Keeping Foals Healthy

Author – Erica Hutten (DVM – Genesee Valley Equine Clinic)

By the time a foal is on the ground, considerable resources have already been invested in buying the breeding, achieving the pregnancy, prenatal care of the mare, and foaling out.  Foals, like human neonates, are uniquely susceptible to a variety of diseases that are found in their environments.  In order to prevent financially or emotionally devastating foal losses, it is important to do all we can to prevent disease in our foals.  Good management is critical to achieving this goal.  Here are a few management tips for reducing disease in foals:

Disinfection of foaling stalls:

Foaling stalls should be cleaned and disinfected between foaling mares.  Remember that disinfectants are inactivated by manure and organic debris, so stalls must be spotless before disinfection.  Phenolic disinfectants (Tek-trol®, One Stoke Environ®) may be superior to bleach, because some pathogens (Rotavirus, for example) are not killed by bleach.

Bedding:  Use of sawdust for bedding, particularly for very young foals, is a risk factor for foal diarrhea diseases.  Straw should be used instead, at least for the first week.

Mare cleanliness:  Foals are exposed to large numbers of pathogens during udder-seeking.  These are ingested, and can lead to septicemia or diarrhea- potentially fatal diseases.  There is good evidence that washing the udder and perineum (hindquarters near the anus and vulva) of the mare and wrapping up the tail before the foal begins trying to nurse significantly decrease the pathogen load ingested by the foal.

Umbilical care:  The stump of the umbilicus (navel) is another potential portal for disease in foals.  Umbilical treatment should start as soon as the cord has ruptured, and dipping should be repeated several times in the first 24 hours.  Dipping should not continue after the stump dries.  There is considerable debate among horsemen about the best substance to use for dipping.  Recent studies have proven that dilute chlorhexidine (Novalsan®) is most effective in reducing bacterial colonization of umbilicus.  Strong iodine and other caustic solutions should be avoided for several reasons.  These substances can cause burning and damage of the surrounding skin, which may predispose to local infections, patent urachus, and other problems later on.

Colostrum consumption:  Colostrum is the first milk, and contains antibodies which are critical for the survival of the foal, who is born with no immune protection of its own.  At birth, the lining of the foal’s digestive tract is “open” to allow absorption of these proteins.  (It can also allow passage of dangerous bacteria!)  The gut “closes” at about 24 hours of age, so it’s essential that colostrum is consumed early.  In addition, there is recent evidence that bottle-feeding 2-4 oz. of colostrum milked from the mare as soon as the foal has a suckle reflex can help protect the gut from bacteria ingested during udder-seeking.  All foals should have blood drawn for an IgG test between 12 and 24 hours of age.  This is part of routine neonatal exam, which should be done by your veterinarian for each birth.  If IgG is low, foals are very likely to succumb to disease within the first week of life.  These foals can be saved with a plasma transfusion if they are detected early.

Even with excellent management, some foals do become ill, so be sure to monitor all neonates closely, and investigate any abnormalities quickly.  Veterinary intervention should be sought sooner rather than later for any foal problem, since they can quickly become critical.

Equine Herpes Virus
Prepared by Dr. Robert Hillman, DVM
(Genesee Valley Breeders Association Board Member)

            The recent outbreaks of neurologic Equine Herpes Virus type 1 have generated renewed interest in this disease. Equine Herpes Virus type 1 is primarily a respiratory pathogen associated with a variety of clinical signs in horses. Clinical signs can include high fever, nasal discharge, abortion, neurological signs and death. Neurologic signs include weakness, ataxia, urinary bladder atony and reduced tail tone. In severe cases, horses will be unable to stand and have a very guarded to poor progress. EHV-1 is enzootic throughout the world and almost all horses over 2 years of age have been exposed with most showing minimal or no clinical signs. Following initial exposure, EHV-1 has the ability to reside in a horse as a silent, persistent infection which can serve as a reservoir of virus for continual transmission in times of stress.

            The widely publicized outbreak of neurologic Equine Herpes Virus type 1 that occurred in late 2006 involved a shipment of 15 horses from Germany. The horses arrived at the New York Animal Import Center in Newburg, NY where they were kept together in federal quarantine. While there one of the horses developed a fever, was treated and displayed no clinical signs of illness before it and the others were released from quarantine. Horses in federal quarantine are not tested for EHV as it is not a foreign disease.

            Eight states received horses from this group of horses. California received a horse that died shortly after arrival of a laboratory confirmed case of equine herpes virus. Florida received 5 horses which resulted in 13 horses identified as infected.  Seven of the horses showed neurologic signs and 6 died or were euthanized. Ten premises in Florida were quarantined. Horses sent to the remaining 6 states were identified, quarantined and closely monitored for at least 3 weeks. No signs of illness were noted and all quarantines have been lifted.

            Additional outbreaks of neurologic EHV1 have been recorded throughout the country that has no association to any of the imported horses. Two horses died at Los Alamitos Race Course in California in late January resulting in 2 barns being quarantined. An equine herpes outbreak at University of Connecticut spread to 21 of their 72 horse herd with 5 showing neurologic signs. All are expected to recover. Ten horse facilities and Quantico Marine Base were quarantined in northern Virginia following exposure to a horse that tested positive to EHV after surgery at Marion DuPont Equine Medial Center in Leesburg. Three of these horses have shown neurological signs of EHV-1 with one being euthanized and tests on six other horses are pending.

            At this time there have been no recent confirmed cases in New York State.

            Prior to 2003 reports of neurologic EHV-1 outbreaks were sporadic. Four out-breaks were reported in 2003. In 2005, 7 outbreaks were reported in 5 states. In 2006 the number of reported outbreaks grew to 11 and involved 8 states. As the number of outbreaks has increased, the number of animals infected in an outbreak appears to be much higher than has been seen prior to 2001.

             The increased reports of neurologic EHV-1 in recent years may be due to a mutant strain. The result of this mutation is that the virus can reproduce rapidly with a predilection for nervous tissue producing a viremia that occurs earlier, reaches a higher peak and lasts longer. The progression of the disease in a population as well as in individual cases appears to be much more rapid then in the past. Response to currently available vaccines for EHV-1 does not appear to be strong enough to protect all immunized animals against the disease induced by the mutated strain of EHV-1. In some outbreaks well vaccinated populations of horses have experienced severe disease with some fatalities. Similar outbreaks have occurred in unvaccinated populations. The isolation of the mutant from of EHV-1 has raised hopes of including it in a new vaccine which will have increased effectiveness against the neurologic form of EHV-1. While neither killed virus vaccines nor modified live virus vaccines for EHV1, will provide 100 % protection from the respiratory, abortion or neurological forms of EHV1, recently reported studies by Dr Klaus Osterrieder at Cornell University indicate that the modified live virus vaccine appears to afford better protection from the neurologic form of EHV1.

            The economic impact from this disease includes not only the value of horses that die but the costs associated with treatment, quarantines, cancelled events and the inability of horses to compete in events. The threat of this disease emphasizes the need to implement and maintain strict biosecurity measures in day-to-day procedures to prevent the introduction and spread of infectious diseases.