Infectious Diseases of the Dog and Cat, 3rd Edition
CHAPTER 7 Nonrespiratory Parainfluenza Virus Infection of
Dogs
Craig E. Greene
ETIOLOGY
Canine parainfluenza virus (CPiV) is a member of the family
Paramyxoviridae, which includes canine distemper virus, simian
virus 5 (SV-5), and human measles and mumps viruses. Human, simian,
and canine type 2 parainfluenza viruses have all been called
SV-5-like viruses because of their close antigenic relationship.
Monoclonal antibody studies have shown minor antigenic differences
between SV-5 isolates.11 Whether different SV-5 isolates are
transmitted among people, nonhuman primates, and dogs remains to be
established. The virus associated with respiratory disease in dogs
is CpiV,5 which causes an acute, self-limiting cough in the
syndrome of canine infectious tracheobronchitis (ITB, see Chapter
6) and is recognized worldwide as an important cause of respiratory
disease in dogs.1,10 Serologic studies indicate that the overall
prevalence of CPiV in the canine population is high but variable.
Experimental inoculation of CPiV in newborn pups can cause viral
spread to internal tissues. Evidence shows that related but
distinct paramyxoviruses may cause systemic or nonrespiratory
infections in older dogs.6 In addition, parainfluenza virus was
consistently isolated from the prostatic fluid of a dog.12
CLINICAL FINDINGS
A parainfluenza virus variant was isolated from the
cerebrospinal fluid (CSF) of a 7-month-old dog with ataxia and
paraparesis lasting 3 to 4 days.7 The dog had been vaccinated
against canine distemper at 7.5 weeks of age. Gnotobiotic puppies
inoculated intracerebrally with this virus isolate developed two
forms of clinical illness.3,4 Some developed acute encephalitis
characterized by seizures, myoclonus (involuntary rhythmic muscle
contractions), and progressive neurologic signs within a few days
after inoculation. Five of six inoculated dogs observed for 6
months after inoculation developed internal hydrocephalus, although
clinical signs were not noted at the time. The hydrocephalus was
thought to result from ependymitis with decreased absorption of
CSF, with or without aqueductal obstruction (see Chapter 84 for an
additional discussion about this type of hydrocephalus from
suspected infectious causes). Seven-week-old seronegative ferrets
intracerebrally inoculated with this CPiV isolate have also been
found to develop a self-limiting nonsuppurative ependymitis and
choroiditis.2 A 6-week-old puppy was found in extremis as a result
of acute hemorrhagic enteritis.4 Although a paramyxovirus variant
was isolated, it has not been confirmed that it was responsible for
the clinical illness.
At present, it is uncertain whether the central nervous system
or gastrointestinal forms of disease caused by paramyxoviral
variants occur with any frequency under natural circumstances.
Neurologic illness has been more commonly recognized as a
complication of other paramyxovirus infections, such as with canine
distemper in dogs (see Chapter 3) and in people with measles and
mumps viruses (see Chapter 25). In laboratory rodents, other
paramyxoviruses have been shown to produce encephalitis and
hydrocephalus that are very similar to those that result when the
paramyxoviral variant is injected into dogs. Naturally occurring
encephalitis, periventriculitis, and hydrocephalus of a suspected
bacterial origin have been described in young dogs (see
Periventricular Encephalitis, Chapter 84).
627
7.1
7.2
CHAPTER 7 Nonrespiratory Parainfluenza Virus Infection of
Dogs
Page 1 of 2
Infectious Diseases of the Dog and Cat, 3rd Edition
DIAGNOSIS
Paramyxovirus-induced encephalitis or hydrocephalus may be
confirmed serologically by the hemagglutination inhibition assay;
however, because of the high prevalence of antibody in canine
populations and the routine use of a vaccine for CPiV, confirmation
requires demonstration of a rising serum antibody titer. CSF
antibody titer to this variant virus was shown to remain
persistently high in dogs after experimental infection.7 Viral
isolation can be performed using CSF or brain tissue of infected
dogs. In addition, direct fluorescent antibody methods can be used
to detect viruses in nervous tissue. For cases of enteritis, virus
isolation and electron microcopy of feces would be most valuable.
Serologic techniques such as virus neutralization or HI must be
used to distinguish these variant paramyxoviral strains from
CPiV.
PATHOLOGIC FINDINGS
Gross pathologic findings have been identified only in
experimentally infected dogs that became hydrocephalic. Moderately
enlarged lateral and third ventricles are present. Microscopically,
acute meningoencephalitis was characterized by multifocal neuronal
necrosis, lymphoplasmacytic cellular infiltrates, and reactive
gliosis. Focal ependymitis was also apparent. Flattening and
discontinuities of the ependymal cells lining the ventricles were
seen in dogs developing hydrocephalus. Ultrastructurally, the virus
could not be found in the brains of dogs developing hydrocephalus
and encephalitis that were examined 1 to 6 months after
experimental infection. In the previously mentioned puppy with
enteritis, the intestinal and gastric contents were blood tinged.
Atrophy of small intestinal villi, mucosal congestion, and lymphoid
necrosis were noted.
THERAPY AND PREVENTION
The prevalence of paramyxoviral variant diseases is unknown at
present, and they have no known treatment. It is possible that the
CPiV vaccine, which was developed for ITB (see Chapter 6), may help
to prevent these other paramyxoviral diseases.
Suggested Readings*
* See the CD-ROM for a complete list of references.
6. Evermann, J: Paramyxovirus infections of dogs. Vet Rec. 117,
1985, 450451.
12. Vieler, E, Herbst, W, Baumgartner, W, et al.: Isolation of a
parainfluenza virus type 2 from the prostatic fluid of a dog. Vet
Rec. 135, 1994, 384385.
Uncited references
9. Macartney, L, Cornwell, HJ, McCandlish, IA, et al.: Isolation
of a novel paramyxovirus from a dog with enteric disease. Vet Rec.
117, 1985, 205207.
6263
7.3
7.4
7.5
7.6
7.7
CHAPTER 7 Nonrespiratory Parainfluenza Virus Infection of
Dogs
Page 2 of 2
