1 June 2019 | New Scientist | 13OUR sun had a lazy start, which may
explain why we are here today.
The moon has surprisingly fewer
volatile elements and compounds –
those that turn into gas and blow
away easily – than Earth. PrabalSaxena at NASA’s Goddard Space
Flight Center in Maryland and his
colleagues investigated whether
solar activity in the first billion years
or so after the moon formed could
explain the discrepancy.
The rotation rate of stars slows
during their lifetimes but there is
variation in how much. The team
used data from the Kepler Space
Telescope on other sun-like stars
to build three models of the
young Earth and moon, each
with the sun rotating at a different
rate. The faster the young sun
spun, the more often it would
have blasted out plasma in flares
and coronal mass ejections.
If the young sun rotated fully
about once a week, there could be
tens of coronal mass ejections a
day, enough to erode away all of
the moon’s potassium and much of
its sodium – volatile elements that
we know still exist there today.
But if the sun turned just once
every eight to 10 days, Earth and
the moon would experience a
powerful ejection only every few
days. That would have left behind
enough sodium and potassium on
the moon to match observations
(The Astrophysical Journal Letters,
doi.org/c55p).
If this let Earth hold on to its
volatiles, too, it could help explain
why life arose here, says Saxena. ❚Solar systemLeah CraneYoung sun spun
slowly, helping life
emerge on EarthThe sun
blasts
plasma into
space in
flares and
coronal mass
ejectionsAS THE climate warms, Lyme
disease is spreading. To assess
the risk of catching the infection
in new areas, we need to track
the ticks that carry it. Now an
analysis of veterinary records
suggests dogs are the answer.
Lyme disease can lead to heart
failure or paralysis, but we don’t
know how many people come
into contact with the bacterium
that causes it. “We don’t screen
ourselves for exposure,” says
Jenna Gettings at the University
of Georgia. “The only time
people are tested for tick-borne
disease is when they have
symptoms. Whereas with dogs,
we screen healthy animals.”
In the US, many pet dogs are
tested for Lyme disease at yearly
check-ups, and the information
is sent to a central database.
It is possible to share veterinary
records widely, because these
don’t have the same kinds of
privacy concerns as human
health data, says Gettings.
She and her colleagues haveanalysed the results of
more than 16.5 million dog
screening tests from 2012 to- These detect if dogs have
produced antibodies to Borrelia
burgdorferi, the bacterium
that causes Lyme disease and
can be passed to animals and
people in tick bites.
Because dogs tend to go to
the same places as their owners,
the dog data should reveal
where people are at the highest
risk of contracting the disease.
When the team compared
the dog data with the reported
rates of Lyme disease in humans
during the same five-year
period, it found an association.
In US counties where up to
10 per cent of dogs screened
positive for B. burgdorferi
exposure, there was a rapid
increase in human incidences
of Lyme disease (GeospatialHealth, doi.org/c58w).
In areas where between
10 and 30 per cent of dogs
screened positive, human rates
also rose, but more slowly. In
areas where more than 30 per
cent of dogs encountered the
bacterium, there was no link
between dog and human data.
“We don’t fully understand
why the association drops off,”
says Gettings. “It may be that
we don’t have a ton of data
at that level.” Thankfully, few
US counties have such high
levels of dog exposure to the
bacterium, she says.
Because veterinarians tend
to test dogs annually, the data
can’t tell us about the spread
of Lyme disease over short
periods of time. It also can’t
take into account when a pet
dog contracted Lyme disease
outside its home county.
Nevertheless, the team could
use the data to build a model
that helps predict where Lyme
disease may be spreading.
“Where the value of this
analysis seems to be the greatest
is in the sort of leading edge
of the range of Lyme disease,”
says Rick Ostfeld at Tufts
University in Massachusetts.
“In places where incidence is
low, it may be that the dog data
is a good sentinel for us.”
In places where Lyme disease
is endemic – the Northeastern
and upper Midwest US – public
health officials and doctors
make people aware of the
risks and give advice on how
to avoid tick bites.
But people in counties where
Lyme disease hasn’t historically
been a problem may be caught
unawares as ticks and the
diseases they carry spread into
their area. This new model could
help give people a much-needed
warning, says Ostfeld. ❚Dogs reveal where Lyme
disease is spreading
Dogs tend to visit
the same places
as their ownersEpidemiologyChelsea WhyteEDUA
RDO^ ARR
AES/GET
TY16.
million dogs were screened
between 2012 and 2016NA
SA
/GS
FC
/SD
O