Anopheles Annulipes Research Articles

Mosquito and Arbovirus Surveillance at Bradshaw Field Training Area, Northern Territory, Australia.

Mosquito surveillance and mosquito-borne arbovirus detections in the area of Bradshaw Field Training Area (BFTA) in Northern Territory, Australia, have not been previously documented. A survey to record the mosquito species within BFTA and determine if arboviruses are present in them was conducted in April 2013. A total of 8,530 mosquitoes were collected, using carbon dioxide-baited encephalitis virus surveillance traps, and the predominant species were Aedes normanensis, which was 74.2% of the mosquitoes collected, and Anopheles annulipes (11.1%), An. amictus (2.9%), and An. meraukensis (2.4%). The mean number of mosquitoes collected was 120.1 ± 13.7 per trap in the 71 traps placed. This study has shown mosquito abundance in the eastern area of BFTA during 2 wk of April 2013 was of high density, and therefore a heightened risk of arbovirus transmission. Reverse transcriptase-polymerase chain reaction and virus isolation identified a single Barmah Forest virus strain from a pool of Ae. normanensis, a positive rate of 1/174 (0.57%). This study has provided the 1st survey of mosquitoes and potential mosquito-borne virus transmission in BFTA.

Anopheles annulipes

This datasheet on Anopheles annulipes covers Identity, Distribution, Hosts/Species Affected.

Observations of an unexpected abundance of estuarine mosquitoes associated with an urban freshwater wetland

ABSTRACT Urban freshwater wetlands have been identified as a potential source of mosquitoes of pest and public health concern in Australia. Mosquitoes most commonly associated with these habitats include Anopheles annulipes, Culex annulirostris, Culex quinquefasciatus, Coquillettidia linealis and Mansonia uniformis. However, adaptive management of freshwater wetlands for wildlife conservation or vegetation management can alter the local environmental conditions and may provide opportunities for other mosquito species to exploit these habitats. A series of small wetlands at Sydney Olympic Park, NSW, were drained in spring 2016 and allowed to refill via rainfall to improve conditions for the endangered green and golden bell frog Litoria aurea. Below-average rainfall was experienced that summer and the wetlands did not fully refill until early autumn. Surprisingly, immature stages of the estuarine mosquito, Aedes vigilax, were observed in the freshwater wetlands in exceptional abundances during this period. Adjacent to these freshwater wetlands there are extensive saltmarsh and mangrove habitats where highly abundant populations of Ae. vigilax are common. Observations of use of freshwater habitats by this estuarine mosquito have implications for urban freshwater wetland management and rehabilitation strategies, which currently do not consider the potential pest and public health issues associated with estuarine mosquitoes.

Seasonal activity, vector relationships and genetic analysis of mosquito-borne Stratford virus.

There are many gaps to be filled in our understanding of mosquito-borne viruses, their relationships with vectors and reservoir hosts, and the environmental drivers of seasonal activity. Stratford virus (STRV) belongs to the genus Flavivirus and has been isolated from mosquitoes and infected humans in Australia but little is known of its vector and reservoir host associations. A total of 43 isolates of STRV from mosquitoes collected in New South Wales between 1995 and 2013 was examined to determine the genetic diversity between virus isolates and their relationship with mosquito species. The virus was isolated from six mosquito species; Aedes aculeatus, Aedes alternans, Aedes notoscriptus, Aedes procax, Aedes vigilax, and Anopheles annulipes. While there were distinct differences in temporal and spatial activity of STRV, with peaks of activity in 2006, 2010 and 2013, a sequence homology of 95.9%–98.4% was found between isolates and the 1961 STRV prototype with 96.2%–100% identified among isolates. Temporal differences but no apparent nucleotide divergence by mosquito species or geographic location was evident. The result suggests the virus is geographically widespread in NSW (albeit only from coastal regions) and increased local STRV activity is likely to be driven by reservoir host factors and local environmental conditions influencing vector abundance. While STRV may not currently be associated with major outbreaks of human disease, with the potential for urbanisation and climate change to increase mosquito-borne disease risks, and the possibility of genomic changes which could produce pathogenic strains, understanding the drivers of STRV activity may assist the development of strategic response to public health risks posed by zoonotic flaviviruses in Australia.

Genetic characterization of K13965, a strain of Oak Vale virus from Western Australia

K13965, an uncharacterized virus, was isolated in 1993 from Anopheles annulipes mosquitoes collected in the Kimberley region of northern Western Australia. Here, we report its genomic sequence, identify it as a rhabdovirus, and characterize its phylogenetic relationships. The genome comprises a P′ (C) and SH protein similar to the recently characterized Tupaia and Durham viruses, and shows overlap between G and L genes. Comparison of K13965 genome sequence to other rhabdoviruses identified K13965 as a strain of the unclassified Australian Oak Vale rhabdovirus, whose complete genome sequence we also determined. Phylogenetic analysis of N and L sequences indicated genetic relationship to a recently proposed Sandjima virus clade, although the Oak Vale virus sequences form a branch separate from the African members of that group.

Mosquito (Diptera: Culicidae) and Rainfall Associations with Arbovirus Disease in Eastern Victoria

Associations between mosquito abundance and Ross River virus (RRV) and Barmah Forest virus (BFV) disease are demonstrated for the Gippsland Lakes region of eastern Victoria, Australia. Significant correlations were obtained between RRV and BFV disease notifications and mosquito counts after lag times ranging from 2–4 months for the dominant mosquito species Aedes camptorhynchus, and 0–3 months for the less abundant mosquitoes Anopheles annulipes, Culex australicus and Culex globocoxitus. Correlations between RRV and BFV disease notifications and rainfall were significant after lag times of 3–4 months. Monthly abundance of Ae. camptorhynchus was significantly higher during above-average years of RRV notifications, with higher mosquito abundance during November to January. Together, these results clarify some important timelines between rainfall, mosquito abundance and increased arbovirus activity in eastern Victoria.

Salinity as a driver of aquatic invertebrate colonisation behaviour and distribution in the wheatbelt of Western Australia

To understand how environmental change will modify community assembly and the distribution of organisms it is valuable to understand mechanisms that drive the occurrence of organisms across the landscape. Salinisation of agricultural land in southwest Western Australia, as a result of land clearing, is a widespread environmental change, which threatens numerous taxa, but provides an opportunity to elucidate such mechanisms. Although salinisation affects terrestrial fauna and flora, the greatest impacts are seen in wetlands and waterways. Many aquatic insect taxa colonise ephemeral water bodies directly as adults or by oviposition. Few empirical studies, however, evaluate the influence of abiotic factors, such as water body salinity, on the colonisation behaviour of aquatic fauna. We conducted a manipulative experiment using mesocosms to test whether colonising insect fauna select aquatic habitats based upon salinity. We found that halosensitive fauna selected less saline mesocosms for oviposition and colonisation, demonstrating that behaviour can influence the distribution of aquatic organisms. Additionally, we utilised field surveys of insects from ephemeral water bodies across a broad region of southwest Western Australia to determine if mesocosm results reflected field observation. The abundance of the same insect taxa and taxonomic groups in the field were highly variable and, with the exceptions of Culex australicus Dobrotworksy and Drummond and Anopheles annulipes Giles (Diptera: Culicidae), did not show similar patterns of distribution to those observed in the mesocosm experiment. Both mesocosm and field assemblages exhibited similar and significant trajectories associated with the salinity gradient, even though there were differences in assemblage structure between the two. Our findings give empirical support to the importance of behaviour in the spatial distribution and assembly of some aquatic insects.

Is there a risk of malaria transmission in NSW?

NSW has a putative malaria vector in Anopheles annulipes, and increased numbers of immigrants from malaria endemic countries who may be infective to mosquitoes but asymptomatic. We examine the factors known to influence malaria transmission and conclude that local transmission is possible but unlikely. The public health implications are that there should be systematic screening of immigrants from malaria endemic countries on arrival, and that the public health capacity to identify and respond to a malaria outbreak should be maintained.

Species-richness of the Anopheles annulipes complex (Diptera: Culicidae) revealed by tree and model-based allozyme clustering analyses

The Australasian Anopheles annulipes complex contains at least ten sibling species, some of which are important vectors of myxomatosis in rabbits. We aimed to establish how many species occurred among specimens from 61 sites throughout Australia, scored for 32 putative allozyme loci. We compared the number of species predicted from tree-based clustering of operational taxonomic units (OTUs) with that from a novel model-based Bayesian clustering approach for individual genotypes. We rejected the hypothesis of conspecificity of OTUs if they differed by at least 20% fixed differences and 0.300 Nei's standard genetic distance D. According to these criteria, 18-25 species occur, making this the most species-rich anopheline complex known to date. A conservative estimate from the Bayesian analysis was 15-20 species. There was large overlap in the assignment of individuals to clusters inferred from the Bayesian and tree-based analyses. The genetic clustering of northern and southern distributed species and an apparent cline in alleles of the enzyme glucose phosphate isomerase suggest that a latitude-dependent factor, such as temperature, may have played a role in speciation and the subsequent distribution of species. Ecological niche modelling of clusters predicted that none occur in New Guinea, emphasizing that additional, as yet unsampled, species may occur. (c) 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 523-539.

Distribution of sibling species of the Anopheles annulipes complex (Diptera: Culicidae) in the Townsville region of Australia

Abstract As members of the Anopheles annulipes species complex have been implicated as possible malaria vectors in the past, their response to dams and urban development is of medical interest. We collected An. annulipes sensu lato (s.l.) Walker from the Ross River Dam and environs of tropical north Queensland, and scored them for 28 allozyme loci. Allozyme genotype data were analysed by the Unweighted Pair Group Method of Analysis applied to percentage fixed allelic differences (%FD) and by a Bayesian clustering approach. Both approaches revealed four groups, which differed by more than 25%FD, suggesting four species. Specimens sequenced for the Internal transcribed spacer subunit 2 of rDNA suggested that three of these groups were An. annulipes species D, species I and species O. Anopheles annulipes species D occurred in the Ross River and the Ross River Dam, An. annulipes species O inhabited rock pools, and An. annulipes species I inhabited both rock pools and artificial containers in domestic situations. Construction of the Ross River Dam appears to have benefited at least An. annulipes species D, and nearby housing development An. annulipes species I. Although An. annulipes s.l. does not appear to be a major medical risk, mosquito monitoring around Townsville may need to take into account the multispecies status of this taxon.

Effects of Habitat Permanence Cues on Larval Abundance of Two Mosquito Species

Fluctuations in mosquito populations can often be correlated with the level of rainfall in the short term, however, rainfall rarely corresponds to mosquito abundance in the long term. Here, we present results of a field based mesocosm experiment designed to test how variables associated with drought influence larval abundance of two species of mosquitoes. We used two water volumes (2 and 4 l) and two drought water concentrations (high and low). The two mosquito species present in these ponds, Ochlerotatus notoscriptus and Anopheles annulipes, differed markedly in larval abundance. The number of larvae of O. notoscriptus observed was significantly greater in high drought water treatments regardless of water volume, and did not co-vary with any water chemistry parameters measured. In contrast, A. annulipes larvae were significantly more abundant in the greater water volume treatments regardless of drought water concentrations. This pattern co-varied with the pH of the pond water. These results indicate that mosquito species may show variances in their oviposition site selection and larval development depending on water depth and drought history.

Timing of host‐seeking behaviour of the mosquitoes Anopheles annulipes sensu lato Walker and Coquillettidia linealis (Skuse) (Diptera: Culicidae) in the Murray River Valley, South Australia

Abstract The timing of host‐seeking behaviour was studied in two mosquito species, Anopheles annulipes sensu lato and Coquillettidia linealis at Mundic Creek, near the Upper River Murray in South Australia. Hourly sampling using carbon dioxide‐baited traps revealed consistent patterns in the timing of host‐seeking. Coquillettidia linealis displayed a very large peak in host‐seeking activity at sunset, followed by a much reduced level throughout the night and a smaller peak at sunrise. Anopheles annulipes s.l. differed by displaying a significantly smaller peak at sunset, followed by higher amount of activity throughout the night compared with Cq. linealis. The two taxa, while both crepuscular and nocturnal, spread their host‐seeking effort out differently throughout the night, indicating that they have different resource requirements.

Isolation of Ross River virus from mosquitoes and from horses with signs of musculo-skeletal disease.

To report clinical and clinicopathological findings in horses naturally infected with Ross River virus (RRV) and identify likely mosquito arbovirus vector species. Veterinarians submitted serum samples from 750 horses because they suspected Ross River virus (RRV) infection. The samples were tested for the presence of IgM and IgG antibody to RRV and for the presence of virus. Mosquitoes were trapped, differentiated to species level and tested for the presence of RRV by virus isolation. RRV was isolated from six species of mosquitoes (Ochlerotatus camptorhyncus, Culex globocoxitus, Cx. australicus, Cx. annulirostris, Cx. quinquefasciatus, Anopheles annulipes) and from 13 horses with clinical signs of musculo-skeletal disease. Antibody to RRV was detected in 420 of the 750 serum samples; 307 contained IgG only; 76 contained both IgM and IgG and 37 contained only IgM antibody to RRV. Virus was isolated from horses with IgM antibody only. RRV can be isolated from infected horses during the short time period when there is an overlap of clinical signs, positive IgM serology and viraemia. Early spring infections of horses may occur if RRV infected mosquito vectors are present. RRV has not been shown to cause clinical disease in horses. This is the first report of isolation of RRV from Oc. camptorhyncus in the Murray region and indicates a potential for infection of humans and animals in autumn as well as in spring.

Mosquito (Diptera: Culicidae) dispersal: implications for the epidemiology of Japanese and Murray Valley encephalitis viruses in Australia.

One hypothesis to explain the southern extension of Japanese encephalitis (JE) virus from Papua New Guinea into the Torres Strait islands in 1995 and to mainland Australia in 1998 is the dispersal of infected mosquitoes, particularly Culex annulirostris Skuse from which JE virus has been isolated repeatedly. To investigate whether this species disperses in this manner, mosquitoes were identified from 368 aerial kite trap collections operated at 50-310 m (altitude) at inland New South Wales between November 1979 to December 1984. Forty samples (9 during daylight and 31 at night) contained mosquitoes, of which 221 could be identified as Culex australicus Dobrotworsky & Drummond (58.8%), Culex annulirostris (21.3%), Anopheles annulipes Walker s.l. (10.4%), Aedes theobaldi (Taylor) (7.2%), Aedes rubrithorax (Macquart) (1.4%), and Aedes sagax (Skuse) (< 0.9%). During the night, mosquitoes were found in 22.6% of the collections at a mean density (+/- SD) of 91.3 +/- 151.7/10(6) m3 of air sampled. During the day, only 3.8% were positive at a mean density 125.3 +/- 152.1. When examined in relation to possible flying time and wind speed, mean +/- SD dispersal distances by day and night were 23.9 +/- 15.3 km and 152.4 +/- 116.3 km, respectively. These data provide circumstantial evidence that aerial carriage southward approximately 200 km from Papua New Guinea to Cape York peninsula is feasible, but that southern dispersal of Murray Valley encephalitis virus infected mosquitoes from tropical to temperate Australia is unlikely.

The gecko: an environmentally friendly biological agent for mosquito control.

Laboratory experiments with Aedes aegypti mosquitoes investigated the effects of light, mosquito density and physiological state on predation rates by the Australian gecko Gehydra dubia and the exotic Asian house gecko Hemidactylus frenatus. For both gecko species a positive correlation was demonstrated between prey density and the predation rate. Using Ae.aegypti males and unfed females as prey in a terrarium (0.054 m3), consumption rates reached 76-108/day for G.dubia and 63-109/day for H.frenatus, with significantly more female mosquitoes than males being eaten in most experiments. Comparing dark with semi-illuminated conditions no consistent contrast of predation rate was demonstrated. Gehyra dubia predation rates on various Australian mosquito species were compared in an experimental room (32 m3) for 24 h exposure with photoperiod L:D 12:12 h Five photophilic species (Aedes vigilax, Anopheles annulipes, Coquillettidia xanthogaster, Culex annulirostris, Cx sitiens) suffered 78-100% predation, compared with only 33-53% predation of four non-photophilic species: Aedes aegypti, Ae.notoscriptus, Ae.vittiger and Cx quinquefasciatus. This demonstrates the potential benefit of domestication for geckoes that learn to hunt at light. When offered a mixture of unfed, freshly blood-fed and gravid females of Ae.aegypti in an illuminated terrarium, both gecko species consumed significantly more unfed than fed or gravid female mosquitoes, presumably because the latter rested whereas the former foraged more actively. H.frenatus consumed significantly more mosquitoes of all categories than did G.dubia per 24 h: unfeds 5.1 +/- 0.1% v. 4.5 +/- 0.5%, blood-feds 4.5 +/- 0.3% v. 4.0 +/- 0.5% and gravids 4.8 +/- 0.4% v. 3.9 +/- 0.5%. Possible relevance of these results to competitive displacement of G.dubia by H.frenatus is discussed.

Abundance and Spaital Distribution of Mosquitoes at Lake Bullawarra, Queensland (Diptera: Culicidae)

During 1976–78, seven trips were made to Lake Bullawarra and 29,118 mosquitoes comprising 19 species were collected. Vertical and horizontal distribution of mosquitoes was investigated using chicken baited traps at three different heights (0,6 and 12 m) and three horizontal distances from shore (0, 31 and 57 m). Culex quinque fasciatus was the most localised species, being captured at ground level and close to the lake shore. Culex annulirostris, Anopheles annulipes s.l. and Aedes eidsvoldensis were also more common close to the ground, but no significant differences in the distribution of these species were found away from the lake edge. These species were also the most common in the majority of the other collections.

Mosquito Collections and a Virus Isolation from Lake Nuga Nuga, Central Queensland (Diptera: Culicidae)

ABSTRACTDuring April‐June 1977 mosquito collections were made at Lake Nuga Nuga, south of Rolleston. A total of 37 male and 533 female mosquitoes were collected using human bait or as resting adults. 99% were either Anopheles annulipes s.l. or Aedes vittiger. the female mosquitoes were processed for virus isolation and Parkers Farm virus was isolated from a pool of Ae vittiger.

MONTHLY PERIODICITY AND ABUNDANCE OF MOSQUITOES (DIPTERA: CULICIDAE) NEAR BATEMANS BAY ON THE SOUTH COAST OF NEW SOUTH WALES, 1985?1988

During an investigation of the seasonal activity of mosquitoes and arboviruses in two coastal native forests, collections of adult mosquitoes with dry-ice baited light traps led to the determination of a fauna comprising 34 species for the Termeil State Forest and 33 species for the Mogo State Forest/Batemans Bay locality. The monthly collection data for all species are presented, revealing the dominance of the saltmarsh pest species Aedes vigilax (Skuse) at Mogo, and the sylvan freshwater species Anopheles annulipes Walker s.l. and Coquillettidia linealis (Skuse) at Termeil. The results reflect the respective environments with the extensive saline marsh and mudflat habitats at Batemans Bay contrasting with the predominantly freshwater marsh and lake habitats of Termeil.

Mosquito (Diptera: Culicidae) and Arbo virus Activity on the South Coast of New South Wales, Australia, in 1985–1988

An investigation of the seasonal activity of adult mosquitoes and arboviruses in two native forests revealed a mosquito fauna comprising 33 species for the Mogo State Forest-Batemans Bay locality and 34 species for the Termeil State Forest. The mosquito Aedes vigilax was the most abundant species in salt marshes at Mogo State Forest-Batemans Bay, whereas the freshwater species Anopheles annulipes s.l. and Coquillettidia linealis were most abundant at Termeil State Forest. Major faunal differences between the two environments reflected the extensive saline marsh and mudflat estuarine habitats at Batemans Bay and the predominantly freshwater stream, marsh, and lake habitats of Termeil State Forest. A total of 218 virus isolates was recovered from the mosquitoes, comprising Ross River virus (86 isolates), Gan Gan virus (123 isolates), Termeil virus (2 isolates), and 7 unidentified viruses. The period of greatest arbovirus activity was from midsummer through midautumn and coincided with the overall peak activity of the most common mosquito species. Ae. vigilax yielded most isolates of Ross River and Gan Gan viruses and appeared to be the vector of greatest public health concern.

ANOPHELES ANNULIPES WALKER (DIPTERA: CULICIDAE) AT GRIFFITH, NEW SOUTH WALES. 2. BIOLOGY AND BEHAVIOUR OF TWO SIBLING SPECIES

AbstractTwo 2 sibling species, previously concealed within Anopheles annulipes, are sympatric at Griffith. The species are provisionally designated as species A and species G. Larvae of both species were found together at some sites. However, relatively few larval habitats of species G were found suggesting that major habitats were undetected. Typical sites for species A were the margins of slow moving drainage canals with filamentous algae. Adults of species A were more abundant closer to Griffith township. Adults of species G were predominant away from Griffith in flooded rice and pasture areas. Species A females developed faster than species G females. In both species, nocturnal activity patterns were similar with most biting occurring in the first few hours after dusk with minor activity peaks around midnight and dawn. Paired EVS trap and human‐bait collections indicated that species A was the more anthropophilic.