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August 2011 RVL Monthly Report

Cattle

Neurological Disease

Diseases of the nervous system were seen frequently in August. Dublin diagnosed lead poisoning at necropsy of a seven-month-old calf which had been found dead a couple of days after transfer to new pasture. The diagnosis was confirmed by lead assay of a sample of renal cortex. Limerick diagnosed lead poisoning in a three-year-old Friesian cow, the second from a group to have died within a period of one week. Blindness and bruxism (teeth grinding) were described ante mortem and post mortem examination revealed small metal fragments in the reticulum. A sample of this material was subsequently found to have a high lead content and toxic levels of lead were again detected in a sample of renal cortex. Dublin examined a six-month- old calf which had been recumbent and paddling prior to death. Gross post mortem revealed apple green fluorescence of cut section of brain on exposure to UV light, and histology of the brain confirmed cerebro-cortical necrosis (CCN). Kilkenny also confirmed CCN using histology in the case of a five-month-old calf with a history of nervous signs; two other calves from the same group were also affected with similar clinical signs. Cork necropsied a five-day-old calf which while able to suckle was inco-ordinated and unable to stand from birth. Post mortem examination revealed hypoplasia of the cerebral cortex and cerebellum, but the remainder of the brain appeared normal. Teratogenesis by Bovine Viral Diarrhoea Virus (BVDV) was suspected, and further testing is currently in progress. A seven-year-old cow which had been submitted to Athlone as a suspect BSE case was found to have abscessation of the cerebellum on post mortem examination. Athlone also examined a six-year-old cow which was similarly suspected of having BSE. Post mortem histopathological examination showed no evidence of spongiform change, but revealed a glial cell tumour in the mid brain. Dublin examined a three-year-old bull with a history of clinical signs suggestive of listeriosis (such as unilateral facial paralysis and circling), and histological examination of the brain revealed multifocal suppurative encephalitis consistent with Listeria monocytogenes infection.

Respiratory disease

Pneumonia cases seen in August included two five-month-old calves submitted to Kilkenny for post mortem examination with a history of ill thrift. Three other calves from the same group had also died with similar clinical signs. Parasitic pneumonia (hoose) was confirmed in both cases. Furthermore Pasteurella sp. was isolated from lungs of both calves, while faecal egg count for both calves revealed evidence of parasitic gastroenteritis. Dublin also reported parasitic pneumonia in a 30-month-old heifer with a history of respiratory distress for a number of days ante mortem. Other cattle from the same group were also affected. Post mortem examination revealed severe bullous septal emphysema numerous adult worms in the larger airways. Although more commonly diagnosed in younger cattle, parasitic pneumonia is also reported in immunologically-naive older cattle which have had limited challenge by infective Dictyocaulus larvae at pasture, whether because of management or intensive anthelmintic use. Kilkenny examined a five-month-old bovine with that had been found dead, from a herd where two other calves from the same group had died in similar circumstances. Pulmonary consolidation of 70% of both lungs was the main gross finding while the isolation of Mannheima haemolytica from tissues confirmed Mannheimosis. Dublin examined a pregnant heifer which had had a history of respiratory distress and grunting. The group of cattle in question had recently been moved to newly rented land of uncertain history and age cohorts of the heifer were similarly affected. Gross post mortem examination revealed severe diffuse pulmonary emphysema dissecting into the mediastinum, and histology revealed emphysematous interstitial pneumonia, and a diagnosis of atypical interstitial pneumonia (Fog Fever) was indicated.

Clostridial disease

Athlone reported a number of cases of bovine clostridial disease in August. Post mortem examinations of two three-year-old cows from unrelated herds revealed oedematous abomasitis with haemorrhagic intestinal contents. Clostridium sordelli was isolated from the affected tissues in both cases. Similar post mortem findings were encountered by Athlone in the case of a two-month-old calf which was submitted to the laboratory, having being found dead. Again Clostridium sordelli was isolated from the affected tissues. Athlone also diagnosed clostridial myositis (blackleg )in three calves from different herds. Failure to vaccinate against clostridial disease continues to cause significant losses in Irish cattle, largely because the risk of the disease is perceived by farmers to be low in cattle, compared to sheep where vaccination is a routine procedure.

Abortion

Dublin isolated Salmonella Dublin from a number of foetal submissions from separate herds. In one case a foetus and placenta were submitted from a herd which had suffered 14 abortions, and where some of the affected dams were reported to be dull and pyrexic. Salmonella Dublin was isolated from both foetal abomasal contents and placenta in this case. Athlone isolated Salmonella Dublin from the abomasal contents of a foetus submitted from a herd which was experiencing an outbreak of diarrhoea among adult cows. Kilkenny reported isolating Salmonella Dublin from the abomasal contents of five foetuses, two of which were from the same herd, while each of the remaining three originated from different herds. All were approximately seven months into gestation when aborted and all were decomposed and emphysematous. In a separate case Kilkenny isolated Arcanobacterium pyogenes from foetal abomasal contents, an agent which is normally associated with sporadic abortion in cattle.

Other Salmonellosis

Cork isolated Salmonella Dublin from several organs in two three-month-old calves submitted from a herd which had had significant losses in calves due to ill thrift and scour. Histology on tissues from both calves revealed paratyphoid nodules in the liver characteristic of salmonellosis  and therefore supportive of the diagnosis. Athlone investigated the sudden death of a six-month-old calf and found brown watery foul smelling gastrointestinal contents on post mortem examination, while Salmonella Dublin was isolated from its organs.

Other conditions

Other interesting cases submitted to the laboratory included a four-month-old calf submitted to Kilkenny with a history of progressive abdominal distension prior to death. Post mortem examination revealed that the peritoneal cavity was filled with urine (uroperitoneum) associated with rupture of the urinary bladder. A small abscess was detected in the wall of the bladder, and this had ruptured. The abscess is most likely to have arisen as a sequel to a neonatal umbilical infection, probably ascending via the urachus. Kilkenny also examined a six-month-old calf with a history of ruminal atony. Post mortem examination revealed a severe purulent peritonitis, and the remnants of the vestigial urachus contained a number of abscesses, one of which had ruptured. Again this abscessation was likely to have arisen from a neonatal umbilical infection. One three-month-old calf with a history of periodic respiratory distress over a two-week period was submitted to Athlone for examination. Gross post mortem examination revealed a septic embolus lodged within an aneurysm at the base of the aorta. This aortic lesion had given rise to a fistulating tract connecting the oesophagus and aorta allowing haemorrhage into the gastro-intestinal tract. This was evidenced by the presence of many very large thrombi in the reticulum and rumen, while the abomasum and small intestine contained black digested blood. Athlone also examined an eighteen-month-old heifer with a clinical history of weakness and being unable to stand prior to death. Post mortem examination revealed an anaemic carcass, due to a haemorrhaging abomasal ulcer (Figure 1). Limerick investigated the death of an 18-month-old Hereford-cross heifer with a history of poor thrive and intermittent diarrhoea. Post mortem examination of the animal found it to be stunted with evidence of chronic pneumonia, and BVDV was detected in tissues.

Abomasal ulcer  

Figure 1: Abomasal ulcer in an 18-month-old heifer. Photo: John Fagan

Sheep

Ill-thrift in lambs

Dublin necropsied two four-month-old lambs which were part of a group suffering from ill thrift on pasture. Arising from post mortem examinations, cobalt deficiency was identified in both lambs while in one of the them, both parasitic gastroenteritis and suppurative encephalitis consistent with listeriosis were also reported. The practitioner was advised to recommend cobalt supplementation and worm dosing.

Infectious disease

Kilkenny reported a five-month-old lamb with a history of pining, and which had haemorrhagic intestinal contents at necropsy. Clostridium sordelli was detected at the site of the lesion using FAT, and clostridial typhlitis/colitis was diagnosed. Athlone diagnosed mannheimosis in a five-month-old lamb which was found to have a large pulmonary abscess and pleural adhesions on gross post mortem examination; Mannheima haemolytica was isolated from the affected tissues on culture.

Athlone examined a five-month-old lamb with a history of paralysis of both right fore and hind limbs and found a severe cellulitis extending from the mid-cervical region along the right flank and extending caudally to the right hind leg. The inflammatory response was found to be particularly severe around two injection sites near the right shoulder. E. coli was isolated from the lesion and the injection sites were suspected of being the portal of entry of infection.

Copper poisoning

Athlone also diagnosed copper poisoning in a five-month-old lamb with a history of acute depression and jaundice, whose kidneys were dark in appearance, and whose liver was friable. The detection of toxic levels of copper in liver and kidney tissue confirmed the diagnosis, and the herdowner was advised to cease supplementary feeding until the source of copper could be identified.

Pigs

Dublin isolated Salmonella Typhimurium from various tissues and the intestinal contents from eight seven-week-old weaner pigs that had died suddenly after moving from the first-stage to the second-stage weaner house of a pig unit. The feed had been changed from dry ration to a liquid-based feed at the same time. Diarrhoea had been observed in some of the pigs ante mortem.

Horses

Athlone necropsied a one-month-old foal which had died suddenly, and whose large intestinal contents were watery and foul smelling. Salmonella Typhimurium was isolated from these contents. Limerick isolated Streptococcus equi subspecies equi from the discharging submandibular abscess of a nine-year-old thoroughbred mare (equine strangles).

Domestic Poultry

Respiratory disease

Limerick necropsied a three-month-old Silkie chicken with a history of sneezing and nasal discharge ante mortem. PCR testing of tissues yielded a positive result for Mycoplasma gallisepticum. Limerick reported that it saw several cases of Mycoplasma gallisepticum infection affecting backyard flocks in recent months. Athlone investigated an outbreak of respiratory disease in a backyard flock where there was a high morbidity and low mortality, the main clinical sign was gurgling breath sounds particularly when the birds were agitated. Post mortem examination of three birds submitted from the flock revealed pericarditis and pus along pharynx and trachea. Serological screening of blood samples taken from affected birds revealed evidence of exposure to Mycoplasma gallisepticum. In a separate case, Dublin examined a hen which experienced respiratory distress ante mortem, there were other mortalities in the flock with similar clinical histories, Infectious bronchitis virus was detected by PCR testing.

Coccidiosis

Cork diagnosed coccidiosis in a 20-week-old hen from a backyard flock comprised of six, where the affected bird had severe diffuse necrotising hepatitis and splenitis, and coccidial cysts were found in the liver.

Failure of herbal ‘wormer’

Dublin examined two fancy hens from a backyard flock which were found to be in poor body condition on post mortem examination. The history provided indicated that a herbal wormer had been administered to the birds. However a parasitic enteritis was diagnosed on the basis of a high faecal egg count and detection of nematodes on histological examination of the intestine. The immediate administration of anthelmintic treatment using drugs of proven efficacy was advised. Many backyard poultry owners favour these herbal products for worm control, which have no egg withdrawal periods, as they contain no anthelmintics.

Marek’s Disease

Gross post mortem examination of a chicken submitted to Athlone with a history of torticollis revealed thickening of the sciatic nerve. Histology of this nerve revealed a lymphocytic neuritis, while a non-suppurative encephalitis was also found. These pathological changes were consistent with Marek’s disease.

Pheasants

Dublin examined three eight-week-old captive-reared pheasants which belonged to a group of 100 that had been moved to an outdoor run during the previous two weeks. The majority had become lethargic and died, and a post mortem examination of three of them revealed poor body condition, Syngamus trachea (gapeworm) infestation of their tracheas (Figure 2) and dark caecal contents were also found, and coccidial oocysts were identified in faeces. Gapeworm infestation and concurrent coccidiosis were diagnosed. In an separate case, Dublin necropsied two 10-week-old pheasants where the group of origin had a very similar clinical history to the case just described, and again gapeworm infection with concurrent coccidiosis was diagnosed. Athlone investigated the death of two pheasants with a history of lethargy and found thickening of the caecal walls and yellow watery caecal contents. Faecal analysis revealed a high coccidial oocyst count, and histology findings were also supportive of coccidiosis.

Syngamus trachea  

Figure 2: Eight-week-old pheasant with adult Syngamus trachea (arrow) worm infestation along the trachea. Photo: William Byrne

Wild birds

Dublin dealt with two incidences of wild bird poisoning in August. In one case a peregrine falcon and a pigeon were submitted when found in a woodland together. Alphachloralose was detected in the crop of the falcon and also in tissues from the pigeon, and the use of the pigeon as a poison bait for the falcon was considered likely. In a separate case, Dublin examined a buzzard which was found dead, and again alphacloralose was detected in tissues.