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September 2009 RVL Monthly Report

The Irish Meteorological Service (www.met.ie) reported that rainfall totals were above normal everywhere for the third successive summer, with about twice the average rainfall at some weather stations. Mean air temperatures for the summer months were a little higher than normal and sunshine totals were above normal everywhere. These warm and wet conditions were ideal for the survival of parasitic eggs and larvae. A liver fluke disease-forecasting model based on rainfall during summer and early autumn predicts that the risk of liver fluke infection during this autumn and winter is high in all areas including parts of the country not usually considered at risk such as the east and south east of Ireland. 

Cattle

Clostridium novyii and chauvoei were both identified in the inflamed and oedematous abomasum of a two-month old bucket reared calf examined by Sligo.  Kilkenny diagnosed blackleg in three animals, aged five, six and eleven months, all from one farm. The latter animal had not been on grass since purchase as a calf. Fluorescent antibody tests (FAT) were positive for Clostridium chauvoei. The animals came from a farm where ten animals had died in the previous few days. Losses had occurred in calves both housed and at grass. Clostridium chauvoei was identified in the neck and axilla muscles of a six-month old suckling weanling presented to Sligo.  Crepitus, oedema and a sweet smell were all observed.  A six-month old heifer, in good condition, which died suddenly, was presented to Athlone. Grossly, there was a focally extensive yellow swelling visible on the surface of the liver. There was a margin of congestion around this yellow lesion (which was devitalised liver tissue). Aerobic and anaerobic culture of the liver lesion did not yield any growth. Histologically, the lesion consisted of multiple foci of hepatocyte necrosis and haemorrhage with varying degrees of eosinophil infiltration (immature fluke migratory tracts). There was thrombosis of blood vessels and proliferation of large bacilli. The gross and histological lesions in the liver were considered consistent with a diagnosis of bacillary haemoglobinuria (BHU) or black disease (a clostridial superinfection following a significant migratory fluke insult). No evidence of haemoglobinuria was detected grossly when the urine was inspected or in the section of kidney tissue. However some deaths can be peracute. Treatment of other animals in this group for liver fluke, to include immature fluke was recommended as well as vaccination with a multivalent clostridial vaccine.

Kilkenny isolated Salmonella typhimurium from a yearling bullock with a history of dysentery for a week. Post mortem showed extensive liver fibrosis and calcification of bile ducts, the result of fluke infestation. The severity of the fluke damage was unusual for such a young animal. A three-year old cow, which was recumbent and in respiratory distress was submitted to Athlone. On gross examination fibrin tags were present on the diaphragmatic surface of the liver and the large intestine contained fluid contents. Urinalysis showed glucosuria and leukocytes in the urine, suggesting a urinary tract infection. Haematology showed marked neutrophilia. Urea, creatinine and fibrinogen levels were significantly above normal. Salmonella dublin was isolated on routine culture of urine and kidney. Limerick and Kilkenny also reported on cases of salmonellosis causing diarrhoea and fever in heifers and cows during the month.

Athlone investigated an outbreak of pneumonia in a group of pregnant Friesian heifers. The group had been housed for three weeks in August as a result of the wet weather. Within days of turnout many of the animals developed high temperatures and respiratory symptoms. One severely affected animal was euthanased and submitted for post-mortem examination. There were gross signs of tracheitis and a locally extensive pneumonia. Tests carried out on trachea and lung were positive for Bovine Herpesvirus type 1 (BHV1). Arcanobacter pyogenes was also isolated from the lungs. This is typical of IBR in that deaths from the disease usually arise from secondary pneumonia.  Reports from the farm indicated that all of the animals in the batch were affected. The herd was vaccinated with an intranasal IBR vaccine and there were no further deaths. However, 15 per cent of the group were reported to have aborted during the outbreak.

Yew tree poisoning was diagnosed by Dublin in one of two Friesian yearling bulls found dead at pasture. Numerous fronds of yew (Taxus baccata) were found in the rumen (figure 1). A yew tree was growing in the field where the bulls were grazing so the animals were moved from there as soon as the diagnosis was made. No further losses occurred.

yew tree foliage from rumen of bull

Figure 1: Yew tree foliage removed from the rumen of a yearling bull (Photo: William Byrne).

A two-year old heifer and a four-year old cow were submitted to Athlone from the same farm. Both had a history of respiratory distress, and hoose associated pneumonia was diagnosed in both animals following post-mortem examination. The history indicated that these animals had been treated for hoose on two occasions during the summer, the last dose being four weeks prior to the deaths.

A focally extensive purulent cardiac septal abscess was found in an adult cow presented to Sligo.  Nutmeg liver associated with heart failure was also a feature. Kilkenny examined a four-year old cow that had been treated for pneumonia. There had been an outbreak of pneumonia in these cows in the spring. Post-mortem examination showed about two gallons of cloudy yellow fluid in the pericardial sac and a thick layer of fibrin with a ¿bread and butter¿ appearance attached to the heart surface (figure 2). Arcanobacter pyogenes was isolated from the heart and from an abscess discovered in the liver in the region of the posterior vena cava. Kilkenny found a large (seven centimeter diameter) thrombus in the portal vein of a cow with a history of sudden death. The lungs, kidneys and spleen contained small abscesses from which Arcanobacter pyogenes was isolated. This condition has similar pathology to the more common thrombosis of the posterior vena cava.

"Bread and butter" exudate in a four-year-old cow with chronic pericarditis

Figure 2: "Bread and butter" exudate in a four-year-old cow with chronic pericarditis (Photo: Donal Toolan).

Sheep

Pasteurella pneumonia in association with significant gastrointestinal parasitism was diagnosed by Sligo in a number of lambs submitted from one farm. These lambs were recently purchased by an inexperienced farmer, and were in poor condition. Dublin examined a lamb, one of a group of forty that were not thriving.  Four of the group had died over a one-week period. The history stated that the lambs had been treated for fluke and worms, but large numbers of Trichuris ovis and strongyle eggs were detected in the faeces. Acute and chronic fascioliasis was diagnosed by all centres during the month.

A five-month old lamb was submitted to Athlone with a history of being found lying on one side and kicking. It could not stand and appeared to be gasping for air. There were no gross lesions on post mortem but histopathological examination of the midbrain (thalamus and colliculus) revealed multifocal areas of oedema and frequent acute perivascular "ring" haemorrhages.  The cerebrum exhibited oedema and neuronal loss in the grey matter of the dorsal portions of the section. The findings were consistent with a diagnosis of acute polioencephalomalcia (cerebro cortical necrosis). Risk factors for CCN in sheep include diets high in thiaminases or sulphates.

Poultry

Kilkenny diagnosed coccidiosis in a three-week old chicken with haemorrhagic contents in a dilated small intestine. Limerick diagnosed a similar condition in a young peacock submitted from a backyard flock of mixed birds.

Limerick diagnosed histomoniasis (blackhead) in a ten-week old turkey.

Other Species

Kilkenny examined a three month old foal that died after treatment for Rhodococcus equi pneumonia. It had extensive pericarditis with a thick layer of fibrin between the heart muscle and pericardium. Streptococcus bovis type 1 was isolated from the heart. Rhodococcus equi was isolated from a single one-centimeter diameter abscess on the serosal surface of the small intestine.

A mare in fat condition was presented to Athlone. The mare had been breathing heavily the previous evening and had died unexpectedly. Grossly, the lungs were congested and oedematous. The main finding was the presence of a distended large intestine, the contents being very watery and blood-tinged. On histopathological examination the intestine showed marked mucosal and submucosal oedema, with dilatation of lymphatics. There was also dilation and congestion of mucosal and submucosal venules and in some areas clostridia-like bacilli were seen in the mucosa. Based on these findings and other results (e.g. negative Salmonella culture) a diagnosis of Colitis X (equine intestinal clostridiosis) was made. Colitis X is now considered to be a dysbacteriosis due to overgrowth by colonic commensals, usually, Clostridium perfringens or Clostridium difficile. The dysbacteriosis can be instigated by prior antibiotic treatment, stress or a change in diet.

Sligo recovered an airgun pellet from a Cormorant (Phalacrocorax carbo) at the request of the Gardaí and the National Parks & Wildlife Service, who were investigating a suspected illegal shooting. The pellet had fractured the upper cervical spine at the level of C4. Radiology was used to locate the pellet (figure 3) which was then removed and returned to the Gardaí as evidence.

Radiograph of airgun pellet

Figure 3: Radiograph showing the location of an airgun pellet in the upper cervical region of a cormorant (Radiograph by Inishfree Veterinary Clinic, Sligo).