Influence of biotic and abiotic factors on the distribution and abundance of Culicoides imicola and the Obsoletus Complex in Italy

Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise, via Campo Boario, 64100, Teramo, Italy.
Veterinary Parasitology (Impact Factor: 2.46). 12/2007; 150(4):333-44. DOI: 10.1016/j.vetpar.2007.09.021
Source: PubMed


Culicoides imicola Kieffer (Culicoides, Diptera: Ceratopogonidae) is the principal vector of bluetongue virus (BTV) to ruminant livestock in southern Europe. The secondary potential vectors are Culicoides obsoletus (Meigen) and Culicoides scoticus Downes and Kettle of the Obsoletus Complex, Culicoides pulicaris (Linnaeus) of the Pulicaris Complex and Culicoides dewulfi Goetghebuer of the subgenus Avaritia Fox. Between 2000 and 2004 >38,000 light-trap collections were made for Culicoides across Italy including the islands of Sardinia and Sicily. Mapping of the 100 largest collections of C. imicola and of the Obsoletus Complex showed them to be disjunct overlapping in only 2% of the 200 municipalities selected. For each municipality the average values were calculated for minimum temperature, aridity index, altitude, terrain slope, normalised difference vegetation index (NDVI) and percentage forest cover. A factor analysis identified two principal factors ('biotic' and 'abiotic') and explained 84% of the total variability; a discriminant analysis classified correctly 87.5% of the observations. The results indicate adult populations of C. imicola to occur in more sparsely vegetated habitats that are exposed to full sunlight, whereas species of the Obsoletus Complex favour a more shaded habitat, with increased green leaf density. Heliophily and umbrophily, by shortening or lengthening the respective adult life cycles of these two vectors, will likely impact on the ability of each to transmit BTV and is discussed in the light of the current outbreak of BTV across the Mediterranean Basin.

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    • "Breeding of most Culicoides species occurs in habitats with high water availability (Conte et al. 2007). On the western slope of the Andes water availability is predicted to peak at middle elevations as a result of increased precipitation relative to low elevations and persistence of water runoff from high elevations (McCain 2007). "
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    ABSTRACT: The environment shapes host-parasite interactions, but how environmental variation affects the diversity and composition of parasite-defense genes of hosts is unresolved. In vertebrates, the highly variable major histocompatibility complex (MHC) gene family plays an essential role in the adaptive immune system by recognizing pathogen infection and initiating the cellular immune response. Investigating MHC-parasite associations across heterogeneous landscapes may elucidate the role of spatially fluctuating selection in the maintenance of high levels of genetic variation at the MHC. We studied patterns of association between an avian haemosporidian blood parasite and the MHC of rufous-collared sparrows (Zonotrichia capensis) that inhabit environments with widely varying haemosporidian infection prevalence in the Peruvian Andes. MHC diversity peaked in populations with high infection prevalence, although intra-individual MHC diversity was not associated with infection status. MHC nucleotide and protein sequences associated with infection absence tended to be rare, consistent with negative frequency-dependent selection. We found an MHC variant associated with a ~26% decrease in infection probability at middle elevations (1501-3100 m) where prevalence was highest. Several other variants were associated with a significant increase in infection probability in low haemosporidian prevalence environments, which can be interpreted as susceptibility or quantitative resistance. Our study highlights important challenges in understanding MHC evolution in natural systems, but may point to a role of negative frequency-dependent selection and fluctuating spatial selection in the evolution of Z. capensis MHC.
    Ecology and Evolution 03/2015; 5(5):n/a-n/a. DOI:10.1002/ece3.1391 · 2.32 Impact Factor
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    • "As previously shown in South Africa (Venter and Meiswinkel, 1994), C. imicola appeared more abundant at low altitude although it was found up to 1200 m in Reunion Island. The major factors explaining Culicoides distribution are temperature, humidity, rainfall (Baylis et al., 1998, 1999, 2001; Calvete et al., 2008; Conte et al., 2003; Purse et al., 2004; Tatem et al., 2003; Wittmann et al., 2001), wind (Baylis et al., 1998) as well as altitude (Baylis et al., 2001; Conte et al., 2003), soil type and moisture (Conte et al., 2007), vegetation indices or land use (Conte et al., 2007), and presence of hosts. Due to its mountainous landscape, Reunion Island exhibits a pronounced temperature gradient. "
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    ABSTRACT: This study establishes the first faunistic inventory of livestock associated Culicoides (Diptera: Ceratopogonidae) species of Reunion Island (Indian Ocean), where bluetongue and epizootic hemorrhagic disease are regularly recorded. Single night-catches were performed at 41 sites using light suction traps at altitudes ranging from 0 to 1525 m, from March to April 2005. Five species were recorded: Culicoides imicola, Culicoides bolitinos, Culicoides enderleini, Culicoides grahamii, and Culicoides kibatiensis, among which at least the first three species are known to be involved in virus transmission to ruminants and equids. This is the first record of C. bolitinos, C. kibatiensis, and C. enderleini on the island. C. imicola was the most abundant species along the sea coast. C. bolitinos was more abundant inland and on two sites on the east coast. C. kibatiensis and C. grahamii were less abundant than the other three species and limited to two foci.Spatial distribution analysis of the different species showed that C. bolitinos, C. enderleini and C. imicola were collected at low altitudes, while the other two species were found at higher altitude. A morphological identification key for adult females and males is given, as well as cytochrome oxydase subunit I sequences. Phylogenetic reconstructions showed a clear divergence between C. bolitinos from Reunion Island and mainland Africa. This monograph will help to identify the Culicoides species in the poorly known entomological fauna of the south-western Indian Ocean region.
    Acta Tropica 11/2014; 142. DOI:10.1016/j.actatropica.2014.10.018 · 2.27 Impact Factor
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    • "The above examples indicate that the species communities of biting midges change between neighboring countries and even from one farm to another in the same area, though at first glance, the farms seem alike. The local species community of biting midges is without doubt dependent on a vast number of biotic and abiotic factors ranging from the presence of different host species (Lassen et al. 2012a), surrounding landscape elements such as woodlands and wetlands (Conte et al. 2007; Takken et al. 2008; Thompson et al. 2013), or the farming practice, e.g., conventional versus organic farming (Mehlhorn et al. 2007). "
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    ABSTRACT: This study presents descriptive statistics and community analysis of adult biting midges trapped at 16 livestock farms by means of light traps on Zealand and Lolland-Falster, Denmark. A total of 9,047 male and female Culicoides divided into 24 species, were caught. Biotic and abiotic factors ranging from presence of different host species (cattle or sheep/goats), presence of small woody areas or wetlands in the surrounding landscape, and agricultural practice (organic or conventional) were included in the community analysis. Only differences in the Culicoides communities between conventional and organic practices were tested significantly different. Total numbers of Culicoides individuals were higher on the organic farms than on the conventional farms. The larger loads of biting midges on the organic farms may be due to free-ranging animals that attracted the midges on pastures and carried them to the stable environment (the cattle of the conventional farms were held inside the stables). Presence of deciduous trees within 500 m of the farms resulted in higher numbers of Culicoides obsoletus s.s., while presence of wetlands increased the numbers of Culicoides punctatus and Culicoides pulicaris. Furthermore, Culicoides riethi and Culicoides puncticollis (subgenus Monoculicoides) were recorded in high numbers on individual farms. C. puncticollis was found for the first time in Denmark and so far only recorded from Zealand.
    Parasitology Research 10/2014; 113(12). DOI:10.1007/s00436-014-4142-z · 2.10 Impact Factor
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