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Canine Parvovirus

History

Canine parvovirus, otherwise known as "parvo" is caused by the canine parvovirus type 2 virus. CPV was first discovered in European dogs in 1976. Over the course of two years, it had caused a widespread gastroenteritis epidemic in dogs, predominantly affecting puppies.⁸ Parvovirus not only affects dogs but also wild animals including raccoons, skunks and foxes.⁴ It is currently believed that CPV mutated from Feline Panleukipenia virus through several genetic mutations.⁵ CPV2 has a high rate of evolution due to it's increased rate of nucleotide substitution, as shown in RNA virus like the Influenzavirus. A rare variant of the disease may be seen in neonatal puppies which causes inflammation of the heart muscle.¹⁰

Infection

The capsid of the virus performs many complex steps including DNA replication, nuclear export, cell receptor binding etc.⁴ The capsid also protects the genome during transfer and while infecting animal hosts. Depending on the type of virus, the capsid may be species specific. The parvoviral capsid also includes protrusions or spike-like exclusions at the icosahedral threefold axes.⁴ The protrusions have been mapped to be the place of antigenicity whereas the twofold spikes attach to host cells.⁹

Diagnosis

CPV is typically diagnosed through detection of the CPV2 virus in feces using ELISA, or enzyme-linked immunosorbent assay. Other methods of detection include electron microscopy or a hemagglutination test. As the disease progresses, the virus becomes less likely to be detected in the feces by ELISA. When it has caused gastroenteritis, diagnoses can be misdiagnosed as coronavirus or other forms of enteritis causing diseases.¹⁰ When CPV has infected the pericardium, diagnoses can be made easier and quicker.⁸

Treatment

CPV has no approved treatment and can quickly progess depending on the age of the canine, and how much treatment is administered.¹ Most cases of CPV are treated using supportive care, preventing dehydration and increasing quality of life. Vaccination is the best prevention for lethal CPV cases and tests should be administered as soon as avaliable. Supportive case includes intravenus fluids, antibiotic injections, and anti-inflammatories.¹⁰

Structural highlights

Primary structure - 564 amino acid chain

Secondary structure - Antiparallel Beta Strand.

Tertiary structure - Antiparallel Beta Barrel.

Quarternary structure - Icosahedral Hetero 180-mer.

CPV is a relatively small icosahedral structure measuring 20 to 26 nm in diameter. It contains three major capsid proteins, known as VP1, VP3, and VP2. VP1 is a structural protein that is present with a specific N-terminal peptide inside the capsid. Each capsid subunit is formed from an eight-stranded .This motif is a common motif found in many viruses. The CPV surface is made up of loops that connect the β strands. Each icosahedral 2-fold axis contains "spikes" that recognize receptivity and antigenicity of the host. These spikes bind to the transferrin of the host cells. The entire genome is about 5000 nucleotides long.