Colorado Department of Agriculture
Animal Industry Division
Livestock Disease Control
8 CCR 1201-19
Part 9:	Equine Viral Arteritis
I.	Introduction
The purpose of this rule regarding equine viral arteritis (EVA) is to protect the equine industry of the State of Colorado. Clinical disease due to EAV infection is a reportable disease to the Colorado State Veterinarian. Equine viral arteritis (EVA) is a contagious disease of horses caused by the equine arteritis virus (EAV). EVA is of special economic concern because it can result in abortion in pregnant mares, illness and death in young foals, and establishment of the carrier state in stallions. The import control policies of most countries currently deny entry to carrier stallions and EAV-infective semen because of the associated disease risks. It is important to enable the ability to require testing of some horses prior to vaccination to demonstrate that antibody titers are due to vaccination rather than natural infection. The vast majority of Colorado horses have never been exposed to the virus; therefore, the risk of spread of infection in Colorado is significant.
II.	Definitions 
A.	"Accredited veterinarian" means a veterinarian licensed by the Colorado Department of Regulatory Agencies, Veterinary Medical Examiners and approved by the United States Department of Agriculture (USDA) in accordance with 9 Code of Federal Regulations § 161 (2002) to perform functions required for state or cooperative state and federal animal disease control and eradication programs. (This rule incoporates by reference 9 Code of Federal Regulations § 161 (2002 ed). This rule does not adopt any later amendments to or editions of this section of the Code.  Additionally, anyone seeking to review a copy of the referenced material may contact the executive administrator of the Department of Agriculture located at 700 Kipling St., Ste 4000, Lakewood, Colorado, to learn how this information may be obtained or reviewed.  This and any other material that is incorporated by reference may be examined at any state publications depository library.)
B.	“Approved laboratory" means a laboratory approved by the State Veterinarian to conduct official testing for equine viral arteritis.
C.	"Book" or "booking" means the contracting or scheduling of a mare to be bred to a stallion.
D.	“Carrier” means a stallion that has a positive EAV culture or polymerase chain recation (PCR) test from semen.
E.	"EAV" means equine arteritis virus, the organism which causes the disease equine viral arteritis.
F.	"Equine" means a family of Equidae which includes but is not limited to horses, asses, jacks, jennies, hennies, mules, donkeys, burros, ponies, and zebras.
G.	"EVA" means equine viral arteritis, a communicable disease in equine resulting in abortion in pregnant mares, illness and death in young foals, and potential establishment of the carrier state in stallions.
H.	“Isolated” means the protocols to prevent the transfer of EAV through the appropriate separation, movement controls and biosecurity procedures approved by the state veterinarian.
I.	“ISO compliant microchip” means a microchip used to identify individual Equidae that are compliant with the International Organization of Standardization and the National Animal Identification System (NAIS).
J.	“National Animal Identification System (NAIS)” means a national program intended to identify specific animals and premises in the United States developed by the U.S. Department of Agriculture (USDA), state agencies and the livestock industry. This system is designed to enable traceback of the movements of any diseased or exposed animal.
K.	"Owner" means any person with the legal right of possession or having legal control over any Equidae, and shall include but not be limited to agents, caretakers, and other persons acting on behalf of that person.
L.	“PCR test” Polymerase chain reaction test to detect EAV in samples.
M.	“Semen” Secretion or ejaculate from the reproductive tract of a stallion containing spermatozoa and seminal fluid from the accessory sex glands. 
N.	“Sero-negative test mare” means a mare that has been tested sero-negative (SN titer <1:4) and has been isolated from other horses prior to being bred.
O.	"Sero-negative" means a horse that has reacted negatively (SN titer <1:4) to a blood test for antibodies to EAV.
P.	"Sero-positive" means a horse has demonstrated a positive reaction in serum neutralization with a titer of equal to or greater than one (1) to four (4) to a blood test for antibodies to EAV.
Q.	"Shedder" or "shedding" means an equine has been determined to have EAV in its body and has potential of transmitting the EAV to other equine.
R.	“Stallion” means a sexually intact male equine.
S.	“Standard insemination volume” means 10 ml of semen. 
T.	“Test breeding” means breeding a suspect carrier stallion to 2 seronegative mares a minimum of twice a day for 2 – 4 days in the same estrus period.
U.	"Vaccinated" or "vaccination" means an equine has been vaccinated with the approved EVA modified live virus vaccine and the vaccination status has been kept current in accordance with the manufacturer's recommendations.
V.	“Vaccinated sero-positive stallion” means a stallion that was sero-negative prior to being vacinated against EVA and which has a positive titer (>1:4) post vaccination.
III.	General EVA Information
A.	All laboratory samples pertaining to this rule shall be submitted by an accredited veterinarian to an approved laboratory.
B.	It is recommended that all breeding stallions be tested for EAV prior to use as a breeding stud or collection for artificial insemination.
C.	It is recommended that frozen semen or semen from unknown stallions be tested negative by virus isolation or PCR prior to being used for artificial insemination. 
IV.	EVA Shedding Stallions 
A stallion is considered to be a carrier if any of the following apply: the virus can be cultured from his semen, if the virus can be detected in his semen by PCR test or if sero-negative mares seroconvert to sero-positive status within 28 days following breeding or insemination.
A stallion known to be a carrier shall not be permitted to breed or be collected for artificial insemination until the state veterinarian determines that the stallion does not pose a risk of transmitting EAV. In making this determination, the state veterinarian shall consider whether the requirements of subsections B. and C. of this section will be complied with by the premises on which the carrier stallion is located. The following restrictions shall apply to a carrier stallion that is permitted to breed or be collected for artificial insemination:
A.	The owner or agent of an EAV carrier stallion shall notify in writing the owner or agent of a mare booked or seeking to book a mare to that stallion that has been classified as an EAV carrier. A written copy of the booking confirmation shall be sent to the state veterinarian.
B.	A carrier stallion shall be housed, handled and bred or collected for artificial insemination in a facility isolated from non-shedding stallions.
C.	A carrier stallion shall be bred to a mare(s) that:
 1.	Have been vaccinated against EVA at least twenty-one (21) days and not more than 1 year prior to being bred; or
2.	Has an existing EAV titer from vaccination or natural exposure to EAV, if the serological for EVA test was performed prior to date of breeding.
V.	Sero-Positive Non-shedding Stallions 
A.	A stallion may be considered to be a ‘vaccinated sero-positive stallion’ if a blood sample collected within 10 days prior to administration of an approved vaccine was negative (SN titer <1:4) for antibodies to EAV. See Section VIII for recommended vaccination protocols. 
B.	It is required that a sero-positive vaccinated stallion that did not have an EVA negative test prior to vaccination comply with one of the following testing procedures to ensure that the stallion is not at risk of transmitting the virus:        
1.	A standard insemination volume (10ml) of semen should be collected and either cultured for EAV or evaluated using a PCR test; or
2.	The stallion should be bred to two (2) mares negative for EAV antibodies. The two (2) mares should have blood collected for an EVA test twenty-eight (28) days after breeding or artificially inseminated from two ejaculates, separately collected. 
The sero-positive stallion would be considered a non-carrier if the semen culture, semen PCR or test-breeding results are negative. 
C.	A stallion may be considered a ‘nonvaccinated sero-positive stallion’ if the stallion has seroconverted following a natural exposure to the virus. It is required that a nonvaccinated sero-positive stallion be tested as outlined below prior to breeding to ensure that he is not at risk of transmitting the virus.
1.	Semen should be collected and either cultured for EAV or evaluated using a PCR test; or
2.	The stallion should be bred to two (2) mares negative for EAV antibodies. The two (2) mares should have blood collected for an EVA test twenty-eight (28) days after breeding or artificial insemination. 
The sero-positive stallion would be considered a non-carrier if the semen culture, semen PCR or test breeding results are negative.
D.	A stallion previously classified as a carrier stallion may be re-classified as a non-carrier stallion if the following criteria are met:
1.	During the first breeding season following the stallion's classification as a non-carrier, the first five (5) seronegative mares bred or artificially inseminated using semen collected from separate ejaculates from this stallion shall be test negative to a blood sample collected for an EVA test twenty-eight (28) days after breeding or artificial insemination.
2.	During the second breeding season, the stallion shall be bred to two (2) mares negative for EAV antibodies that will be tested twenty-eight (28) days after breeding or have its semen collected and cultured negative for EAV or have the semen tested negative by PCR for EAV. If the semen culture report or PCR test and blood samples are negative for EAV, there shall not be restrictions placed on a future breeding season.
E.	The final determination that a stallion is not an EAV carrier shall be made based on scientific procedures described in this section and approved by the state veterinarian. Until this determination is made the stallion shall be considered as an EAV carrier. 
VI.	Requirements for Breeding Mares to a Carrier Stallion or Inseminating Mares With Known EAV Infected Semen 
The following guidelines are required when breeding mares to a carrier stallion or inseminating mares with known EAV infected semen.
A.	If a sero-negative mare is to be bred to a carrier stallion for the first time.
1.	It is required that the mare be vaccinated a minimum of twenty-one (21) days prior to the first breeding or artificial insemination by an EAV carrier stallion and subsequently  isolated a minimum of twenty-one (21) days after the first breeding or artificial insemination.
a)	During isolation, the mare shall be physically separated from other equine in a separate isolation area approved by the state veterinarian or designated personnel.
b)	After the isolation period, the mare may move without restriction.
B.	Mares that have been vaccinated against EAV or have been bred to an EAV carrier stallion within the previous two (2) years may be re-bred to a carrier stallion but should be isolated for a minimum of twenty-one (21) days after breeding as noted above. 
C.	When a mare bred to a carrier stallion is returned to the premises of origin within 21 days of breeding, it shall be in a transport vehicle or trailer by herself or with other seropositive horses. Upon returning to the premises of origin, the transport vehicle or trailer and equipment used to move the mare must be immediately cleaned and disinfected according to procedures approved by the state veterinarian.
 VII.	Actions for Newly Diagnosed Sero-positive Stallions  
A stallion infected with EAV during the breeding season shall immediately cease breeding or immediately cease having semen collected for artificial insemination or semen collected and stored for future use. Since EVA is a reportable disease in the State of Colorado, the state veterinarian must be immediately notified in the event of clinical EVA disease demonstrated by a positive laboratory test on serum or semen. An owner or agent with a mare booked or bred to a stallion that became infected with EAV during the breeding season shall be immediately notified in writing by the stallion's owner or agent. A copy of the written notification shall be sent to the state veterinarian. A stallion infected with EAV during the breeding season shall be classified as an EAV carrier and shall be handled according to the requirements of this rule. Following the stallion's classification as a carrier, the state veterinarian may reclassify the stallion as a non-carrier in accordance with this rule.
VIII.	Equine Vaccinated Against EVA
Following are the recommendations that will provide for a more effective program for mares or stallions to be vaccinated for EVA in Colorado:
•	The equine owner’s facility should have an NAIS premises registration.
•	The mare or stallion receiving EVA vaccine should have an ISO compliant microchip implanted according to NAIS standards.
•	That mares be tested for antibodies to EAV prior to an initial EVA vaccination.
•	Testing for antibodies in blood of mares be submitted to an approved veterinary laboratory.
•	A certificate documenting the mare has been vaccinated be sent to the state veterinarian within seven (7) days of the vaccination date.
•	The EVA vaccination certificate for mares be on a form prescribed by the state veterinarian.
•	The prior negative EVA test and vaccination of intact colts between 6-12 months of age and of adult teaser stallions.    
Following are the requirements for mares or stallions to be vaccinated with EVA vaccine in Colorado:
•	Testing of stallions for antibodies in blood or evidence of EAV in semen shall be submitted to an approved veterinary laboratory. 
•	Stallions vaccinated for the first time against EVA shall be test negative to a blood sample collected by an accredited veterinarian prior to vaccination.
•	Stallions vaccinated for the first time against EVA shall have the EVA vaccine administered by an accredited veterinarian within ten (10) days after the sample collection date.
•	A certificate documenting that the stallion has been vaccinated shall be sent to the state veterinarian within seven (7) days of the vaccination date.
•	The EVA vaccination certificate for stallions shall be on a form prescribed by the state veterinarian.  
•	All equids vaccinated for the first time against EVA shall not have direct exposure to an EVA affected animal or a pregnant mare for twenty-one (21) days after vaccination.
•	A vaccinated stallion shall not be used for breeding or artificial insemination within twenty-eight (28) days after vaccination. A vaccinated mare shall not be bred within twenty-one (21) days of vaccination. 
IX.	EVA Test Mares 
A.	An EVA test mare shall be isolated from the other equine and under the supervision of the state veterinarian if the mare becomes:
1.	Clinically affected with EVA after breeding or artificial insemination; or
2.	Sero-positive after breeding or artificial insemination.
B.	An isolated mare shall be released from isolation by the state veterinarian after:
1.	Twenty-eight (28) days in isolation and providing test results are negative; or
2.	The spread of EAV is no longer a risk, whichever is longer.
Parts 10 – 15:	Reserved
Part 16:	Statements of Basis, Specific Statutory Authority and Purpose
IV.	Adopted: January 4, 2007 – Effective: March 4, 2007
The Colorado Department of Agriculture adopts the following rules according to its authority as found in Colo. Rev. Stat. § 35-50-105, et seq.
Statements of Basis, Specific Statutory Authority and Purpose
The statutory authority of this rule lies in § 35-50-105, et seq., C.R.S., 2005, specifically 35-50-105 (3)(f), (g) and (h), C.R.S., 2005, which grants authority to the Commissioner of Agriculture, with the approval of the Colorado Agricultural Commission, to set standards and requirements for testing livestock for infectious or contagious diseases and to set similar requirements for the vaccination of livestock to control infectious diseases. The Commissioner is further authorized to set standards and requirements for surveillance, testing, or implementation of other disease control measures.
The basis of this rule lies in the importance of controlling contagious disease among horses and other equine species and to facilitate commerce among citizens of Colorado and other states and countries. Equine viral arteritis (EVA) is a highly communicable disease spread among horses in two different manners. Infected equines with clinical signs of EVA can infect other equines by aerosol discharges from the mouth or nose. Male equines that have contracted EVA can then spread the disease to females by breeding or by artificial insemination. Therefore EVA is spread through both direct and venereal routes among equines. There is no direct treatment for the veneral disease, and therefore, male equines with the disease may have restricted ability to breed during the remaining period of their lives.
The purpose of this rule is to establish a widely accepted protocol for EVA disease control methods, testing, vaccination and record keeping requirements. This rule will enable owners of equines to contract for breeding their equines with increased confidence that EVA vaccination, testing, and disease control standards remain in effect in Colorado.