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Current Animal Disease Updates for MA

Public information related to current reportable animal disease issues in Massachusetts.

Rabbit Hemorrhagic Disease Virus

August 6, 2020

Rabbit Hemorrhagic Disease Virus Serotype 2 (RHDV2, Rabbit Calicivirus) was identified in New Mexico and New York in March 2020. Since that time, the virus has been found in wild and domestic rabbits in Arizona, California, Colorado, New Mexico, Nevada, Texas, Utah, and northern Mexico; and feral domestic rabbits in Colorado and Utah. At this time the virus has not been identified in Massachusetts and the outbreak in New York has been contained. For an updated map of reported RHDV2 outbreak locations, please see https://www.aphis.usda.gov/aphis/maps/animal-health/rhd.

Clinical signs of RHDV2 include fever, lethargy, respiratory signs, neurologic signs including seizures, and sudden death. Most often, the rabbit is found dead, sometimes with blood around the nose. Recovered rabbits shed virus for a month or longer. This non-enveloped calicivirus is very resistant in the environment and can remain infective for months. Rabbits may become infected through direct contact, or through exposure to virus within feces, urine, or on contaminated materials, including cages, bedding, and human clothing and footwear.

Currently there is no licensed vaccine in the US for RHDV, although one is in development. Under strict state and federal regulations, states with confirmed cases of RHDV2 may be allowed to import one of the killed vaccines used in Europe; however, these manufactures have stated they will not be able to support vaccine production for the needs of the US. Although vaccination may reduce the clinical signs of disease, it does not prevent a rabbit from becoming infected, developing clinical signs, or shedding the virus. Since Massachusetts has no confirmed cases at this time, veterinarians will not be allowed to import or use the vaccine. This means strict biosecurity measures are of utmost importance in preventing disease transmission.

To protect domestic rabbits, owners and caretakers should keep them indoors and maintain a closed colony. Virus may be brought inside on human clothing or footwear, and on other animals that spend time outside, including dogs, cats, and insects. It is recommended that caretakers change out of their “street clothes” when handling their rabbits. Animals that go outdoors should not have access to rabbit areas, and all animals in the household should be treated with appropriate flea prevention. For many reasons, domestic rabbits should never be abandoned outside or released into the wild. In this case, release of an infected domestic rabbit could be a source of infection for wild populations.

New rabbits and those returning to the colony should be quarantined for a minimum of 14 days. PPE including gloves and a smock, and dedicated equipment and supplies for cleaning, grooming, etc. is necessary when handling quarantined rabbits. Caretakers must wash their hands between groups of rabbits; and must change contaminated PPE and wash hands between quarantined individuals. Shared play areas should be thoroughly disinfected between groups of rabbits, and should not be used for those in quarantine.

Disinfectants that will inactivate RHDV2 are labeled to inactivate non-enveloped viruses, like parvovirus and feline calicivirus. Porous materials like wood, carpet, and upholstered furniture are much more difficult to decontaminate than non-porous materials, like metal. To clean and disinfect, remove all animals from the area and ensure adequate ventilation and PPE. Thoroughly remove and discard all bedding, fur, feces, and visible debris from the area. This step is important as some disinfectants are inactivated by organic material. Next, thoroughly wash the area with soap and water, and let it dry completely. Then, saturate all surfaces with disinfectant solution, allow for appropriate contact time, and rinse thoroughly. Preferred disinfectants include accelerated hydrogen peroxide (Rescue) and potassium peroxymonosulfate (Trifectant, Virkon S). Sodium hypochlorite (bleach) is effective only when no organic material is present. Bleach is corrosive and can cause respiratory issues in humans and animals if appropriate precautions are not taken. A list of products that are expected to be effective in inactivating RHDV2 has been published by the EPA: https://www.epa.gov/pesticide-registration/list-o-disinfectants-use-against-rabbit-hemorrhagic-disease-virus-rhdv2.

RHDV2 has not been found in wild rabbits in New England. For their own health and safety, humans and domestic animals should avoid contact with all wildlife and carcasses. Finding the occasional rabbit carcass is not cause for concern, as predation is the most common cause of death in wild rabbits. Sightings of multiple dead rabbits with no signs of trauma within several days may be cause for concern and should be reported to the Division of Fisheries and Wildlife.

For more complete information of biosecurity and disinfection, please see the Division of Animal Health’s RHDV2 Biosecurity article. For information related to wildlife rehabilitation, please contact the Division of Fisheries and Wildlife at (508) 389-6300. Suspected cases of RHDV2 must be reported to the Massachusetts Department of Agriculture at (617) 626-1795 and US Department of Agriculture Veterinary Services at (508) 363-2290. 

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Eastern Equine Encephalitis (EEE) in Animals

Massachusetts is currently dealing with an unprecedented level of Eastern Equine Encephalitis (EEE) virus in the mosquito population. Mosquitos pick up the virus from infected wild birds that ordinarily exhibit no symptoms. Infected mosquitos are capable of then transmitting the virus to people or horses. Infected humans and horses are victims only and play no role in transmission of the virus. The movement of horses (even if infected) does not spread the disease.

Mosquito control and mitigation efforts are incredibly important to decreasing the level of virus in the environment. Removal of standing water, getting rid of trash that can collect and hold water, and cleaning animal water buckets and troughs at least twice weekly will diminish mosquito breeding habitat. Judicious use of pesticides further limits the mosquito population numbers, mosquito bites and potential transmission of the virus.

Avoidance of outdoor activities during peak mosquito activity (dusk to dawn) further diminishes risk. For people, risk mitigation is the critical component.

For horses avoidance of outdoor activities is more challenging because they are horses. Their environmental exposure is higher but we also have the advantage of a readily available and highly effective vaccine. Appropriate vaccination of horses is highly protective and associated with limited risk. None of the 2019 equine EEE cases occurred in an adequately vaccinated horse.

The message is VACCINATE your horse! The vaccine works and is highly protective. Timing of the vaccine can be critical. Most of the EEE vaccines are part of a combination vaccine that includes Eastern and Western Encephalitis, Tetanus, plus or minus West Nile Virus often called EWT or EWT/WNV.

If your horse was vaccinated this year, check with your veterinarian about a booster. If your horse was not vaccinated this year then vaccinate immediately. Previously vaccinated horses may quickly respond to a booster vaccine and readily develop protective antibody. Horses of unknown vaccination status should receive two vaccines the first year.

Foals of 2019 should be vaccinated as soon as they are old enough (3-4 months of age) and need a second booster vaccine for adequate protection. Please do not forget the mare. She was likely vaccinated early in the spring prior to foaling and may need a booster vaccine to ensure protection until the first killing frost.

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Eastern Equine Encephalitis (EEE) Vaccinations

September 6, 2019

Massachusetts is currently dealing with an unprecedented level of Eastern Equine Encephalitis (EEE) virus in the mosquito population. Mosquitos pick up the virus from infected wild birds that ordinarily exhibit no symptoms. Infected mosquitos are capable of then transmitting the virus to people or horses. Infected humans and horses are victims only and play no role in transmission of the virus. The movement of horses (even if infected) does not spread the disease.

Mosquito control and mitigation efforts are incredibly important to decreasing the level of virus in the environment. Removal of standing water, getting rid of trash that can collect and hold water, and cleaning animal water buckets and troughs at least twice weekly will diminish mosquito breeding habitat. Judicious use of pesticides further limits the mosquito population numbers, mosquito bites and potential transmission of the virus.

Avoidance of outdoor activities during peak mosquito activity (dusk to dawn) further diminishes risk. For people, risk mitigation is the critical component.

For horses avoidance of outdoor activities is more challenging because they are horses. Their environmental exposure is higher but we also have the advantage of a readily available and highly effective vaccine. Appropriate vaccination of horses is highly protective and associated with limited risk. None of the 2019 equine EEE cases occurred in an adequately vaccinated horse.

The message is VACCINATE your horse! The vaccine works and is highly protective. Timing of the vaccine can be critical. Most of the EEE vaccines are part of a combination vaccine that includes Eastern and Western Encephalitis, Tetanus, plus or minus West Nile Virus often called EWT or EWT/WNV.

If your horse was vaccinated this year, check with your veterinarian about a booster. If your horse was not vaccinated this year then vaccinate immediately. Previously vaccinated horses may quickly respond to a booster vaccine and readily develop protective antibody. Horses of unknown vaccination status should receive two vaccines the first year.

Foals of 2019 should be vaccinated as soon as they are old enough (3-4 months of age) and need a second booster vaccine for adequate protection. Please do not forget the mare. She was likely vaccinated early in the spring prior to foaling and may need a booster vaccine to ensure protection until the first killing frost.  

Potomac Horse Fever

August 12, 2019

The Massachusetts Department of Agricultural Resources has received a report of a single confirmed case of Potomac Horse Fever (PHF) in a horse housed at an Essex county stable.  The horse presented to a referral hospital with signs of colitis. This follows a case in a Norfolk county horse in July. That horse’s initial clinical presentation was “off feed” and uncomfortable, signs generally associated with mild colic. Fever and diarrhea came later. 

Potomac Horse Fever (PHF) is a seasonal bacterial disease of horses.  The disease is caused by the bacteria (Neorickettsia risticci). The complicated transmission cycle is associated with freshwater snails and certain aquatic insects. Clinical signs in horses include fever, colic, and diarrhea. Horses that are sick with PHF are not considered to pose a risk to other horses. Treatment of sick horses should be initiated promptly to avoid the potential for severe dehydration and colitis which may be fatal.

There is a commercial vaccine approved and available that may offer some protection. Other recommendations to prevent transmission include not letting horses drink from streams and ponds, cleaning water buckets to remove any insects, and turning off lights in stables at night to avoid attracting insects. It is also suggested to be careful not to sweep dead insects off the floor into stalls or mangers where horses may inadvertently consume them. 

Although the disease is unusual in New England, Massachusetts had a single confirmed case at a Norfolk County stable with a second suspect case at the same farm in 2018. The Equine Disease Communication Center (EDCC) also reported a PHF case at a farm in CT in 2018. 

Please continue to monitor your horses’ health.  Temperature monitoring continues to be our best early warning system. Please report any sick animals promptly to your veterinarian so potentially life-saving treatment can begin right away.

Potomac Horse Fever is a reportable disease in Massachusetts.  Contact the Division of Animal Health at 617-626-1795 upon diagnosis.  Additional reportable disease information can be found on the Reportable Animal Disease Program page.

Equine Corona Virus: Horse Show Risk Assessment

March 1, 2019

Equine Coronavirus (ECoV) risk assessment during horse shows

This document provides basic information regarding Equine Coronavirus (ECoV). ECoV is a recently identified contagious disease that generates a high level of concern and much communication within the equestrian community. Horses that are competing may encounter ECoV at a show or other event. ECoV is known to be transmitted by a fecal- oral route (transmission through the manure of a horse that is shedding the virus).

Good biosecurity should be practiced at all horse gatherings/ competitions which will decrease exposure to the virus.  See EDCC guidelines. http://www.equinediseasecc.org/disease-information

Summer 2018 ECoV incidents in the Northeast Region of the USA:

During the late summer of 2018, several horses were affected by ECoV at a horse show. Most of the affected horses had the typical mild-to-moderate, self-limiting gastrointestinal disease but a small number of horses was more severely affected. ECoV is diagnosed sporadically throughout the year but is more common in the cooler months.

What we known about ECoV

  • ECoV has been recognized in the last several years as a new/emerging gastrointestinal disease in adult horses (1). Only about 25% of the naturally infected horses show clinical signs.
  • Approximately 10% of horses with clinical signs of fever, lethargy, anorexia (lack of appetite) or diarrhea due to ECoV also show signs of colic (abdominal pain).
  • Mortality is low (3-7%).  Fecal-oral infection with ECoV is currently considered as the likely exclusive form of transmission between horses (4).
  • We expect that horses will shed the EcoV virus for approximately 25 days; however, longer shedding times and asymptomatic chronic shedders have been anecdotally documented. Information about how long ECoV can survive in the environment is limited. Survival of virus in the environment depends on many factors, including presence of a porous surface, humidity, and number of viral particles present, so it is difficult to predict. General recommendations for showgrounds facilities to minimize the risk of ECoV (and other contagious disease) include the following:
  • Show ground facility managers should clean and disinfect (C and D) the entire facility several times a year as well as between closely scheduled horse shows. Manure should be removed from the stalls and premises as soon as possible, thus decreasing the likelihood of horses being exposed to contagious disease.
  • Show ground facility managers should have a biosecurity system in place prior to every event.This should include a plan for any ailment or disease that may occur at the event. Dedicated biosecurity officers (these can be specially trained show personnel) should be present at all show grounds or events. This will allow a quicker and more thorough response to a suspected contagious disease, thus minimizing potential spread and facilitating early therapy if indicated.
  • Show ground facility managers should require a CVI (Certificate of Veterinary Inspection, also known as a health certificate) prior to entry to the show grounds and should screen all horses entering the show grounds.

As a responsible equestrian planning to attend a horse show you should take basic biosecurity measures including:

Take home messages:

  • ECoV is a newly recognized infectious disease that can affect individuals and groups of horses.Morbidity and mortality rates vary with the horses own health status and response to illness as well as circumstances surrounding the exposure and conditions at the stabling facility. Infectious disease is part of the inherent risk of horse shows. This risk cannot be reduced to zero but can be minimized by responsible and professional conduct by showground facilities, show organizers and the equestrian community
  • We hope that this document helps Northeastern equestrians becoming better educated, more enthusiastic and better prepared for show season this spring!

 DAR, The Massachusetts Department of Agricultural Resources Division of           Animal Health

Ron Vin, DVM, DACVIM, Vin Equine Services, Myhre Equine Clinic

Linda Mittel, MSPH, DVM Animal Health Diagnostic Center Cornell University

Melissa R. Mazan, DVM, Diplomate ACVIM, Cummings School of Veterinary Medicine, Tufts University

References:

  1. Enteric coronavirus infection in adult horses N. Pusterla, R. Vin, C.M. Leutenegger, L.D. Mittel,

T.J. Divers. The Veterinary Journal Volume 231, January 2018, Pages 13-1

  1. Study on the resistance of severe acute respiratory syndrome-associated coronavirus Xin- WeiWanga., et al Journal of Virological Methods Volume 126, Issues 12, June 2005, Pages 171- 177
  2. Overview of Feline Infectious Peritonitis. Julie K. Levy. The Merck Manual
  3. Experimental inoculation of equine coronavirus into Japanese draft horses Nemoto, M., Oue, Y., Morita, Y., Kanno, T., Kinoshita, Y., Niwa, H., Ueno, T., Katayama, Y., Bannai, H., Tsujimura, K., et al. 2014. Archives of Virology 159, 33293334.
  4. AHDC online information:

https://ahdc.vet.cornell.edu/docs/EquineCoronavirusFactSheet_Sept10_Accessible.pdf

6.   Boone S, Gerba C.  Significance of Fomites in the Spread of Respiratory and Enteric Viral Disease. Appl Environ Microbiol. 2007, 73(6):1687-1696

 

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