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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-
DOI link for 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-
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-
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