Tasty treats pets should avoid (Proceedings)

There have been numerous cases of dogs developing polyuric, oliguric or anuric renal failure within 12-72 hours of ingesting grapes and raisins. Red grapes, green grapes, seed or seedless grapes, vine grapes, grape crushings, and fermented grapes, along with various brands of commercial raisins (including sun-dried), have been implicated. The toxin has not been identified. There appears to be no apparent dose response [at least with respect to the amount of grapes and raisins consumed], and toxic doses have been reported to be as low as 0.7 oz grapes/kg BW and 0.11 oz raisins/kg BW. Most reported cases involve large quantities of grapes and raisins; however, there have been cases where a half dozen grapes was associated with the development of renal disease. In most documented cases of poisoning, pets had been previously exposed to either grapes or raisins with no apparent ill effects.

Vomiting characteristically begins within 2-6 hours of ingestion, followed by depression, anorexia, lethargy and abdominal pain. As early as 12-24 following exposure, clinical pathological abnormalities include azotemia, hyperphosphatemia and hypercalcemia. Patients are typically oliguria or anuric, and isosthenuria with granular casts are commonly observed. Proximal renal tubular degeneration and necrosis, with 33-100% distribution, are the typical lesions, while sparing the distal tubules. The tubular basement membranes remain intact. Mineralization can occur in the kidney, along with other organs.

Decontamination is recommended in cases of recent exposures; emesis, gastric lavage, activated charcoal, cathartic; combined with fluid diuresis (2-3x maintenance) for 48 hours (monitoring BUN, Cr, Ca, P, K, urine specific gravity, etc.). Dogs that present in renal failure often require heroic measures (peritoneal dialysis, hemodialysis), and the prognosis is generally quite poor.

Macadamia nuts have been shown to be toxic to dogs. Estimated toxic doses derived from clinical case reports range from 0.70 to 4.9 g/kg BW - this represents approximately 5-40 whole kernels for a 20-kg dog. Other reports have placed estimates between 2.4 up to 62.4 g/kg BW. Toxicosis was observed experimentally in dogs that received 20 g/kg roasted nuts by stomach tube. The toxic principle has not been identified. Clinical signs are typically seen within 6-24 hours of ingestion, and include weakness [rear limbs more affected than fore limbs], recumbency, depression, vomiting, ataxia, tremors, hyperthermia, joint pain [with or without swelling] and stiffness. Regardless of therapy, recovery is generally complete within 24 hours. The only consistent serum chemistry abnormality seen in the experimentally dosed dogs was elevated lipase concentrations. Decontamination (emesis, activated charcoal, cathartic) should be considered within the first few hours of ingestion. Other treatments are symptomatic and depend on the clinical signs and their severity.

Onions, garlic, chives and leeks [Allium sp.] contain sulfoxide and disulfide compounds that cause oxidative damage to erythrocyte membranes, leading to methemoglobin formation and a Heinz body hemolytic anemia. Toxicity varies with the type and amount of Allium ingested; raw, crushed, cooked and dried Allium can all pose threats to pets. Considering fresh onions contain > 85% moisture, dried forms present greater risks. Cats are more sensitive than dogs, though exposures are more commonly reported in dogs. Toxic doses reported in dogs from the literature vary: 2.4, 5.5 and 15 g dehydrated onions/kg BW; 12.6 g fresh onions/kg BW. Clinical signs in pets, occurring 24-72 hours post ingestion, are directly related to the degree of methemoglobin production and anemia observed: inappetance, pale or icteric mucous membranes, weakness, rapid breathing, rapid heart rate, diarrhea, staggering and collapse. Aggressive use of IV fluids and blood transfusions should be considered; vitamin E may help to stabilize membrane architecture.

Exposure to chocolate products continues to be a problem for pets, though many exposures never lead to any signs. The theobromine and caffeine content of chocolate products varies, and sometimes determining the toxic dose is close to impossible. In general, the more bitter the chocolate, the higher the theobromine/caffeine content.

Type Caffeine (mg/oz) Theobromine (mg/oz)

• Milk chocolate 6 44-56

• Semi-sweet 24 138

• Unsweetened baking 49 393

• Cocoa 72 737

Dogs are particularly sensitive to methylxanthines, with LD50s in the 100-200 mg/kg range. However, mild signs can be observed at exposure levels of 20 mg/kg, moderate effects seen at exposure levels of 40 mg/kg, and severe clinical problems can be seen when exposures reach 60 mg/kg or greater. The most commonly reported clinical signs include tachycardia, hyperactivity, tremors, increased urination, vomiting and diarrhea. Seizures and cardiac arrhythmias can be seen at high exposure scenarios.

Aggressive and early treatment, such as decontamination procedures [activated charcoal, cathartic] and cardiovascular monitoring, coupled with appropriate supportive care [diuresis] generally lead to a positive outcome. Many laboratories can analyze for both theobromine and caffeine in a variety of biological specimens; however, the levels have not been correlated with the severity of clinical signs and can therefore only be used to confirm exposures.

References

Cope RB. 2005. Allium species poisoning in dogs and cats. Vet Med, August, 562-566.

Eubig PA et al. 2005. Acute renal failure in dogs after ingestion of grapes or raisins: A retrospective evaluation of 43 dogs (1992-2002).J Vet Intern Med 19:663-674.

Gwaltney-Brant SM. 2006. Macadamia nuts. In Small Animal Toxicology, Ed. ME Peterson, PA Talcott, Elsevier Inc., pp. 817-821.

Mostrom MS. 2006. Grapes and raisins. In Small Animal Toxicology, Ed. ME Peterson, PA Talcott, Elsevier Inc.,