Letteratura scientifica selezionata sul tema "Culex annulirostris"

Furlong, Morgan, Andrew Adamu, Roslyn I. Hickson, Paul Horwood, Maryam Golchin, Andrew Hoskins e Tanya Russell. "Estimating the Distribution of Japanese Encephalitis Vectors in Australia Using Ecological Niche Modelling". Tropical Medicine and Infectious Disease 7, n. 12 (22 novembre 2022): 393. http://dx.doi.org/10.3390/tropicalmed7120393.

Williams, Simon H., Avram Levy, Rachel A. Yates, Nilusha Somaweera, Peter J. Neville, Jay Nicholson, Michael D. A. Lindsay et al. "The Diversity and Distribution of Viruses Associated with Culex annulirostris Mosquitoes from the Kimberley Region of Western Australia". Viruses 12, n. 7 (2 luglio 2020): 717. http://dx.doi.org/10.3390/v12070717.

Ritchie, Scott A., Debbie Phillips, Michael Poidinger, John Mackenzie, Andrew Van Den Hurk e Annette Broom. "Isolation of Japanese Encephalitis Virus from Culex annulirostris in Australia". American Journal of Tropical Medicine and Hygiene 56, n. 1 (1 gennaio 1997): 80–84. http://dx.doi.org/10.4269/ajtmh.1997.56.80.

Hanford, Jayne K., Dieter F. Hochuli e Cameron E. Webb. "Oviposition Behavior of Culex annulirostris (Diptera: Culicidae) Is Affected by the Recent Presence of Invasive Gambusia holbrooki (Cyprinodontiformes: Poeciliidae)". Journal of Medical Entomology 56, n. 4 (24 marzo 2019): 1165–69. http://dx.doi.org/10.1093/jme/tjz027.

Williams, C. R., B. P. C. Smith, S. M. Best e M. J. Tyler. "Mosquito repellents in frog skin". Biology Letters 2, n. 2 (21 febbraio 2006): 242–45. http://dx.doi.org/10.1098/rsbl.2006.0448.

MOTTRAM, P., e D. S. KETTLE. "Development and survival of immature Culex annulirostris mosquitoes in southeast Queensland". Medical and Veterinary Entomology 11, n. 2 (aprile 1997): 181–86. http://dx.doi.org/10.1111/j.1365-2915.1997.tb00311.x.

Sweeney, A. W., Edwin I. Hazard e M. F. Graham. "Intermediate host for an Amblyospora sp. (Microspora) infecting the mosquito, Culex annulirostris". Journal of Invertebrate Pathology 46, n. 1 (luglio 1985): 98–102. http://dx.doi.org/10.1016/0022-2011(85)90133-8.

Van den Eynde, Claudia, Charlotte Sohier, Severine Matthijs e Nick De Regge. "Japanese Encephalitis Virus Interaction with Mosquitoes: A Review of Vector Competence, Vector Capacity and Mosquito Immunity". Pathogens 11, n. 3 (3 marzo 2022): 317. http://dx.doi.org/10.3390/pathogens11030317.

Boyd, Ann Marie, e Brian H. Kay. "Vector Competence of Aedes aegypti, Culex sitiens, Culex annulirostris, and Culex quinquefasciatus (Diptera: Culicidae) for Barmah Forest Virus". Journal of Medical Entomology 37, n. 5 (1 settembre 2000): 660–63. http://dx.doi.org/10.1603/0022-2585-37.5.660.

Russell, Richard C. "CULEX ANNULIROSTRIS SKUSE (DIPTERA: CULICIDAE) AT APPIN, N. S. W.?BIONOMICS AND BEHAVIOUR". Australian Journal of Entomology 25, n. 2 (maggio 1986): 103–9. http://dx.doi.org/10.1111/j.1440-6055.1986.tb01087.x.

Wells, Peter J. "Vector competence of aedes vigilax (Skuse) and culex annulirostris Skuse (Diptera:Culicidae) for Ross River virus, and some other alphaviruses and bunyaviruses". Thesis, The University of Sydney, 1994. https://hdl.handle.net/2123/27471.

"lake was larger, aerial photography was used to estimate the extent of the floating algal mats. This was then scanned into a computer, digitized and estimates made. During April and November 1991 and in September 1992, Hydrilla covered between 13.3 and 16.6 km of the stage 2A lake, and this was estimated to contain populations of 5.6 billion, 275 million and 513 million immatures, respectively, mainly Culex annulirostris and Anopheles annulipes as before. However, whereas Culex annulirostris comprised 90–98 per cent of aquatic stages during 1985–86, now Anopheles annulipes s.l. comprised 43.7 per cent of all the immatures identified. Although natural mortality will reduce the numbers actually reaching adulthood, these numbers are so high that some form of control is indicated. As discussed previously, one can only speculate on the abundance of mosquito larvae that will utilize marginal emergent vegetation when it develops fully along the foreshores of the stage 2A lake. At present, from the 1991–93 data, the average number of mosquito immatures based on transects 5 m wide was 85.7/m Because the shoreline contains bare". In Water Resources, 146. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-33.

"in Kununurra; indeed, occasional seroconversions have been recorded in every month of the year. Elsewhere in the Kimberley region, seroconversions occur in most years towards the end of the wet season at all sites monitored, but the overall frequency tends to be less than that observed in Kununurra, except when flooding is extensive and widespread. Until about 1990, most seroconversions in sentinel chickens in the Pilbara region were due to infections with Kunjin virus, but over the next three years seroconversions to MVE virus showed a significant increase in incidence, suggesting that virus movement from the Kimberley region may be occurring more often. Since 1993, however, Kunjin virus activity has once again become more prevalent in the Pilbara area. Mosquito collections Continuing studies in 1976 and 1977 in the Ord River area using bait traps showed that while Culex annulirostris continued to dominate the mosquito fauna of the area, other species such as Coquillettidia xanthogaster, Mansonia uniformis and Anopheles bancroftii increased in number following stabilization of the margins of Lake Kununurra and the prolific growth of aquatic plant species (Wright 1981). Studies in the West Kimberley area in 1977 in the Derby area also found that Culex annulirostris was the dominant mosquito species (Wright et al. 1981). A major advance in mosquito trapping in the north of Western Australia was the introduction of the EVS-CO light trap in 1978, which replaced the use of bait traps after 1979. This resulted in a ninefold increase in the number of mosquitoes being collected, and a significant increase in the species diversity, although Culex annulirostris remained the dominant species (Stanley 1979). Annual mosquito collections have continued to be undertaken in the Ord River area and at other sites in the Kimberley region since 1978, particularly at the end of the wet season although also at other times if unusual environmental conditions such as cyclones or early wet season flooding have occurred. With the stabilization of Lakes Argyle and Kununurra and of the area under irrigation, the results obtained have provided a clearer association between environmental conditions, mosquito numbers and virus activity (see below). Although the mosquito density, and thus the number collected, is always relatively high in the Ord River area, heavy wet season rainfall and flooding result in a significant increase in the mosquito density. In other areas of the Kimberley, a similar pattern has emerged but the increase in the mosquito density is often more marked than in the Ord River area, and the proportion of different mosquito species tends to vary considerably. Nevertheless, regardless of the study area, Culex annulirostris dominates after widespread heavy rainfall and flooding, but if the rainfall is more localized, other floodplain breeding species such as Aedes normanensis may dominate initially (e.g. Broom et al. 1992)." In Water Resources, 132. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-25.

"Virus isolations Mosquito collections obtained during most field trips to the north-west of Western Australia have been processed for virus isolation. Until 1985, virus isolation was undertaken by intracerebral inoculation of suckling mice, but this was then replaced by cell culture using C6/36 mosquito, PSEK, BHK and Vero cells. The use of cell culture has significantly reduced the overall virus isolation rate by largely excluding arboviruses, rhabdoviruses and most bunyaviruses, but is as effective as suckling mice for the isolation of flaviviruses and alphaviruses. MVE virus has been isolated every year that significant numbers of adult mosquitoes have been processed except 1983 (Broom et al. 1989; Broom et al. 1992; Mackenzie et al. 1994c). Isolations of MVE, Kunjin and other flaviviruses are shown in Table 8.2. There was a strong correlation between the number of virus isolates in any given year and the prevailing environmental conditions. Thus those years with a heavy, above average wet season rainfall and subsequent widespread flooding yielded large numbers of virus isolates (1981, 1991, 1993) compared with years with average or below average rainfall and with only localized flooding. Although most MVE virus isolates were obtained from Culex annulirostris mosquitoes, occasional isolates were also obtained from a variety of other species, including Culex quinquefasciatus, Culex palpalis, Aedes normanensis, Aedes pseudonormanensis, Aedes eidvoldensis, Aedes tremulus, Anopheles annulipes, Anopheles bancroftii, Anopheles amictus and Mansonia uniformis (cited in Mackenzie et al. 1994b; Mackenzie and Broom 1995), although the role of these species in natural transmission cycles has still to be determined. Virus carriage rates in Culex annulirostris mosquitoes are shown in Table 8.3 for the Ord River area (Kununurra–Wyndham) and Balgo and Billiluna in south-east Kimberley. Very high mosquito infection rates were observed in those years with above average rainfall. Virus spread and persistence Stanley (1979) suggested that viraemic waterbirds, which are often nomadic, may generate epidemic activity of MVE in south-east Australia and in the Pilbara region. In an attempt to understand the genesis of epidemic activity better, our laboratory initiated a long-term study in the arid south-east Kimberley area at Billiluna and Balgo, two Aboriginal communities on the northern edge of the Great Sandy Desert. Occasional cases of Australian encephalitis had occurred in both communities (1978, 1981). The studies have clearly shown that MVE virus activity only occurs following very heavy, widespread rainfall both locally and in the catchment area of the nearby watercourse, Sturt Creek, which results in extensive flooding across its floodplain (Broom et al. 1992). Localized flooding is insufficient to generate virus activity. Two possible explanations can be proposed to account for the reappearance of MVE virus activity when environmental conditions are suitable: either virus can be reintroduced into the area by viraemic waterbirds arriving from enzootic areas further north; or virus may". In Water Resources, 133–35. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-26.

"sion dam (Stanley 1979). Most of the species collected in the bait traps were those associated with permanent and semipermanent fresh water breeding sites, and the dominant species was Culex annulirostris, which accounted for over 70 per cent of the collections (Liehne et al. 1976a; Stanley 1979). Thus the major vector species for MVE virus was shown to be abundant in the Ord River irrigation area. The major mosquito breeding areas were in swampland adjacent to the diversion dam. Little breeding activity was found in the irrigation area probably due to the excessive use of insecticides applied by aerial spraying for controlling insect pests on cotton crops. However, cotton was discontinued as a crop in 1975, and an increased number of mosquitoes began to appear in 1976. • Viruses. Pools of mosquitoes were processed for virus isolation by intracerebral inoc-ulation of macerated mosquito supernatants into suckling mice. A total of 195 strains of 16 arboviruses were isolated from 1075 pools, of which 29 were identified as MVE virus and 21 as Kunjin virus. The majority of the isolates were made from Culex annulirostris (153 of 195 isolations), including 28 of 29 identified as MVE. Thus the overall virus isolation rate was high (18 per cent). For MVE virus from Culex annulirostris, 3.5 per cent of pools yielded virus at an approximate rate of 1 infected mosquito per 1459 uninfected mosquitoes (Liehne et al. 1976b; 1981). • Serological studies of animals and birds. All the early serological investigations employed the haemagglutination-inhibition (HI) assay. Cattle sera obtained from the Ord River irrigation area exhibited a high incidence of antibody to MVE virus (80 per cent positive), but the incidence declined to 37 per cent positivity in sera collected elsewhere in the Kimberley region (Liehne et al. 1976c). A very significant increase in the incidence of antibody to MVE was observed in cattle between 1972 and 1975 in the irrigation area and nearby cattle properties, with increases ranging from between 22 and 36 per cent to between 75 and 90 per cent (Stanley 1979). While the establishment of the irrigation area and the completion of the Ord River dam were undoubtedly responsible for some of this increase, it is probable that the very heavy ‘wet’ season rainfall in 1973–74 also contributed. • Of 335 sera collected from 31 avian species, 195 were found to have antibody to MVE virus. Although only a few species were sampled in moderate or large num-bers, it was interesting to note that the incidence of antibody was similar between waterbirds and non-waterbirds (56 and 59 per cent, respectively), and between differ-ent avian orders: Ciconiiformes (herons, egrets), 62 per cent; Anseriformes (ducks, grebes), 55 per cent; and Psittaciformes (parrots), 56 per cent, (Liehne et al. 1976c). • Human serological studies. A total of 441 human sera were collected in the Ord River area, of which 293 were from Caucasians and 148 from Aboriginals. A very high incidence of MVE antibodies was observed in the Aboriginal population, with 96 per cent of adults and 77 per cent of children exhibiting antibodies. In the Caucasian pop-ulation, the incidence of MVE virus antibodies was 53 per cent in adults and 24 per". In Water Resources, 129. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-22.

"waterbird populations and provide additional mosquito breeding habitats, which would be conducive to increased arbovirus activity (Stanley 1972; 1975). Indeed the potential problems were expected to become more acute as the population in the area increased with the development of Kununurra township and nearby farming activities, and with increased tourism and mining opportunities. More than sixty-five arboviruses have been isolated in tropical Australia, but only a few have been implicated in human disease (Mackenzie et al. 1994a). These include the flaviviruses Murray Valley encephalitis (MVE), Kunjin, Kokobera, Alfuy, Edge Hill and dengue; and the alphaviruses Ross River, Barmah Forest, and Sindbis (Mackenzie et al. 1994a; 1994b). With respect to the Ord River irrigation area, the most important of these viruses is MVE, the major cause of Australian encephalitis. MVE virus has a natural biocenose between waterbirds, particularly members of the order Ciconiiformes, and mosquitoes, particularly the fresh-water breeding species, Culex annulirostris. MVE virus is a member of the Japanese encephalitis serological complex of flaviviruses, and is more closely related to Japanese encephalitis virus than are the other Australian members of the complex (Kunjin, Kokobera, Alfuy and Stratford viruses)." In Water Resources, 127. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-20.

"a water purifier and a food source and haven for the abundant wildlife at the reservoir? We think not. This option will be discussed later. 9.4.2 Arboviruses From 1983 to 1987, domestic chicken flocks were maintained as sentinels (Figure 9.3) and bled for the presence of antibodies to both alphaviruses (e.g. Ross River virus) and flaviviruses (e.g. Murray Valley encephalitis, Kunjin viruses). These data showed that alphavirus activity occurred annually but this infection was somewhat unpredictable and did not necessarily correlate with the zones of highest mosquito abundance closest to the reservoir. Flavivirus infection occurred far less frequently. From 1990–93, 51,497 adult female mosquitoes were processed for the presence of alphaviruses using enzyme immunosorbent assay and polymerase chain reaction methods (Kay et al. 1996; Oliveira et al. 1995). Ten isolates of Ross River, one of Barmah Forest and two of Sindbis virus strains were recovered from Aedes normanensis, Anopheles amictus and Culex annulirostris, which indicated that they were probably local vectors. All virus stains were recovered from mosquitoes collected during the wet seasons (February or March) of 1991 or, especially, 1992. Relative hazard was assessed for four Ross River dam localities: Big Bay (north); Antill Creek (north-east); Toonpan (east); and Ross River (south). These were compared with more". In Water Resources, 147. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-34.

"As an adjunct to this, egg masses of Austropeplea were hatched out and reared in constant temperature rooms at 15°C, 25°C and 30°C with weekly changes of water and vegetation (Figure 9.5). Shell length was measured weekly until time of reproduction. At 15°C the snails grew slower but lived longer, but at 25°C and 30°C, there was little difference in growth rates, although those at 25°C were marginally larger at equivalent periods. Although water temperatures at the Ross River dam do occasionally drop to 16°C on occasions, generally they average 25–28°C (Hurley et al. 1995). Thus from this, an Austropeplea of 12 mm shell length collected during summer will be around one month old and capable of reproducing. One of 20 mm at either 25°C or 30°C water temperature would be approximately 100 days old. On this basis, it is suggested that monitoring could be comfortably done every two to three months. 9.6 Management options 9.6.1 General conclusions There are several other lakes, man-made or otherwise in northern Queensland, that support diverse recreational activities without apparent mishap. All are subjected to tropical conditions conducive to year round production of mosquitoes, snails, mites and pathogens. What is different about the Ross River dam stage 2A is its shallowness and proximity to large human populations. Nevertheless, the studies carried out in two blocks (1983–1987 and 1990–1995) have defined its mosquito and alphavirus hazard as considerable but no greater in the northern and north-eastern areas of Big Bay, Ti-Tree Bay, Round Island and Antill Creek than that experienced by local residents in everyday life. The relative hazard would change considerably, however, if the responsible local authorities ever decided to mount a broadscale aerial control programme against larval Aedes vigilax, which breed in the extensive intertidal wetlands. Restriction of activities to daylight hours will not only facilitate easier control of the public but will also reduce exposure to key vector species such as Culex annulirostris, Anopheles amictus and Aedes normanensis. However, who takes the responsibility for an estimated 5 billion mosquito larvae found periodically in the floating Hydrilla beds? As discussed, both Culex annulirostris and Anopheles annulipes are quite capable of dispersing from the reservoir into the urban populace. Recreational management issues are probably far less complicated than the moral issues. Whereas land clearance prior to the flooding of the stage 2A lake was effective in controlling tropical itch mites and some mosquito species, it also probably effected a redistribution of the kangaroos and wallabies, known to be most effective intermediate hosts of some arboviruses, including Ross River and the often fatal Murray Valley encephalitis. They have probably been driven towards the quieter eastern areas around Toonpan, where in 1992 Ross River virus was detected in wet season Aedes normanensis at rates as low as 1:217". In Water Resources, 151. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-38.

"This will be discussed later. Two species, Mansonia uniformis and Mansonia septempunctata, which breed in association with macrophytes such as water hyacinth Eichhornia crassipes, became less common from stage 1 to 2. The saltmarsh species Aedes vigilax was also collected in reasonable numbers at all localities around the reservoir. This species is known for its wide dispersal powers and was undoubtedly blown in from the extensive intertidal wetlands on the coast. Thus on the basis of abundance, two taxa – Culex annulirostris and Anopheles annulipes s.1. – warranted further consideration. The former species is considered to be the major vector of arboviruses in Australia (Russell 1995), transmitting Ross River, Barmah Forest, Kunjin, Kokobera, Alfuy and Edge Hill viruses and Murray Valley encephalitis, as well as dog heartworm. Of these, Ross River is by far the most common arbovirus in coastal northern Queensland, with morbidity approximating 400 cases per 100,000 population. Thus from first principles, this arbovirus and perhaps Barmah Forest, about which little is known, would constitute the greatest hazard to recreational use. Although Anopheles annulipes has previously been implicated in malaria transmission at Sellheim during the Second World War, this species group has returned isolated positives of Ross River and Barmah Forest viruses and Murray Valley encephalitis from other parts of Australia. However, no transmission studies have been done on the population from the reservoir. Thus on the evidence to date, it could not be regarded as a major concern at the Ross River dam. Both Culex annulirostris and Anopheles annulipes were shown to have seasonal peaks of abundance during the late post-wet season (March to May), with populations building up with the onset of spring (September to October). Spatially, the trapping programme was designed to compare mosquito numbers on the foreshore of the stage 1 lake with two localities expected to be on the margins of the stage 2A lake, with two remote localities (and therefore theoretically unaffected by any water resource project activity) as negative controls. Mosquito numbers (i.e. for those species known to breed at the dam) decreased with distance away from the Ross River dam. Both light trapping and human bait collections carried out twice per month were reasonable indicators of broad seasonal trends in mosquito abundance. However, the statistical analysis indicated that occasionally the light traps could miss short periods of high biting activity (Jones et al. 1991). If greater resolution was required, it was recommended that light traps could be supplemented with animal baited traps, although it is probable that this could be rectified by intensifying the light trapping regimen. Cluster analyses of dam breeding species in both 1984–85 and 1991–93 indicated that light trap catches along the northern (Big Bay, Ti-Tree Bay, Round Island) and western sides (Ross River) gave similar patterns, but the profile towards the east (Antill Creek, Toonpan, Oak Valley) was somewhat different (Barker-Hudson et al. 1993; Hearnden and Kay 1995). On this basis, adult mosquito surveillance would therefore need to be based on two localities at either end of the lake." In Water Resources, 143. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-31.

"The report recognized the need to minimize disturbance of fauna and flora and suggested that ‘swimmer’s itch’, caused by avian schistosome cercariae, and mosquito-borne viruses should be investigated. Because the 26 km northern boundary, e.g. Big Bay, Antill Creek, had steeper foreshores and deeper water, it was recommended as a primary site for public access. The 7 km western boundary formed by the dam wall was seen as ideal for viewing opportunities of the lake and surrounding hills and mountains, and for water sports. Because of inaccessibility, potential management difficulties and shallowness, the 47 km southern and eastern margins did not offer significant recreational opportunities. 9.3 Tropical itch mite The stage 1 lake was surrounded with open schlerophyll woodland which afforded kangaroos and wallabies shelter during the hottest times of the day. Part of their exoparasitic fauna is the mite Eutrombicula macropus, whose offspring spend part of their life-cycle hanging off grass stems and other vegetative matter waiting to encounter a new host. Much to their misfortune, campers and bushwalkers consequently often find themselves with an itchy rash called ‘tropical itch’, often around the lines of underclothing. Prior to the filling of the stage 2 lake, the land in the zone between the stage 1 and stage 2 margins was selectively cleared. This probably diverted the macro-pods to other wooded habitat. From November 1990 to 1992, 350 litter samples were processed using Berlese funnels and 40 W incandescent bulbs to drive any inhabitants into sample bottles containing 70 per cent alcohol. No Eutrombicula macropus were collected. Thus clearing would seem to present an effective management option against this pest, as well as having the other benefits detailed below. 9.4 Mosquitoes and arboviruses 9.4.1 Mosquitoes From April 1984 to September 1985 (stage 1), the primary questions related to definition of mosquito taxa and the suitability of different methods of catching adult mosquitoes for surveillance purposes. Twenty-six taxa were collected by all night carbon dioxide supplemented light traps or by human bait collections for one hour after sunset (Barker-Hudson et al. 1993; Jones et al. 1991). The numerically dominant species were Culex annulirostris and Anopheles annulipes (both species groups), which are traditionally associated with temporary fresh water pools along the lake margins, often among emergent vegetation. Of considerable surprise during September 1985 was the discovery of immatures of these species, plus Aedeomyia catasticta, utilizing extensive floating mats of the aquatic weed Hydrilla verticillata which sometimes covered 37 per cent of the surface of the lake." In Water Resources, 142. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-30.

"Little was known about MVE virus, its vertebrate hosts or its vectors before the establishment of the Ord River irrigation area. Early serological studies by Stanley and Choo (1961; 1964) on human sera collected in 1960 from Halls Creek in East Kimberley and Derby in West Kimberley had demonstrated that the virus was circulating in these areas. However, no clinical cases of encephalitis had been reported, which may have been due to the small human population in the region prior to 1960, to a lack of awareness by clinicians, to low virus carriage rates in mosquitoes, or to a combination of these factors. Similarly, no cases of encephalitis had been reported in the Northern Territory. The first clinical case of Murray Valley encephalitis (now known as Australian encephalitis) occurred in 1969 (Table 8.1), a fatal case that was acquired by a tourist south of the Ord River irrigation area (Cook et al. 1970). Only limited information was available on the mosquito species prevalent in the Ord River area before 1972, although Culex annulirostris, believed to be the major vector for MVE virus from studies carried out by Doherty and colleagues in north Queensland (Doherty et al. 1963), was found to be present (H. Paterson, personal communication to Stanley 1972), and was the dominant species (H. Paterson, personal communication to Stanley 1975). Thus prior to the completion of stage one of the Ord River irrigation area, serological evidence had been obtained to demonstrate that MVE virus caused subclinical human infections, but no clinical cases had been reported. Between the completion of stage one and stage two, the first clinical case of encephalitis was reported, and limited information on the mosquito fauna was obtained but without details of mosquito numbers or population dynamics. 8.3 Studies on Murray Valley encephalitis from 1972 8.3.1 Early studies, 1972—1976 A series of investigations on the ecology of MVE virus in the Ord River irrigation area and on the effect of the completion of the Ord River dam were initiated by Stanley and colleagues in 1972. The major components comprised: regular mosquito collections obtained just before and immediately after the wet season to determine the number and proportion of each species at different sites, and for isolation of viruses; serological studies of animals and birds to investigate their roles as possible vertebrate or reservoir hosts; and serological studies of the human population, both Caucasian and Aboriginal, to determine subclinical infection rates and to assess potential risks. These studies yielded a number of important findings which have provided the basis for much of our knowledge of MVE ecology in north-western Australia. The major findings were as follows. • Mosquitoes. Using live bait traps to collect mosquitoes, it appeared that there had been a significant increase in mosquito numbers since the construction of the diver-". In Water Resources, 128. CRC Press, 1998. http://dx.doi.org/10.4324/9780203027851-21.