Things to Remember about DNA Viruses

DNA Viruses Remember HHAAPPPIC for:

  • Herpesviruses
  • Hepadnaviruses
  • Adenoviruses
  • Asfarviruses
  • Papova = Polyomaviruses and Papillomaviruses
  • Parvoviruses
  • Poxviruses
  • Iridoviruses
  • Circoviruses

All DNA viruses replicate in the nucleus except POX replicate in the cytoplasm

All DNA viruses are dsDNA except PARVO and CIRCO ssDNA

All DNA viruses are icosahedral except POX is complex

Below is a summary of DNA virus families based on criteria for classification and their properties. The detail for each DNA virus family is covered on separate topics.



Family name Poxviridae Asfarviridae

(Asfar=African swine fever and related viruses)

Circoviridae Parvoviridae Herpesviridae Adenoviridae Hepadnaviridae

(Hepadna=hepatitis DNA virus)

Iridoviridae Papillomaviridae Polyomaviridae
Genome ds linear DNA ds linear DNA ss circular DNA, ambisense (+/-) ss linear DNA (+) or (-) sense ds linear DNA ds linear DNA ds circle gapped DNA ds linear DNA ds circular DNA ds circular DNA
Genome size 130-280 kbp 190 kbp 1.7 kb 5 kb 120-200 kbp 36-38 kbp 3.2 kbp 150-350 kbp 5-8 kb 5-8 kbp
Symmetry of capsids Complex Icosahedral Icosahedral Icosahedral Icosahedral Icosahedral Icosahedral Icosahedral Icosahedral Icosahedral
Naked or enveloped Enveloped Enveloped Naked Naked Enveloped Naked Enveloped Naked/Enveloped Naked Naked
Baltimore class I I II II I I VII I I I
  Baltimore class I: ds DNA viruses: These viruses usually must enter the host nucleus before it is able to replicate (except Poxviridae). These viruses require host cell DNA polymerases to replicate the viral genome and hence are highly dependent on the cell cycle. Proper infection and production of progeny require that the cell is in mitosis as that is when the cell’s polymerases are active. The virus may induce the cell to forcefully undergo cell division, and chronically, this may lead to the transformation of the cell and ultimately, cancer.

dsDNA → mRNA

Baltimore class II: ssDNA viruses: Replicate within the nucleus using host cell DNA polymerases and form a dsDNA intermediate during replication

ssDNA → dsDNA → mRNA

Baltimore class VII: gapped ds DNA viruses: They have gapped genome and they undergo reverse transcription during maturation as opposed to retroviruses. RNA is formed as intermediate product then DNA.


Virion 170-200×300-450nm 200nm 20 nm 18-26nm 150-200nm 70-100 nm 42nm 125-300 nm 40-45 nm 45-55nm
DNA polymerase + +
Genus and species Orthopoxvirus:   Cowpox virus, Camelpox virus

Parapoxvirus: BoPS, Orf virus, pseudocowpox virus

Avipoxvirus:    Fowlpox virus, turkeypox virus

Capripoxvirus:   Goatpox virus, LSD virus, sheeppox virus

Leporipoxvirus:    Rabbit fibroma

Suipoxvirus:   Swinepox


African swine fever     virus










BoHV1, BoHV2, SuHV1, EHV1, EHV3, CaHV1, FeHV1 Mardivirus:

GaHV1, GaHV2




 Fowl adenovirus A-E


Ovine adenovirus D

Canine adenovirus,

Caprine adenovirus

Bovine adenoviruses A-C,

Human adenoviruses A-F


Hepatitis B virus


Duck hepatitis B virus


Lymphocystis disease virus of fish


Ranaviruses of fish, amphibians, and reptiles


Bovine polyoma virus (BPyV)

BK virus (human)


Simian virus 40 (SV40)


Bovine papillomavirus (BPV) type 1;

Human Papillomavirus

Disease Lumpy skin disease African swine fever PMWS caused by PCV2 Canine parvovirus caused by CPV Pseudorabies (Aujeszky disease) caused by SuHV1   Duck hepatitis B Lymphocystis disease in fish

Ranaviral disease

  Bovine papillomavirus caused by BPV1
Hosts Cattle (Bos taurus, zebus, domestic buffaloes) Wild and domestic pigs Domestic pigs Dogs Domestic pigs     Fish, amphibians and reptiles   Cattle
Clinical signs Randomly distributed nodules (5-50 mm) in the skin and subcutaneous tissue. Multifocal, roughly circular necrotic areas on the muzzle, respiratory tract, buccal cavity, forestomachs, abomasum, vagina, teats, udder and testes High fever (40-42°C), haemorrhages in the reticuloendothelial system and skin. Vomiting and haemorrhagic diarrhoea. Death within 3 to 14 days. wasting, dyspnea, enlarged lymph nodes, diarrhea, pallor, and jaundice in weaned piglets


Intestinal form: depletion of lymphocytes in lymph nodes and necrosis and destruction of the intestinal crypts. Vomiting and bloody diarrhoea

Cardiac form: sudden death

Asymptomatic, but PRV can cause abortion, high mortality in piglets, and coughing, sneezing, fever, constipation, depression, seizures, ataxia, circling, and excess salivation in piglets and mature pigs.     Transformation and hypertrophy of cells in the dermis, connective tissues of various internal organs forming grossly visible lymphocystis nodules.   Cutaneous warts
Laboratory diagnosis EM, Inoculation of primary cell culture of lamb or calf testis cells followed by HE, DIF, virus neutralisation; ELISA PCR, ELISA, IB, haemadsrption IPMA, IF, ELISA Detection of CPV2 in the faeces by EIA, HA, EM or PCR ELISA, PCR EM, ELISA, FI, HI, PCR   Cell culture, histopathology, serology, PCR, IF   PCR
Target cells   macrophages monocyte/ macrophage lineage and different types of epithelial cells Rapidly dividing cells e.g. epithelial cells in crypts of Lieberkuhn Trigeminal ganglion neurons         Basal and parabasal cells of the epidermis (keratinocytes)
Cellular Virus receptors   CD163 GAG: HS and CSB Transferrin receptors (TfR) Heparan sulphate, herpesvirus entry mediator (HVEM), Nectin 1 and 2,         GAG heparin sulphate

Alpha6beta4 integrins

Viral attachment ligand   p72 and p54 in virus attachment and p30 in virus internalization Capsid protein Capsid protein gB, gC, gD, gH and gL          
Virus replication   Entry via clathrin-mediated endocytosis Entry via clathrin-mediated endocytosis, pH-dependent replication, virus assembly in the nucleus Entry via clathrin-mediated endocytosis, pH-dependent replication, and intact viruses enter the nucleus Entry by fusion, transport to the nucleus along microtubules, egress by exocytosis Entry via clathrin-mediated endocytosis, pH-dependent replication, virus assembly in the nucleus       Entry via clathrin mediated endocytosis, genome uncoating in cytoplasm, genome import to nucleus, cytolysis
Transmission mechanical Contact faecal-oral route Oral-nasal infection oral or nasal contact         Direct contact
Reservoir host   wild swine (warthogs and bushpigs)        
Vector Arthropod bite (stable fly Stomyxos calcitrans and Biomyia fasciata)) Argasid ticks Ornithodoros moubata and O. erraticus        
Control Homologous attenuated virus vaccine: Neethling strain

Heterologous attenuated virus vaccine: sheep pox vaccine

No vaccine available, hygiene, prevent contact between wild and domestic pigs Hygiene, Vaccination with recombinant PCV2 capsids Vaccination: Live attenuated parvovirus Vaccination         Prophylactic and therapeutic vaccination


PMWS=Post Weaning Multisystemic Wasting Syndrome; PCV1, porcine circovirus type 1; PCV2, porcine circovirus type 2, BFDV, Beak and feather disease virus; CAV, chicken anaemia virus; CPV, canine parvovirus; PPV, porcine parvovirus; ChPV, chicken parvovirus; AAAV, Avian adeno-associated virus; BAAV, bovine adeno-associated virus; CAAV, canine adeno-associated virus; BoHV1, Bovine herpesvirus 1 ;  BoHV2, Bovine herpesvirus 2 ; SuHV1, Suid herpesvirus 1 ;  EHV1, Equine herpes virus 1; EHV3, Equine herpes virus 3 ; CaHV1, Canine herpes virus 1; FeHV1, Feline herpes virus 1; GaHV1, Gallid herpes virus 1; GaHV2, Gallid herpes virus 2; AlHV1, Alcelaphine herpes virus 1;  BoPS, Bovine papular stomatitis; LSD, Lumpy skin disease; BPV1, IPMA=Immunoperoxidase monolayer assay; IB=Immunoblotting Assay


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