Current Findings in the Regional Veterinary Laboratories

September 2004

Some topics:-

Patent hoose in dairy cows.

Backleg in weanling suckler calves

Botulism

  • Yew tree poisoning
  • Parasitic gastroenteritis in lambs
  • Coughing and ill thrift in a sheep flock caused by lungworm - Muellerius capillaris
  • Absence of findings of acute fasciolosis in sheep.

Cattle

Kilkenny diagnosed several cases of parasitic gastroenteritis during September. Strongyle egg counts of up to 17,000 eggs per gram were seen in some cases. Some of these cases presented with a history of pneumonia, weight loss or nervous signs with or without scour. However, once an adequate anthelmintic programme was put in place, the losses and other problems disappeared. Histopathological examination carried out in Athlone showed evidence of Pasteurella pneumonia in a four-month-old calf. Four weanlings from three different farms were submitted to Kilkenny. Three had a history of just being found dead and the fourth had a history of respiratory distress. All cases had severe interstitial and sub-pleural emphysema. Bullae ranging from 1cm to 7cm in diameter were seen. Consolidated pneumonia was present in two of the four cases and lungworm were seen in the airways in all four. FAT for Respiratory Syncitial Virus (RSV) was positive in three of the four cases. The first case of hoose pneumonia diagnosed by Dublin this year was in a weanling in early September. Patent hoose was confirmed by Cork in dairy cows. The disease was in most of the first and second lactation cows, which were underweight. Comprehensive anthelmintic treatment of calves was the practice on the farm with boluses given in the summer and further treatment at housing. This may have left the animals with poor immunity to the lungworms. There was an excellent response to eprinomectin from the cows.

Sligo isolated Salmonella dublin from the liver and gall bladder of a four month-old calf that died of ruminal acidosis. This animal had ad lib access to concentrates. The main postmortem finding was greyish - yellow fluid rumenal contents with a pH of 5.4. The Salmonella isolate is likely to have been an incidental finding, reflecting this animal's carrier status. Salmonella dublin was isolated from faecal samples on two further occasions during the month. Limerick RVL encountered a small number of cases of blackleg in weanling suckler calves, where there was a history of inadequate vaccination. Cork also diagnosed that a stunted weanling with extensive skin lesions covering most of its body had a mast cell tumour. This is a very unusual neoplasia in cattle. The diagnosis was made from a biopsy and euthanasia was advised. xx

Neutrophilia and hypergammaglobulinemia were found in a bullock with enlarged carpal joints submitted to Dublin. This bullock became laterally recumbent and was euthanased. Multiple small abscesses throughout the entire spleen and to a lesser extent in the liver yielded Arcanobacter pyogenes on routine culture. A focus of infection, which was being disseminated via the bloodstream, was considered the most likely pathogenesis of these lesions. Athlone isolated Salmonella dublin from the faeces of a bullock with chronic weight loss and scour. Athlone also isolated the same organism from a cow with a high temperature and diarrhoea. Salmonellosis had been diagnosed on this farm five years previously. 7.2% of bloods examined for Salmonella in Athlone had significant titres. Investigation by Dublin of milk drop syndrome and pyrexia accompanied by some diarrhoea and ocular discharge in dairy cows in another dairy herd, also lead to the isolation of Salmonella dublin from a faeces sample from a cow that died subsequently. Samples submitted to Cork from a cow that died after an illness of five days duration in which haemoglobinurea and jaundice were clinical signs had findings suggestive of leptospirosis. L. icterohaemorrhagiae was detected on fluorescent antibody test and a liver necrosis consistent with that infection was apparent on histopathology.

Limerick RVL is investigating a suspected outbreak of bovine botulism. Three deaths have occurred in the group of yearling heifers over a three-month period. All deaths occurred on an area of land where poultry manure was spread in autumn 2003. There was also a poultry unit on an adjacent farm. All three animals presented with flaccid paralysis. There was no response to any treatment. The third case was submitted to the RVL for post-mortem examination. Congestion of the intestinal mucosal surfaces was the only significant finding. A sample of abomasal contents is being examined for evidence of Clostridium botulinum toxin. Cork confirmed that a cow losing condition for three months and with excess peritoneal fluid, mesenteric infiltrations and stricture of the bowel had intestinal adenocarcinoma. Yew tree poisoning was suspected as being the cause of death of six cows in county Tipperary, over a seven-day period. Samples of a plant taken from the rumen of one of the cows were sent for identification to the National Botanical gardens. They were identified as yew (Taxus baccata). Dead branches of yew tree, the result of recent hedge-cutting, were found in the field where the deaths occurred.

Sheep

Sligo diagnosed CCN by histopathological examination in a lamb from a flock where four lambs had been found dead in the previous month. Several clearly demarcated areas fluoresced strongly when a cross section of fresh cerebrum was examined under UV light (see figure 1). Mannheimia haemolytica (formerly Pasteurella haemolytica) septicaemia was diagnosed by Dublin as the cause of death in a well-grown lamb from a flock that had seven sudden deaths in the course of one week. There was a history of having been recently weaned. The lambs were not vaccinated. A seven-month-old lamb submitted to Limerick RVL for post-mortem examination following a history of scour, ill-thrift and anaemia was found to have parasitic gastro-enteritis. Large numbers of parasites were seen in the abomasum. Microscopic examination of some of the parasites showed large numbers of Haemonchus contortus and Teladorsagia (formerly Ostertagia) circumcincta larvae. Smaller numbers of Trichostrongylus axei larvae were also present. Haemonchus contortus is a blood-sucking parasite that, in large numbers, can cause anaemia. Parasitic gastroenteritis was the most common finding in lambs submitted for PME to Kilkenny. Lambs were submitted with histories varying from scour that failed to respond to treatment, pneumonia, suspect clostridial disease, and failing to thrive. Strongyle egg counts varied from 1,000 to 100,000 eggs per gram of faeces. Almost half of all routine ovine faecal samples submitted had strongyle egg counts in excess of 1,000 eggs per gram. A ewe submitted to Cork following euthanasia to investigate coughing and ill thrift in the flock was found to have nodules in the lungs caused by lungworm Muellerius capillaris. The coughing was ascribed to the lungworm infection while fasciolosis was contributing to the poor thrive. Sligo diagnosed spinal compression in a seven-year-old ewe with hind-leg ataxia. The lesion was neoplastic and locally metastaticand is currently being typed.Sligo reported that acute fasciolosis was not diagnosed at post mortem examination by the laboratory this autumn. The last case of fasciolosis (chronic) diagnosed was on 1st April 2004. The reason for this is not clear, but may be due to increased vigilance and awareness of control measures, including summer dosing programs. As an illustration of how low the incidence of fasciolosis has been in 2004 to date, there have been six diagnoses of louping ill in sheep and five of fasciolosis.

Deer

A six-month-old deer calf, referred to Cork with suspected parasitic pneumonia, had pyothorax with foul smelling fluid in the left hemithorax, with the left lung collapsed and consolidated while the right lung had multifocal abscesses (see figure 2). Pasteurella multocida and Arcanobacter pyogenes were isolated. There was no evidence of lungworm but histopathology, suggested foreign body material also as a significant factor in the lung damage.

Sligo reported a case of necrobacillosis in a fallow deer calf which was presented for necropsy examination. The dorsum linguae was totally necrotic and clearly prevented the calf suckling or foraging. Filamentous non-branching gram negative bacteria were identified on a gram stained smear. Follow up cultural examination succeeded in isolating Fusobacterium necrophorum. Necrobacillosis was confirmed on histopathological examination.

Birds

Kilkenny isolated Yersinia pseudotuberculosis from pheasants that showed severe enteritis on examination. Histological examination also identified focal areas of hepatic necrosis in a number of the livers from the pheasants. Sligo had an outbreak of 'Black-head' in young chickens on a free-range enterprise. Chickens are usually only rarely clinically affected by disease.

Figure 1 - CCN in a lamb – photo Micheal Casey

Figure 2 - Thorax of a six-month-old deer calf – photo Sorcha Spillane