From Denise Hatakayuma, Chair, Health & Longevity Committee
(Taken from BLOATNOTES, News from the Canine Gastric Dilation-Volvulus Research Program, January 1998).
Of the 1,989 dogs of different breeds enrolled in Dr. Larry Glickman's bloat study, 303 were Newfoundlands. After initial enrollment, the owners of the Newfs were to complete a Current Status and History Questionnaire for each of their dogs enrolled. The response rate of Newfoundlands was 88 percent of the total, or 266 Newfoundlands. Follow-up postcards were also to be completed in January and February of 1998. Preliminary results of data analysis should be available by the summer. Please remember to answer follow-up questionnaires.
There has been a dramatic increase (approximately 1500 percent) in the frequency of bloat (gastric dilation with or without volvulus) in dogs admitted to veterinary teaching hospitals between the years of 1964 to 1994, a rise from 0.036 percent to .57 percent of all dogs admitted. The data was collected from the Veterinary Medical Data Base (VMDB), a computerized multihospital record system. If the rise were due to the increasing popularity of large dogs, susceptible to bloat, the bloat prevalence rates for specific breeds should remain constant. If there were some environmental change responsible, the rates for specific breeds would be expected to increase in parallel with the overall rate for all dogs.
The VMBD records were re-analyzed. First, the diagnostic criteria were limited to dogs with gastric torsion (volvulus), based on radiographic and/or surgical evidence. Next, the analysis was limited to the years 1975-1996. There was a similar pattern of increase for 2,975 dogs with gastric torsion throughout the late 1970s. The overall frequency of gastric torsion rose from 0.06 percent of all dogs admitted in 1975 to 0.31 percent of those admitted in 1995, an increase of more than 500 percent.
When breed specific prevalence rates were plotted for Great Danes and Irish Setters, two high- risk breeds, results showed similar increases. Among 479 Great Danes, the rate rose from 0.91percent in 1975 to a peak of 0.33 percent in 1991, while the rate among 228 Irish Setters rose from 0.22 percent in 1975 to a peak of 3.25 percent in 1994. There was an increasing trend over time, despite year-to-year fluctuations, which were evident in all breeds, even in breeds with fewer dogs suffering from bloat. These patterns indicate an unknown environmental cause, rather than changes in popularity of higher risk breeds.
Some useful information for Newf owners concerned about bloat can be learned from a study on survival and recurrence of bloat. Highly significant factors influencing survival are the condition of the dog on arrival at the hospital, and the presence of gastric necrosis at surgery. Points to remember: In general, once dogs make it to surgery, chances of surviving in the near term are about 85 percent. Therapy for shock and gastric decompression are only first aid for dogs with bloat. Some form of gastropexy is needed to prevent a recurrence. After gastropexy, bloat recurrence is rare and most dogs lead normal lives. The overall fatality rate of bloat has stabilized to about 30 percent.
Age of Bloat Onset
The risk of bloat seems to increase as dogs grow older. A retrospective study conducted on VMDB data from 12 teaching hospitals between 1980 and 1989 showed that 78.8 percent of the dogs were at least four years old before they bloated. The risk was more than twice as high in dogs 7.0 to 9.9 years than in dogs 2.0-3.9 years old, and more than three times higher in dogs 10 or older. In a case-controlled study of 101 dogs with bloat, treated between January 1992 and June 1995, the mean onset was 6.9 years (standard deviation + / - 3.2 years). In a study conducted in the Netherlands between 1984 and 1989, the mean age of onset was 6.8 years (range 10 months to 13.6 years). An age of onset ranged from 1-17 years in a study of 134 dogs conducted by the School of Veterinary Medicine in Hanover, Germany, from January 1988-ApriI1991, with 70.2 percent of the dogs being 7-12 years old at onset. The Norwegian College of Veterinary Medicine in Oslo, Norway reports an average age of 7.2 years (range 1-15 years), with 58.3 percent of the dogs being 6.1-12 years old when they bloated.
More Bloat Studies
A family of Irish Setters is being studied by geneticist Dr. Robert Schaible and breeder Jan Ziech to attempt to better understand the genetic influences on bloat, which can cluster within certain families (familial bloat), or occur in unrelated animals (sporadic bloat). In Irish Setters the pattern suggested that incomplete dominance of a major gene is the mode of inheritance of chest depth/ width ratio, which seems to support the hypotheses that dogs with a deeper chest relative to width are at a greater risk of developing bloat than dogs of the same breed with smaller chest depth/width ratios. The bloat researchers at Purdue are exploring the feasibility of conducting a radiographic study that would offer insight into the role of the esophageal anatomy and function in chronic bloat, which might offer some insight into the role of the esophagus in acute bloat. Drs. Van Slujis and Wolvekamp, at the University of Utrecht in the Netherlands, previously described six dogs with chronic multiple episodes of gastric dilation in which aerophagia (swallowing air) appeared to be a habit and a cause of their illness. The authors subsequently studied 15 dogs suffering from recurrent gastric-dilation volvulus (GDV), and concluded, "recurrent GDV may be associated with abnormal esophageal motility and that impaired transport of food through the esophagus may induce aerophagy."