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Open Access Research

Molecular xenomonitoring of Dirofilaria immitis and Dirofilaria repens in mosquitoes from north-eastern Italy by real-time PCR coupled with melting curve analysis

Maria Stefania Latrofa1, Fabrizio Montarsi2, Silvia Ciocchetta2, Giada Annoscia1, Filipe Dantas-Torres13, Silvia Ravagnan2, Gioia Capelli2 and Domenico Otranto1*

Author Affiliations

1 Dipartimento di Sanità Pubblica e Zootecnia, Università degli Studi di Bari, Strada Provinciale per Casamassima km 3, 70010, Valenzano, Bari, Italy

2 Istituto Zooprofilattico Sperimentale delle Venezie, Laboratory of Parasitology, Viale dell’Università 10, Legnaro, 35020, Italy

3 Departamento de Imunologia, Centro de Pesquisas Aggeu Magalhães (Fiocruz-PE), 50670-420, Recife, Pernambuco, Brazil

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Parasites & Vectors 2012, 5:76  doi:10.1186/1756-3305-5-76

Published: 20 April 2012

Abstract

Background

Dirofilaria immitis and Dirofilaria repens are transmitted by bloodsucking culicid mosquitoes belonging to Culex, Aedes, Ochlerotatus, Anopheles and Mansonia genera.

The detection of filarioids in mosquitoes for assessing distribution of vectors and/or of pathogens in a given area (also known as “xenomonitoring”), when based on individual dissection of wild-caught female mosquitoes is time consuming and hardly applicable in large epidemiological surveys.

Our study aimed to evaluate the recently developed duplex real-time PCR for screening large number of culicids and to assess their positivity for D. immitis and D. repens in an area where both species are endemic.

Methods

A duplex real-time PCR was used to detect and differentiate D. immitis and D. repens in mosquitoes collected in six provinces of the Veneto region using 43 carbon dioxide-baited traps under the frame of an entomological surveillance program to monitor the vectors of West Nile disease. From early May till October 2010, unfed female mosquitoes (n = 40,892) were captured in 20 selected sites.

Results

Mosquitoes identified as Culex pipiens, Ochlerotatus caspius, Aedes vexans and Culex modestus were grouped into 995 pools according to species, day and site of collection (from minimum of 1 to maximum of 57). Out of 955 pools, 23 (2.41 %) scored positive for Dirofilaria spp. of which, 21 (2.2 %) for D. immitis and two (0.21 %) for D. repens. An overall Estimated Rate of Infection (ERI) of 0.06 % was recorded, being higher in Och. caspius and Ae. vexans (i.e., 0.18 % and 0.14 %, respectively). At least one mosquito pool was positive for Dirofilaria spp. in each province with the highest ERI recorded in Vicenza and Padova provinces (i.e., 0.42% and 0.16 %, respectively). Mosquitoes collected in all provinces were positive for D. immitis whereas, only two (i.e., Padova and Rovigo) provinces scored positive for D. repens. All mosquito species, except for Cx. modestus, were positive for D. immitis, whereas D. repens was only found in Cx. pipiens.

Conclusions

The results suggest that both Dirofilaria species are endemic and may occur in sympatry in the examined area. The molecular approach herein used represents a powerful tool for surveillance programs of D. immitis and D. repens in the culicid vectors towards a better understanding of the epidemiology of the infections they cause and their seasonal transmission patterns.

Keywords:
Dirofilaria immitis; Dirofilaria repens; Real-time PCR; Mosquitoes; Vector; Surveillance