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November 2009 RVL Monthly Report

Cattle

Sligo diagnosed lung worm infestation in a number of weanlings presented for post mortem.  The carcasses tended to be in poor body condition and ill thrift was evident for some time.  Concurrent fascioliasis resulting in diffuse hepatitis was evident in some of these cases.  Similar findings were also seen in adult ewes.  Pleural and pericardial transudation was seen in one such case as a result of hypoproteinaemia.

Dublin diagnosed Neospora caninum associated abortion in a dairy herd in which six cows had aborted at 3 to 4 months gestation. Multifocal accumulations of glial cells were seen in the cerebral tissues antibodies to Neospora caninum were detected in maternal serum samples. Dublin also detected Salmonella dublin as the cause of bovine abortion in another herd.

Limerick diagnosed septicaemic salmonellosis in two weanling from two separate farms during the month. In one case the animal had diarrhoea over a ten-day period. In the other case, the animal had been dyspnoeic and weak for only a few hours before death. This animal also had a heavy liver fluke infestation.

Nephropathy of unknown aetiology was diagnosed in two month old calf presented to Sligo.  The calf was anaemic, uraemic, dehydrated and in poor condition, along with multifocal haemorrhaging abomasal ulcers.

Dublin diagnosed bronchopneumonia in a six-month-old weanling, with 75% of the lungs partially or fully consolidated. Pasteurella multocida was isolated from the lungs. The calf also had a faecal egg count of 500 strongyle eggs per gram.

Sligo detected BVD virus associated with Mucosal Disease at post mortem in four store animals which had not been thriving for some time.  Linear oesophageal ulcers, rumenal pillar ulcers, watery diarrohea and necrotic typhilitis and segmental colitis were seen to varying degrees in the cases examined. 

A cow from a herd where three cows had died suddenly was submitted to Dublin.   All three had been dried off in the previous week, given dry cow therapy and had been transferred to "wintering ground".  This coincided with prolonged periods of rainfall.  Fibrinosuppurative necrotising mastitis with thrombosis was subsequently found on histopathology. Streptococcus dysgalactiae was isolated from mammary tissue and also isolated from several organs throughout the body.  Streptococcus dysgalactiae is categorised as an "environmental" Streptococcal species because it can be found in the cows' environment from where it can gain entry to the mammary gland via the teat canal. 

Limerick diagnosed blackleg as the cause of sudden death in an unvaccinated eight-month old weanling. Suspect lesions were seen in the heart, tongue and diaphragm. A fluorescent antibody test was positive for Clostridium chauvoei.

A number of full term calves were presented to Sligo during the month.  The calves were fully formed but the lungs of most were not inflated.   These findings are suggestive of dystocia and or prolonged calving.  If the calves survived such dystocia could lead to acidosis.  Acidosis is known to reduce the absorption of colostral antibodies, in turn leading to hypogammaglobulinaemia

A massive haemorrhage into the abdominal cavity emanating from the uterus was found by Sligo in a seven year old dairy cow which had died suddenly.   An extensive fibrinous peritonitis with multiple adhesions was found in nine year old cow submitted to Sligo.  The adhesions had led to constrictions of the bowel which had blocked the passage of faeces.  Limerick diagnosed yew tree poisoning in a 3-year old Simmental cow. It had been found dead along with another cow and a bull. There had been some stormy weather in the previous days. Leaves and branches from a yew tree were found in the rumen.

In November 667 milk samples were submitted to the RVLs.  Staphylococcus aureus was the predominant isolate, accounting for 55% of cultures (figure 1).  Given the time of year it is likely these samples were submitted from cows with elevated somatic cell counts with a view to informing dry cow therapy selection.   If as suspected these samples were from cows with elevated SCC the coliform and Bacillus isolates were likely to be contaminants. 

Percentage of mastitis pathogens cultured from milk samples submitted to the RVLs in November 2009 (xls 16Kb) 

Figure 1: Percentage of mastitis pathogens cultured from milk samples submitted to the RVLs in November 2009.

Sheep

Sligo diagnosed acidosis in a 6 month old well conditioned ram.  Large numbers of Clostridia spp were detected suggesting a Clostridial involvement as well ('Overeating Disease').

All the regional veterinary laboratories have reported substantial increases in the diagnoses of acute and chronic fascioliasis in a number of sheep submitted during the month.  Possible explanations for this unprecedented increase in the level of fascioliasis include the heavy rainfall over two consecutive summers and the mild winter last year which resulted in expansion of snail habitats and prolonged survival of infective metacercariae on pasture.  Typical findings at post mortem included decreased body condition, anaemia, and both acute and chronic diffuse hepatitis.  Pleural and pericardial transudation as a result of hypoproteinaemia were also seen in a number of cases. 

Goats

A goat from a herd of 300 was submitted to Limerick with a history of depression, sub-normal temperature and diarrhoea. Post-mortem examination revealed lesions in the liver consistent with chronic fascioliasis.

Dublin diagnosed bronchopneumonia in a female goat that died from a group with respiratory signs over a 10 day period. Well demarcated dark red consolidation of the lungs with serofibrinous pleuritis was evident, from which  Mannheimia haemolytica was cultured. 

Equine

Kilkenny found a grossly enlarged spleen in a 19 year old horse (Figure 2 ).  This can found to be due to lymphoma on histopathology.  Rapid severe weight loss, exercise intolerance and lethargy were features of the history.  Interestingly the white blood cell count was normal ante mortem.

Enlarged spleen in a horse

Figure 2: Enlarged spleen in a 19 year old horse (photo: Donal Toolan).

Avian

Dublin examined 7 laying hens from an organic flock experiencing high mortality. Six of the seven had egg peritonitis, and Escherichia coli was isolated from the faeces, liver and other organs of all 7 birds.

Increased prevalence of paramphistomosis

Increases in the prevalence of acute larval paramphistomosis have been detected by the various veterinary laboratories in both sheep and cattle.  Paramphistomes (or rumen flukes) are usually considered to be of little pathogenic significance when present in their adult form in the forestomachs. However, heavy infestation with larvae, which parasitise the small intestine, can cause a severe protein-losing enteropathy and high mortality.

Paramphistome larva attached to duodenal mucosa

Figure 3: Paramphistome larva attached to the mucosa of the duodenum (photo: Donal Sammin).

Paramphistomes have an indirect life cycle similar to that of Fasciola hepatica but with different snail species as intermediate hosts. Consequently, the same risk factors would appear to apply as for fasciolosis. It has been suggested that the recent increase in prevalence of rumen fluke infestation is due to flooding - that snails normally resident in permanent water bodies move onto flooded pasture, and are shedding metacercariae there, which become available for grazing animals when the floods recede.

Affected animals have presented to the Veterinary Laboratory Service with profuse watery diarrhoea, prostration and death. Death may intervene very soon after first signs of diarrhoea in sheep such that the disease in affected flocks may initially present as 'sudden death' whereas in cattle the course would appear to be more protracted with recent severe weight loss as a characteristic feature in clinically-affected animals. The morbidity in affected groups of cattle also appears to be lower than that in sheep flocks and the disease only appears to be manifest in younger cattle whereas all ages of sheep appear to be susceptible. There can be significant mortality in sheep flocks - about 30% encountered in two affected flocks. Antemortem confirmation of diagnosis is problematic; faecal sampling is unlikely to be of diagnostic value because the infestation is prepatent; marked hypoproteinaemia seems to be a consistent feature of the disease and may provide supporting evidence.

Flukicides licensed for the treatment of fasciolosis may not be effective against paramphistomes. Oxyclozanide is reported to be effective against adult paramphistomes and has recently been used to good effect to treat an affected sheep flock (with the larval form of the disease) in the midlands. Other flukicides such as rafoxanide have been reported to be effective against paramphistomes but usually at dosages 2-3 times that recommended for treatment of fasciolosis. If considering departing from recommended dosage rates you must consult with the manufacturer of the product in question regarding safety margins, efficacy, withholding periods etc. Information on licenced flukicides (by product name and active substance) can be obtained at the Irish Medicines Board website:

http://www.imb.ie/EN/Medicines/VeterinaryMedicines/VeterinaryMedicinesListing.aspx