The present study reports on the incidence and risk factors of diarrhoea and vomiting in young, large breed dogs in Norway. Both diarrhoea and vomiting are relatively common conditions, although diarrhoea is more often registered. Most of the dogs only suffered from one episode of either diarrhoea and/or vomiting during the study period. Moreover, dogs suffering from several episodes of gastrointestinal disorders demonstrated relatively long periods without signs in between these episodes. In line with the findings of Hubbard et al.
], a positive association between the occurrence of diarrhoea and vomiting in the same dog was found. In the majority of dogs in the present study, however, episodes of diarrhoea and vomiting did not occur at the same time.
The distributions of both diarrhoea and vomiting were skewed with a much higher frequency during the first months of life. Puppies are immunologically immature and by 12 weeks of age the majority have lost most of their maternally derived antibodies rendering them more prone to infections [14
]. Additionally, the stress of weaning, transportation and re-homing could lead to an increase in gastrointestinal infections due to increased susceptibility [15
]. Obviously, many other causes of acute gastrointestinal disorders, like changes in diet, ingestion of garbage or table scraps, and ingestion of foreign material are commonly reported [16
]. An important issue when evaluating the health status of puppies is the owners' possible increased awareness during the first months of their dog's life. This may lead to a higher rate of registrations in the younger compared to the older dogs. Hubbard et al.
] reported no association between the age of the dog and the frequency of either vomiting or diarrhoea. On the other hand, Wells and Hepper [4
] reported that the frequencies of both vomiting and diarrhoea were highest in puppies and declined with increasing age. Also, studies exploring the occurrence of infectious agents, with the potential to cause gastrointestinal disorders, in faecal samples have reported a higher occurrence in young dogs [17
Results from previous studies regarding a possible gender or breed influence on the occurrence of diarrhoea and vomiting in the dog, are conflicting. Hubbard et al.
] did not find any association between vomiting and gender, but diarrhoea was significantly more common in males. Also, Stavisky et al.
] reported a higher occurrence of diarrhoea in males in a recent case-control study. In two other studies no effects of breed and gender on the occurrence of gastrointestinal conditions were reported [4
]. Our results indicate an association between gender and occurrence of diarrhoea, with males more often exhibiting this sign. A possible explanation may be differences in behaviour between the genders. In a study of dog to dog interaction the frequency of dog sniffing at another dog differed significantly between gender, with males more often exhibiting this behaviour [23
]. Furthermore, the most common inspection areas when two dogs meet, are the head and anogenital area, with males inspecting the anogenital area more often than females [24
]. Also, male dogs may show increased roaming behaviour [25
]. Therefore, one could speculate whether differences in behaviour between the genders might render males at a higher risk for developing gastrointestinal disorders. In the present study, the incidence of both diarrhoea and vomiting was influenced by breed, which is in contrast to the results of Hubbard et al.
]. However, some of the breeds in their study had very few individuals included. Several possible explanations for differences in occurrence of gastrointestinal conditions between breeds can be provided. Firstly, differences in genetic susceptibility leading to increased risk of infections are suggested to occur in some breeds [26
]. Secondly, differences in both husbandry and behaviour might occur between different breeds. Such differences could be related to feeding regimens including the type of diet, frequency of receiving titbits, frequency of scavenging, frequency and length of walks, length of time off leash, number and length of dog to dog interactions et cetera
. Hubbard et al.
] reported differences in the frequency of scavenging between different breeds, but not the frequency of receiving titbits. Feeding a home-cooked diet, a recent history of scavenging, or change of diet all increased the risk of diarrhoea in the dog [21
]. In the present study, the information about nutrition was not sufficient to assess the influence of feeding on diarrhoea and vomiting in the study population. However, almost all dogs were fed commercial diets from well-reputed international companies.
In the present study the higher incidence of diarrhoea in the urban areas could be explained by rural living locations offering fewer possibilities for dog to dog contact, and contact with other dogs' excreta. Also, in the dog, regular contact with cattle, sheep or horse faeces, which is more likely to occur in rural areas, appeared to be associated with a reduced risk of diarrhoea [21
In the present study, the occurrence of both diarrhoea and vomiting demonstrated a seasonal variation with higher incidence in the summer months. Different seasons have the potential to influence, among other things, the frequency and length of walks, dog to dog interactions and the frequency of scavenging. Also, the occurrence of potential infectious agents responsible for diarrhoea and vomiting can be influenced by climatic conditions.
Some potential limitations of the present study need to be highlighted. A random effect for breeder was considered, but since the breeder:litter ratio was close to one, the breeder level was omitted. The GEE method is considered a suitable and robust method for analysing repeated measures with a dichotomous outcome [13
], but is limited to a single level of clustering [27
]. The possible effect of clustering of the dogs in litters on the two models was evaluated by using the "xtmelogit" command in Stata, with dog and litter as random effects using the same independent variables as in the GEE models (data not shown). The results from the "xtmelogit" analyses supported the GEE results, and estimates were not influenced much by the model. For diarrhoea the litter represented approximately 20% of the residual variance and the dog the rest, while the random effect was of marginal effect. For vomiting there was a strong random effect on dog, with litter explaining only 3% of residual variance. These results suggest that the GEE estimates were reliable and that the random effect at dog level was the most important one in the models. Also, episodes of diarrhoea and vomiting are owner-reported, and misclassification bias may have occurred. Diarrhoea is often defined as "increased faecal fluidity, and is usually accompanied by an increased defecation frequency and volume of faeces" [16
]. This is a sign generally recognized by the owner without any problem. Vomiting is "a reflex act initiated by stimulation of the vomiting centre in the medulla" oblongata, and should be differentiated from regurgitation; "the passive evacuation of undigested food from the oesophagus" [28
]. Vomiting is also a sign easily identified by the owner. However, regurgitation might have been classified as vomiting in our study. On the other hand, regurgitation is not so common, and usually a more permanent clinical condition compared to episodes of vomiting [3
]. It should, however, be noted that some breeds, including the Irish wolfhounds, are predisposed to megaoesophagus and portosystemic shunts (PSS). These conditions, might lead to regurgitation, intermittent diarrhoea and/or vomiting [28
]. Fortunately, the Irish wolfhounds included in the present study were all screened for PSS by a bile acid test at six to eight weeks of age and were all found to be normal (data not shown). As part of the study, all dogs were regularly assessed by a veterinarian, and none of the dogs included were diagnosed with megaoesophagus. Also, unmeasured factors, like recent stay in kennel, could confound or intervene [21
The relatively high number of owners which left the study during the observation period could have influenced the validity. Also, the dogs in this study population were owned by people participating in a research study and they underwent regular veterinary examinations as well as regular vaccination and deworming, i.e. living under presumably optimal conditions. Stavisky et al.
] reported that having up to date vaccination history reduced the risk of canine diarrhoea. Validity for other breeds (e.g. smaller breeds), other ages (e.g. older dogs), other geographical areas and dogs held under less optimal conditions can therefore be questioned. On the other hand, cohort studies generally have a high relevance to real-world situations and a relatively high external validity [30