The mosquitoes of Sardinia: species records 35 years after the malaria eradication campaign

1. Thirty-five years ago malaria was eradicated from Sardinia by massive application of DDT directed against the mosquito vector species, Anopheles labranchiae, but the long-term effects on the mosquito fauna have not been investigated previously. 2. A 5-year mosquito survey (1980-85) involved in the inspection of 348 sites (plus 173 reinspections) and the processing of nearly 60,000 specimens. 3. Twenty-four species in six genera were identified from larval and adult collections. Species of the genera Culex (41%) and Aedes (22%) were more commonly encountered than Culiseta (18%) and Anopheles (17%) species. Orthopodomyia (1.6%) and Coquillettidia (0.6%) were far less frequent. 4. The species composition was similar to that described for the years of the eradication campaign, except for the genus Anopheles. Of the eight Anopheles species previously recorded, only four species were identified in collections of 1159 larvae from eighty-five positive sites. 5. Anopheles labranchiae was the most frequently collected species of its genus (49%), but was represented in only 12% of the total collections. Comparison with previous records indicated a progressive increase in sites positive for An.labranchiae over the past 35 years. 6. Anopheles hispaniola was not found, although it had apparently replaced An.labranchiae soon after the eradication campaign. An. labranchiae was common in the sites where the replacement phenomenon has been observed.     

Establishing the eradication unit of Molara Island: a case of study from Sardinia, Italy

Molara is a small island belonging to the Marine protected Area Tavolara—Punta Coda Cavallo, in Sardinia. During 2006–2007, a bio-monitoring program reported a strong presence of the black rat, Rattus rattus, on Molara island. Rat predation has detrimentally affected the unique biodiversity of this island, thus, in 2008 an eradication campaign was conducted. Our eradication protocol included a pre-eradication genetic investigation, using 8 microsatellite loci, on a rat population of Molara as well as on neighbour islands within the Marine Protected Area (MPA). The main goal of this genetic investigation was to establish the correct borders of the eradication unit of Molara island. As several recent eradication campaigns have been unsuccessful, due to incomplete and unstable eradication, we also aimed to assess possible hidden sources of reinvasion. Specimens were also collected during post- eradication monitoring on Molara for genetic screening to establish their origin, and thus validate the effectiveness of our eradication campaign. According to our genetic analysis, within the MPA there are four different eradication units, corresponding to the islands of Molara, Tavolara, Piana and to the Sardinia mainland. Gene flow among these four units is more or less absent. The assignment and clustering tests performed on pre and post-eradication samples seem to indicate that the population of Sardinia mainland is a possible source of re-invasion for the Piana and Molara populations.     

Cultural and genetic adaptations to malaria: Problems of comparison

The concept of adaptation has been used differently in studies of biological and cultural evolution, and this divergence raises the question of whether genetic and cultural adaptations are truly comparable. This paper compares genetic and cultural traits associated with endemic malaria in Sardinia, Italy. Thalassemia and G-6-Pd deficiency, two genetic traits of the Island's population, are believed to enhance fitness against malaria, despite increased risk for the diseases of thalassemia major and favism. Two cultural traits, a pastoral pattern of inverse transhumance and rules limiting the geographical mobility of lowland women, limited exposure to the malaria vector, Anopheles labranchiae; these are used as examples of cultural adaptations. The distribution, costs, and benefits of the adaptive cultural and genetic traits are compared, and the theoretical difficulties of finding a common measure of adaptive value are discussed.     

Parasitoses and development: malaria and echinococcosis]

After having placed emphasis on the cyclic oscillations characterizing the interest of the scientific and political world for parasitology, the author analyzes the various standpoints from which parasitic diseases, and above all malaria, have been dealt with ever since the beginning of this century. Specific criticism is addressed to the military model, which has provided the basis for many eradication campaigns. The author also analyzes the "vicious circle theory", which labelled the activity of the WHO in its first decade of life, and which assumed that breaking the disease and underdevelopment circle was possible by acting mainly or even exclusively on endemic and debilitating diseases. Both these models were tested with success in Sardinia with the 1947-49 antimalaria campaign. However, socio-economic development of the island did not occur as expected, and attempts to export the same approaches to other parts of the world soon disclosed their limitations, leading to major failures. The experience on the fight against echinococcosis is subsequently examined. The conclusions drawn are that many successes may be obtained through a systemic rather than a sectorial approach; and that a "conflicting cohabitation" with diseases is foreseen as a long-lasting reality, and must thus be controlled with the appropriate means.     

Reduced seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV), human herpesvirus 8 (HHV8), related to suppression of Anopheles density in Italy

In two formerly malarious parts of Italy, age-related seroprevalence rates of Kaposi's sarcoma-associated herpesvirus [human herpesvirus 8 (KSHV/HHV8)] were determined from local blood donors and correlated with periods of vector control during anti-malaria campaigns. In Veneto, decreased KSHV/HHV8 seroprevalence in the 1951-1955 birth cohort coincides with the peak of DDT house-spraying. In Sardinia, where larviciding augmented indoor DDT-spraying, a significant drop of KSHV/HHV8 seroprevalence between 1945 and 1950 and 1951-1955 birth cohorts (P = 0.0046) coincides with suppression of the malaria vector Anopheles labranchiae Falleroni (Diptera: Culicidae). These results are consistent with age-related association between KSHV/HHV8 seroprevalence rates in native/resident populations and the density of malaria vectors in Veneto and Sardinia. This example supports our 'promoter arthropod' hypothesis on the role of haematophagous insects [putatively blackflies (Simuliidae), sandflies (Phlebotominae) and biting midges (Ceratopogonidae), as well as mosquitoes] when their bites induce hypersensitivity and immunosuppression, potentiate KSHV/HHV8 transmission via human saliva (when insect bite lesions are licked by another person whose saliva carries the virus) and may facilitate Kaposi's sarcoma.     

Epidemiology in the strategies for malaria control

A rapid overview is presented of the evolution of the main orientations of malaria control, since the discovery of mosquito transmission. Stated control objectives appear to have oscillated between expectations to eradicate the vector, or at least the disease, and more modest approaches to minimise the effects of the infection. High optimism was raised when a new control measure, or new combination of existing measures, appeared to be highly effective and was expected to have universal applicability. The implementation of large scale campaigns eventually found the limits of applicability of the proposed strategy and the exaggerated expectations soon gave way to disillusion and, eventually, to a revival of research. The longest and most impacting period of exaggerated expectations was the global malaria eradication campaign of the 1950s and 1960s, which completely disregarded the study of local epidemiology, considering that all it was needed was to know if an area was "malarious" or not. Research was practically abandoned and, even when reinstated after the recognised failure of the campaign, it has retained an almost exclusive orientation towards the development of control tools, drugs or eventually vaccines. One of the earliest victims of the eradication campaign was the study of epidemic malaria and its determinants in different epidemic prone areas. In spite of an extremely long period of disillusion, lasting for almost two decades, the reality of the malaria problem led WHO and member countries to agree on a global strategy of control, aiming at a realistic use of existing tools, to at least reduce or prevent mortality. An essential element of this strategy is the prevention or control of malaria epidemics and the selective use of vector control, both of which have to be based on a solid knowledge of local epidemiology, the study of which has to rejoin the path abandoned fifty years ago.     

Design and implementation of a mosquito database through an entomological ontology

There have been constant changes in the biology and behavior of the vector and parasite involved in the transmission of malaria. There is limited interest in developing new technologies and procedures for controlling the underlying factors of this threat, which poses an enormous challenge to health systems. To understand the various vector species and their interrelations is of prime importance in understanding the transmission mechanisms of malaria in order to react efficiently. To attain this objective, we have used an ontological approach to producing a database that we consider to be our own contribution in helping to control malaria vectors if eradication has been unsuccessful in the previous control campaign.     

Adaptation to past malarial endemia and susceptibility to common diseases in modern populations: a study of adenosine deaminase and MN blood group genetic polymorphisms

We carried out a study of adenosine deaminase (ADA) and MN blood group genetic polymorphisms in relation to past malarial morbidity in Sardinia and in relation to susceptibility to allergic asthma (a Th2 disorder) and Crohn's disease (a Th1 disorder) in the population of Rome. Eight hundred and eight schoolchildren, aged 7--14 years from 14 Sardinian villages located in the central area of the island, were considered. One hundred and twenty-two children with allergic asthma and 39 adult patients with Crohn's disease from the population of Rome were also studied. The data suggest an interaction between the two systems concerning resistance/susceptibility, both to malaria and to the diseases considered. In Sardinia, the frequency of the *L(M)/ADA*2 gametic type is negatively correlated with past malarial endemia, suggesting an increased susceptibility to malaria leading to its decrease in areas with high malarial endemia. In Rome, this gametic type is correlated negatively to allergic asthma and positively to Crohn's disease, suggesting a protective effect against allergic asthma and increased susceptibility to Crohn's disease.     

Design and implementation of a mosquito database through an entomological ontology

There have been constant changes in the biology and behavior of the vector and parasite involved in the transmission of malaria. There is limited interest in developing new technologies and procedures for controlling the underlying factors of this threat, which poses an enormous challenge to health systems. To understand the various vector species and their interrelations is of prime importance in understanding the transmission mechanisms of malaria in order to react efficiently. To attain this objective, we have used an ontological approach to produce a database that we consider to be our own contribution in helping to control malarial vectors if eradication has been unsuccessful in the previous control campaign.     

Malaria control: achievements, problems and strategies

Even if history has not always been the Magistra vitae, Cicero expected it to be, it should provide, as Baas said, a mirror in which to observe and compare the past and present in order to draw therefrom well-grounded conclusions for the future. Based on this belief, this paper aims to provide an overview of the foundations and development of malaria control policies during the XX century. It presents an analysis of the conflicting tendencies which shaped the development of these policies and which appear to have oscillated between calls for frontal attack in an all-out campaign and calls for sustainable gains, even if slow. It discusses the various approaches to the control of malaria, their achievements and their limitations, not only to serve as a background to understand better the foundations of current policies, but also to prevent that simplistic generalisations may again lead to exaggerated expectations and disillusion. The first part of the paper is devoted to the development of malaria control during the first half of the century, characterised by the ups and downs in the reliance on mosquito control as the control measure applicable everywhere. The proliferation of "man-made-malaria", which accompanied the push for economic development in most of the endemic countries, spurred the need for control interventions and, while great successes were obtained in many specific projects, the general campaigns proposed by the enthusiasts of vector control faced increasing difficulties in their practical implementation in the field. Important events, which may be considered representative of this period are, on the campaign approach, the success of Gorgas in the Panama Canal, but also the failure of the Mian Mir project in India; while on the developmental approach, the Italian and Dutch schools of malariology, the Tennessee Valley and the development of malaria sanitation, included the so called species sanitation. The projection of these developments to a global scale was steered by the Malaria Commission of the League of Nations and greatly supported by the Rockefeller Foundation. Perhaps the most important contribution of this period was the development of malaria epidemiology, including the study of the genesis of epidemics and their possible forecasting and prevention. Although the great effectiveness of DDT was perhaps the main determinant for proposing the global eradication of the disease in the 1950s, it was the confidence in the epidemiological knowledge and the prestige of malariology, which gave credibility to the proposal at the political level. The second part deals with the global malaria eradication campaign of the 1950s and 1960s. It recognises the enormous impact of the eradication effort in the consolidation of the control successes of the first half of the century, as well as its influence in the development of planning of health programmes. Nevertheless, it also stresses the negative influence that the failure to achieve its utopian expectations had on the general disappointment and slow progress of malaria control, which characterised the last third of the century. The paper then analyses the evolution of malaria control funding, which often appears out of tune with political statements. The fourth part is devoted to the search for realistic approaches to malaria control, leading to the adoption of the global malaria control strategy in Amsterdam in 1992, and the challenge, at the end of the century, to rally forces commensurate with the magnitude of the problem, while aiming at realistic objectives. After discussing the conflicting views on the relations between malaria and socio-economic development and the desirable integration of malaria control into sustainable development, the paper ends with some considerations on the perspectives of malaria control, as seen by the author in early 1998, just before the launching of the current Roll Back Malaria initiative by WHO.     

Dealing with malaria in the last 60 years. A personal experience

Dealing with malaria in the last 60 years is seen by the author in the perspective of his own experience. His malaria work, which began in 1941, covered the study of the habits of the mosquitoes dwelling in the savanna country of Eastern Colombia and the effect on malaria transmission of the newly introduced DDT residual spraying. The success of the campaign he later directed in Sarawak and Brunei contributed to the launching by WHO of its global malaria eradication campaign. Further successful work in Uganda showed the possibility of effective control and even eradication in highland country but left unsolved the problem of how to interrupt transmission of holoendemic malaria in Africa. The author's work with WHO in the Middle East showed to what extent social and economic conditions could influence the course of a malaria campaign. This was also the experience in America, both in Colombia in the author's early work and later in Mexico during an evaluation of the national malaria programme. Development of insecticide resistance was also encountered in his career and the refractoriness of the European vectors was also observed in his work as a malariologist.     

The antimalaria campaign in Italy between control and eradication: the Sardinian experiment]

The aim of this paper is to examine historically the alternative between control and eradication of the infectious diseases, starting with the idea of eradication itself, a result of the Pasteurian revolution. The eradication of malaria in Italy is taken as a case study. Through an extensive use of the archival sources, the alternative between control and eradication is analysed for the first years of the Sardinian Project, directed by the Rockefeller Foundation, that resulted in the eradication of malaria in Sardinia. This program is compared with the different program, grounded in the Italian malariological tradition, that in the same years carried out the eradication of malaria in the rest of Italy.     

A research agenda for malaria eradication: vaccines

Vaccines could be a crucial component of efforts to eradicate malaria. Current attempts to develop malaria vaccines are primarily focused on Plasmodium falciparum and are directed towards reducing morbidity and mortality. Continued support for these efforts is essential, but if malaria vaccines are to be used as part of a repertoire of tools for elimination or eradication of malaria, they will need to have an impact on malaria transmission. We introduce the concept of "vaccines that interrupt malaria transmission" (VIMT), which includes not only "classical" transmission-blocking vaccines that target the sexual and mosquito stages but also pre-erythrocytic and asexual stage vaccines that have an effect on transmission. VIMT may also include vaccines that target the vector to disrupt parasite development in the mosquito. Importantly, if eradication is to be achieved, malaria vaccine development efforts will need to target other malaria parasite species, especially Plasmodium vivax, where novel therapeutic vaccines against hypnozoites or preventive vaccines with effect against multiple stages could have enormous impact. A target product profile (TPP) for VIMT is proposed and a research agenda to address current knowledge gaps and develop tools necessary for design and development of VIMT is presented.     

Fine-scale population genetic structure of a wildlife disease vector: the southern house mosquito on the island of Hawaii

The southern house mosquito, Culex quinquefasciatus, is a widespread tropical and subtropical disease vector. In the Hawaiian Islands, where it was introduced accidentally almost two centuries ago, it is considered the primary vector of avian malaria and pox. Avian malaria in particular has contributed to the extinction and endangerment of Hawaii's native avifauna, and has altered the altitudinal distribution of native bird populations. We examined the population genetic structure of Cx. quinquefasciatus on the island of Hawaii at a smaller spatial scale than has previously been attempted, with particular emphasis on the effects of elevation on population genetic structure. We found significant genetic differentiation among populations and patterns of isolation by distance within the island. Elevation per se did not have a limiting effect on gene flow; however, there was significantly lower genetic diversity among populations at mid elevations compared to those at low elevations. A recent sample taken from just above the predicted upper altitudinal distribution of Cx. quinquefasciatus on the island of Hawaii was confirmed as being a temporary summer population and appeared to consist of individuals from more than one source population. Our results indicate effects of elevation gradients on genetic structure that are consistent with known effects of elevation on population dynamics of this disease vector.     

Genetic effects of human migrations and isolation

This paper analyses how migrations, environment and epidemics interact to shape genetic variation in the moder human species. The gene mutation that makes humans resistant to malaria is a striking example of how disease can shape the human genome. In Europe malaria spread in coincidence with the arrival of populations from Asia Minor and eastern Mediterranean and was favoured by the spread of agriculture, by the sedentary conditions of life and the related demographic increase. Natural selection, generally, shape the gene pool of a population in order to fit a different environment. This is the reason because hemoglobinopathies and enzyme G6PD deficit are greatly spread in areas hit by malaria epidemic. These effects are particularly evident in isolated regions or in islands with low population density, e.g. Sardinia. Disasters such as epidemics may drastically reduced the size of a population, and the victims under such circumstances are not selected. As a result the survivors within this small population are unlikely to be representative of the original population in its genetic makeup, and this occurrence is known as “bottleneck effect”. Sardinia, for instance, was hit between 1300 and 1700 by several plague epidemics. Such events drastically reduced the total number of inhabitants; creating a local alteration in the gene frequencies, that have moulded the genetics of the population. This has brought about not only a differentiation with respect to other Mediterranean populations, but creating a variability inside the island.     

Evaluation of vector competence for West Nile virus in Italian Stegomyia albopicta (=Aedes albopictus) mosquitoes

West Nile virus (WNV) is a zoonotic arboviral pathogen transmitted by mosquitoes in a cycle that involves wild birds as reservoir hosts. The virus is responsible for outbreaks of viral encephalitis in humans and horses. In Europe, Culex pipiens (Diptera: Culicidae) is considered to be the main vector of WNV, but other species such as Stegomyia albopicta (=Aedes albopictus) (Diptera: Culicidae) may also act as competent vectors of this virus. Since 2008 human cases of WNV disease have been reported in northeast Italy. In 2011, new areas of southern Italy became involved and a first outbreak of WNV lineage 1 occurred on the island of Sardinia. On the assumption that a potential involvement of St. albopicta in WNV transmission cannot be excluded, and in order to evaluate the competence of this species for the virus, an experimental infection of an St. albopicta laboratory colony, established from mosquitoes collected in Sardinia, was carried out. The results were compared with those obtained in a colony of the main vector Cx. pipiens. The study showed St. albopicta collected on Sardinia to be susceptible to WNV infection, which suggests this Italian mosquito species is able to act as a possible secondary vector, particularly in urban areas where the species reaches high levels of seasonal abundance.     

Campaigns for the eradication of malaria in Tunisia: history and current situation

The authors recall the historic of the different campaigns conducted against the malaria in Tunisia. Started since 1903 under the direction of Charles Nicolle, these campaigns were taken over after the end of each world war. However it must be necessary to wait the last campaign from 1966 to 1972, to conclude at the eradication of the disease, in 1977, into the country. Since this date, the systematic control of malaria is always conducted in the country. This end control is objected to avoid the resurgence of this parasitic disease in Tunisia, for the number of imported cases is increasing and the country presents ecological conditions propitious to Anopheles.     

Behavioural responses of invasive American mink Neovison vison to an eradication campaign, revealed by stable isotope analysis

1.  The detrimental impacts of invasive, non-native species on islands are widely acknowledged and it is often best to act rapidly against such species, even where uncertainty exists over the best way to proceed. If management actions are evaluated and refined, using information learnt from the biology of culled animals, this uncertainty can be gradually reduced, increasing the likelihood of a successful outcome.
2.  American mink Neovison vison carcasses were collected as part of an eradication campaign on several islands of the Outer Hebrides, Scotland, and stable isotope analysis was used to describe ecological variation in this invasive non-native predator.
3.  Isotope profiles from individual mink whiskers demonstrated how behaviour at a population level changed markedly over time. As the eradication campaign progressed, mink increased their reliance on marine food sources and focused their activity on the coastline. Stable isotope analyses also demonstrated sex-related changes in foraging and ranging behaviour in relation to food resource availability on the two main island complexes.
4.   Synthesis and applications. Our findings contribute to the refinement of a campaign to extend the successful eradication of mink from Uist and Harris, to the whole of the Outer Hebrides archipelago, UK. They also highlight the potential for stable isotope approaches to provide more detailed postmortem information that can inform adaptive management of wildlife populations for conservation objectives.     

Harnessing genomics and genome biology to understand malaria biology

Malaria is an important human disease and is the target of a global eradication campaign. New technological and informatics advancements in population genomics are being leveraged to identify genetic loci under selection in the malaria parasite and to find variants that are associated with key clinical phenotypes, such as drug resistance. This article provides a timely Review of how population-genetics-based strategies are being applied to Plasmodium falciparum both to identify genetic loci as key targets of interventions and to develop monitoring and surveillance tools that are crucial for the successful elimination and eradication of malaria.     

Modeling the role of environmental variables on the population dynamics of the malaria vector Anopheles gambiae sensu stricto

ABSTRACT: BACKGROUND: The impact of weather and climate on malaria transmission has attracted considerable attention in recent years, yet uncertainties around future disease trends under climate change remain. Mathematical models provide powerful tools for addressing such questions and understanding the implications for interventions and eradication strategies, but these require realistic modeling of the vector population dynamics and its response to environmental variables. METHODS: Published and unpublished field and experimental data are used to develop new formulations for modeling the relationships between key aspects of vector ecology and environmental variables. These relationships are integrated within a validated deterministic model of Anopheles gambiae s.s. population dynamics to provide a valuable tool for understanding vector response to biotic and abiotic variables. RESULTS: A novel, parsimonious framework for assessing the effects of rainfall, cloudiness, wind speed, desiccation, temperature, relative humidity and density-dependence on vector abundance is developed, allowing ease of construction, analysis, and integration into malaria transmission models. Model validation shows good agreement with longitudinal vector abundance data from Tanzania, suggesting that recent malaria reductions in certain areas of Africa could be due to changing environmental conditions affecting vector populations. CONCLUSIONS: Mathematical models provide a powerful, explanatory means of understanding the role of environmental variables on mosquito populations and hence for predicting future malaria transmission under global change. The framework developed provides a valuable advance in this respect, but also highlights key research gaps that need to be resolved if we are to better understand future malaria risk in vulnerable communities.