Biomedical subjects

B H Kay

Publications and source records attributed to B H Kay.

At least 37 records · Page 2Linked to original sources

PubMed2000

Toxicity of insecticides for control of freshwater Culex annulirostris (Diptera: Culicidae) to the nontarget shrimp, Caradina indistincta (Decapoda: Atyidae).

Laboratory evaluations were conducted in southeastern Queensland, Australia, to determine the toxicities of two organophosphate compounds (temephos and pirimiphos-methyl), an insect growth regulator (s-methoprene), and an entomopathogenic bacterium (Bacillus thuringiensis variety israelensis de Barjac [B.t.i.]) to Culex annulirostris (Skuse), an Australian freshwater mosquito vector of arboviruses, and to Caradina indistincta Calman, a co-habiting nontarget shrimp species. S-methoprene and B.t.i. were safest for Cx. annulirostris control with lethal dose ratios (LC95 nontarget/LC95 target) of 3,300 and 846,000, respectively. In contrast, lethal dose ratios for temephos and pirimiphos-methyl were 0.05 and 0.00005, respectively, suggesting that they are environmentally unsuitable. Based on their high lethal dose ratios, s-methoprene and B.t.i. are recommended for control of larval Cx. annulirostris in Australian freshwater habitats.

Animals↗

PubMed2000

Definition of Ross River virus vectors at Maroochy Shire, Australia.

Evidence of Ross River (RR) virus infection in field-collected mosquitoes and data from laboratory vector competence experiments incriminated a range of mosquito species as important vectors of RR virus in Maroochy Shire, Queensland, Australia. Nine RR and 2 Barmah Forest virus isolates were recovered from 27,529 mosquitoes collected in light traps from Maroochy Shire during 1996. Nine of the 10 most abundant mosquito species collected in light traps were fed on blood containing the B94/20 strain RR isolated from Queensland in 1994. All species except for Culex sitiens Wiedemann were susceptible to experimental infection. Evidence of RR virus transmission to mice was found with Aedes vigilax (Skuse), Aedes funereus (Theobald), Aedes procax (Skuse), Culex annulirostris Skuse, Mansonia uniformis (Theobald) and Culex australicus Dobrotworsky & Drummond. Aedes notoscriptus (Skuse) and Aedes multiplex (Theobald) were susceptible to RR virus infection, although there was no evidence of virus transmission. Based on adult abundance and vector competence results, freshwater species such as Cx. annulirostris, Ae. procax, and Ae. funereus, and saltmarsh Ae. vigilax, appear to be important vectors of RR virus in Maroochy Shire and control programs should be revised to include these species.

Aedes↗

PubMed2000

Vector competence of Aedes aegypti, Culex sitiens, Culex annulirostris, and Culex quinquefasciatus (Diptera: Culicidae) for Barmah Forest virus.

Aedes aegypti (L.), Culex sitiens Weidemann, Culex annulirostris Skuse, and Culex quinquefasciatus Say mosquitoes colonized at the Queensland Institute of Medical Research, Brisbane Australia, were fed on blood containing Barmah Forest virus (BF). Only Cx. annulirostris was susceptible to infection, with a median cell culture infectious dose (CCID50) of 10(3.36) per mosquito. Ae. aegypti and Cx. quinquefasciatus were infected experimentally, but at rates of < 9%. Cx. sitiens did not become infected. Infection rates for Cx. annulirostris fed 10(3.5) CCID50 of virus per mosquito, varied from 9 to 50% between 2 and 13 d after infection. Virus transmission to suckling mice by Cx. annulirostris occurred from 2 d after infection. Transmission of BF virus by Cx. annulirostris was 10% at 2 d after infection and did not exceed 8% thereafter. Although Cx. annulirostris may be infected and is able to transmit BF virus to suckling mice, it is nonetheless a relatively inefficient vector of the virus.

Aedes↗

PubMed2000

Definition of species in the Culex sitiens subgroup (Diptera: Culicidae) from Papua New Guinea and Australia.

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.

Alleles↗

PubMed2000

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.

Aedes↗

PubMed2000

The importance of subterranean mosquito habitat to arbovirus vector control strategies in north Queensland, Australia.

In north Queensland, 14 localities were surveyed for mosquito larvae (third and fourth instar) during summer/autumn and winter from 1996 to 1999. Absolute population numbers in subterranean habitats, mainly service manholes and pits (97%) but also some wells, septic tanks, storm drains, and sumps, were expressed as a proportion of total numbers in these sites plus surface sites within a 100-m radius. When correction factors were applied to subterranean samples, the 472,477 larvae mainly of Aedes tremulus (Theobald) group, Aedes notoscriptus (Skuse), and Aedes aegypti (L.) comprised 78% of the total population. In relation to the proportion of the overall immature mosquito population from subterranean habitats (propsub), linear regression coefficients for minimum temperature, relative humidity, and Mesocyclops copepod prevalence were significant for winter data; but for summer, only relative humidity was significant. Linear regression coefficients for Mesocyclops prevalence approached significance (P = 0.061) in summer. When multiple linear regression was used to model propsub, 68% of the variation was accounted for by relative humidity and the prevalence of Mesocyclops. In the drier and cooler towns, increased use of subterranean sites during winter was caused by reduced availability of surface oviposition sites because of the dry season. In the wetter coastal towns, no such restrictions applied and ambient conditions remained more equitable all year round. Mesocyclops were surprisingly common, particularly in these coastal towns. Release of known numbers of Mesocyclops indicated that 3-sweep netting in service manholes was sensitive down to densities of one Mesocyclops per 10 liters, and overall recovery varied from 1 to 4%. In relation to control, service manholes represent a stable habitat for mosquito (7% positive overall) and Mesocyclops populations. If they remained wet, service manholes positive for mosquito immatures or Mesocyclops during summer/autumn had 96% and 85% chance, respectively, of being positive the following winter. Even allowing for the effect of drying, a mosquito-positive manhole had a 79% chance of remaining positive the following winter. In view of the importance of these sites as refuges from adverse ambient conditions, it is proposed that a winter control strategy using Mesocyclops presents a cost-effective control option to reduce the recolonization of surface sites when conditions become more suitable.

Aedes↗

PubMed2000

National progress in dengue vector control in Vietnam: survey for Mesocyclops (Copepoda), Micronecta (Corixidae), and fish as biological control agents.

This paper describes the process of expanding a successful dengue control program in 3 provinces in northern Vietnam into a national one and demonstrates the presence of a rich, low-cost resource that could have similar applicability to other countries in the region. The cornerstone of the preventive strategy is larval control of Aedes aegypti (L.), the major vector, using predators such as copepods, Mesocyclops spp., aided by the corixid bug Micronecta quadristrigata Bredd, and fish in large water storage containers. From 1989 to 1998, 9 species of Mesocyclops (M. woutersi Van de Velde, M. aspericornis (Daday), M. ruttneri Kiefer, M. thermocyclopoides Harada, M. affinis Van de Velde, M. ogunnus Onabamiro, M. yenae Holynska, M. cf. pehpeiensis Hu, and M. dissimilis Defaye and Kawabata) were found in natural and artificial habitats in 26 provinces throughout Vietnam. The predatory capacities of 6 of these were evaluated in the laboratory. This indicated that daily consumption/killing averaged between 16 and 41 Ae. aegypti larvae per copepod. From detailed evaluations in 9 provinces, Mesocyclops spp. were surprisingly common in 8,413 artificial containers (concrete tanks, wells, ornamental ponds and in the south, large jars). Because of existing practices for washing and water transfer from ponds and lakes in Ha Tay and Ha Bac, Mesocyclops spp. already occurred in 60-100% of the water storage containers. When the relationship between the presence or absence of Mesocyclops and Aedes larvae in 5,111 containers was analyzed by the chi-square test, their distributions were significantly related, indicating control (odds ratio = 0.56). When 3,426 containers that did not contain Mesocyclops or fish were analyzed in relation to the distribution of Aedes larvae, those with Micronecta also had significantly less Aedes (odds ratio = 0.43). Therefore, this study demonstrates that there is an abundance of local Mesocyclops spp. in Vietnam that can be incorporated into specifically designed community-based control programs aided by Micronecta and fish.

Aedes↗

PubMed2000

Colonization and laboratory biology of Aedes notoscriptus from Brisbane, Australia.

Methods are described for the laboratory colonization of Aedes notoscriptus from Brisbane, Queensland, Australia. To initiate colonization, efforts were made to duplicate the natural environment of this species, including the use of a bromeliad as a swarm marker and oviposition substrate. The colony stabilized after the F8 with eclosion rates >50%, and an average production of 5,220 adults since the F9. The fecundity of Ae. notoscriptus averaged 29.4+/-10.5 eggs (range 14-57). The average development times from egg hatch to adult were 11 and 20 days under typical summer (20.5-28.9 degrees C) and winter (10.1-21.2 degrees C) conditions in Brisbane, respectively. This is the 1st published report of the colonization of Ae. notoscriptus.

Aedes↗

PubMed2000

A sticky entry-exit trap for sampling mosquitoes in subterranean habitats.

This paper addresses the problems of sampling adult Aedes aegypti and other mosquitoes which utilize subterranean habitats such as wells and service manholes. The sticky pipe trap is a simple device with an adhesive paper insert that can be clipped to the undersides of service manholes to record the entry and exit of adult mosquitoes through the keyhole openings. This trap was 1st used successfully in Townsville, Charters Towers, and Saunders Beach in north Queensland, Australia, in dry seasons of 1996-97 to record usage by 5 species, mainly the Aedes tremulus group and Ae. aegypti, which together comprised 91% of the 1,140 adults collected. Both males and predominantly nulliparous females were recorded exiting manholes, whereas all freshwater-breeding species entering manholes were gravid, presumably seeking oviposition sites.

Aedes↗

PubMed1999

Population structure and dispersal of the saltmarsh mosquito Aedes vigilax in Queensland, Australia.

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

Aedes↗

PubMed1999

Dissemination barriers to Ross River virus in Aedes vigilax and the effects of larval nutrition on their expression.

Effects of larval nutrition on vector competence of the mosquito Aedes vigilax (Skuse) (Diptera: Culicidae) from Townsville, north Queensland, for Ross River virus (RR) were examined. Larvae were reared on three different diets to create three significantly different size classes of adult mosquito. These were fed on serial dilutions of RR and then sampled on alternate days so the progression of the virus through the mosquito could be examined. No differences of vector competence could be attributed to larval nutrition. Barriers to infection and the correlation between infection rate, viral titre and transmission of RR by Ae. vigilax were also examined. The mesenteronal barrier was the only infection barrier expressed. No correlation between viral titre and transmission was detected, but a strong correlation was found between salivary gland infection and transmission rate. From this it was possible to estimate that 98.7+/-1.3% of Ae. vigilax with infected salivary glands transmit RR.

Aedes↗

PubMed1999

Experimental infection and transmission of Barmah Forest virus by Aedes vigilax (Diptera: Culicidae).

Aedes vigilax (Skuse) mosquitoes colonized from Townsville, Queensland, Australia, were fed on blood containing Barmah Forest virus (BF) isolated from the same species. The colony was susceptible to infection, with an ID50 of 10(2.6) CCID50 per mosquito. Infection and transmission rates for mosquitoes fed 10(3.5) CCID50 virus per mosquito varied from 58 to 100% and 36 to 100%, respectively, between days 3 and 13 after infection. Titers in infected mosquitoes were high by 5 d after infection and did not vary substantially thereafter. Virus transmission to suckling mice occurred from 3 d after infection. This work establishes that Ae. vigilax is a competent vector of BF.

Aedes↗

PubMed1999

Vector competence of Aedes notoscriptus (Diptera: Culicidae) for Barmah Forest virus and of this species and Aedes aegypti (Diptera: Culicidae) for dengue 1-4 viruses in Queensland, Australia.

Aedes notoscriptus (Skuse) mosquitoes colonized from Brisbane, Queensland, Australia, were fed on blood suspensions containing either Barmah Forest (BF) virus, dengue virus type 1 (DEN-1), dengue virus type 2 (DEN-2), dengue virus type 3 (DEN-3), or dengue virus type 4 (DEN-4). Ae. notoscriptus was shown to be moderately susceptible to oral infection with BF virus, ID50 = 10(3.3) CCID50 per mosquito, with titers in infected mosquitoes peaking 10 d after infection. BF virus transmission occurred between days 5 and 12, with an average rate of 45% (range, 40-50%). For DEN 1-4, Ae. notoscriptus showed low level susceptibility to oral infection, with maximum head and thorax squash infection rates of 8, 5, 13, and 3%, respectively. Rates of infection were notably higher in a north Queensland strain of Aedes aegypti (L.) used as a positive control, with maximum thorax squash infection rates of 58, 68, 78, and 60% for DEN 1-4, respectively. On the basis of these data, it is concluded that Ae. notoscriptus could act as an efficient vector of BF in urban environments, but it is unlikely to be an important vector of DEN.

Aedes↗

PubMed1999

Spatial and temporal analysis of Ross River virus disease patterns at Maroochy Shire, Australia: association between human morbidity and mosquito (Diptera: Culicidae) abundance.

Notifications of Ross River (RR) virus disease in Maroochy Shire were mapped according to the patient's place of residence, and standardized morbidity ratios were calculated for each of 11 census districts, with 4 areas having higher than average overall rates of RR virus disease notification. Temporal analysis of RR virus disease notifications from each of the 11 areas indicated that epidemics of RR virus disease either were widespread, resulting in higher than average numbers of cases from the majority of areas, or limited to only certain areas. Mosquitoes were collected in CO2 light traps, and the numbers analyzed to determine whether there was any association between mosquito abundance and disease incidence. Seasonal light trap indices for the fresh water-breeding Culex annulirostris Skuse and brackish water-breeding Aedes funereus (Theobald) were correlated positively with disease incidence. There was no apparent association between Aedes vigilax (Skuse) or Aedes procax (Skuse) light trap indices and disease incidence. Identification of human subpopulations with higher than average rates of RR virus disease, and the mosquito vectors associated with virus transmission, should provide a framework for the development of focused and therefore more effective control programs.

Aedes↗

PubMed1999

Calibrated funnel trap for quantifying mosquito (Diptera: Culicidae) abundance in wells.

Our article addresses the problems of sampling and quantifying the abundance of immature Aedes aegypti (L.) and other mosquitoes that use subterranean habitats such as wells and service manholes. Two versions of the funnel trap, Austrap and Vietrap, were extremely sensitive for detecting the presence of Ae. aegypti larvae in wells, and the modified version, the Vietrap, sampled on average 20.5% of 3rd and 4th instars when set overnight for 12 h. For both models, regression analyses between trap catch and absolute abundance indicated high coefficients of determination (R2 = 0.932 and 0.992) enabling accurate direct calibration. The effects of immature age, mosquito species, well diameter, and trap size on catch size were investigated. Because of its simplicity, efficacy, and inexpensiveness, the Vietrap will facilitate the comprehensive assessment of key larval habitats for Ae. aegypti, data critical for the development of effective control programs.

Animals↗

PubMed1999

Vector competence of mosquitoes (Diptera: Culicidae) from Maroochy Shire, Australia, for Barmah Forest virus.

Mosquitoes were collected in light traps from Maroochy Shire and fed on blood containing the sympatric BF1611 strain of Barmah Forest virus (BF). Saltmarsh Aedes vigilax (Skuse) and freshwater Aedes procax (Skuse) were highly susceptible to infection, with ID50s of 10(1.7) and 10(1.5) African green monkey kidney (Vero) cell culture infectious dose, 50% endpoint (CCID50) per mosquito, respectively, followed by Aedes multiplex (Theobald) and Aedes funereus (Theobald) with 10(2.5) and 10(3.2) CCID50 per mosquito, respectively. Culex australicus Dobrotworsky & Drummond and Mansonia uniformis (Theobald) that were fed 10(3.6) CCID50 (Vero) BF per mosquito had infection rates of 28 and 60%, respectively. Only 8% of freshwater Culex annulirostris Skuse fed the same viral dose were infected. Evidence of virus transmission to mice was found with Ae. vigilax and Ae. procax, with transmission rates of 65 and 88% at 11-12 d after infection, respectively. Based on adult abundance, susceptibility to infection, and efficiency of virus transmission, Ae. vigilax would appear to be the most important vector of BF in Maroochy Shire.

Aedes↗

PubMed1998

Identification of Australian arboviruses in inoculated cell cultures using monoclonal antibodies in ELISA.

An ELISA using a panel of specific monoclonal antibodies was developed to identify all alpha and flaviviruses isolated from mosquitoes caught throughout Australia. This technique is sensitive and rapid and is more specific than the traditional methods used to identify flaviviruses. The ability to identify unknown virus isolates from field-caught mosquitoes quickly and accurately improves the efficiency of arbovirus surveillance programs and allows health authorities to give an early warning of an increased health risk from a mosquito-borne virus in a particular region.

Aedes↗

PubMed1998

Vector competence of Aedes notoscriptus (Diptera: Culicidae) for Ross River virus in Queensland, Australia.

Aedes notoscriptus (Skuse) mosquitoes colonized from Brisbane, Queensland, Australia, were fed on blood containing Ross River (RR) virus isolated from Brisbane, Queensland, Australia. This colony was highly susceptible to infection, ID50 = 10(3.2) CCID50 per mosquito, with titers in infected mosquitoes peaking 9 d after infection. Transmission occurred between days 9 and 14, with a maximum rate of 13% between days 12 and 14 after infection. Considering the peridomestic abundance and human blood feeding habit of Ae. notoscriptus, positive transmission of RR virus indicates the need to consider this species more seriously in the context of urban RR transmission.

Aedes↗