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October 2011 RVL Monthly Report

Cattle

Clostridia

Limerick investigated the sudden deaths of two weanlings from the same herd. Post mortem examination revealed lesions consistent with Blackleg; such lesions were found in the heart in one case and in the ilio-psoas muscle in the other. The diagnosis was confirmed when Clostridium chauvoei was detected in lesions using Fluorescent Antibody Technique (FAT). In a separate case, Limerick confirmed Blackleg on post mortem examination of an eight-month-old weanling with a history of pyrexia and depression. Crepitus and swelling of the brisket were evident. Athlone diagnosed blackleg in an eight-month-old weanling with a clinical history of respiratory distress and pyrexia. Post mortem examination revealed cardiomyositis, fibrinous pericarditis and pleurisy. In a separate case Athlone diagnosed blackleg in a weanling when characteristic lesions were found in the psoas muscles. In both cases, multivalent clostridial vaccination of cohorts was advised. Athlone also necropsied a four-month-old calf with a history of pyrexia and kicking in pain and found circumferential gelatinous and sanguinous oedema of the subcutaneous tissue of the right limb extending from the coronary band to the level of the hip joint. Isolation of Clostridium sordellii from the oedematous lesion confirmed a diagnosis of malignant oedema. Kilkenny investigated the sudden death of a 20-month-old heifer. Haemorrhagic enteritis was found on post mortem examination while Clostridium sordellii was detected at the lesion using FAT. These findings supported a diagnosis of Clostridial enterotoxaemia. A five-year-old cow was submitted to Athlone when it died after an acute illness which lasted only a few hours. Necrotic lesions in the liver consistent with Black disease were identified in the liver. Evidence of fasciolosis was also found in this case. There is a well-established strong association between Black disease and Fasciola hepatica infestation. Sligo recorded several cases of clostridial disease in October including Black disease, blackleg and malignant oedema. Failure to provide full vaccinal cover (e.g. not vaccinating all animals, incomplete primary courses, failure to continue with booster vaccination) was common to the herd histories in these cases.

Pneumonia

Limerick diagnosed parasitic pneumonia (hoose) and parasitic gastroenteritis in an eight-month-old weanling with a history of pneumonia and pining for a few days ante mortem. Post mortem examination revealed large numbers of adult lungworms in the bronchial tree and a faecal trichostrongyle egg count of 10,000 eggs per gram of faeces was consistent with severe roundworm burden. Kilkenny investigated the death of a five-month-old weanling with a history of pneumonia. Post mortem examination revealed emaciation, subcutaneous oedema in the intermandibular space and ventral neck and also lungworm infestation of the bronchial tree. Histopathology revealed Ostertagia larvae in the abomasal gastric glands, hoose pneumonia with concurrent ostertagiosis was diagnosed in this case. From a separate herd, an 11-year-old pedigree Limousin cow which had been imported from France one year earlier, was submitted to Kilkenny with a clinical history of acute pneumonia. Post mortem findings of pulmonary emphysema and severe lungworm infestation of the bronchial tree confirmed parasitic pneumonia (hoose).

Infectious Bovine Rhinotracheitis (IBR) was diagnosed in two feedlot cattle submitted to Athlone from a feedlot unit experiencing an outbreak of pneumonia among animals which had been recently introduced into the herd. Post mortem examination revealed severe fibrinonecrotic tracheitis in both animals (Figure 1), PCR testing of lesions yielded a positive result for IBR virus, confirming the diagnosis. Sligo reported several separate cases of IBR outbreaks in October. Fibrinonecrotic tracheitis, which is characteristic of IBR, was encountered on post mortem examination of cattle submitted from these outbreaks, and secondary bacterial infection was commonly encountered in these cases, Arcanobacterium pyogenes was regularly isolated.

Tracheitis  

Figure 1: Severe fibrino-necrotic tracheitis in a feedlot weanling calf with IBR. Photo: John Fagan

Kilkenny necropsied a one-month-old calf which had a clinical history of pneumonia and scour. Several other calves in the herd were similarly affected, and these calves had been recently introduced into the herd from several different sources. Watery intestinal contents, pulmonary consolidation and tracheitis were found on post mortem examination. PCR testing of pulmonary tissue yielded a positive result for Bovine Herpes Virus 1(BHV1), Bovine Coronavirus (BoCo) and Bovine Respiratory Syncytial Virus (BRSV), while Cryptosporidium oocysts were detected in faeces. Cork diagnosed Bovine Respiratory Disease Complex in a group of 300 imported weanling calves many of which were suffering from pneumonia, the pathogens detected in carcasses and nasal swabs submitted from the outbreak included BoCo, Parainfluenza Virus 3 (PI3), Bovine Viral Diarrhoea Virus (BVDV), Mycoplasma bovis, Pasteurella spp., Salmonella Dublin and Histophilus spp. The 300 weanlings involved were calves that had been purchased into the farm from different sources. The two cases just outlined highlight the danger of mixing calves introduced from multiple sources.

Mucosal Disease

Dublin diagnosed mucosal disease in a six-month-old calf, submitted with a history of chronic diarrhoea. Post mortem examination revealed severe necrotising enteritis and typhlo-colitis, while histopathological examination of the intestine revealed dilated crypts lined by attenuated epithelium, and Peyer’s patches were depleted of lymphoid cells. PCR testing of tissues in this case was positive for BVDV. Kilkenny investigated the death of a yearling bullock with a history of scour and pneumonia. Ulceration and thickening of the entire small intestine was encountered while suppurative pneumonia was found in the right cranial lung lobe, and PCR testing of tissues in this case yielded a positive result for BVDV confirming the diagnosis.

Vena Caval Thrombosis

An in-calf heifer, which had been found dead, was submitted to Dublin for post mortem examination. Pulmonary infarction and an 8 cm diameter liver abscess which had ruptured into the caudal vena cava were noted and a large quantity of blood was found in the rumen. Septic emboli released into the vena cava from the ruptured abscess were evidently transported to the lungs resulting in the infarction while accumulation of blood in the rumen was consistent with swallowing of expectorated blood arising from the pulmonary lesion. Kilkenny examined a two-year-old bullock which was submitted for post mortem examination with a history of bleeding from the nose and mouth (epistaxis). Post mortem examination revealed pulmonary abscessation, hepatic abscessation (multiple) and the presence of a septic thrombus in the caudal vena cava.

Gastrointestinal disease

Athlone necropsied a four-month-old emaciated heifer and found a large amount of fodder wrap in an otherwise empty rumen, while evidence of coccidiosis and cryptosporidiosis was also found on laboratory testing. Ingestion of the fodder wrap was likely to have at least contributed to the weight loss problem and as other calves from the same group were also emaciated better management of waste plastic on the farm was advised. A two-month-old calf was submitted to Kilkenny with a history of having been found dead after drinking milk the previous day. Post mortem examination revealed distention of intestine while a twist was found at the root of the mesentery, confirming mesenteric torsion. Sligo necropsied a one-month-old calf with a history of chronic ill thrift and found severe abomasal ulceration. In a separate case, Sligo found perforating abomasal ulceration with resultant fibrinous peritonitis in a three-month-old calf. A one-month-old calf which had died after a short episode of mild depression was submitted to Kilkenny for post mortem examination which revealed perforating abomasal ulceration with associated fibrinous peritonitis.

Babesiosis

Cork confirmed Babesiosis on a number of occasions in October. In two separate cases where whole blood samples were submitted to the laboratory from cows showing clinical symptoms of the disease, detection of the protozoan parasite in red blood cells on examination of giemsa stained blood film was confirmatory (Figure 2). Post mortem examinations were also carried out on cattle that had died of babesiosis. Pathological change reported from these cases included jaundice and haemoglobinuria. Sligo diagnosed babesiosis in two cows submitted from separate farms for post mortem examination. One of these was a young springer which was found to be infested with ticks, and the second case was an aged cow.

Babesiosis  

Figure 2: Giemsa-stained blood film from a cow with babesiosis, with the protozoan parasite evident in red blood cells (arrow). Photo: Cosme Sanchez

Salmonellosis

Kilkenny necropsied a 13-day-old calf suspected of having pneumonia, and while evidence of pneumonia was found on post mortem examination, other changes such as haemorrhagic enteritis and mild jaundice were also identified. Salmonella Dublin was isolated from several organs, confirming salmonellosis. Dublin necropsied a four-week-old calf with a history of acute depression and recumbence ante mortem. Gross post mortem examination revealed pulmonary oedema, pleural effusion and diarrhoea. Multifocal splenitis, hepatitis and ulcerative colitis were found on histology. The farm had been experiencing an outbreak of Salmonella abortion at the time the calf died and though Salmonella spp. was not isolated from the calf, the antibiotic therapy administered in this case may have inhibited the growth of pathogens in bacterial culture. Herd history and characteristic pathological changes supported a presumptive diagnosis of Salmonellosis. From a separate herd, Kilkenny diagnosed salmonellosis in an 18-month-old heifer which had been found dead. Post mortem examination in this case revealed pulmonary congestion and meningeal oedema. The isolation of Salmonella Dublin from several organs confirmed the diagnosis. Dublin isolated Salmonella Dublin from a cow which had been suffering from diarrhoea. This cow had aborted one foetus in late gestation, two weeks prior to presenting with enteritis.

Other conditions

Two three-day-old suckler calves from the same herd that had been found dead in their pens were submitted to Limerick for post mortem examination. Both were found to have enteritis and to be dehydrated. E. coli K99 was detected in the intestines of both calves. Athlone examined a small, abnormally short-haired calf which died a few minutes after delivery and which was born one week before the due date. Gross post mortem examination revealed an enlarged irregularly nodular liver while histology revealed marked hepatic fibrosis. It was concluded that foetal death was caused by a congenital hepatopathy. Kilkenny examined a three-week-old calf which had required fluid therapy ante mortem but which bled incessantly from the catheter site. Post mortem examination revealed anaemia and widespread petechiation throughout the body. A tentative diagnosis of Bovine Neonatal Pancytopaenia (BNP) was made, pending confirmation. Pyelonephritis was diagnosed by Sligo in a three-week-old calf with a history of pining (ill-thrift, weight loss). Limerick necropsied a four-month-old calf with a history of diarrhoea and weakness for one week ante mortem and found large pale and hard kidneys (Figure 3); E. coli was isolated from liver and kidney. Histopathological examination revealed severe lesions of chronic multifocal to coalescing interstitial nephritis, which has been associated with E coli infection. Athlone diagnosed yew tree (Taxus baccata) poisoning in two one-year-old heifers which had been found dead. The characteristic yew tree leaves was found in the ruminal contents on post mortem examination. Cork investigated an outbreak of ulcerative teat lesions which had affected six heifers out of a milking herd of 70. Similar lesions were seen in the herd in previous years although fewer animals were affected in previous seasons. Serological testing of blood samples harvested from affected heifers revealed evidence of recent exposure to Bovine Herpes Virus 2, the causative agent of Bovine Ulcerative Mammilitis. Limerick investigated the death of a seven-year-old suckler cow in very fat condition which failed to rise within days of calving. The calf was delivered alive by caesarean section, but the cow died 48 hours after calving. Post mortem examination revealed a pale liver with a greasy texture on cut surfaces; fatty liver disease was confirmed on histopathology.

Chronic interstitial nephritis  

Figure 3: Enlarged, pale and firm kidney from four-month-old calf with chronic interstitial nephritis. Photo: Alan Johnson.

Abortions

Dublin isolated Salmonella Dublin from a seven-month-old Friesian foetus with serofibrinous pleuritis, two abortions had occurred in the herd. Athlone isolated Salmonella Dublin from the stomach contents of a five-month-old foetus, Bovine Viral Diarrhoea Virus (BVDV) was also detected in the pleural fluid from the same submission. In a separate case, Athlone isolated Salmonella Dublin from the abomasal contents of an eight-month-old foetus. Kilkenny reported a seasonal increase of abortions in October with Salmonella Dublin being the most common abortifacient encountered.

Hydrops foetalis (foetal anascara) was diagnosed in a foetus examined by Athlone. This abnormality is usually associated with hydroallantois or hydrops amnion. In most cases this condition is idiopathic and cases are usually sporadic. Kilkenny isolated Arcanobacterium pyogenes from a number of separate foetal submissions in October; this pathogen is normally a sporadic abortifacient.

Sheep

Pneumonia

Limerick examined two five-month-old lambs which had died following an acute episode of depression and pyrexia, which was unresponsive to antibiotic therapy. There had been four other similar mortalities from the group of origin which consisted of 62 lambs. Post mortem revealed pneumonia in both cases with fibrinous peritonitis and splenomegaly in one. Mannheima haemolytica was isolated from organs in the case of both lambs, confirming a diagnosis of mannheimosis. Sligo reported several cases of pneumonia in sheep in October, and Mannheima haemolytica was the most common pathogen isolated in such cases.

Parasitism

Sligo saw several mortalities in yearling and adult sheep associated with heavy acute infestations of Fasciola hepatica (liver fluke). Invariably, post mortem examinations revealed friable livers, often with rupture of the capsule and haemorrhage into the peritoneum (Figure 4). Cases histories often described sudden death after handling such as at dosing time. Athlone diagnosed acute fascioliosis in five different sheep from three separate flocks during October. Sligo saw several cases of parasitic gastroenteritis, usually affecting lambs.

Friable liver  

Figure 4: Friable liver with ruptured capsule from a sheep with liver fluke. Photo: Colm O Muireagain

Clostridial disease

Athlone investigated the sudden death of a six-month-old lamb, the fifth such mortality that had occurred in the same group of lambs in four days. The lambs were outdoors and had been fed a finisher meal for the previous three weeks. Post mortem examination revealed friable kidneys, pulmonary congestion, fibrin clotting in the pericardial sac and glycosuria. A diagnosis of pulpy kidney disease was made; high levels of grain feeding are a known risk factor for pulpy kidney in unvaccinated sheep. Sligo also reported several diagnoses of clostridial disease in lambs, with sudden death the common feature of the history in each case.

Other disease

Sligo isolated Corynebacterium pseudotuberculosis, from a pituitary abscess in a ram. The owner had noticed a rapidly progressing ‘dummy syndrome’ ante mortem. C. pseudotuberculosis causes Caseous lymphadenitis, a notifiable disease. It causes chronic caseous abscessation of lymph nodes. Typically the lesions are seen in superficial lymph nodes draining the area through which the organism entered the body (injection site, shearing injury), but many of these infections progress to become systemic, invading deeper sites, such as in this case.

Pigs

Three fattener pigs were submitted to Dublin with a history of coughing. Post mortem examination revealed fibrinous pericarditis and peritonitis in one of the three pigs. Both of the remaining two had pneumonia in the anteroventral lung with acute diffuse pleuritis in the case of one of these two. Influenza virus H1N1 was detected in lung tissue from the two pigs with pneumonia and while this was the only pathogen found, ante mortem antibiotic therapy may have inhibited bacterial culture growth. Histopathology revealed both bronchointerstitial and peribronchial “cuffing” pneumonia in the same lungs suggesting concurrent or sequential infection by more than one pathogen.

Avian

A five-week-old broiler chicken was submitted to Limerick for examination following the death of ten birds from a group of 65. The owner had noticed some diarrhoea in the group. The submitted broiler was found on necropsy to have lesions consistent with broiler ascites. The owner was advised to reduce the feed intake and ensure that the birds had a normal day-night light schedule. Colisepticaemia was diagnosed by Dublin in an eight-week-old turkey with fibrinous pericarditis, peritonitis and air sacculitis. The hepatic sinusoids contained clumps of gram negative bacteria.