons affecting three different lofts, paramyxovirus (PMV 1) was detected in these pigeons confirming Newcastle disease. Dublin investigated increased mortality of chicks in a broiler flock, where multifocal necrotising hepatitis was found on post mortem examination of the birds. Clostridium perfringens was isolated on culture. In a separate case, Dublin examined a hen from a backyard flock, which had been the third to die in as many days. This particular hen had been reported to be inappetent ante mortem. Post mortem examination of the hen revealed severe peritonitis, while three misshapen eggs were present in the oviduct. E. coli was isolated from peritoneal surfaces; Mannheima haemolytica was isolated from one of the abnormal eggs, M. haemolytica has been previously reported as a co-pathogen in peritonitis and salpingitis in hens.