It is very important that management is vigilant in optimising the prevention and containment of diseases.

Breeding farms are ideal because a) there is a lot of movement of horses on and off farm, b) there is a high proportion of young susceptible stock with less immunity than older horses, and there is a mixture of young horses ( foals) mixed with older horses (broodmares).

The amount of infectious disease on a farm tends to INCREASE according to the NUMBER and CONCENTRATION of horses on the farm, and the amount of movement of horses ON and OFF the farm.

SLIDE 2

On a farm, the basic way to reduce infectious disease is to firstly REDUCE THE CHALLENGE that the horses are exposed to. I.e. Keep the environment as IDEAL as you possibly can to limit the chance that bugs have to get established within your farm, and secondly to ENHANCE THE RESISTANCE THAT YOUR HORSES have by using vaccination protocols to protect them... There are different considerations for every disease, all the different diseases have their own individual ideal set of conditions. That makes it difficult – what is good for eliminating one disease makes it difficult to prevent the next. It is a real juggling act to have a balanced management that limits the establishment of all diseases.

It is important to be aware that complete prevention of disease is an unrealistic expectation., We are dealing with a commercial proposition whereby horses are run together in close contact under often stressful conditions. Despite all your best efforts you are never going to prevent every disease from occurring on your farm.. The important thing is to recognize WHEN those diseases are starting to occur and to take steps to limit their spread.

This talk is basically going to go through some diseases commonly found on farms., or commonly not wanted to be found on farms. Hopefully I will be able to give you some insight how and why they occur and what steps you can take to limit their impact on your farm.

SLIDE 3

Good broodmare management is the cornerstone for success in any infectious disease management program.

This is because the broodmare is responsible for the production of a healthy live foal and responsible for the early immunity that her foal possesses.

SLIDE 4

The first topic I am going to talk about is ABORTION. It is important to realize that there are a few different causes of abortion, and not all of them are a result of infectious, contagious diseases. However, the take home message that I would like to give you all from this lecture today is that it is essential that all abortions are treated like an infectious, contagious abortion UNTIL PROVEN OTHERWISE. An infectious, contagious outbreak for a stud farm can mean economic disaster.

There are three different groups of abortion. INFECTIOUS, NON INFECTIOUS, and UNKNOWN.

SLIDE 5

NON INFECTIOUS causes of abortion includes old mares with a fibrotic uterus. You can get a guide as to the probability of a mare slipping, especially if she has slipped before, by having an endometrial biopsy done at the beginning of the breeding season. Having a fibrotic uterus limits the area of the uterus that the foetus is able to establish nutrition from and limits the development of the foetus and placenta.

Another cause of non infectious abortion is twinning. It is imperative that you have your mares scanned early, from 14-19 ( or 11 days if you are AOM) to ensure that your vet has a reasonable chance of successfully squashing a twin without damage to the other foetus.. It is the vets responsibility to make sure that no twinning occurs. However you can’t blame the vet if you didn’t have your mare scanned until day 30 or greater, the likelihood of damaging the other twin increases as the foal increases in size and while possible to crush at this late stage it increases the risk. Now having said that, you have to be aware that vets are not superhuman, I have seen Angus at the crush in tights, goggles and a cape scanning mares, but no one else, and in any case it is a very ugly sight. Twins do happen, despite the best intentions of everyone. So it is important if there is any doubt about cysts and possible twins etc that you don’t grizzle about the bill but that you get those mares RECHECKED where a positive yes or no she does or doesn’t have twins can be determined.

Other causes of non infectious abortion is systemic illness of the mare for example colic or endotoxaemia and infections.

SLIDE 6

Infectious abortion can be divided into two types:- Infectious (but not contagious) abortion and infectious and contagious abortion.

Placentitis is a form of infectious (but not contagious) abortion. Placentitis is infection of the placenta.

It is most commonly caused by an infection that enters through the cervix whilst the mare is pregnant. Another reason it occurs is because of infection that lodges at the placenta from the blood stream. This type of placentitis is very difficult to predict or understand and even more difficult to prevent as you could imagine.

Many bacteria and some funguses are capable of causing placentitis.

Placentitis can causes the placenta to become insufficiently attached to the uterus to supply the foetus with its necessary nutrition and oxygen, leading to its death and subsequent abortion or the premature or term birth of an ALIVE BUT WEAK FOAL..

SLIDE 7

The important thing to recognize here is that EARLY RECOGNITION is the key.

Look for early development of an udder, or streaming of milk, and check daily for vulval discharge.

If any of these signs develop your mare needs urgent veterinary attention.

The basic procedure is to have the placental junction ultrasounded to assess it thickness and its attachment to the uterus.

A lot of work and research needs to be done on how to manage placentitis. Treatment can be unsuccessful but is sometimes rewarding. The basic treatment regime involves antibiotic therapy, anti-inflammatory therapy and Regumate.

It is also very important to realize that there is a strong likelihood that you are going to be presented with a critically ill foal. It is important to be aware that there is a strong likelihood that your foal will need to be on antibiotics from birth. In some cases the only indication that you will have that the placenta has been infected is after birth when the placenta can be unusually thickened, heavy and large. In these cases also there is a strong indication that your foal will need antibiotics.

SLIDE 8

Prevention of placentitis is difficult because placentitis is often an opportune infection. The basic precautions to take are to ensure that hygiene at breeding, treating and parturition is adequate and to make sure that any mare requiring a caslick is given one.

SLIDE 9

Now onto infectious abortion. Equine Herpes virus 1 and 4 are both causes of equine abortion and are both highly contagious.

Equine Herpes Virus 1 is the single most important cause of equine abortion.

Equine Herpes Virus 4 is the single most important cause of respiratory disease and is occasionally associated with equine abortion.

SLIDE 10

Equine Herpes Virus 1 or 4 gains entry into the horses system through the mucus membranes of its nose, gums or eyes.

It multiplies in these cells and then makes its way to the respiratory tract lymph nodes within 2 to 3 days of exposure to the virus. It also can ‘rest’ in white blood cells and certain endothelial cells ,( the blood vessels of the uterus containing endothelial cells is an especial target.)

Initial clinical signs at this point could include an increase or decrease in temperature, a horse that is off its food and depressed, enlarged lymph nodes, and a serous or clear nasal discharge that may become mucopurulent.

SLIDE 11

It is highly contagious and is spread via close contact between horses via aerosols from coughing or snorting horses, through handlers, and from sharing drinking water or feeders.

The most contagious and infectious matter however is the aborted foetus and placenta of an infected mare.

As I mentioned previously the virus rests and multiplies in the endothelial cells of the blood vessels of the uterine wall. From this vantage point, with the foetus relying on these blood vessels for nutrition and oxygen, the virus makes its way into the foetus where it infects the foetus causing pneumonia, bronchiolitis and hepatic necrosis or inflammation. It DOES NOT damage the uterus but severely damages the foal, resulting in the subsequent abortion or birth of a severely ill and short lived foal.

SLIDE 12

The incubation period is between 2 weeks and 3 months. 95% of mares will abort in the last 4 months of pregnancy. The majority of these will abort 10-20 days after infection with the virus.

SLIDE 13

So how do these outbreaks of EHV abortion occur?

Well firstly, unfortunately EHV can develop a carrier state whereby a horse that has been exposed to EHV at one time but is not clinically sick at the present ‘carries ‘ the EHV virus around in its lymph nodes and white blood cells.

Under a state of stress, which can be any sort of stress and is not always an apparent stress, the virus becomes ACTIVE and infects that mares foetus. The mare does not always shed virus through her nasal secretions and often the first exposure all her paddock mates have to the virus is their exposure to her aborted foetus and placenta. Then 10 –20 days later an abortion storm will occur and a great percentage of the in contact mares will abort due to the EHV.

The second way that an abortion storm may occur is by the introduction of a non quarantined mare into the herd who is shedding the virus. In this case the in contact mares again will all possibly abort.

SLIDE 14

Management of your brood mares is crucial to prevent or limit the effect that EHV can have on your farm.

The first most important thing to realize is that it is impossible to know if a resident mare is a carrier of EHV until you have that first abortion.

So therefore the management steps you must take is to firstly try to run your mares in several groups of small numbers as compared to one large susceptible group.

The second most imperative thing to realize is that you must attempt to run your pregnant mares as a closed herd with no introductions. If you must introduce new horses then it is important that they are quarantined for at least one month.

It is also very important to realize that young horses are large reservoirs of EHV, and therefore you must limit the contact that your late pregnant mares have with the weanlings and yearlings.

Thirdly you should implement a vaccination program on your farm to decrease the EHV level on your farm.

SLIDE 15

Vaccination is with DUVAXYN which is a combined inactivated EHV!&4. It is apparently the best equine herpes virus vaccine available throughout the world ( according to Angus.)

Use of the vaccine will decrease the virus load on your farm. It is not a guarantee that your mares will not abort if they are faced with overwhelming challenge but it reduces the risk.

Vaccination for pregnant mares involves vaccination on the 5^th/7^th/&9^th month of pregnancy. If the mare has not been vaccinated previously she will need an initial course of 2 shots one month apart.

It is important to vaccinate the weanlings and yearlings as this is the group that is the most susceptible to infection. The weanlings are given an initial shot at 4 months followed by another one month later, and then vaccinated every six months.

SLIDE 16

If you do have an abortion for whatever reason it is important that both you and your staff follow a strict procedure each time until a positive cause of the abortion has been determined. Remember that the foetus and placenta are the most infectious items around when it comes to EHV.

It is imperative that the foetus and placenta are sent to a laboratory for analysis.

All articles that have come in contact with the foetus or placenta should be burned.

The area should be limed and roped off or electric fenced.

All farm personnel in contact should disinfect with a phenol disinfectant and wash boots, change clothing etc before going near any other mares.

There is controversy as to whether the mares should be moved from the paddock or not.

My suggestion would be that if you have a paddock that is isolated that will not introduce infection to a new mob of mares then you should move them out of the infected paddock.. There are a lot of practical implications here and it is really dependant on the individual situation as to what is the best course of action. Just one last comment , it can be a real disaster when a fox drags an infected foetus across into another paddock so it is a good idea to try if possible to have secure fencing around your pregnant mare groups.

SLIDE 17

Now there is another disease a lot of you, especially those of you with thoroughbreds will have heard about or tested for in your pregnant mare groups and that is a disease called Equine Infectious Anaemia or EIA for short.

EIA sprung to prominence last year when a lot of the thoroughbred studs required testing for EIA before accepting the mare to the stud. This was a result of a couple of positive tests on horses in New South Wales.

Now EIA is another highly contagious virus. It is a retrovirus, similar to the AIDS virus in people.

SLIDE 18

It infects the red blood cells of the horse permanently and there is no vaccine or cure for EIA.

It spreads through the blood via mosquito/fly bites and dirty needles, unclean surgical instruments etc.

It causes fever, depression, anorexia, weight loss, anemia, swelling of the limbs, and can also sometimes cause abortion, colic, neurological signs or infertility.

Most horses recover from the initial illness but they remain permanent carriers of the virus in their red blood cells.

Testing for EIA is via a blood test they call the Coggins test.

As I said before there is no vaccine and no cure, and the only option for infected horses is Euthanasia.

SLIDE 19

TETANUS.

The horse is more susceptible to tetanus than any other animal in the world.

For this reason it is imperative that your breeding stock are immune.

Tetanus is caused by toxins liberated from the bacteria Clostridium tetani. Spores from this organism are capable of persisting in the soil for many years. Horses are therefore exposed frequently to the infective form of the bacteria.

TETANUS usually occurs as a consequence of deposition of infective spores in a deep, penetrating wound.

Toxins are released by the bacteria within the wound that travel up the peripheral nerves and cause over stimulation and rigidity until the muscles that are innervated by the effected nerves begin to ‘LOCK’.

Clinical signs that you will see with tetanus may be an initially stiff gait. This might be followed by restriction of jaw movements ( hence the term ‘lockjaw’), prolapse of the third eyelid, and an unsteady gait. The tail will often be held out stiffly. The ears are usually pricked and the horse will sometimes look as if it has a frown on its face.

Eventually if left untreated they will die from suffocation due to paralysis of their breathing muscles.

Treatment can be very difficult.

Prevention is the best cure, and luckily the tetanus vaccine is one of the most effective vaccines available.

SLIDE 20

All horses should be vaccinated initially with 2 shots one month apart with a yearly booster thereafter.

However it is imperative that your broodmares are given a tetanus shot in the last month before they foal so that they can pass some passive immunity to their foal.

It is extremely important that if for whatever reason the mare does not get vaccinated that the foal is given a tetanus antitoxin at birth. Otherwise they are very susceptible to getting tetanus through their umbilical cord.

Likewise if the foal has not gained adequate colostrum it is wise to give the foal a tetanus antitoxin.

SLIDE 21

Strangles will be discussed at length in a later lecture but I would just like to mention the vaccination protocol here.

Basically it is 3 shots 2 weeks apart as the initial course and then repeated every 6-12 monthly depending on the circumstances on the stud.

As with tetanus it is very important that the pregnant mare is vaccinated in the last month before foaling to ensure that she has adequate immunity to pass to her foal.

SLIDE 22

Parasite control is an important management factor relating not only to the general condition of the mare but also to the unborn foal.

Mares should be dewormed on a regular basis using a product approved for use during pregnancy eg benzimidazoles, fenbendazole, pyrantel pamoate, and the avermectins.

Strongyles and ascarids are the main parasites associated with disease in mares and foals. Other parasites such as pinworms, tapeworms, and bots create discomfort but are not usually associated with life threatening diseases.

It is especially important to deworm a mare before foaling to ensure that the foal is not exposed to a high parasite burden. Strongyloides westeri can be transmitted through the milk from the mother so it is important to deworm her with a product that has an effect in her mammary glands such as ivermectin or benzimadazoles.

Because foals practice coprophagy, or eating manure, the transmission of parasites increases.

Pasture management and rotation is an essential part of worm control on a stud farm.

Management practices that enhance parasite control include the following:-

1)routine removal of faeces from stalls, pastures and paddocks

2)Manure not spread on pastures unless it has been composted for one year

3)Regular rotation of pastures and avoidance of overstocking

4)Harrowing pastures during the driest and hottest season of the year

5)Deworming all horses at the same time

6)Deworming all new horses to farm prior to allowing them to intermingle with other horses.

SLIDE 23

The stallions penis always has a normal bacterial flora on its surface. These bacteria, known as commensals, are generally not pathogenic i.e. in general they will no cause uterine infections or fertility problems. All ejaculates will have some bacterial elements.

Bacterial problems can arise when the normal bacterial flora of the penis is altered and colonized by one particular type of bacteria. Alterations in the normal flora mostly occurs as a result of over washing of the penis prior to breeding or washing with surgical scrubs.

SLIDE 24

There are three bacteria that pose a potential problem when they are present in excessive numbers on the stallion's penis.

Pseudomonas aeruginosa, Klebsiella pneumonia, and Taylorella Equigenitalis.

SLIDE 25

Pseudomonas aeruginosa may cause endometritis or vaginal discharge in the mare. Diagnosis can be made by culturing the stallion and the mare and using a fluorescent lamp source .

Mares should be treated post service with the appropriate antibiotics and the stallion can be treated by washing with a very dilute hydrochloric acid.

SLIDE 26

Klebsiella pneumoniae can cause endometritis if the stallion has an overgrowth of this particular bacteria on his penis.

Again diagnosis can be made by culture of the stallion and the mare., and the mare should be treated post service with antibiotics. The stallion again can be treated by washing with dilute sodium hypochlorite.

SLIDE 27

Taylorella equigenitalis is the bacteria that causes Contagious Equine Metritis or CEM. It is not in Australia at present, but it has been in Australia and caused several breeding farms to close for the season in the 70’s.

Taylorella causes a severe endometritis that results in a copious grayish purulent discharge. Early embryonic death and abortions are not uncommon in pregnant mares.

The stallions carrying Taylorella show no clinical signs. The bacteria lives in the urethra and the sheath of the penis, and around the cervix and clitoris of infected mares.

Diagnosis can be difficult and time consuming.

Mares can be treated with daily intrauterine crystalline penicillin infusions and the scrubbing of the clitoris with chlorhexidine., then packing the area with nitrofurazone. Stallions are treated by washing with soap and water, chlorhexidine, and nitrofurazone.

SLIDE 28

Coital exanthema is caused by the equine herpes virus 3. The diagnosis is fairly simple and is performed by examination of the penis where pustules and ulcerations are found. If a mare is bred during this period the disease is transmitted and similar lesions can be found on the vulva and perineal areas. Fertility is not usually affected. However the lesions can be painful and the stallion might refuse to breed over the convalescent period.

The infection is self limiting and resolves in about 3 weeks without treatment.

SLIDE 29

The risk of acquiring infection can be reduced by maintaining distinct groups of horses on your farm. Resident mares and foals should be kept separate from weanlings, yearlings, and visiting mares.

New arrivals should be quarantined for 30 days and monitored for signs of illness .

Vaccinations and worming should also be done as they arrive if there is no history.

SLIDE 30

Foaling mares being sent to another farm for breeding should be transported 6-8 weeks prior to foaling to allow them to develop some exposure and immunity to the pathogens on that farm. This will enable them to protect the foal with their colostrums from the pathogens on that farm.

Mares being walked on likewise where possible should be transported without the foal to reduce the risk of the foal acquiring infection..