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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 90, Num. 6, 1995, pp. 775-776
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 90(6).
775-776, nov./dec.. 1995
II National Meeting on Strategic Research in Leishmaniases
Belo Horizonte, MG, Brazil September 18-22, 1995
Hooman Momen
Departamento de Bioquimica e Biologia Molecular, Instituto
Oswaldo Cruz, Av. Brasil 4365, 21045-900 Rio de Janeiro, R J,
Brasil
Code Number: OC95155
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EPIDEMIOLOGY
Over 200 participants gathered for five days to discuss
strategic research in leishmaniases. The meeting was designed
to offer an opportunity for interaction between those working
in control and research of the diseases. The meeting was held
against a background of a worsening epidemiological situation
regarding the diseases in Brazil. This was highlighted by the
reports from many participants. Figures from the National
Health Foundation (Fundacao Nacional de Saude - FNS) showed
that in 1994 over 3000 cases of visceral leishmaniasis (VL)
and over 30000 cases of cutaneous leishmaniasis (CL) were
reported in Brazil. In addition, evidence was reported of
considerable subnotification of cases. These figures reflect
both: an increase in the number of cases reported in recent
years and an extension of the endemic areas.
Equally worrying is the increase in the urbanization of
the diseases. Besides the recrudescence of epidemics of VL in
cities such as Sao Luis the strategy should be re-examined
with the use of (Maranhao, MA), Fortaleza (Ceara, CE) and -
Teresina (Piaui, PI) outbreaks have occurred in cities where
this disease was previously unknown such as Belo Horizonte
(Minas Gerais, MG). Outbreaks of CL were reported in all
states of Brazil except Rio Grande do Sul (RS) and Santa
Catarina (SC). These outbreaks occurred not only in the usual
areas of forest and recent colonization but mainly in areas of
ancient colonization and increasingly in urban areas. The
focal and extensive nature of these cases were reported by
several participants. The significance of this urbanization
was discussed. One factor was the uncontrolled growth of urban
areas in recent decades due principally to rural migration.
This has led to the formation of districts (normally on the
periphery of the cities) where the population lives in
conditions of extreme poverty and which favour the spread of
endemic diseases. Where detailed investigations had been made
many of the cases were related to special ecological
conditions in the urban areas, such as proximity to parks,
rural surroundings or vacant plots, presence of trees or
abundant vegetation, or absence of sanitation. Peri-urban or
semi-urban may be a better description for many of these loci.
DOGS
The role of dogs and their control was a recur theme during
presentations and discussions. The current policy of the FNS
is for the elimination ofserologically or clinically positive
dogs in areas of visceral leishmaniasis. This strategy has
often met with resistance from the owners of affected pets and
with its growing implementation in urban areas due to the
recent epidemics this opposition has increased. This position
was made clear by the presence of a representative of a dog
breeders association at the meeting. Pedigree dogs are more
susceptible to infection than mongrels. In one case all the
females of a colony were found to be serologically positive
dooming the colony to extinction and the owners to economic
distress. The technical basis for this strategy were discussed
and although it was felt that no immediate changes in current
policy should be made. It was proposed that controlled trials
and the study of alternative methods of control (see below).
The role of a canine reservoir for cutaneous leishmaniasis
caused by Leishmania braziliensis has also been an
object of controversy. In a case control study in the area of
Baturite (CE), a strong correlation was found between human
cases and the presence of infected dogs in the household.
Furthermore the age distribution of the human cases and the
feeding behaviour of the sand flies indicated intra-domicilary
transmission. Similar results were found in the area of Viana,
Espirito Santo(ES). In addition studies on feeding preferences
of the most frequent sand fly species found in the intra and
peri:domestic habitat showed that they were attracted to dogs
and humans and not to wild animals. In the discussion it was
noted that although these two loci are widely separated and
may be representative of the former Atlantic forest areas
where L. braziliensis circulates, there exists other
epidemiological situations where the importance of dogs has
not yet been demonstrated. The issue of the primary reservoir
host in the silvatic habitat was also discussed and it was
felt that with the new in situ molecular
hybridization and amplification techniques, the answer to this
riddle would soon be found.
CONTROL
Vector control was another important theme of the meeting.
There was some discussion on the importance of the repellent as
opposed to the insecticidal activity of the chemicals used in
household spraying. The use of ultra low volume (ULV) spraying
using organophosphates as an alternative to canine control was
suggested. There exists anecdotal reports of the interruption of
VL transmission after ULV spraying for the control of dengue in
some cities in the northeast of Brazil. Older reports relate a
similar interruption of transmission when spraying
organochlorides against anophelines for the control of malaria
was carried out. It was felt that a controlled trial was needed
to test the efficacy of ULV, perhaps together with the use of
insecticide dips for dogs, as an alternative to the elimination
of dogs in leishmaniasis control.
There was not much news in the area of chemotherapy.
Concern was expressed at the near monopoly situation in the
supply of pentavalent antimony and the lot to lot variation of
the active ingredients. Experimental information is urgently
required on the effect of temperature, light and other factors
on antimonial drugs and on the change in concentration
ofpentavalent and trivalent ions during storage. It was felt that
many studies aimed at identifying optimum drug doses were not
comparable because of these factors which could also be
responsible for some reports of increasing drug resistance.
Difficulties in the treatment of certain patients were also
pointed out, in particular, those who are resistant to
antimonials and do not respond to amphotericin as well as those
who suffer from diffuse cutaneous leishmaniasis. The necessity
of further research was emphazised to develop safer and better
drugs to treat not only humans but also to cure canine
leishmaniasis. Reports of trials with immunotherapy were also
presented. The results although limited indicated some utility
as an alternative to chemotherapy in treatment of pregnant women
or when combined with antimonials to lower the dosage and thus
reduce toxicity. Further controlled trials are however
required.
VACCINATION
Vaccination was another prominent theme of the meeting.
Canine vaccination studies though starting later than human
studies appear to be making greater progress. Three vaccines were
presented by groups from Pernambuco, Minas Gerais and Rio de
Janeiro. All showed promise in early studies. The vaccine from
MG is currently undergoing a double blinded controlled phase III
trial in a VL endemic area in Montes Claros (MG). The codes are
expected to be broken in December of this year. The Pernambuco
vaccine is also expected to undergo a phase III trial shortly.
The results of these trials are eagerly awaited to see whether
canine vaccination can become an effective control tool. The long
history of human vaccination studies in Brazil including the
results of the different trials was reviewed at the meeting.
Currently the vaccine produced by the group from MG has been
reformulated and is now based on a single strain of L.
amazonensis. This vaccine has completed its phase I trials
and will shortly start phase II. The large number of skin-test
positives found in volunteers from an apparent non-endemic area
promoted a discussion on the Montenegro test and the sensitivity
to the timerosal used in its preparation.
Difficulties with diagnostic tests was another topic of
discussion. Current serological tests have a low sensibility
especially in patients with localized cutaneous lesions, who are
the most frequent cases. The need for more sensitive antigens was
emphasized as well as the hope expressed that molecular
biological techniques would assist in a rapid and precise
diagnosis A need for a rapid simple diagnostic test for field use
with dogs was also brought up. A number of candidates exist and
the FNS is planning multi-centred field trials to test these
kits.
A number of more didactic presentations were also made on
aspects of the immunology, molecular biology, characterization,
clinical signs and epidemiology of the diseases for the benefit
of the large number of technical personnel involved in control
that were present. The interaction between people involved in
administration, control and research in these diseases was on of
the aspects that contributed to the success of the meeting. The
full proceedings of the II National Meeting on Strategic Research
on Leishmaniasis will be published shortly as a supplement to the
Revista da Sociedade Brasileira de Medicina Tropical. It
was decided to hold the next national meeting in Fortaleza (CE)
in 1997.
Acknowledgements: to Drs Keyla and Mauro Marzochi for critical
reading of the original manuscript.
Copyright 1995 Fundacao Oswaldo Cruz
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