Pox Disease of Livestock

Cow pox:

• It is a mild contagious skin disease of cattle usually affecting the udder
• It is characterized by eruptions of pustular rash
• When virus transmitted to human via vaccination, it gives immunity against small pox.

Etiology:

• Vaccinia virus of genus orthopox virus
• Family: Poxviridae
• Virus produce hemorrhagic pock lesion on chorio-allantoic membrane of developing chick embryo

Transmission:

• Spread through direct contact with infected udders on cow’s teat
• Through direct contact to infected animals
• Rodent to human transmission
• Via hand of milkers

Pathogenesis:

• Virus enters through direct contact
• First replication occurs in skin or lungs
• Spread to regional LN followed by primary viremia
• Skin lesion appears as erythema and then macule
• Vesicles formation which becomes pustules. Pustules rupture to form scar.

Clinical Findings:

• Temperature is mild in nature
• Anorexia, suspended rumination and depression
• Udder is swollen, hot and sensitive
• Typical pock lesion appears on teat and udder
• Lesion on face of calf
• Swollen lymph nodes, fever
• Vesicles rupture leaving raw ulcerative areas that form scar

Diagnosis:

• Based on clinical signs, characteristic skin lesion
• Isolation of virus

Differential Diagnosis:

1. FMD:

• Lesion in foot and mouth along with udder

2. Pseudo cowpox:

• Scab formation in annular pattern
• Milker’s nodule formation on hand of milker

3. Udder impetigo:

• It is caused by Staphylococcus aureus
• Lesion are discrete, superficial, thin walled and vesicle surrounded by zone of erythema.

Treatment:

• No specific treatment available. Symptomatic treatment is done
• NSAIDs; Meloxicam @0.2 mg/kg, b.wt. IM X OD for 3-5 days
• Broad-spectrum antibiotics; Streptopenicillin
• Application of povidone iodine; himax, salicyclic acid, benzoic acid ointment

Control Measures:

• Strict hygienic measures should be adopted.
• Isolation and segregation of affected cattle
• Disinfection of milking machine
• Hands of milker should be cleaved and washed with antiseptic soap before milking.
• Teat dipping into KMnO₄ solution prior to dipping.

Goat pox:

• It is a malignant disease of goat characterized by fever and appearance of pock lesion.
• All breeds of goat irrespective of age and sex are susceptible.

Etiology:

• Capripox virus

Transmission:

• Through direct contact with affected animals
• Through wound and abrasions
• Virus present in skin papules are transmitted when infected animals rub their body on healthy animals
• Inoculation by biting insect

Pathogenesis:

• Inhalation of virus
• Virus reaches blood circulation via lymphatic duct causing primary viremia
• Virus then localizes to skin and target organs; lungs
• In lungs, lesion produce leading to bronchopneumonia

Clinical Signs:

• Incubation period is of 2-5 days
• Papules are preceded by red macules which is easily seen on white skin. First appear on hairless parts of skin
• Rhinitis, conjunctivitis
• Swollen superficial lymph nodes
• Eyelids are swollen and may completely cover the eyeball
• Mucopurulent ocular and nasal discharge when papules on conjunctiva and external nares become ulcerated.
• Mucus membrane of eyes, nose, lips, vulva and prepuce becomes necrotic
• Ultimately animals die due to laboured breathing as a result of broncho-pneumonia.

PM Findings:

• Pock lesion are seen in all parts of body, eg; lips, cheeks, snout, nostril, face, ear, feet, thigh, abdomen, eyelid, neck, teat, udder
• Papules are usually raised with dark brown centres and changes into vesicle containing cream-colored fluids within 2 days
• Hemorrhage in epidermis and edema of subcutis
• Ballooning degeneration of epithelial cells.
• Coagulative necrosis with pyknotic nuclei and infiltration of neutrophils
• Lung parenchyma shows focal areas of pneumonic changes characterized by congestion, red hepatization and exudation.

Diagnosis:

• On basis of clinical signs and symptoms
• Isolation of virus
• Serum neutralization test
• Gel diffusion test
• FAT

Differential Diagnosis:

• Contagious ecthyma:
  • Lesion are usually in lips
• FMD
  • Lesion mostly confined to mouth and feet.

Treatment and Control:

• Antiseptic or antibiotic ointment are applied.
• Scabs should be painted with povidone-iodine preparation
• Infected animals should be segregated.
• Infected milk shouldnot be fed to kids.

Sheep pox:

• Most serious pox disease of animals characterized by acute febrile condition and generalized development of pock lesion.

Etiology:

• Capri pox virus; DNA virus
• Relatively resistant to environmental temperature and stress

Susceptible Host:

• Sheep are naturally susceptible
• Younger sheep are more susceptible over older ones
• Merino breeds are more prone to disease than indigenous breeds.

Transmission:

• Direct contact with infected animals
• Droplet infection through nasal inhalation
• Through wound and abrasion

Pathogenesis:

• After virus gains entry, there is multiplication of virus with resultant viremia.
• Virus then distributed throughout body system
• Generalized skin lesion appears which turns into vesicles. Vesicles then turn into scab.

Clinical Signs:

Disease appears in 3 clinical forms:

i. Malignant form

ii. Mild (benign) form

iii. Abortive form

1. Malignant form:

• Most common form of disease
• Affected sheep are dull and depressed with high fever; 106-107°F
• Pock lesion on eyelid, lips, nostrils, ears, cheeks, side of foreleg, thigh, scrotum, prepuce, vulva, under tail, chest region and buccal mucosa.
• Lesion begins as macules, then turn into papules which transform into large vesicles. Necrotic changes in the vesicle leads to scab formation.

2. Mild form:

• Eruptions are confined around eye, lips and nose
• Usually noticed in adult sheep

3. Abortive form:

• Ewe may abort and foetus shows pock lesion
• Lactating ewes shows the signs of mastitis due to lesion in udder

PM Findings:

• Characteristic papules, vesicles, pustules, and scabs are noted on cutaneous surface.
• Lesion observed in mucosa of respiratory and alimentary tract especially on trachea.

Diagnosis:

• On the basis of clinical signs and lesion
• Animal inoculation test: lymph of suspected material of affected sheep is inoculated into scarified surface of skin of suspected animal. Inoculated sheep shows high rise of temperature, papules and vesicle formation.
• CFT, Immunodiffusion test
• Gel diffusion test

Treatment and Control:

• Antiseptic or antibiotic ointment are applied.
• Scabs should be painted with povidone-iodine preparation
• Infected animals should be segregated.
• Infected milk shouldnot be fed to lambs
• Vaccination; attenuated or killed vaccine, freeze dried vaccine is administered.

Swine pox:

Syn: Contagious impetigo, Louse borne dermatitis

• It is highly contagious viral disease of pigs characterized by skin eruptions and cutaneous lesion.
• It is mostly seen in young pigs 3-6 weeks old but all age is affected.

Etiology:

• Suipox virus
• Virus can be grown in tissue culture.

Epidemiology:

• Disease is distributed world-wide.
• It is more frequently seen on areas where intensive breeding program has been undertaken.
• It has been recorded as an outbreak in large white pig from Andhra Pradesh, India.
• Cases have been reported in wild boars, suggesting a potential wildlife reservoir for the virus.
• The severity of the disease can vary, with younger pigs experiencing more noticeable symptoms and potentially higher mortality rates.

Transmission:

• Through direct contact with infected pig
• Rubbing of infected skin on healthy pig
• Through vectors; biting lice; Hematopinus suis

Pathogenesis:

• Virus enters through skin abrasion or bites
• Replication of virus in epidermal cells
• Formation of vesicles
• Vesicles ruptures and turns into scab which heal or drop off

Clinical Findings:

• Incubation period; 1 week
• Affected pigs are dull and depressed with dejected appearance.
• High fever; 105-107°F with nasal and ocular discharge
• Pock lesion appears over snouts, eyelids, inner aspect of thigh, abdomen
• Lesion are vesicular at first which turns to papules. Red brown scab develops on skin within 8-11 days.

PM Findings:

• Multifocal, popular to pustular lesion are seen on ventral abdomen, inner thighs, and perioral/ocular region.
• Ballooning degeneration of epidermal cells.
• Fluid accumulation within abdominal cavity
• Eosinophilic inclusion bodies are found within cytoplasm of keratinocytes.

Diagnosis:

• Based on clinical findings
• Based on PM findings
• Isolation and identification of virus

Differential Diagnosis:

• Mites infestation
• Scabies; Itching is cardinal sign
• Ringworm: Lesion are crusty in nature

Treatment:

• There is no specific treatment for disease.
• It is better to use Butox @3-5 ml/litre of water
• Ivermectin @1ml/50 kg, b.wt., SC, SD

Control Measures:

• Vaccination is not attempted.
• Recovery from infection renders the pig immune to disease.
• Lice should be controlled in pigs. Acaricides like lindane, trichlorophan, amitraz, etc may be applied.
• Animals should be cleaned and disinfected to keep the premises louse free.
• Isolation of affected animals from herd.
• Regular inspection of skin of newly purchased pigs for signs of pox lesions.