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| Journal of the New Zealand Medical Association,
29-April-2011, Vol 124 No 1333
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Yaws in Polynesia’s Wallis and Futuna Islands:
a seroprevalence survey
Gilles Guerrier, Sandrine Marcon, Laure Garnotel, Roger
Deltour, Stéphane Schinas, Jean Pierre Mathelin, Chantal Chouvin, Olivier
Metge, Jean Marc Daronat
Yaws is a non-venereal infection caused by the spirochaete
Treponema pallidum subspecies pertenue. The disease affects
populations living in warm and humid subtropical countries, especially children
under 15 years, with a peak incidence in the 6 to10-year-old age range. Direct
skin-to-skin contact with exudative lesions is the main route of transmission,
together with breaks in the skin caused by injuries, bites, or
excoriations.1
Clinical manifestations occur in three distinct phases. The
primary stage is characterised by a papular “raspberry-like” lesion,
developed after 3 to 4 weeks of incubation at the Treponema inoculation
site and ulcerates. This painless cutaneous ulcer may last 3 to 6 months before
healing spontaneously. Secondary yaws are smaller skin lesions that teem with
widespread disseminated treponemes. At the late stage, bone, cartilage, and soft
tissue destruction may occur, leading to irreversible disabling or
disfiguration.
Despite strong reduction in geographic extension due to past
eradication campaigns targeting treponemal diseases organised by World Health
Organization (WHO) during the 1950s, yaws has been reported to be re-emerging in
Pacific islands, including Vanuatu2 and Solomon
Islands.3
To assess yaws prevalence on similar islands, a
seroprevalence survey was carried out on Wallis and Futuna, one of
France’s three Pacific Island groups, located about 600 km North-East of
Fiji.
MethodsA clinical and serological survey was conducted from
1–30 August 2010 among patients attending four outpatient clinics and one
hospital serving population on both islands.
Wallis has 9207 inhabitants scattered in three
districts, each having an outpatients clinic while 4238 inhabitants live on
Futuna served by a single clinic.4 Included
patients agreed with giving additional samples to perform treponemal serology in
addition to regular blood analysis they required. Presence of cutaneous or
osteo-articlular lesions was recorded, as well as trips in endemic areas, such
as Vanuatu or Solomon Islands.
All participants gave oral informed consent to
participate in the study, after methods and objectives were extensively
explained in local language by a native speaker health worker. Oral consent was
notified in patient’s notes. This procedure was approved by the
institutional review board. For children, consent was obtained from a parent or
a guardian. No incentives were offered to study participants and no names were
recorded. The study protocol was approved by the Wallisian Ministry of
Health.
ResultsA total of 264 serum samples were tested for specific
Treponema pallidum Hemagglutinations Assay (TPHA; Biomérieux,
Marcy l’Etoile, France) and non-specific Rapid Plasma Reagin (RPR;
Fujirebio, Tokyo, Japan) according to the manufacturer’s recommendations.
Among 222 samples coming from Wallis and 42 from Futuna, 52 (20%) were positive
for one or both tests. All positive patients but two were born before 1960
(Table 1).
Table 1. Seroprevalence Treponema
pallidum haemagglutinations assay (TPHA; specific) and rapid plasma reagin
(RPR; non-specific) by age group
Among those aged 50 or under, one had consistent serology
and compatible lesions with primary yaws without any relevant journeys in
endemic areas. No case of tertiary yaws has been detected. Patients never
travelled in other endemic areas with the exception of two job-seekers, who
spent respectively 5 and 10 years in Vanuatu during their twenties.
DiscussionFifty-year-old plus people were positive for treponemal
serology without any symptoms, compatible with serological scarring after healed
infections. Past infections had been contracted on Wallis or Futuna, since most
subjects did not move to areas with current yaws high endemicity.
The survey demonstrates that yaws was likely to have been a
public health problem in the past. Indeed, this finding is consistent with
seroprevalence surveys performed during eradication campaigns conducted in the
Pacific area over the 1950s.5 Since no data
after intervention are available in Wallis and Futuna—where yaws is not a
recorded condition in clinic statistics—our study provides interesting
result on yaws prevalence.
A very low prevalence of non-venereal treponemal disease was
found among young age groups. Our result contrasts with findings in Vanuatu,
where difficult to diagnose clinically forms of attenuated yaws have resurged.
This difference might be explained by the better availability and accessibility
of healthcare on Wallis and Futuna, thus allowing widespread use of antibiotics
for any infectious disease.
Serological tests cannot distinguish Treponema
pallidum subspecies. Therefore, positive TPHA may reveal past syphilis
infection, possibly lately treated in cases where VDRL is also positive.
However, high prevalence of yaws in the region during the
1930s6 indicates that serological profiles
found in our survey are suggestive of non-venereal treponemal disease. Finally,
rare cases of positive VDRL with negative TPHA may reflect false positive due to
non-treponemal infections or systemic diseases.
This study was designed to assess the prevalence of present
or past yaws on Wallis and Futuna. Due to time and financial constraints, study
design focused on people presenting to clinics. This may explain why younger age
groups are under-represented. Failure to randomise subjects is the major
limitation of this survey.
Yaws was less likely in people able and willing to access
health care. However, people live in close proximity to clinics and health
facilities provide free care. In addition, included patients were roughly evenly
distributed among different districts, limiting a potential selection bias.
Nevertheless, a study concentrating on randomly selected 5 to 15-year-old
children should be performed to definitely refute resurgence of yaws in Wallis
and Futuna.
Competing interests: None.
Authors: Gilles
Guerrier1, Sandrine
Marcon2, Laure
Garnotel3, Roger
Deltour3, Stéphane
Schinas3, Jean Pierre
Mathelin3, Chantal
Chouvin3, Olivier
Metge3, Jean Marc
Daronat1
Correspondence: Dr Gilles
Guerrier, Hôpital de Sia, BP4G, 98600 Matua’Utu, Wallis Island.
Email: guerriergilles@gmail.com
References:
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