Experimental investigation of the susceptibility of Italian Culex pipiens mosquitoes to Zika virus infection

We investigated the susceptibility of an Italian population of Culex pipiens mosquitoes to Zika virus (ZIKV) infection, tested in parallel with Aedes aegypti, as a positive control. We analysed mosquitoes at 0, 3, 7, 10, 14, 20 and 24 days after an infectious blood meal. Viral RNA was detected in the body of Cx. pipiens up to three days post-infection, but not at later time points. Our results indicate that Cx. pipiens is not susceptible to ZIKV infection.

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.

Probable autochthonous introduced malaria cases in Italy in 2009-2011 and the risk of local vector-borne transmission

We describe two cases of probable autochthonous introduced Plasmodium vivax malaria that occurred in 2009 and 2011 in two sites of South-Central Italy. Although the sources of the infections were not detected, local transmission could not be disproved and therefore the cases were classified as autochthonous. Sporadic P. vivax cases transmitted by indigenous vectors may be considered possible in some areas of the country where vector abundance and environmental conditions are favourable to malaria transmission.

Probable autochthonous introduced malaria cases in Italy in 2009–2011 and the risk of local vector-borne transmission

We describe two cases of probable autochthonous introduced Plasmodium vivax malaria that occurred in 2009 and 2011 in two sites of South-Central Italy. Although the sources of the infections were not detected, local transmission could not be disproved and therefore the cases were classified as autochthonous. Sporadic P. vivax cases transmitted by indigenous vectors may be considered possible in some areas of the country where vector abundance and environmental conditions are favourable to malaria transmission.

Impact of environmental changes and human-related factors on the potential malaria vector, Anopheles labranchiae (Diptera: Culicidae), in Maremma, Central Italy

The Maremma Plain (central Italy) was hyper-endemic for malaria until the mid-20th century, when a national campaign for malaria elimination drastically reduced the presence of the main vector Anopheles labranchiae Falleroni. However, the introduction of rice cultivation over 30 yr ago has led to an increase in the An. labranchiae population and concern over possible malaria reemergence. We studied the impact of anthropogenic environmental changes on the abundance and distribution of An. labranchiae in Maremma, focusing on rice fields, the main breeding sites. Adults and larvae were collected in three main areas with diverse ecological characteristics. Data were collected on human activity, land use, and seasonal climatic and demographic variations. We also interviewed residents and tourists regarding their knowledge of malaria. Our findings showed that the most important environmental changes have occurred along the coast; An. labranchiae foci are present throughout the area, with massive reproduction strictly related to rice cultivation in coastal areas. Although the abundance of this species has drastically decreased over the past 30 yr, it remains high and, together with climatic conditions and the potential introduction of gametocyte carriers, it may represent a threat for the occurrence of autochthonous malaria cases. Our findings suggest the need for the continuous monitoring of An. labranchiae in the study area. In addition to entomological surveillance, more detailed knowledge of human-induced environmental changes is needed, so as to have a more complete database that can be used for vector-control plans and for properly managing emergencies related to autochthonous introduced cases.

[Assessment of malaria resurgence risk in Morocco. Study of the vectorial capacity of Anopheles labranchiae in a rice cultivation area in the north of the country]

To assess the malaria reintroduction risk in Morocco, we analyzed the malariogenic potential of a rice cultivation area in the north of the country. Our results showed that the receptivity of this area is very high during all the period of the rice cultivation, from May to October, the vectorial capacity of An. labranchiae, malaria vector in Morocco, is considerably high during the summer which corresponds to the rice cultivation period. The risk of autochthonous malaria resumption is important because of the possible presence of gametocytes carriers in the last malaria focus which is bordering the study area. The risk of a tropical malaria introduction is unimportant seen the low vulnerability of the area and the uncertain competence of its vectors considered. However, this risk must be considered with a more attention.

An overview of the lesson learned in almost 20 years of fight against the "tiger" mosquito

Since its introduction in Italy in 1990, Aedes albopictus has spread quickly across the country, being at present reported in scattered foci in all regions below 600 m of altitude. The most important items of the lesson learned in almost 20 years of fight against the "Tiger" in Italy are here reported and discussed.

Aedes albopictus in Rome: results and perspectives after 10 years of monitoring

In 1997, Aedes albopictus (Skuse 1894) was detected in Rome in two opposite areas of the city. In the following 2 years, the species quickly spread. In 2000, scattered foci of the species were reported in the whole urban area and in the outskirts of the capital city. In Rome, Ae. albopictus seems to have found optimal environmental conditions to proliferate and to overwinter through and without diapausing eggs. In ten years Ae. albopictus has colonized the whole urban area through three phases: first massive spread, following maintenance of infestation, and colonization of alternative winter breeding sites with favorable climatic conditions. Data collected during the 2007 show that rainfall is no longer the most important factor for the development of the species, with respect to the past. In fact Ae. albopictus probably has found new alternative larval breeding sites through the colonization of small water collections refilled periodically by human activities. During 2007-2008 winter season, in order to evaluate the species adaptability, a study of eggs hatching and length of larval cycle at low temperatures, was carried out in laboratory and in simulated field conditions. Data and results are showed and discussed also by the light of existing literature.

Infection with chikungunya virus in Italy: an outbreak in a temperate region

BACKGROUND

Chikungunya virus (CHIKV), which is transmitted by Aedes spp mosquitoes, has recently caused several outbreaks on islands in the Indian Ocean and on the Indian subcontinent. We report on an outbreak in Italy.

METHODS

After reports of a large number of cases of febrile illness of unknown origin in two contiguous villages in northeastern Italy, an outbreak investigation was done to identify the primary source of infection and modes of transmission. An active surveillance system was also implemented. The clinical case definition was presentation with fever and joint pain. Blood samples were gathered and analysed by PCR and serological assays to identify the causal agent. Locally captured mosquitoes were also tested by PCR. Phylogenetic analysis of the CHIKV E1 region was done.

FINDINGS

Analysis of samples from human beings and from mosquitoes showed that the outbreak was caused by CHIKV. We identified 205 cases of infection with CHIKV between July 4 and Sept 27, 2007. The presumed index case was a man from India who developed symptoms while visiting relatives in one of the villages. Phylogenetic analysis showed a high similarity between the strains found in Italy and those identified during an earlier outbreak on islands in the Indian Ocean. The disease was fairly mild in nearly all cases, with only one reported death.

INTERPRETATION

This outbreak of CHIKV disease in a non-tropical area was to some extent unexpected and emphasises the need for preparedness and response to emerging infectious threats in the era of globalisation.

Aedes albopictus and Culex pipiens implicated as natural vectors of Dirofilaria repens in central Italy

To identify the natural vectors of Dirofilaria repens Railliet et Henry, entomological samplings were carried out in four sites within the Lazio region, foci of canine subcutaneous dirofilariasis. Collections were made in 2002-2003 by means of dog-baited and miniature Centers for Disease Control and Prevention traps as well as on humans. Microscopy identified 1576 attracted mosquito females as belonging to six species, but molecular diagnostics detected filarial DNA only in Culex pipiens L. and Aedes albopictus (Skuse, 1894). Dirofilaria immitis Leidy DNA, D. repens DNA, or both were found in the head and thorax of both mosquitoes. The simultaneous presence of vectors showing diurnal and nocturnal activity patterns is of concern for animal and human health. The finding of D. immitis DNA in mosquitoes in areas where only D. repens was been recovered in dogs also demonstrates that this filarial parasite circulates among carnivores (wild or domesticated pets).

High levels of human chitotriosidase hinder the formation of peritrophic membrane in anopheline vectors

In the Anopheles midgut, Plasmodium falciparum produces a specific chitinase able to penetrate the blood meal surrounding the chitin-containing peritrophic membrane (PM). High levels of an analogous chitinase, chitotriosidase (CHIT), may be found in human blood, being the markers of macrophage activation. To verify the hypothesis that CHIT present in malaria patient blood could help parasite to overcome PM, we carried out a bioassay by feeding Anopheles stephensi females on an artificial apparatus that contained human blood from four different sources and with different chitinase concentrations: (1) healthy donors, as negative controls; (2) patients with malaria; (3) patients with Gaucher disease; and (4) whole blood enriched with commercial P. falciparum chitinase, as positive controls. After 16, 20 and 24 h of bloodfeeding, mosquitoes were dissected to extract the midgut and assess the effect of the different chitinases on membrane structure. Optical microscopy showed that formation of PM was clearly complete after 16 h in the posterior midgut from Anopheles already fed with healthy donor bloods. By contrast, PM formation was visible after 16 h in the posterior midgut of mosquitoes fed with malaria and Gaucher patient bloods but appeared clearly damaged at 20 and 24 h. At the same time, the PM formation was almost completely inhibited in the midgut of Anopheles fed with P. falciparum chitinase-enriched bloods. These alterations were clearly confirmed by transmission electronic microscopy. In the present paper, we demonstrate that human CHIT from different sources is active on anophelines' PM.

Laboratory evaluation of the bioinsecticide Spinosad for mosquito control

Spinosad, a naturally occurring product of the fermentation of the bacterium Saccharopolyspora spinosa, is a highly effective bioinsecticide against a broad range of agriculturally important insect pests, and this agent has an excellent environmental and mammalian toxicological profile. In this study the efficacy of a Spinosad-based product (Laser 4.8% emulsifiable concentrate) was evaluated in laboratory bioassays against laboratory-reared mosquito strains of 3 species of medical importance: Aedes aegypti, Anopheles stephensi, and Culex pipiens. Spinosad was particularly effective against larval Aedes and Culex, with a less marked activity against anophelines (24-h median lethal concentration = 0.0096, 0.0064, and 0.039 mg/liter, respectively), showing a persistence of the insecticide action of about 6 wk in laboratory containers. The activity of the Spinosad-based product against adult mosquitoes (toxicity by ingestion and a possible irritant or repellent effect on gravid females) also was evaluated. Results are discussed and compared with those available in the literature.

[Note on Anopheles maculipennis complex in Morocco]

Anopheles belonging to Anopheles maculipennis complex, collected from February to June 2002 in eight provinces of Morocco (Khouribga, Taounate, Alhouceima, Chefchaouen, Fes, Khemisset, Kalaa Sraghna and Benslimane), were identified with characterization of the ribosomal DNA by PCR and ITS2 sequence analysis. The results of this study showed that all the identified specimens belong to the Anopheles labranchiae species.

Potential vectors of West Nile virus following an equine disease outbreak in Italy

In the late summer of 1998, an outbreak of equine encephalomyelitis due to West Nile virus (WNV) occurred in the Tuscany region of central Italy. The disease was detected in 14 race horses from nine localities in four Provinces: Firenze, Lucca, Pisa and Pistoia. The outbreak area included Fucecchio wetlands (1800 ha), the largest inland marsh in Italy, and the adjacent hilly Cerbaie woodlands with farms breeding horses. To detect potential vectors of WNV, entomological surveys of Fucecchio and Cerbaie were undertaken during 1999-2002 by collecting mosquito larvae from breeding sites and adult mosquitoes by several methods of sampling. Among 6023 mosquitoes (Diptera: Culicidae) collected, 11 species were identified: Aedes albopictus (Skuse), Ae. vexans (Meigen), Anopheles atroparvus Van Thiel, An. maculipennis Meigen s.s., An. plumbeus Stephens, Culex impudicus Ficalbi, Cx. pipiens L., Culiseta longiareolata Macquart), Ochlerotatus caspius (Pallas), Oc. detritus (Haliday) and Oc. geniculatus (Olivier). In Fucecchio marshes, Cx. impudicus predominated with seasonal peak densities in spring and autumn: its greatest abundance during early spring coincides with arrival of migratory birds from Africa. In Cerbaie hills, Cx. pipiens predominated with peak population density in late summer. No viruses were isolated from 665 mosquitoes processed. These findings, plus other data on Italian mosquito bionomics, suggest a possible mode of WNV transmission involving the most abundant Culex in the Fucecchio-Cerbaie areas. Culex impudicus, being partly ornithophilic, might transmit WNV from migratory to non-migratory birds during springtime; Cx. pipiens, having a broader host range, would be more likely to transmit WNV from birds to horses and, perhaps, to humans by late summer.

First finding of Dirofilaria repens in a natural population of Aedes albopictus

The invasive mosquito Aedes albopictus (Skuse) (Diptera: Culicidae) has become widespread in Italy during the past decade. Also Italy has foci of canine filariasis caused by Dirofilaria (Spirurida: Onchocercidae), due to subcutaneous D. repens Railliet & Henry as well as the dog heartworm D. immitis (Leidy) transmitted by various vector mosquitoes (Diptera: Culicidae). In 2002, at Fiumicino, west of Rome (Lazio Region), 17% of dogs were found to have D. repens microfilariae in peripheral blood. To evaluate the role of Ae. albopictus as a vector of Dirofilaria in this area, female mosquitoes were collected daily, June-October 2002, landing on dog or human bait in a rural house at Focene. Mosquitoes were maintained at 27 degrees C and 70% RH for 6 days, to allow development or purging of filaria larvae, then identified and frozen for subsequent molecular assay with filaria-specific ribosomal S2-S16 primers. To distinguish specimens harbouring infective L3 Dirofilaria larvae, DNA was extracted separately from the mosquito abdomen and head-thorax. Dirofilaria species were identified by sequencing, confirmed by polymerase chain reaction of positive specimens using primers specific for D. immitis and D. repens. Dirofilaria DNA was detected in 3/154 (2%) of Ae. albopictus females examined: D. repens DNA in head-thorax and abdomen of one collected 27th July; D. immitis in the abdomen of one collected 24th September; DNA of both D. immitis and D. repens in the head-thorax of one collected 11th October 2002. Thus Ae. albopictus is a potential vector of both Dirofilarias in Italy, representing risks for veterinary and human health.

[Insecticide sensitivity in malaria vectors in high altitude Madagascar after five years of vector control]

In 1991, Anopheles gambiae and Anopheles funestus, the main malaria vectors in the Highlands of Madagascar, were reported to be fully susceptible to DDT; nevertheless a slight decrease in the susceptibility levels was recorded when compared with previous assays carried out in 1962. From 1993 to 1997, five cycles of indoor residual spraying have been carried out in the Highlands: a total of 1,482,000 kg of 70% wp DDT have been used for the treatment of houses and animal shelters. From 1996 to 1999, adult mosquito susceptibility tests to DDT and to some pyrethroids (lambdacyalothrine, deltamethrine, permethrine and cyfluthrine) have been carried out on samples collected in 20 areas of the Highlands. Bioassays were carried out following the WHO standard method. All tested populations of An. funestus showed a full susceptibility to DDT. An. gambiae showed a widespread decrease in the susceptibility to DDT, particularly marked in the region of the capital city Antananarivo. Both species were susceptible to pyrethroids.

[Aedes albopictus in Rome: monitoring in the 3-year period of 1998-2000]

Aedes albopictus was first reported in Italy in 1990 and in the urban area of Rome in the late summer 1997. Ae. albopictus is a daytime, outdoor mosquito, that bite preferably on man. In Rome (42 degrees South of latitude), larvae are found from March to November, but some adult females are active until December. The peak of adult abundance, and then of the annoyance caused to man, occurs in late August-September. The presence of the species in Rome represents the first example in Italy of extensive colonization of an urban area, with involvement of hundred-thousand people. Since 1997, Ae. albopictus has spread quickly from the initial foci to the whole city. In 2000, scattered foci of the species have been reported throughout the urban area and in some towns of the province.

[Aedes albopictus in Italy: an underestimated health problem]

Since 1990, Ae. albopictus has spread in 9 regions and 30 provinces of the country. This species was introduced in Italy in shipments of scrap tires form the USA. In Italy, Ae. albopictus is the major biting pest throughout much of its range and, although there is no evidence that this mosquito is the vector of human disease in the country, the species might be involved in the transmission of some arboviruses which have been reported in the Mediterranean Basin. Aim of this paper is to provide an update on the distribution of Ae. albopictus in Italy and to renew the interest in a problem frequently underestimated. Public health implications after a ten-year presence of the species are also discussed.

Anopheles sacharovi (Diptera: Culicidae): a reemerging malaria vector in the Ararat Valley of Armenia

In 1994, the first indigenous case of malaria since the 1960s was reported in Armenia, and the number of cases quickly increased in the ensuing years. In 1998, a roll-back malaria program was developed to eliminate the recently established foci of malaria infection and to prevent the reestablishment of malaria in Armenia. As part of this program, we carried out entomological surveys to identify the potential malaria vectors in the Ararat Valley, the area where most of the indigenous malaria cases had been reported. In particular, we attempted to ascertain the presence of Anopheles sacharovi Favre, which is historically the most important malaria vector in Armenia yet which had not been reported since 1965. In 1998-2000, we collected adult mosquitoes and larvae in the city of Masis and in three rural villages of the Ararat Valley. Species identification of the members of the Anopheles maculipennis complex was performed through egg and larval morphology, heteroduplex analysis, and sequencing of the second internal transcribed spacer of ribosomal DNA. Two species of the complex were identified: An. sacharovi, found in all of the study sites, andAn. maculipennis s.s. Meigen, the most common species in the area. The reemergence of An. sacharovi in the study sites shows that the receptivity for malaria is still high in the Ararat Valley and, likely, in other regions of Armenia.

Impact of the malaria control campaign (1993-1998) in the highlands of Madagascar: parasitological and entomological data

Malaria transmission in the central highlands of Madagascar was interrupted in the 1960s by a national control program that used DDT indoor spraying and mass treatment with chloroquine. At the end of the 1980s in this region, epidemic malaria reappeared. Italian health authorities provided technical assistance to the National Malaria Control Program since the beginning of the resurgence of malaria in the central highlands. Yearly residual house spraying performed for 5 years (1993-1998) and the availability of antimalarial drugs reduced malaria transmission to very low levels, with improvement in parasitologic and entomologic indexes. A significant reduction of malaria prevalence was observed in the villages located at altitudes of 1,000-1,500 m, corresponding to the stratum of unstable malaria that was the main target of the antivector interventions. A significant reduction of malaria prevalence was also observed in the villages located at altitudes of 900-1,000 m, where malaria transmission is stable. The main vector Anopheles funestus was dramatically reduced in abundance and distribution in the sprayed areas.

Malaria incidence and mortality in Italy in 1999-2000

In 1999-2000, a total of 2060 malaria cases were reported by the ISS. Most of the patients took inappropriate treatments or did not have any prophylaxis. Ninety-three per cent became infected in African malarious countries, 4% in Asian countries, and 3% in Latin America. P. falciparum accounted for 84% of the cases, followed by P. vivax (8%), P. ovale (5%), and P. malariae (2%). Deaths corresponded to an annual case fatality rate of 0.3% in 1999 and 0.5% in 2000. In general, imported malaria cases reflect the number of Italian travellers who underestimate the infection risk in Asian and Latin American malarious countries and permanent residents of African origin who visit their relatives in their native countries.

Could malaria reappear in Italy?

Because of concern about the possible reintroduction of malaria transmission in Italy, we analyzed the epidemiologic factors involved and determined the country's malariogenic potential. Some rural areas in central and southern Italy have high receptivity because of the presence of potential malaria vectors. Anopheles labranchiae is probably susceptible to infection with Plasmodium vivax strains, but less likely to be susceptible to infection with P. falciparum. Its vulnerability is low because of the low presence of gametocyte carriers (imported cases) during the season climatically favorable to transmission. The overall malariogenic potential of Italy appears to be low, and reintroduction of malaria is unlikely in most of the country. However, our investigations showed that the malaria situation merits ongoing epidemiologic surveillance.

Identification of the sibling species of the Anopheles maculipennis complex by heteroduplex analysis

The group of anopheline mosquitoes referred to as 'Anopheles maculipennis complex' includes the most important malaria vectors of the Palearctic Western region. The species belonging to this complex, however, are difficult or impossible to distinguish by morphological characters. To differentiate sibling palearctic species belonging to this complex, interspecific differences in the ITS2 sequences were used to set up a rapid and sensitive diagnostic tool based on heteroduplex analysis. The relative heteroduplex mobility allowed the following seven species to be readily distinguished: An. atroparvus, An. labranchiae, An. maculipennis s.s. , An. martinius, An melanoon, An. messeae and An. sacharovi.

Laboratory and field evaluation of metallic copper on Aedes albopictus (Diptera: Culicidae) larval development

Laboratory bioassays and field trials were carried out to study the effect of metallic copper on the development of Aedes albopictus (Skuse). Multiwire electric cable was used as a source of metallic copper. Three different doses were used in laboratory tests (5, 10, and 20 g/liter) and two in field tests (20 and 40 g/liter). In the laboratory, 10 g/liter induced high mortality and a lack of development in Ae. albopictus larvae and doses of 20 g/liter completely inhibited development. Larval mortality was higher in earlier instars than in third through fourth instars and pupae. No effects were reported on egg hatching. Copper ion concentration in water increased up to 574 ppb for 5 g/liter dose, 710 ppb for 10 g/liter dose, and 1,210 ppb for 20 g/liter dose, within week 6. The increasing concentration of copper in water was correlated positively with the decreasing production of adults. Copper ions concentration < 500 ppb did not or only slightly affected larval development and mortality of Ae. albopictus in laboratory tests. Copper concentrations between 500 and 1,000 ppb delayed larval development and caused high mortality. Copper concentrations > 1,000 ppb inhibited larval development completely killing all the larvae. This last result has been achieved by the use of a 20 g/liter dose of metallic copper in water. Copper also affected adult weight. In field trials, 20 g/liter reduced the number of larvae in treated pots by 90%, and 40 g/liter completely prevented oviposition. Moreover, the persistence of the toxic action of metallic copper in the field lasted for several months.

Phylogenetic relationships of seven palearctic members of the maculipennis complex inferred from ITS2 sequence analysis

The sequences of the second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) were determined from seven palearctic mosquitoes species belonging to the Anopheles maculipennis species complex, namely An. atroparvus, An. labranchiae, An. maculipennis, An. messeae, An. melanoon, An. sacharovi and An. martinius. The length of the ITS2 ranged from 280 to 300 bp, with a GC content of 49.4-54.1%. With the exception of An. messeae, negligible levels of intraspecific polymorphism and no intrapopulation variation were observed. The phylogenetic relationships among the members of the maculipennis complex were inferred by maximum-parsimony analysis of the PAUP program and the neighbour-joining and maximum-likelihood analysis of the PHYLIP program. All of the trees obtained were almost identical in topology, although the relationships among three species, i.e. An. maculipennis, An. messeae and An. melanoon, remained unresolved. The phylogenies were in good agreement with the previous gene-enzyme and polytene chromosome banding pattern studies.

Current status of Aedes albopictus and Aedes atropalpus in Italy

Eight years after the 1st record in Italy, scattered foci of Aedes albopictus are reported in 9 regions and 107 municipalities belonging to 22 provinces, mainly located in the northeastern part of the country (Veneto region). In almost all infested areas the species is well controlled and at low levels of density, through source reduction and antilarval treatments. Aedes atropalpus, 1st recorded in 1996, remains limited to the original focus in the province of Treviso. Surveillance and control of both species are carried out by local health agencies within a national program coordinated by Istituto Superiore di Sanità (national Institute of Public Health).

Malaria surveillance in Italy: 1997 analysis and 1998 provisional data

Malaria is the commonest imported infectious disease in Italy. Malaria was endemic throughout much of the country until it was eradicated nearly 50 years ago. Since then, a malaria surveillance system has been set up to detect locally acquired cases that

[Zooprophylaxis: old and new problems]

In the present note the authors report on the most important works which have examined the application of zooprophylaxis as a means for malaria control from the onset of this century to the present day. The method of zooprophylaxis has evolved throughout the years in close connection with other problems, undoubtedly more important in the history of malaria, which in the present paper are amply discussed. From the very beginning this subject was the object of heated debates by those who retained it a valid method of malaria control and those who denied its validity, among whom some of the most important Italian and foreign malariologists. The experiments of zooprophylaxis received most attention in the twenties, but, following the works of Missiroli and co-workers in the early thirties by which the varieties of the "complex maculipennis" were identified, the interest on zooprophylaxis was less heightened. It should be noted, however, that the increase of cattle, and especially land reclamation, reduced considerably malaria endemicity in northern Italy where zoophilic varieties were most prevalent. Recently, renewed interest on zooprophylaxis has been shown in Pakistan, where some experiments on the use of cattle have led to an unexpected increase of malaria transmission.

Malaria in Maremma, Italy

BACKGROUND

In August, 1997, a woman with no history of travel to malarious regions developed Plasmodium vivax malaria. She lived in a rural area of Italy where indigenous Anophyles labranchiae mosquitoes were present.

METHODS AND FINDINGS

An environmental investigation was done within a 3 km radius of the patient's house. Adult mosquitoes and larvae were collected and examined by PCR with the gene for plasmodium circumsporozoite protein as target. About 200 people living in the area were interviewed to detect possible carriers of P. vivax.

FINDINGS

None of the mosquitoes captured were carrying any malarial organisms. The house-to-house investigation identified a 7-year-old girl who had had a feverish illness a few days after her arrival in Italy from India, and who, 3 months later, still had P. vivax in her blood; she and her mother had antimalarial antibodies.

INTERPRETATION

These investigations suggest that the index case of malaria was caused by local anopheline mosquitoes infected with exogenous P. vivax.

[Resistance to organophosphate insecticides in Culex pipiens L. (Diptera: Culicidae) and first signal of the presence of A5-B5 esterase in Italy]

After a short review on insecticide resistance in mosquitoes, the results of a study on organophosphate (OP) resistance, carried out on 2 Culex pipiens L. field populations from North-eastern Italy, are reported. The A1 an A4-B4 or A5-B5 esterases were detected in our sample by starch gel electrophoresis. In order to differentiate between A4-B4 and A5-B5 esterases, restriction fragment length polymorphism (RFLP) analysis at the esterases B locus was performed: both A4-B4 and A5-B5 aplotipes were found in one of the studied populations. This is the first record of A5-B5 esterases in continental Europe.

Identification of a North American mosquito species, Aedes atropalpus (Diptera: Culicidae), in Italy

In late September 1996, during a routine survey for Aedes albopictus in Italy, a population of Aedes atropalpus s.s. was discovered in the Veneto Region (northern Italy). Larvae were collected in 2 tire storage areas belonging to tire recapping companies that imported loads of car and large equipment used tires from eastern Europe and North America. Aedes atropalpus is found only in North America and hence it is the origin of this species. Control measures were carried out in October, but by then any remaining Ae. atropalpus would have been diapausing in the egg stage. A follow-up survey will be conducted in the spring of 1997 to assess if Ae. atropalpus has been established in the area and the extent of the spread in Italy.

3D structure of kaliotoxin: is residue 34 a key for channel selectivity?

Kaliotoxin (KTX) is a natural peptide blocker of voltage-dependent K+ channels. The 3D structure of a truncated analogue of KTX (Fernandez et al. (1994) Biochemistry 33, 14256-14263) was determined by NMR spectroscopy and showed significant differences from structures established for other related scorpion toxins. A recent publication with the structure of the complete toxin (Aiyar et al. (1995) Neuron 15, 1169-1181) did not confirm these differences. In this communication we report NMR data for KTX at pH 3.0, 5.5 and 7.2 and the 3D structure obtained from data at pH = 5.5. Complete KTX displays a folding similar to that of other toxins with an alpha-helix and a beta-sheet linked by two disulphide bonds. The pKa of His 34 is anomalously low (4.7-5.2 depending on the buffer) owing to its interaction with two Lys residues (including the essential Lys 27), the charged N-terminus and the side chain of Met 29. Charged residues are placed symmetrically with respect to an axis that approximately coincides with one of the principal components of the moment of inertia of the toxin. His 34, which occupies a well-defined position between two conserved Cys, is located on the centre of a layer of charged groups. Positively and negatively charged residues are found at the same position in related toxins. It is suggested that electrostatic effects modulate the distances between positive charges in flexible side chains, contributing to the fine tuning of the selectivity toward different channel subclasses and that the approximate coincidence between the moment of inertia and the charge axis facilitate the approach of the toxin to the channel. The very low pKa of His 34 implies that it will be completely unprotonated at physiological pH.

[Impregnation of uniforms with permethrin as a mean of protection of working personnel exposed to contact with hematophagous arthropods]

Laboratory bioassays were conducted to evaluate the effectiveness of permethrin-impregnated clothing against biting arthropods. Military battle dress uniforms were impregnated at a rate of 0.12-0.15 mg active ingredient (A.I.)/cm2. Gas chromatographic analysis of cloth patches treated showed that over 50% of the chemical remained after 6 cycles of washing. This amount of A.I. (0.06-0.07 mg/cm2) was effective in providing protection against Aedes aegypti and Ixodes ricinus. Mosquitoes and ticks were exposed respectively for 30 sec-3 min and 5-10 min to permethrin-impregnated uniforms: although the knockdown effect diminished with washing, the remaining permethrin provided 100% mortality of the mosquitoes and over 90% mortality of the ticks.

Status of malaria vectors in Italy

About 30 yr after malaria eradication, surveys to assess the presence and abundance of anopheline vectors were carried out in central and southern Italy and in the islands of Sardinia and Sicily from 1992 to 1994. Anopheles labranchiae Falleroni was present in scattered foci in all regions, except for Tuscany, where it breeds almost exclusively in rice fields (Grosseto Province). Most common breeding sites were rivers and streams, followed by ponds and ground pools. The highest adult density was found in Tuscany near rice fields and along the west coast of Calabria. Anophelines in Grosseto were abundant at human bait, with peaks of > 200 landings per human per night and vectorial capacity between 7.3 and 26 for Plasmodium falciparum and between 8.3 and 32.5 for Plasmodium vivax. Anopheles sacharovi Favre, a former malaria vector in Puglia and Sardinia, was not found in these regions. The other vector in southern Italy, Anopheles superpictus Grassi, was found at low densities on the western and eastern coasts of Calabria. All anopheline populations were fully susceptible to deltamethrin, malathion, and DDT but showed reduced susceptibility to permethrin and propoxur. These data are discussed in the light of a possible reintroduction of malaria into Italy.

Esterases A5-B5 in organophosphate-resistant Culex pipiens from Italy

Culex pipiens mosquitos from Lignano city, Udine province, northeast Italy, were found to carry over-produced non-specific esterases A1, A2-B2 and A4-B4 or A5-B5, detected by starch gel electrophoresis, giving multiple resistance to organophosphorus insecticides. In order to differentiate between A4-B4 and A5-B5 esterases, the latter known only from Cyprus whereas the former is widespread in Italy and elsewhere, restriction fragment length polymorphism (RFLP) analysis was performed at the esterase B locus. Both B4 and B5 haplotypes were found. This is the first record of A5-B5 esterase-mediated resistance in continental Europe.

Age-related prevalence of Plasmodium falciparum circumsporozoite antibody in an hyperendemic area of Madagascar, and its relationship with parasite prevalence

An epidemiologic survey on malaria endemicity levels, including entomologic, parasitologic, and immunologic indicators, was carried out in a village of the Madagascar highlands (Analaroa) at the end of the 1990-1991 rainy season. The results indicate that malaria is hyperendemic and Anopheles funestus is the main vector in the area. The prevalence of parasitemia decreased with age from a maximum level of about 60% in children less than five years of age to a minimum of about 16% among those more than 29 years of age. The prevalence of Plasmodium falciparum circumsporozoite antibodies (Ab-Cs) increased with age from a minimum level of about 10% in children less than five years of age to a maximum of 71.7% among those more than 29 years of age. An inverse correlation was observed between P. falciparum prevalence and levels of Ab-Cs and parasite prevalence. The study confirmed that prevalence and Ab-Cs levels are reliable indicators of malaria endemicity in hyperendemic areas. Schoolchildren between five and 14 years of age are considered the most practical and susceptible group for this kind of epidemiologic study.

Occurrence and spread in Italy of Aedes albopictus, with implications for its introduction into other parts of Europe

Aedes albopictus is considered second only to Ae. aegypti in its importance to man as a disease vector of dengue and dengue hemorrhagic fever. The first sighting in 1979 of the vector species in Europe came from Albania; however, it was only when Ae. albopictus was introduced into Italy in 1990, through the importation of used tires, followed by its subsequent spread, that the species was considered as a threat to public health. At the close of 1995, Ae. albopictus infestations have been reported from 10 Italian regions and 19 provinces. The risk for greater distribution of Ae. albopictus in Europe can potentially be projected, based on well-established criteria such as: where the winter monthly mean temperature is 0 degree C, where at least 50 cm of mean annual rainfall occurs, and where the mean summer temperature is approximately 20 degrees C. Those countries where climatic conditions meet such criteria and that may be vulnerable to a potential introduction of Ae. albopictus include Spain, Portugal, Greece, Turkey, France, Albania, and the former Republic of Yugoslavia. The Italian plan of action, established for the surveillance and control of Ae. albopictus, is presented in detail.

History and updating on the spread of Aedes albopictus in Italy

The present distribution in Italy of Aedes albopictus, the Asian mosquito recently introduced, is described. Until now this mosquito species has been established in 8 regions of our country: Liguria, Veneto, Lazio, Lombardia, Emilia-Romagna, Toscana, Piemonte and recently Sardegna. The established populations have been able to overcome the winter season. These populations, certainly imported from temperate areas, have reconfirmed the great adaptation of the species, reaching the high latitude of 46 degrees North of the Padova area in Northern Italy. The origin of the infestation in Veneto region was shown to be strictly related to the importation of used tires and demonstrated at least for one load of tires from USA. The internal trading of tires from Veneto is the source of infestation of the other Italian regions, with the exception of Liguria and Lazio. Since the introduction and the establishment of Ae. albopictus in Italy represent a new problem of public health, a centre for the surveillance and control of this species has been set up at the Department of Parasitology, Istituto Superiore di Sanità, Roma.

The kaliotoxin family enlarged. Purification, characterization, and precursor nucleotide sequence of KTX2 from Androctonus australis venom

Kaliotoxin (KTX) has been originally described as an inhibitor of the intermediate conductance Ca(2+)-activated K+ channel (Crest, M., Jacquet, G., Gola, M., Zerrouk, H., Benslimane, A., Rochat, H., Mansuelle, P., and Martin-Eauclaire, M.-F. (1992) J. Biol. Chem. 267, 1640-1647). However, the radioiodinated 125I-KTX-(1-37) was also able to bind to the dendrotoxin sensitive voltage-dependent K+ channel (Romi, R., Crest, M., Gola, M., Sampieri, F., Jacquet, G., Zerrouk, H., Mansuelle, P., Sorokine, O., Van Dorsselaer, A., Rochat, H., Martin-Eauclaire, M.-F., and Van Rietschoten, J. (1993) J. Biol. Chem. 268, 26302-26309). By following the ability to compete with 125I-KTX-(1-37) for binding to its receptor on rat brain synaptosomes, a new kaliotoxin-like peptide, KTX2, was isolated from Androctonus australis scorpion venom. It is a 37-amino acid residue peptide, and its sequence shares 76% identity with KTX. The differences between the two peptides concern the NH2-terminal region and the residues 31 and 34 located in the region involved in the channel recognition. These differences may explain the 5-fold decrease of the molluscan Ca(2+)-activated K+ channel blockage by KTX2 (kd = 135 nM) as well as of its binding affinity to rat brain synaptosomes (IC50 = 50 pM), compared with KTX. Specific antibodies raised against KTX-(1-37) were not able to recognize KTX2. Using degenerate primers, a 370-base pair cDNA encoding the KTX2 precursor was amplified by polymerase chain reaction from a cDNA library of A. australis venom glands. It encoded a presumed signal peptide of 22 residues followed by the sequence of the mature peptide.

Source and spread of Aedes albopictus in the Veneto region of Italy

Colonies of Aedes albopictus were discovered at the end of the summer of 1991 in the Veneto region of Italy. To locate the source of the infestation, a detailed investigation was carried out among companies dealing in the production of recapped tires. Because most of the tires had been imported from the USA, it was surmised that this could have been one source of the infestation. This hypothesis was confirmed in the summer of 1992 following an inspection of a load of used tires from Atlanta, Georgia, in which Ae. albopictus eggs were found. Despite control measures in 1991, many colonies of Ae. albopictus are now well established in large areas of the region. Adults are active between the months of April and October. They are very susceptible to the most common insecticides.

Plasmodium falciparum circumsporozoite antibody prevalence in Madagascar: a longitudinal study in three different epidemiologic areas

A longitudinal study on the prevalence of Plasmodium falciparum circumsporozoite antibodies (Ab-CS) was carried out in 15 villages of three epidemiologic areas of Madagascar: the highlands, east coast, and the southwest region. A total of 3,967 blood samples were collected from November 1989 to April 1991 from cohorts of resident schoolchildren. The prevalence of Ab-CS in the examined population varied greatly according to the different ecoepidemiologic areas of the country. A correlation analysis was made between Ab-CS and P. falciparum parasite prevalence in the same population. High Ab-CS prevalence rates (25-75%) and levels (optical density = 0.28-0.76) were observed in the villages of the east coast (mesoendemic stable malaria). The Ab-CS prevalence rates varied from 0 to 37% in the highlands and southwest region villages (unstable malaria). The use of Ab-CS prevalence is proposed to be a useful and reliable seroepidemiologic marker of malaria endemicity in those areas of Madagascar in which malaria transmission is high and continues for more than four months a year.