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March 2009 RVL Monthly Report

Cattle

Limerick diagnosed septicaemic listeriosis in a one-week old calf.  The calf had been sick for three days and had a clinical history of diarrhoea and poor thrive. Post mortem examination of a nine-day-old Charolais calf submitted to Dublin revealed consolidation of left cranial lung lobes and a thick white exudate in the pelvis of the right kidney. There was milk present in the rumen (rumenal drinker) and the lining of the abomasum was dark. Meningeal vessels appeared prominent. Escherichia coli was isolated from the lung, meninges, spleen, liver and kidney. Colisepticaemia was diagnosed. The result of a zinc sulphate turbidity (ZST) test was low indicating insufficient absorption of colostrum antibodies. Lesions of meningitis and vasocentric suppurative encephalitis were present, and there was extensive fungal abomasitis. Fungal septicaemia was diagnosed in a two-week old calf submitted to Athlone. Gross post mortem examination showed necrotic enteritis and an associated peritonitis. There were ecchymoses on the parietal surface of the rumen, reticulum and omasum, and in the lungs. Histopathological examination revealed granulomatous pneumonia with fungal hyphae evident, thrombi with fungal hyphae in the intestinal wall and lesions of nephrosis.

Kilkenny investigated outbreaks of Salmonella dublin infection on two dairy farms. In the first case the farmer reported a mortality rate of up to fifty per cent in the calf group. A calf one-week old was submitted and was found to have lesions of fibrinous enteritis. S. dublin was isolated from liver, spleen, lung and intestine. In the second case, there was a dramatic reduction in milk yield accompanied by diarrhoea in cows one month after calving. Two cows died and two more responded to intensive antibiotic treatment. S. dublin was isolated from faeces samples submitted.

A two-week old calf with a history of scour was submitted to Athlone. There were lesions of diphtheritic laryngitis and aspiration bronchopneumonia in the cranial lung lobes. The contents of the intestines were fluid, and a necrotic intestinal intussusception with some fibrin tagging of the adjacent intestines was seen. Pseudomonas aeruginosa was isolated from the lung and rotavirus was detected in a sample of intestinal contents. The immediate cause of death was considered to be the strangulated intusussception, but the rotavirus infection was probably responsible for the diarrhoea. The calf had a second potentially lethal problem, as there was an abscessating bronchopneumonia secondary to the severe necrosuppurative laryngitis. Calf diphtheria (lingual necrobacillosis) was suspected by Kilkenny following gross examination of an emaciated five-week old calf with a history of diarrhoea, followed by weakness and death (figure 1). Fusobacterium necrophorum was not isolated.

Necrotic lesion in tongue of calf

Figure 1: Necrotic lesion in the tongue of an emaciated calf (photo: Donal Toolan).

Kilkenny carried out investigations on a farm where a few animals were permanently stunted and in poor condition. Two ten-day old calves and a yearling were submitted for post mortem examination. All had lesions of pneumonia. Pasteurella multocida was isolated from one calf and the yearling; one calf was positive for bovine coronavirus (BoCo) and the other had a low ZST reading(13 units) and was positive for rotavirus and cryptosporidium spp. in the faeces. Tissue levels of copper and selenium were satisfactory. This case illustrates the importance of properly controlling common diseases to ensure that subsequent growth and thrive are optimised.

Athlone diagnosed traumatic reticuloperitonitis and pericarditis in a five-year old cow. A ten centimetre long thin stiff black wire was present in the caudal mediastinum and there was in excess of 15 litres of fibrinoserous fluid in the thoracic cavity. A five-year-old cow presented to Dublin had a history of recumbency for five days before death. The animal had gone down one day after calving but had risen for a few hours after treatment with intravenous calcium, before once again becoming recumbent despite further treatment. Post mortem examination revealed fibrinous pericarditis, and while the mammary gland did not seem grossly abnormal, brown watery fluid containing clots could be extracted from one of the quarters. Histopathology revealed severe congestion of the meninges, multifocal necrosis in the liver and suppurative mastitis. A pure growth of Escherichia coli was isolated from the abnormal milk sample and coliform mastitis with associated endotoxaemia was diagnosed. The cause of the hernia was probably traumatic. Limerick examined of an eight year-old cow that died within a few hours of calving. It was found to have a rupture of the fundus of the uterus, adjacent to the pelvic brim.

Sheep

Four aborted lambs and foetal membranes were presented to Athlone from one flock. The foetal membranes were thickened and reddened in the intercotyledonary area. A coat swab from one lamb and a swab of the foetal membranes from another, tested positive for Chlamydia. Histolopathology revealed lesions of suppurative placentitis, with vasculitis and Chlamydia-like inclusions within trophoblast epithelial cells. A diagnosis of enzootic abortion of ewes (EAE) was made. Antibodies to Toxoplasma gondii were detected by Dublin in serum from aborted twin lamb foetuses submitted from a farm where ten ewes from a flock of 420 had aborted. Multifocal lesions of mineralisation were observed in the relatively autolysed placenta, and congestion in the white matter of the cerebrum and a small focal area of gliosis was observed histologically.

Listeria monocytogenes was isolated from the brain of a three-month old lamb submitted to Kilkenny with a history of head-tilt, circling and eventual recumbency. Two three-year old ewes, which were found in a recumbent state and frothing from the mouth, died within twelve hours despite treatment with calcium and magnesium. They were examined by Kilkenny, where listeriosis was diagnosed based on lesions seen histologically in both brains. One of the ewes also had suspect lesions of clostridial enterotoxaemia, involving a section of the small intestine. A fluorescent antibody test (FAT) was positive for Clostridium sordellii.

Athlone diagnosed copper toxicity in two ewes with a clinical history of inappetance and depression. Gross post mortem examination showed that both carcasses were jaundiced and had enlarged and dark kidneys, with red urine in the bladder of one. Very high levels of copper were found in the livers of both ewes confirming copper toxicity as the cause. On subsequent enquiry it emerged that the sheep were being fed a cattle ration, which typically contains a higher amount of copper than is recommended for sheep.

Poultry

Six live laying hens were submitted to Athlone from a flock of 18,000 layers. There was a history of a drop in egg production over the previous 3-4 days. There was no evidence of neurological signs or enteritis on clinical examination. On gross post mortem examination the birds all exhibited excessive fat deposition in the mesentry (around intestines) and around the gizzard and heart. The livers were a brown to pale tan colour. There was no gross evidence of enteritis, or respiratory pathology. All six birds were actively ovulating and four of the birds had good sized, soft-shelled eggs in the uterus. Sections of liver from two of the birds exhibited moderate to marked micro- and macro-vesicular vacuolation of the hepatocytes, which given the gross findings was considered consistent with hepatic lipidosis (fatty liver). The laying down of excessive fat can lower productivity in laying hens and lead in severe cases to mortalities due to fatty liver haemorrhage syndrome. This can be due to the diet being primarily too high in energy or can occur due to the diet being deficient in calcium (laying hens will increase their dry matter intake of calcium deficient diets in an attempt to ingest adequate calcium). An obesity/fatty liver syndrome in laying hens has also been associated with aflatoxicosis. Advice was given to investigate the laying hen diet (feed and any supplements), concentrating on total energy and calcium content in the first instance.

Other Species

A mute swan (Cygnus olor) with a history of listlessness was euthanased and submitted to Dublin for examination. It was one of three from the same public park that was being treated, and poisoning was suspected. On post mortem examination two fishing hooks were lodged in the bird¿s oesophagus, one of which had also penetrated the trachea (figure 2). Exudate and food material had accumulated around the hooks, and the crop and gizzard contained almost no food.

Fishing hooks in oesophagus of mute swan

Figure 2: Fishing hooks in the oesophagus of a mute swan (photo: Rosemarie Slowey).