Vitis species: Grape

Family

Vitaceae

Common Names

Grape, grape vine.

Plant Description

A genus of about 65 vines or shrubs found in many regions of the Northern Hemisphere, Vitis is best known for Vitis venifera, the wine grape. Numerous cultivars of this species are the basis for the varietal wines available today. A frost-hardy, woody, deciduous vine with tendrils opposite the leaves, and large 5 - 7 lobed, to heart shaped leaves. Inflorescences are produced in leaf axils and consist of clusters of small greenish-white, 5 petalled flowers. Fruits are drupes, with or without seeds, that turn blue-black or yellowish-green when ripe (Fig. 399 and Fig. 400).

Figure 399. Vitis venifera.

Figure 400. Vitis venifera.

Toxic Principle and Mechanism of Action

The toxin present in grapes or raisins responsible for the syndrome of poisoning in dogs has not been determined [1-4]. Tannins in the grapes and raisins, fungal mycotoxins in the grapes such as ochratoxin, and pesticides that may have been sprayed on the grapes have been postulated as a possible cause for acute renal failure seen in dogs, but no evidence to date has been found to incriminate these compounds [3,4]. The high glucose and fructose content of grapes (12%) and raisins (40%) suggests that dogs may be unusually sensitive to monosaccharides or compounds that interfere with sugar metabolism, and the syndrome may be due to the high sugar intake affecting kidney function [5]. There is considerable variation in the susceptibility of dogs to grape and/or raisin toxicity. In one series of suspected grape or raisin toxicity in dogs the amount of grapes consumed was 12 - 31gm/kg body weight [3]. The toxic dose of raisins is 0.1oz/kg body weight.

Risk Assessment

Dogs that have eaten grapes or raisins they have been fed in the household are at greatest risk. Consumption of grapes off of the vines directly by dogs can lead to toxicity. Toxicity does not appear to be related to the variety of grape, or brand of raisin consumed.

Clinical Signs

Vomiting within 24 hours of consuming grapes or raisins is the initial presenting sign in dogs [3,4]. Even though it would appear most or all of the grapes or raisins have been vomited, vomiting continues for several hours and leads to dehydration, weakness, and collapse. This is followed within a short period by signs of acute oliguric or anuric renal failure. Increased blood urea nitrogen (BUN), and creatinine, hyperphospatemia, and hypercalcemia are generally present within 48 hours of ingesting the raisins ir grapes [5-7].

Severe, diffuse, tubular necrosis is often detectable on renal biopsy.

Successful treatment of raisin or grape poisoning requires early recognition and aggressive monitoring and appropriate therapy to maintain renal function. If the grapes or raisins have been consumed in the past 2 hours, vomiting should be induced, and activated charcoal administered orally. Dogs should be put on intravenous fluid therapy, and closely monitored since dogs with a history of ingesting grapes or raisins are often in acute oliguric or anuric renal failure when they are presented for treatment, caution must be taken when administering intravenous fluids as the dogs can quickly develop pulmonary edema. Peritoneal dialysis may be necessary and life saving [6,7].