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 threeweek 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”
Figure 2 “Lesions associated with trichomonosis in a Greenfinch- photo Michéal
Casey”