Atti Accademia Nazionale Italiana di Entomologia Anno LXII, 2014: 159-163 THE IMPORTANCE AND SIGNIFICANCE OF ENTOMOLOGICAL MONITORING FOR NEW AND OLD PATHOGENS TRANSMITTED BY CULICIDAE GIOIA CAPELLI (*) - SIMONE MARTINI (**) - SARA CARLIN (*) - STEFANIA CAZZIN (*) SILVIA CIOCCHETTA (***) - PAOLO MULATTI (*) - MATTEO MAZZUCATO (*) -MANLIO PALEI (****) FRANCESCA RUSSO (*****) - SILVIA RAVAGNAN (*) - STEFANO MARANGON (*) - FABRIZIO MONTARSI (*) (*) Istituto Zooprofilattico Sperimentale delle Venezie, Viale dell’Università, 10; 35020 Legnaro (Padua), Italy; e-mail: [email protected] (**) Entostudiosnc, Brugine (Padua), Italy (***) Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia (****) Friuli Venezia Giulia region, Udine , Italy (*****) Veneto Region, Venice, Italy Lettura tenuta durante il Seminario “Arthropod vectors of diseases in humans and domestic animals”, in onore dell’Accademico Mario Coluzzi. Seduta pubblica dell’Accademia - Roma, 3 ottobre 2014. The importance and significance of entomological monitoring for new and old pathogens transmitted by Culicidae Mosquito-borne pathogens (MBPs) include viruses, protozoa and helminths affecting animals and humans worldwide. When a vector is established in an area there is a real and predictable risk of introduction of new MBPs or expansion of old ones, due to the global movement of goods, animals and humans. The global trade also enhanced the likelihood to import alien species, which pose new threats for the transmission of local and exotic MBPs. The surveillance of MBPs includes the entomological monitoring, which has different aims and strategies according to the target mosquito and pathogen. Here we report the main results achieved in five years of entomological monitoring in north-eastern Italy for endemic and at risk of introduction MBPs. In particular the significance of long and short term studies is commented, also reporting examples of other researchers. Our conclusion is that the current situation of MBPs in northern Italy suggests entomological monitoring cannot be abandoned in the next future, especially in Veneto region. Efforts need to be done in order to maximize the efficacy of the monitoring systems and at the same time minimize the costs for the community. In this respect studies on the cost/benefit of entomological monitoring systems are welcome. KEY WORDS: entomological surveillance, mosquito-borne pathogens, Culex pipiens, Aedes albopictus. BACKGROUND Mosquito-borne pathogens (MBPs) include viruses, protozoa and helminths affecting animals and humans worldwide (ENGLER et al., 2013; OTRANTO et al., 2013). In north-eastern Italy some MBPs are endemic, with different spatial and temporal distribution, such as Dirofilaria immitis and D.repens (L ATROFA et al., 2012; CAPELLI et al., 2013a), Setaria labiatopapillosa (PIETROBELLI et al., 1995; CANCRINI et al., 1997), West Nile (WNV) and Usutu virus (USUV) (CAPELLI et al., 2013b), protozoa circulating among birds (Plasmodium, filariae) and in the past, also human malaria (MAJORI, 2012; ROMI et al., 2012).When a vector is established in an area there is a real and predictable risk of introduction of new MBPs or expansion of old ones, due to the global movement of goods, animals and humans. The recent outbreak of chikungunya virus in Emilia-Romagna (ANGELINI et al., 2007), the emergence of WNV in northern Italy (BUSANI et al., 2011) and the expansion of D. immitis in southern regions (OTRANTO et al., 2009) – Pubblicato aprile 2015 are paradigmatic examples of such occurrences. The global trade also enhanced the likelihood to import alien species, which pose new threats for the transmission of local and exotic MBPs (M EDLOCK et al., 2012).The surveillance of MBPs in based on passive and active monitoring of humans and susceptible animals (MULATTI et al., 2013) coupled with the entomological monitoring, which has different aims and strategies according to the target mosquito and pathogen. In general the entomological monitoring has the following main aims: (i) to define the mosquito species composition, their relative density and seasonal dynamics; (ii) to early detect the re-activation of endemic pathogens; to assess the mosquito infection rate and therefore quantify the risk of transmission to vertebrates; (iii) to detect new circulating pathogens; (iv) to detect new mosquito species. The reachability of these aims are affected by the spatial and temporal intensity of the monitoring, the skills of the people involved and, last but not least, the budget availability. – 160 – ENDEMIC PATHOGENS PND CULEX PIPIENS L. The north-eastern part of Italy (Veneto and Friuli Venezia Giulia regions) seems to be particularly suitable for the mosquito survival, likely due to its climate, landscape and abundance of wild/domestic animals. After the emergence of WNV in 2008 (MACINI et al., 2008; BUSANI et al., 2011), several entomological studies were implemented, including long term monitoring systems and short term studies to answer specific questions. For long term monitoring, a range of 24-66 CDCCO2 traps were activated weekly or fortnightly from May to October 2009-2013. The mosquitoes were screened by RT-PCR for Flaviviridae (RAVAGNAN et al., 2011). More than 700,000 mosquitoes were collected, being Cx.pipiens the most abundant (80%) followed by Ochlerotatus caspius and Aedes vexans. Cx. pipiens was the only vector of WNV and USUV in this area. From 2010 to 2013, the WNV positive samples were characterized by partial sequencing of NS5 and NS3 genes.The phylogenetic analyses showed the occurrence of WNV lineage 1 and 2, and of two different strains of WNV-1 that have been circulating with different spatial and temporal patterns.This highlights that new viral introductions have occurred in few years and also indicates the capability of these viruses to become endemic and to rapidly evolve and emerge in different sites (CAPELLI et al., 2013b;RAVAGNAN et al., 2014). Mapping, modeling and spatial analyses were done using the entomological data to identify correlations with climate, landscape, animal and human infections (M ULATTI et al., 2014). The results showed for the first time that the contribution of density-dependence in regulating vector population growth was greater than any other environmental factor on its own. Overall the most significant predictors of Cx.pipiens dynamics included length of daylight, population density and temperature in the 15 days prior to sampling. Precipitation, number of rainy days and humidity had limited importance. Also linear models detected significant relationships between WNV in humans and mosquitoes. Spatial analysis detected clusters of WNV occurrences for all the hosts, identifying an area where to focus surveillance and promptly detect WNV reactivation (MULATTI et al., 2013). Beside annual monitoring, short term studies were organized. In one site, captures with CDC and gravid traps were done every 2hrs for 24hrs all over the season. The “dial activity” showed that Cx.pipiens changed its host searching activity according to the season and highlighted the period of the day at major risk of Cx. pipiens biting (MONTARSI et al., 2015). This may help to target personal protection against mosquitoes based on the higher risk of human bite and WNV transmission. In other three sites pre- and post-disinfestation captures were done (CARLIN et al., 2014).In only one site a significant mosquito reduction (75%) was achieved. The success of the control measures in reducing Cx.pipiens density varied according to the methods used, calling for the need of harmonic guidelines for disinfestation procedures. This may help to choose the most effective method for mosquito control in case of emergency. The host preference of Cx.pipiens was assessed by PCR blood meal analysis of fed females and human landing captures (MONTARSI et al., 2014). Cx.pipiens fed preferentially on birds (76%), mainly blackbird, sparrow, magpie and collared dove, indicating possible bird targets for a better WNV surveillance. The low biting rates of humans and the absence of detection of human blood into mosquitoes in the sites examined confirm that Cx. pipiens is scarcely attracted by humans. The results of this study could explain the relative low incidence of WNV clinical cases in horses and humans compared to other infected areas of eastern Europe and USA. The data provided are also of importance for WNV transmission risk models in the area affected. PATHOGENS AT RISK (SKUSE) OF INTRODUCTION AND AEDES ALBOPICTUS In Italy every year a variable number of human imported dengue and chikungunya cases are reported (GOBBI et al., 2012). If these cases occur in summer in an area infested by the tiger mosquito the risk of transmission is real and increases according to the density of the mosquitoes and people. Consequently, the knowledge of the degree of the infestation in an area is pivotal to promptly intervene with the disinfestation actions according to the National Program of Surveillance. The best examples of a large scale entomological monitoring is the one set up in the Emilia Romagna region, where urban areas are constantly monitored by more than 2,700 ovitraps (CARRIERI et al., 2011). Using the series of historical data, the mean number of eggs laid in ovitraps were compared to different estimates of adult mosquito abundance, human landing collection and number of bites declared by citizens. It was then possible to calculate a disease – 161 – risk threshold in terms of number of eggs per ovitrap above which an arbovirus epidemic may occur (CARRIERI et al., 2012). DETECTION OF NEW SPECIES In Veneto region the entomological monitoring for the tiger mosquito allowed the detection of Aedes koreicus (Edwards), a new invasive mosquito species (CAPELLI et al., 2011), potential vector of arboviruses and filariae. The biology and ecology of this mosquito need to be studied (M ONTARSI et al., 2013), such as the host preference (CAZZIN et al., 2014) and the vector competence for helminthes and viruses. Invasive Aedes species may pose new threats for animal and human health (MEDLOCK et al., 2012). For more details see MONTARSI et al. in this issue. THE RETROSPECTIVE STUDIES When a vector monitoring system is set up for years a consistent bank of samples is usually stored. A sub-sample of the mosquitoes collected in previous years was screened for Bunyaviridae. Tahyna virus was isolated from Ochlerota tus caspius (Pallas) in Veneto and Emilia Romagna Regions and Batai virus from Anopheles maculipennis s.l. (Meigen) in Emilia Romagna only (CALZOLARI et al., 2010, CAPELLI et al., 2014). These findings help to enhance the preparedness of the Health System to face the possible emergence of these viruses. Using the DNA extracted from mosquitoes in 2010 it was also possible to map the distribution of D.immitis and D.repens in mosquitoes in Veneto, giving new insights on the risk of transmission for animals and humans (LATROFA et al., 2012). Another interesting example of the usefulness of retrospective studies is the evidence of the Schmallenberg virus (SBV) into Culicoides samples stored in 2012 in Italy. In this case, it was possible to demonstrate that SBV had circulated in at least three Italian provinces since early September 2011, nearly 5 months prior the first detected case in 2012 (GOFFREDO et al.,2013). CONCLUSIONS The current status of MBPs in northern Italy suggests that entomological monitoring cannot be abandoned in the next future. In particular, Veneto region is the only area of Italy where WNV has been circulating continuously in animals, humans and vectors since its emergence in 2008. Efforts need to be done in order to maximize the efficacy of the monitoring systems and at the same time minimize the costs for the community. In this respect studies on the cost/benefit of entomological monitoring systems are welcome. For pathogens at risk of introduction a recent review of ROGERS et al. (2014) concluded that “The threat of dengue to Europe at present is considered to be low but sufficiently uncertain to warrant monitoring in those areas of greatest predicted environmental suitability, especially in northern Italy and parts of Austria, Slovenia and Croatia, Bosnia and Herzegovina, Serbia and Montenegro, Albania, Greece, south-eastern France, Germany and Switzerland, and in smaller regions elsewhere”. The paradigmatic example of chikungunya outbreak in Emilia Romagna region is a lesson that we must not forget. RIASSUNTO Fra gli agenti patogeni trasmessi dalle zanzare vi sono virus, protozoi ed elminti che possono infettare gli animali e l’uomo in tutto il mondo. Se una specie di zanzara vettrice è ben stabilita in un territorio vi è un alto rischio di introduzione di nuovi patogeni o di espansione di quelli già presenti, a causa del movimento globale delle merci, degli animali e degli esseri umani. Il commercio globale ha aumentato poi il rischio di importare specie aliene di zanzare insieme agli agenti infettivi da loro trasmessi sia locali che esotici. La sorveglianza del fenomeno si basa sul monitoraggio entomologico, che ha diversi obiettivi e strategie in base alla specie di zanzara target e al tipo di patogeno trasmesso. Nella rassegna sono riportatii principali risultati conseguiti in cinque anni di monitoraggio entomologico in aree endemiche dell’Italia nord-orientale a rischio di introduzione di nuovi patogeni trasmessi dalle zanzare. 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