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M Coluzzi

Publications and source records attributed to M Coluzzi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Zoophily of Anopheles arabiensis and An. gambiae in Madagascar demonstrated by odour-baited entry traps.

In Madagascar we used odour-baited entry traps (OBETs) for host choice tests of wild female anopheline mosquitoes (Diptera: Culicidae) at representative localities on the East and West sides of the island (villages Fenoarivo and Tsararano, respectively) and at the southern margin of the central plateau (Zazafotsy village, 800 m altitude). No insecticide house-spraying operations have been undertaken at these villages. Odours from a man and a calf of similar mass, concealed in different tents, were drawn by fans into separate OBETs set side by side. Traps were alternated to compensate for position effects, and different pairs of individual baits were employed for successive replicates. Totals of 266 An. funestus Giles sensu stricto and 362 An. gambiae Giles sensu lato were collected in 48 trap nights during March-June 1999. For each mosquito species the 'index of anthropophily' was defined as the proportion of females caught in the human-baited trap. For An. funestus this index was found to be consistently greater than 0.5 (value for random choice between traps/hosts), indicating that this species 'preferred' human to calf odour (index=0.83). Conversely, the index of anthropophily for An. gambiae s.l. indicated they 'chose' calf in preference to human odour (index=0.26). No significant differences of relative preference for calf or man were detected between villages; geographical variance accounted for <8% of the total experimental variance. Molecular identifications of 181 specimens of the An. gambiae complex (approximately 50% of the samples) revealed only An. arabiensis Patton at Tsararano and Zazafotsy, but >97% An. gambiae Giles sensu stricto at Fenoarivo, in accordance with prior knowledge of the differential distributions of these sibling species on the island. Predominant zoophily (i.e. intrinsic 'preference' for cattle odours) by both An. arabiensis and An. gambiae s.s. in Madagascar contrasts with their greater anthropophily in continental Africa.

Animals↗
PubMed2000

Promoter sequences of the putative Anopheles gambiae apyrase confer salivary gland expression in Drosophila melanogaster.

The saliva of blood-feeding arthropods contains an apyrase that facilitates hematophagy by inhibiting the ADP-induced aggregation of the host platelets. We report here the isolation of a salivary gland-specific cDNA encoding a secreted protein that likely represents the Anopheles gambiae apyrase. We describe also two additional members of the apyrase/5'-nucleotidase family. The cDNA corresponding to the AgApyL1 gene encodes a secreted protein that is closely related in sequence to the apyrase of the yellow fever mosquito, Aedes aegypti, and whose expression appears enriched in, but not restricted to, female salivary glands. The AgApyL2 gene was found searching an A. gambiae data base, and its expression is restricted to larval stages. We isolated the gene encoding the presumed A. gambiae apyrase (AgApy) and we tested its putative promoter for the tissue-specific expression of the LacZ gene from Escherichia coli in transgenic Drosophila melanogaster. All the transgenic lines analyzed showed a weak but unambiguous staining of the adult glands, indicating that some of the salivary gland-specific transcriptional regulatory elements are conserved between the malaria mosquito and the fruit fly. The availability of salivary gland-specific promoters may be useful both for studies on vector-parasite interactions and, potentially, for the targeted tissue-specific expression of anti-parasite genes in the mosquito.

5'-Nucleotidase↗
PubMed2000

Cytogenetics of the Anopheles gambiae complex in Sudan, with special reference to An. arabiensis: relationships with East and West African populations.

The species composition of malaria vector mosquitoes belonging to the Anopheles gambiae complex (Diptera: Culicidae) from >40 localities in Sudan, representing most ecological situations, was determined by analysis of ovarian polytene chromosomes. Of 2162 females, 93% were identified as An. arabiensis Patton and 7% were An. gambiae Giles sensu stricto. No hybrids were found between the two species. Anopheles arabiensis occurred in all but two sites, whereas An. gambiae s.s. was effectively limited to the southernmost, more humid localities. For chromosomal paracentric inversions, the degree of polymorphism was low in An. gambiae s.s. (inversions 2La, 2Rb and 2Rd), higher in An. arabiensis (inversions Xe, 2Ra, b, bc, d1, s; 3Ra, d). Anopheles gambiae samples from Sudan were all apparently panmictic, i.e. they did not show restricted gene flow such as observed among West African populations (interpreted as incipient speciation). Chromosomal inversion patterns of An. gambiae in southern Sudan showed characteristics of intergrading Savanna/Forest populations similar to those observed in comparable eco-climatic situations of West Africa. Anopheles arabiensis was polymorphic for inversion systems recorded in West Africa (2Ra, 2Rb, 2Rdl, 3Ra) and for a novel 2Rs polymorphism, overlapping with inversion systems 2Rb and 2Rd1. Samples carrying the 2Rs inversion were mostly from Khashm-el-Girba area in central-eastern Sudan. In the great majority of the samples all polymorphic inversions were found to be in Hardy-Weinberg equilibrium. Sudan populations of An. arabiensis should therefore be considered as generally panmictic. Anopheles arabiensis shows more inversion polymorphism in west than in east African populations. Sudan populations have more evident similarities with those from westwards than those from eastwards of the Great Rift Valley. The possible influence of the Rift on evolution of An. arabiensis is discussed.

Africa, Eastern↗
PubMed2000

[Malaria eradication in Calabria, residual anopheles and transmission risk].

The paper is from a presentation at the meeting "La malaria in Calabria" (Cosenza, Italy, May 3, 1997) held to celebrate the half centenary of the antimalaria campaign (1947-1952) that eradicated the infection from the region. While Plasmodium falciparum had already disappeared in 1950, P. vivax persisted and the last autochtonous case was documented on the river Esaro in 1955. From the records of that time, it is clear that malaria eradication was achieved in the presence of important vector densities, as shown by larval surveys. Indoor DDT spraying, acting through the insecticide irritant effect, mainly avoided the house resting by the vector and forced the exposure of the mosquito to the outdoor environment where the lower mean temperatures eventually proved instrumental in destabilizing the parasite's life cycle. It is stressed that insecticide resistance never arised in the Anopheles vector populations of Calabria, in spite of at least ten years of continuous indoor spraying with an excellent overall coverage. This is expected in the absence of important selection pressures at the larval breeding sites and whenever the impact of the house spraying on the vector is due mainly to the insecticide irritant effect rather than to a direct imagocidal effect.

Animals↗
PubMed1999

Trapping cDNAs encoding secreted proteins from the salivary glands of the malaria vector Anopheles gambiae.

The signal sequence trap method was used to isolate cDNAs corresponding to proteins containing secretory leader peptides and whose genes are expressed specifically in the salivary glands of the malaria vector Anopheles gambiae. Fifteen unique cDNA fragments, ranging in size from 150 to 550 bp, were isolated and sequenced in a first round of immunoscreening in COS-7 cells. All but one of the cDNAs contained putative signal sequences at their 5' ends, suggesting that they were likely to encode secreted or transmembrane proteins. Expression analysis by reverse transcription-PCR showed that at least six cDNA fragments were expressed specifically in the salivary glands. Fragments showing a high degree of similarity to D7 and apyrase, two salivary gland-specific genes previously found in Aedes aegypti, were identified. Of interest, three different D7-related cDNAs that are likely to represent a new gene family were found in An. gambiae. Moreover, three salivary gland-specific cDNA fragments that do not show similarity to known proteins in the databases were identified, and the corresponding full length cDNAs were cloned and sequenced. RNA in situ hybridization to whole female salivary glands showed patterns of expression that overlap only in part those observed in the culicine mosquito A. aegypti.

Amino Acid Sequence↗
PubMed1999

Interethnic differences in the humoral response to non-repetitive regions of the Plasmodium falciparum circumsporozoite protein.

We analyzed the humoral immune response to the amino- (amino acids 22-125) and carboxy-terminal (amino acids 289-390) non-repetitive domains of the Plasmodium falciparum circumsporozoite protein (PfCSP) in individuals belonging to three west African ethnic groups (the Fulani, Mossi, and Rimaibé) living in the same conditions of hyperendemic transmission in a Sudan savanna area of Burkina Faso. Previous surveys conducted in the same area showed obvious interethnic differences in the susceptibility and immune reactivity to malaria, with the Fulani showing lower infection and disease rates and higher humoral responses to various P. falciparum antigens than sympatric ethnic groups. A total of 764 subjects (311 Mossi, 273 Rimaibé, and 180 Fulani) of all age classes were tested. The total mean +/- SE anti-(CSPf-N-term) and anti-(CSPf-C-term) seroprevalences were 65.6 +/- 1.7% and 57.0 +/- 1.8%, respectively. These seroprevalences were lower than that recorded in the same sample for the central (NANP)40 repetitive domain (88.3 +/- 1.2%). As previously reported for other P. falciparum antigens (PfCSP-(NANP)40, thrombospondin-related anonymous protein, merozoite surface protein-1, Pf155-ring-infected erythrocyte surface antigen, and Pf332), in spite of similar exposure to malaria, the Fulani showed higher immune reactivity than sympatric populations for both antigens tested. Our results confirm the presence of B cell epitopes in the non-repetitive regions of the PfCSP; moreover a further evidence of interethnic differences in the capacity to mount humoral responses against P. falciparum malaria was obtained. The assessment of the biological basis of interethnic heterogeneities in the susceptibility and in the humoral immune responses to malaria appears relevant in the development of anti-malaria vaccines.

Adolescent↗
PubMed1999

Population structure, speciation, and introgression in the Anopheles gambiae complex.

We review here what is known about the population structure and evolutionary dynamics of members of the Anopheles gambiae complex with emphasis on the situation in West Africa. First, the importance of the 2nd chromosome inversion polymorphism is demonstrated especially in adaptation to levels of aridity, a major environmental variable in Africa. This affects the distribution of karyotypes on both a macro- and micro-geographic scale as well as temporally. Such differentiation leads to karyotypes being differentially effective transmitters of malaria and differentially susceptible to indoor residual spraying of insecticides. Second, we review the evidence that cryptic taxa, especially in An. gambiae s.s., exist. This observation stems from both karyotype studies and molecular studies. It is abundantly clear that West African populations of An. gambiae s.s. are often not panmictic units, with premating factors evidently acting to maintain distinct genetic forms. Third, we review phylogenetic studies that have revealed the presence of introgression between the two most important vectors, An. gambiae and An. arabiensis. This is most evident for the 2nd chromosome inversions. This interpretation of phylogenetic data is consistent with a direct laboratory study indicating inversions in this chromosome are stably maintained in back-crossed populations. All of this information has led to the view that members of the An. gambiae complex are highly variable with an abundance of adaptive genetic variation. This presents a significant challenge to vector control programs designed to reduce malaria in sub-Saharan Africa.

Africa, Western↗
PubMed1999

Are chromosomal inversions induced by transposable elements? A paradigm from the malaria mosquito Anopheles gambiae.

Chromosomal rearrangements abound in nature and can be studied in detail in organisms with polytene chromosomes. In Drosophila and in Anopheline mosquitoes most speciation processes seem to be associated with the establishment of chromosomal rearrangements, particularly of paracentric inversions. It is not known what triggers inversions in natural populations. In the laboratory inversions are commonly generated by X-rays, mutagens or after the activity of certain transposable elements (TEs). The Anopheles gambiae complex is comprised of six sibling species, each one characterized by the presence of fixed paracentric inversions on their chromosomes. Two of these, An. gambiae s.s. and An. arabiensis, are the most important vectors of human malaria and are structured into sub-populations, each carrying a characteristic set of polymorphic chromosomal inversions. We have cloned the breakpoints of the naturally occurring polymorphic inversion In(2R)d' of An. arabiensis. Analysis of the surrounding sequences demonstrated that adjacent to the distal breakpoint lies a transposable element that we called Odysseus. Characteristics of Odysseus' terminal region and its cytological distribution in different strains as well as within the same strain indicate that Odysseus is an actively transposing element. The presence of Odysseus at the junction of the naturally occurring inversion In(2R)d' suggests that the inversion may be the result of the TEs activity. Cytological evidence from Drosophila melanogaster has also implicated the hobo transposable element in the generation of certain Hawaiian endemic inversions. This picture supports the hypothesis of the important role of TEs in generating natural inversions.

Animals↗
PubMed1999

Different response to Plasmodium falciparum in west African sympatric ethnic groups: possible implications for malaria control strategies.

The comparison of malaria indicators among populations with different genetic backgrounds and uniformly exposed to the same parasite strains, is one of the approaches to the study of human heterogeneities in the response to the infection. The results of our comparative studies conducted in Burkina Faso, West Africa, showed consistent interethnic differences in Plasmodium falciparum infection rates, malaria morbidity, prevalence and levels of antibodies to various P. falciparum antigens, and genetic background. The differences in the immune response were not explained by the entomological observations which indicated substantially uniform exposure to infective bites. The presence in the same epidemiological context of individuals characterized by different immune reactivity to malaria represents an ideal opportunity to study the possible relationships between the baseline level of anti-malaria immunity of a population and the protective efficacy of control measures based on the reduction of transmission. In spite of similar reduction of entomological inoculation rates obtained by permethrin-impregnated curtains, ethnic- and age-dependent efficacy was observed. These studies demonstrate the existence of marked interethnic differences in the susceptibility to P. falciparum malaria, probably involving the genetic regulation of humoral immune responses. These differences should be considered in the development of anti-malaria vaccines and in the evaluation and application of malaria control strategies.

Africa, Western↗
PubMed1999

Mosquito behavioural aspects of vector-human interactions in the Anopheles gambiae complex.

The behaviour of two of the most anthropophilic malaria vectors in the world, Anopheles gambiae Giles and An. arabiensis Patton, is revisited with respect to recent studies on their host preferences and the chemical ecology of host-seeking. Issues are discussed in relation to the ways anthropophily may have arisen in the complex, and the opportunities the study of olfaction and host-seeking behaviour offers to malaria control in Africa.

Animals↗
PubMed1999

The clay feet of the malaria giant and its African roots: hypotheses and inferences about origin, spread and control of Plasmodium falciparum.

Grassi's allegory of the fragile feet of clay of the malaria giant applies particularly to Plasmodium falciparum marginal populations in temperate climates such as those that spread within the last three thousand years in the Mediterranean area through their close association with non diapausing vectors of the Anopheles maculipennis complex. The winter survival of the vector and the successful completion of the sporogonic cycle depended on the availability of the house environment to the mosquito. The fragility of the parasite's cycle became especially evident with the crucial impact of indoor-sprayed residual insecticides resulting in very rapid malaria eradication. The malaria giant showed to possess much more solid feet in the Tropics where P. falciparum eventually reached an exceptionally stable endemicity in sub-Saharan Africa due to a vectorial system which produces inoculation rates far higher than the minimum necessary to saturate human populations. This very high transmissibility resulting from recent human-dependent speciation processes in Afrotropical Anopheles mosquitoes (namely the emergence in the Neolithic period of specifically anthropophilic taxa in the An. funestus and An. gambiae complexes) had probably a key influence on the origin of the modern P. falciparum from an ancestral, less pathogenic, taxon. It is hypothesised that under the prevalence of multiple inoculation during epidemic flashes, a fast growing, aggressive strain responsible for acute, short-lived infections was selected. This quickly replaced the ancestral taxon and spread all over the world taking advantage of previous Anopheles radiation and of the demographic expansion following the agricultural revolution. Dealing with the African 'roots' of the malaria giant means to face both the exceptional stability of the parasite cycle and the risk of disrupting the human natural response with unsustainable interventions. Most efforts should be concentrated in the support and improvement of the available anti-disease strategies whereas the development of effective anti-infection strategies should be mainly pursued through reasonably diversified research programmes and well monitored pilot interventions within a long-term perspective. The aim is to discover and test new anti-malarial tools which either alone or, more probably, integrated with the available measures, could allow the interruption of transmission. In most Afrotropical hyper- and holoendemic zones, once given full priority to strengthening disease control, P. falciparum eradication appears the only realistic anti-infection objective, unless it is demonstrated that progress can be achieved in these epidemiological zones through sustainable and cost-effective intermediate steps based on the reduction of infection prevalence.

Africa↗
PubMed1999

Salivary gland-specific gene expression in the malaria vector Anopheles gambiae.

Molecular studies on the tissue-specific gene expression in the salivary glands of Anopheles gambiae may provide useful tools for the development of new strategies for the control of the most efficient malaria vector in the sub-Saharan Africa. We summarize here the results of a recent investigation focused on the isolation of secreted factors and putative receptors from the salivary glands of An. gambiae. Using the Signal Sequence Trap technique we have identified the first cDNAs specifically expressed in the An. gambiae salivary glands. Among these, four are exclusively expressed in female glands and encode factors presumably involved in blood-feeding, whereas two other cDNAs seem to be expressed both in male and in female glands and are likely implicated in sugar-feeding. Homologues of genes previously identified in the yellow fever mosquito Aedes aegypti, like the apyrase and D7, as well as novel salivary gland-specific cDNAs, were identified. The isolation and characterization of promoter sequences from the corresponding genes may prove useful for the expression of anti parasitic agents in the salivary glands of transgenic mosquitoes.

Amino Acid Sequence↗
PubMed1999

Chromosomal and bionomic heterogeneities suggest incipient speciation in Anopheles funestus from Burkina Faso.

Sampling of day-resting Anopheles funestus was carried out in September-November 1991, October-December 1992, and November 1994 at two sites near Ouagadougou, Burkina Faso: the small village of Noungou where humans outnumber cattle, and the nearby Fulani settlement of Loumbila where cattle outnumber humans. Collections made inside human dwellings were supplemented in 1992 by outdoor-resting samples from artificial pit-shelters. Indoor-resting An. funestus were also collected in November 1992 and November 1994 in four villages of the Banfora area (southern Burkina Faso) and in a sudanese-sahelian village in northern Burkina Faso (Tougouri). Half-gravid female sub-samples were preserved in carnoy's fixative and processed for polytene chromosome analysis. The material from the two villages near Ouagadougou was analysed by ELISA to know (i) the human/animal origin of the blood meal; (ii) the infectivity for Plasmodium falciparum malaria; and (iii) the possible correlation of these parameters with chromosomal variants. A total of 1416 An. funestus could be scored for the whole polytenic complement, while the origin of the blood meal and circumsporozoite protein (CSP) positivity were asserted from 1076 and 1154 specimens, respectively. With a few exceptions, four polymorphic paracentric inversions (3a, 3b, 2a and 5a in decreasing order of frequency) were observed in all populations. Inversion 2s, whose breaking points include those of inversion 2a, was found only as the heterokaryotype 2s/+ floating at an overall frequency of 3.7% in two villages of the Banfora area and in the two sites near Ouagadougou. Two heterokaryotypes 2a/t out of 186 scored specimens were observed in different years from one village of the Banfora area. Wide variations in inversion frequencies were observed among the samples without consistent geographical or temporal clines. Highly significant departures from Hardy-Weinberg equilibrium were recorded for inversions 3a and 3b in most samples, with the alternative homokaryotypes (standard and inverted) significantly more frequent than expected. Conversely, inversion 5a was in Hardy-Weinberg equilibrium in most samples, whereas the 2a-s inversion system was intermediate between these extremes. However, a deficit of heterokaryotypes was apparent practically in all samples. Significantly higher frequencies of the standard homokaryotypes were recorded (i) in the exophilic samples collected in Loumbila for arrangement 3a; (ii) in the animal-fed sub-sample collected outdoors in Noungou vs. the parallel human-fed sub-sample for arrangements 2a-s, 3a, and 3b, or vs. the samples obtained from indoor catches in both Loumbila and Noungou in the case of inversion 3a; (iii) in the December CSP-negative sub-sample from Loumbila vs. the parallel CSP-positive sub-sample for arrangement 2a. A plausible working hypothesis is that An. funestus in Burkina Faso includes two taxonomic units, one of which is mainly monomorphic standard with most inverted arrangements floating at very low frequencies, and probably uniquely characterised by arrangement 2s, while the other taxon is nearly fixed for arrangement 3ab and polymorphic for all the other inversions at intermediate to high frequencies. The latter would be characterised by a higher vectorial capacity and would probably correspond to An. funestus s.s. from East Africa. About the former hypothetical taxon, its endophily and anthropophily appear less marked and its relationship with other members of the An. funestus subgroup will require specific investigations.

Animals↗
PubMed1998

Cloning of inversion breakpoints in the Anopheles gambiae complex traces a transposable element at the inversion junction.

Anopheles arabiensis, one of the two most potent malaria vectors of the gambiae complex, is characterized by the presence of chromosomal paracentric inversions. Elucidation of the nature and the dynamics of these inversions is of paramount importance for the understanding of the population genetics and evolutionary biology of this mosquito and of the impact on malaria epidemiology. We report here the cloning of the breakpoints of the naturally occurring polymorphic inversion 2Rd' of A. arabiensis. A cDNA clone that cytologically mapped on the proximal breakpoint was the starting material for the isolation of a cosmid clone that spanned the breakpoint. Analysis of the surrounding sequences demonstrated that adjacent to the distal breakpoint lies a repetitive element that exhibits distinct distribution in different A. arabiensis strains. Sequencing analysis of that area revealed elements characteristic of transposable element terminal repeats. We called this presumed transposable element Odysseus. The presence of Odysseus at the junction of the naturally occuring inversion 2Rd' suggests that the inversion may be the result of the transposable element's activity. Characteristics of Odysseus' terminal region as well as its cytological distribution in different strains may indicate a relatively recent activity of Odysseus.

Animals↗
PubMed1998

Humoral response to Plasmodium falciparum Pf155/ring-infected erythrocyte surface antigen and Pf332 in three sympatric ethnic groups of Burkina Faso.

The humoral immune response against synthetic peptides of two Plasmodium falciparum blood-stage antigens, Pf155/ring-infected erythrocyte surface antigen (RESA) (EENV)6 and Pf332 (SVTEEIAEEDK)2, in individuals belonging to three sympatric ethnic groups (Mossi, Rimaibe, and Fulani) living in the same conditions of hyperendemic transmission in a Sudan savanna area northeast of Ouagadougou, Burkina Faso were examined. The Mossi and Rimaibe are Sudanese Negroid populations with a long tradition of sedentary farming, while the Fulani are nomadic pastoralists partly settled and characterized by non-Negroid features of possible Caucasoid origin. A total of 764 subjects (311 Mossi, 273 Rimaibe, and 180 Fulani) were tested. A lower P. falciparum prevalence was observed in the Fulani of all age groups. The serologic results clearly indicate the existence of interethnic differences in the capacity to respond to these two P. falciparum antigens. The Mossi and Rimaibe showed similar responses, whereas the Fulani displayed consistently higher prevalences and levels of antibodies against both epitopes tested. The anti-(EENV)6 and anti-(SVTEEIAEEDK)2 seroprevalences were 29.9% and 38.9% in Mossi, 29.7% and 39.2% in Rimaibe, 86.1% and 76.1% in Fulani (all P values of Fulani-Mossi and Fulani-Rimaibe comparisons << 0.001). Anti-RESA and anti-Pf332 antibody levels were approximately 65% (P << 0.001) and 45% (P << 0.001), respectively, higher in seropositive Fulani than in seropositive Mossi and Rimaibe, who showed very similar values. The observed differences cannot be explained in terms of interethnic heterogeneity of malaria exposure since these communities have lived in the same area for more than 30 years and the P. falciparum inoculation rate, measured during two consecutive years, was substantially uniform for the three ethnic groups. The possibility of remarkable heterogeneities in the capacity to mount immune responses against P. falciparum antigens among populations with different genetic backgrounds must be taken into account in the development of anti-malaria vaccines.

Adolescent↗
PubMed1998

Odor-mediated host preferences of West African mosquitoes, with particular reference to malaria vectors.

The role of odors in mosquito host preferences was studied in a village near Ouagadougou, Burkina Faso. Two odor-baited entry-traps were put beside one another and a choice of host odor-laden air was blown out of them. Odors of a human and a calf (of similar mass) were drawn from two tents in which each was separately concealed. Allowances were made for trap position, differences in human-subject attractiveness, CO2 levels, and trap contamination with alternative host odors. Choices for the human-baited trap greater than the 0.5 random expectation were made by Anopheles gambiae s.l. (0.96) and An. pharoensis (0.68). The choices for the human-baited trap of Culex antennatus were significantly lower than 0.5 (0.25), whereas for the Cx. decens species group (0.56), the difference was not significant. Interpretation of the latter result was complicated by the significant effect of CO2 levels on the index. Species caught in low numbers but whose trap distribution showed a bias towards the human-baited trap were An. funestus (total numbers in the human-baited trap to the calf-baited trap = 9:0), Mansonia africana (17: 1), Aedes dalzieli (22:4), and Ae. hirsutus (13:1); species showing bias towards the calf-baited trap were An. rufipes (0:11), Cx. duttoni (0:17), and Cx. nebulosus (2:35). Mansonia uniformis was the only species distributed randomly between the two traps. Molecular identification of the An. gambiae s.l. samples revealed a marked difference in trap distribution: for the human-baited trap the ratio was 52% An. arabiensis to 48% An. gambiae s.s.; for the calf-baited trap, it was 92% An. arabiensis to 8% An. gambiae s.s.

Animals↗
PubMed1998

Baseline immunity of the population and impact of insecticide-treated curtains on malaria infection.

It has been shown that insecticide-treated bed nets or curtains may reduce morbidity and mortality from malaria in hyper-holoendemic areas of sub-Saharan Africa. This protection could partially depend on the transitory imbalance between the anti-malaria immunity acquired by the population before the intervention and the lowered sporozoite load resulting from the anti-vector measure. To verify if the efficacy of the intervention is influenced by the baseline immune status of the population, we compared the protective effect of permethrin-impregnated curtains (PIC) against malaria infection among groups with different baseline levels of anti-malaria immunity. We analyzed the impact of PIC on the Plasmodium falciparum infection rate in two rural villages of Burkina Faso inhabited by three ethnic groups: the Fulani, Mossi, and Rimaibé. These have been previously shown to differ for several malariologic indices, with the Fulani being characterized by lower infection and disease rates and by higher immune response to P. falciparum with respect to the other ethnic groups. The PIC were distributed in June 1996 and their impact on malaria infection was evaluated in groups whose baseline levels of immunity to malaria differed because of their age and ethnic group. Age- and ethnic-dependent efficacy of the PIC was observed. Among the Mossi and Rimaibé, the impact (parasite rate reduction after PIC installation with respect to the pre-intervention surveys) was 18.8% and 18.5%, respectively. A more than two-fold general impact (42.8%) was recorded in the Fulani. The impact of the intervention on infection rates appears positively correlated with the levels of anti-malaria immunity. Since decreased transmission entails a reduction of immunity, the efficacy of the intervention in the long term cannot be taken for granted. The expected complementary role of a hypothetical vaccine is stressed by these results, which also emphasize the importance of the genetic background of the population in the evaluation and application of malaria control strategies.

Animals↗