September 2011 RVL Monthly Report
Dublin diagnosed colisepticaemia in a two-day-old calf which had been healthy for the first 12 hours post partum but then rapidly became depressed and died. Post mortem examination revealed omphalitis, dehydration and widespread ecchymotic haemorrhages in the subcutis and on serosal surfaces. Escherichia coli (E. coli) was isolated from several organs and the Zinc Turbidity Test (ZST) revealed a low reading consistent with poor transfer of maternal immunoglobulin. Kilkenny necropsied a one-day-old calf with a history of recumbency ante mortem. The ZST revealed a poor transfer of maternal immunoglobulin, while gross post mortem examination revealed a fibrinous peritonitis, and subsequent isolation of E. coli from organs was consistent with colisepticaemia. Sligo reported peritonitis in a number of neonatal calves which had low serum immunoglobulin concentrations.
Kilkenny necropsied a two-day-old calf with a history of dyspnoea and failure to stand and suckle. It had been stomach tubed with colostrum. Its lungs were oedematous and there was milk in the trachea and bronchi where histopathology revealed meconium, foreign material and bacterial colonies in airways and alveoli. A diagnosis of aspiration pneumonia was indicated. Dublin examined two Friesian calves, each approximately four-months-old, with a history of pneumonia for a few days ante mortem. Several other calves from the group were suffering from pneumonia. These calves had been turned out to grass one month before the onset of clinical signs. In both cases, post mortem examination revealed widespread bullous emphysema, associated with an infestation of lungworm. Parasitic pneumonia (hoose) was diagnosed. Kilkenny also saw parasitic pneumonia in a five-month-old weanling reported to have had respiratory distress for 48 hours ante mortem. Emphysematous pneumonia was observed on gross post mortem examination, with large numbers of lungworm in the bronchial tree. Sligo saw a six-month-old calf which had a history of pneumonia with coughing which had been euthanased by the veterinary practitioner. Consolidation of both lungs was revealed on gross post mortem examination, while histopathology revealed suppurative bronchopneumonia, granulomatous and lymphocytic cuffing of bronchioles and proliferation of Bronchiole Associated Lymhoid Tissue (BALT). These findings were consistent with enzootic (cuffing) pneumonia, usually associated with poor ventilation and Mycoplasma spp. infection.
Kilkenny examined a three-week-old calf with a history of sudden death. An atrial septal defect was identified on gross post mortem; typical sequelae to congestive heart failure, including cardiomegaly and nutmeg liver were also found. Athlone reported vegetative endocarditis was observed at the necropsy of a two-year-old heifer which had a history of intermittent pyrexia and lameness before death, which was unresponsive to treatment. Kilkenny found vegetative endocarditis (Figure 1) and valvular incompetence with nutmeg liver on post mortem examination of a cow that had a history of respiratory distress.
Figure 1: Vegetative endocarditis in a cow. Photo: Donal Toolan.
Limerick identified mesenteric root torsion on necropsy of ten-week-old suckler calf and Athlone found mesenteric root torsion in a 13-month-old bullock with a history of sudden death. Athlone made a similar diagnosis in the case of a three-year-old cow submitted with a similar history when a 180-degree torsion of the large and small intestine around the root of the mesentry was identified on post mortem examination.
Kilkenny diagnosed mycotic ulcerative abomasitis in a 10-week-old calf while Limerick diagnosed perforating abomasal ulceration in a seven-week-old suckler calf with a history of sudden death. Dublin necropsied a three-week-old bucket reared calf that had presented with a history of bilateral bloating and constipation and found an acute diffuse peritonitis with ingesta present in the peritoneal cavity. Contamination of the peritoneum had evidently arisen from perforating abomasal ulceration. Dublin also found perforating abomasal ulceration and peritonitis in a two-month-old bucket-fed calf with a history of depression for one week, and abdominal distension for two days, ante mortem.
Athlone examined a six-week-old calf with a history of constipation that was found to have ulceration of the pylorus, ulcerated diphtheritic Peyer’s patches and extensive diphtheritic ulcerative colitis. While Bovine Virus Diarrhoea Virus (BVDV) infection was considered a possibility, PCR testing of tissues yielded a negative result for BVDV. Histopathology revealed necrotic enteritis with numerous thrombi containing fungal hyphae. Based on the history, a tentative diagnosis of Idiopathic Necrotic Enteritis with fungal septicaemia arising from prolonged antibiotic therapy was made.
Athlone diagnosed Malignant Oedema as the cause of death of two seven-month-old weanlings, which, were found to have marked emphysematous myositis around the neck at post mortem examination. The herdowner had not practiced clostridial vaccination but was advised to do so to prevent further losses. Cork found haemorrhagic myositis in the neck of a seven-month-old weanling that died rapidly following a short episode of scouring. A pure growth of Clostridium sordelli was isolated from muscles of the neck, and tissue samples also tested positive for BVDV antigen. This unusual presentation may have been facilitated by BVDV-related immunosupression. Kilkenny diagnosed Clostridium sordelli enterotoxaemia in three weanlings from the same herd which had been found dead. Intra-luminal intestinal haemorrhage was the main gross post mortem finding while Fluorescent Antibody Technique (FAT) testing of affected tissue yielded a positive result for Clostridium sordelli. Sligo reported seeing several cases of Malignant Oedema in September while other clostridial disease seen by Sligo included Black Disease (Figure 2) and Blackleg.
Figure 2: Scleral oedema in a bovine with Black Disease. Photo: Colm Ó Muireagáin.
Limerick examined an 18-month-old Hereford cross heifer with a history that described a sudden onset of severe watery diarrhoea and depression for a few days ante mortem. Ulceration of the caecal mucosae was found on post mortem examination, and BVDV antigen was confirmed on PCR testing. From a separate herd, Limerick necropsied an 18-month-old heifer with a history of chronic diarrhoea, wasting and dehydration; BVDV infection was confirmed in this case, also using PCR.
Kilkenny examined a five-month-old weanling which was frothing at the mouth and showing nervous signs, and was subsequently euthanased. Gross post mortem revealed laminar fluorescence of cerebral cortex under ultra-violet light, while histology confirmed Cerebro-Cortical Necrosis (CCN). Kilkenny also examined an 18-month-old bull which became progressively stiff and eventually recumbent over a period of five days ante mortem. Another animal from the group had died in similar circumstances while a third animal was showing similar clinical symptoms at the time of submission. Biochemical analysis of tissues revealed toxic levels of lead in the kidney, confirming lead poisoning.
The Regional Veterinary Laboratory service received 336 bovine milk samples for culture and antibiotic susceptibility testing during September, Staphylococcus aureus was isolated from 166 samples (49.4%) (Table 1) while antimicrobial susceptibility testing was carried out on 72 of the Staphylococcus aureus isolates (Table 2). Bulk tank samples are unsuitable samples for submission where herdowners are planning blanket dry cow therapy. Selecting a small number of high somatic cell cows from the herd and taking composite samples from these in a sterile fashion will yield better quality, uncontaminated samples and more reliable laboratory results.
September 2011 table 1: milk isolates (doc 61Kb)
Table 1: Pathogens isolated by the Regional Veterinary Laboratory service from 336 milk samples submitted in September. Courtesy Alan Johnson.
September table 2: AMR testing of milk (doc 54Kb)
Table 2: Results of antmicrobial sensitivity testing carried out on 72 isolates of Staphylococcus aureus Isolated from milk samples submitted to the Regional Veterinary Laboratory service in September. Courtesy Alan Johnson.
Sligo investigated a problem of high Somatic Cell Count (SCC) in a dairy herd and found that Staphylococcus aureus and Streptococcus dysgalactiae were commonly isolated from samples arising from the investigation. It was concluded that there was a core of infected cows contributing to the mastitis breakdown, investigations also revealed evidence of teat damage and inadequate disinfection. Recommendations given to the herdowner included culling of problem cows improved post milking teat disinfection, and servicing of the milking machine.
Sligo necropsied seven bovine foetuses submitted from an abortion outbreak in a dairy herd. While Neospora caninum antibodies were detected in the thoracic fluid of three foetuses, histological examination of submitted placentae revealed changes that were more suggestive of Q fever. The serum from 43 cows was screened for routine post-abortion serology and 13 were found to be seropositive for Coxiella burnetii, the pathogen that causes Q fever.
Salmonella-related abortion was frequently diagnosed in September. Kilkenny isolated Salmonella Dublin from seven submitted foetuses, while Athlone isolated Salmonella Dublin from the abomasal contents of a foetus which had been aborted at five months gestation; this was the second abortion in the herd over a few days. Dublin isolated Salmonella Dublin from the abomasal contents of an aborted bovine foetus close to term; this was the third such abortion in the herd in a short number of days. From a separate herd, Dublin isolated Salmonella Dublin from placenta of a seven-month-old aborted foetus; it was the first such abortion in the herd that season.
Other abortifacients detected in September included an Arcanobacterium pyogenes isolated from the stomach contents of a seven-month-old aborted foetus submitted from a dairy herd; this was the only abortion which had occurred in the herd. Arcanobaterium pyogenes is normally regarded as a sporadic abortifacient. Dublin also detected bovine herpesvirus 1 (BHV-1/IBR) by PCR in the spleen of a six-month-old aborted foetus. This had been the second abortion in a dairy herd of 120 cows. Kilkenny isolated Bacillus licheniformis and Aeromonas hydrophila from the abomasal contents of aborted foetuses from different holdings . Athlone necropsied an eight-month-old foetus which had been the fifth to be aborted from the same group of heifers. Histopathology revealed brain lesions consistent with mycotic encephalitis indicating a diagnosis of mycotic abortion. Mycotic infection can arise if the pregnant animal is fed mouldy feed or develops rumenal acidosis and rumenitis while pregnant.
Cork diagnosed three cases of louping ill from two separate flocks, one two-year-old ewe from one flock and two six-month-old lambs from the other. Neurohistopathology in these cases revealed non-suppurative meningo-encephalitis, perivascular lymphocytic infiltration, glial nodules, neuronal necrosis and neuronophagia (Figure 3) – lesions consistent with Louping ill. Sligo diagnosed louping ill in a one-year-old hogget, which had neurohistopathological lesions consistent with the disease; several ticks were evident on the carcass.
Figure 3: Neuronal necrosis and neuronophagia in a six month old lamb with Louping ill. Photo: Cosme Sanchez
Parasitic gastroenteritis was diagnosed by Sligo in a six-month-old lamb which showed severe dehydration, faecal staining of the perineal area and a raised faecal strongyle egg count, Sligo reported several such cases of parasitic gastroenteritis in sheep usually affecting lambs. Kilkenny examined a five-year-old ewe with a history of sudden death, post mortem examination revealed a severe liver fluke infestation, and culture of intestinal contents revealed concurrent infection with Salmonella Typhimurium.
Athlone diagnosed copper poisoning in a one-year-old ram, which on necropsy was found to be icteric. The kidneys were darkened in appearance and haemoglobinuria was in evidence while toxic levels of copper, were detected in the kidneys. Sligo confirmed copper poisoning in a ram; icterus and haemoglobinuria were found on post mortem while diagnosis was confirmed on biochemical analysis of tissues.
Pneumonia due to Mannheima haemolytica was diagnosed by Athlone in a six-month-old lamb which had been found dead, the third such death in the group in a week. Salmonellosis was diagnosed in a ewe which was one of seven to die out of the same group within a short period of time; Salmonella Arizonae was isolated from faeces and tissues. A Charolais hogget ewe with a history of ataxia and difficulty in standing was submitted to Dublin. Post mortem examination revealed abscessation of the lung and pituitary gland. Arcanobacterium pyogenes was isolated from both abscesses suggesting haematogenous spread of the pathogen from the pulmonary abscess to the pituitary gland.
Athlone observed bilateral sinusitis in a hen submitted from a flock which had suffered 20 mortalities in three weeks, and subsequent PCR testing of the affected tissues revealed Mycoplasma gallisepticum infection. Dublin also diagnosed Mycoplasma gallisepticum infection in a six-week-old pullet which presented with pus filled sinuses on post mortem examination, and PCR testing of tissues confirmed presence of the pathogen. In a separate case, Dublin diagnosed a mixed respiratory infection in a backyard flock of hens reported to have raised mortality. Clinical signs included sneezing, mouth breathing, and purulent ocular and nasal discharges. Infectious Laryngotracheitis was diagnosed based upon histopathology, however laboratory testing also revealed evidence of infection with Mycoplasma gallisepticum, Pasteurella multocida and Infectious Bronchitis Virus. Cork diagnosed Mycoplasma gallisepticum infection in two separate backyard flocks and in one of the two cases, concurrent Infectious Bronchitis Virus infection was also detected. Limerick examined a seven-week-old Maran hen submitted from a flock where five out of 25 birds had died with clinical signs of gasping, poor appetite and swelling around the eyes. Post mortem examination revealed blood and mucous in the trachea while both Infectious Bronchitis Virus and Mannheima haemolytica were detected in the lungs, Mannheima haemolytica is thought to be, in most cases, a secondary invader of the respiratory tract in poultry.
Dublin examined a number of broiler chickens from a flock with a history of lameness. Post mortem examination revealed swollen feet (Figure 4) and hocks. Staphylococcus aureus was isolated from brown serous exudates collected from swollen feet joints (proximal metatarsus), flexor tendons and swollen hock (tarsal) joints indicating a diagnosis of staphylococcal arthritis and tenosynovitis. Limerick examined an eight-week-old broiler from a backyard flock with a history of poor locomotion and diarrhoea. Gross examination revealed septic arthritis of the elbow (radio-ulnar) joint while Staphylococcus aureus was isolated from the affected joint and the liver.
Figure 4: Swollen foot in a broiler chicken with staphylococcal arthritis and tenosynovitis. Photo: William Byrne
Kilkenny examined a 19-week-old chicken with a history of coughing for four weeks ante mortem, where pulmonary histopathology revealed multifocal aggregates of cryptosporidial oocysts surrounded by lymphohistiocytic inflammation, indicating a diagnosis of pulmonary cryptosporidiosis. From a separate flock, Kilkenny examined two pheasants in poor body condition and found Hexamita protozoa on intestinal smears confirming a diagnosis of Hexamitiasis. Limerick found haemorrhagic intestinal contents on post mortem examination of a ten-week-old broiler, submitted from a flock of 80 birds that had suffered 20 mortalities. Very large numbers of coccidial oocysts were found in faeces indicating coccidiosis while the isolation of Mannheima haemolytica from lung tissue indicated concurrent Mannheimosis.
Dublin observed fibrinous peritonitis, pericarditis and air-sacculitis in a number of 40-week-old layer hens submitted from a flock with a mortality of up to 15 birds per day. E. coli was isolated from organs leading to a diagnosis of colisepticaemia. Limerick also diagnosed colisepticaemia in two one-week-old chicks, bacteriology confirmed the diagnosis.
Dublin diagnosed alphachloralose poisoning in a red kite which had been found dead. The diagnosis was made on the basis of toxicological testing which indicated the presence of the poison in tissues.
Hepatic lipidosis (Figure 5) was diagnosed by Dublin in the case of a two-year-old male alpaca which was found dead. Petechial and eccymotic haemorrhaging was observed in subcutaneous tissues, over the pericardium, epicardium and endocardium, the liver was pale with a marked reticular pattern, and bilirubin crystals detected in the urine were indicative of cholestasis. Hepatic lipidosis is a recognised problem in camelids and is thought to be nutritional in origin.
Figure 5: Vacuolation of hepatocytes with bile retention in the liver of an alpaca with hepatic lipidosis. Photo: Ann Sharpe