Vesicular Stomatitis Jen Gold DVM Diplomate ACVIM, ACVECC Chaparral Veterinary Medical Center May 8, 2015

What is Vesicular Stomatitis? It’s a virus Member of the Rhabdoviridae Two types of viruses in the genera – Lyssavirus Rabies – Vesiculovirus VSV

Virus versus Bacteria Viral Smaller than bacteria Require living hosts to survive and multiply – Plants – Animals – Humans Otherwise they can’t survive Invades cells and takes over the cell Does not respond to antibiotics Bacterial Single cell organism Thrive in lots of environments – Cold – Heat – Intestines of mammals Respond to treatment with antimicrobials/antibiotics Caveat-must be on appropriate antimicrobial

Vesiculovirus Bullet shaped virus

Two Serotypes of Interest Vesicularstomatitis virus-New Jersey (VSV-NJ) Vesicularstomatitis virus-Indiana (VSV-IN) These viruses are similar in size Create different neutralizing antibodies Distinguished by either serotype Indiana or serotype New Jersey

Epidemiology First reported in United States in 1916 Most likely was occurring during Civil war In 1926 distinguished the two serovars. 1990’s 3 outbreaks occurred in the Southwest

1995 Outbreak Index case confirmed in Las Cruces, New Mexico 1162 investigations occurred 42 states VS confirmed in AZ, CO, NM, TX UT,WY 78% of premises had horses 22% of premises had cattle, one had a positive llama All cases were serotype New Jersey

1997 Outbreak Index case for outbreak in Yavapai County, AZ Outbreak had 689 investigations for suspect VS cases in 40 states 380 premises housed positive VS animals Four states involved: AZ, CO, NM, UT

1998 Outbreak Index case in Tularosa, New Mexico in a horse 130 investigations were positive for VS Four states affected, AZ, TX, NM, CO 99% of cases were equine 1% of cases were cattle Serotype VSV-IN

Outbreaks : TX, NM, CO; 470 positives 2005: Nine states; 786 positives 2006: WY; 29 positives 2009: TX, NM; 7 positives 2010: AZ; 4 positives 2012: CO, NM; 290 positives 2014: TX, CO NE 433 positives

Economic Cost 1928: California dairy herds – $97 to 202 lost per head 1995: New Mexico beef herd – $53 lost per head Losses due to: – Increased culling, increased mortality – Reduced milk production – Labor, medicine, veterinary costs

Vesicular Stomatitis Virus Morbidity – Range: 5 to 90% – Most animals seroconvert Mortality – Higher in adults – Death rare in cattle and horses

Vesicular Stomatitis Virus Disease of Western Hemisphere Only one area of endemic disease is in USA Other areas – South American – Central America – Mexico

Transmission Considered arboviruses WHAT IS AN ARBOVIRUS? Any group of viruses that are transmitted by mosquitos, ticks or other arthopods Other examples: Yellow Fever, West Nile, Dengue Fever

Arthropod Vector Transmission Outbreaks in Southwest Typically occur in late spring early summer Continue through late fall Index cases for outbreaks typically in Arizona and New Mexico

Transmission Most outbreaks suggestive of an association with arthropod abundance New cases occur with warmer weather Insect hatches

Types of Vectors-Sand Fly

Horse Fly

Deer Fly

Mosquito

Biting Midge

House Fly

Eye Gnats

Black Fly

Stable Fly

Vectors Evidence shows most arthropod vectors are likely Sand flies Black flies

Transport of Infected Animals Many outbreaks have occurred due to transport of infected animals Example 1983 outbreak: Cases of cattle in Idaho travelled to California 1995 outbreak: Horse in New Mexico transported to Texas

Direct Contact Transmission Experiments pigs Pigs inoculated with VSV-NJ Sero-negative pigs came in contact with infected pigs Transmission occurred when pigs had visible lesions Sero-negative pigs shed virus as early as 1 day after contact with infected pigs

Reservoirs Multiple species have been found to have antibodies to VSV Deer mice may be a reservoir species in the southwest

Risk Factors Animals with access to shelter or barn have reduced risk Increased insect populations Residence within ¼ mile to running water

Pathogenesis Virus attaches to cell surface Enters cells, transcription of virus particles

Pathogenesis Much remains unclear Disease has been around for a long time

Clinical signs Typically follow a 3-7 days incubation period Initially animals have a fever Drooling is then seen in horses and cattle

Clinical Signs Lesions are raised blanched and fluid filled vesicles Erosions occur next Occur on muzzle, tongue, cheek, coronary bands

Clinical signs

Diagnosis WHY IS THIS SUCH A BIG DEAL????? Rule out other diseases Biggest Reason-Foreign Animal Disease Foot and Mouth Other Rule outs Cantharidin toxicosis, Sunburn

Center for Food Security and Public Health, Iowa State University, 2011 Foot & Mouth DiseaseVesicular Stomatitis Swine Vesicular Disease Vesicular Exanthema of Swine Clinical Signs by Species All vesicular diseases produce a fever with vesicles that progress to erosions in the mouth, nares, muzzle, teats, and feet Cattle Oral & hoof lesions, salivation, drooling, lameness, abortions, death in young animals, "panters"; Disease Indicators Vesicles in oral cavity, mammary glands, coronary bands, interdigital space Not affected Pigs Severe hoof lesions, hoof sloughing, snout vesicles, less severe oral lesions: Amplifying Hosts Same as cattle Severe signs in animals housed on concrete; lameness, salivation, neurological signs, younger more severe Deeper lesions with granulation tissue formation on the feet Sheep & Goats Mild signs if any; Maintenance Hosts Rarely show signsNot affected Horses, Donkeys, Mules Not affected Most severe with oral and coronary band vesicles, drooling, rub mouths on objects, lameness Not affected

Diagnosis Three approaches to diagnosis – Antibody detection – Virus detection via viral isolation – Detection of virus genetic material

Diagnosis Viral neutralization considered gold standard Animals with antibodies > 1:40 dilution are considered positive cELISA test for antibodies is also used and is most frequently the test of choice in the US Once cELISA is positive, then confirmed by Viral neutralization or complement fixation

Diagnosis Other tests Viral isolation-vesicle fluid, swabs of lesions can find virus particles Polymerase chain reaction (PCR) can detect serotype VSV-NJ rtPCR can distinguish the two serotypes

Diagnosis Practitioner notifies state veterinarian State veterinarian makes the decision to quarantine Quarantined premises are eligible for release days after the onset of lesions in the last affected animal on the premises

Therapy VS typically short lived and self limiting No specific treatment indicated Most horses recover in 7-14 days Frequent rinsing of lesions with mild antiseptic solutions or application of topical antibiotics may help prevent secondary infections

Therapy Softening of grain or pellets with water may help chewing when oral lesions are present Dehydration from not drinking may require fluid therapy

BIOSECURITY Wear disposable gloves when working with affected horses Eye protection is also indicated when examining, handling affected horses

BIOSECURITY CAUTION!! ZOONOTIC – HUMANS CAN GET VESICULAR STOMATITIS – CAUSES FLU LIKE SYMPTOMS Restriction of movement of affected horses and herd mates essential for control of spread of the virus Quarantine of premises

Disinfection Easily inactivated – Area must be free of organic matter – Contact time of at least 10 minutes Disinfectants – Phenolic, halogen-based disinfectants – Soda ash, 2% iodophores – Chlorine dioxide, 1% chlorine bleach – 1% cresylic acid – Quaternary ammonium

Prevention Currently NO VACCINE licensed in USA

Prevention Protection from Insect Exposure Housing horses indoors during the evening Regular application of insect repellents to the horse including inner surface of ears – Where black flies like to feed Decrease any standing water Feed through fly control

New Arrivals to Facility or Event Certificate of veterinary inspection with statement related to potential exposure to VS Inspection of newly arriving horses including oral examination to detect ulcers or vesicles Wear disposable gloves, wash hands in between horses, change gloves between horses

Additional Resources World Organization for Animal Health (OIE) – U.S. Department of Agriculture (USDA) – Center for Food Security and Public Health – USAHA Foreign Animal Diseases (“The Gray Book”) – Center for Food Security and Public Health, Iowa State University, 2011