||B L O A T N O T E s|
News from the Canine Gastric
Dilatation-Volvulus Research Program
School of Veterinary Medicine,
Purdue University, W. Lafayette IN 47907-1243
Phone: (317) 494-6301 FAX: (317) 494-9830
EPIDEMIOLOGY PROGRAM RESEARCH TEAM
Department of Veterinary Pathobiology
Larry Glickman, VMD, DrPH
Diana Schellenberg, MS
Department of Veterinary Clinical Sciences
Gary C. Lantz, DVM
William R. Widmer, DVM, MS
Center for Applied Ethology & Human-Animal Interaction
Nita Glickman, MS, MPH
Bloat Prevention Emerging from Case-Control Study
Analysis is nearly complete for the Practitioner-Owner Case-Control Study of Risk Factors for Canine Gastric Dilatation-Volvulus (CGDV; bloat). In that study, veterinarians identified dogs with bloat (cases), and each was matched with a dog without bloat (control) of the same breed (or similar weight if a mixed breed) and age (_2 years). Control dogs usually had a disease other than bloat, but some had no disease. Owners were interviewed about diet, exercise patterns, etc. Univariate analysis of data from 101 pairs provided some clues to factors which predispose dogs to bloat or precipitate onset of a bloat episode.
Most (93) of the pairs were purebred. Breeds represented by at least 4 pairs were Great Dane (18 pairs), German Shepherd (14), Doberman Pinscher (9), Standard Poodle (8), Golden Retriever (6), Rottweiler (4), Akita (4), and Shar-Pei (4). The mean age at bloat onset was 6.9 years. The 101 cases included 50 males and 51 females. and controls, 39 males and 62 females.
Dietary factors which appeared to increase risk were fast eating, fewer meals per day, less canned dog food, less table food, and fewer snacks between meals. Several suspected dietary factors did not increase risk, i.e., there were scarcely any differences between cases and controls. These included consumption of dry dog food (almost every dog did); amount of dry dog food consumed; consuming dry dog food that had not been moistened before feeding; and nutritional supplements or vitamins (few dogs received them).
Personality traits associated with an increased risk included being fearful or showing aggression to people or other dogs. In contrast, dogs characterized by their owners as happy were at decreased risk.
Dogs with a history of belching or flatus were at increased risk. However, a prospective study is needed to find out whether abnormal gastrointestinal function truly precedes bloat onset or the symptoms reflect the owner's recall bias.
Non-dietary factors not associated with higher risk included exercise patterns; sharing a household with other dogs or with cats (which is consistent with the non-infectious nature of bloat); pre-existing disease; drug treatment; and recent vaccination. Puppy vaccination history could not be assessed for these pet dogs.
The time of bloat onset was between 6 p.m. and midnight in 51 (59.3%) of the 86 cases in which it was reported. This is consistent with veterinarians_ clinical impressions that bloat often occurs at night. We attempted to identify factors during the 8 hours before bloat onset which might have precipitated the episode. The most notable association was with stressful events. However, in most cases the owner did not recall a stressful event, and those events that were described are hard to interpret. Also, in this type of study there is always a concern that the owner's recall of a factor like stress for a dog may be influenced by dealing with the disease and its aftermath.
Other precipitating factors were a change in feeding time and a bigger meal than usual. The latter finding is consistent with the dietary predisposing factor of less frequent meals.
Multivariate analysis, which takes into consideration several factors at the same time, is still being completed for these data. The factors with the strongest associations will be studied in more detail in the prospective study just beginning.
Thanks to all! This study would not have been possible without the 27 veterinary clinics that provided medical data on the cases and controls and the owners who patiently answered the interview questions.
Wanted - Speed limit! How do you slow down a fast eater?? If you have found a practical method to slow
your dog's rate of eating, we would like to hear about it. Also, please let us know if it is OK to publish your idea in a future issue of BLOAT NOTEs Write to: Diana Schellenberg, Bloat Research, VPTH 101, Purdue University School of Veterinary Medicine, West Lafayette IN 47907-1243.
Now Starting: Prospective Study of Bloat Risk Factors in Purebred Dogs
Planning and preparations are at fever pitch for the new prospective study of bloat risk factors in purebred dogs. The main purposes of this study can be summarized as:
Measure the incidence of bloat in several large and giant pure breeds;
Determine the relationship between body conformation, particularly the depth/width ratio of the chest and abdomen, and risk of bloat in individual dogs within a breed;
Evaluate the influence of family history of bloat on risk in individual dogs;
Evaluate effect of diet and personality characteristics as predisposing factors.
The study as originally proposed included 4 breeds at high risk of bloat: Great Danes, Irish Setters, Saint Bernards, and Standard Poodles. The original study is being supported by Morris Animal Foundation, the American Kennel Club Canine Health Foundation, breed clubs, and individual donors. The AKC Canine Health Foundation and national breed clubs are co-sponsoring the addition of 6 breeds to the study: Akitas, Bloodhounds, Collies, Irish Wolfhounds, Rottweilers, and Weimaraners.
Data collection begins at dog shows (usually breed specialties), where the dog is measured and the owner records basic information, including whether the dog or any of its first-degree relatives has had an episode of bloat. After the show, owners will be asked to complete a written questionnaire with detailed information about the dog's diet and personality characteristics. Each dog will be followed for up to 2 years to find which ones bloat. The prospective design is the only way to actually measure age-specific incidence of bloat in a breed, and offers other powerful advantages such as decreasing recall bias.
We hope to obtain data on up to 250 dogs per breed. Irish Setters measured at the 1994 national specialty and Great Danes measured at specialties in 1994 and 1995 will be included with dogs enrolled at 1996 shows.
After data obtained at the shows has been analyzed, each of the 10 participating national breed clubs will receive the first summary of results. This will include (a) prevalence of a bloat history in the dogs enrolled at the show,
relationship between body measurements and a previous bloat episode, and (c) relationship between family history of bloat and history of bloat in an individual dog. After data from the 2-year study are analyzed, each participating breed club will receive a summary of all data pertinent to that breed, including the incidence of bloat in that breed, and breed-specific risk factors. Combined data will be published in the veterinary medical literature.
The Purdue research team can travel to the shows, measure dogs, and collect bloat histories. But all this expense and effort will be successful only if members of the participating breed clubs recruit exhibitors to take their dogs to the Purdue booth to be measured and to be enrolled in the study. Reminder: Data from individual dogs in our studies is confidential.
Irish Setter 1-Year Follow-Up
What percentage of dogs of a particular breed will bloat during their lifetime? That is, what is the lifetime risk or cumulative incidence of bloat in the breed? This question can be answered only by following a large number of dogs of that breed over time, which is one purpose of the new prospective study. The methods to be used in that study were first applied to Irish Setters measured at the Irish Setter Club of America National Specialty in June 1994. One- year follow-up data were collected for these dogs in the summer of 1995.
Of the 155 Irish Setters measured at the show, whose average age was 3.6 years, 11 (7%) had a previous episode of bloat while 144 (93%) did not.
In June 1995 each owner was sent a letter asking for follow-up information: Was the dog still alive? Had the dog had a bloat episode since June 1994? Owners who did not return their postcards were contacted by phone. Information was eventually obtained from all but 3 owners for a response rate of 94%. (Many thanks to the owners!)
Among 135 dogs who had not bloated before June 1994, 3 dogs bloated during the following year, for an annual incidence rate of 2.2%. This is approximately the annual incidence rate predicted from the data collected at the show, that is, from the prevalence at the average age of 3.6 years.
The cumulative lifetime incidence was estimated from the annual incidence rate. Assuming that in this breed the annual incidence rate of bloat is 2.2%, and the average life span is 12 years, the cumulative lifetime incidence rate for Irish Setters is estimated to be approximately 23.2%. Thus, these data predict that if all Irish Setters survived to age 12, almost 1 out of every 4 would bloat
This is the first population-based, breed-specific estimate of the lifetime risk of bloat. The estimate is probably conservative, since bloat risk increases with age, and the dogs measured at the show were younger than the general population.
Another purpose of the prospective study is to answer the question: Do dogs with deeper, narrower chests have a higher risk of developing bloat? The data from the show suggested that for individual Irish Setters, the greater the chest depth/width ratio, the greater the bloat risk. The follow-up data support this. The table below compares average chest depth/width ratios for dogs who bloated and those who did not. The P value of 0.01 implies that it is unlikely that the difference in depth/width ratios between those who bloated and those who did not between June 1994 and June 1995 was due to chance alone.
Heartbreak and Hope -- Findings from the Survival and Recurrence Study
The purpose of the Survival and Recurrence Study which began in January 1992, was to evaluate short-term survival rates, long-term survival rates, and bloat recurrence rates following an episode of bloat. All dogs with bloat identified for the case-control study, were eligible for this follow-up. The 140 owners who agreed to participate were interviewed by phone every few months about their dogs_ health status. The results demonstrate the high overall death rate and confirm the critical importance of gastropexy to prevent recurrence.
Of 140 dogs, 33 (23.6%) died within the first 7 days. Another 8 died later because of bloat recurrence, bringing the total death rate from bloat to 29.3%. Dogs who survived 7 days tended to be younger and in better medical condition when they reached the clinic, and had less stomach damage apparent at surgery. However, time between bloat onset and arrival at the clinic did not appear to be related to the likelihood of survival.
Of the 107 who survived >7 days, 10 (9.3%) had a recurrence and 8 of these died. During follow-up, 20 other dogs died from various medical conditions other than bloat. Recurrence data were analyzed for 82 dogs who were followed for 3 months to >3 years. The ability of gastropexy to prevent a bloat recurrence was striking:
Looking at the data another way, the probability of recurrence per dog per month of follow-up was 4% for dogs without gastropexy, compared with only 0.3% for dogs with gastropexy.
The success of gastropexy in preventing recurrences (secondary prophylaxis) has led to discussions about whether gastropexy should be done before the first episode (primary prophylaxis) in healthy, high-risk dogs. We are currently using a clinical decision analysis model to study this question.
All in the Family? (Part 3)
We are still trying to understand the possible importance of a familial form of bloat, in which clusters of cases occur within families, vs the sporadic form, in which single, isolated cases occur. Family history of bloat is one of the risk factors being evaluated in the new prospective study. Pedigree studies to date have not shown a simple mode of inheritance of bloat risk, such as that for certain eye diseases in dogs.However, the pedigrees sent to us -- and for which we are grateful -- have too much missing data to provide most of the answers we crave. This is no one's fault. It has become apparent that only in very rare instanceswill a breeder be able to provide a complete, lifetime bloat history for an entire large litter and/or several generations of ancestors.
Several lines of evidence, however, suggest that a dog's conformation (which is genetically controlled), particularly the depth/width ratio of the chest, influences the risk of bloat. Dogs with deeper, narrower chests tend to be at greater risk.
Jan Ziech, an Irish Setter breeder from Minooka, Illinois, is collaborating with the Purdue Bloat Research Team to study the genetics of the chest depth/width ratio and its relationship to bloat in a family of Irish Setters. Dr. Robert H. Schaible, an adjunct faculty member in the Department of Veterinary Clinical Sciences, is serving as genetic consultant.
The study family is of interest because several dogs have bloated. Measurements were obtained in 1994- 1995 for all but 1 of 15 surviving dogs in 2 litters. The dogs were measured at the 1994 ISCA National Specialty, at Purdue, or at veterinary clinics. These 2 litters were from the same dam but 2 different sires; the parents were also measured. The dam, 2 of 6 measured dogs whelped in 1988, and 3 of 8 dogs whelped in 1991 all had a history of bloat. Neither of the sires had a history of bloat. The lifetime history of bloat in this family, however, will not be fully known for years.
When the chest depth/width ratios of the 2 litters were plotted, the 1988 litter fell into 3 groups (trimodal distribution), while the 1991 litter fell into 2 groups (bimodal distribution). From this data, incomplete dominance of a major gene was hypo-thesized to be the mode of genetic inheritance of chest depth/width ratio. When the ratios for the parents were plotted on the same scale, the values for the sires were consistent with the values expected for sires that would produce the distributions observed in thelitters. The sire of the 1988 litter appeared to be heterozygous for the "deep-chest" trait, while the sire of the 1991 litter appeared to be homozygous. The dam was assumed to be heterozygous, since she produced pups with a trimodal distribution, but her own depth/width ratio contributed little to her classification because it fell between two categories.
If chest depth/width ratio is determined by a major gene, it would be easier to change a breed's conformation by selection than if the trait were controlled by many genes. More familial studies like these being facilitated by Jan Ziech are needed to confirm the mode of inheritance of this trait and its relationship to bloat risk.
From the Scientific Literature
Zentek and H. Meyer: Normal handling of diets -- are all dogs created equal? Journal of Small Animal Practice 36:354-359, 1995.
The answer to the title question is "no, " according to this paper from Hannover, Germany, which showed significant differences between Great Danes and Beagles in their ability to digest nutrients.
The authors noted that food tolerance differs among breeds, especially in the giant breeds, which can have increased frequency of soft stools. They measured "apparent digestibility" (difference between nutrient intake and fecal output) in four 5-day feeding trials. Four commercial diets, 2 canned and 2 dry [brands not identified], were tested in 3 Great Danes and 3-5 Beagles. Great Danes had lower ability to digest most nutrients in 3 of 4 trials, and also had a significantly higher fecal loss of water, sodium, and potassium.
An earlier study by these investigators showed that Great Danes have a smaller digestive tract relative to body weight compared to smaller breeds. This may account in part for the difference in digestive capability.
Comment -- This study illustrates the importance of considering possible breed differences when evaluating the role of diet in bloat or other diseases. In the new prospective study (see p.1) we will ask owners about the composition (reported on the label) of the diets they are feeding. If owners can provide this information, it will allow evaluation of the effect of dietary composition on bloat risk in each of the breeds studied.
We are grateful for donations to bloat research from individuals and breed clubs in honor of dogs affected by bloat.
We are pleased to acknowledge memorial fund donations from two groups of donors in honor of: Boomer, a fawn male Great Dane owned by Karen and Scott Hamilton. Am. Can. Ch. Daynakin-Grandy Nite Solo CD, a Great Dane owned by Bruce and Edie Lind.
Georgia Hymmen and Jack Henderson, Daynakin Great Danes, sent these memorials on behalf of all the contributors.
Thank$! -- Epidemiologic studies of bloat and other areas of companion animal health at Purdue University School of Veterinary Medicine are made possible by contributions from the Morris Animal Foundation, AKC Canine Health Foundation, animal health companies, private foundations, breed clubs (national, regional, and local), and
individuals whose dogs have experienced bloat. We welcome your comments, suggestions, and support.
Those wishing to donate can send contributions to Purdue University in care of Dr. Larry Glickman, Bloat
Research Program, Veterinary Pathobiology VPTH 101, Purdue University, West Lafayette IN 47907-1243.
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