Poxviridae

PoxviridaeBy: Qasim MashoodDVM (2010-2015)

The family “Poxviridae” comprised of two subfamilies….

1. Chordopoxvirinae2. Entomopoxvirinae

Classification

morphology

Virions are complex

Core –Dumbbell shaped, Contains viral DNA, viral proteins

Lateral bodies – unknown nature

+/ - Envelope

Genome is linear and double stranded

Encodes all transcription and replication enzymes needed for viral genome

Largest and most complex of all viruses Brick shaped or ovoid 250 x 200 x 200 nm in size

Occurs in the cytoplasm

Following the release of the viral core into the cytoplasm, the following occur:

Adsorption and penetration via endocytosis for non-enveloped viruses Fusion with the plasma membrane are used with enveloped viruses

Uncoating – 2 step process Host cell enzymes partially uncoat the viral particle, exposing some viral DNA and polymerase

Early mRNA are transcribed resulting in several polypeptides, including an uncoating protein which completes the uncoating of the core.

DNA replication using enzyme pools

Replication

“Late” mRNA codes for structural proteins and proteins to switch off “early” mRNA activity

Especially to block uncoating proteins in order to protect the progeny virions that are being assembled

Following assembly, mature enveloped virions are released by budding or by exocytosis

Naked virions are released by cell lysis

Most poxviruses are naked Both enveloped and naked are infectious.

Poxviruses are resistant to ambient temperatures and can survive for many months or years in dried scabs

Poxviruses are transmitted between animals by skin abrasions, aerosol and mechanical transmission by arthropods

Pathogenesis and Immunity Highly epitheliotropic – causing cutaneous and systemic disease in birds and wild and domestic

mammals Many are host specific, but orthopoxviruses infect a wide range of hosts After cutaneous introduction or inhalation – the virus gains access to the systemic circulation

through the lymphatics. Multiplication of the virus at the skin wound may lead to direct access to the blood and primary

viremia. Secondary viremia disseminates the virus back to the skin and other organs.

Poxviridae – Epidemiology, Pathogenesis and Immunity

Cowpox Camelpox Monkey pox Mouse pox Sheep and goat pox Lumpy skin disease Yabapox and tanapox Fowl pox ORF Pseudocow pox Bovine papular stomatits

Diseases

The Cowpox Virus

Nomenclature:

Family: PoxviradaeSubfamily:ChordopoxvirinaeGenus:OrthopoxvirusesSpecies: Cowpox virus

Epidemiology

Cowpox virus has been found only in Europe and in adjacent parts of the former Soviet Union and has traditionally occurred via contact with infected teats of milking cows

• The reservoir hosts of cowpox virus are rodents from which it can spread occasionally to cats, cows, humans, and zoo animals.

• Cowpox is a zoonosis, meaning it is transmitted from a vertabrate animal to a human.

Currently, infection with cowpox virus is more commonly seen among domestic cats, from which it is occasionally transmitted to humans.

In human produces localized,pustular leisions that are painful.

virus infection in domestic cats is often a more severe disease than in cattle or humans.

Clinical findings

Lesion are on head or a forelimb in cat. In cattle Lesions on the teats the contagious parts of the udder of

cows and is spread through herds by the process ofmilking.

Clinical findings ….

Camelpox virus is very host Specific and does not infect other animals. Severe generalized Skin lesions Case fatality 25%

Camel pox

Transmission is by either direct contact between infected and susceptible animals or

indirect infection via a contaminated environment. The role of insects in transmission has been suspected because the disease is often observed after rainfall.

Transmission

Zoonotic importance The monkeypox virus is thought to be transmitted to

people in bites from animals, in aerosols during close contact, or by direct contact with lesions, blood or body fluids

monkeypox virus or its nucleic acids have been found in skin lesions, urine, feces, and oral, nasal and conjunctival exudates.

This virus can be spread on fomites.

Monkey pox

In humans, monkeypox resembles smallpox. Symptoms Milder the lymph nodes are usually enlarged. initial symptoms are flu–like Fever chills headache backache, Fatigue lymphadenopathy (most often affecting the submandibular, cervical and/or inguinal

lymph nodes)

Infections in Humans

Species known to be susceptible include Old and New World monkeys and apes

a variety of rodents rhesus macaques cynomolgus monkeys, baboons

Animal host range

EPIDEMIOLOGY • Morbidity rate: Endemic areas 70–90% • Mortality rate: Endemic areas 5–10%, although can approach

100% in imported animals Hosts • All breeds of domestic and wild sheep and goats, although most

strains cause more severe clinical disease in only one species • Native breeds in endemic areas are far less susceptible than breeds

of European or Australian origin – morbidity and mortality may approach 100%

Sheep and goat pox

rise in rectal temperature to above 40°C macules develop in 2-5 days small circumscribed areas of hyperaemia papules develop from macules – hard swellings of

between 0.5 and 1 cm in diameter . Papules may be covered by fluid-filled vesicles,

Clinical signs

• Skin lesions: congestion, haemorrhage, oedema, vasculitis necrosis. • Lymph nodes draining infected areas: enlargement (up to eight times normal size) lymphoid proliferation

Lesions

• Pox lesions: on mucous membranes of the eyes, mouth, nose, pharynx, epiglottis, trachea, on the rumenal and abomasal mucosae, and on the muzzle, nares, in the vulva, prepuce, testicles, udder, and teats. Lesions may coalesce in severe cases

• Lung lesions: severe and extensive pox lesions, focal and uniformly distributed throughout the lungs; congestion, oedema, focal areas of proliferation with necrosis,

lobular atelectasis. Enlargement, congestion, oedema and haemorrhages of mediastinal ymph nodes

Sheep and goat pox

Family Poxviridae Genus Capripoxvirus

Closely related to sheep and goat pox

Center for Food Security and Public Health, Iowa State University, 2011

Lumpy Skin Disease Virus

Morbidity Widely variable 3% to 85%

Mortality Usually low 1% to 3% 20% to 85% in some outbreaks

Center for Food Security and Public Health, Iowa State University, 2011

Morbidity/ Mortality

Primary route: biting insects Minor route: direct contact

Cutaneous lesions, saliva, nasal discharge, milk, semen, muscles

No carrier state Spread related to movement of cattle

Center for Food Security and Public Health, Iowa State University, 2011

Animal Transmission

Incubation period 2 to 5 weeks

Inapparent to severe infection Young calves most susceptible

Nodule development Decreased milk yield

Center for Food Security and Public Health, Iowa State University, 2011

Clinical Signs

Clinical Signs

Raised, circular, firm, coalescing nodules Common on head, neck, udder,

perineum, legs Secondary bacterial infections Rhinitis, conjunctivitis Lameness Abortion and sterility

Center for Food Security and Public Health, Iowa State University, 2011

Myxoamtosis

visible by lumps (myxomata) puffiness around the head and

genitals. acute conjunctivitis possibly blindness The rabbits become listless, lose appetite fever. Secondary bacterial infections In typical cases where the rabbit has

no resistance death may take place rapidly, often in as little as 48 hours. Death usually occurs within 14 days

Fowl pox

Fowl pox occurs mainly in two forms:

Most commonly it is a cutaneous infection of epithelial tissues of the non-feathered portions of the skin characterized by the formation of wart-like nodules on the comb, wattles, oral comissures, eyelids, feet and legs

alternatively it appears as an infection of the mucus membranes of the mouth, nose and eyes giving rise to diphtheritic pseudo-membranes in the mouth,pharynx and larynx.

Strains: There are 4 main strains of the virus, namely; fowl pox, turkey pox, pigeon pox

and canary pox. infection by biting Involvement of the skin around the naries may causenasal discharge, and lesions on the eyelids can causeexcessive lacrimation and predispose poultry to secondarybacterial infections. In uncomplicated cases, healing occurs within 3 weeks

Orf is an exanthemous disease caused by a parapox virus and occurring primarily in sheep and goats

Symptoms papules and pustules on the lips and muzzle less commonly in the mouth of young lambs and on the eyelids, feet, and

teats of ewes. The lesions progress to thick crusts which may bleed. Orf in the mouths

of lambs may prevent suckling and cause weight loss, infect the udder of the mother ewe, mastitis .Occasionally the infection

can be extensive and persistent if the animal does not produce an immune response

ORF(rough)contagious pustular dermatitis

the course of the disease (1-4 wk), the scabs drop off and the tissues heal without scarring.

During active stages of infection, more severely affected lambs fail to eat normally and lose condition.

Extensive lesions on the feet lead to lameness.

contagious pustular dermatitis

Bovine papular stomatitis is usually of little clinical importance occurs worldwide, All ages, although the incidence is higher in animals less than 2 years of age. The development of lesions

muzzle, margins of the lips, and the buccal mucosa is

similar to that of pseudocowpox Immunity is of short duration Demonstration by electron microscopy of the characteristicparapoxvirus virions in lesion scrapings is used for diagnosis.

Bovine papular stomatitis

Pseudocowpox occurs as a common endemic infection Chronic infection in many milking herds and occasionally occurs in beef herds. The lesions of pseudocowpox are characterized by "ring" or

"horseshoe" scabs, the latter being pathognomonic for the disease .

Infection is transmitted by cross-suckling of calves, improperly disinfected teat clusters of milking machines, and probably by the mechanical transfer of virus by flies. Control;Attention to hygiene in the milking

Psudeopox