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Biosecurity, or containment of animals exhibiting infectious diseases so these do not spread further in the community, is an important aspect of breeding, showing, racing and boarding stables. A number of guidelines have been issued by the AAEP (American Association of Equine Practitioners) with regards to biosecurity measures to undertake depending on the pathogen of concern. Attached is a copy of these guidelines. Biosecurity On Your Farm Biosecurity involves reducing the risk of exposure of infectious diseases to horses in close contact with each other. Vaccination helps reduce the risk of exposure to infectious diseases. However, any new individuals introduced to the farm should undergo a quarantine of a minimum of 4 weeks prior to being introduced to the farm residents. In addition, horses that travel or show frequently should be quarantined upon return from shows as well. The infectious diseases for which there is a vaccine that may be of concern to your horses are: · Influenza · Herpesvirus · West Nile virus · EquineEastern Encephalitis virus · Strangles · Rabies · Potomac Horse Fever There are a number of infectious diseases for which there is no equine vaccine, such as salmonellosis and clostridial diarrhea, which should be monitored for in any ill individual. Influenza Equine influenza is a RNA virus that sporadically occurs in epidemic form in most countries of the world. Clinical signs: fever, coughing, mucopurulent nasal discharge most commonly, with occasional distal limb edema and cardiac myopathy. Incubation period: 24 hours – 3 days Transmission: aerosol (respiratory droplets from coughing, snorting) which may occur for 7-10 days. Indirect transmission can occur through vectors (people, water and feed buckets). Diagnostics: virus isolation, PCR, immunoassay and paired serology. Shedding of virus: 7-10 daysEnvironmental persistence: up to 2 days on fomites, up to 3 days in water. Biosecurity guidelines: booster vaccination of healthy animalsunvaccinated animals should be vaccinated with a modified live intranasal vaccine maintain horses in isolation for 21 days after resolution of last suspected infection Herpesvirus Equine herpesvirus is a common DNA virus that occurs in horse populations worldwide. The 2 most common strains are EHV-1 (causing abortion, respiratory and neurologic disease) and EHV-4 (causing respiratory disease and occasional abortion). Clinical signs: fever, coughing, nasal discharge, weak neonatal foals, abortion in late pregnancy, incoordination of the hind limbs, urine retention/dribbling, recumbency. Incubation period: 24 hours-6 days or longer; abortion can occur from 2 weeks to several months following infection. Transmission: aerosol (most common) from respiratory droplets. Shedding can persist for more than 10 days. Indirect transmission through fomites, aborted fetuses/ fluids and the environment for several weeks. Diagnostics: virus isolation, PCR and paired serology. Shedding of virus: 21 days or more possible. Recovered horses may develop latent infections and may shed the virus during times of stress. Environmental persistence: usually less than 7 days, no more than 35 days. Biosecurity guidelines: booster vaccination of healthy animals; vaccinating unvaccinated animals is unlikely to be protective. Maintain horses in isolation for 28 days. West Nile Virus (WNV) WNV is a mosquito-borne flavivirus that causes disease in birds, humans and horses and is transmitted by many species of mosquitoes. The mortality rate is approximately 30%. WNV is considered endemic in the US. Clinical signs: mild low-grade fever, inappetance, lethargy, neurologic signs (sudden onset of imbalance, fine tremors of face and neck muscles, cranial nerve paralysis, limb paralysis). Incubation period: 7-10 days Transmission: mosquito vector. Diagnosis: MAC-ELISA, plaque reduction neutralization test, CSF analysis, post-mortem. Shedding of virus: there is no viral shedding. Environmental persistence: the virus is susceptible to drying, UV light and detergent. Biosecurity guidelines: prevention is the key! Vector management (reducing mosquito population). There are no other biosecurity issues: isolation is not required if WNV is confirmed. Zoonotic potential: human risk of exposure via bite of infected mosquito or through handling CNS tissue and/or fluids of infected animals. Equine Eastern Encephalitis (EEE) EEE is an alphavirus that is present on the East coast and is transmitted by mosquitoes (Aedes and Coquillettidia perturbans species). There is a 75-95% mortality rate associated with EEE. Clinical signs: moderate to high fever, depression, inappetance, cranial nerve signs, dementia, seizures, personality change, coma, death. Incubation period: 3-7 days. Transmission: mosquito vector. Diagnosis: MAC-ELISA, paired serum neutralizing antibody titers, CSF analysis, post-mortem. Shedding of virus: there is nor viral shedding. Environmental persistence: the virus is susceptible to drying, UV light and detergent. Biosecurity guidelines: prevention is the key! Vector management (reducing mosquito population). There are no other biosecurity issues: isolation is not required if EEE is confirmed. Zoonotic potential: human risk of exposure via bite of infected mosquito or through handling CNS tissue and/or fluids of infected animals. Strangles Streptococcus equi subsp. equi is the bacterium responsible for causing the upper respiratory disease known as strangles. Less commonly, the bacterium may affect lymph nodes in the thorax and/or abdomen, causing “bastard” or metastatic strangles. Clinical signs: fever 24-48 hours before other signs, lymphadenopathy ± abscessation, mucopurulent nasal discharge, pharyngitis, dysphagia, upper airway stridor. Incubation period: 3-14 days. Transmission: direct (horse-to-horse) and indirect through fomites. Diagnosis: bacterial culture, PCR, SeM-specific ELISA. Shedding of bacterium: 2-3 weeks post-recovery, intermittent shedding for months to years in carrier horses (bacterium persists in guttural pouches or paranasal sinuses). Environmental persistence: 30 days minimum. Biosecurity: record rectal temperatures twice daily and isolate horses with fever and/or clinical signs. Avoid horse-to-horse contact or any contact with respiratory droplets or abscessed material. Treat/feed/water infected horses last. Change boots/shoes/clothes after handling infected horses. Perform 3 consecutive weekly PCR and cultures prior to releasing infected horses. Horses on the premises that are not showing clinical signs and have a normal rectal temperature may be released in 21 days. Rabies Rabies is a fatal viral disease of mammals. Although relatively rare in horses compared to other viral neurological disease, the incidence is slowly increasing due to the proximity of horses to wild animals harboring the rabies virus (raccoons and skunks most commonly in GA). Clinical signs: highly variable. Disease is rapidly progressive and results in death in 5-7 days. Signs may include lameness, colic, dysuria, priapism, aggression, neurological disease. Rabies is considered a differential diagnosis in ALL cases of neurologic disease in horses. Incubation period: 2-6 weeks or longer. Transmission: bite wound from an infected animal. Diagnosis: post-mortem, fresh brain tissue. Shedding of virus: N/AEnvironmental persistence: the virus is susceptible to drying, UV radiation and detergent. Biosecurity: vaccinate horses annually! Any neurologic horses that die should be tested for rabies. Post-exposure vaccination is administered to personnel having contact with rabid horses. Previously vaccinated horses that are bitten by a rabid animal receive a booster vaccination and are quarantined and observed for 3 months. Zoonotic potential: rabies is 100% fatal in humans that do not receive post-exposure vaccination. Potomac Horse Fever (PHF) PHF is caused by the rickettsial organism Neorickettsia risticii. The disease can affected any age, breed or sex of horse and commonly occurs in the summer and fall. Clinical signs: diarrhea, fever, laminitis, mild colic, edema of limbs and ventrum, abortion. Incubation period: 1-3 weeks. Transmission: oral ingestion of trematodes present in aquatic insects, whole blood transfusion from infected donor, transplacental, other modes possible. Diagnosis: PCR, IFA titers. Shedding of organism: cases are not contagious. Environmental persistence: the organism remains within aquatic insects. Biosecurity: all horses with diarrhea are considered contagious unless proven otherwise. Horses with PHF may also shed Salmonella. Ruling out contagious causes of diarrhea prior to release of horse from quarantine. Biosecurity: if PHF is confirmed as the cause of disease and no other infectious causes of diarrhea are diagnosed, horses do not need to remain in isolation. The vaccination is not 100% protective but may reduce the severity of the clinical signs.
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