Prevention
is there a vaccine for cowpox?
Yes, life long immunity
Classification of poxviruses?
the family Poxviridae has been divided into two subfamilies: Chordopoxvirinae and Entomopoxvirinae.
The subfamily Chordopoxvirinae is further subdivided into ten genera, including Avipoxvirus, Capripoxvirus, Cervidpoxvirus, Crocodylidpoxvirus, Leporipoxvirus, Molluscipoxvirus, Orthopoxvirus, Parapoxvirus, Suipoxvirus and Yatapoxvirus.
In an unvaccinated population, the Case Fatality Rate (overall fatality rate) for variola major is?
30%
ORF VIRUS INFECTIONS
The orf virus is a species of Parapoxvirus. It causes a disease
in sheep and goats that is prevalent worldwide.
The disease is also called contagious pustular dermatitis or sore mouth infection.
Orf is transmitted to humans by direct contact with an infected animal. It is an occupational disease of sheep and goat handlers.
Infection by orf virus is facilitated by skin trauma. Infection of humans occurs usually as a single lesion on a finger, hand, or forearm but may appear on the face or neck.
Lesions are large nodules, rather painful, with surrounding inflamed skin.
Healing takes several weeks.
Electron microscopy can confirm a parapoxvirus infection, but only nucleic acid testing methods can definitively identify a parapoxvirus as orf virus.
Smallpox showed a spike in incidence in which season/s?
winter/spring
is there a vaccine against Molluscum contagiosum virus?
no
Clinical Findings
The incubation period of variola (smallpox) was 10–14 days.
The onset was usually sudden. One to 5 days of fever and malaise preceded the appearance of the exanthems, which began as macules, then papules, then vesicles, and finally pustules.
These formed crusts that fell off after about 2 weeks, leaving pink scars that faded slowly. In each affected area, the lesions were generally found in the same stage of development (in contrast to chickenpox).
A “Smallpox Recognition Card” prepared by the World Health Organization shows
the typical rash Lesions were most abundant on the face and less so on the trunk. In severe cases, the rash was hemorrhagic. The casefatality rate varied from 5% to 40%. In the less common and more benign variola minor strain (also eradicated), or in vaccinated persons, the mortality rate was under 1%.
What is/are the reservoirs for small pox virus?
Humans are the only reservoir
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vaccination made by which scintist ? when ?
Edward Jenner introduced vaccination with live cowpox virus in 1798.
Modes of Transmission of infection (3)
Air-droplet, contact with infected clothing and bodily fluids, face to face
MONKEYPOX INFECTIONS
Monkeypox virus is a species of Orthopoxvirus.
The clinical features of human monkeypox are similar to those of smallpox, but usually less severe.
lymphadenopathy
Complications are common and often serious.
generally pulmonary distress and secondary bacterial infections.
In unvaccinated patients, the fatality rate-10%. Vaccination with vaccinia either protects against monkeypox or lessens the severity of disease.\
not to be easily transmitted from person to person.
Resistance of poxvirus
Poxviruses are stable and if protected from sunlight may remain viable for months at room temperature. They survive for years in the cold or when freeze dried. They are susceptible to ultraviolet light and other irradiations. They are resistant to 50 percent glycerol and 1 percent phenol but are readily inactivated by formalin and oxidiing disinfectants.
laboratory diagnosis of small pox
Polymerase chain reaction (PCR) tests
electron microscopy
inoculation of vesicular fluid onto the chorioallantoic membrane of chick embryos.
Antibody assays can be used to confirm a diagnosis of poxvirus infection. Antibodies appear after the first week of infection that can be detected by hemagglutination inhibition, neutralization, enzyme-linked immunosorbent assay, radioimmunoassay, or immunofluorescence tests.
Does vaccination or infection give immunity? for how long?
Life long immunity
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differences of variola and vaccinia viruses
The variola virus is the causative agent of smallpox.Variola has a narrow host range (only humans and monkeys). Smallpox used to occur in two distinct clinical varieties.
a. Variola major or classical smallpox: The florid, highly fatal disease typically seen in Asia.
b. Variola minor or alastrim: The mild, nonfatal disease (alastrim) typically seen in Latin America.
Vaccinia virus, the agent used for smallpox vaccination,is a distinct species of Orthopoxvirus. Vaccinia virus is unique in that it is an ‘artificial virus’ and does not occur in nature as such.
cultivation of poxviruses
chick embryo:
•Variola pocks are small, shiny, white convex, non necrotic, non hemmorhagic lesions with ceiling temperature (highest temperature above which pocks are not produced) of 380 C.
•Vaccinia pocks are larger, irregular, flat, greyish, hemorrhagic and Necrotic with ceiling temperature of 410 C.
tissue culture:
Cytopathic effect are produced by Vaccinia in 24 - 48 hours and more slowly by Variola.
Inclusion bodies called Guarnieri bodies can be seen.
animals
Viral DNA replication occurs
in the cytoplasm
Name an infection whose symptoms mimic those of smallpox?
Chickenpox
tell about antigenic structure
All poxviruses share a common nucleoprotein (NP) antigen. Some twenty different antigens have been identified by immunodiffusion. These include the LS antigens (a complex of two antigens, the heat labile L and the heat stable S antigens), agglutinogen, and hemagglutinin, which is responsible for the agglutination of erythrocytes of those fowls which are also agglutinated nonspecifically by tissue lipids.
tell about morphological structure of poxvirus by showing diagram by you
brick-shaped or ellipsoid particles size (300–400) × 230 nm. Their structure is complex and conforms to neither icosahedral nor helical symmetry. The external surface of particles contains ridges. An outer lipoprotein membrane, or envelope, encloses a core and two structures of unknown function called lateral bodies.
linear doublestranded DNA (130–375 kbp).
protein (90%), lipid (5%), and DNA (3%).
Molluscum Contagiosum
MOLLUSCUM CONTAGIOSUM
Molluscum contagiosum is a benign epidermal tumor that occurs only in humans.
member of the Molluscipoxvirus genus.
The virus has not been transmitted to animals and has not been grown in tissue culture.
The lesions of this disease are small, pink, wart-like tumors on the face, arms, back, and buttocks. They are rarely found on the palms, soles, or mucous membranes.
more frequent in children than in adults. It is spread by direct and indirect contact (eg, by barbers, common use of towels, or swimming pools).
The incubation period may extend for up to 6 months. Lesions may itch, leading to autoinoculation. The lesions may persist for up to 2 years but eventually regress spontaneously. The virus is a poor immunogen; about one-third of patients never produce antibodies against it. Second attacks are common.