The Parvoviridae is a family of small, non-enveloped viruses that contain a single-stranded DNA genome of approximately 5,000 bases. Plus and minus DNA strands are packaged into separate virions in approximately equal proportion and they can be classified by size, morphology, and genomic organization.
Members of the family Parvoviridae infect a wide variety of hosts, ranging from insects to primates, with replication taking place in the nucleus of dividing cells. Generally, parvoviruses cause a wide range of acute or chronic diseases; however, many of them are not known to be associated with any disease.
Parvoviruses in humans
Parvovirus B19 is a widespread virus pathogenic for humans and a member of the Erythroparvovirus genus in the Parvoviridae family. It was discovered serendipitously in 1975 when blood donors were screened for hepatitis B. The virus is widespread, with a myriad of various manifestations depending on the immunologic and hematologic status of the host.
Characteristics of such ample range of pathologies and outcomes depend on the interplay between the pathogenetic potential of the virus, its adaptation to diverse cellular environments, and the physiological and immune status of the infected individuals. It causes aplastic anemia in patients with sickle cell disease, fifth disease in childhood (erythema infectiosum), arthropathy in adults, and rare fetal infections.
The virus has a marked tropism for erythroid progenitor cells in the bone marrow, exerting a cytotoxic effect and causing a block in erythropoiesis that can be manifested as erythroid aplasia. Wide circulation of the virus and prevalent benign and self-limiting clinical course generally lead to a diminished appreciation of its pathogenetic potential.
Adenoassociated viruses (AAV) are also members of the Parvoviridae family which appear to infect humans without causing clinical manifestations and have been used as vectors for gene transduction and gene therapy. The first human adenoassociated virus was discovered in 1965, as a contaminant of adenovirus preparations.
Parvoviruses in animals
Parvovirus in dogs is a potentially fatal infection that can damage the intestines and result in severe diarrhea and dehydration. Canine parvovirus type 2 (CPV-2) emerged in late 1970s causing severe epizootics in kennels and dog shelters worldwide, and soon became endemic in the global dog population.
Feline panleukopenia virus has almost identical DNA sequence as canine parvovirus, but this one does not harm dogs. It causes disease in all felids, as well as in some members of related families (such as raccoons or minks). It is commonly referred to as feline distemper and causes fever, low white blood cell count, diarrhea and sometimes even death.
Porcine parvovirus is the major causative virus in a reproductive failure syndrome in swine, are characteristic symptoms are grouped under an acronym SMEDI (which stands for stillbirths, mummified fetuses, early embryonic death, and infertility). This infection has been reported to occur worldwide with variable prevalence rates.
Two specific parvoviruses of rats, RV (Kilham rat virus) and H-1 virus, are highly pathogenic for fetal and infant rats. Although the infections are usually subclinical, they can also seriously damage central nervous system, liver, lymphoid system, and other tissues. In colonies where the infection is endemic, a majority of rats develop antibodies and become immune by the time they are seven months old.