Transcript Distemper Paul R Earl Facultad de Ciencias Biológicas Universidad Autónoma de Nuevo León San Nicolás, NL 66451, Mexico.

Distemper
Paul R Earl
Facultad de Ciencias Biológicas
Universidad Autónoma de Nuevo León
San Nicolás, NL 66451, Mexico
Canine distemper (CD), related to measles, is
caused by a morbillivirus through sneezing and
nasal discharges, and other transmissions of body
fluids from saliva to urine. Once the virus CDV has
entered the central nervous system (CNS), the dog
will likely die.
This is a very common and important disease,
largely preventable by a 3-dose vaccination, live
or attentuated. It is absolutely necessary to try to
protect dogs against CDV. Of course, almost all
dog owners know this disease by its nerve
damage. Parvovirus-caused diseases in dogs like
the one causing Aleutian disease in mink and
panleukonpenia in cats are also well known and
preventable.
One polyvalent vaccine can include CDV,
adenovirus Type 2, hepatitis, parainfluenza,
parvovirus, Leptospira canicola and L.
icterohaemorrhagiae. Another polyvalent
vaccine is CDV-Adenovirus Type 2Coronavirus-Parainfluenza-Parvovirus type
2b vaccine, modified live and killed viruses
with the 2 major Leptospira spp. Other
viruses like rabies are also sometimes
combined as polyvalent vaccines.
See http://www.pitt.edu/~super1/lecture/
lec10911/index.htm
Morbilliviruses
These contain 6 structural proteins.
Three internal proteins are associated
with the negative-strand genome: the
nucleocapsid protein (N),
phosphoprotein (P) and large protein
(L). On the inner leafet of the envelope
there is a matrix protein (M) which
probably plays a role in budding and
the structural integrity of the virus.
Protruding from the envelope are 2
glycoproteins (gp), hemagglut-inin (H) protein
and fusion (F) protein. Two additional nonstructural proteins are generated from the P
gene either by translation of an overlapping
open reading frame for the C protein or, by
insertion of an extra G residue in the P mRNA.
mRNA is generated for the V protein, which is
amino-coterminal with P protein but which
terminates in 70 residues C-terminal. The genes
for the N, P, V, C, M, F, H and L proteins are
ordered on the 3' to 5' on a negative-stranded
genomic template of 15±7±--15±9 kb. The
epitopes on the H protein can be of interest
when involved in making vaccines.
Paramyxovirus. University of Warwick.
Wild animals
Distemper is a worldwide disease of many
wild and domestic animals. Most carnivores
are susceptible to natural CD. Mammalian
families that are commonly infected include:
Canidae (dog, fox, wolf) Felidae (cat, lion,
tiger) Procyonidae (racoon, panda) and
Mustelidae (ferret, skunk, weasel, badger),
aside from marine mammals like dolphins
and whales. The lethal virus in seals is
closely related phocine distemper virus, not
CDV.
Vaccination
One aim of vaccination (immunization) is to
acquaint the dog’s immune system with the
pathogen by presenting a killed or modified form
of the pathogen. Another aim is to vaccinate the
population 'sufficiently' so that an outbreak
cannot not occur.
The animal will then be protected from
becoming ill when exposed to the real thing.
The 2 major parts of the immune system are
humoral immunity (B lymphocytes that produce
antibodies) and cell-mediated immunity
(T lymphocytes that destroy defective and
infected cells). Vaccination is critical in the
prevention and control of disease, and a great
success.
Newborns can respond immunologically,
perhaps weakly, at birth. Passive immunity is
provided to them by antibodies that are passed
mainly in the colostrum from the dam to the
offspring in the 1st 24-72 hours after birth. Eighttwo percent to 98 % of the maternal antibodies
come from the colostrum, while only 2-18 % of
antibodies are transferred in utero.
The amount of antibody the young receive
depends on the antibody titer of the dam, and
how much colostrum each newborn receives.
Maternal antibodies interfere with the capacity of
the young to respond to vaccination by
inactivating the vaccine just as if it is the real
pathogen.
Vaccines
Routine vaccines include 1/ CDV,
2/ parainfluenza, 3/ adenovirus-2,
4/ parvovirus and 5/ compulsory
rabies. Consider also canine corona
virus (CCV) that causes enteritis.
Major CDV, CPV and vaccines of the
2 viruses combined are now given.
PFIZER ANIMAL HEALTH
(the Vanguard Puppy Vaccine)
INTERVET (the Progard Vaccine)
MERIAL (the Recombitek C4 and C6
vaccines). Merial is supported by
Rhone-Merieux and Merck.
FORT DODGE (the Puppy Shot)
SCHERING-PLOUGH ANIMAL HEALTH
(the Galaxy Vaccine)
Rabies
In all states, rabies vaccinations are required by
law. The first rabies vaccination is good for one
year. In many states, subsequent vaccinations
are good for 3 years. In other states, they are
only valid for one year by law. Please check with
your vet to determine the legal requirements in
your state.
Vaccinating your pet for rabies may literally save
its life for 2 reasons. Rabies is a threat in many
areas, and it is a horrible disease. In addition, an
unvaccinated pet who bites a human being is
subject to long quarantine periods or even death
for the purpose of testing for rabies infection of
the brain.
As rabies can infect ALL MAMMALS and be fatal,
its vaccination in dogs, cats & ferrets should be
compulsory. Five companies in the US--Fort
Dodge, Pfizer, Intervet, Merial, Bayer and Aventis
Pasteur--produce 28 rabies vaccines. Also
Schering-Plough is marketing vaccines made by
other companies.
The Imovax rabies vaccine produced by Aventis
Pasteur is a sterile, stable, freeze-dried
suspension of rabies virus prepared from strain
PM-1503-3M obtained from the Wistar Institute of
the University of Pennsylvania in Philadelphia.
Signs of CD
The first sign of distemper is eye discharge that
may appear watery to pus-containing. Later,
dogs develop fever, nasal discharge, coughing,
lethargy, reduced appetite, vomiting and
diarrhea. Still later, the virus may attack the
nervous system, causing seizures, twitching,
partial or complete paralysis. CDV causes
demyelinating encephalomyelitis. That is, the
covering of the neurons is destroyed.
Distemper is often fatal. Even if a dog does not
die from the disease, CDV can cause irreparable
damage to a dog’s nervous system. However,
some dogs mount a strong immune response
within 2-3 weeks and recover spontaneously.
Pathology
Aerosol transmission from respiratory
secretions is the main route of transmission.
Virus shedding begins about 7 days post
infection. Lymphopenia is always present
during the early infection.
The virus spreads first to local lymph nodes.
Within 7 days, it spreads to all lymphatic
tissues. During this period of 3-6 days
postinfection, the 1st rise of temperarure
occurs along with the appearance of
interferon in the circulation.
Depending on the virus strain, the signs
may be more related to acute grey matter or
subacute white matter disease. Seizures and
myoclonus with hyperesthesia and
depression predominate in grey matter
disease.
Incoordination ataxia, paresis, paralysis and
muscle tremors occurs in white matter
disease. Meningeal signs of hyperesthesia
and cervical rigidity may be seen in both.
Optic neuritis and retinal lesions also may
occur. Hard footpads and hardness of the
nose are produced sometimes.
The clinical course, severity of the disease and
neuropathology vary with the virus strain. Dogs
either die within 3 weeks or recover. Lesions in
the neuraxis are those of a encephalomyelitis.
With some less aggressive strains,
demyelination can be the predominant finding.
Some dogs succumbed, generally around 28-42
days postinfection, while others recover.
Strains like R252 and A75-17 induce delayed,
white matter disease with a mixed pattern of
mortalities, persistent infections or recoveries.
Neutralizing antibody responses often correlates
with the disease course. Dogs which die have
low serum titers or lack antibody. Recovering
dogs have the earliest and highest titers.
Canine distemper encephalomyelitis is the
most common form of CDV infection and often
begins as gastrointestinal and respiratory
disturbances: vomiting, diarrhea, coughing
and seromucopurulent eye-nose discharges.
Hyperkeratosis of the footpad may be seen.
Many animals have conjunctivitis and
chorioretinitis.
Cortical and subcortical signs include
generalized seizures and sometimes
personality changes, such as depression and
disorientation. Signs of localization in the brain
stem include incoordination, falling, turning to
one side and nystagmus.
Neuronal changes including nuclear pyknosis and
shrunken cells, chromatolysis and neuronophagia
are found in the cerebral cortex, pontomedullary
nuclei, Purkinje cells and gray matter of the spinal
cord. In some dogs, hippocampal cells can be
selectively involved. Intranuclear and
intracytoplasmic inclusions bodies may be present
in neuronal cells, astrocytes, histiocytes,
meningeal cells, and ependymal cells.
The distribution of inclusion bodies in distemper
virus encephalitis is erratic, and their presence is
not an indication of the severity of the disease
process. Changes in the white matter vary
according to the duration and intensity of the
infection.
Demyelinating lesions can be focal or
disseminated. Nerve fibers may undergo
degeneration, resulting in the formation of
swollen axonal ovoids. Pronounced gliosis
may be evident in association with these
changes. In many severe lesions, there is
evidence of tissue necrosis, edema and
macrophage infiltration. These lesions are
often situated in the cerebellar peduncles or
in the central white matter.
Also, CDV can produce chronic multifocal
encephalomyelitis. Dogs may have such
symptoms for months.
Courtesy of Michael Oglesbee
Courtesy of Michael Oglesbee
Courtesy of Michael Oglesbee
Parvoviridae
Members of the family Parvoviridae are small
eukaryotic DNA viruses that infect a variety of
animal species, including humans.
The genome is minus-sense, single-stranded DNA
and the virus has no envelope.
Canine parvovirus (CPV), feline panleukopenia
virus (FPV) and viruses similar to FPV like blue fox
parvovirus, the raccoon parvoviruses and mink
enteritis virus are all host variants of the carnivore
parvoviruses.
CPV evolved as a new pathogen in dogs in1976
from FPV. The new virus hit an unprotected
population, caused a dramatic pandemic and
infected virtually all populations of domestic and
wild carnivores worldwide.
Ferrets
Etiology. CDV, Morbillivirus, pantropic virus
replicates in epithelium and lymphoid tissues.
Transmission. Aerosol.
Clinical. Mucopurulent oculonasal discharge,
papular rash under chin, perianal, inguinal; “orange”
hyperkeratotic planum nasale and footpads,
photophobia, acute mortality; central nervous signs,
tremors, convulsions, coma. Disease progression
10-40 days with profound immunosuppression
Pathology. Bilateral nasal and ocular discharge,
suppurative bronchopneumonia, acute death without
gross lesions; eosino-phillia, 2-5 µm intranuclear and
intracytoplasmic inclusions especially in the cells of
the urinary bladder, renal pelvis, biliary epithelium,
neurons. Encephalitis with demyelination.
Aleutian disease
Etiology. Parvoviridae, Aleutian disease virus.
Transmission. Orofecal, aerosol, in utero; shed
subclinically for months, persists in the
environment.
Clinical. Plasma cell proliferation,
hypergammaglobulinemia >20% serum protein,
glomerulonephritis, vasculitis, insidious 2 year
progressive disease,
Pathology. Prominent plasmacytic infiltrate in
renal interstitium, portal triads, spleen,
membranous glomerulonephritis, tubular protein
casts, splenomegaly, pale, tan kidneys.
Coronavirus
Etiology. Coronaviridae, Epizootic Catarrhal
Enteritis.
Transmission. orofecal, prolonged shedding.
Clinical. high morbidity, low mortality,
vomiting and dark green diarrhea with
abundant mucus;
Pathology. Often no gross lesions, clear fluid
lumen content; vacuolar degeneration and
necrosis of apical enterocytes, marked villous
atrophy, fusion, blunting; later, enteritis with
marked lymphocytic infiltration.
Parvovirus
Found throughout the world, parvovirus is a
highly contagious disease agent that attacks
the intestinal tract, the white blood cells and
sometimes the heart. It is spread through
contact with the feces of infected dogs and can
be carried on shoes, crates, equipment, or on
the hair or feet of infected dogs. One infected
dog at a show, a canine expo, a shelter or any
other facility where dogs congregate can spread
the virus to hundreds of unprotected dogs.
Symptoms of parvo appear 5-7 days after
exposure and include depression, loss of
appetite, vomiting and severe diarrhea.