Download April 2007

Current Findings in the Regional Veterinary Laboratories
April 2007
Cattle
A diagnosis of neonatal colibacillosis was made by Dublin in a two-day old calf with
a history of lethargy. The intestine appeared dilated and contained pale yellow watery
fluid. Other than congestion of the brain no other gross lesions were seen.
Enterotoxigenic Escherichia coli (K99 positive) was detected in intestinal contents.
Two one-week old calves from different herds were submitted to Dublin with similar
histories of diarrhoea that was non-responsive to treatment. One herd had lost three
calves over one weekend, after failure to respond to the oral electrolyte and antibiotic
treatment that had achieved good results earlier in the calving season. In both cases a
heavy burden of Cryptosporidium spp. was detected in the faeces. In addition, the
zinc sulphate turbidity (ZST) test results of 11 and 13 units were low when compared
to the minimum recommended level of 20, indicating poor absorption of colostrum
antibodies.
Kilkenny examined a ten-day old calf that had shown signs of pneumonia followed by
incoordination and death within a few days. Salmonella dublin was isolated on routine
organ culture. Histopathology showed multifocal liver necrosis, interstitial
pneumonia and meningitis consistent with Salmonella dublin septicaemia. It is
interesting to note that the bacterium was isolated from internal organs but not from
faeces, as often happens in septicaemia. Athlone also diagnosed septicaemic
salmonellosis in a one-week old calf with a history of sudden death.
Cork examined a three-week old calf that had a persistent scour and had been on
prolonged antibiotic therapy. Post mortem examination revealed a severe abomasitis
and rumenitis. The abomasal mucosa was dark, necrotic and covered by digested
blood. Routine and fungal cultures were negative, and a fluorescent antibody test
(FAT) for Clostridium sordelli was also negative. However, microscopic
examination of sections of the abomasum showed widespread hyphal invasion,
thrombosis within the blood vessels and necrosis of mucosa and submucosa
consistent with mycotic abomasitis (figure 1). Salmonella dublin and
cryptosporidiosis were subsequently found in some of the other calves in the herd. A
one-month old calf examined by Athlone had a navel infection and diffuse purulent
pneumonia. An enzyme-linked immunosorbent assay (ELISA) test was positive for
Bovine Viral Diarrhoea (BVD) viral antigen. Athlone also diagnosed BVD in a twoweek old calf, which had gross lesions of diffuse peritonitis, omphalitis and enteritis.
A two-month old calf was presented to Athlone with a history of severe lethargy with
poor response to treatment. No significant lesions were identified on gross post
mortem examination, but histopathological examination of the brain revealed nonsuppurative encephalitis involving the cerebrum and cerebellum, consistent with a
diagnosis of listeriosis.
Blood samples were submitted to Cork from yearlings on a farm that reported
problems with weak calves, pneumonia, scour, ill-thrift, poor response to antibiotic
treatment, and high mortality rates. The problems had been going on since the spring
of 2006. All nine samples were positive for the presence of bovine viral diarrhoea
(BVD) viral antigen. A fifteen-month old store bullock with a history of hind limb
weakness and nystagmus was presented at Kilkenny. Histopathological examination
of the brain and heart showed multifocal necrosis due to thrombotic vasculitis.
Colonies of gram-negative cocco-bacilli were seen in blood vessels of the heart. The
findings were consistent with a diagnosis of thromboembolic
meningoencephalitis (TME). Haemophilus somnus was not isolated in this case.
Faecal samples examined by Cork from four cows in one herd with persistent
diarrhoea and slight drop in milk yield, were positive for liver fluke eggs.
Tick borne fever was diagnosed by Cork in two dairy herds with a history of
pyrexia and milk drop. Anaplasma (formerly Ehrlichia) phagocytophila infestation
was identified from the inclusions seen in the neutrophils of blood smears (figure 2).
This rickettsial organism, transmitted by the tick Ixodes ricinus, typically produces a
short febrile illness associated with leucopaenia. Recovery is usually uneventful but
animals can remain carriers for many months.
Lead poisoning was diagnosed by Limerick in a dairy herd. The cows presented
with the sub-acute form of toxicity viz. agalactia, dullness, anorexia, blindness, gait
abnormalities, alimentary tract malfunction, and nervous manifestations which
eventually lead to death. All three cows that died were found dead in ditches. Metallic
lead was found in the reticulum of the cow that was submitted for post mortem and
kidney analysis showed toxic levels of lead. Gross lesions included non-specific
petechiation, inflammation of the gastro-intestinal tract and enlargement of the liver.
The herd owner carried out a search and found that a tractor battery that had been
inadvertently left in a paddock showed evidence of recent disturbance.
Hypocalcaemia and hypomagnesaemia were detected by Cork in blood samples from
a dairy herd where ringwomb appeared to be causing delayed calvings and dystocia.
Sheep
Kilkenny diagnosed emphysematous abomasitis in a one-month old lamb. A
fluorescent antibody test was positive for Clostridium sordelli. Coccidiosis was
diagnosed by Sligo in lambs at pasture presenting with enteritis from two separate
flocks.
A pregnant ewe carrying twins was examined by Cork and was found to have a
severe cellulitis with oedema and haemorrhage extending from the sternum to the
inguinal area. Arcanobacter pyogenes was isolated. The sudden death of a three-year
old ewe submitted to Athlone was attributed to torsion of the mesentery. A ewe was
presented to Sligo from a flock where up to five ewes presented with neurological
signs. The ewes had been grazed on rough pasture. Ticks were detected in the axillas
of the dead ewe and on the four comrades examined. Brain histopathology revealed
perivascular lymphocytic infiltration, and glial nodule formation in the hind
brain and mid brain. Lymphocytic infiltration of blood vessels and glial shrubbing
was evident in the cerebellum. These findings are consistent with louping ill.
Pigs
Pasteurella multocida was isolated by Cork from two pigs, seven weeks old, from
two different farms.
Kilkenny examined three six-week old pigs with a history of scour and wasting. All
three were emaciated and two had lesions of necrotic enteritis. Salmonella
typhimurium was isolated from all three. Virology tests are ongoing.
Poultry
Staphylococcus aureus was isolated from the lungs of a batch of three-week old
chickens submitted to Limerick. Up to 1,000 deaths had occurred from a group of
50,000 birds. Most of the birds were found dead and had displayed few clinical
symptoms.
Fowl cholera (Pasteurella multocida isolated) was identified by Cork in a hobby
flock. The principal manifestations were of a very poor hatch, with many dead-inshells. Most of those that did hatch were weak and died within days. Chronic sinusitis
in hens was also a feature of the outbreak.
Other Species
The abortion of a foal foetus received by Cork was associated with Equine
Herpes Virus type 1, based on the histopathological findings and a positive
polymerase chain reaction (PCR) test.
A six-week old goat kid, one of twins, with a history of diarrhoea and loss of appetite,
and in the case of this one bloat following feeding with a stomach tube and sudden
death was presented to Dublin. Peritonitis apparently arising from a perforated
abomasum was found to be the likely cause of death with large numbers of
coccidial sporozoites and gametogony stages were seen during histopathological
examination in the small intestine. (Photo available if required of coccidia).
Limerick diagnosed acute pancreatic necrosis in a greyhound. The animal had a
clinical history of depression, vomiting and diarrhoea. Other than blood tinged fluid in
the peritoneal cavity, the gross lesions were unremarkable. Histopathology of the
pancreas showed severe interstitial haemorrhage extending into the surrounding fat.
There was breakdown of pancreatic lobules with separation of acinar cells.
A captive buzzard (Buteo buteo) was presented to Athlone with a history of a short
illness. Histopathology revealed that death was associated with granulomatous
pneumonia and hepatitis, more than likely of bacterial origin. .
CAPTIONS FOR PHOTOS
Figure 1
“Mycotic hyphae in the abomasal submucosa of a three-week old calf – photo Cosme
Sánchez-Miguel”
Figure 2
“An inclusion in the neutrophil of an adult cow associated with tick-borne fever–
photo Cosme Sánchez-Miguel”