First Record of Culex (Culex) brethesi (Dyar) (Diptera: Culicidae) in Rio Grande do Sul State, Brazil

SCIENTIFIC NOTE

First Record of Culex (Culex) brethesi (Dyar) (Diptera: Culicidae) in Rio Grande do Sul State, Brazil

J da C Cardoso^{I, II}; MB de Paula^I; A Fernandes^I; E dos Santos^II; MAB de Almeida^II; DF da Fonseca^II; MAM Sallum^I

^IDepto de Epidemiologia, Faculdade de Saúde Pública, USP, São Paulo, SP, Brasil

^IIDivisão de Vigilância Ambiental em Saúde, Centro Estadual de Vigilância em Saúde, Secretaria da Saúde do Estado do RS, Porto Alegre, RS, Brasil

^{Correspondence}

ABSTRACT

This is the first record of Culex (Culex) brethesi (Dyar) in Rio Grande do Sul state, Brazil. The species was identified from specimens collected in a sand bar vegetation with the aid of a Nasci's trap, during an expedition for surveillance of the West Nile Virus in July of 2006, in the city of Mostardas, Rio Grande do Sul, Brazil.

Keywords: Entomological surveillance, vector, Arbovirus

Mosquitoes are among the most important vectors of the West Nile Virus (WNV), an arbovirus of the genus Flavivirus (Flaviviridae), which infects equines and urban and wild birds and may lead to death. In humans, this virus causes fever, at times progressing to acute meningitis, encephalitis, and death. The WNV was detected in Africa, Asia, Europe (Natal & Ueno 2004), and in the United States (Petersen & Roehrig 2001). In 1999 the WNV has spread throughout North and Central America, and was first isolated in South America in 2006, in Buenos Aires, Argentina (Morales et al 2006). In the United States, between 1999 and 2008, tests performed in mosquitoes detected the WNV in 64 Culicidae species, of which the majority belonged to the genera Culex and Aedes (CDC 2009).

In Brazil, 156 species of the genus Culex are registered, grouped in nine subgenera (WRBU 2009). The subgenus Culex is one of the most important in the Neotropical region from an epidemiological point of view (Forattini 2002).

Due to the potentiality to be introduced in Brazil, the WNV surveillance includes entomological studies aiming to identify potential vector species, know their population dynamics, and detect and monitor viral activity in potential hosts. To achieve this, actions focused on adult forms of Culex spp. and Aedes spp. are recommended, both in areas of high risk of transmission (zoos, hunting reserves, feeding territories or migratory bird refuges) and places of notification of possible or confirmed WNV cases in birds, humans and other mammals (OPAS 2002). Between July 24^th and 28^th, 2006, as part of the WNV Surveillance Program routine, the Centro Estadual de Vigilância em Saúde, an organ of the Secretaria da Saúde do Rio Grande do Sul organized an expedition to the Parque Nacional Lagoa do Peixe (PNLP), the largest migratory bird refuge in this state. The park covers the cities of Tavares (80%), Mostardas (17%) and São José do Norte (3%), and is located between the Lagoa dos Patos and the Atlantic Ocean, on the central section of the Coastal Plains of the state of Rio Grande do Sul (Fig 1). According to its management plan, the PNLP covers an area of 344 km² and is 62 km long and 6 km wide on average. Mean annual temperature varies from 18°C and 20°C and mean annual rainfall reaches 1,186 mm. Except for a long belt of coastal dunes, the topography is flat, and the soil is basically formed by marine quartz sands (Loebmann & Vieira 2005).

Mosquitoes were collected in sand bar vegetation on the road (31°06'42" S; 50°51'59" W) that connects the city of Mostardas with the coast. A total of two 15-min manual aspirations were performed (from 09:30h to 09:45h and from 10:15h to 10:30h), using Nasci's traps (Nasci 1981). The mosquitoes collected were stored in entomological boxes and sent to the Laboratório de Entomologia em Saúde Pública - Universidade de São Paulo, to identify the species. A total of four Culex (Culex) brethesi (Dyar) specimens were identified, based on characters of the male genitalia.

Culex brethesi was described from the genitals of a male collected in San Isidro, in the province of Buenos Aires, Argentina. Its geographic distribution is not well known. While Guimarães (1997) points to the occurrence of Cx. brethesi in Argentina and questions its presence in Brazil, the Smithsonian Institution online catalogue of mosquitoes records the presence of this species only in Argentina and Uruguay (WRBU 2009). In Brazil, Taipe-Lagos & Natal (2003), in a study of mosquito ecology in the Parque Ecológico Tietê located in the outskirt of the city of São Paulo, identified four Cx. brethesi specimens. However, the authors did not specify whether they were male or female. Rossi (2006) used material originated from collections made in Buenos Aires and from the Museu de la Plata archives to re-describe the male, female, pupa and 4^th instar larva. In addition, information about taxonomy and geographic distribution of the species was updated. According to Rossi (2006), Cx. brethesi occurs in the Argentinean provinces of Buenos Aires, Cordoba, Mendoza, Misiones, Santa Fe, Santiago del Estero, Entre Rios, Corrientes and Misiones. The author suggests that other records of this species could have resulted from mistaken identifications, not based on male genital structures.

In this study Cx. brethesi is recorded for the first time in Rio Grande do Sul state, making clear its occurrence in Brazil. The specimens were identified based on characteristics of the male genitalia (Fig 2), and incorporated into the Coleção Entomológica of the Faculdade de Saúde Pública da USP (FSP-USP).

Even though this species has not been associated, until now, with the transmission of pathogens that cause diseases in humans this finding shows the importance of detailed collection activities of the Culicidae fauna as an entomological surveillance strategy.

Acknowledgments

We acknowledge the Parque Nacional Lagoa do Peixe management for permitting the collections. MAMS is financially supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP (Grant 05/53973-0), and Conselho Nacional de Desenvolvimento Técnico e Científico (CNPq BPP 300351/2008-9 to MAMS).

Received 06 August 2009 and accepted 28 January 2010

Edited by Neusa Hamada - INPA

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Publication Dates

• Publication in this collection
  14 Mar 2011
• Date of issue
  Feb 2011

History

• Received
  06 Aug 2009
• Accepted
  28 Jan 2010