Equine Health Topics
Insulin Resistance by theHorse.com
Horses fed diets high in sugar or starch are more likely to be insulin resistant even if they are not obese.
Insulin resistance is a reduction in the sensitivity to insulin that decreases the ability of glucose to be transported into the body's cells from the bloodstream. While the body can compensate for a short period of time by increasing insulin production and secretion to maintain normal blood sugar levers, the end result is abnormally high circulating levels of glucose. Insulin resistance has become a hot topic in the equine news front of late, but has likely existed (undiagnosed) for many years.
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- Insulin resistance is defined as a decreased sensitivity of the horse's cells to insulin resulting in an increased blood sugar level.
- Contributing factors are thought to include diet, body condition, age, and breed.
- Common clinical signs include weight gain or loss, muscle loss, development of a cresty neck, regional deposition of fat in areas such as the tailhead, behind the shoulder or over the loin; lethargy and chronic (recurrent) laminitis.
- Diagnosis is challenging and involves measuring insulin and glucose levels in the blood.
- There is no specific treatment or cure for insulin resistance. Diets and exercise are important for limiting development and prevention of worsening of insulin resistance in horses.
Failure of Passive Transfer by theHorse.com
When foals don't get enough of their necessary antibodies from their dams, it is called failure of passive transfer.
Newborn foals are born with virtually no infection-fighting antibodies. Foals obtain these antibodies, also referred to as immunoglobulins, from their dam's colostrum - a special type of milk that is produced by the mare during the last one or two weeks of gestation. Most foals nurse from their dams and obtain at least 1 liter of good quality, antibody-rich colostrum within the first eight hours of life. This process by which mares pass antibodies on to their foals via the colostrum is referred to as passive immunity. Then foals don't get any or enough of these important antobodies, it is called failure of passive transfer.
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- Within 4-6 hours after birth, a foal should stand and nurse from its dam to ingest and absorb the antibodies (immunoglobulins) that are in the mare's first milk called colostrum.
- This process is referred to as passive transfer of immunity.
- Foals that fail to nurse or are unable to absorb the antibodies are classified with failure of passive transfer.
- Failure of passive transfer is diagnosed based upon a veterinarian's examination and a blood test that measures a foal's immunoglobulin (IgG) levels.
- Foals with IgG levels less than 800 mg/dl are considered to have either a partial or complete failure of passive transfer.
- Foals with failure of passive transfer can be treated with either fresh or frozen colostrum, a commercial form of IgG, or by the intravenous adminsitration of plasma products that are high in concentration of immunoglobulins.
- Prognosis of foals with failure of passive transfer is variable; however, good foaling management strategies can help prevent many cases of failure of passive transfer.
Cushings by theHorse.com
By far the most common manifestation of Cushing's is an abnormal haircoat.
Equine Cushing's Disease, Equine Cushing's Syndrome, hyperadrenocorticism, pars intermedia pituitary adenoma (PIPA), and pituitary pars intermedia dysfunction (PPID) are all terms used to describe horses with an endocrine (hormonal) disorder. This disorder involves production of very high levels of cortisol and cortisol like hormones, which are steroids that are known as a "stress hormones". They have wide reaching effects throughout the body such as increasing blood sugar (glucose) levels and suppressing the immune system.
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- Cushing's is a hormonal disease of horses most often caused by a benign tumor of the pituitary gland that results in the production of very high levels of cortisol and cortisol like hormones.
- High levels of cortisol and coritsol like hormones are responsible for the preponderance of the cliniclal signs observed in equine Cushing's patients, including a long wavy coat, sway back appearance, muscle loss, an increase in drinking, eating and urination, recurrent respiratory disease, and chronic or recurrent laminitis.
- A variety of tests are available to assist in achieving a definitive diagnosis, especially in horses with subtle clinical signs.
- There is no cure for Cushing's. Drug therapy and husbandry play an important role in the management of affected horses to help them live as long and as comfortable as possible.
Anthelmintic Resistance in Horses by Dr. David Pugh, DVM, MS, DACT, DACVN
With respect to equine parasite control, many of the older ideas are no longer valid. Large strongyles have been eradicated from most horse farms. Small strongyles (cyathostomes, cyathostomins) are not the most significant pathogenic internal parasite of horses in North America. Larval stages of cyathostomes encyst in the colonic mucosa and may cause pathology upon emergence from the mucosal cyst. The damage to the bowel from larval emergence is magnified when large numbers emerge simultaneously.
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Rhodococcus equi by theHorse.com
Depressed foal can be warning sign for Rhodococcus
Rhodococcus equi is well known for its ability to cause severe pneumonia in foals one to six months age. In addition, R. equi can cause septic arthritis (infection of the joints), osteomyelitis (infection of the bones), neonatal diarrhea (enterocolitis), abdominal lymphadenitis (inflammation of the lymph nodes), spinal cord abcesses, and immune-mediated disease such as polysynovitis. It can also cause sudden death in foals that appear to be healthy.
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- R. equi is best known for the severe and devastating pneumonia it causes in young foals between one and six months of age.
- Most foals are exposed to this ubiquitous, soil-dwelling bacterium, yet not all foals develop disease.
- Ingesting or inhaling the bacteria from the soil, dirt, or fecal particles is the primary route of entry in foals. R. equi then invades macrophages in the lung, which are a special type of white blood cell that normally kill bacteria.
- Affected foals rapidly develop fever, lethargy, a mucopurulent nasal deishcarge, an increased repiratory rate, and respiratory distress.
- Diagnosis is challenging and is dependent on clinical signs, evidence of lung abcesses on radiographs, and isolation of R. equi from a transtracheal wash.
- Treatment consists of a variety of antibiotics, including a combination of rifampin and erythromycin.
- No vaccine for R. equi is available. Prevention is aimed at management of sanitation strategies and administration of hyperimmune plasma to foals shortly after birth.