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Distemper, Canine 271

Client Education SUGGESTED READING AUTHOR: Jonathan F. Bach, DVM, DACVIM, DACVECC
Development of DIC represents a severe Stokol T: Laboratory diagnosis of disseminated EDITOR: Jonathan E. Fogle, DVM, PhD, DACVIM
VetBooks.ir past, the present and the future. Vet Clin Small Diseases and Disorders
complication of many systemic diseases.
intravascular coagulation in dogs and cats: the
Anim 42(1):189-202, 2012.

Video
Distemper, Canine Client Education Available
Sheet

BASIC INFORMATION • Generalized distemper manifests initially • Systemic and neurologic signs are not always
as a respiratory infection followed by present at the same time. Often, neurologic
Definition gastrointestinal (GI) signs and often CNS disease occurs 1-3 weeks after recovery
Viral disease caused by a morbillivirus of the signs; CNS signs may manifest concomitant from systemic signs, but the two forms can
family Paramyxoviridae. Clinical disease includes with or after resolution of respiratory and coincide. Rarely, the neurologic signs will
mild to severe systemic illness with high morbid- GI signs. occur weeks to months later.
ity and variable mortality (mortality often related • Old-dog encephalitis (ODE), a rare and
to central nervous system [CNS] infection). chronic form of panencephalitis, likely results Etiology and Pathophysiology
from an inflammatory reaction associated • Certain strains of CDV are more virulent
Synonyms with persistent canine distemper virus and neurotropic.
Distemper, hardpad disease (CDV) infection of the CNS gray matter. • Shedding of the virus begins by the seventh
Signs can include ataxia, compulsive move- day after infection and may continue for up
Epidemiology ments such as head pressing or continual to 90 days.
SPECIES, AGE, SEX pacing, and uncoordinated hypermetric • Shedding is primarily aerosol; the virus can
• Dogs, especially urban or suburban dogs gait. Systemic signs are not associated with also be recovered from urine, feces, nasal and
between 3 and 6 months of age this form. ocular secretions, and skin.
• Other susceptible species include additional • Chronic relapsing demyelinating encepha- • After initial exposure, CDV replicates
members of the order Canidae (e.g., coyote, lomyelitis is a persistent, spontaneous CDV in the upper respiratory epithelial tissue
wolf, fox), ferrets, mink, skunk, raccoon, infection. macrophages. Macrophages are carried
sea mammals, and selected members of the • Inclusion-body polioencephalitis is a variant by the local lymphatics to the tonsils and
order Felidae (e.g., lions, tigers). of the disease that can occur after vaccination retropharyngeal and bronchial lymph nodes.
and manifests only as a CNS disease. The Here, the virus multiplies and disseminates
GENETICS, BREED PREDISPOSITION pathogenesis is similar to that of ODE. systemically in mononuclear cells, creating
More common, and higher mortality rates, in an initial fever and leukopenia 3-6 days after
dolichocephalic versus brachycephalic breeds HISTORY, CHIEF COMPLAINT exposure. Lymphopenia is associated with
With the generalized form of the disease, viral damage to T and B lymphocytes.
RISK FACTORS initial presentation typically includes one or • Viremia occurs by the ninth day after infec-
Exposure to infected animals, inadequate vacci- more of the following: lethargy, ocular and tion as the virus spreads hematogenously
nation, immunocompromise, and transplacental nasal discharge (serous or mucopurulent), to epithelial tissues and the CNS. Occur-
transmission cough, inappetence, vomiting, and diarrhea. rence of viremia depends on host humoral
A patient with a more advanced form of the and cell-mediated immunity. Infection of
CONTAGION AND ZOONOSIS disease often has a history of neurologic signs epithelial tissue correlates with shedding of
Highly contagious (aerosol route common) (e.g., seizures, ataxia, myoclonus). the virus and occurs through all epithelial
between infected and susceptible individuals; secretions, even in animals with subclinical
not zoonotic PHYSICAL EXAM FINDINGS infections.
• Systemic disease: as above; fever, ocular ○ Dogs with adequate humoral and cell-
GEOGRAPHY AND SEASONALITY signs (keratitis, conjunctivitis, uveitis), loud mediated immunity clear the virus by day
Worldwide distribution breath sounds on auscultation, dehydration, 14.
cachexia, poor haircoat. Dental abnormalities ○ Dogs with an intermediate level of immu-
ASSOCIATED DISORDERS (dental enamel hypoplasia, tooth impaction, nity have infection of epithelial tissues
• Hyperkeratosis of the footpads (hardpad oligodontia) in dogs that survive neonatal by day 14. Clinical signs that develop
disease) infections. eventually resolve if the antibody titer
• Ocular signs (anterior uveitis, optic neuritis, • Neurologic disease: signs indicate encephalitis increases and the virus is cleared from
retinal degeneration, keratoconjunctivitis) can or encephalomyelitis (seizures, vestibular most tissues. Some virus may persist in
develop with systemic disease or as a sequela. signs, cerebellar signs/hypermetria, paresis). footpads and CNS.
• Postencephalitic epilepsy Seizures commonly manifest as chewing-gum ○ In dogs with poor immunity, virus spreads
• Myoclonus seizures (vigorous repetitive opening and to many tissues by day 14, including
• Persistent anosmia (loss of sense of smell) closing of the mouth) but can be generalized. skin, endocrine glands, exocrine glands,
possible in recovered patients Hyperesthesia attributable to viral menin- and epithelial cells of the GI tract, the
gitis is uncommon. Myoclonus (rhythmic respiratory system, and the genitourinary
Clinical Presentation twitching of the head, neck, or one or tract.
DISEASE FORMS/SUBTYPES more limbs) occurs as the disease progresses • Clinical signs are often severe. Secondary
• Subclinical to mild disease is probably most and is very suggestive of canine distemper bacterial infections are common; although
common, but systemic/generalized form is (see Video). Optic neuritis and chorioretinitis this advances morbidity, studies indicate it
the most recognized. can be observed. does not increase mortality.

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