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April 2011 RVL Monthly Report

Bovine

The submission rate of young calves to the laboratory service in April was high.  The types of diseases encountered in such cases were manifold and varied. 

Sligo reported several submissions of neonatal calves, and among the more common diagnoses reported were hypogammaglobulinaemia, navel ill, joint ill, diarrhoea and septicaemia. Sligo diagnosed hydrocephalus in a four-week-old calf with a history of blindness.  The condition may be caused by exposure to teratogens during pregnancy, one of which is Bovine Viral Diarrhoea Virus (BVDV) though the virus was not detected in tests on this particular calf. Dublin detected an intussusception of the small intestine in a two-day-old calf (Figure 1) with a history of unwillingness to suck. In a separate case Dublin diagnosed atresia ilei in a 30-hour-old Belgian Blue calf, in which depression was the main clinical presentation. A segment of the ileum was found to be totally absent and each of the two free ends of intestine formed a blind ended sac, the intestine proximal to the lesion was distended with ingesta while distally the intestine was shrunken and empty. Limerick examined a four-day-old suckler calf which was found dead.  Thyroid gland enlargement and thyroid follicular hyperplasia were found on histology, consistent with goitre, and bacteriology revealed the calf to have colisepticaemia, while a low ZST result in this case was indicative of poor passive transfer of maternal antibody. Cork necropsied a one-week-old nipple-fed calf which was one of seven mortalities in a group of thirty and found cranioventral consolidation of lungs consistent with bronchopneumonia. Pasteurella multocida was isolated from several tissues and a diagnosis of Pasteurella pneumonia and septicaemia was made.  Athlone also diagnosed Pasteurella multocida septicaemia in a four-week-old calf with a history of sudden death, again the main post mortem finding in this case was a bronchopneumonia, while Pasteurella multocida was isolated from several tissues. Limerick necropsied a three-week-old calf with a history of high temperature and respiratory distress ante mortem; a cardiomegaly associated with a ventricular septal defect was found. Kilkenny necropsied  a two-week-old calf which was found to have a large blood clot in the small intestine (Figure 2) and haemorrhages in other organs. Thrombocytopaenia was demonstrated in an ante mortem blood sample and, with trilineage hypoplasia in the bone marrow, was consistent with Bovine Neonatal Pancytopaenia (BNP).  Athlone diagnosed Salmonella septicaemia in a five-day-old calf which was weak since birth, splenomegaly and jaundice were encountered on post mortem examination and Salmonella Dublin was isolated from tissues.  Athlone necropsied a three-week-old calf with a history of failure to stand after calving. There was fibrinosuppurative polyarthritis and there was rancid milk in the rumen.  Histological examination of tissues revealed severe chronic active rumenitis, with the fungal and bacterial involvement. A diagnosis of chronic mycotic rumenitis was made, this condition can develop after prolonged antibiotic therapy, but it can also arise in ruminal drinkers where either there is either a failure of closure of oesophageal groove, or inappropriate tubing has allowed milk to collect in the rumen. Kilkenny isolated Salmonella Dublin from each of a pair of one-month-old calves from the same premises, one of the two had pneumonia and fibrinous colitis, and the second had meningitis.

Intussuseption  

Figure 1: Small intestinal intussusception in a two day old calf. Photo: William Byrne

Blood clot in intestine  

Figure 2: Large blood clot in the intestine of a two week old calf with Bovine Neonatal Pancytopaenia (also known as BNP or ‘bleeding calf syndrome’). Photo: Donal Toolan

Athlone necropsied a two-month-old calf which was found dead. The carcass was dehydrated while the intestinal contents were watery. Histological changes found in the intestinal lining and the finding of large numbers of coccidial oocysts confirmed a diagnosis of severe coccidiosis. Non-infectious causes of mortality in older calves included a case of lead poisoning, which Limerick diagnosed in a three-month-old Belgian Blue calf which was submitted for necropsy, with a clinical history of severe distress, bawling and kicking ante mortem. Biochemistry revealed very high levels of lead in tissues. The source of the lead was not confirmed and no other animals were similarly affected. Athlone diagnosed copper poisoning after necropsy of a number of carcasses submitted from an incidence of multiple mortalities in a group of forty calves which were approximately six weeks of age. Copper sulphate had been administered orally to the calves, and the first mortalities occurred four hours after dosing. The case highlights the dangers of oral supplementation of copper. Kilkenny diagnosed a very unusual case of cellulitis in the neck of a two-month-old calf as a result of a perforated abomasal ulcer. On necropsy of the calf it was found that the ulcerated abomasal wall had adhered to the abdominal wall and ingesta had tracked through the fascia between the muscle layers of the abdominal and thoracic walls to accumulate under the skin along the neck.

The laboratory service also investigated the deaths of several older yearling and adult bovines. Sligo diagnosed Blackleg in a yearling, while Dublin identified nephritis and multi-organ haemorrhages in a one-year-old heifer. Bacteraemia was suspected,although a bacterial pathogen was not isolated possibly due to the administration of antibiotics to the heifer ante mortem. Kilkenny diagnosed traumatic pericarditis in a 15-month-old bull. The pericardial sac contained brown fluid and a large quantity of fibrin, and a wire 8 cm in length was found in the reticulum which had penetrated through the reticular wall, the diaphragm, and the pericardial sac. Athlone also diagnosed a traumatic pericarditis in a cow which had been pining for three weeks prior to its death. Post mortem examination revealed severe purulent pericarditis with a 5 cm wire free in the pericardium. Athlone diagnosed endocarditis in a yearling heifer with a history of lameness and stiffness, a vegetative lesion was found on the bicuspid valve, and a suppurative embolic pneumonia was also identified. Streptococcus dysgalactiae subspecies equisimilis was isolated from the cardiac lesion. Limerick examined a three-year-old Limousin-cross cow with a history of not eating or drinking, the tongue was described as constantly hanging out of the mouth,  histological examination of the brain revealed a suppurative encephalitis consistent with listeriosis. A two-year-old bovine that had grown to only half of its expected size was submitted to Kilkenny. Dry pleural adhesions and large areas of pulmonary atelactesis were suggestive of a previous episode of pneumonia, and testing of tissues proved positive for BVDV. Athlone also detected BVDV in tissues of a two-year-old bullock, which had been found recumbent antemortem. Gastrointestinal ulceration was evident on post mortem, and persistent infection with BVDV was diagnosed. Kilkenny investigated the sudden death of a three-year-old bull. Necropsy revealed abomasal ulceration and haemorrhagic intestinal contents,  and death from haemorrhagic shock due to abomasal ulceration was diagnosed. Sligo diagnosed cirrhosis of the liver due to ragwort poisoning in an aged cow. Several cows from the same herd had succumbed to the same condition the previous year. 

Bovine abortion   

Abortions on separate holdings associated with Bacillus licheniformis and Salmonella Dublin were recorded by Athlone. Alhough Bacillus licheniformis abortion is normally sporadic, outbreaks can occur and are associated with mouldy hay or silage during gestation. Kilkenny isolated Streptococcus uberis from a 7.5 month old aborted foetus in which fibrinous peritonitis was also observed. Dublin isolated Bacillus licheniformis from the abomasal contents of two calves from the same herd, which died around parturition. Other similar deaths had occurred in this herd, but had not been investigated. In light of a history of death peripartum Bacillus licheniformis infection in utero was likely in this case. 

Ovine

April saw a seasonal increase in the number of lamb submissions to the laboratory service. Sligo diagnosed clostridial disease in several neonatal lambs with a history of sudden death, while Athlone diagnosed Pulpy Kidney Disease in a one-month-old lamb with a history of sudden death, serous clotting of the pericardial sac and abnormally friable kidneys were the main post mortem findings. Kilkenny investigated the sudden death of a one-month-old lamb and found a 180 degree mesenteric torsion on gross post mortem examination. Athlone diagnosed Nematodirus battus infection in two separate submissions of lambs from different flocks. In both cases intestinal contents were copious and watery and the presence of Nematodirus battus eggs in faeces was confirmed. Dublin found abomasal ulceration in a six-week-old lamb (Figure 3), a hair-ball (“trichobezoar”) was also found in the abomasom, and the lamb had black watery faecal contents and mucous membranes were very pale. Athlone isolated Mannheima haemolytica from the lungs of an eight-week-old lamb with severe pneumonia and, in a separate case, Athlone isolated Pasteurella multocida from the brain of a four-week-old lamb with meningoencephalitis.  

Abomasal ulceration  

Figure 3: Abomasal ulceration (arrow) in a six-week-old lamb.

A number of ewes from separate flocks were presented to Sligo with a clinical history of neurological symptoms; Listerial encephalitis and louping ill were the most common diagnoses in such cases. Dublin diagnosed hypomagnesaemic tetany in a six-year-old ewe which was found dead approximately four weeks after lambing. Very low levels of magnesium were found in vitreous humour; hypomagnesmic tetany is most common in ewes between one to four weeks after lambing. Athlone identified florid fibrinous pericarditis in a ewe which was found dead, Arcanobacterium pyogenes was isolated from the lesion, while in a separate case where a ewe was found dead, Athlone detected lesions in the brain consistent with listerial encephalitis.

Ovine Abortion

Limerick isolated Listeria monocytogenes from aborted twin ovine foetuses, while Dublin necropsied foetal and placental tissues submitted from an outbreak of abortion and found diffuse placentitis with multifocal necrosis. Clearview Chlamydia testing of tissues yielded a positive result while elementary bodies were visible on placental modified Ziehl-Nielsen (MZN) impression smears, and a diagnosis of Chlamydophila (enzootic) abortion was reported.

Porcine

Two finisher and four grower pigs were submitted to Dublin from a unit with a history of sudden deaths among the finishers while the growers displayed neurological symptoms ante mortem. Post mortem examination of finishers revealed a fibrinous pleuropneumonia. Actinobacillus pleuropneumonia was isolated from tissues in these two cases, and Streptococcus suis was isolated from the brain as well as other organs in the case of the growers.

Four piglets were submitted to Athlone from a farm experiencing a lameness problem. Post mortem examination of the piglets revealed separation of the mural and solar hoof horn affecting one digit in each of two of the four piglets. Three piglets were affected by polyserositis and the fourth piglet was found to have fibrinosuppurative meningitis. In the case of the latter pig with meningitis, E coli was isolated from several organs, including the brain, while in the case of two of the remaining three pigs, Erysipelothrix rhusiopathiae was isolated from body tissues, a finding consistent with erysipelas.

Equine

Athlone necropsied a yearling horse in poor condition.  An abscess in the jugular groove and an abscess adjacent to the trachea were found on post mortem while histology of the lung showed non-suppurative interstitial pneumonia. Streptococcus equi equi was isolated from affected tissues and a diagnosis of strangles was made. 

Equine abortion

Athlone examined an aborted equine foetus which was five weeks before term, post mortem examination revealed abundant serosanguinous fluid in body cavities while pneumonia was also found. Equine Herpesvirus 1 was detected in tissue, a common equine abortifacient.