WAFDAL

Archive for the ‘MegaOesophagus’ Category

Report to the 8^th ECDC meeting in Croatia in 2007

By Tyge Greibrokk

Chairman, Health and Breeding Commission

Mega oesophagus (MO) is a gastrointestinal disorder which is found mainly in young puppies, soon after birth, whereby an inborn enlargement of the digestive tract (oesophagus) leading to the stomach allows reflux of stomach contents into the mouth and also into the lungs.  Symptoms are coughing, milk leaking out of the nostrils and vomiting, leading to malnutrition, starvation and frequent bouts with pneumonia, often requiring the puppies to be euthanized. However, occasionally the enlargement can become reduced more or less completely at an age of 5-7 weeks.

In 2004/2005 several incidents of mega oesophagus in Dalmatian litters became known in several European countries. Breeders started to collect information, rumors were flying and one breed club introduced restrictions on breeding. The ECDC meeting in Belgium in 2005 appealed to the clubs and the breeders to report new cases to T. Greibrokk of the Health and Breeding commission, in order to try to obtain more knowledge about how MO can be inherited. A considerable amount of information has been obtained, particularly from Switzerland, the Nordic countries and the Netherlands, but also from breeders in other countries, including New Zealand. Altogether we have information from 71 European litters and 10 from New Zealand, spanning more than 30 years in time, and with pedigrees for all. Not all the reports are confirmed by a veterinary. Unfortunately, the last year has not provided much news, for whatever reason.

We wish to be able to answer the following questions:

1. Is MO an inherited trait among Dalmatians and how common is it?

2. Assuming inheritance, what is the mode of inheritance?

3. What can the breeders do?

Question 1:

The answer to the first part of this question is definitely, yes. The test breeding results from New Zealand rules out all doubts.

But, is there a difference between the background of the New Zealand dogs and the European dogs?

The answer is not really, in both cases dogs from UK are in the background.

However, could there be several slightly different MOs, from mutations arising at different times and/or places?

This cannot be ruled out, but the majority of the pedigrees points in the same direction, to imports from UK, often a long time ago. After all, this is the basis of most Dalmatians in Europe as well as in New Zealand, and we know that MO has been found in Dalmatians in the UK and in the rest of Europe for decades. Several co working genes, like in hip dysplasia, is of course a possibility.

Is it commonly found among our Dalmatians?

During the last 25 years in the Netherlands, Norway and Sweden, MO was reported in about 0,3% of the litters. This is not a representation of the actual incidence in these countries, only of the known cases. In most European countries not even this degree of information is available. In all likelihood the occurrence is higher, possibly much higher.

Question 2:

First, we can conclude that the inheritance is not related to sex.

Secondly, it is apparently not a simple recessive or a simple dominant inheritance.

Thirdly, the expression (the symptoms) shows great variation. X-ray examinations of puppies from New Zealand and Sweden also prove that early symptoms may disappear a few weeks later, resulting in healthy dogs.

Thus, it is possible to conclude with either dominant inheritance with incomplete penetrance and different expressivity, or poly genetic inheritance with different expressivity.

From the breeding results we cannot decide which is the most probable, but personally I favor a theory of poly genetic inheritance. With less impact of some genes and more of others, or vice versa, differences in expression are more easily understood. Thus, when a dog with one subset of genes (and never having given MO) is mated with another dog with another subset of genes (which never gave MO too), the combination can release the disorder. The effect would appear to be recessive. This can explain why some stud dogs give no problems in 50 litters, until suddenly comes two with MO.

Another argument is the fact that MO exists in several breeds, but apparently with different hypotheses for inheritance, while none actually have been proven. I find it difficult to believe that exactly the same mutation would appear in very different breeds. More likely, in my opinion, is a natural variation in the genes responsible for building the nerves and muscles of the digestive tract, allowing many different protein expressions to take place and thereby to different seriousness of the disorder. If this hypothesis should be correct, we will probably never be able to develop a simple DNA-test for MO.

Question 3:

Due to the large variations in symptoms and the fact that in many puppies the symptoms are gone at 7-8 weeks of age, it is likely that the incidence of MO is much higher than the reported numbers. Most major breeders may have had a litter with MO, even without detecting it. Remember that many puppies do not live long enough to be diagnosed, for different reasons.

A couple of breeders in New Zealand and Sweden now take all their puppies to contrast X-ray at 4 weeks of age, in order to get maximum information about their breeding dogs and for not selecting the wrong puppies for future breeding. In Sweden the cost is about 55 Euro per puppy. This is a procedure which is highly recommendable for breeders which suspect they may be in the danger zone.

What about breeding restrictions?

Without knowing the mode of inheritance, one should be careful about restrictions. However, a puppy that has been diagnosed with MO should never be used in breeding, even if the symptoms are long gone, with the only exception for test breeding.

In order to be able to get information from the breeders, we are dependent on their goodwill and cooperation. Thus, it is more important with openness than with restrictions and everybody should have an interest in more knowledge. We have seen that suddenly there is an accumulation of MO on some lines, giving the breeders a substantial problem. This could happen to everyone, unless we start to be more open about our breeding results.