Biomedical subjects
Publications and source records attributed to S A Ritchie.
Animal feed pellets containing lupin seed or alfalfa were added to ovitraps set in Cairns, Australia. Although they collected fewer Aedes eggs than Centers for Disease Control enhanced ovitraps, they did outperform tap water alone. A wooden tongue depressor collected comparable number of Aedes eggs as a Masonite board and seed germination paper.
The SRC gene encodes the proto-oncogene pp60(c-)(src), a tyrosine kinase implicated in numerous signal transduction pathways. In addition, the SRC gene is differentially expressed, developmentally regulated, and frequently overexpressed in human neoplasia. However, the mechanisms regulating its expression have not been completely explored. Here we describe the isolation of a new distal SRC promoter and associated exon, designated 1alpha, which we mapped to a position 1.0 kilobase upstream of the previously described SRC1A housekeeping promoter. Differential use of these promoters and their associated exons coupled with subsequent splicing to a common downstream exon results in c-Src transcripts with different 5' ends but identical coding regions. Promoter analysis following transient transfections into HepG2 cells mapped the minimal 1alpha promoter to a region 145 bp upstream of the major transcription start site. This region contained a consensus binding site for hepatic nuclear factor-1 (HNF-1), a liver-enriched transcription factor implicated in the regulation of a number of genes in liver, kidney, stomach, intestine, and pancreas. Subsequent mobility shift assays confirmed that HNF-1alpha isoform was the predominant factor interacting with this region of the promoter. Mutation of the HNF-1 site resulted in a dramatic reduction in SRC promoter activity. Cotransfection studies demonstrated the promoter could be strongly transactivated by the HNF-1alpha isoform but not by the related HNF-1beta factor. Consistent with these results, we demonstrated that transcripts originating from the SRC1alpha promoter display a tissue restricted pattern of expression with highest levels present in stomach, kidney, and pancreas. These results indicate that SRC transcriptional regulation is much more complex than previously realized and implicates HNF-1 in both the tissue-specific regulation of the SRC gene in normal tissues and the overexpression of c-Src in certain human cancers.
In the Cairns area of far north Queensland, Australia, the seasonal abundance of Anopheles farauti Laveran sibling species was studied at 6 locations, representing 3 habitat types, between August 1995 and September 1997. A total of 45,401 An. farauti s.l. was collected using CO2 + octenol baited CDC light traps, and consisted of 29,565 An. farauti No. 2, 14,214 An. farauti No. 3, and 1,622 An. farauti s.s. The relative abundance of all 3 species differed significantly by season and location. An. farauti No.2 was the dominant species except in Cairns, where An. farauti s.s. was most abundant, and at Ninds Creek, where An. farauti No. 3 predominated. The dominant species at each location was present year round, although peaks in seasonal abundance were observed. An. farauti s.s. populations were highest during the wet season (January-April). In lowland freshwater swamp habitats and 1 brackish location, An. farauti No. 2 was more abundant during the wet season. However, at the highland freshwater swamp habitat, populations of An. farauti No. 2 were highest during the late dry season and early wet season (October-December). There was a significant positive correlation of both temperature and rainfall with An. farauti s.s. and An. farauti No. 2 trap collections. There was a negative correlation between An. farauti No. 3 and temperature, indicating that this species may be more abundant during cool weather. Although there were significant relationships among weather variables and An. farauti s.l. collections, correlation values were generally low, indicating that other factors may contribute to variability among An. farauti sibling species trap collections.
Japanese encephalitis is a disease of major importance in Asia, which from 1995 has extended its range into the north of Australia. Culex annulirostris Skuse of the Culex sitiens subgroup of Culex was incriminated as the most likely mosquito vector. Because misidentifications previously have occurred within this subgroup, our paper defines electrophoretic methods to identify Culex specimens from Queensland and the Northern Territory in Australia and from Western Province in Papua New Guinea. In collections from 1996 to 1998 Culex sitiens Wiedemann, Cx. palpalis Taylor, and Cx. annulirostris comprised 93.1% of the total banded proboscis Culex mosquitoes collected; 6.9% remained unidentified to species by morphological or electrophoretic examination. The prevalence of Cx. palpalis was variable and appeared to be associated with below average rainfall during 1997. In Papua New Guinea, this species comprised up to 97.4% of banded proboscis Culex, with smaller numbers collected from the Torres Strait Islands and Cape York; none was collected from other Queensland localities. Cx. annulirostris was more prevalent during years of average or above average rainfall and was predominant in most localities, especially in the Torres Strait and Queensland. These data confirmed the problems in separating Cx. sitiens from Cx. palpalis and Cx. annulirostris using morphological characters.
After Japanese encephalitis (JE) virus emerged in the Torres Strait in Australia in 1995, investigations were initiated into the origin of the incursion. New Guinea was considered the most likely source, given its proximity to islands of the Torres Strait. Almost 400,000 adult mosquitoes were processed for virus isolation from 26 locations in the Western Province of Papua New Guinea (PNG) between February 1996 and February 1998, yielding three isolates of JE virus. Two isolates of Murray Valley encephalitis, 17 isolates of Sindbis, and 1 each of Sepik and Ross River viruses were also obtained. Nucleic acid sequences of the PNG JE isolates were determined in the prM region, and in a region overlapping a part of the fifth nonstructural protein and the 3' untranslated region. The PNG isolates belonged to genotype II, and shared > 99.2% identity with isolates from humans and mosquitoes from the Torres Strait, suggesting that PNG is the source of incursions of JE virus into Australia.
OBJECTIVE: To describe the circumstances of two cases of Japanese encephalitis (JE) in north Queensland in 1998, including one acquired on the Australian mainland. DESIGN: Serological surveillance of sentinel pigs for JE virus activity; serological surveys of humans and pigs and viral cultures of mosquito collections. SETTING: Islands in the Torres Strait and communities in the Northern Peninsula Area (NPA) and near the mouth of the Mitchell River in Cape York, Queensland, in the 1998 wet season (December 1997-May 1998). RESULTS: Sentinel pigs in the Torres Strait began to seroconvert to JE virus in February 1998, just before onset of JE in an unvaccinated 12-year-old boy on Badu island. By mid-April, most sentinel pigs had seroconverted. Numerous JE viruses were isolated from Culex annulirostris mosquitoes collected on Badu. In early March, a person working at the mouth of the Mitchell River developed JE. Serological surveys showed recent JE virus infection in 13 young pigs on a nearby farm, but not in 488 nearby residents. In NPA communities, sentinel pigs seroconverted slowly and JE viruses were isolated from three, but none of 604 residents showed evidence of recent infection. Nucleotide sequencing showed that 1998 JE virus isolates from the Torres Strait were virtually identical not only to the 1998 isolate from an NPA pig, but also to previous (1995) Badu isolates. CONCLUSIONS: JE virus activity was more widespread in north Queensland in the 1998 wet season than in the three previous wet seasons, but ecological circumstances (e.g., less intensive pig husbandry, fewer mosquitoes) appear to have limited transmission on the mainland. Nucleotide sequencing indicated a common source for the 1995 and 1998 JE viruses. Circumstantial evidence suggests that cyclonic winds carried infected mosquitoes from Papua New Guinea.
Population genetics of the mosquito Aedes vigilax (Skuse) (Diptera: Culicidae), a major vector of arboviruses (e.g. Barmah Forest, Ross River), were investigated to obtain an indirect estimate of mosquito dispersal characteristics in typical habitats of Aedes vigilax in south-east Queensland: on the off-shore islands of Moreton Bay and on the mainland where disjunct breeding populations of Ae. vigilax are distributed along intertidal marsh. Six allozyme loci were assessed for genetic differentiation between samples from 11 localities. Significant larval variation between some breeding sites was attributed to site-specific selection. Nonsignificant genetic differentiation was found among collections of adult mosquitoes caught in light traps throughout the study area (exceeding 60x27 km), indicating widespread dispersal. As distances of < or = 9 km over water did not appear to act as effective barriers to Ae. vigilax dispersal, localized control activities applied to Ae. vigilax breeding sites are unlikely to be effective against the vagile adult population. Therefore, the contiguous shires programme of broad acre control is endorsed to prevent the spread of arboviruses carried by Ae. vigilax
This research evaluated the use of qualitative presence/absence data compared with quantitative real number counts of Aedes vigilax eggshell data to obtain information on the spatial distribution of eggshells in several salt marsh vegetation types. Eggshells were extracted by subsampling and flotation, a method that does not recover all eggshells. The results of the analysis of presence/absence data were compared with those of real numbers. The general conclusions were similar by either method, suggesting that presence/absence data may be sufficient to rapidly determine eggshell distribution patterns.
Fifty-six adult female mosquitoes of the species Anopheles farauti sensu stricto--the arthropod vector for malaria--were collected from Mackay, central Queensland, at latitude 21 degrees 09'S, between August 1996 and August 1997. This is the southernmost record of this species, and may indicate that the malaria-receptive zone in Queensland needs to be expanded.
Arboviruses continue to be major human pathogens in the Australian region. This report provides a summary of the activities of these viruses over the past eight years, and comments on new findings relevant to their respective ecologies. Of particular interest and concern is the propensity of these viruses to spread. The examples discussed include the initiation of dengue epidemics in north Queensland by virus imported in viraemic travellers; the spread of Japanese encephalitis virus to the Australasian region and its probable enzootic establishment in the south-west of Papua New Guinea; the potential spread of Ross River virus to other countries, as demonstrated by the 1979-80 outbreak in the South Pacific, and the recent occurrence in military personnel from the United States of America after an exercise; and the recent spread of Barmah Forest virus into Western Australia.
OBJECTIVES: To investigate two outbreaks of dengue type 2 in north Queensland, one in the Torres Strait beginning in late 1996, the other in a Cairns suburb in early 1997. DESIGN: Epidemiological investigation of all laboratory-confirmed cases of dengue, entomological investigation of the local environment, and laboratory analysis of the isolated dengue viruses. MAIN OUTCOME MEASURES: Numbers of confirmed and of locally acquired cases; virus serotype; comparison of nucleotide sequences between viruses isolated from the two outbreaks; and Breteau Index (BI = number of containers with larvae of the mosquito vector Aedes aegypti found per 100 houses investigated) on the affected islands and in the Cairns suburb. RESULTS: There were 201 confirmed cases of dengue in the Torres Strait outbreak, which lasted nearly seven months, and seven confirmed cases in the Cairns outbreak, which lasted about nearly 11 weeks. Most (190) were confirmed as dengue type 2. Nucleotide sequencing of viruses isolated from the two outbreaks showed they were identical. Ae. aegypti breeding sites were very common on the five Torres Strait islands surveyed (BIs, 73-219--high risk), but less so in the Cairns suburb (BI, 23). The most common breeding sites were water storage reservoirs, particularly rainwater tanks, on the outer Torres Strait islands, discarded containers (such as plastic containers, buckets and tyres) on Thursday Island, and garden items (such as flowerpot bases and jars) in Cairns. CONCLUSIONS: The virus responsible for the Cairns outbreak was most probably introduced from the Torres Strait, whereas the virus responsible for the Torres Strait outbreak was imported from Papua New Guinea. Preventive strategies tailored to specific locations are needed to reduce breeding of Ae. aegypti in north Queensland, and the consequent risk of future outbreaks of dengue.
This prospective study's objectives were to describe the features of all episodes of malaria diagnosed in Far North Queensland (excluding the Torres Strait) and to assess how much of a threat they posed to the area's public health. Over a three-year period, 216 episodes of malaria were diagnosed (158 Plasmodium vivax and 68 P. falciparum infections). Most (82%) of the infections were acquired in Papua New Guinea (PNG). Approximately 70% of the episodes occurred in Australian citizens, about half of whom were in malaria-endemic countries for work; the remainder travelled abroad for recreation. Three-quarters of the Australian citizens with malaria had taken either no or inadequate prophylaxis. Australian citizens who had taken adequate prophylaxis were much less likely to develop P. falciparum than other types of malaria compared to those who took either no or inadequate prophylaxis (p = 0.01). Gametocytes were present in 121 (56%) of the episodes of malaria. Mosquito surveillance was carried out in response to 38 (31%) of these gametocytaemic episodes. Significant numbers of Anopheles farauti sensu lato mosquitoes were found close to the residence of a patient in 4 (11%) of these episodes. Only two occasions when local transmission could have possibly occurred were recognised. We do not believe malaria poses an important threat to the health of the public in Far North Queensland. Nevertheless, it remains an important problem for those who travel abroad to malarious areas.
This paper provides a brief nontechnical overview of the use of remote sensing to achieve multiple objectives, focusing on mosquito management. It also shows how Geographic Information Systems, combined with remote sensing analysis, have the potential to assist in minimizing disease risk. Examples are used from subtropical Queensland, Australia, where the salt marsh mosquito, Aedes vigilax, and the freshwater species, Culex annulirostris, are vectors of human arbovirus diseases such as Ross River and Barmah Forest virus disease. Culex annulirostris is also implicated in the transmission of Japanese Encephalitis. Mapping the breeding habitats of the species facilitates assessment of the risk of contracting the diseases and also assists in control of the vectors. First, it considers a simple risk model that is applied to data for the city of Brisbane in southeast Queensland. This is then linked to computer-aided analysis of remotely sensed data to map potential ephemeral freshwater breeding sites of Cx. annulirostris. This has the potential to guide control at critical times, for example after heavy summer rainfall or when there is an outbreak of Ross River virus disease. Second, the use of color infrared aerial photography is used to identify the specific parts of the salt marsh in which larvae and eggs of Ae. vigilax are found. Finally, we explore novel ways to map the detailed pattern of water under mangrove forest canopy to identify where mosquitoes are breeding and as an aid to planning modification. For each we discuss the limitations and advantages and the possibilities for combining methods and/or using a single method for multiple objectives.
We report a patient with Plasmodium vivax malaria that was acquired in Cairns in October 1996. Rather than being "introduced" (i.e., derived from an imported case), we believe this is likely to have been a case of "airport malaria" (i.e., acquired from an infected mosquito imported in an aircraft). It is, to our knowledge, the first report of airport malaria in Australia.
In February 1996, vivax malaria was diagnosed in a man from a remote community in far north Queensland who had not visited a malarious area for the past 19 years. Microscopy and DNA studies of blood from other residents of the community did not identify a source of infection. It was suspected the infection was transmitted by mosquitoes from a neighbour who had been infected in Papua New Guinea, but whose blood was not available for DNA tests.
During the summer 1994 outbreak of epidemic polyarthritis in suburban Brisbane, 29,931 adult female mosquitoes were collected by octenol-CO2 light traps and tested for virus by species in pools of approximately 20 using an in situ enzyme-linked immunoassay. Overall, 63 isolations of Ross River (RR) virus were made from 7 different mosquito species, including 23 from freshwater-breeding Culex annulirostris Skuse, 13 from peridomestic Aedes notoscriptus (Skuse), 4 from Aedes procax (Skuse), 12 from the brackish water-breeding Aedes funereus (Theobald), 9 from saltmarsh Aedes vigilax (Skuse), and 1 each from Culex sitiens Wiedemann and Aedes alternans (Westwood). The RR virus minimum infection rate in mosquitoes ranged from 1.6 to 2.5/1,000 from March to June 1994. This study implicates freshwater and brackish water mosquitoes as important suburban vectors of RR virus and indicates the need for refocusing mosquito control priorities.
In northern Queensland, Australia, three experiments were conducted to determine the response of mosquitoes of the Anopheles farauti complex to CDC traps baited with four attractant combinations: octenol + CO2 and light; octenol and light; CO2 and light; or CO2 and octenol without light. A CDC-modified updraft light-trap was also trialled, but did not significantly enhance collections of An.farauti sensu lato. The combination of light, octenol and CO2 caught significantly more An.farauti s.l. (both An.farauti No.1 and No.2 sibling species) when compared to CO2 and light alone. Only small numbers of the An.farauti complex were captured when CDC traps were baited with octenol alone, i.e. no light or CO2.
Mosquitoes were collected using CO2 and octenol-baited light traps during an outbreak of Japanese encephalitis (JE) on Badu Island in the Torres Strait, Australia in April 1995. A total of 13,300 mosquitoes comprising 12 species were processed for virus isolation. Eight isolates of JE virus were obtained from Culex annulirostris, with a carriage rate of 2.97:1,000; this mosquito also yielded one Sindbis virus isolate. A reverse transcriptase-polymerase chain reaction was used to sequence the JE viruses, which were compared with published sequences. The eight isolates were 90% homologous with known JE strains but only 68% homologous with other flaviviruses. Among the isolates, 99% homology was obtained, suggesting a common point of origin.