The original post written by Susan McConnell has raised several issues which really require separate posts for reasons of clarity. However the ongoing discussion on the original post has of course – as conversations do – moved on. To post the following only as a comment to the original post has the potential to create confusion, hence this new thread. First I wish to declare and amke it known that the following treatise is a personal opinion and is not a reflection of any CPRG process nor is endorsed by the CPRG in any way. Susan raises the issue of using raw data to generate statistical information. She states that she is uncomfortable with data being used to generate inter-country comparisons as she sees this as both divisive and discriminatory. She then states, and I quote I feel the focus should be on helping reduce the incidence of HWSD, worldwide. There is a science called Epidemiology. By definition the science of epidemiology has been defined as follows: the study of the distribution of a disease or condition in a population or those factors which influence their distribution (A. Lilienfeld 1958). A more recent definition is a method of reasoning about disease that deals with biological inferences derived from observations of disease phenomena in populations and groups (D. Lilienfeld 1978) So the question is, how can the incidence of HWSD worldwide be established if raw data is not used for comparative study? Epidemiology studies disease spread within a population, the mode of transmission of the disease and the temporal (or time) over which a disease state has become established in a defined population. Because I know most about the populations of the Connemara ponies in Australia (Aus) and New Zealand (NZ) , these will be used as an example. Until 2005 New Zealand had a very small population of very closely related ponies. Over 67% of them were descended from a single mare; have/had very high COIs. There had been no reports of hoof problems. In 2005 a series of imports of ponies began from Australia. 2007 saw internet discussion begin on soft foot. In 2007 an in-foal mare imported from Australia dropped a filly foal which demonstrated signs of what we now know is HWSD. Fast forward to the beginning of the research at Davis. Blood samples from 39 NZ domiciled ponies were sent for use in the preliminary research. Using pedigree data as a guide the expectation was that ponies born in NZ, prior to 2005 would all be N/N. From the research data subsequently made available to me personally, by the owners of these ponies, this expectation was upheld. Time therefore – used from an epidemiology perspective - supports the premise that HWSD entered the NZ Connemara pony population after 2005 as a direct result of importing ponies from Aus. We know it had to come from Aus, we know when it came from Aus and we were able to establish which sub-populations were most at risk. Time and geography. Now take Susans own personal situation which she herself reports upon. “I have tested my top tier breeding Connemara Ponies which are: both my Premium stallions as well as all my broodmares. This covers the breeding stock I have owned and bred under the Oakfields prefix since 1989 in the USA. All the stallions and mares results were N/N. Therefore, all the ponies I have bred over the years follow as N/N and will not need testing.” So what does this tell us from an epidemiological perspective? Time and geography! We are talking about a closed population since 1989. The original ponies were all N/N and no further blood has been introduced into the population. We are told the geographical origins of the population. IF we look at the USA population using the freely publicly shared HWSD status information supplied by pony owners, then we see that the only carrier stallion and 2/3 of the carrier mares are all of many generations of USA breeding. Once again what does this tell us? Time! It shows that the mutation has been present at a low level in the USA population for a very long time. The third carrier mare listed is USA born but has parents from opposite ends of the globe! Epidemiological importance here? Geography! So by comparing raw data the numbers of ponies tested by VGL from August 2014 to October 2014 with information freely provided by pony owners, we have already established: 1. that the indications are that the NZ population was HWSD free prior to 2005. 2. the affected lines from Aus came from over a wide geographical area in Aus itself. 3. the 3 affected Aus lines are not related to each other until back into generations + 10 4. the 3 affected lines appear to have come into Aus in the second tranche of imports in the 1970s So readers, you have to make up your own minds as to whether the information generated by extrapolating raw data from VGL and using the information provided by freely given HWSD test results is useful and helpful to, and supports Susans view “I feel the focus should be on helping reduce the incidence of HWSD, worldwide. “ or is in fact divisive and discriminatory?
Posted on: Tue, 11 Nov 2014 20:41:13 +0000
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