Longitudinal follow-up of malaria transmission dynamics in two villages in a Sahelian area of Niger during a nationwide insecticide-treated bednet distribution programme.

Malaria transmission was monitored in two villages in the Sahel zone of Niger over 4 years. During this period, a nationwide vector control programme was carried out in which insecticide-treated bednets were distributed free to mothers of children aged <5 years. Anopheles gambiae and Anopheles arabiensis (Diptera: Culicidae) were found to be the major malaria vectors. The dynamics of An. gambiae s.l. did not vary dramatically over the study period although the proportion of female mosquitoes found resting indoors decreased in both villages and, in one village, the parity rate and sporozoite index were significantly reduced after bednet distribution. By contrast with An. gambiae, the dynamics of Anopheles funestus altered greatly after the bednet distribution period, when adult density, endophagous rate and sporozoite rates decreased dramatically. Our observations highlight the importance of quantifying and monitoring the dynamics and infections of malaria vectors during large-scale vector control interventions.

Anopheles hervyi in Niger: no evidence for a role in Plasmodium falciparum transmission.

Anopheles hervyi is an endemic mosquito species with a very limited spatial distribution in the south east of Niger. No new captures have been reported since the 1960s and its role in malaria transmission has not been studied. In the present study, the use of CDC light traps showed it to be much more abundant than previously found but there was no evidence to suggest it was a malaria vector in this region. The larval habitats have not been identified but the potential role of a saline lake in determining the distribution of this species is discussed.

[Plasmodium falciparum chloroquine and pyrimethamine resistance monitoring network with molecular tools in the Niger River valley, Republic of Niger]. / Réseau de surveillance moléculaire de la chimioré- sistance de Plasmodium falciparum a la chloroquine et a la pyriméthamine dans la vallée du fleuve Niger, au Niger.

Plasmodium falciparum resistance to chloroquine first arose in Africa 25 years ago. Nowadays most of African malaria control programmes have switched their first-line treatment of uncomplicated malaria cases towards artemisinin derivatives combination. After WHO guidelines, a survey network for malaria treatment resistance has been set up in the Niger valley around Niamey since December 2004. The association of the Niger national malaria control programme with the CERMES research center allowed collecting of samples from both health centers and hospitals of this region. Blood finger-pricks on filter papers were tested for detection of plasmodial antigen in health center without biological diagnosis capacity. Specimens found positive either in hospital laboratory or by using antigen method were tested by PCR/RFLP to detect K76T mutations on the pfcrt gene and S108N mutation on the pfdhfr gene. This simple procedure allows the screening of a large number of specimens. Moreover, a spatial distribution of mutations and evidence of resistance clusters were searched integrating the data in a geographic information system. The 76T mutation of pfcrt and 108N of pfdhfr were respectively found in 50.8% and 57% of the specimens tested. No statistically significant difference was found according to the level of sanitary formations or the age of the patients. No resistance cluster was identified and the prevalence of mutation seems homogeneous in the zone. By completing the clinical efficacy studies we think that our simple method for collecting and testing blood samples associated with clinical efficacy studies may be useful for building a network of malaria drug resistance in Africa.

[French language training course: malaria workshop organized by Institut Pasteur de Madagascar]. / Formation francophone Sud/Sud: l'atelier paludisme de l'Institut Pasteur de Madagascar.

The Malaria Workshop organized by Institut Pasteur de Madagascar is an original course that applies innovative concepts to training of health professionals involved in malaria control in endemic countries. Course objectives are to enhance the skills needed to fight malaria (transversal competencies, critical approach, and position statement), to reinforce project cycle management proficiency, and to demonstrate how the Internet can be used as a source of documentation to compensate for geographical isolation. The Malaria Workshop is a six-consecutive-week full-day course that has been presented once a year since 2003. Seventy-six researchers, physicians or health ministry officials have already benefited from this training. Teaching methods emphasize andragogy that facilitates a learner/mentor relationship promoting exchange rather than transmission of knowledge and problem-based learning that engages learners to take an active part in gathering information. These methods in combination with the diverse backgrounds and experience of course participants foster a positive dynamic environment for learning that is monitored by weekly progress evaluation. Follow-up surveys have confirmed the positive effect of this training on the professional performance of former participants who become more involved in program development and fund-raising efforts. A professional network is growing and learners are starting to their experience. In this report workshop organizers describe the course's origins and concepts and present the conclusions drawn based on the first five yearly sessions.

ELISA study of oocyst-sporozoite transition in malaria vectors.

Intrinsic vector characteristics and environmental factors affect the sporogonic development of P. falciparum in Anopheles mosquitoes. We tested for the presence of the circumsporozoite protein, as a marker of the oocyst to sporozoite transition in naturally infected Anopheles gambiae s.l. and Anopheles funestus. Malaria vectors were collected in a village in the Sahel of Niger during the rainy and dry seasons. ELISA-CSP was carried out on abdomen and head/thorax portions from more than 2000 samples. No significant difference was found in the overall rates of infection of An. gambiae s.l. (4.13%) and An. funestus (3.58%). Given the differences in duration of the two parasite stages, P. falciparum CSP antigen prevalence was nearly as high in the abdomen as in the head/thorax, and did not differ significantly between An. gambiae s.l. and An. funestus. These preliminary results suggest that development from oocysts to salivary gland sporozoites is similar in the two vectors. However, these developmental indices varied as a function of the season in which samples were collected, particularly for An. gambiae s.l. This simple method may be useful for field studies assessing the effect of environmental and genetic factors on parasite survival.

[Fleas and diseases transmissible to man]. / Les puces et les maladies transmises à l'homme.

Fleas are wingless insects that parasitize mammals and more rarely birds. They are able to jump and may bite people. Adult fleas are hematophagous. The impact of fleas on public health is related to their ability to act as vectors for transmission of infectious agents during blood meals. The purpose of this article is to describe fleas and the diseases that they transmit to humans. Special focus is placed on epidemiological aspects.

Population genetic structure and competence as a vector for dengue type 2 virus of Aedes aegypti and Aedes albopictus from Madagascar.

Starch gel electrophoresis was used to assess the polymorphism of 7 isoenzymes in single mosquitoes (field-collected F0 or F1 generation) for Aedes albopictus (8 strains) from northern Madagascar. Mosquitoes of the F2 generation (3 strains of Aedes aegypti and 10 strains of Ae. albopictus) were tested for oral susceptibility to dengue type 2 virus. Aedes aegypti was less susceptible to viral infection than Ae. albopictus. The genetic differentiation was less high between Ae. albopictus populations collected in agglomerations connected by highly frequented roads, indicating that human ground transportation favors mosquito dispersal. These results have implications for the ecology, pattern of migration, and relative importance in epidemic transmission of dengue viruses between the 2 Aedes species.

Plasmodium falciparum parasites in French Guiana: limited genetic diversity and high selfing rate.

The genetic characteristics of Plasmodium falciparum isolates collected in French Guiana, where malaria transmission is low and occurs in isolated foci, were studied. Blood samples were collected from 142 patients with symptomatic malaria and typed using a polymerase chain reaction-based strategy for merozoite surface protein-(MSP-1) block 2, the MSP-2 central domain, and glutamate-rich protein (GLURP) repeat domain polymorphism. This showed that the parasite population circulating in French Guiana presented a limited number of allelic forms (4, 2, and 3 for MSP-1 block 2, MSP-1, and GLURP, respectively) and a small number of mixed infections, contrasting with the large genetic diversity of parasite populations and infection complexity reported for Africa, Asia, and other parts of South America. Two groups of isolates displaying identical 3 loci allele combinations were further studied for the Pf332 antigen, histidine-rich protein-1, thrombospondin-related anonymous protein, and Pf60 multigene family polymorphism. Within each group, most isolates were identical for all markers tested. This suggests a high rate of self-fertilization of P. falciparum parasites in French Guiana, resulting in homogenization of the population. The implications of these findings for malaria control in areas of low endemicity are discussed.

Malaria transmission in Southern Madagascar: influence of the environment and hydro-agricultural works in sub-arid and humid regions. Part 1. Entomological investigations.

A 4-year entomological study was carried out in Southern Madagascar to identify malaria vectors, evaluate the transmission and compare the influence of irrigation in the sub-arid and adjacent humid regions. Three villages were involved in this entomological survey: Androvasoa (located in the natural sub-arid ecosystem), Pépiniére (sited at the centre of an irrigated rice scheme in the sub-arid region) and Esana (bordered with rice fields in the humid region). Mosquitoes were collected inside and outside dwellings when landing on human beings, with light traps and with knockdown indoor sprays. Anopheles arabiensis, Anopheles merus and Anopheles funestus were found in every village while Anopheles gambiae s.s. was only found in the village bordering the rice-fields (Pépiniére) and Anopheles mascarensis, a mosquito native to Madagascar, was only found in the humid region (Esana). In Pépiniére, the annual entomological inoculation rate (EIR) was low (EIR=0.4 infective bites/man/year (IBM)). In the irrigated scheme of the sub-arid region, malaria transmission was 150 times higher (mean EIR=63 IBM) than in the natural ecosystem and A. funestus was the main vector, responsible for 90% of infective bites. In Esana, the level of malaria transmission was high (EIR=41 IBM) and 2/3 of the infective bites were due to A. mascarensis, despite the presence of A. gambiae s.s. and A. funestus. These results are discussed with reference to the impact of irrigation on malaria in Africa ("the paddies paradox").

In vitro sensitivity of Plasmodium falciparum to amodiaquine compared with other major antimalarials in Madagascar.

Chloroquine has been used in Madagascar since 1945 and remains the first-line treatment for uncomplicated cases of malaria. Low-grades of resistance type R1 and R2 have been reported. Thus, in vitro tests were performed in order to monitor the drug sensitivity of Plasmodium falciparum from different study sites, with the aim of identifying alternatives to chloroquine. Chloroquine IC50 values ranged from 0.2 nM to 283.4 nM (n = 190, mean IC50 = 52.6 nM; 95% CI = 46.1-59.1 nM). Fifteen isolates (7.9%) were chloroquine-resistant. One mefloquine-resistant isolate was detected (1/139). The test isolates were sensitive to amodiaquine (n = 118), quinine (n = 212), pyrimethamine (n = 86) and cycloguanil (n = 79). The median IC50 for amodiaquine was 12.3 nM (mean IC50 = 15.3 nM, 95% CI = 13.3-17.3 nM). Amodiaquine was 3.4 times as active as chloroquine in vitro and 7 times as active as quinine against P. falciparum. These results indicate that amodiaquine may be a potent alternative to chloroquine in Madagascar. There was positive correlation between tested quinoline-containing drugs activities, which suggests in vitro cross-susceptibility.

Two new fleas (Siphonaptera: Ceratophyllidae: Leptopsyllinae) of Madagascar: Tsaractenus rodhaini n. sp. and Paractenopsyllus (Consobrinopsyllus n. subgen.) goodmani n. sp.

Following considerable sampling in Malagasy forests, two new species of endemic fleas from Madagascar are described. These are T. rodhaini n. sp. and P. goodmani n. sp., collected on small mammals. The material of T. rodhaini allows us to describe the previously unknown female of the genus Tsaractenus. We also complete the initial description of the genus with new diagnostic characters. Although it belongs to Paractenopsyllus, P. goodmani shows many unique characteristics. To help resolve certain systematic issues involving Malagasy Leptopsyllinae we introduce the new subgenus Consobrinopsyllus of Paractenopsyllus for P. goodmani. Its particular condition makes us consider valuable characters of the genus Tsaractenus. Carrying several traits of this genus, P. goodmani could constitute an intermediate step between the two endemic Malagasy leptopsylline genera. Considering these new findings the actual taxonomic position of the Malagasy genera among the Leptopsyllinae is discussed.

Leptopsyllines from Madagascar (Insecta: Siphonaptera: Ceratophyllidae): description of five new species of Paractenopsyllus Wagner, 1938.

Five new species of the malagasy endemic genus Paractenopsyllus Wagner, 1938, are described. Paractenopsyllus rouxi, P. ratovonjatoi, P. duplantieri, P. juliamarinus and P. gemelli have been collected on endemic small mammals and the black rat. Biotopes are mid-elevation rain-forests of the central highlands or the northern mountains of Madagascar. Morphological affinities between these new species and those already known provide taxonomic links within the genus. Differences in the spatial and altitudinal distributions and host ranges allow discussion of the potential factors important in the species distribution of this genus.

[Description of three new species of Paractenopsyllus genus (Siphonaptera: Leptopsyllinae) from Madagascar]. / Description de trois nouvelles especes de Paractenopsyllus (Siphonaptera: Leptopsyllinae) de Madagascar.

The males of three new and rare species of the Malagasy endemic genus Paractenopsyllus Wagner, 1938 are described. Paractenopsyllus beaucournui, P. oconnori and P. raxworthyi have been collected on endemic small mammals and the black rat. As for others species of the genus, biotopes are rain-forests of the central highlands or the northern mountains of Madagascar. Two of the described species were collected at elevations lower than typical for the genus and below the limits of the highland bioclimatic zone. Morphological affinities between these new species and those already described provide taxonomic framework for the genus. An updated identification key is provided for the diagnosis of all the 20 Malagasy species of Leptopsyllinae.

[Molecular characterization of mosquitoes of the Anopheles gambiae complex from Mayotte and Great Comoro]. / Caractérisation moléculaire des moustiques du complexe Anopheles gambiae à Mayotte et à Grande Comore.

The mosquitoes of the Anopheles gambiae complex have been characterised at specific and sub-specific levels in two islands of the Comoros archipelago: the island of Mayotte (French departmental collectivity) and the island of Grande Comore (Comoros Union). Results are similar in the two islands and are presented together. The species An. gambiae s.s. was observed alone (determination performed on 149 specimens by PCR product of IGS of rDNA). The molecular form observed alone was S, and corresponds in this geographic area to the chromosomal form Savanna (determination performed on 123 specimens by another PCR product of IGS of rDNA). The haplotype IB was observed alone (determination performed on ten specimens, by sequencing the ITS of rDNA, with special attention at the position 871 of ITS), as previously observed by other authors in East Africa. Finally, in Mayotte and Grande Comore the An. gambiae complex is only composed by An. gambiae s.s. from the molecular form S/type IB.

[Resurgence of the plague in the Ikongo district of Madagascar in 1998. 2. Reservoirs and vectors implicated]. / Résurgence de la peste dans le district d'Ikongo à Madagascar en 1998. 2. Réservoirs et vecteurs impliqués.

Our survey of mammals and fleas arose as a result of an outbreak of bubonic plague at an usually low altitude in the Ikongo district (Madagascar), while a previous study had found anti-F1 antibodies in an endemic hedgehog. Animals were sampled with live traps in two hamlets (Antanambao-Vohidrotra, 540 m alt. and Ambalagoavy, 265 m alt.) and with pitfall traps in a neighbouring forest (750 m alt.). Rat fleas were collected by brushing the fur and free-living fleas by use of light traps. The introduced shrew Suncus murinus was found only in the village of Ambalagoavy while the black rat (Rattus rattus) was found in all three sites and the only seropositive rat was caught at Antanambao-Vohidrotra. In contrast, among the Tenrecidae (endemic shrews and hedgehogs) found in the forest near the first village, four animals were found seropositive for anti-F1 antibodies. One of them was carrying the endemic flea Paractenopsyllus pauliani, not yet reported as a vector of plague. The endemic vector of plague, Synopsyllus fonquerniei, was found only in the first village of Antanambao-Vohidrotra, and the cosmopolite flea Xenopsylla cheopis only in Ambalagoavy. Although no Yersinia pestis could be isolated and no F1-antigen could be detected in these animals, we found evidence of the recent transmission of plague in Antanambao-Vohidrotra and the nearby forest, but not in Ambalagoavy. These data corroborate with the sylvatic plague cycle hypothesis in Madagascar and its involvement in the outcome of the bubonic plague outbreak in this district.

[Resurgence of the plague in the Ikongo district of Madagascar in 1998. 1. Epidemiological aspects in the human population]. / Résurgence de la peste dans le district d'Ikongo à Madagascar en 1998. 1. Aspects épidémiologiques dans la population humaine.

Between the 20th October and the 18th November 1998, an outbreak of bubonic plague was declared in a hamlet in the Ikongo district of Madagascar. We conducted an epidemiological survey because of the re-emergence of the disease in this area (the last cases had been notified in 1965) and because of the low altitude compared to the classical Malagasy foci. The outbreak had been preceded by an important rat epizootics during September. A total of 21 cases were registered with an attack rate of 16.7% (21/126) and a lethality rate of 33% (7/21). The disease was more prevalent in males (66% of cases) and children aged < 15 years, as observed in general throughout the country. The anti-F1 seroprevalence among the contact population was 13.5% (13/96), probably attributable to subclinical infection by Yersinia pestis. No rodent was trapped during the survey, but an endemic hedgehog (Tenrec ecaudatus) was highly seropositive, suggesting a recent transmission of the plague bacillus among this species. The small mammals and vectors possibly involved in these new foci were investigated in May 1999.

[Update on plague in Madagascar]. / Actualités sur la peste à Madagascar.

After a thirty year period of successful control, bubonic plague showed the first signs of return in Madagascar where a fatal outbreak occurred in Antananarivo in 1978. A second outbreak was observed in Mahajanga in 1991 after more than a half century. In 1997, 459 confirmed or presumptive cases were reported, as compared to 150 to 250 cases during the last years. However the actual extent of this recrudescence must be placed in the perspective of a more efficient control program that has led to better reporting of suspected cases and availability of more accurate diagnostic techniques. Recent research has led to the development of highly effective immunological diagnostic tools (detection of antibodies and F1 antigen) allowing not only better surveillance of the disease in man and animals but also renewed study of the epidemiological cycle in the current environment. In this regard the capacity of several endemic fleas as vectors and the role of the rat Rattus norvegicus and the musk shrew Suncus murinus are currently under investigation. Genetic study of strains collected from 1936 to 1996 has demonstrated the appearance of 3 new ribotypes of Yersinia pestis since 1982 in the zones of strongest plague activity in Madagascar. A strain showing multiresistance to standard therapeutic antibiotic agents was isolated in 1995. Bubonic plaque is a priority health problem in Madagascar but remains a major concern for the rest of the world.

[Systematics and biology of Anopheles vectors of Plasmodium in Africa, recent data]. / Systématique et biologie des anophèles vecteurs de Plasmodium en Afrique, données récentes.

Renewed interest in research on Plasmodium vectors in Africa and development of genetic and molecular biology techniques has been spearheaded by the WHO and the PAL+ program of the French research ministry. New findings have led to a better understanding of the systematics and biology of the main vector groups. The purpose of this article is to describe the newest data on the Anopheles gambiae complex and the M and S forms of An. gambiae s.s., on species in the An. funestus group and genetic polymorphism of An. funestus, on the two probable species in the An. moucheti complex, and on An. mascarenesis.

[Evaluation of the effect of Knox-Out microencapsulated V.O. 240 and K-othrine powder on rat lice in two villages in the Betafo region]. / Evaluation de l'effet du Knox-Out microencapsulé V.O. 240 et de la K-othrine poudre sur les puces des rats de deux villages de la région de Betafo.

The effect of two different insecticides on flea control was tested from January to March 2000 in the Ivory village and the Ambatolahy village: Knox-Out, a microcapsulated formulation of diazinon, organophosphorous compound (240 gr/L) and the deltamethrin powder (2 g/kg ai), respectively. The villages are located 2.5 km apart in the Betafo region in Madagascar. Deltamethrin is a pyrethroid and is still used in the National Plague Control Program, whereas diazinon has not previously been applied in plague control in Madagascar. The flea index and the prevalence of rats carrying fleas in the two villages before and after (at one and two months follow-up, respectively) were measured to evaluate the effect of each insecticide. Flea index decreased significantly in both villages by at the first month follow-up. However, at the second month follow-up no significant differences in comparison to pre-treatment index values were observed in any of the villages. This study has demonstrated a similar immediate effect of deltamethrin and of diazinon, and confirmed the absence of remanent action of the two insecticides.