Current Findings in the Regional Veterinary Laboratories
December 2007
Cattle
All laboratories reported a steady throughput of aborted foetal material during the month. Salmonella Dublin, Listeria monocytogenes, Arcanobacter pyogenes, Bacillus licheniformis, Leptospira hardjo, Neospora caninum and Bovine Viral Diarrhoea (BVD) virus were amongst the most common causes of abortion identified. As in 2006, Brucella abortus was not isolated from any foetus during the year (1,648 samples were cultured). It is important, however, to continue to encourage farmers to submit foetal material to the laboratories for diagnostic purposes.
An outbreak of respiratory disease in weanlings was investigated by Sligo. Respiratory Syncytial Virus (RSV) was detected on lung tissue taken from one carcass. Part of the herd had been vaccinated for Infectious Bovine Rhinotracheitis (IBR). Two six-month old calves presented to Athlone were also diagnosed with RSV pneumonia. Pasteurella multocida was isolated but was considered to be a secondary pathogen. A weanling submitted to Athlone with a short history of severe respiratory distress had lesions of fibrinonecrotic tracheobronchitis, bronchopneumonia and emphysematous bullae. IBR virus was identified. Anteroventral lung lobe consolidation, pulmonary and cardiac abscessation, ulceration of the abomasal mucosa, oesophagus and interdigital spaces were amongst the gross lesions observed by Dublin in a persistently infected (PI) BVD positive yearling.
Athlone carried out a field investigation on a spring-calving dairy herd where thirty percent of cows were not pregnant. The visit was carried out in early December at which time the average body condition score of the cows was found to be satisfactory. A metabolic profile was carried out on blood samples taken from a percentage of the cows and the copper and selenium status was found to be low. Copper supplementation was recommended and the owner was advised to ensure that this continued during the breeding season. It was also advised to institute a regime of selenium supplementation in the herd to ensure adequate dietary selenium throughout the year. There was no evidence of dietary protein or energy imbalance. However advice was given regarding the pre- and post-calving feeding of cows to ensure minimal loss of body condition post-calving.
Sheep
Sligo reported that a farmer who presented four aborted foetuses for post mortem examination was himself very visibly suffering from severe conjunctivitis. All four foetuses tested positive for Chlamydophila abortus, and the farmer was advised, through his veterinary surgeon, to contact his general practitioner (GP) about his eye infection, and to advise the GP that he had been in contact with C. abortus. Athlone diagnosed toxoplasmosis in a flock where seven of fifty ewes had aborted.
Athlone and Sligo warned about the danger of fluke-associated deaths this winter. Both laboratories reported on cases of acute and chronic fascioliasis (figure 1). In most cases there appeared to be inappropriate control measures in place. The recently issued Department of Agriculture, Fisheries and Food liver fluke forecast suggests that the current risk of disease is very high and that treatments in January and April should be strongly considered for out-wintered sheep. All bought-in sheep should be kept isolated and dosed with an anthelmintic and flukicide before being allowed to join the main flock.
An adult ram, which had been housed for the winter with a group of rams, was found dead and was submitted to Dublin. The ram had a raised, ulcerated cutaneous mass on its poll, composed of firm white tissue and a deep tract of pus, which appeared to have eroded the underlying cranium bone leading to a suppurative meningitis. Arcanobacterium pyogenes was isolated from the lesion. Chronic cellulitis over the poll is a common sequel to fighting in rams.
Psoroptes ovis mites were identified in wool samples submitted to Kilkenny from ewes with a history of severe scratching. It was reported that the ewes had been treated twice with an ivermectin product, but no details of dosage rates and dosage interval had been supplied.
Limerick examined amputated ear sections of ewes from a dairy sheep farm. The ear tips had to be amputated from a number of sheep with proliferative lesions that were thought to be neoplastic. This was the second year that the problem had occurred. Histopathological examination, however, showed that the lesions were associated with contagious pustular dermatitis (orf).
Pigs
Two three-month old fattener pigs, which died suddenly on a farm with a history of other sudden deaths, were presented to Dublin. Gross findings in each pig were quite different. In one pig the left lung was severely congested and consolidated, with part of the right similarly affected. Histopathology revealed lesions of interstitial pneumonia, and Streptococcus suis type 2 was isolated from the lung and spleen. In the case of the second pig, lesions were mainly associated with the intestine where there was significant haemorrhage into the lumen of the ileum and jejunum. No significant bacterial pathogens were isolated, but histopathological examination revealed widespread thrombosis of intestinal blood vessels. The changes were consistent with diffuse intravascular coagulation, possibly associated with endotoxic or septic shock. Streptococcus suis type 2 septicaemia could not therefore be ruled out in both cases. Limerick also isolated Streptococcus suis type 2 from a group of three-week old piglets. The history given was of sudden deaths. Lesions included polyserositis, meningitis and arthritis. Streptococcus dysgalactiae was isolated from the joints of a piglet of similar age, with lesions of polyarthritis.
Poultry
Kilkenny diagnosed joint infections associated with Erysipelas rhusiopathiae and Mannheimia haemolytica in turkeys dying suddenly within three or four weeks of reaching slaughter weight. In Athlone a turkey with a history of sudden death had lesions of fibrinous pneumonia and air sacculitis. Routine culture of lung lead to the isolation of Klebsiella pneumoniae and Erysipelothrix rhusiopathiae. Klebsiella spp. is occasionally associated with mortality in young turkeys. Erysipelas is associated with acute septicaemia and high mortality in unvaccinated flocks. Advice was given regarding vaccination and treatment with an effective broad-spectrum antibiotic.
Other Species
A blood sample from a dairy goat suffering from emaciation proved positive for Johnes Disease using an enzyme-linked immunosorbent assay (ELISA) test. This was the sixth animal to show similar clinical signs on the farm over a two-year period. A farm investigation was conducted by Athlone, and advice was given regarding the implementation of measures to reduce the risk of spread of the Mycobacterium avium subspecies paratuberculosis (MAP) organism during the kidding period.
Two Ring-tailed Lemurs (Lemur catta) that died after a one-week illness were examined by Cork. Similar histological lesions were found in both animals, with multifocal diffuse hepatocellular necrosis and moderate non-suppurative inflammatory cell infiltration. Non-suppurative myocarditis was also a feature, and parasitic cysts were seen in the myocardium of one of the lemurs. Immunohistochemical (IHC) staining was positive for Toxoplasma antigen.
Sligo reported that trichomonosis caused the deaths of two Greenfinches (Carduelis chloris) found in a rural county Sligo garden. This disease (also called trichomoniasis) has recently been observed in garden birds in the U.K.,especially in Greenfinches, and the first cases in Ireland have appeared in the east and south of Ireland in the past couple of months. Affected birds often appear lethargic and "fluffed up", and seem to die quite quickly after showing the first clinical signs (figure 2). Trichomonosis is transmitted by contact with the saliva of infected birds, and shared feeding areas, especially bird feeders have been implicated in disease transmission. Although the Trichomonas organism that causes this disease is not considered to have a zoonotic risk, garden birds may carry a range of other organisms (including Salmonella) that may cause illness in humans. Feeding areas and utensils should be kept clean.
Limerick examined a 12-week old Rottweiler with a history of vomiting and diarrhoea. Lesions of necrotic enteritis were seen, which on histopathology were consistent with parvovirus infection, complicated by secondary bacterial invasion. The dog also had granulomatous lesions in the lungs that were thought to be as a result of parasitic (possibly Toxocara canis) larval migration. The dog had been vaccinated for parvovirus a month before becoming ill. Kilkenny and Athlone also diagnosed parvoviral enteritis in young pups during the month.
CAPTIONS FOR PHOTOS
Figure 1 “Lesions of chronic fascioliasis in a ewe’s liver – photo Michéal Casey”