The following update on lymphatic filariasis in Madagascar has just been
circulated on Lymfilariasis. I thought subscribers to Parasitology may
also be interested.
Lymfilariasis is a moderated discussion group on all aspects of lymphatic
filariasis.
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Regards
Rick Speare
Moderator Lymfilariasis
Department of Public Health and Tropical Medicine
James Cook University
Townsville
AUSTRALIA
Phone: -61-(0)77-225700
Fax: -61-(0)77-225788
email: Richard.Speare at jcu.edu.au
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Date: Wed, 30 Apr 1997 16:23:43 +0300 (GMT+0300)
From: esterre at pasteur.pasteur.mg
To: lymfilariasis at jcu.edu.au
LYMPHATIC FILARIASIS IN MADAGASCAR: RECENT DATA FOR AN OLD DISEASE
Bancroftian filariasis was initially introduced in the South-
West Indian Ocean by human migrations and described in most of the
islands since the beginning of the 19th century. Due to a
Wuchereria bancrofti strain with a nocturnal periodicity (maximal
density between 8 p.m. and 6h30 a.m.), it is mainly transmitted by
Anopheles gambiae, A. arabiensis and A. funestus even if some
culicids (Culex quinquefasciatus) have been identified as proven
vectors (for example, the only one present in Seychelles and Chagos
islands). Probably related to malaria vector control programs (as
in La Reunion and Mauritius, since 1949) or specific chemo-
prophylaxis with DEC (islamic Comoros islands) or both (Mayotte
island: DDT pulverisations since 1977, DEC tested in 1981 and then
regularly distributed since 1985: see Galtier et al., Bull. Soc.
Path. Exot., 1987, 80: 826-833), the disease is progressively
retreating since the beginning of the 20th century with the notable
exception of the eastern coast of Madagascar. This aspect of
historical epidemiology is reviewed in a recent paper (in French,
like all the others references mentionned in this release) of
Julvez and Mouchet (Bull. Soc. Pathol. Exot., 1994, 87:194-201).
Since the initial surveys of Brygoo ((1958: 20 to 37 p.cent of
the population of the east coast (18.384 exams !) with
microfilariema, but also 6.5 p.cent of inhabitants of Mahajanga
region on the west coast)) followed by Prodhon (in 1972, confirming
the existence of sporadic cases on the west coast: 9.2 p.cent of
inhabitants of Mahajanga, mainly of Comorian origin) and Bruhnes
(in 1975, who demonstrated the absence of the disease on the high
plateaux due to climatic conditions), there was no recent
information on this parasitic disease in Madagascar. The situation
in a pilot village on the east malagasy coast was compared in 1954
(prevalence: 39.6 p. cent, mean density: 1850 microfilaria/cubic
mm) and in 1967 (prevalence: 49 p.cent, mean density: 1925
microfilaria/cubic mm), after ten years of regular (two times a
year) insecticide (DDT and HCH) pulverisations for malaria control.
A DEC-based (6mg/kg one time a month during 7 months) control trial
was tested on the 53 inhabitants and confirmed (prevalence: 3.7
p.cent, mean density: 100 microfilaria/cubic mm), by comparison
with a control village (Dodin et al., Arch. Inst. Pasteur
Madagascar, 1968, 37: 17-24), the efficiency of the prophylactic
policy still developped since 11 years in French Polynesia (Laigret
et al., Bull. WHO, 1966, 34: 925-938).
Two recent surveys in the litlle island of Sainte-Marie (Nosy
Boraha), 6 kms from the east coast, and in 8 districts along the
eastern region revealed a global prevalence of 7.7 p.cent and 23
p.cent, respectively. The mean parasitic density ranged from 50 to
150 microfilaria/cubic mm in Sainte-Marie (Rakotomalala et al.,
Arch. Inst. Pasteur Madagascar, 1995, 62: 124-127), and was about
180 microfilaria/cubic mm on the east coast region (Champetier de
Ribes, BIESP, Ministry of Health, 1996, 6).
With a sex ratio of about 1.3, men are more exposed to pathology
including chronic morbidity (elephantiasis, hydrocoele). The
prevalence rate of chronic morbidity was 2.3 p.cent in Sainte-Marie
district and 7.3 p.cent on the costal region. In this last area, a
survey in 5 supplementary medical districts is planned and will
give a better idea of the global prevalence and associated
morbidity.
As ivermectin is presently not available on the local pharma-
ceutical market, mass treatment with DEC (6mg/kg) during three
consecutive years is the recommended strategy. This repetitive mass
treatment has been launched in 1995 in Sainte-Marie, but the
population of the eastern region will have to wait for available
funds before having the benefit of such a control program.
Dr. Gilles Champetier De Ribes, Service de Surveillance
Epidemiologique, Ministry of Health (DLMT division), PO Box 460,
Antananarivo 101, Madagascar
E-mail: deribes at bow.dts.mg
and
Dr. Philippe Esterre, Head of Parasitology Unit, Institut Pasteur
de Madagascar, PO Box 1274, Antananarivo 101, Madagascar
E-mail: esterre at pasteur.pasteur.mg
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[This is a magnificent contribution from our colleagues from Madagascar.
Many thanks for the time and effort involved in this update. Mod - Rick
Speare]
