Vesicular and ulcerative diseases_060325.3_w20

• Vesicular and ulcerative diseases affect animal systems.
• Vesicles in livestock feature blister-like lesions in the mouth and feet.
• Companion animals manifest similar skin lesions.
• Diagnose vesicle diseases by verifying the presence of vesicles.
• It is important to identify current or recent vesicles.

Key Definitions

• Vesicle: A small, circumscribed elevation of the epidermis filled with clear fluid, measuring less than 0.5 cm in diameter.
• Bulla: A localized collection of fluid exceeding 0.5 cm in diameter, larger than a vesicle.
• Erosion: The loss of epithelial layers.
• Ulcer: Loss of epithelium with damage extending through and below the basement membrane.
• Pox: Raised proliferative or inflamed epithelial lesion.
• Alopecia: Hair loss, which can be a secondary condition.
• Erythema: Diffuse or localized skin redness that disappears with diascopy.
• Macule: Flat, circumscribed skin discoloration less than 1 cm in diameter without surface elevation or depression, and a large macule is known as a patch
• Nodule: Circumscribed solid elevation greater than 1 cm extending into the dermis, with large nodules being refered to as masses
• Papule: Small solid elevation of the skin up to 1 cm in diameter, feels solid and is due to the infiltration of inflammatory cells, fluid or foreign material (calcium), with oedema and epidermal hyperplasia
• Patch: Localised flat change in skin pigmentation larger than 1 cm in diameter.
• Plaque: Flat topped elevation of the skin >0.5 cm formed by a coalition of papules
• Pustule: Small circumscribed elevation of the epidermis filled with purulent material
• Wheal: Sharply circumscribed raised lesion consisting of oedema, it usually appears and disappears within minutes to hours

Epithelium

• Normal epithelium is stratified squamous with keratinisation.
• The stratum spinosum layer features spiny processes and intercellular bridges attached by desmosomes.
• The stratum basale lies above the basement membrane.
• Tonofilament formation leads to keratin production.
• In vesicles, stratum spinosum cells experience death, known as acantholysis.
• Clear fluid collects between overlying layers and the stratum basale forming a vesicle.
• The fluid serves as a key diagnostic marker.
• Vesicles typically have a thin overlying layer that ruptures quickly.
• Ulceration presents as damage and necrosis that extends through the basement membrane.
• Ulceration elicits a strong inflammatory reaction.
• Healing occurs through fibroplasia.
• Scarring may result from secondary healing.
• Causes: Infections, burns, and chemical injuries.

Examples of Vesicular Disease

• Foot and Mouth Disease (FMD).
• Swine Vesicular Disease (SVD).
• Vesicular Stomatitis (VS).
• Other causes include chemical injuries, physical injuries, photosensitisation, and autoimmune conditions.
• FMD only affects cloven hoofed animals like pigs, cattle, sheep, and deer, and it is worldwide.
• SVD primarily affects pigs, mainly in the EU (Italy).
• VS affects cattle and horses, rarely pigs, occurring due to insect transmission seasonally in the USA.
• Small animals can also be affected.

Foot and Mouth Disease Virus (FMDV)

• Veterinary surgeons play a vital role in identifying and controlling these diseases within a legislative framework.
• FMD, SVD, and VS are notifiable diseases
• Blue Tongue (BT) and related diseases cause ulcers in the mouth, but not vesicles.
• FMDV belongs to the Picornaviridae family.
• The picornaviridae family are among the smallest RNA-containing viruses known.
• They are significant pathogens for animals and humans.
• Virions have a spherical, non-enveloped capsid.
• The genome comprises a single positive-sense mRNA of approximately 7.5 Kb.
• The polyprotein is flanked by Non-Coding Regions (NCRs), also known as UTR-NTR.
• The icosahedral capsid lacks an envelope, and the shell protects the nucleic acid.
• The capsid demonstrates 2, 3, and 5-fold axes of symmetry with 20 faces.

Epidemiology of FMDV

• It spreads rapidly among even-toed ungulates.
• Cattle, sheep, goats, pigs, as well as buffalo, deer, antelope, and elephants can contract is,
• As a List A disease, it is notifiable and causes significant losses.
• A large amount of virus is shed during the first 24 hours, prior to the onset of clinical signs.

Clinical Signs of FMDV

• Incubation: two to 14 days
• Infected cattle display fever and reduced milk production.
• Profuse salivation drooling, smacking lips, and oral vesicles rupture, often accompanied by lameness foot lesions.
• Pigs may experience foot lesions and lameness.
• Sheep, goats, wild ruminants, and humans typically have only mild symptoms.

FMDV Survival Factors

• FMDV can survive refrigerated for months.
• It becomes progressively inactivated at temperatures above 50°C.
• FMDV becomes inactivated at pH levels below 6.0 or above 9.0.
• Muscle destruction occurs at pH levels of below 6.0 post rigor mortis. However, it can survive in neutral pH in lymph nodes and bone marrow.
• FMDV is resistant to iodophores, quaternary ammonium compounds, hypochlorite, and phenols, especially with organic matter.
• It can persist for about a month in contaminated fodder and environment (3 days in summer, 30 days in winter), six months in slurry, and two weeks in dried feces.
• UV light and desiccation kill the virus.

Diagnosing FMDV

• Diagnosing FMDV is similar to other vesicular diseases.
• It requires laboratory testing to confirm.
• Tests include detecting FMDV antigen in tissue or fluid, using pharyngeal fluid from convalescing animals.
• ELISA is the preferred diagnostic test, although PCR can also be used.

FMDV Control Measures

• FMD is a notifiable disease in FMD-free countries,.
• in contact animals are culled in.
• Movement is restricted
• Ring vaccination is used, but animals carry the virus.
• In endemic countries, vaccination aims to protect the animals and continue life as normal.

Swine Vesicular Disease.

• This is similar to other vesicular viruses.
• Taxonomic family: Picornaviridae.
• Taxonomic class: Enterovirus.
• Is non-enveloped.
• It contains +RNA.
• Pigs are natural hosts
• The disease is notifiable.
• Mild in nature.
• Associated with a febrile illness.
• Results in lesions on the coronary bands and, less commonly, on the snout, lips, and tongue.
• Causes lameness.
• Diagnosis needs ELISA in order to be distinguished from other vesicular diseases.
• Alternatively, the virus can be isolated.
• There is a vaccine but again not suitable in countries where it is not endemic.
• Occurs regularly in southern EU and occasionally appears in the UK.
• It is milder than FMD, but almost identical clinically.

Vesicular Stomatitis Virus

• Order taxonomic rank: -virales.
• Taxonomic Class: Mononegavirales.
• Includes single stranded viruses.
• Is (-)sense.
• Non-segmented genome.
• Enveloped.
• Family taxonomic rank: -viridae.
• Taxonomic family: Rabdoviridae.
• Can result in bullet shaped viruses.
• In the genus taxonomic rank is virus.
• Is Vesiculovirus.
• All cross react.
• Similar genome sequence.
• Examples include the species: VSV.
• It is Vesiculovirus.
• Is bullet shaped.
• Linear RNA genome negative
• The virus is approximately 11KB.
• It is enveloped.

VSV Epidemiology

• Causes endemic in Central America and South America and USA
• It affects mainly horses and cattle.
• Outbreaks every 2/3 years in tropical regions every 10 years in temperate regions
• Results in transmission via direct contact and insect
• The virus can be isolated from blackflies, mosquitoes, sand & houseflies.

VSV Pathogenesis

• Enters through abrasions or via insects
• Vesicles develop at site of infection.
• Spread occurs locally by extension of primary lesion.
• Transfer of the virus occurs to secondary regions but is unclear how

VSV Clinical Signs

• Results in an incubation period: for up to 5 days
• The patient becomes febrile (high temperature)
• Vesicles, blisters on oral mucus membrane, lots of saliva
• Lameness in pigs, mastitis in cows with teat lesions, all normally heal
• Problem is losses to production and culling, and other disease control measures (as seen in FMD)
• Animals develop antibodies but immunity may be limited, strains may not cross protect
• In pigs, different from FMDV in that does not spread to cattle and only a small proportion are infected

VSV: Diagnosis, treatment and control

• Isolation of virus in cell culture or detection of Antigen by ELISA or Complement Fixation Test
• EM in specimens or tissues
• Test must be quick- as levels of IgM do not persist
• Specific treatment NONE, to minimize secondary infection such as insect proof buildings, avoidance of insects
• Vaccines available but generally not used.
• Movement restrictions and quarantine for 30 days post last case.
• Papilloma viruses cause warts on calves and cows teats
• Bluetongue causes oral lesions in sheep.

Related Zoonotic diseases:

• Pseudocowpox
• Orf
• Bovine papular stomatitis etc

Other related conditions:

• Ulcerative diseases
• Photosensitisation – 1° and 2°
• Plant toxins - can cause direct blisters

Mucosal Disease

• Mucosal disease is a particular manifestation of the disease complex caused by a pestivirus BVDV in cattle persistently infected in utero

Malignant Catarrhal Fever

• It is caused by herpes virus.
• It is commonly seen in the UK,
• Is seen in cattle infected with an ovine herpes virus.

Bovine Papular Stomatitis

• Bovine Papular Stomatitis (BPS) is caused by a parapoxvirus and is similar to pseudocowpox and orf.

Vesicular disease in small animals:

• The main 2 viruses: feline calicivirus and Feline Herpesvirus
• Caliciviridae, vesivirus.
• +RNA.
• Small nonenveloped.
• Herpesviridae, Alphaherpesviridae subfamily.
• Feline Herpes Virus 1.
• Ds DNA, large, enveloped.
• Vesicles in dogs can result in small multiple vesicles, a condition also known as pemphigus
• May be present on skin and/or at oral-cutaneous and/or ano-cutaneous junctions.
• Results in an autoimmune disease.
• Variety of other autoimmune diseases of skin

Other causes of vesicles:

• Plant toxins.

• Photosensitisation.

• Trauma which may include thermal and chemical damage to the skin.

• Key veterinary role is to identify a vesicle in livestock with blister-like lesions around and in the mouth and on the fact.