Veterinary medicine
Prof. D. Basima AlbadraniVESICULAR STOMATITIS
ETIOLOGYThe causative virus is a vesiculovirus (family Rhabdoviridae)
There are two antigenically distinct serotypes of the virus: vesicular stomatitis New Jersey (VS-NJ) and vesicular stomatitis Indiana (VS-IN).
There are three subtypes of the vesicular stomatitis Indiana] fort Lupton, Alagaos (Brazil) and Cocal (Trinidad) .
The New Jersey serotype is the most virulent and most common.
the virus is much less resistant to environmental influences than the virus of FMD and it is more readily destroyed by boiling and use of disinfectants.
The disease is of major importance because it is indistinguishable from foot and mouth disease, and it can cause disease in humans.
EPIDEMI OLOGY
Disease of cattle and horses , donkeys, deer and occasionally pigs in the western hemisphere.
Host occurrence : Cattle, horses, and donkeys are most susceptible but infection can also occur in pigs, camelids and humans and possibly sheep and goats.
A major outbreak occurred in military horses in the United States
during the 1914-1918 war but in recent years, in addition to clinical disease in horses, it has come to assume greater importance in cattle and pig herds.
Calves are much more resistant to infection than adult cattle.
Many species of wildlife are seropositive such as bats, deer, monkeys
Humans are susceptible – infection causes an influenza-like disease - and the development of high antibody titers in humans often ccompanies outbreaks in cattle.
Clustered outbreaks occur in summer and autumn.
Vector (Sandflies and blackflies ), direct and mediate transmission
In endemic areas, outbreaks are seasonal, often associated with the transitions between rainy and dry seasons.
The morbidity rate varies considerably; 5-10% is usual but in dairy herds it may be as high as 80%.
There is usually no mortality in dairy herds but overall case-fatality rates ranging from 0-15% are recorded for beef herds.
Morbidity in horse herds is high but there is no mortality.
Outbreaks in an area are usually not extensive but the disease closely resembles FMD and has achieved considerable importance for this reason.
The saliva and vesicular fluid from clinically affected animals are highly infective but infectivity diminishes rapidly and may be lost within 1 week after the vesicles rupture. However, convalescent cattle have been suspect as perpetuating disease and spreading it with movement to other herds.
Vesicular stomatitis virus has been isolated from convalescent cattle 38 d after the disappearance of clinical signs and disease can recur in convalescent cattle.
Domestic animals appear to be deadend hosts in which the virus does not persist and does not return to its natural cycle.
Method of transmission
biological transmission by blood-feeding insects, The virus can be biologically transmitted by black flies (Simulium vittatum)
and mechanically by Culicoides spp.
flies (Musca domestica, and M. autumnalis) and eye gnats (Hippelates spp.), sandfly (Lutzomyia shannoni), which may be a biological vector in that region from feral pigs acting as the amplifying host.
Other suspect vectors for vesicular stomatitis include L. trapidoi and mosquitoes,
Mediate or immediate contagion occurs by contact or ingestion of contaminated materials, especially in large intensive dairies where there is much communal use of water and feed troughs, It also occurs by the ingestion of contaminated pasture.
In fed cattle the use of coarse roughage or hard pellets encourages the spread of the infection, Spread within dairy herds also appears to be aided by milking procedures.
The importation of embryos from infected areas is considered a minimal risk for introduction of infection.
Risk factors
Host factors
Environ mental factors
There is a marked seasonal incidence of the disease, cases decreasing sharply with the onset of cold weather. The disease is enzootic in low-lying coastal countries with tropical climates, heavy rainfall and high insect populations during the summer.
Pathogen risk factors
Economic importance
Most cases of vesicular stomatitis recover in a few days. The losses on large dairy farms due to disruption of continuity of milk supplies may cause severe financial loss.
There is also much inconvenience and temporary inability to feed,
There are also losses associated with quarantine such as loss of market opportunities and pasture damage from overgrazing of pastures used for quarantine.
Other economic effects result from the cancellation of animal events such as fairs and the cost of loss of international markets.
PATHOGENESIS
. Local infection of the mucous membrane of the mouth and the skin around the mouth and coronets is followed by the development of vesicles on the lips, muzzle, tongue, and also on the teats and
interdigital clefts.
CLINICAL FIN DINGS
Cattle
In cattle after a short incubation period of 3-15 d, t
here is a sudden appearance of mild fever and the development of vesicles on the dorsum of the tongue, dental pad, lips and the buccal mucosa.
The vesicles rupture quickly and the resultant irritation causes profuse, ropy salivation and anorexia.
Confusion often arises in field outbreaks of the disease because of failure to find vesicles. In some outbreaks with thousands of cattle affected, vesicles have been almost completely absent.
They are most likely to be found on the cheeks and tongue where soft tissues are abraded by the teeth.
At other sites there is an Viral diseases characterized by alimentary tract signs erosive, necrotic lesion.
In milking cows there is a marked decrease in milk yield.
Lesions on the feet and udder occur only rarely except in milking cows where teat lesions may be extensive and lead to the development of mastitis. Recovery is rapid, affected animals are clinically normal in 3-10 d, and secondary complications are relatively rare.
Horses
In horses, the signs are broadly similar. There is fever, depression, inappetence, drooling of saliva and affected horses may rub their lips on troughs and jaw champ. Vesicles coalesce and rupture with detachment
of the epithelium and the formationof shallow ulcers. The period of fever and vesicles is short lived. Not infrequently the lesions seen are limited to the dorsum of the tongue or the lips and are in the coalescing ulcer stage. Other less common sites include the udder of the mare and the prepuce of males. Lesions may occur at the coronary band and lead to lameness
and deformity of the hoof wall.
CLINICAL PATHOLOGY
. Diagnostic confirmation Virus isolation or polymerase chain reaction,
serology with rising titers.
Differential diagnosis
Because of its case-for-case similarity to FMD, prompt and accurate diagnosis of the disease is essential. In most countries the disease is notifiable.
All species
• FMD and other vesicular diseases.
Cattle
• Bovine virus diarrhea
• Bovine malignant catarrh
• Pseudocowpox.
H orses
• Blister beetle toxicosis
• Bullous phemigoid
• Phenylbutazone toxicity
• Grass seed awns.
TREATMENT is seldom undertaken but nonsteroidal anti-inflammatories may contribute to the com fort of the animal and
the rapidity of recovery.
CONTROL
Office of International Epizootics OIE List-A disease.
Hygienic and quarantine precautions to contain the infection within a herd
A DNA vaccine