Surveillance of the chikungunya vector Aedes albopictus (Skuse) in Emilia-Romagna (northern Italy): organizational and technical aspects of a large scale monitoring systemArchived
The chikungunya virus outbreak that occurred in 2007 in northern Italy (Emilia-Romagna region) prompted the development of a large scale monitoring system of the population density of Aedes albopictus (Skuse, 1894), comparable at the provincial and municipal levels. In 2007, egg density data presented an aggregated distribution (VMR >1) and Taylor's power law was applied to calculate the minimum number of ovitraps needed to obtain the prefixed precision levels: D=0.2 in the areas where the chikungunya epidemic occurred and D=0.3 in all the other urban areas >600 ha.
Carrieri M1, Albieri A1, Angelini P2, Baldacchini F2, Venturelli C3, Zeo SM3, Bellini R1.1 Medical and Veterinary Entomology, Centro Agricoltura Ambiente “G. Nicoli”, Crevalcore (BO), Italy 2 Emilia-Romagna Region Public Health Service, Bologna, Italy3 Public Health Department, Cesena (FC), ItalyJournal of Vector Ecology 2011 Jun;36(1):108-16. doi: 10.1111/j.1948-7134.2011.00147.x.
The chikungunya virus outbreak that occurred in 2007 in northern Italy (Emilia-Romagna region) prompted the development of a large scale monitoring system of the population density of Aedes albopictus (Skuse, 1894), comparable at the provincial and municipal levels. In 2007, egg density data presented an aggregated distribution (VMR >1) and Taylor's power law was applied to calculate the minimum number of ovitraps needed to obtain the prefixed precision levels: D=0.2 in the areas where the chikungunya epidemic occurred and D=0.3 in all the other urban areas >600 ha. The estimated minimum ovitrap number was then used to set up a monitoring network at the regional scale in season 2008 (May-October). In 242 municipalities 2,741 ovitraps were activated and the 2008 sampled data showed a similar aggregated distribution as in 2007. The adequacy of the monitoring design was evaluated by recalculating the Taylor's coefficients and the minimum ovitrap number for each urban area >600 ha using the 2008 egg density data. The comparison between the two estimates showed that the minimum ovitrap number calculated in 2007 was underestimated by 2.7% in weeks 22-41 but was overestimated by 29.4% if referring to the period of highest population density (weeks 27-37). The low cost of the proposed monitoring system, based on the use of fortnightly checked ovitraps, could make it economically sustainable even in a non-epidemic season.
VBORNET comment, 30/9/2011: In this paper, Carrieri et al. provide well-supported data underlining the importance of using ovitraps to monitor Aedes albopictus even in low density areas. Ovitraps are already being used for several years for the monitoring of Aedes (Stegomyia) species like Ae. albopictus and Ae. aegypti and their use has become standard. However, the relationships between egg monitoring and adult densities remain unclear. Here the authors statistically test their data which allows them to adapt the sampling scheme and control measurements according to the specific site characteristics and regarding species abundances. This is a unique approach achievable at low cost and well-designed to estimate the infestation level in large urban areas (exceeding 600 ha) even in non-epidemic season. Moreover, one of the main advantages is the continuous sets of data on mosquito populations which can serve as a basis for more directed monitoring and control strategies. This paper correctly promotes the further use of ovitraps for studies on invasive Aedes species as a low cost and efficient surveillance method. Furthermore these long-term data can be implemented in prevention and control strategies, can be used in (GIS) applications which have been done by the authors for this region, and is an added value to the continuous invasive mosquito problematic in Europe.