Investigation Recap:
Last month we reported
on an investigation of an unprecedented lead poisoning outbreak in
Nigeria (Epi Monitor April 2011) which won the Singal award at
CDC’s recent Epidemic Intelligence Service Conference in Atlanta.
Since then the Epi Monitor has learned that the organizations
investigating and responding to the outbreak have been named the
2011 winners of the Green Star awards for “environmental heroes
working in disasters and emergencies” (see related article). What
remained unclear from that initial report are the details of how
the outbreak was actually detected, a topic of special interest to
epidemiologists and others conducting disease surveillance.
Assumptions
Whenever outbreaks
happen they are by definition a departure from the usual rate at
which disease occurs and thus may be readily detected or reported
via routine surveillance activities, perhaps by an observant
clinician, or by members of the affected population. And the
events in this outbreak were certainly unusual since the death
rate was as high as 30% of all children under five years of age in
some villages, according to Jane Greig from Médecins Sans
Frontières (MSF) or Doctors Without Borders.
In fact, it appears
that none of these pathways produced an early or effective alert,
and the behind the scenes story of how the outbreak came to be
detected and the response carried out reveals much about the
incredibly harsh conditions and complex public health problems in
some poorer areas of developing countries.
The following account
has been pieced together from documents and interviews with MSF
epidemiologists Jane Greig and Todd Swarthout, and
fact checked with other MSF staff working on the outbreak (Lauren
Cooney
(health advisor for the emergency desk), Natalie Thurtle
(current health advisor for the project), and Leslie Shanks
(medical director).
MSF was the first group of public health professionals to identify
and respond to the outbreak which the British Medical Journal
called the worst heavy metal contamination incident on record
worldwide.
Origins
The outbreak came to
attention of MSF at the end of March 2010 when a team doing
regular “emergency surveillance” for meningitis visited villages
in the area of northern Zamfara state. These teams are fielded
regularly by MSF looking for early signs of epidemic-prone
diseases such as meningococcal meningitis. The team was informed
of sick children, and a large number of deaths were reported to
them, however, the symptoms did not fit clearly with likely local
causes of illness such as meningitis or malaria, and the onset of
cases predated the usual onset date of the seasonal meningitis
cases. Furthermore, treating the sick children for these
conditions had no impact.
More MSF
Investigation
MSF and Ministry of
Health (MoH) teams provided 24hr medical care in the villages from
the start of April, and on April 8, an MSF epidemiologist, medical
coordinator and assistant medical coordinator visited two
villages, saw children at the local health posts, and talked with
villagers. Investigators began to suspect the illnesses were
linked to the observed crushing and grinding of rock going on in
village households as part of mining activities in the area, with
heavy metal poisoning a strong differential diagnosis. Suspicion
centered initially on mercury poisoning since it is used in the
process of gold mining and inhabitants doing the mining had
evidence of mercury on their hands. In agreement with the MoH, the
investigators took blood samples which had to be sent to a
laboratory in Germany for heavy metal testing. Although mercury
poisoning was considered, the clinical picture pointed more to
lead intoxication. The blood test results, which were delayed for
days because of ash clouds over Europe from a volcano in Iceland,
showed that lead was clearly the problem, with all samples having
levels far exceeding the threshold for urgent treatment.
Important News
The diagnosis of lead
poisoning was important news because the team now knew that
chelation therapy isan effective medical intervention. However, it
was not readily available in this part of the world, so all that
the MSF physicians could provide at this early stage was
supportive care for symptoms such as fever and convulsions. In
effect, they were working long hours, but only buying time for
children who were likely to die until chelation therapy could be
obtained. And this was hard on the doctors, said Greig and
Swarthout.
A New Mission
Discussions within MSF
headquarters ensued about what should be the MSF response. The
organization has an “Emergency Desk” to manage the critical phase
of emergency interventions, and this clearly was a situation where
more children would die without treatment. However, what to do was
not an easy decision. MSF had never provided such therapy before
and knew little about it. The advice of organizations such as CDC
/ WHO and toxicologists would be critical to making an effective
response. However, MSF knew that no other organization was likely
to respond quickly enough nor have the operational ability to work
in such a difficult environment, so they decided they had to do
it. In early May, MSF worked out what scope their response should
have.
As soon as MSF had
results, they sought, and encouraged the Nigerian Ministry of
Health to seek support from the USA Centers for Disease Control
and the World Health Organization,. Chelation therapy was sourced
and the Ministry of Health had to give permission to import the
drug into Nigeria.
Logistics
MSF has strong
logistics capacity, but the challenges involved in providing such
therapy under the harsh conditions found in the villages were
daunting. For example, MSF could not administer treatment in the
villages where the patients lived since these dwellings were still
contaminated and would result in ongoing exposure to lead. So they
had to set up special treatment centers in 2 local government
hospitals in areas provided by the local government in the big
towns nearest the first 2 villages found to be affected. MSF had
to resolve issues of providing adequate power and water, finding
additional staff and adequate housing for them, and obtaining food
and accommodations for the caregivers and other siblings who
accompanied the sick children to the therapy site.
Testing and
treatment
CDC was able to bring
in portable machines to test blood lead levels of children in
large numbers locally. They also brought a team from TerraGraphics
who confirmed the source and extent of the exposure, as well as
provided emergency plans for remediaton, which is a key
contributor to recovery of children. Some of the initial blood
levels were “astronomically” high, according to Greig. This
provided an extra challenge to in-field testing, since almost all
levels were above the upper limit of the portable machines
capacity, so a dilution protocol had to be devised and validated
by the field team and experts at CDC headquarters. In Europe,
children might get 4-5 rounds of treatment for much lower lead
levels over a course of a couple of years. In Nigeria, some of the
children have needed more than 10 rounds of treatment already, in
less than 1 year! And family support was required for many days
since the initial course of treatment given by MSF was for 28 days
as an inpatient. The magnitude of the challenge was considerable
since essentially every child under five in the first-known
affected villages was at risk, and there were hundreds of sick
children to treat.
Rapid impact
One positive aspect of
the episode was the quick impact of treatment: some children came
to the treatment center in a coma or no longer able to walk and
showed rapid improvement with treatment, starting to walk again
within just a few days. However, this posed additional challenges
since it was a huge burden on families to send children to the
treatment centers, and the caregivers wanted to return to their
villages when children appeared much improved even though their
treatment was not complete. However, some children remain with
severe neurological sequelae.
New Protocols
This challenge of
maintaining patient compliance has been reduced since, in
collaboration with an expert panel, MSF has been able to innovate
and modify its treatment protocols from what they were in the
early days. Inpatient treatment has been replaced largely by
outreach teams that are able to go to the villages and give
children oral tablets for a standard course of 19 days.
Data For Action
During the early
outbreak investigations, routine patient line lists were recorded
to review symptoms of the unknown condition and develop a case
definition, and “quick and dirty” survey data was collected to
obtain a rough estimate of death rates, which even if somewhat
inaccurate were still “ridiculously” high, according to Greig.
Once the cause was identified and chelation therapy was available
the death rates dropped dramatically. A database was set up to
record treatment information, which has improved over time to meet
changing project needs. Information about the personal
characteristics of patients, treatment courses, and blood sample
results at different times during treatment has been collected.
With this information, MSF has been able to make informed
decisions about patient management and protocol modifications. The
data permit not only retrospective analysis, but help manage daily
treatment and follow-up activities.
Current Status
As of this point, the
magnitude of the problem in Nigeria is unknown for sure, however,
children in the seven villages first known to be affected have
been screened, children who need treatment are offered it, and the
environment has been remediated by teams led by the international
organizations TerraGraphics & Blacksmith Institute. There remains
at least one large village which has high environmental lead
levels but has not yet been remediated.
Cause of the
Outbreak
The outbreak occurred
because of very high lead content, sometimes >10% lead, in the
rocks being crushed to extract gold, but the reasons the outbreak
occurred last year and not earlier are not fully understood. It
does appear that the problem happened quickly and thus could have
been caused by a new gold strike or discovery in the area, a
change in the source of rocks used for mining since the percent
lead in these rocks varies, or some other precipitating factor.
One thing that appears certain is that more grinding machines
began appearing in the villages as more households took on mining
activities late in 2009.
Long Term Solution
Despite the
encouraging aspects of the response to the outbreak itself, a
solution to the longer term problem of preventing recontamination
of the soil after villages have been remediated remains
challenging. As long as a financial incentive to mine rock
exists, then the risk of exposure will persist in the absence of
safe mining practices. Villages themselves made efforts to move
the mining activities out of the main area of the villages, but
this presents other challenges of secure storage of equipment and
travel distances. Implementation of safer mining practices is
crucial to ensuring villages are no longer lead contaminated.
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"...organizations investigating and responding to the outbreak
have been named the 2011 winners of the Green Star awards for
'environmental heroes working in disasters and emergencies'"
"Furthermore, treating sick children for these conditions had
no impact"
"...Lead was clearly the problem, with all samples having
levels far exceeding the threshold for urgent treatment."
"MSF
knew that no other organization was likely to neither respond
quickly enough nor have the operational ability to work in
such a difficult environment, so they decided they had to do
it."
"...grinding machines began appearing in the villages as more
household took on mining activities late in 2009."
"...some of the children have needed more than 10 rounds of
treatment"
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