Effects of three-hour restricted food access during the light period on circadian rhythms of temperature, locomotor activity, and heart rate in rats.

The effects of food on biological rhythms may influence the findings of chronopharmacological studies. The present study evaluated the influence of a restricted food access during the rest (light) span of nocturnally active Wistar rats on the 24 h time organization of biological functions in terms of the circadian rhythms of temperature (T), heart rate (HR), and locomotor activity (LA) in preparation for subsequent studies aimed at evaluating the influence of timed food access on the pharmacokinetics and pharmacodynamics of medications. Ten-wk-old male Wistar rats were housed under controlled 12:12 h light:dark (LD) environmental conditions. Food and water were available ad libitum, excepted during a 3 wk period of restriction. Radiotelemetry transmitters were implanted to record daily rhythms in T, HR, and LA. The study lasted 7 wk and began after a 21-d recovery span following surgery. Control baseline data were collected during the first wk (W1). The second span of 3 wk duration (W2 to W4) consisted of the restricted feeding regimen (only 3 h access to food between 11:00 and 14:00 h daily) during the L (rest span) under 12:12 h LD conditions. The third period of 3 wk duration (W5 to W7) consisted of the recovery span with ad libitium normal feeding. Weight loss in the amount of 5% of baseline was observed during W1 with stabilization of body weight thereafter during the remaining 2 wk of food restriction. The 3 h restricted food access during the L rest span induced a partial loss of circadian rhythmicity and the emergence of 12 h rhythms in T, HR, and LA. Return to ad libitum feeding conditions restored circadian rhythmicity in the manner evidenced during the baseline control span. Moreover, the MESORS and amplitudes of the T, HR, and LA 24 h patterns were significantly attenuated during food restriction (p < 0.001) and then returned to initial values during recovery. These changes may be interpreted as a masking effect, since T, HR, and LA are known to directly react to food intake. The consequences of such findings on the methods used to conduct chronokinetic studies, such as the fasting of animals the day before testing, are important since they may alter the temporal structure of the organism receiving the drug and thereby compromise findings.

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").

Lack of daily rhythms major modifications despite continuous infusion of melatonin in the rat.

The present study was conducted to evaluate the effect of melatonin on the daily rhythms of temperature, heart rate and locomotor activity in rats that received subcutaneously a continuous infusion of two different doses e.g. 1 and 5 mg/kg per day for seven days. Our results indicate that melatonin does not induce a loss of the daily rhythmicity of temperature, heart rate and locomotor activity. Whatever the dose, melatonin slightly modifies the main parameters of these rhythms e.g. a decrease of the amplitude of the daily rhythms of temperature and heart rate and an increase of the mesor of temperature. Taking into account these results obtained after constant rate delivery in normal rats, we plan now to investigate the effects of melatonin on our experimental model of Parkinson's disease (double bilateral intrastriatal 6-hydroxydopamine injection).

[Molecular identification of sibling Anopheles species: example of the Anopheles minimus and Anopheles dirus complexes, major malarial vectors in Southeast Asia]. / Identification moléculaire d'espèces jumelles d'anophèles: exemple des complexes Anopheles minimus et Anopheles dirus vecteurs majeurs du paludisme en asie du Sud-Est.

Effective control of malaria vectors requires precise identification of species. This is especially important within complexes of species that cannot be distinguished based on morphological features. Two methods based on polymerase chain reaction (PCR) analysis have been developed to identify 2 species in the Anopheles minimus complex and 5 species of the Minimums group as well as 4 species of the Anopheles dirus complex. Association of oligonucleotide couples in the form of multiplex PCR has allowed development of two simple, reliable PCR techniques adapted to each one of these species complexes that comprise the major vectors of malaria in Southeast Asia. Specifically designed to meet the needs of entomologist working in the field for reliable, cost-effective tests, these techniques will facilitate assessment of the geographical distribution of each vector. These data will help to better target vector control measures.

[Malaria vector control in Cameroon: past, present, future. Reflections]. / La lutte antivectorielle au Cameroun. Passé-présent-avenir. Réflexions.

During the fifties, large scale malaria vector control projects based upon house spraying were implemented in Southern and Northern parts of Cameroon in line of malaria eradication concept. In the South, the pilot zone of Yaounde gathered about 150,000 inhabitants, in the forest area. First operations started in 1953 but the programme became actually operational in 1956. It was divided in two parts: the western part was treated with DDT, while the eastern one was treated with dieldrin. At the same time, the whole forested area was also treated with dieldrin until 1960. Yaounde itself was not treated because it was free of anopheles and malaria. House spraying in the pilot area of Yaounde was a complete success and plasmodic index dropped below 1%. The same success was observed in most of the southern treated areas. Unfortunatly dieldrin resistance of An. gambiae hampered this programme which stopped in 1960. The northem pilot project dealt with some 250,000 inhabitants around Maroua, in a savanna area. To avoid dieldrin resistance observed in 1956, DDT was selected and house spraying started in 1959. From a strictly operational point of view, the campaign was considered as a success. But after two years, it was noticed that plasmodic index remained still around the same value of 35% and the programme stopped. It was thus stated that according to available techniques it was not possible to reach the ultimate goal of eradication even when chemoprophylaxis (chloroquin + pyrimethamin) was added. The comparison between south (= success) and north (= failure) was very interesting as it underlined the big differences between epidemiological faces, an unaccepted concept at that time. Now ecological and epidemiological diversity is the well acknowledged. It also underlined the need of diversity of strategies according to the epidemiology of the disease and the ecology of its vector Vector control was then stopped for a while. In the eighties, Primary Health Care was promoted and malaria control shifted from vector to parasite control, vector control remaining as a prevention method. But chemioresistance of Plasmodium falciparum appeared and. quickly spread, at different levels, across the country. A new emphasis was therefore given to vector control thank to the newly developed technique of insecticide impregnated mosquito nets. Two kinds of studies were undertaken: - what people were actually doing in term of mosquito control at family level, the main reason and the costs as well as current use of mosquito nets - the efficacy of pyrethroid treated mosquito nets (IMN) in different areas of southern forested area against different malaria vectors: An. gambiae, An. nili, An. moucheti. It thus clearly appeared that IMN were very successful in sharply reducing malaria transmission aAd morbidity. But its promotion is limited by the current poor use of mosquito nets in Yaoundé (1 mosquito net for 27 "beds") while in Douala, where IMN are largely used against the bite of the huge population of Culex. quinquefasciatus, the implementation of the first riational centre for impregnation of mosquito net was a great success, as long as it was headed by a motivated and skill manager Impregnated mosquito nets appear thus as a tool of great efficacy but their sustainability is still matter of concern and promotional campaigns must be developed involving private and public, political and scientific spheres as well as the general population who should be encouraged to become partners and even actors of vector and malaria control at their household level.

DDT house spraying and re-emerging malaria.

PIP: This article discusses the role of DDT in the re-emerging cases of malaria worldwide. It is noted that malaria is reappearing in urban areas and in countries that previously eradicated the disease, including the Amazon Basin, South and North Korea, Armenia, Azerbaijan, and Tajikistan. In addition, the frequency of imported malaria has also increased in industrial countries. Although many factors contribute to such a phenomenon, the strongest correlation is with decreasing numbers of houses sprayed with DDT. Early studies of DDT showed repellent, irritant, and toxic actions that worked against malaria vector mosquitoes. Sprayed on house walls, DDT exerted powerful control over indoor transmission of malaria. However, since the ban of DDT in the 1970s and the implementation of alternative malaria-control programs there has been a global outburst of malaria epidemics. In view of this, it is recommended that the global response to burgeoning malaria rates allow for DDT residual house spraying where it is known to be effective and necessary. Regulations and policies of industrialized countries and international agencies that block financial assistance to countries that use DDT for malaria control should be eliminated.^ieng

Effects of a seven-day continuous infusion of L-DOPA on daily rhythms in the rat.

The present study was conducted to evaluate the effect of L-3, 4-dihydroxyphenylalanine (L-DOPA) on the daily rhythms of temperature, heart rate and locomotor activity in rats that received a 7-day continuous infusion. Our results indicate that L-DOPA does not induce a loss of the daily rhythmicity of temperature, heart rate and locomotor activity but modifies the main parameters of these rhythms, e.g. it increased the MESOR (midline estimating statistic of rhythm) of temperature and heart rate and increased the amplitude of temperature but decreased the amplitude of heart rate. Taking into account these results obtained after constant rate delivery, we now plan to investigate the effects of DOPA therapy by changing the time of its administration.

Airport malaria : a rare disease still poorly understood.

The article by Daniel Lusina and colleagues in this issue of Eurosurveillance is a timely reminder of the dangers of airport malaria. Since 1977, when the disease was first documented, 75 cases of airport malaria have been observed in western Europe, 28 o

[Anopheline population genetics]. / Génétique des populations anophéliennes.

Population genetic studies of vectors are essential for (i) the determination of their taxonomic status and consequently the definition of their vectorial role in the transmission of pathogenic agents; (ii) the evaluation of the species genetic variability and the estimation of their capacities of adaptation to selection pressure; (iii) an estimation of gene flow among populations in order to evaluate their degree of isolation and gene circulation, especially resistance genes. Among the malaria vectors taken as examples on three continents, Africa, South-East Asia and Latin America, the large majority of the species showed an important polymorphism. The Gambiae Complex, which is by far the most studied one, includes at present 7 species with the recent description of An. quadriannulatus A and B from Ethiopia. An. gambiae s.s. includes itself 5 chromosomal forms. One of them, the Mopti form, should be considered as a species unto itself. For An. arabiensis, a strong differentiation has been observed among the populations from Senegal and the Indian Ocean Islands. The kdr mutation, which confers resistance to pyrethroid knockdown effect, has never been found either in the Mopti form, or An. arabiensis, indicating a restricted gene flow between these latter two and An. gambiae s.s. The speciation process of the Gambiae Complex seems to be a recent phenomenon due to environmental selection pressure. Species of the Funestus Group are distinguishable by morphological characters. The genetic study of An. funestus s.s. did not show the presence of a complex, in spite of high polymorphism and population structure. Anophelines from eastern areas present an important biodiversity. The Minimus Complex includes two species, A and C, which are widely distributed in South-East Asia. Species A is strongly endophilic, on the contrary species C is at once more exophilic and zoophilic. The latter species might have been selected by DDT indoor house spraying. After numerous taxonomic investigations, the Dirus Complex includes now 7 species. In Latin America, An. pseudopunctipennis clustered into three geographic populations which are under a speciation process. One covers North America and Guatemala, the other South America and Belize, whilst the last one is restricted to Grenada Island. On the contrary, An. darlingi showed little morphologic and genetic variability throughout the species geographic range suggesting the existence of a single species. The main objective of these studies is to implement a more selective approach of vector control programs in relation to the incriminated species, their bioecology and their role in malaria transmission. The improvement of efficiency and selectivity of vector control is becoming a major goal in order to make the best out of the available tools and control the impact of interventions on the environment.

[Epidemiological stratification of malaria in the Comoro archipelago]. / Stratification épidémiologique du paludisme dans l'archipel des Comores.

In the Comoros Islands, the level of malarial endemicity varies greatly from one island to the other, even though the total area (4 islands) covers less than 2,300 km2 and has a population of some 600,000 people only. The epidemiological stratification is based on the diversity of human and physical characterisation. They both determine the presence and the behaviour as well as the size of the vector's populations. Vectorial dynamics can explain varying levels of endemicity given parasitological indicators and specific morbidity. Analyzing these criteria shows up different epidemiological features and serves as a basic guideline for malaria control. The efficiency of this control depends on the relationships between the intensity and the length of the transmission, in the framework of protection mechanisms; it is of crucial importance for clinical treatment. Further elements are the age of the patient, the season and the geographic situation of the area. Stratification provides explanations for these relationships and helps to define antimalarial programmes adapting to each situation a range of therapeutic and antivectorial methods. The availability and accessibility of anti-malarial medicine is the minimum requirement for reducing mortality: domestic spray insecticides for reducing transmission are effective for several years and should be followed by the use of mosquito nets or curtains impregnated with pyrethrinoids, and in the particular case of Grande Comore, the use of larvivorous fish. As anywhere else, the economic development, which is dependent on political stability, is the essential basis for malaria control.

Status of pyrethroid resistance in Anopheles gambiae sensu lato.

The present study confirms the presence of pyrethroid resistance among Anopheles gambiae s.l mosquitos in Côte d'Ivoire and reports the observation of such resistance in two other countries in West Africa (Benin and Burkina Faso). Malaria vector populations from Cameroon (Central Africa), Senegal (West Africa) and Botswana (southern Africa) were found to be susceptible to pyrethroids. In the most resistant mosquito populations, resistance to permethrin was associated with reduced mortality, not only with respect to this compound but also towards deltamethrin. Moreover, a significant increase in knockdown time was observed in some mosquito populations before any decrease in mortality, suggesting that knockdown time could be a good indicator for the early detection of pyrethroid resistance. In view of the current extension of such resistance, there is an urgent need to set up a network in Africa to evaluate its development. It is also vital that the impact of this resistance on pyrethroid-impregnated bednets be assessed.

[Vectors and environmental factors in malaria]. / Vecteurs et facteurs d'environnement du paludisme.

Malaria is a major risk for more than two billion human beings on Earth, and is the cause of 700,000 to 2.5 million deaths per year. The causative factor, Plasmodium (four species), involves an asexual cycle in man and a sexual one in anopheline mosquitoes. The four species of Plasmodium are pathogenic for man but P. falciparum accounts for more than 90% of deaths. Only black Africans are refractory to P. vivax, a characteristic linked to the lack of Duffy antigen. Among the 400 species of anophelines so far recorded, less than 50 are recognized malaria vectors. Every one has its own geographic and ecological characteristics, which locally induce the epidemiological trends and its biodiversity. In a given site transmission depends on competent anopheline species, their infective rate and their biting rate. Inhabitants of endemic areas develop during infancy immunity which protect them during the rest of their lives. This immunity (premunition) between parasite and its host is acquired at an heavy price of infant mortality. It can decrease rapidly when people leave endemic areas. Because inhabitants of endemic areas continue to harbor asymptomatic parasites they become good parasite reservoirs. The diversity of epidemiological situations needs a diversification of malaria control measures. The prognosis of the evolution of malaria depends on control measures, applied or not, and on the evolution of climatic and anthropic environment, which are very hard to predict for the time being.

Diversity of malaria in rice growing areas of the Afrotropical region.

It is well known that 'in many instances the rice agrosystem perfectly fits the ecological requirements of pathogens or vectors' and in fact 'malaria, schistosomiasis and Japanese encephalitis are important vector-borne diseases associated with rice production in developing countries' (IRRI, 1987). In spite of these fears, rice cultivation has been on the increase in the African region in response to demographic and economic pressures. However, although rice fields provide suitable breeding places for Anopheles mosquitoes and rice cultivation leads to an increase in the biting rates, the species which are adapted to these sites are not the same in all parts of Africa. Several examples illustrate this phenomenon: An. funestus in the rice fields of Madagascar, An. pharoensis in saline water rice fields in the delta of the Senegal river, An. arabiensis in northern Cameroon and Burundi, An. gambiae Mopti form in the Kou Valley (Burkina Faso) and An. gambiae Savanna form in the rice fields of Kafine near Bouaké (Côte d'Ivoire). The vectorial capacities of these species are not the same and malaria inoculation rates are not necessarily increased in the riceland agroecosystem. The consequences for malaria of introducing rice cultivation depend on the situation before its introduction: it could be worsened in unstable malaria areas but not in stable malaria areas. Therefore, sound epidemiological and entomological knowledge are needed before causing any environmental modifications for agricultural purposes and there should be regular monitoring to avoid any outbreak.

[The anopheles of Niger]. / Les anophèles du Niger.

Nineteen species of Anopheles have been observed in the Republic of Niger but only Anopheles gambiae, An. arabiensis and An. funestus are of epidemiological importance as malaria vectors. The two species of the An. gambiae complex have the same breeding sites. But in a large part of the country they disappear all during the dry season because of the lack of adequate pools of water. Their survival is as yet an unexplained phenomenon. The most northern wet season distribution of An. gambiae complex, depending on the latitude of the intertropical front. An. funestus was no longer found after 1970 because its breeding places were destroyed both by dryness and human activity. The Republic of Niger is a border area between the palearctic Mediterranean biogeographical region and the Afrotropical one. Two different vectorial systems of malaria transmission are separated by the Sahara desert. The risk of importation of an African vector such as An. gambiae and a parasite such as Plasmodium falciparum must be considered. For the time being, the low volume of road traffic limits the risk but the construction of a paved Transsaharian highway with new human settlements and developing cultivated areas with irrigation increases the dangers of epidemic outbreaks in these oases.

[Chloroquine resistance and malaria control in Ivory Coast]. / Chloroquino-résistance et lutte antipaludique en Côte d'Ivoire.

We present here data from the Ivory Coast on the susceptibility of Plasmodium falciparum to chloroquine, obtained since the first chloroquine-resistant strains were discovered in 1987. Susceptibility was assessed using the WHO 7-day field test. Almost all the tests were carried out in the capital, Adidjan, and in the southern forest zone. The frequency of chloroquine resistance was below 30% in most cases, the actual frequency differing between regions. The frequency of R3 chloroquine-resistant P. falciparum was very low. Such resistant parasites were found only on an oil-palm plantation and in the south west of the country, probably due to the free medical care available at both locations. In general, access to health care is limited. Fevers attributed to malaria are generally treated at home using plants or incomplete courses of chloroquine. Our data suggest that R3 chloroquine-resistant P. falciparum strains are selected by repeated high doses of chloroquine, rather than by low doses. Thus, symptomatic treatment of uncomplicated malaria and treatment at home with the "correct" medication may be more effective than systematic medication, for limiting the level of chloroquine resistance in the parasite. Pyrethroid-resistant Anopheles gambiae s.l. is present in West Africa and this may reduce the short-term effectiveness of impregnated mosquito nets. In the absence of R3 chloroquine-resistant P. falciparum, self-medication at home may be a practical and realistic way to treat malaria. However, more knowledge about the effectiveness of anti-malaria drugs, their use in various social, cultural and economic environments and the geographical distribution of insecticide-resistant vectors is required before effective strategies can be designed. However, it would certainly be of value to consistently check the quality of anti-malaria drugs and to try to improve the effectiveness of self-medication at home.