Exotic Diseases

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Species Infected

cattle, horses, pigs, deer

rare in sheep, goats

can cause influenza-like symptoms in humans

Clinical Signs

• essentially the same as foot and mouth disease
• short incubation followed by a mild fever
• vesicle development accompanies diffuse ropey salivation and anorexia
• feet lesions and lameness not a feature in cattle but is more frequent in pigs
• sudden drying off
• rapid healing within a week of lesions first appearing
• low morbidity 5-10%, but in dairy herds may be 80%
• disease can be more severe in South America with occasional mortality occurring

Lesions

• during outbreak these may be site-specific on one property (mouth or feet) and on another property affect a different site
• all sites may be involved
• vesicle development in cattle frequently not evident or does not occur
• erosions seen instead
• if vesicles do develop they do so 24-48 hr post-infection
• rapidly coalesce and rupture
• pigs - vesicles last longer on snout as epithelium tougher
• rapid repair within a week

Pathogenesis

• not well understood
• thought that skin/mucosal abrasions or damage necessary for infection to occur
• no carrier state known at present

Aetiology

Vesiculovirus (Rhabdoviridae)

2 types

• New Jersey
• Indiana - 3 subtypes
• both virus types are antigenically and epidemiologically distinct
• resistant to environmental effects but infectivity low so outbreaks can be controlled

Epidemiology

• well recorded but difficult to explain
• endemic in tropics with cyclic epidemics in temperate areas
• latent infections activated by stress
• wild animal reservoir a possibility
• some features such as seasonality suggest insects (mosquitos, phlebotomus flies) may be either mechanical or biological vectors
• it may be a catholic virus, that is, one that can infect plants, insects and vertebrates

Differential Diagnoses

• as for foot and mouth disease
• care: vesicles may not be observed