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October 2010 RVL Monthly Report

Cattle

October saw a high number of pneumonia cases; parasitic pneumonia (hoose) in particular was a recurrent diagnosis. Dublin investigated the death of a nine-month-old Montbeliarde weanling which had died suddenly; many others in the same group were coughing and a few from the group had died. Heavy lungworm infestation was confirmed in the weanling on necropsy (Figure 1).  Athlone diagnosed parasitic pneumonia in an 18-month-old heifer which had respiratory distress for 24 hours ante mortem. Gross post mortem examination revealed severe bilateral pneumonia and heavy lungworm infestation of airways, while dilation of the right ventricle of the heart and severe congestion of the liver were consistent with right sided congestive heart failure. Athlone also diagnosed severe parasitic pneumonia in a six-month-old calf which had a history of coughing and pyrexia. On necropsy there were abundant lungworms  in the lumen of the bronchi and lower airways.  

Lungworm in trachea

Figure 1: Lungworm (Dictyocaulus viviparus) infestation of the trachea in a nine-month-old Montbeliarde weanling. Photo: William Byrne

Athlone investigated an outbreak of pneumonia in a group of calves, where mortalities were all under three weeks of age. All affected calves had been born from a group of nine cows which had been bought into the herd while pregnant. Evidence of enteritis, dehydration and pneumonia were found on gross post mortem examination of carcasses submitted from the outbreak, while histology revealed focal hepatitis and fungal granulomatous pneumonia. Using PCR methodology, bovine herpes virus 1 (IBR) was detected in lung tissue from the necropsied calves. All the calves from the nine bought-in cows died, while an IBR vaccination programme had been in place when the cows arrived. It was suspected that the naïve bought-in cows and their calves contracted the virus on the farm with the resultant losses. The fungal infection of lungs was considered to have been secondary to IBR in this case. Athlone also diagnosed IBR in a one-year-old bullock with severe fibrino-necrotic tracheitis and pulmonary consolidation. Small abscesses in the lung parenchyma were consistent with secondary bacterial infection; IBR was confirmed with the detection of bovine herpes virus 1 in tissues using PCR. A seven-month-old heifer submitted to Athlone showed diffuse fibrinous pleuropneumonia of the apical and cardiac lobes of the lungs, while fibrin tags were evident on pleural surfaces, BRSV infection of the lungs was confirmed using PCR.

Sligo diagnosed clostridial disease in cattle on several occasions. Blackleg was the most common manifestation of clostridial disease encountered. Invariably with these cases vaccination had not been employed, while the history was normally that of sudden death. However in exceptional cases lameness ante mortem was reported. Athlone necropsied a 2.5-year-old heifer with a history of sudden death. Darkening and emphysema of muscle along the neck was observed, and anaerobic culture of the affected muscle yielded a growth of Clostridium sordelli. Gross pathology and bacteriology supported a diagnosis of malignant oedema.  Limerick received a sample of muscle taken from a heifer presented to a meat plant for slaughter. The heifer was noticed to be stiff in her gait on ante-mortem inspection and, following slaughter, very dark lesions were detected on the upper hind limb suggesting a tentative diagnosis of blackleg.

Salmonellosis is a recurrent diagnosis in all seasons, but seems to be occurring at a high incidence this autumn and October was no exception. Sligo isolated Salmonella dublin from two calves with septicaemia which were submitted from the same large dairy unit. Among the findings in the two calves were haemorrhagic enteritis and joint ill. Dublin isolated Salmonella typhimurium from faecal samples submitted from two cows which developed a reddish-brown watery diarrhoea. Six cows at different stages of lactation from this particular herd had diarrhoea and while they responded to some degree to antimicrobial therapy, milk yield remained poor in convalescent cows. The six infected cows were quarantined in an effort to stem the spread of infection. Kilkenny isolated Salmonella dublin from faeces submitted from several scouring cows from a number of separate herds. These animals were reported to have pyrexia and watery diarrhoea which was blood stained in some cases. Athlone investigated the death of a five-year-old cow which was found weak and depressed in the morning, but which was dead within hours.  On post mortem examination, this cow was found to have pulmonary oedema, focal necrosis in the liver, the intestinal mucosa was congested, and intestinal contents were very watery. Isolation of Salmonella dublin from tissues and intestinal contents in this case confirmed a diagnosis of septicaemic salmonellosis. Limerick necropsied a calf with a history of chronic pneumonia. Clinical signs had become more severe a few days ante-mortem. Salmonella dublin was isolated from lungs, liver, spleen and intestinal contents. Septicaemic salmonellosis secondary to debilitation arising from chronic pneumonia was advanced as a possibility in this case.

Arcanobacter pyogenes was isolated from a pituitary abscess (Figure 2) found in a 15-month-old Charolais calf submitted to Dublin. The calf had a clinical history of ataxia, unilateral facial paralysis and exophthalmia. Though the condition is rare, this was the second such case submitted to Dublin in four months. Athlone accepted a four-year-old cow for post mortem with a history of dyspnoea. Necropsy of the submitted carcass revealed a restrictive pericarditis and a massive abscess in the right lung which contained up to 40 litres of foul smelling yellow turbid fluid. Though a foreign body was not found, the lesions were most likely caused by a foreign body penetration of the reticular wall and pericardium. Athlone also investigated the sudden death of a 30-month-old heifer. Necropsy revealed engorgement of rumen with large amounts of grain, while a rumen pH of 4.9 confirmed a diagnosis of acute ruminal acidosis. 

Pituitary abscess

Figure 2: Pituitary abscess in a fifteen-month old Charolais calf. Photo: William Byrne.

Bovine abortion

There was a seasonal increase in bovine abortion submissions to the laboratory service in October. Kilkenny recorded a high number of Salmonella-related abortions while Dublin isolated Salmonella dublin from an aborted foetus of six month gestational age. Its dam had been one of a number of cows to abort in a 180-cow dairy herd. Limerick and Athlone also reported several cases of Salmonella-related abortion. Vaccination and appropriate disposal of slurry or bedding material were some of the measures advised. Other infectious abortifacients diagnosed included Arcanobacterium pyogenes, Aspergillus fumigatus and BVD. In the case of one abortion submission to Athlone, while there were no significant findings on analysis of the submitted foetus, Aerococcus urinae was isolated from the placenta, while histological examination of tissues revealed evidence of bacterial placentitis. Though an uncommon abortifacient, Aerococcus urinae infection is associated with bovine reproductive disease including abortion, vulvitis, vaginitis and metritis. This latter case illustrates the importance of submitting fresh placenta if at all feasible in any abortion cases.

Sheep

Infectious disease in sheep reported in October included several cases of bacterial pneumonia submitted to Sligo RVL, Mannheima haemolytica was the most common isolate in these cases. Sligo also diagnosed a number of cases of louping ill. Neurological symptoms were common in the clinical histories of these submissions, while on post mortem examination ticks were found attached to the skin around the axilla and perineal areas. Limerick necropsied a six-month-old lamb with a history of stiffness in the neck and legs for 24 hours ante mortem. The  isolation of Salmonella dublin from the spleen, liver, lung, and brain confirmed septicaemic salmonellosis in this case. Athlone diagnosed chronic fasciolosis in a ewe which presented with severe and diffuse hepatic fibrosis, while Cork also diagnosed fasciolosis in an adult Mountain Blackface sheep which had a history of ill-thrift for a few days ante mortem. On post mortem examination the sheep was found to have poor body condition, ascites, and thick-walled, dilated bile ducts which contained liver fluke.

Kilkenny necropsied a five-month-old lamb with a history of poor condition and weakness. Tissue cobalt levels were found to be extremely low, and gross examination of tissues revealed the liver to be pale and slightly swollen (Figure 3). Histology findings were consistent with ovine white liver disease. Sligo diagnosed copper poisoning in a ram which had jaundice, haemoglobinuria and dark coloured kidneys. Copper poisoning was also diagnosed in a six-month-old lamb submitted to Cork. This lamb had severe jaundice while tissues were found to contain toxic levels of copper. Athlone examined a ram that died shortly after arrival in a new flock. The rumen was found to contain significant quantities of grain while a rumen pH of 4.7 confirmed acute ruminal acidosis. Athlone diagnosed compression fractures of cervical vertebrae 3 & 4 in a pedigree Charolais ram which had been recently imported into the submitting flock. This is an injury that typically occurs in rams in the breeding season as a result of fighting.

Pale swollen liver

Figure 3: Pale swollen liver from a five-month-old lamb with white liver disease. Photo: Donal Toolan.