SouthWest Equine Medical and Surgical Center Raising the Standard of Equine Veterinary Healthcare in Arizona

Featured Case of the Month - "Lacy"

Signalment:
10-year-old Quarter Horse mare

History and Presentation:
Lacy was referred to SWEMSC with a history of colic signs and lethargy of one-day duration.

Physical Examination: At presentation, Lacy was not exhibiting overt signs of colic but was moderately depressed.

	Her heart rate was ausculted (with a stethoscope) and found to be elevated (82 bpm), but her palpable pulse was weak and the rate was only 42 bpm. This finding is termed a pulse deficit, meaning there is not a pulse felt for every heartbeat.
	Her heart rhythm was also irregular indicating a cardiac arrhythmia, or an abnormal timing of expected heartbeats.
	Lacy's gums were dry and darkened. This is a consistent finding in dehydrated and toxic horses.
	Minimal gut sounds were audible, but a small amount of normal feces was passed during her examination.
	Rectal examination and nasogastric intubation (aka stomach tube) did not reveal any significant abnormalities.
	Physical exam findings generated a broad differential diagnosis list including, gastrointestinal disease, cardiac disease, and toxicosis.

Due to the nature of the clinical signs, oleander (Nerium oleander) toxicity was highly suspected.

Diagnostics:

Blood work was drawn and indicated that Lacy was dehydrated. A stress leukogram was present as well (white blood cell parameters that are consistent with the bodies response to any stressful event). An electrocardiogram (ECG) was performed due to the pulse deficit and cardiac arrhythmia noted on the physical exam. An ECG records the electrical activity of the heart, however, does not specifically indicate a certain disease. Results of the ECG tracing confirmed the arrhythmia. Moderately severe electrical activity abnormalities were noted, including ventricular premature complexes (VPC's), junctional beats, and ectopic beats.

Figure A. is a normal ECG tracing from a horse.
Figure B. is a copy of Lacy's ECG tracing shortly after admittance to SWEMSC.

Following confirmation of cardiac abnormalities a cardiac echocardiogram (an ultrasound of the heart) was performed to rule out any developmental or visible problems within the soft tissues of the heart. Samples of her feces and blood were submitted for isolation of the oleander toxin.

The day following admittance, the owner reported that a source of oleander had been located near Lacy's pen. Results of the fecal analysis revealed the presence of Oleander toxins and subsequently confirmed the diagnosis of oleander toxicosis. Lacy's blood work also indicated she was in acute kidney failure as evidenced by increased blood urea nitrogen and creatinine levels (elevations due to reduced filtration by the kidneys). Lacy was also at an elevated risk of developing gastric ulcers due to her prolonged anorexia as a result of the toxicant. For this reason, gastroscopy (a specialized video camera passed from her nose and into her stomach) was performed to be certain her stomach lining was not compromised. Results of the gastroscopy revealed no abnormal findings within the stomach, including gastric ulcers.

Therapy:

Lacy's treatment regimen was made up mostly of supportive care and stabilizing her condition until she could clear the effects of the oleander toxins. Toxin absorbants were given via stomach tube to reduce the amount of toxin that continued to be absorbed from her digestive tract. The absorbant was regularly administered over three days due to enterohepatic recycling of the toxins released from the oleander. Aggressive intravenous fluid therapy was initiated to combat her dehydration, kidney failure, and promote excretion of the toxins from her body. During her stay, Lacy received 110 liters of balanced fluids intravenously. Anti-inflammatories were given to reduce the damage of the toxemia and help Lacy feel better while the treatment took effect. Due to the risk of bacterial infection following a toxic insult, antimicrobials were started as a precaution.

Recovery:
Lacy slowly improved over the following several days. She began eating and developed mild diarrhea due to the toxin absorbent and orally administered protectants. This was short-lived and resolved in a couple days. Her blood work was checked daily to be certain that her kidney and other body systems were working properly. Laminitis is always a concern when horse becomes systemically ill and toxic, however Lacy did not develop any clinical signs of laminitis during her stay at the hospital. Eventually her blood work and physical exam findings allowed her fluid therapy to be stopped. General nursing care was continued until she was able to return home.

Six weeks following her discharge from the hospital, Lacy's blood work, urinalysis, and ECG tracings revealed she had made a full recovery.

Horse Owner Education:

Lacy's case is a reminder to all those who deal with horses in Arizona.

Oleander (Nerium oleander) toxicosis has been associated with fatal arrhythmias and sudden death in horses. Early clinical signs following ingestion of toxic doses of Oleander can range from any variety of abnormalities that can easily be confused with GI disease (colic), cardiac disease, nervous system diseases (encehaplitis), other toxic ingestions (Blister Beetle), renal disease (kidney failure), or musculoskeletal disease (Tying-up).

The plant comes in a variety of sizes, colors, and is virtually everywhere in the Phoenix area. The plant is toxic when fresh or dry, thus hedge clippings containing dry oleander leaves are considered the number one cause of oleander toxicosis in horses. The dry leaf is less irritating to the mouth and appears to be inadvertently consumed if mixed with hay, as in cases with high wind. The lethal dose of oleander in horses is 0.005% of bodyweight.

Often, well-meaning owners underestimate or are unaware of the very serious and life-threatening effects of oleander ingestion.