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New Jersey Horse Health News

From the New Jersey Department of Agriculture
in cooperation with the
New Jersey Association of Equine Practitioners
Christine Todd Whitman, Governor Arthur R. Brown, Jr., Secretary

Horse

EQUINE HEALTH NEWSLETTER DEBUTS

This quarterly newsletter has been prepared by the New Jersey Department of Agriculture in cooperation with the New Jersey Association of Equine Practitioners. The purpose of this publication is to provide New Jersey horse owners with current information and advice on horse health issues. The newsletter will include articles on current horse issues in our state such as reportable diseases, recommended health management practices, and updates on legislation.

Veterinarians from around the state will be contributing articles of interest for New Jersey horse owners. In addition, readers may suggest future topics by contacting the newsletter editor. We look forward to bringing New Jersey horse owners current, factual information on health issues which may be happening in their own back paddock.

Next month's topics include Lyme disease in horses, equine protozoal myelitis and more vaccine recommendations.

Editor

In this issue ...

        PREVENTIVE MEDICINE 
        RABIES IN HORSES  
        EQUINE INFECTIOUS ANEMIA 
        LEGISLATIVE NEWS
        DID YOU KNOW? 
        EQUINE RESOURCES ON THE WEB

REVENTIVE MEDICINE
INCLUDES SCHEDULED VACCINATIONS

You've often heard the term "preventive medicine" used in terms of horse health but exactly what does it mean? In general, the term includes any management practice conducted for the purpose of preventing future illness or injury in a living creature, humans and animals alike. Such practices include everything from providing adequate, quality feed and fresh, clean water to implementing a strategic vaccination program.

Horse owners are aware of the need to provide quality feed and water for their animals but what about vaccination schedules? The effectiveness of a vaccination program cannot be gauged by your horse's appearance. Often the first indication you might have that your horse is overdue on its vaccinations may be seeing actual signs of disease, as commonly happens with influenza outbreaks. There may be no warning signs before that to let you know that immunity is waning.

Sometimes seeing, or hearing about, a sick horse reminds us to double- check on our vaccination schedule. Different vaccines have different vaccination schedules and, in some cases, vaccinations should be given two or even three times a year (e.g., influenza) or annually (e.g., rabies).

Currently, there are approximately 90 U.S. equine vaccines, approved by the USDA to prevent about 14 different viral and bacterial equine diseases; many pharmaceutical companies produce different brands of the same type of vaccines. While vaccinating a horse may not necessarily prevent the vaccinated animal from becoming sick when exposed to a particular infectious organism, it should at least diminish the severity of illness that the horse develops following exposure.

So, what types of vaccines should be used to keep New Jersey horses as disease free as possible, and how often should these vaccines be administered in a preventive medicine program?

As a guide, the New Jersey Association of Veterinary Practitioners (NJAEP) recommends that New Jersey horse owners vaccinate against the following diseases: rabies, tetanus, encephalitis, influenza, and rhinopneumonitis. Other vaccines may be recommended based on the age of the horse and infectious organisms identified locally.

In this issue, we will take a close look at two equine diseases: equine infectious anemia and rabies. One disease depends on insect control and Coggins tests as preventive measures of disease spread (equine infectious anemia) while the other may be controlled by vaccination (rabies).

EQUINE INFECTIOUS ANEMIA

Equine infectious anemia (EIA) is an infectious disease of horses which slowly erodes their immune system. This viral disease has commonly been called "Swamp Fever," as early clinical cases were commonly associated with geographic areas noted for plenty of water and insects. The EIA virus is similar to the AIDS virus of humans and the immunodeficiency virus of cats. All of these viruses are lentiviruses, which are transmitted only between members of the same species. There are currently no vaccines or cures for these viruses.

The EIA virus may be transmitted from horse to horse by certain species of blood-sucking insects (horseflies, deerflies) which have cutting mouth parts. Insertion of the fly's mouth parts into an infected horse picks up infected blood cells. These infected blood cells are then transferred to a second horse during another meal. For this reason, insect control is critical in keeping down transmission from infected to non-infected animals. Also, needles may play the part of an insect's mouth parts, and "outbreaks" of EIA have been linked to multiple needle use on horses.

In addition to insect control, testing of horses for the EIA virus is performed as a preventive measure of disease spread. The Coggins test, named after the scientist who developed the technology, checks for the presence of EIA antibodies in the horse's blood. If these antibodies are present, the horse has been infected with the virus. In most states, including New Jersey, a horse with a positive Coggins test must either be completely isolated from other horses and insects, or destroyed.

EIA ACROSS THE UNITED STATES

New Jersey is one of many states in the northeast with a strong disease control program for EIA. For this reason, New Jersey and most New England states have had very few cases of EIA diagnosed over the past 10 years. A look at available USDA statistics from October 1, 1995 to September 30, 1996 finds that Maine, Vermont, Rhode Island, Connecticut, Delaware and Maryland all reported zero EIA positives in that time frame. Meanwhile, New York reported 11 positive cases, while Pennsylvania reported eight. New Jersey and Massachusetts each reported two EIA positives while New Hampshire reported three.

States which reported over 25 EIA positives in the same time period include Tennessee, Florida, Mississippi, Louisiana, Arkansas, Oklahoma, Texas, Illinois and Minnesota. In fact, the states with the highest percentage of test-positive horses have originated from horses in what is referred to as "The Hot Zone": those states which border the Gulf of Mexico or the Mississippi River and Oklahoma. In this "Hot Zone" area of the country, the reservoir of insects capable of transmitting the virus persist almost year round and many horses have gone untested due to lack of state regulations.

EIA CASES IN NEW JERSEY

The majority of horses which are found to be positive for EIA are inapparent carriers of the virus which are detected on routine annual tests. These horses have been exposed to the virus, may have experienced a mild fever and have recovered. With stress, these infected horses may develop clinical signs of disease such as weight loss, anemia, fever, weakness and edema.

One clinical case of EIA was diagnosed in New Jersey in September 1996. This case was a thoroughbred racehorse which had been running at the Philadelphia Park, became ill, and was shipped to a veterinary hospital in New Jersey. The attending veterinarian had blood sent out for a Coggins test and the result, 24 hours later, was positive.

Because this infected horse had been in contact with many horses at the Philadelphia Park, a quarantine was placed on horses at the track until Coggins tests on those horses were found to be negative ... 45 days after the sick horse left the Park. Fortunately, none of the racehorses exposed to the infected horse tested positive for EIA. Because there is no treatment for this disease (or vaccine for prevention), the infected horse was destroyed.

Not all EIA infected horses show clinical signs of disease, as the racehorse mentioned above. Two EIA-positive pleasure horses were identified in Monmouth and Salem Counties in the past year. One horse had been in the state approximately one month, while the second had been a New Jersey resident for over a year.

The first horse (Monmouth County) had been brought into the state without a health certificate or current Coggins test. Trace back of this horse revealed that it was brought into the state by a horse dealer's agent from New York. The horse dealer in New York bought the horse from a second dealer who had obtained the horse in Arkansas. The owner who purchased the horse in New Jersey was given a copy of a Coggins test chart, which appeared to match the horse's description. The Coggins test was more than one year old, however. Trace back of the movement of this horse resulted in the quarantine of approximately 90 horses in New York and three farms with 70 horses in New Jersey. No additional EIA positive horses were identified in New Jersey as a result of exposure to this horse.

The second EIA positive horse (Salem County)was a mare which had also been brought into New Jersey by yet another horse dealer. This dealer had also purchased this horse from Arkansas. The New Jersey owner who ultimately purchased this mare reported that he had been provided with a negative Coggins test at the time of purchase. A review of this Coggins test result shows that the blood test had been conducted in Arkansas approximately six months before the horse was sold in New Jersey. This mare foaled six months after residing in New Jersey. Six months after foaling, the owner decided to sell the mare and had a Coggins test performed in preparation for the sale. This test came back positive, as did the Coggins test on the weaned foal. Trace back of possible contact horses to this EIA positive mare resulted in testing approximately 30 horses from six different owners. All contact horses were found to be negative.

Neither of the two EIA positive horses mentioned above was clinically ill. Typically, it is the routine testing of horses prior to sale or show which turn up EIA reactors. Two additional EIA positive horses passed through New Jersey from neighboring states to horse auctions in New Jersey in 1997. Since these horses did not have current Coggins tests when presented at the sale, blood was taken for EIA testing before they were sold. The blood tests were conducted at the New Jersey Department of Agriculture and trace back of the animals begun within 24 hours of the sale. As it turned out, both of these horses were on their way to a slaughterhouse from the sale. One of the two horses had come from Pennsylvania, where it had resided for years. Trace back of the movement of this horse involved exposure to approximately 80 horses from 35 owners in Pennsylvania. Blood testing of these contact horses revealed one EIA positive pony.

EIA REGULATIONS

An outline of New Jersey's disease control program for Equine Infectious Anemia may be found in the New Jersey Administrative Code under Title 2. These statutes require any horse entering New Jersey to have a health certificate and Coggins test taken within one year of import. If, however, a horse is being brought into the state to go to a horse sale, or is a New Jersey resident horse going to a horse sale, the owner must have a health certificate and Coggins test for the horse taken within 90 days of the date of sale; this is the responsibility of the seller. In addition, any New Jersey resident horse which is transported on a roadway in New Jersey must carry a valid Coggins test current within two years of the date of travel.

(Note: surrounding states require a valid Coggins test within one year of the date of travel.)

EIA PREVENTIVE MEDICINE

Currently, medical researchers are striving to develop a vaccine for AIDS in humans. The cost of that research effort is now measured in hundreds of millions of dollars. There is little likelihood of such a research effort being made for EIA in horses.

Because of the lack of a cure for EIA, and no immediate hope of a vaccine for prevention, horses will continue to have only state regulations for protection. These regulations require the routine blood testing of those which travel between states, or within states. In this way, when horses congregate at shows or sales, there will be little risk of the spread of EIA. By ensuring that Coggins test papers are current (and not fraudulent), show and sale officials are doing their part to stop the spread of this incurable disease in the horse population.

Some states, such as Texas, have relied entirely on horse shows to monitor for EIA by requiring current Coggins test charts prior to show registration. Just this month, the Texas Animal Health Commission announced that Texas is expanding their EIA testing requirements to include all equine moving to boarding stables and pastures, breeding farms and training stables. By expanding the test requirements, the prevalence rate of EIA in Texas should drop from the present level of approximately .3% of horses tested.

RABIES IN HORSES

Although horses and other livestock are infrequently infected with rabies, they are susceptible to the virus if bitten by a rabid animal, i.e., raccoon, skunk, fox, or bat. Horses displaying signs compatible with rabies infection (fever, lack of appetite, lameness, colic, facial nerve paralysis, weakness, restlessness, progressing to lack of coordination, vocalization, drooling and paralysis) should be examined by a veterinarian immediately. If the veterinarian determines that the neurologic signs are consistent with rabies, he or she is required to contact the local health department which has jurisdiction over the horse location. The local health department will assist the veterinarian and horse owner with the protocol to follow for rabies specimen collection and transportation to the New Jersey Department of Health and Senior Services (NJDHSS) Public Health Laboratory in Trenton for diagnosis.

WHEN RABIES IS SUSPECTED

Knowing who to call and what procedures to follow in the case of a possibly rabid animal will save considerable time and confusion should the situation ever arise on your farm.

If possible, a horse suspected of having rabies should not be euthanized before a plan to transport and test the specimen has been arranged. Transport options include direct delivery to the laboratory, private delivery services, state courier service and local health department transportation.

State courier service should not be used for cases with high risk exposures since testing is usually delayed several days while the specimen is in transit.

In the event that rabies is diagnosed by examination of brain tissue, the local health department will investigate and consult with individuals who may have been exposed to the rabid animal and help determine if human post-exposure rabies treatment is necessary.

The New Jersey Poison Information and Education System provides human rabies exposure consultations and may be able to assist callers with contacting local health departments on a 24-hour basis at (800) 962-1253.

If problems arise with the submission of specimens or laboratory testing, the NJDHSS Infectious and Zoonotic Diseases Program may be called directly between the hours of 8 am and 5 pm at (609) 588-3212.

The Division of Animal Health, New Jersey Department of Agriculture, may assist large animal veterinarians with brain removal and, at times, with specimen transport. The division my be contacted between the hours of 8 am and 5 pm at (609) 292-3965 after the local health department has been contacted.

RABIES CASE REPORT: JANUARY 1998

A four-year-old thoroughbred gelding, stabled in Far Hills, was reported by the owner to be lethargic and colicky on January 12th. The horse was off feed and lethargic through the following day and examined by a veterinarian on January 14th, when it was found to be ataxic and depressed, with a fever of 105EF and signs of cranial nerve dysfunction.

Upon veterinary examination, the owner reported that the horse had last been vaccinated for rabies in November 1996 while stabled at another farm. The owner, however, could not locate the health records for confirmation.

After being examined by the veterinarian, the horse did not respond to therapy, continued to deteriorate, and was euthanized on January 15th. The head was submitted to the Division of Animal Health for removal of the brain and delivery to the NJDHSS rabies laboratory, where it was determined to be positive for rabies on the 16th. Seven people, including the owner and veterinarian, are currently undergoing rabies post-exposure treatment because of contact with the horse's saliva within 10 days of the onset of disease.

Because this horse had a history of rabies vaccination, rabies did not appear to be the most likely diagnosis at the time of this illness. Once the horse was euthanized, however, the veterinarian recognized that the brain would have to be tested for the rabies virus due to the neurological signs it had demonstrated before euthanasia. As it turned out, the rabies virus was identified and, when located, the health records of this horse had no rabies vaccination history.

Currently, the New Jersey Association of Equine Practitioners (NJAEP) recommends that all horses receive a first rabies vaccine at three months of age and then annually thereafter since equine rabies vaccines are only approved for a one-year duration of immunity. Four animal health companies manufacture USDA-approved rabies vaccines for horses.

The NJAEP strongly recommends that horse owners maintain a current file of all of their horse health records (including the date and type of all vaccines administered) and stay on schedule with all preventive medications.

DID YOU KNOW?

One case of eastern equine encephalitis (EEE) was diagnosed in New Jersey in 1997. This case was identified in late October as a five-year- old thoroughbred gelding stabled in Indian Mills, Burlington County. Mosquito trapping sites, monitored by the New Jersey Agriculture Experiment Station, first isolated the EEE virus from a pool of mosquitos collected in Cape May on September 9, 1997. In general, mosquito numbers at South Jersey trapping sites tended to be below average in 1997 until mid-September, when averages jumped above the levels trapped over the previous 12 years.

Where does the EEE virus come from? Why do we track EEE in mosquitos? When should horses be vaccinated? A review of EEE and answers* to these questions will appear in the next issue of the New Jersey Horse Health News.

*Note: EEE is a virus which circulates in the wild bird population. It is carried between birds by mosquitos. If a mosquito carrying the virus bites a horse or person, the virus may infect this new host. Clinical signs include fever, incoordination, confusion, impaired vision, progressive paralysis, convulsions, and death 2 to 3 days after the onset of disease.

LEGISLATIVE NEWS

Legislation (A-817) signed into law on January 9, 1998 by Governor Whitman is designed to reduce the liability of a horse and land owner, manager, trainer, farrier, transporter, director and veterinarian. The law states that "equine activities involve risks that are impractical or impossible to eliminate and that those risks must be borne by those who engage in those activities." A sign must be posted in a common area stating this. Copies of this legislation may be obtained from Legislative Information, located in the State House Annex, at (609) 292- 4840. A maximum of three copies may be mailed out per request.

NEWSLETTER EDITOR
Janice L. Nicol, DVM, MS
New Jersey Department of Agriculture
Division of Animal Health
PO Box 330
Trenton, New Jersey 08625-0330
(609) 984-2251 Phone
(609) 633-2550 Fax

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