Enterotoxemia in Pet Rabbits and other Herbivores

By Elisabeth Simone-Freilicher, DVM, DABVP (Avian practice)
www.angell.org/avianandexotic
avianexotic@angell.org
617 989-1561

Any practitioner who treats herbivores regularly has encountered the dreaded “flat rabbit” emergency. The patient presents recumbent, weak and dull, possibly with pale mucous membranes, dyspnea, and usually with hypothermia. This presentation is usually caused by a severe imbalance (dysbiosis) in cecal bacterial flora, resulting in an overgrowth of anaerobic spore-formers that produce enterotoxins causing diarrhea and shock. Any delay in treatment may be rapidly fatal.

The patient’s signalment can vary widely. The condition can affect any small herbivore, of any age and either sex. The history is usually surprisingly uniform: a sudden onset of weakness and lethargy, occasionally preceded by diarrhea, and often by several days of decreased appetite and fecal output.

On physical examination, the patient’s lethargy and weakness may be temporarily masked by the patient’s adrenaline surge. (It is important to remember that animal hospitals are unusually stressful places for small herbivores, as the hospital environment often surrounds them with the sight, sound, and scents of their natural predators.) Rabbits and guinea pigs may present with a temperature of less than 100 degrees Fahrenheit (under 99 degrees in chinchillas). Abdominal palpation may reveal a full and doughy stomach, similar to that of gastrointestinal tract stasis, or a distended, fluid-filled, or gaseous cecum. Mucous membranes may be pale. Respiratory effort may be increased, especially when there is abdominal discomfort.

At this point I usually keep diagnostics to a minimum. A systolic blood pressure is taken, and if lower than 40 mm Hg, shock is diagnosed, with no further diagnostics performed until the patient is stabilized.

An intravenous catheter is invaluable here. If intravenous access cannot be obtained without undue stress to the patient, warmed subcutaneous fluids are given (LRS at 100-150 mL/kg), and the patient is placed on heat. In extremely hypothermic cases, a warmed blanket may also be placed over the patient. As the fluid is absorbed and the patient is warmed, an intravenous catheter is reattempted; if impossible, an intraosseus catheter placed in the humerus or femur may also be used.

Once intravenous or intraosseus access is obtained, the following protocol is used, adapted from Marla Lichtenberger, DVM, DACVECC.

1) Crystalloids- 10-15 mL/kg IV

Hetastarch- 15 mL/kg IV over 15 minutes

Recheck blood pressure.

If <40 mm Hg, repeat.  If <40mm Hg after second bolus, go to step 2.

If >40 mm Hg, go to step 3.

2) Hypertonic Saline- 3 mL/kg over 10 minutes

Hetastarch- 3 mL/kg IV over 15 minutes

Crystalloids- 4 mL/kg/hr IV

Recheck blood pressure.

If <40 mm Hg, rule-out hypoglycemia or heart disease

If >40 mm Hg, go to step 3.

3) Warm aggressively including IV crystalloids until systolic blood pressure is greater than 90 mm Hg. If blood pressure drops below 40 mm Hg, return to step 1.

Once the patient is stable, treatments are administered to reduce and correct enterotoxemia. This is similar to treatment in the early enterotoxemic small herbivore, which may present with hypothermia, diarrhea (with or without mucous), but is not weak and in shock. Treatments often need to be given slowly or in stages to avoid stressing the fragile patient. Therefore, our first treatment is usually toxin chelation: cholestyramine, available from human or equine pharmacies. One packet is mixed with 40mL tap water, and syringe-fed at 12cc every 12-24 hours (6cc in chinchillas and guinea pigs). This is followed by antibiotics to decrease the population of cecal spore-forming anaerobes: subcutaneous procaine penicillin G in rabbits (70,000 IU/kg every 48 hours), or oral or injectable metronidazole or chloramphenicol in chinchillas and guinea pigs. Commercial rabbit probiotic is administered, or fecal pellet feeding from a healthy conspecific (preferably from the same household) in chinchillas and guinea pigs.

Once the patient is stable enough to tolerate further diagnostic testing, a complete blood count and chemistry panel as well as radiographs may be performed.  Any additional diagnostics are generally deferred until the patient has been stable and normothermic for at least twenty-four hours.

Although some patients will respond quickly to the above treatments, for those that do not respond quickly, the prognosis is guarded to grave. Once the enterotoxemia has resolved, small herbivores very rarely progress directly to normal gastrointestinal motility, and treatment for ileus should be anticipated as the next step on the road to recovery.

For more information about Enterotoxemia or Angell’s Avian and Exotic service, please call 617 989-1561 or e-mail avianexotic@angell.org.