Parrot herpesvirus See psittacid herpesvirus

parrot papillomavirus A possible member of the Papillomavirus genus, family Papovaviridae.

Parry Creek virus (PCRV) An unassigned vertebrate rhabdovirus. Isolated from mosquitoes, Culex annulirostris, in Australia. Some antigenic relationship to members of the genus Lyssavirus. Not known to cause disease in humans.

Calisher CH et al (1989) Intervirology 30, 241

parsimony (stinginess, niggardliness, miserliness) An approach to the construction of a phylogenetic tree that selects the phylogeny that minimizes the number of evolutionary changes required to explain the data. Used extensively to build trees based upon nucleotide sequences.

Hillis DM et al (1993) Meth Enzymol 224, 456

Paru virus A possible member of the genus Orbivirus, isolated from phlebotomine flies in the Amazon region of Brazil. Antigenically related to Changuinola virus. Not known to cause disease in humans.

Parvoviridae (Latin: parvus = small) A family of small DNA viruses. Virion diameter, 18-26nm, non-enveloped, composed of 60 copies of the capsid protein with icosahedral symmetry. Buoyant density (CsCl): 1.39-1.42g/ml. Genome consists of one molecule of linear single-stranded DNA, 4-6kb in length, mol.wt. 1.5-2.2 x 106. G+C content: 41-53%. In some genera the single strands from virions are complementary and, after extraction, these come together to form a double strand. Infectivity ether-resistant and relatively heat-stable. Replication occurs in the nucleus and is dependent on either certain functions of the host cell, or on a helper virus. There are two subfamilies: (1) Parvovirinae, genera Parvovirus, Erythrovirus and Dependovirus; and (2) Densovirinae, genera Densovirus, Iteravirus and Contravirus. The members of the Densovirinae subfamily only infect arthropods.

Siegl G et al (1985) Intervirology 23, 61 Siegl G and Cassinotti P (1998) In Virology, vol. 1 of Topley & Wilson's Microbiology and Microbial Infections, Ninth edition, edited by BWJ Mahy and L Collier. London: Arnold, p. 261

Parvovirinae A subfamily of the family Parvoviridae which includes only viruses that infect vertebrates or vertebrate cell cultures. There are three genera: Parvovirus, Erythrovirus and Dependovirus.

Parvovirus A genus of the family Parvoviridae. Type species Mice minute virus. Parvoviruses replicate in susceptible cell cultures without a helper virus. Mature virus particles contain only positive strands of DNA which have a hairpin structure at both the 5' and 3' ends of the otherwise single-stranded molecule. There are many species infecting a variety of vertebrates and most are host-specific. A number of parvoviruses have been isolated from cell lines, and their origins are therefore doubtful. Only the feline and related viruses are known to cause disease in the wild. The patho-genicity of the rodent viruses in the laboratory suggests parvoviruses may cause non-acute disease in humans and other animals. Replication in cell culture is best in rapidly dividing cells derived from tissues of the natural host, but usually produces only slight or transient CPE, making detection difficult. However, many species hemagglutinate,


and infected cells hemadsorb. No group antigen and no antigenic relationship to other DNA viruses.

Berns KI (1990) Microbiol Revs 54, 316

Paschen bodies Elementary bodies found in cells infected with Variola or Vaccinia viruses. See also Buist bodies. Synonym: chlamydozoa variolae.

passage Infection of a host with a virus or a mixture of viruses with subsequent recovery of the virus from that host (usually after one infection cycle). Can be used to separate a specific virus from a mixture of viruses, or (through a series of passages) a virus can be adapted to grow well in a host in which it originally grew poorly.

passenger virus Any non-pathogenic virus. When isolated from diseased tissue it has no causal relationship to the disease process.

passive hemagglutination A serological test which can be used to detect a virus-specific antibody by coating red blood cells with viral antigen. If viral antibody is present in test samples, the red blood cells will agglutinate. See reverse passive hemagglutination.

Pasteur virus A strain of Rabies virus.

patas monkey herpesvirus deltaher-pesvirus Synonym for cercopithecine herpesvirus 7.

McCarthy K et al (1968) Lancet ii, 856

Pata virus (PATAV) A serotype of Eubenangee virus in the genus Orbivirus. With Eubenangee, Ngoupe and Tilligerry viruses forms the Eubenangee serogroup. Isolated from Aedes palpalis in Central African Republic. Not reported to cause disease in humans.

pathogen An organism or virus which causes a disease.

Pathum Thani virus (PTHV) A strain of Dera Ghazi Khan virus in the genus Nairovirus. Isolated from a tick, Argas robertsi, in Thailand. Not reported to cause disease in humans.

Patois virus (PATV) A species in the genus Bunyavirus, belonging to the Patois serogroup. Isolated from cotton rats, Sigmodon hispidus, and mosquitoes of Culex sp in Panama and Mexico. Not reported to cause disease in humans.

Paul-Bunnell antibody Heterophile antibodies characteristic for infectious mononucleosis (glandular fever), described by Paul and Bunnell in 1932. They are predominantly IgM, but their mode of formation is not fully understood. In the Paul-Bunnell test, they are detected by agglutination of sheep ery-throcytes.

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