|
Return to Animal
Health Centre Home Page
Diagnostic Diary - August 1996
TOLL FREE NUMBER: Please note that the Animal Health Centre
now has a toll free number: 1 800 661-9903. Keep this in mind if
calling the lab long distance.
Return to Table of
Contents
From The Assistant Chief Veterinarian
R. J. Lewis
There have been several exciting developments occurring at the
Animal Health Centre over the last few months and I would like to
share two of them with you.
Quality assurance and quality control are major issues of
concern with diagnostic laboratories everywhere and no less so at
the AHC. The American Association of Veterinary Laboratory
Diagnosticians (AAVLD) has addressed this topic and developed a
certification process for veterinary diagnostic laboratories.
They provide two types of accreditation: accredited and
provisionally accredited. The first of these is given to a
laboratory that is "...capable of providing a full range
of diagnostic services including necropsy, histopathology,
clinical pathology, bacteriology, virology, mycology,
parasitology, serology, and chemistry/toxicology." The
second type is given to a laboratory that does not meet the
criteria but that intends to do so within a given time frame. The
standards established are very high and require a great deal of
information regarding the philosophy of the service, personnel
qualifications, physical facility, budget, and a wide variety of
other very specific parameters. We have amassed a large package
of information which has been forwarded to the Accreditation
Committee for evaluation at their next meeting in July. If the
application is accepted, an on-site review committee will arrange
a time to visit the AHC over several days to evaluate our
services.
We believe we have excellent people and provide a very high
quality service. Rigorous evaluation by the AAVLD will put this
belief to the test. If we are successful in achieving full
accreditation, our clientele may be reassured that our services
have met a very high standard. Following our evaluation and
subsequent results, their report will be shared with you in a
future edition of this newsletter.
No matter what you read or listen to these days, the Internet
and the World Wide Web have been receiving extensive media
coverage. The B.C. Ministry of Agriculture, Fisheries, and Food
have had a home page on the Web for several months and are
presently redesigning the graphics and information provided at
this site (http://www.gov.bc.ca/agf/). We have been
developing a link to this home page and plan to be on line within
the next month.
This format will present an ideal opportunity to get
information to you and to update it rapidly. The Diagnostic Diary
will be on line as well as a blank submission template,
instructions on shipping specimens to the AHC, a current fee
schedule, a staff directory, photos of the various laboratory
sections, and an overview of all the tests available within each
section. There will also be an alphabetical listing of all the
tests we provide, a bulletin board of current events and
important recent diagnoses, a list of all federally and
provincially reportable diseases, and links to other Web sites.
If you are anxious to see the AHC on line, call up the BCMAFF at
the middle or end of July and there will be a link to the AHC.
Undoubtedly there will be many updates and improvements to the
site as we hear from you and find out what you would like to see
at this location.
We now have a generic Electronic Mail address that may be used
to access the Animal Health Centre via the Internet. This will be
monitored on a semi-regular basis for incoming and outgoing mail.
If you should have any questions that we may be able to address
for you, please contact us via the following address:
ahc@agf.gov.bc.ca
I will be monitoring this regularly but if you require
information immediately, please continue to use the telephone or
FAX.
We look forward to hearing from you through this new
electronic communication format. Your ideas and comments are
always welcome.
Return to Table of
Contents
A Message from the Chief Veterinarian
Dr. Peter Hewitt
We are always looking for ways to improve our service. What
Dr. Ron Lewis has outlined above will, we hope, provide useful
information to you, our clients.
 Ron or I are
always pleased to hear from anyone with suggestions on how we
could better provide service to you. If you don't tell us, we
won't know. At one time we had a small committee consisting of
members of the BCVMA who met with us on a regular basis to
discuss lab services. This was very useful to us, and perhaps
this approach could be tried again. Would you support this?
Please let me know.
On the topic of animal welfare, I have been involved in
numerous meetings and have answered many letters, which seems to
be taking more and more of my time. While most people are
supportive of the amendments to the Prevention of Cruelty to
Animals Act, some individuals think the amendments fall
short, while others think they go too far.
Briefly, the amendments permit the Society for the Prevention
of Cruelty to Animals (SPCA) to enter any premises generally open
to the public where animals are for sale, hire, or exhibition. In
this way, the SPCA will hopefully be able to monitor and prevent
abuse before it escalates. "An ounce of prevention is worth
a ton of cure!" Prior to the amendment, SPCA staff had to
wait until the abuse occurred before they could take action.
As well, there is a provision within the act to allow the SPCA
inspector to enter any premises, including a vehicle, aircraft,
or vessel (not a dwelling house without a warrant) where an
animal is believed to be in "critical distress".
"Critical distress" occurs when veterinary treatment
cannot prolong an animal's life, or where prolonging an animal's
life would result in unduly suffering. "Critical
distress" also includes those situations where immediate
veterinary intervention is necessary to prevent the imminent
death of an animal (i.e., a dog shut in a completely closed car
on a hot summer's day).
An offence provision is now included in the Act which removes
the need to prove "willful" cruelty as was previously
necessary under the Criminal Code.
The Act states the offence section does not apply if the
distress results from an activity which is carried on in
accordance with reasonable and generally accepted practices of
animal management (for farmed animals, the "Recommended
Codes of Practice" for that species is used by the SPCA as
those standards).
What is the role or responsibility of the practicing
veterinarian who is presented with an animal which has been
mistreated? Should he or she report that owner to the SPCA? I
believe there is an obligation to do so, unless the practitioner
thinks the owner intends to accept the advice given and will not
repeat the abuse. The issue falls under the jurisdiction of one's
own personal judgment. What do you think?
Return to Table of
Contents
Neospora Update from the Animal Health Centre
John Coates
Neospora sp protozoan abortion continues to be the
number one cause of identified infectious abortion in dairy
cattle submissions at the AHC in Abbotsford. To date, numbers of
diagnosed beef cases remain low.
Investigative work of both a pathological and epidemiological
nature continues by the Neospora Committee established within the
Fraser Valley and spearheaded by Drs. Rich Vanderwal of the
Abbotsford Veterinary Clinic, John Robinson of the AHC, and
Chairman Mr. Ron Barker of the Abbotsford Agricultural Centre.
Any one of these persons should be contacted for additional
information on this subject.
Most notably in California, as well as in our studies here,
specific facts are slowly being brought to light on this
intriguing cause of infectious abortion in cattle. A condensed
review of some of these facts follows, which may help to answer
many of the questions received by staff at the AHC from time to
time from owners and practitioners alike.
- There is no known treatment or prevention for the
infection.
- The life cycle of the parasite is unknown.
- Brain tissue, together with other organs including heart
and liver, is crucial for a diagnosis. Immunperoxidase
testing at the AHC confirms cases initially diagnosed by
standard light microscopy. At present, the Indirect
Fluorescent Antibody Technique (IFAT) is used to detect
circulating antibodies to the agent in either cows or
colostrum-deficient neonatal calves. An ELISA test to
detect antibodies against the agent will become standard
practice at the AHC by September, 1996.
- It is not yet known if the canine isolate (Neospora
caninum) and the bovine isolate represent identical
species.
- The only known natural route by which cattle become
infected with Neospora sp. is transplacental
infection of the fetus from the infected dam.
- The similarities of Neospora (an apicomplexa
coccidial parasite) to Toxoplasma suggests that
postnatal infection may be acquired through oral
ingestion of coccidial oocysts shed from an unidentified
carnivorous definitive host.
- Serology done on a few coyotes and an occasional dog
taken from Fraser Valley farms with Neospora
abortion problems have had negative titres to the agent,
using the indirect Fluorescent antibody test (IFAT).
- There is good evidence of congenital transmission of
neosporosis from one generation to the next, producing
persistently infected calves that may proceed to abort
when they become pregnant.
- Whether Neospora can cause significant abortion
problems in the first trimester is not yet well known;
most Neospora abortions occur from 4 to 6 months
gestation.
- In British Columbia and elsewhere, the vast majority of
abortion confirmations are in dairy cattle. Breed
susceptibility is not thought to be a major factor here,
but rather the environment of the drylot dairy is more
conducive to the spread and transmission of the disease.
Cattle in drylot dairies are densely populated and fed a
variety of harvested feeds stored in and around the dairy
prior to feeding. These feeding practices may offer
opportunities for fecal contamination of ration
components.
- Cows that abort a Neospora infected fetus can have
additional infected fetuses in subsequent pregnancies.
This observation is reported in the literature and has
been seen in Fraser Valley herds as well. The outcome of
these subsequent pregnancies is variable, resulting in a
congenitally infected calf or possibly another abortion.
- There is no known method whereby an infected cow can be
cleared of the infection.
- There are no known methods to prevent (postnatal)
infection with Neospora sp in cattle because there
is insufficient information on the parasite's life cycle
on which to base recommendations. Nevertheless, it is
prudent to remove all potentially infected aborted fetal
tissues, including the placenta, that may serve as a
source of the organism for other animals. Fecal
contamination of water and feed by other animals should
be minimized.
- As is the case with the related coccidial organism, Toxoplasma
(an important cause of abortion in sheep and goats)
development of an effective vaccine against Neospora
will be difficult.
(Primary reference: Anderson M et al, Calif. Vet Diag Lab and
Dept Pathology, Micob & Immun, School of Vet Med; Univ of
Calif., Davis, Calif., neosporosis and abortion in dairy cattle,
in Advances in Dairy Technology 1996: 8; 197-209.
Return to Table of
Contents
Fly Larvae in English Sparrows
Dr. Victoria A. Bowes
A concerned member of the public submitted three juvenile
English sparrows for necropsy. She had noticed that these young
fledglings had several maggots infecting the skin of their heads
and that these birds and the previous nestmates displayed
weakness, progressing to death over a few days. Several large,
plump, tan maggots were present in cavitations under the skin of
the head and neck of each bird. The nests were also submitted and
yielded approximately 20 fly pupae.
The size and shape of the maggots were suggestive of Sarcophaga
sp., the flesh fly, which was confirmed by identifying the flies
which hatched from the pupae following eight days of incubation. Sarcophaga
sp. flies are usually associated with carrion or decomposing
organic matter, but some species require living flesh to complete
their life cycle. Preventative measures are in place which
involve pulling down the affected nests.
Return to Table of
Contents
Practical Advice
by Marjorie Ramsay
...sic transit gloria mundi
never use the coin wash on a Sunday.
Return to Table of
Contents
Pasteurellosis in ducklings
Dr. Victoria A. Bowes
The recent owners of a small commercial duck farm noticed a
persistent and slowly increasing mortality rate in their young
ducklings. Before their deaths, the ducklings displayed lack of
coordination, tremors, and hyperexcitability. At necropsy, there
was marked fibrinous pericarditis (inflammation of the heart sac)
and the hock joints contained purulent exudate. Microscopically,
there was a severe acute meningitis. A bacterium resembling Pasteurella
anatipestifer was recovered from the brain and visceral
organs. Results of the antibiotic sensitivity testing indicated
this organism should respond to treatment with penicillin.
Return to Table of
Contents
Gas gangrene and death in a horse following
injection
D.M. McIntosh
A seven year-old horse died from gas gangrene after receiving
an intramuscular injection. The horse had been injected three
days previously with an "anti-allergic medication" for
an apparent reaction to fly spray. Over the next two days the
horse became severely lame, and would not bear weight on the
affected limb.
A veterinarian examined the horse, diagnosed bacterial
cellulitis, and instituted extensive emergency treatment, but the
horse died because of the advanced state of the disease. Deep
wounds, including injection sites, are most suitable for the
development of gas gangrene. In this case, the injection of the
medication into the hind limb was most likely the initiating
factor. Care must be taken when injecting any medication.
Return to Table of
Contents
Thinking positively
"I learned this, at least, by my experiment; that if one
advances confidently in the direction of his dreams, and
endeavors to live the life which he has imagined, he will meet
with a success unexpected in common hours."
- Henry Thoreau in Walden; or, Life
in the Woods, published 1854.
Return to Table of
Contents
Sharp Cuts from the Necropsy Room
Malignant lung tumor in a horse
A 20 year-old Arab horse was submitted to the AHC for
necropsy, following a prolonged period of progressive debility. A
malignant lung tumor, consistent with bronchiolo-alveolar
carcinoma, was found distributed throughout much of its lung
tissue.
Return to Table of
Contents
Goitre in a neonatal foal
Tissues were received from a 10 day-old foal that had
been weak at birth, and which had failed to nurse on its own. The
animal was bottle fed and had received a transfusion of blood
from its dam in an attempt to save it. The foal eventually died.
Coliforms were cultured from lung, liver, and thoracic fluids;
there was microscopic evidence of a bacterial septicemia. The
most interesting finding, however, was marked hyperplasia of the
thyroid tissue, indicative of goitre. Iodine deficiency in equine
fetuses can be as much a problem as in other species, and several
cases of goitrous foals have been observed this past spring.
Prudent trace mineral supplementation to the pregnant mare is
needed to avoid newborn foals that are stillborn, weak, or fail
to prosper.
Return to Table of
Contents
Lymphoma in a mare
An older mare was submitted for necropsy after showing
signs of chronic wasting and intermittent diarrhea.
Clinical-pathological tests results suggested kidney disease.
Gross necropsy findings revealed an advanced malignant tumor
within the posterior abdomen and pelvic inlet, which had
completely encapsulated both kidneys and ureters. There was mild
distention of the pelvis (hydronephrosis) of the right kidney,
and both ureters were partially occluded by the firm,
proliferative malignancy. The mass had also infiltrated the
mesentery supporting the intestine.
Microscopically, cells of the mass were consistent in
appearance with equine lymphoma, a malignant tumor of
lymphoid cells. An oxalate nephrosis was also present,
with numerous oxalate crystals present within the renal tubules
of the kidney. Oxalates are toxic to kidney tubules, and cause
destruction of functional tubular parenchyma, as was seen
microscopically in this case.
The source of the numerous oxalates in the animal's kidneys
was probably of internal origin, rather than having an external
source as commonly happens in cats and dogs poisoned by drinking
ethylene glycol (antifreeze). It is possible they were formed
secondary to chronic renal obstruction, as has been previously
described. Secondary disturbances in protein metabolism may also
have played a role.
Return to Table of
Contents
Equine herpes viral abortion
A late-gestational thoroughbred fetus was submitted for
post mortem examination following abortion. Necropsy, including
microscopic examination of fetal tissues, indicated severe,
multifocal necrosis (destruction) of liver tissue, consistent
with abortion by equine herpesvirus-1. The equine fetus also had
interstitial pneumonia and inflammation of the brain,
(encephalitis). Viral studies were positive by the polymerase
chain reaction procedure (PCR) for equine herpesvirus, likely equine
herpesvirus-1.
Return to Table of
Contents
Suspected Alsike clover poisoning in horses
R.E. Clugston
Fixed tissues for histopathological examination were received
from a five year-old miniature horse that died after a
prolonged illness. According to the veterinarian, the owner was
suspicious of Alsike clover poisoning, as the animal,
together with other horses, had been fed this leguminous hay for
several months. Histopathological examination of submitted fixed
tissues revealed toxic injury to the animal's liver (toxic
hepatopathy), characterized by marked portal fibrosis, bile duct
proliferation, and portal inflammatory cell accumulations. These
microscopic findings, although not diagnostic for Alsike clover
poisoning, are certainly characteristic of the condition, and
confirmed the owner's suspicions.
Return to Table of
Contents
Skin tumor in a cougar
R.E. Clugston
A raised, thickened area of hairless skin approximately 5 x 7
cm on the ventral abdomen of a five year-old cougar was examined
microscopically and found to be consistent with sqamous cell
carcinoma, which tends to be a slowly progressive malignant
skin tumor. The cougar was a longtime resident of a wildlife
park.
Return to Table of
Contents
Congenital brain disease in a calf
J. Coates
A five week-old Limousin crossbred calf was submitted
to the AHC for clinical examination prior to euthanasia. The
animal was recumbent, unable to stand on its own, and displayed
"perpetual tremors", which had been present since
birth. Gross post mortem revealed an abnormally small brain
(microencephaly), including a cerebellum about half normal size
for a normal calf of similar size and age. Microscopically, there
was a mild, diffuse, encephalitis present, characterized by mild
lymphocytic cuffing of vessels. Within the cerebellum, Purkinje
cells were reduced in number and some had been displaced into the
molecular or granular layers. Both white matter tracts and the
granular layers of the cerebellum were narrowed and poorly
developed (hypoplastic).
Non CPE-BVD (bovine virus diarrhea) virus was cultured
from a pooled sample of the animal's tissues, and from the buffy
coat (white cell layer) taken from a non-clotting (EDTA) sample
of the animal's blood.
Return to Table of
Contents
Suspected Listerial brain infection in a 15 month-old bull
J. Coates
A 15 month-old Holstein bull had been showing vague nervous
signs for the previous week. The animal had been extensively
treated with intravenous antibiotics by the veterinarian, who,
along with the owner, had kept the animal alive by repeated
stomach tubing with water and a concentrated protein energy
preparation. The veterinarian was concerned about rabies, since
both he and his client had been handling the animal's mouth while
feeding it by stomach tube.
Brain samples were immediately sent to the federal laboratory
at Lethbridge for rabies examination--these tests proved
negative. At the A.H.C., histopathological examination of the
brain's medullary tissue revealed small microabscesses and
other inflammatory changes consistent with bacterial
encephalitis due to Listeria monocytogenes. Bacterial
cultures for the organism were not successful, although the
animal had been on antibiotic treatments intravenously for
several days. The animal had been fed a corn silage ration, a
type of feeding regimen often associated with listerial
encephalitis in cattle. Often widely distributed in the
environment, Listeria moncytogenes is found within corn
silage, and is ingested by the animal at time of feeding. In
goats, some studies have found it to be more common in animals on
woodland browse than those feeding on regular pasture or hay.
(Johnson et al, JAVMA, vol. 208, May 1996)
Encephalitic listeriosis is an important but generally
sporadic worldwide disease of ruminants such as cattle, sheep,
and goats. The organism may also produce bacterial septicemia;
abortion may occur in pregnant animals.
(See comments in The Trouble with Brains on
some of the pratfalls to be avoided when sending in samples for Listeria
sp. encephalitis testing).
Return to Table of
Contents
Nutritional myopathy in lambs
Nutritional myopathy, or white muscle disease,
was diagnosed in a two week-old lamb from a flock that had
suffered heavy losses prior to submission of specimens for
necropsy. With the diagnosis, the owner was able to take
immediate, corrective measures to prevent further losses.
Return to Table of
Contents
Iodine deficiency suspected in lambs
Iodine deficiency characterized by prominent goitre
(enlarged, hyperactive thyroid gland) was diagnosed in three
lambs submitted for necropsy from a flock that had suffered
ongoing losses of lambs characterized by stillbirth or severe
weakness. The owner was urged to contact his veterinarian
immediately for corrective treatment of ewes that had not yet
lambed. Goitre in lambs is usually caused by a deficiency of
iodine in the pregnant ewe's diet.
As in many or most of the cases described throughout this
newsletter, the real significance of the necropsy results on this
lamb was the information provided to the owner to avoid further
losses in the remaining animals in his flock. The positive
economic results arising from a single post mortem diagnosis can
be very substantial for a livestock producer.
Return to Table of
Contents
Traumatic death in an ostrich
Post mortem examination of a mature ostrich that had
died suddenly following no history of illness revealed multiple
fractures of cervical vertebrae C3 and C4. Extensive bleeding
surrounded the spinal cord; the beak of the animal had also been
badly bent. These findings suggested acute trauma as the cause of
injury, likely caused by running into an inert object such as a
building or a fence. Ostriches and other ratites are particularly
susceptible to self-induced fatal trauma, broken necks, or
rupture and hemorrhage of internal organs such as the liver are
often the result when these animals run into objects.
Return to Table of
Contents
Blackhead in turkeys
Post mortem or necropsy examination of five, nine week-old
turkeys raised outdoors in a back yard flock, revealed
changes consistent with "blackhead' (or histomoniasis).
There had been 45 birds in the group; a month earlier, they had
been taken off "medicated" feed. Whether or not the
feed had contained a preventive medication for turkey blackhead
is unknown. Initially, the owner noticed the birds became very
thirsty as their water intake increased greatly. Five birds then
died over the next few days. These birds were immediately
submitted for post mortem examination at the AHC.
Livers on these birds were swollen and discolored, with large
yellow to white areas seen throughout. Ceca were greatly
thickened, inflamed, and contained cheesy, necrotic cores of
purulent material. Microscopically, liver and cecal tissue
contained numerous small unicellular organisms consistent with Histomonas
meleagridis, the causative agent of blackhead in turkeys. The
owner was urged to contact his poultry practitioner for immediate
treatment of the remainder of his flock.
The small protozoan agent that causes blackhead is often a
problem over the summer months in birds raised outside. The
organism is ingested in earthworms picked from the soil, or from
infected cecal worm eggs. Chickens, if allowed to run with
turkeys on outside range, may also spread the disease to turkeys.
Chickens are not usually clinically affected by the organism, but
shed it in their feces where it is protected from dehydration by
being carried within the eggs of the chicken cecal worm, Heterakis
gallinae. The common earthworm may also act as a mechanical
vector in spreading the organism.
Other species susceptible to blackhead or histomoniasis are
pheasants, pea fowl, and bobwhite quail.
NOTE
Did you know the lymphoproliferative tumors produced in
chickens by the herpes virus of Marek's disease was the first
important neoplastic disease in any species, including humans, to
be prevented by the administration of a live virus vaccine?
Development of successful vaccines for control of Marek's Disease
(MD) is a singular achievement both in agriculture and basic
cancer research. Prior to vaccine development, MD had become the
most costly of all poultry diseases.
Return to Table of
Contents
Acute deaths in neonatal mink
J. Coates
A mink rancher submitted a half dozen dead mink kits to the
AHC for necropsy. Ongoing losses in mink litters of one to three
neonatal mink kits per affected litter, aged one to two weeks,
had recently occurred. Neoatal hypothermia (chilling due to low
environmental temperature) was not likely in this case, as older
mink kits up to nearly three weeks of age were also involved, and
temperatures had generally been mild. Initial milk ingestion
after birth (with its concentrations of colostral antibody and
needed energy) had probably been adequate, as there had been no
deaths of mink kits younger than a week of age.
Post mortem findings indicated that many of the kits had died
quite acutely, as most had stomachs moderately filled with fresh
milk. Lungs tissue often appeared congested, and occasionally had
patchy areas of hemorrhage.
Microscopically, the kits had marked suppurative inflammation
of the portal areas of the liver, and most had pneumonia. Escherichia
coli (non-hemolytic E. coli) was cultured from lungs
and livers, as was a hemolytic Staphylococcus aureus. (Staph.
aureus). Either bacterial agent may have been responsible for
the changes seen, which suggested a bacterial septiciemia and
localization of the organisms in lung and liver, with secondary
inflammatory response. Mild brain irritation was also seen in a
few of the submitted mink kits.
E. coli is an established pathogen in neonatal mink,
and hemolytic Staph aureus is a known pathogen in several
species of neonates, including rabbits.
The owner was urged to increase the frequency of nest box
cleaning to reduce bacterial contamination caused from excessive
fecal accumulation. Antibiotic usage was also discussed as an
alternative therapy, if losses continued; this would be achieved
by medicating the nursing mink dams, so that kits would receive
antibiotic medication via ingested milk.
Return to Table of
Contents
Canine distemper in a litter of pups
Canine distemper was diagnosed on necropsy on two 8-10 week
old pups from the Interior that had been showing signs of central
nervous system (CNS) involvement, including spontaneous barking,
pacing, inappetence, and depression.
The animals were in very poor body condition on necropsy, with
atrophy of body fat stores and anemia. Fecal examination did not
reveal any significant level of intestinal parasites or worms.
Both animals had pneumonia. There was a mild nonsuppurative
inflammation of the brain, most evident within the cerebellum,
medulla, and brain stem. Structures resembling intranuclear
inclusion bodies occurred within medullary transitional
epithelium of the kidneys. Lung tissue was positive for canine
distemper virus using the fluorescent antibody procedure, and on
tissue culture.
These pups had never been vaccinated. Several other pups from
the same litter became ill over the next ten days, showing
similar clinical signs. All or most have died or have been
euthanized after prolonged illness.
Canine distemper is a worldwide, highly contagious disease of
young dogs. Clinical signs are usually linked to involvement of
lung, brain, or intestinal tract, though runny eyes, skin
eruptions, and sore foot pads may also be seen. Many of the
pathological changes in naturally occurring cases are due to
bacterial complications. The disease is well controlled by a good
vaccination program. Pet owners and practitioners are reminded
that canine distemper is always circulating among the dog
population, and that presenting clinical signs can be vague and
variable. Failure to vaccinate will usually be evident in the
animal's history. A differential diagnosis to canine distemper in
dogs showing nervous signs is rabies.
Return to Table of
Contents
Antifreeze poisoning in a dog
Acute ethylene glycol toxicity (antifreeze poisoning) was
diagnosed in a dog that died after three days of severe illness,
characterized by vomiting, lack of appetite, depression, and anuria
(absence of urine formation and excretion). Diagnosis was based
on necropsy findings, which revealed swollen and congested
kidneys. Microscopically, there were myriads of birefringent
oxalate crystals seen within distended, damaged renal tubules.
From the veterinary practitioner's point of view, microscopic
examination of urine sediment from an affected animal should
reveal oxalate crystals in their urine when it is first presented
clinically. These crystals are often "wheat-sheaf" in
appearance and are birefringent under polarized light.
The owner of this animal found a plastic pail containing
traces of ethylene glycol at the rear of her yard, just inside a
fence that separated the property from a back lane. This was
evidently a case of deliberate poisoning.
Return to Table of
Contents
Lead toxicity and suspected blackleg in a calf
Lead toxicity was diagnosed in a nursing calf from a Vancouver
Island beef herd. The animal was found dead at pasture. Kidney
lead levels were measured at 100 ppm. Although no distinct
lesions were seen on the tissues sent in to the laboratory from
the practitioner, the organism of bovine blackleg, Clostridium
chauvoei, was detected in heart blood and heart muscle using
the fluorescent antibody (FA) procedure. The likely cause of
death in this animal was blackleg, though it would have died in
any event, considering the high kidney levels of lead.
The owner found several discarded batteries at pasture which
had been recently licked and chewed; the grassy area around the
batteries had been flattened and disturbed. Steps were
immediately taken to remove all toxic materials from the grazing
area. Discussions with the owner by the veterinary practitioner
indicated he had lost calves the previous year due to blackleg.
The remaining animals were immediately given blackleg
vaccinations and long-acting prophylactic penicillin injections,
with a second booster vaccination to follow in a few weeks. This
was an unusual combination of both a toxic and infectious agent
within the same animal.
Blackleg is an infectious disease, primarily of young cattle
less than two years of age, caused by the bacterial organism Clostridium
chauvoei. The organism usually localizes and proliferates in
muscle tissue such as the loin, thigh or neck muscles, or
possibly the diaphragm or heart. A potent exotoxin that actually
kills the animals is secreted by the proliferating bacteria. The
site of muscle injury and exotoxin proliferation is often, though
not always, detected on necropsy. In affected areas, the muscle
takes on a toasted, blackened appearance, hence the name
"blackleg". Affected muscle has a strong butyric, or
abnormally sweet, odour.
Although a specific site of muscle injury was not detected on
the animal by the veterinary practitioner, identifying the
organism circulating within the dead animal's blood and within
submitted heart muscle via laboratory tests is good
circumstantial evidence of the disease. Spores of the organism
are very hardy, and may survive in soil for many years. A
vaccination program, carefully designed to assure effective
antibody levels in animals of the most susceptible age group, is
the best way to avoid the disease. For details, please see your
veterinary practitioner.
Return to Table of
Contents
Poet's Corner
Remembering the Sea
"...From these Alberta's sealess plans,
I don't forget the English sea,
Linked with all oceans round the world....
...I don't forget my friend the sea,
Immense, divine, caressing.
Although I seek you here in vain,
Remembrance itself is a blessing."
- excerpts from the poem An Immigrant
Remembers the Sea,
by poet Marjorie Ramsay .
Return to Table of
Contents
Are there new types of BVD virus?
Information presented at a symposium on BVD in Guelph,
Ontario, April, 1994, described antigenic, genomic, and
structural differences between the BVD viruses (Type-2 strains)
isolated from outbreaks in Ontario and Quebec in 1992, 1993 and
1994, and older BVD strains (Type-1 or Classic strains). BVD
vaccines are antigenically derived from Type-1 strains. There is
no experimental data suggesting that the differences between
Type-1 and Type-2 strains influence vaccine efficacy in the
field. Field evidence strongly supports the efficacy of the
vaccines currently available.
The BVD viruses presently causing problems among cattle in
Ontario and Quebec are slightly different from older viruses, but
they are not really new. BVD viruses like these have been found
in the United States and other Canadian provinces since at least
1987. The Type-2 viruses do not always cause disease outbreaks.
Outbreaks seem to require more factors than just the presence of
the virus. Resistance to BVD, either from vaccination or previous
infection, is important in determining whether animals become
sick after being infected.
"...Outbreaks (of BVD) have occurred in herds that never
received an initial double immunization (primary series) of
killed vaccine as directed on the label. Single annual
vaccination with killed vaccine does not provide immunity to BVD
unless preceded by a primary series."
-- from CEPTOR, vol. 2, No. 2, June 1994, newsletter of the
Ontario Mini story of Agriculture. Editor's note: there is
a new live BVD vaccine presently being offered on the Canadian
market by Bayer. For information, see your veterinarian.
Return to Table of
Contents
Cryptosporidiosis in calves and other species
Over the last few months, notably during the late winter and
spring, we have had our share of positive cases of cryptosporidia
in young calves, both beef and dairy animals, usually from a week
to 6 weeks of age. This agent is usually one of several that
singly or in combination with other microbes wreak havoc among
young calves. Often, in any one case of calf diarrhea, we have
difficulty in assessing the significance of this agent.
Cryptosporidium sp. occasionally turns up in routine
fecal testing where the cause of diarrhea in a calf or calves is
sought. Often, other agents such as rotavirus or coronavirus (or
both) , or secretory strains of E coli such as 0157:K88,
are involved. The organism is not always readily identifiable
microscopically on positively reacting calves, suggesting numbers
of the organisms present in the gastrointestinal tract are likely
quite low, or that the correct area for microscopy was not
fortuitously sampled. Some of these calves are
hypogammaglobulinemic; that is, they have low colostral antibody
titres when these are available for examination at the AHC using
blood serum. The point here is that cryptosporidia are often
opportunists, in this writer's view, and contribute to illness in
an animal that has other, perhaps more serious underlying
problems or infectious agents to contend with. Nevertheless,
cryptosporida is considered a primary disease producing agent in
young cattle (Radostits, Blood, and Gay, Veterinary Medicine,
1994).
Diarrhea may vary in degree from mild to severe and is usually
transient with eventual complete recovery if other factors don't
tip the scales too much in favor of the microbe. The diarrhea is
poorly responsive to medications commonly used to fend off
bacterial organisms and , in the writer's experience, often
produces a dark green, watery stool. Keeping the animal
sufficiently hydrated will permit it to heal via its own immune
response, which is the main objective of treatment.
The organism's eggs (or oocysts) are sporulated at the time of
shedding so it is immediately infectious (Garber et al, JAVMA,
1994, pp 86-91). This is in contrast to most coccidial oocysts,
which require a four to five day sporulation period after
shedding prior to becoming infectious. This characteristic makes
it very difficult to completely eliminate the organism from the
calf's environment, although thorough cleanups will go a long way
in reducing the parasite's numbers.
The test used at the AHC to detect cryptosporidia in fecal
specimens is an ELISA test. The test is rapid and accurate. Like Giardia,
Cryptosporidium sp. is a potential zoonotic agent and may
spread from animals to man.
Return to Table of
Contents
The Trouble with Brains
Working as a pathologist in the AHC, this writer has the
opportunity to review submissions from veterinary practitioners,
and occasionally from private individuals, requesting examination
of an animal's brain for a variety of conditions such as rabies,
listerial encephalitis, poliomalacia, etc.
The one agent that occasionally receives short shrift on these
submissions is Listeria monocytogenes, the bacterial agent
causing the cattle brain infection known as "circling
disease". This organism may also produce disease in other
domestic species such as sheep and goats, rarely in swine, and
potentially is also a zoonotic (i.e., an agent capable of being
transmitted from animals to man).
Practitioners are well aware that this Gram positive bacterial
organism may cause brain infection in these species, and it may
also cause a generalized septicemia and abortion, as well.
Fortunately, in cases of circling disease, fairly characteristic
lesions are detectable microscopically in the brain, and the
organism is usually successfully cultured from tissues, though
sometimes brain cultures are negatively influenced by prolonged
antibiotic use prior to the death of the animal.
From a pathologist's point of view, success in confirming the
practitioner's clinical diagnosis by histopathological
examination of brain tissues is sometimes markedly impaired or
made impossible, due to receiving inadequate brain tissue
submissions.
When sending in brain for examination, and especially when Listeria
sp. (circling disease) is suspected, please be sure to include
the brain stem, medulla, and cerebellum. The characteristic
microabscesses of Listeria sp., with its attendant meningeal
reaction, is commonly only seen in the medullary area of the
brain stem. If slices of cerebral cortex are the only portions
submitted, it is highly likely that the lesion will not be
present, and so the diagnosis of listerial encephalitis cannot be
confirmed. Bacterial culture of the brain is also frequently
unsuccessful unless portions are taken from the medulla; the
organism is often simply not present in other areas of the brain.
A good deal of physical effort goes into manually removing a
brain from a larger animal such as a cow, or bull; it can be
difficult, especially when the animal may have received the 'coup
de grace' from a rifle shot. Despite hemorrhage from the bullet's
path, however, most of the brain is still very readable
histologically, and certainly capable of being cultured.
Take time to send as much of the brain as possible to the
laboratory, no matter what your tentative diagnosis. A
mid-sagittal brain cut, with half the entire brain enclosed fresh
and the other half enclosed in buffered 10 per cent formalin, is
worthwhile. No one likes to receive a "no histologic
diagnosis" on a necropsy report from the laboratory after
going to so much trouble to remove a brain. Furthermore, no
pathologist enjoys sending it out, so be especially careful to
send in the brain stem including the medulla and
overlying cerebellum if your clinical diagnosis is listerial
encephalitis.
Return to Table of
Contents
Diagnosing Johne's Disease: an update on AHC
techniques
In a nutshell, things have changed.... a lot. In earlier
times, rapid confirmation of this chronically debilitating
condition in cattle, sheep, goats, and occasionally in related
ruminant species was limited to acid fast stains of fecal smears
or rectal biopsies. These results could be positive or negative,
though a negative wasn't necessarily a real negative; another
fecal sample taken a day or a week later may turn up as positive.
The imprecision of these results were frustrating for
practitioner and laboratory diagnostician alike, just as attempts
to culture the organism still are. Culturing is generally not a
practical step in diagnostic laboratories, as the organism takes
from four to 10 weeks to grow (Carter's Diagnostic Procedures
in Veterinary Bacteriology and Mycology, 4th edition, 1984).
Fortunately, things have changed for the better. At the AHC,
we have serology tests for Johne's Disease. The test used at the
AHC for Bovine Johne's Disease is a blood serum ELISA test.
Sensitivity on this test is only fair at 66 per cent (that is,
only about two thirds of the truly positive animals will respond
positively to this serum antibody test). However, the specificity
of the test is very high at 96 per cent (indicating the accuracy
of actual positives is very high). At present this is the
recommended serology test for Johne's disease in cattle.
In sheep and goats, an agar gel immunodiffusion test (AGID) is
used for the detection of serum antibodies. Again, sensitivity is
somewhat lacking at 26.6 per cent. However, the accuracy of
positive reactors to the tests is virtually 100 per cent.
Despite mediocre to poor sensitivity, these serum tests can
still be very useful in the ongoing screening of suspected or
problem herds for the Johne's agent, Mycobacterium
paratuberculosis, as all reactors are truly positive.
At the present time,
 Dr. John Robinson of the AHC
is evaluating a polymerase chain reaction (PCR) test for Johne's
disease, which relies on the detection of specific DNA or protein
chains of the organism being detected in tissue or fecal
specimens. PCR testing of suspected Johne's field specimens
submitted to the AHC on a routine or experimental basis in all 3
species has been promising, and this test is now being used in
conjunction with the other diagnostic tests described above.
The serology tests offer practical relief to veterinary
practitioners and owners attempting to clean up chronic problems
with Johne's Disease in a group of animals. We hope that the PCR
test which Dr. Robinson has been developing will also provide
rapid and accurate testing of individual animals. Dr. Henry
Lange, field veterinarian with the AHC, is able to assist
veterinary practitioners in utilizing these various tests within
effective control strategies aimed at eliminating the organism
from a herd or flock.
Return to Table of
Contents
On veterinarians and veterinary medicine
"Why doesn't veterinary medicine toot its own horn? Why
doesn't it let people know the extent to which
veterinarians...have contributed to their health and standard of
living? Is it because most veterinarians never learned or have
forgotten the great achievements made in the past, and because
few members of the profession appreciate the full scope of the
contributions being made to society by today's veterinarians?
...My impression is that the failure of the veterinary
profession to adequately advertise its accomplishments is
responsible for the public's perception of what a veterinarian
does, is being based mainly on the portrayal of the veterinary
practitioner by James Herriot in his books...The problem is that
the public has no conception of what members of the profession
and others allied to it have done in the past and are doing today
in so many areas that impact on its health, well-being, and
standard of living: contributions, for example, to the practice
of human medicine and surgery; to the understanding, control, and
eradication of zoonotic diseases, such as rabies, tuberculosis,
salmonellosis; to animal welfare; to the protection of the
environment; to the research, diagnosis, control and prevention
of enzootic diseases within, and of foreign diseases entering,
the national herd, poultry flocks, and fish stocks.
...People, by and large, esteem those professions they
perceive as having a direct effect on their lives, so until they
are made aware that the veterinary profession is one of them,
veterinarians are going to be faced with the problem of image.
...In his review of Laurie Garrett's book, The Coming
Plague: Newly Emerging Disease in a World out of Balance,
Nusbaum writes, 'The book is full of lessons for the veterinary
profession. In a list of 16 disciplines that contribute to
disease control, Garrett does not include veterinary medicine. We
obviously have not caught her attention. Our greatest lesson
should be that resources and honors go to those professions that
contribute in a highly visible way to human health'.
...Rest assured, if we don't promote our profession as a major
contributor to human health and general well-being, no one else
will."
- comments by Dr. Doug Hare, Editor-in-Chief, Canadian
Veterinary Journal, Feb. 1996, vol 37., pp 69-70.
Return to Table of
Contents
Fifth anniversary for Diagnostic Diary
This issue marks the fifth anniversary of Diagnostic Diary,
our first issue being published in the summer of 1991. Of course
there were newsletters sent out previously, but not quite in the
format we have presently adopted. We hope you find Diagnostic
Diary informative, interesting, and easy to read.
The purpose of this newsletter is to inform and to share
knowledge between those of us at the Animal Health Centre and our
readers. By sharing interesting cases, often those of a flock or
herd nature, as well as the more esoteric individual cases, we
hope to heighten the awareness of our readers. The newsletter
also records changes or improvements in diagnostic tests carried
out at the AHC.
If you have any comments or ideas as to how we can improve Diagnostic
Diary, please let us know. Our address and telephone number
is at the bottom of D.D's first page. We welcome your
suggestions. Sincerely, Ed.
Return to Table of
Contents
On Learning
"A lecture is the procedure whereby the notes of the
lecturer are transferred to the notebook of the student,
generally without passing through the mind of either. It is
however, the criterion of a good lesson that the student
remembers it without effort...
...There is a great pleasure in learning a science, not
because of the power and glory it gives us, but because knowledge
is a heightening of consciousness, and it is therefore just as
instinctively desirable as is undesirable the reverse state of
unconsciousness and death...
...Scientists often seem to be matter-of-fact people,
unromantic and even hard headed; that is because the scientific
attitude is realistic, as opposed to ritualistic. But there is a
vague, continuously satisfying glow of emotion about any science,
and he who has accepted and learned its discipline is marked for
life. For example, there is a richness of the culture of biology
that compares to the most intense affectations that artistic
people have about their environment..."
- from Experimental Surgery, by J. Markowitz, J.
Archibald, and H. G. Downie, 5th edition, Williams and Wilkins
Co., Baltimore, 1964
Return to Table of
Contents
Poet's Corner
My House Faces East
I planted twelve sunflowers to face my house,
To look at in September.
As I sat on my porch when the day was done
To dream and think and remember.
The flowers bloomed well as I weeded and watered.
I look, but they aren't much fun;
They show me their backs quite plainly
But their faces are turned to the sun.
- by Canadian Poet Marjorie
Ramsay, from her book of poems entitled "Half a Centennial
is Better than None ...." published 1967. Born in London,
England, during a Zeppelin raid in March 1918, Ms. Ramsay crossed
the pond to Canada in 1956. Ms. Ramsay presently resides in
Truro, Nova Scotia, happily once again near the sea, and happily
near her son, Dr. Wm. Bruce Ramsay (OVC 66) and his family. With
Ms. Ramsay's permission, we are happy to offer to you, our
reader, small snippets from her poems and writings throughout
this newsletter. Ed.
Return to Table of
Contents
Focus on Staff
Former Director, Dr. John Bankier (1902- 1979)
John Cassells Bankier (OVC 1927) was born in Mitshill,
Scotland, May 25, 1902, and immigrated to Canada in 1923.
 His contributions to the establishment of
veterinary pathology diagnostic service in British Columbia are
still with us today.
In 1946, British Columbia had no staff veterinary pathologist,
nor any veterinary laboratory facilities. Realizing a genuine
need, Bankier immediately set out to change this. One year later,
as an employee of B.C. Veterinary Services, Dr. Bankier
established the first veterinary diagnostic laboratory in British
Columbia, in an old two-roomed house in Victoria. These
facilities were later expanded in 1951 with the opening of the
B.C. Department of Agriculture Pathology Laboratory, which
consisted of a small wooden hut on the U.B.C. campus.
Over the years, veterinary diagnostic services gradually
increased with demand. Due largely to Bankier's dogged
determination that the province and its citizens deserved better
diagnostic facilities, he was given the task of designing a new
laboratory. These efforts resulted in the opening of the
Abbotsford Veterinary Laboratory on Gladwin Road on Oct. 22,
1965, which was later officially named the John Bankier Building.
1997 will mark the fiftieth anniversary of continuous
provincial veterinary diagnostic service in British Columbia. No
small thanks on this occasion will be due to the contributions of
the visionary, yet pragmatic Dr. John Bankier, founding Director
of the province's first diagnostic pathology laboratory (with
thanks to Dr. Jeremy Greenfield, AHC Bacteriology section. Ed).
Return to Table of Contents
Return to Animal Health Centre Home Page
|
