You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Pica is an abnormal craving to eat something unusual such as soil

In livestock pica is frequently observed when there is mineral deficiency.  Cattle, for example, will eat bones, rocks or bark and this is often a sign of phosphorus deficiency. In sheep potassium deficiency has been reported to result in pica and with excessive hair licking, floor licking and wood chewing. In humans pica has been reported to occur in zinc deficiency.

True pica is an unusual and uncommon sign in small animals, but there are several causes reported in the literature. When dogs eat soil they are predisposed to develop the formation of silica urolithiasis - which have a characteristic "jack stone" appearance. The soil may be ingested along with other material, such as root vegetables or unwashed food eg cabbages, swedes,.

Known causes of pica are :

• Hyponatremia. Sodium deficiency is one of the most powerful drivers for the  ingestion of unusual materials. As the nutritional requirement for sodium is so low, and most foodstuffs contain sodium  it rarely occurs because an animal's ration is deficient in sodium content. The body is extremely efficient at conserving sodium, and workers have found it impossible to induce hyponatremia by feeding a ration with only a trace of sodium. 

Hyponatremia is is defined as serum sodium concentration less than 137mEq/L (Normal range is 140-155 mEq/L) . It is only likely to occur if the normal homeostatic mechanisms breakdown, for example in there is 

• excessive water intake
• inappropriate secretion of antidiuretic hormone (ADH)
• hypoadrenocorticism
• if excessive sodium losses occur due to gastrointestinal disorders
• iatrogenic losses occur following the administration of diuretics
• dilution occurs due to the administration of hypotonic fluids.

Other signs of hyponatremia include :

• Slow growth in young
• Impaired milk production in postparturient animals
• Weight loss
• Fatigue and weakness
• Polyuria
• Seizures

• Hepatic encephalopathy. Pica is an unusual manifestation of hepatic encephalopathy and it is accompanied by polyphagia. Presumably this is a behavioural response to functional  failure of the liver producing a state of "metabolic starvation", or it could be due to secondary effects on the brain.

• Zinc poisoning Persistent pica has been described in a dog that repeatedly swallowed North American pennies containing a high percentage of zinc, and which often licked brass objects. This relationship is feasible as zinc is known to affect the sense of taste.

Feedback request : The true incidence of pica in small animals is not known. . If you would like to participate in a Provet Survey please send the clinical details of any cases that you see to feedback@provet.co.uk  Thank YOU.

Last updated : October 2013