Three ‘clusters’ of confirmed cases (red drops on AlabamaRot.co.uk’s map) of Alabama Rot appear around Leigh in Greater Manchester, the New Forest in Hampshire and Guildford in Surrey (between November 2012 and 14th April 2015). Are these indicative of an Alabama Rot causing environmental factor at a higher concentration relative to other non-cluster areas of England (1)?
The five blue drops on the map (1) are confirmed cases by county (Hampshire and Greater Manchester) and are excluded from this analysis (Figure 1 & 2). If Anderson Moores located these cases by town or village would the New Forest or Leigh clusters be increased?
I define the term ‘cluster’ arbitrarily to mean three cases or more in an area of less than 99 km2, equivalent to one case in less than 33 km2 area. Would a statistician advise me whether this is a reasonable definition of a ‘cluster’?
There have been 60 confirmed cases of Alabama Rot (33 confirmed cases listed by town (red drops) and 27 confirmed cases listed by county (blue drops)) in England between December 2012 and 14th April 2015. This is an average of 3 cases per month between the months of November and June.
Only three cases (5%) have been reported in the four months between July and October: in Somerset in July 2014; Ogdens, New Forest October 2013 and Leeds in September 2014. Does this suggest a temperature dependent environmental factor present in Winter (Nov-Jan), Spring (Feb-May) and early Summer (June) that triggers CRGV – or does seasonality occur by chance?
Leigh in Greater Manchester has a cluster of 3 Alabama Rot confirmed cases in approx. 6 km2 area or 1 case per 2 km2 (Figure 3).
The New Forest has a cluster of 16 confirmed Alabama Rot cases in approx. 394 km2 area or 1 case per 25 km2 (Figure 4).
Guildford has a cluster of 4 confirmed Alabama Rot cases in approx. 30 km2 or 1 case per 8 km2 (Figure 5).
In the three clusters (Leigh, New Forest, Guildford), 26 cases occur in 430 km2, an average 1 case per 17 km2.
The area that bounds all English confirmed cases is approx. 81,265 km2 (Figure 6).
The 35 confirmed cases (27 blue drop county case and 8 red drop town cases) that do not occur in the above three clusters are spread over an area of 80,835 km2 (81,265-430 km2) or 1 case per 2310 km2.
Each case in the three cluster areas (Leigh, New Forest, Guildford – 1 case per 17 km2) are x136 (i.e. 2310/17) more concentrated than the other English cases (one case per 2310 km2) .
Are these three clusters statistical flukes? What is likelihood that these clusters could occur by chance? Are vets in these areas reporting Alabama Rot at a greater rate than vets in the rest of England? Are dogs walked more in the cluster areas than elsewhere in the UK?
(1) Alabama Rot UK Map: https://www.google.com/maps/d/edit?mid=zIJgTtl9x6zk.kif7awTR9hAA