Gourt Home::Gourt :: Parvovirus
Parvovirus, commonly called parvo, is a genus of the Parvoviridae family linear, non-segmented single stranded DNA viruses with an average genome size of 5 kbp. Parvoviruses are some of the smallest viruses found in nature (hence the name, from Latin parvus meaning small).
Many types of mammalian species have a strain of parvovirus associated with them. A parvovirus tends to be specific about the taxon of animal it will infect. That is, a canine parvovirus will affect dogs, wolves, and foxes, but will not infect cats or humans.
Structure
The viral capsid of parvovirus is made up of 3 proteins known as VP1, VP2 and VP3 that form an icosahedral structure that is resistant to pH, solvents and temperature up to 50°C.
Inside the capsid is a single stranded DNA genome. At the 5’ and 3’ ends of this genome are palindromic sequences of approximately 115 nucleotides long that form hairpins, which is essential for viral genome replication.
Parvovirus Replication
In order to enter host cells the parvovirus binds to a cell surface receptor. Once in the host cell the viruses DNA genome is translocated to the nucleus where transcription of non-structural proteins into mRNA occurs first before being transported out of the nucleus into the cytoplasm where the host ribosomes translate the viral mRNA into viral proteins. Next the CAP (capsid) proteins are transcribed and translated in the same way as the non-structural proteins. The replication of the viral genome can now occur. The process by which the parvovirus genome is expressed is poorly understood, although host DNA polymerase is needed for replication. Once the genome has replicated it is packaged inside the viral capsid within the cytoplasm.
Parvoviruses do not have an envelope and so are only released when the cell undergoes lysis.
In order for viral replication to take place the infected cells must be non quiescent cells (those which are actively undergoing mitosis). This is because the virus relies heavily on the host cells replication machinery and therefore require the cell to pass through S phase. Unlike polyomaviruses, parvoviruses are unable to turn on DNA synthesis in host cells.
Diseases
Parvoviruses can cause disease in some animals. Because the viruses require actively reproducing cells in order to replicate, the type of tissue infected varies by the age of the animal. The gastrointestinal tract and lymphatic system can be affected at any age, leading to vomiting, diarrhea and immunosuppression, but cerebellar hypoplasia is only seen in cats that were infected in the womb or at less than two weeks of age, and disease of the myocardium is seen in puppies infected between the ages of three and eight weeks.
Canine parvovirus is a particularly deadly disease among young puppies, causing gastrointestinal tract damage and dehydration as well as a cardiac syndrome in very young pups. It is spread by contact with an infected dog's feces. Symptoms include lethargy, severe diarrhea, fever, vomiting, loss of appetite, and dehydration. Mouse parvovirus 1, however, causes no symptoms but can contaminate immunology experiments in biological research laboratories. Porcine parvovirus causes a reproductive disease in swine known as SMEDI, which stands for stillbirth, mummification, embryonic death, and infertility. Feline panleukopenia is common in kittens and causes fever, low white blood cell count, diarrhea, and death. Infection of the cat fetus and kittens less than two weeks old causes cerebellar hypoplasia. Mink enteritis virus is similar in effect to feline panleukopenia, except that it does not cause cerebellar hypoplasia. A different parvovirus causes Aleutian disease in minks and other mustelids, characterized by lymphadenopathy, splenomegaly, glomerulonephritis, anemia, and death. The most accurate diagnosis of parvovirus is by ELISA. Dogs and cats can be vaccinated against parvovirus.
Parvovirus B19, which causes fifth disease in humans, is a member of the Erythrovirus genus of Parvoviridae rather than Parvovirus.
References
Further reading
Feline Parvovirus by Cats Protection Parvoviruses | Animal diseases
"Parvovirus"