Distemper

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Distemper
Paul R Earl Facultad de Ciencias
Biológicas Universidad Autónoma de Nuevo León San
Nicolás, NL 66451, Mexico
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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.
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One polyvalent vaccine can include CDV,
adenovirus Type 2, hepatitis, parainfluenza,
parvovirus, Leptospira canicola and L.
icterohaemorrhagiae. Another polyvalent vaccine
is CDV-Adenovirus Type 2-Coronavirus-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
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MorbillivirusesThese 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.
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Protruding from the envelope are 2 glycoproteins
(gp), hemagglut-inin (H) protein and fusion (F)
protein. Two additional non-structural 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 157--159
kb. The epitopes on the H protein can be of
interest when involved in making vaccines.
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Paramyxovirus. University of Warwick.
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Wild animalsDistemper 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.
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VaccinationOne aim
of vaccination (immunization) is to acquaint the
dogs 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.
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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. Eight-two 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.
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VaccinesRoutine vaccines
include 1/ CDV, 2/
parainfluenza, 3/ adenovirus-2,
4/ parvovirus and 5/ compulsory rabies. Consider
also canine corona virus (CCV) that causes
enteritis.
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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)
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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.
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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.
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Signs of CDThe 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 dogs nervous
system. However, some dogs mount a strong immune
response within 2-3 weeks and recover
spontaneously.
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PathologyAerosol
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.
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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.
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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.
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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.
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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.
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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.
21
Courtesy of Michael Oglesbee
22
Courtesy of Michael Oglesbee
23
Courtesy of Michael Oglesbee
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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.
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FerretsEtiology. 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.
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Aleutian diseaseEtiology.
Parvoviridae, Aleutian disease virus.Transmission
. Orofecal, aerosol, in utero shed subclinically
for months, persists in the environment.Clinical.
Plasma cell proliferation, hypergammaglobulinemia
gt20 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.
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CoronavirusEtiology.
Coronaviridae, Epizootic Catarrhal
Enteritis.Transmission. orofecal, prolonged
shedding.Clinical. high morbidity, low
mortality, vomiting and dark green diarrhea with
abundant mucusPathology. 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.
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ParvovirusFound 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.