Pox Virus 1 and 2 Flashcards
Poxviridae family has two subfamilies which one are we interested in and which one doesn’t matter and why?
We are studying Chordopoxvirinae (poxviruses of vertebrates), because we don’t care about poxviruses of insects (Entomopoxvirinae)
Properties of Poxviruses
Large sometimes enveloped with complex structure (symmetry). Most are pleomorphic, typically brick-shaped. Possess an irregular surface of projecting tubular or globular structures.
On the other hand, members of the genus Parapoxvirus are ovoid, covered with long thread-like surface tubules which appear to be arranged in crisscross fashion, resembling a ball of yarn.
Orthopoxviruses
Appear brick shaped with irregular thread like projecting tubular or globular structures.
Parapoxvirus
OVAL with long threadlike criss crossing of yarnlife tubules.
IMV and EEV both are infectious what is the difference?
EEV contain 2 membranes : Envelope and Inner Membrane. Virions that are released from cells by budding, rather than by cellular disruption, acquire the extra envelope that contains virus encoded proteins from host cell membrane.
IMV only have an inner membrane and they come out by disruption of host cell and only have an inner membrane. Come out by lysis of the host cell.
Do pox confirm to icosahedral or helical symmetry?
NO it is COMPLEX.
What is on the virion outer layer and how many genes do they have?
Outer layer encloses dumbbell shaped core and two lateral bodies, the core contains viral DNA . Poxviruses have more than 200 genes, and as many as 100 of these encode proteins that are contained in virions.
What does the Genome look like for Pox?
Single molecule of linear ds DNA varying from 130 kbp (parapoxviruses) to 280 kbp (fowlpox virus up to 375 kbp (entomopoxvirus)
Crosslinks that join the two DNA strands at both ends.
Where does replication occur?
Cytoplasm. Poxviruses have the enzymes required for transcription and replication of viral genome. Pox viruses are released by budding or cell lysis. Enveloped virions are taken up by cells more readily and appear to be more important in the spread of virions through the body of the animal.
Antigenic Characteristics
All share group specific nucleoprotein NP exposed following alkaline digestion of the virus. Genetic recombination among the viruses within a genus results in extensive serological cross reactions and cross protections none between different genera. production of hemagglutinin by only ORTHOPOXVIRUSES
How stable are the enveloped pox viruses?
VERY, can withstand dessication and survive for long periods in scabs. Due to low lipid content they are less sensitive to organic solvents/disinfectants compared to other enveloped viruses. High resistance to drying. Can last YEARS in dried scabs or other virus laden material.
Transmission between animals
Skin: has to be broken or lacerated
Respiratory route: by aerosol route, inhalation of aerosol can result in infection as in sheeppox virus.
Mechanically transmitted by biting arthropods, myxoma virus and avipoxviruses
Pathogenesis and immunity
Highly Epitheliotropic, causing cutaneous skin lesions.
Occasionally, poxviruses causes systemic diseases in birds and wild animals, Many poxviruses are host specific, Orthopoxviruse infect a wide range of species.
Spread of Pox
Following intro into the body, pox gains access to the systemic circulation via the lymphatic system. A secondary viremia disseminates the virus back to the skin and to other target organs.
Skin lesions in Pox infection
Macule > Papule > Vesicle > Pustule > Scab > Scar
Rupture of pustule can predispose to secondary bacterial infection. Ulceration may develop. Poxvirus can survive in the dried scabs for many months or years.
Genus ORTHOPOXVIRUS
Cowpox
Distribution: Endemic only in Europe and Asia
Hosts: Cattle, wild and domestic cats, humans, zoo animals
Reservoir host: Rats
Cow pox in cattle, transmission and clinical findings
Cow to cow transmission in a herd through infected milker’s hands or teat cups. Infected farm cats can also transmit the disease, rodents serve as reservoir and can transmit the disease. economic importance: losses to farmers due to inconvenience in milking because of soreness of teats and mastitis from secondary infections. Clinical findings after an incubation period of 3-7 days cows may be febrile, papules appear on teats and udders, suckling calves can get lesions in the mouth. Vesicles may not be evident or may rupture readily leaving raw ulcerated areas that form scabs.
Cowpox in Cats: Transmission: Clinical Signs
usual route is through skin inoculation, through a bite or skin wound. Rodents are a common source. transmission by oral nasal route is also possible. In exotic felids cheetahs, viral pneumonia may be evident. Clinical signs, single primary skin lesion, usually on the head neck or a forelimb. Primary lesion can vary from a small, scabbed wound to a large abscess. Secondary lesion aprox 7-10 days after primary lesion, widespread secondary lesions appear. 2-4 days tehse develop into discrete circular ulacerated papules ~0.5-1 cm in diameter. ulcers soon become covered by scabs and healing is usually complete by ~ 6 wks. Many cats show no signs other than skin lesions but ~20% may develop mild coryza or conjunctivitis, complications from secondary bacterial infections.
Cowpox in Humans
Mainly caused by cuddling cats. Rarely from rodents and zoo animals. Virus is not commonly found in cattle so getting it from cow is very less. Clinical signs is macropapular lesions first observed on hands and face. Later develop into vesicular and then ulceration lesions. Enlarged painful local lymph nodes, patients may report fever, vomiting, and sore throat.
Other Orthopoxviruses Monkey pox
Viral zoonosis with symptoms in humasn similar to those seen in teh past in smallpox patients
Other orthopox In monkeys:
The disease is characterized by generalized skin eruptions, developing to papules on the trunk, face palms, and soles.
Transmission in humans
Primary infection results from direct contact withe blood, bodily fluids, or rashes of infected animals. In Africa human infections have been documented through the handling of infected monkeys, Gambian rats or squirrels
Secondary transmission is human to human with close contact with infected respiratory tract excretions with the skin lesions or with recently contaminated objects.
Distribution of monkeypox
remote villages in central and west Africa near tropical rain forests
Clinical signs in humans same as smallpox
Invasion period 0-5 days fever, intense headache, lymphadenopathy, muscle pain. Skin eruption period, evolution of the rash from maculo-papules lesions with a flat bases to vesicles small fluid filled blisters, pustules, followed by crusts.
