Canine Distemper

Syn: Canine Influenza, Hard pad Disease

• It is acute, highly contagious viral disease of carnivorous animals characterized by diphasic fever, ocular and nasal catarrh and frequent cutaneous eruptions.
• It is often manifested by bronchopneumonia, gastroenteritis, and encephalitis.
• Dogs < 1 year (3-6 months) are most susceptible.
• It affects gastrointestinal, respiratory, skin, immune and CNS.

Etiology:

• Morbilli virus of Paramyxoviridae family
• Pleomorphic, enveloped, ss RNA virus
• It is sensitive to ether and fragile in nature.

Epidemiology:

• It is distributed worldwide and is endemic in many areas.
• Mortality rates can be high, especially in puppies.
• All members of Canidae (wolves, fox, coyote, jackal), Mustelidae (ferret, mink, skunk, otter, weasel) are susceptible to distemper.
• Disease is noted in all age group but young ones between age group of 3-6 months are more susceptible and case fatality rate in them are maximum.
• Wild animals can act as reservoirs for CDV, potentially leading to spillover events into domestic dog populations or vice versa.

Transmission:

• Inhalation (droplet or aerosol), air borne disease
• Virus is discharged through secretions and excretions
• Ingestion of contaminated food and water

Pathogenesis:

• Inhalation of infected droplets
• Multiplication in respiratory epithelium and alveolar macrophages
• Spread to tonsil and bronchial lymph nodes
• Virus circulates in blood associated with lymphocytes
• It reaches to bone marrow, spleen, brain, thymus, cervical and mesenteric lymph nodes

Clinical Signs:

Disease appears in 3 phases:

1. Mild infection with favorable prognosis:

• Inappetance and depression
• Slight rise of temperature
• Recovery of animals

2. Generalized infection with poor prognosis:

• Characteristic biphasic fever (105-107°F)
• Nasal discharge, cough
• Respiratory distress
• Loss of appetite, vomition, diarrhoea
• Diarrhoea feces may contain blood
• Hyperkeratosis of skin in foot pad and nose and becomes thickened, so called hardpad disease.
• Pain and lameness
• Vesiculo-pustular eruption on ventral aspect of abdomen and on inner part of thigh
• Mucopurulent ocular discharge and conjunctivitis.

3. Infection with Nervous Complication:

• Chorea (Jerky movement of group of muscles) or convulsion
• Epileptic form fits may be observed
• Restlessness, excitement, chewing movements, excessive salivation
• Muscular spasm may be observed in lips, cheeks, jaw, head, neck or limb.

PM Findings:

• Congestion of brain and meninges
• Perivascular cuffing in meninges and brain
• Reduction in size of thymus, depletion of lymphocytes
• Thickening of alveolar walls, hyperplasia, proliferation of alveolar epithelium
• Signs of catarrhal or hemorrhagic enteritis
• Degenerative changes in renal and bladder epithelium

Diagnosis:

• On the basis of history of vaccination
• On the basis of clinical findings and PM findings
• Isolation of virus and identification by immunofluorescence test
• Demonstration of eosinophilic, intra-cytoplasmic and intra-nuclear inclusion in stained epithelial cell.
• Hematological examination: Marked leukopenia
• Serological test: FAT, SNT, VNT, ELISA
• Animal inoculation test: Dogs or ferrets are to be inoculated with suspected materials and observation are to be recorded about clincal signs, lesions and inclusion bodies. Intracytoplasmic eosinophilic inclusion bodies are noted in conjunctiva or vaginal epithelial impressions.

Differential Diagnosis:

1. Kennel cough complex (Canine infectious tracheobronchitis):

• It is caused by bacteria.
• Coughing, nasal/ocular discharge
• Cough is usually dry, hacking type, paroxysmal often worsens with excitement or pressure on trachea
• Disease is self-limiting; in 1-3 weeks

2. Canine adenovirus-2 (CAV-2 infection):

• Systemic signs are absent. It is confined to respiratory
• Fever is mild/absent.
• Discharge is usually serous to mucopurulent (milder).

3. Canine parvovirus:

• More hemorrhagic diarrhoea, leukopenia
• Severe vomiting, dehydration is noted in CPV

4. Rabies:

• No history of vaccination or history of late vaccination
• Animal present furious form before slipping into nervous form

5. Toxoplasmosis:

• It is usually caused by protozoan parasite.
• Respiratory signs are less dominant
• Absence of hyperkeratosis of skin

Treatment and Control Measures:

• There is no specific drugs or treatment for viral disease.
• Symptomatic treatment is done.
• Antibiotic therapy to counter secondary bacterial infection.
• To reduce fever; antipyretics such as meloxicam @ 0.2 mg/kg, b.wt. IM or SC
• Antiemetic drugs; Ondansetron @0.5 mg/kg, PO or IV, q12-24 hour
• Pantoprazole @0.7-1 mg/kg, b.wt. PO or IV SD
• Anti-distemper serum (homoserum) @1-5 ml/kg, b.wt. IV, SC or IM
• Injection immunoglobulin 10% @0.01 ml/kg, b.wt. IM, OD
• Lardopa (500 mg) ½ tab, OD followed by every ½ tab every week to check chorea.
• Water-soluble B vitamins is administered.
• Combined vaccine of Parvo, Distemper, Hepatitis, Para-Influenza, Leptospirosis. 1^st vaccination: 7-9 weeks, Second: 12-14 weeks and then annually.