hello my name is maria de la puente and i work
for the european commission for the control of food and month disease in this presentation i'm
going to introduce you to the use of the timeline in an fmd outbreak investigation in summary this
is what we are going to see we will remember how we age fm deletions we will see how to construct
a timeline and a little example on how to use it so why we age fm deletions the first thing
is that we do it to take the relevant samples that will allow us to confirm or rule out fmd
so for example if you look at this picture think about how old this lesion is
and therefore which kind of sample would you take from this animal i'll let you
think about it okay so if you look at here we could say that these lesions are one day
old and therefore here what we would do is to take a sample of vesicular fluid or
epithelium to try to isolate the virus so now try again with this other picture so
look at it estimate the age of the lesion and then think about which would be
the sample of election in this case okay give you the answer so now this lesion would
be 10 days or older which means that the virus infected the animal much longer ago than in the
previous case and therefore we could expect to find antibodies in this case we would probably
take a blood sample to do a serological test the second reason why we age deletions in
the case during an outbreak investigation is to be able to build a timeline that help us to
trace back and forth the most relevant contacts and this is what we are going to see now
how to build this timeline and how to use it so first of all to build a timeline we
need an excel sheet that has these rows and as you can see that i put in the following names
that will make more sense in the following slides calendar discount day zero visions
infection window and excretion window so the first step now that we have
this um timeline or this sheet is to put the date when we go to the
farm to do the outbreak investigation so here you can see in the
example it's the 1st of december so once we have it we can add the rest of the
days in the row calendar so after and before then we need to identify when the
first lesion appeared in the farm and to do this we need to be able to age
lesions so we need to find the oldest solution in the farm and in this example imagine
that this lesion was four days old so in the line editions we are going to color
the following days so if it is four days old on the first of december when we went to the farm
then we count three two one and we color here then we are going to add the day zero date zero
will be will represent the prodromal period which will be in the case of fmd one day which
is the period like um before the lesions appear when the animal will show like in a specific
symptoms like inappropriate so we color it here the zero and then we add the zero and the rest
of the count minus one minus two minus three etc and now we are going to define
the infection window and to do this we consider the incubation period
a of a fmd and the equation period is the period that goes from the infection
of the animal until the clinical signs appear and in cattle it is 2 to 14 days so we are
going to color it here you see minus 2 2 to -14 but the most likely incubation period is shorter
is from 2 to 6 days so in this case we are going to color it a bit darker because it was this
will represent the most likely incubation period and we will use this to define which
is the most likely infection window also so now that we have the infection window we
are going to define the extraction window so um in an animal the this will happen two
days before the onset of the clinical signs um and in milk we could find a virus up to
four days before the onset of the disease in this example we are going to think that
we are a like working with a young male so we will forget about those four and
we will color from minus two onwards and again we will have a most likely
expression window that will go from day 0 to day 3 and we put it in a darker color and basically that's it we have for
timeline so now we need to use it um i'm putting here one example on how to use
the timeline in this case we are going to define a which would be the most likely source of
introduction of fmd in the farm so i'm giving you here three examples for you to think which
one do you think is the most likely source the first example is two cows that were bought
on the 29th of november then we have the farmer who visited his cousins farm on the 23rd of
november and finally some hay that was brought to the farm on the 11th of november so i'll let
you think a bit about it before giving the answer so take your time to look at the timeline
and place those three events in the timeline so let's see the solution okay i'm
sure you got it right the farmer who visited his cousin on the 23rd of november
is the most likely source of infection and this is because if you place the three events in
the timeline you can see that the two cows were brought into the farm much later and
like it doesn't fall in the incubation a period in the infection window the farmer
visited his cousin's farm in the most likely infection period while the hay was brought to
the farm too early in our timeline so that's it i hope you found it useful and now it's a bit
clearer how to construct a timeline thank you you
