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Biomedical subjects

B H Kay

Publications and source records attributed to B H Kay.

At least 91 records · Page 5Linked to original sources
PubMed1992

Laboratory evaluation of Brazilian Mesocyclops (Copepoda: Cyclopidae) for mosquito control.

In laboratory tests, four different strains of Mesocyclops aspericornis (Daday) collected in or near Fortaleza, Brazil, showed potential as biological control agents of Aedes aegypti (L.) mosquito larvae but were not as effective against Anopheles or Culex. In contrast, the larger M. longisetus (Thiebaud), collected at Fortaleza, killed 100% of Ae. aegypti and Anopheles farauti (Laveran) (No. 1) at larval densities of 200/liter and Culex quinquefasciatus (Say) at 25/liter. In cage simulations with Ae. aegypti and Mesocyclops, both copepod species eliminated all immatures in earthenware pots by week 3. Owing to the lack of replacement, all Ae. aegypti adults subsequently died by week 8 or 9. Although both M. longisetus and M. aspericornis showed maximum reproductive potential at 25 degrees C, breeding occurred from 20 to 35 degrees C. Based on these laboratory evaluations, M. longisetus has been selected for field trials in rural villages in Ceará to control Ae. aegypti.

Aedes↗
PubMed1992

Evaluation of a funnel trap for collecting copepods and immature mosquitoes from wells.

A simple funnel trap which inverts on entry to and exit from the water, was evaluated with respect to sampling the aquatic fauna of wells in and around Fortaleza, Brazil. Mosquito larvae, copepods, ostracods, fish and tadpoles were collected. When known numbers of Culex quinquefasciatus larvae and Mesocyclops aspericornis copepods were introduced into negative wells, overnight sampling resulted in 50% positivity of traps when 10 larvae (1/1,000 cm2) and 25 copepods (1/176 liters) were introduced. All traps were positive when 100 and 400 larve and copepods, respectively, were present. Over a range of 10-2,000 and 25-800 released larvae and copepods, respectively, average recovery rates were 6.1 and 3.6%, but on the basis of one sample, the variability was such that a precise estimate of absolute abundance could not be made.

Animals↗
PubMed1991

Monoclonal antibodies to Kunjin and Kokobera viruses.

Five monoclonal antibodies (MoAb) were produced to the envelope (E) protein of Kunjin (KUN) virus. Three of these were specific for the KUN/West Nile complex, and two reacted with epitopes that were common to the flavivirus family. These MoAb defined at least four distinct epitopes on the E protein of KUN virus. Eight MoAb were also produced to unidentified proteins of Kokobera (KOK) virus. Seven were specific for KOK, while the remaining antibody cross-reacted with Stratford virus and an unregistered flavivirus CS946. The application of these MoAb to arboviral surveillance is discussed.

Animals↗
PubMed1991

Evaluation of Australian Mesocyclops (Cyclopoida: Cyclopidae) for mosquito control.

Six of seven species of Mesocyclops copepods, collected from northeastern Australia, showed potential as biological control agents of Aedes mosquitoes. Methods of laboratory evaluation included predation trials at different larval mosquito densities, population growth rates at different temperatures, and laboratory cage simulations. The predation efficacy of Mesocyclops aspericornis, M. australiensis, and M. mb1 from southern Queensland, and M. darwini, M. mb2, M. notius and M. mb3 from northern Queensland were compared with M. aspericornis (used successfully in French Polynesia) against laboratory populations of Aedes aegypti (L.), Culex quinquefasciatus Say, and Anopheles farauti Laveran (No. 1). M. aspericornis (L. Kurwongbah) proved to be the most effective Queensland predator and exhibited an elevated reproductive rate at 20-25 degrees C. M. darwini was less efficient as a predator but was more fecund at 25-35 degrees C. Based on these evaluations, M. aspericornis (L. Kurwongbah) has been selected for small-scale field trials in Queensland.

Aedes↗
PubMed1991

Comparison of dry ice baited light traps with human bait collections for surveillance of mosquitoes in northern Queensland, Australia.

Adult mosquitoes were collected from April 1984 to September 1985, at 3 sites at or adjacent to the Ross River Dam, north Queensland. The numbers attracted to dry ice baited encephalitis virus surveillance (EVS) light traps and to human bait were similar. Both methods sampled 18 taxa and ranked the abundances of Culex annulirostris, Anopheles annulipes s.l., Aedes vigilax, Mansonia uniformis and Ma. septempunctata similarly at each locality. Significant correlations between the 2 methods were found for all 5 of the dominant species, but were stronger for Ae. vigilax, Ma. uniformis and Ma. septempunctata than for Cx. annulirostris or An. annulipes. Human bait attracted more Cx. annulirostris, Ae. vigilax and Ma. uniformis than the EVS traps. The relative effectiveness of the 2 methods varied significantly with time for Cx. annulirostris and An. annulipes, but both methods revealed similar long term population trends. These data suggest that EVS surveillance may be better suited for sampling Ae. vigilax, and human bait (or alternatively animal bait) or a combination of both methods would be more appropriate for sampling Cx. annulirostris at the dam.

Aedes↗
PubMed1990

Is Aedes albopictus in Australia?

In Brisbane during October 1988 one larva of the exotic dengue vector Aedes albopictus (Skuse) was collected by quarantine officers from a consignment of used vehicle tyres imported from Asia. Although this is not the first report of this mosquito in Australia, the finding was of sufficient importance to change quarantine procedures. Subsequently in Darwin during June 1989, two Ae. albopictus larvae were recovered from an ovitrap located near the wharves. This article reviews the global expansion of this species and, on the basis of previous imports of tyres into Australia, suggests that Ae. albopictus may already be established in this country.

Aedes↗
PubMed1990

Epitope analysis of the envelope and non-structural glycoproteins of Murray Valley encephalitis virus.

Previous studies have shown that antibodies produced against strategic flavivirus epitopes play an important role in recovery and immunity. Definition of the conformation and location of these epitopes and the degree of their conservation among flaviviruses is important to understanding the humoral response to flavivirus infection. In this study we have examined epitopes recognized by 14 monoclonal antibodies (MAbs) produced to the envelope (E) and non-structural (NS1) proteins of Murray Valley encephalitis virus (MVE). These antibodies were analysed for specificity, neutralization, haemagglutination inhibition (HI) and competitive binding. We have identified six distinct epitopes on the E protein which are located in four non-overlapping domains. MAbs to epitopes in one domain neutralized virus, were specific for MVE and Japanese encephalitis virus, and reacted with epitopes resistant to reduction. Two other E domains, one specific to MVE and the other shared by all flaviviruses, also contained neutralization sites and were stabilized by disulphide bonds. The fourth domain on E was conserved among the flaviviruses, sensitive to SDS denaturation and did not induce neutralizing antibody. Studies with MVE NS1 MAbs revealed that they were mostly type-specific, unreactive with conserved epitopes, and unreactive in HI and neutralization tests. The six epitopes identified on NS1 did not overlap and represent antigenic domains either resistant or sensitive to reduction. Immunoblotting of viral proteins in MVE-infected C6/36 cells revealed two distinct forms of NS1 and high Mr proteins of 97K and 108K that represented disulphide-linked heterodimers of E and NS1.

Animals↗
PubMed1990

Anti-mosquito antibodies reduce the susceptibility of Aedes aegypti to arbovirus infection.

Aedes aegypti (L.) mosquitoes showed a significant reduction in susceptibility to infection with Ross River virus and Murray Valley encephalitis virus when they were fed on a blood-virus mixture containing rabbit antibodies to mosquito midgut components. Presence of the antibodies did not demonstrably affect virus titres in infected mosquitoes, nor the transmission of virus from infected mosquitoes to vertebrates.

Aedes↗
PubMed1989

Larval diet and the vector competence of Culex annulirostris (Diptera: Culicidae) for Murray Valley encephalitis virus.

Culex annulirostris Skuse larvae were reared on two different amounts of powdered dog chow and yeast, low intake (2.8 micrograms/larva) and high intake (8.4 micrograms/larva), to produce adults with mean wing lengths of 3.25 and 3.7 mm, respectively. The resulting adults were fed different dosages of Murray Valley encephalitis virus and after 10 d extrinsic incubation at 28 degrees C, the infection rate, transmission rate, salivary gland, and body titers were determined. There were no significant differences in any of these parameters.

Animals↗
PubMed1989

Rearing temperature influences flavivirus vector competence of mosquitoes.

Culex annulirostris Skuse mosquitoes (Brisbane strain) were reared at 20 degrees C or 27 degrees C and the adult females were experimentally infected by feeding Murray Valley encephalitis virus (MVE). They were then maintained (a) in the insectary at 20 degrees C, after rearing at either 20 degrees C or 27 degrees C; (b) at ambient outdoor temperatures, range 12.2-28.9 degrees C, mean 19.6 degrees C; or (c) at 27 degrees C after rearing at 27 degrees C. There was no significant difference in rates of MVE infection or transmission when mosquitoes were reared and maintained constantly at 20 degrees C or 27 degrees C. However, for females kept at reduced temperature (i.e. mean = 19.6 degrees C or 20 degrees C after rearing at 27 degrees C), the infection and transmission rates of MVE were significantly reduced (2 x 8 replicates). This investigation illustrates that vector competence is depressed by decreasing temperatures for adult mosquitoes compared with those they experienced during development. Similar patterns were evident with previously published work on Japanese and St Louis encephalitis, dengue and yellow fever. The process appears to be reversible, i.e. increased temperature raises virus infection and transmission rates. It is concluded that, without incubation at warmer temperatures, flavivirus recovery from overwintering mosquitoes will be negatively biased.

Animals↗
PubMed1989

The vector competence of Culex annulirostris, Aedes sagax and Aedes alboannulatus for Murray Valley encephalitis virus at different temperatures.

Culex annulirostris Skuse, colonized from Brisbane, Queensland, and Mildura, Victoria, Australia, were effective vectors of Murray Valley encephalitis virus at 20, 27 and 32-35 degrees C with full extrinsic incubation periods of 15, 10 and 4 days respectively. At 20 degrees C, 7-11 days post-infection, transmission by the Mildura colony (0-20%) was less efficient than the Brisbane colony (30-70%) but both were capable of 75-100% transmission after longer extrinsic incubation periods. Discriminant analysis of body and salivary gland titres showed that these were not satisfactory indicators of transmission. Wild-caught Aedes sagax (Skuse) and Cx annulirostris from the Murray Valley showed equal competence, but Aedes alboannulatus (Macquart) was a poor vector. The results provide data on rural amplification of Murray Valley encephalitis virus during spring and suggest that further work on the potential of Ae. sagax as a natural vector is warranted.

Aedes↗
PubMed1989

The runnelling method of habitat modification: an environment-focused tool for salt marsh mosquito management.

Traditional methods of managing salt marsh mosquitoes focus primarily on maximizing the reduction of mosquito populations, with minimizing environmental impact as a secondary consideration. An environment-oriented approach to salt marsh management for mosquito control, runnelling, is described and compared with other forms of habitat modification such as ditching and Open Marsh Water Management (OMWM). Runnelling alters the salt marsh as little as possible while causing significant reductions in mosquito numbers. The effect of runnelling on the environment was monitored via the following variables: water table level, substrate characteristics (moisture, salinity and pH), vegetation (height and density of each Sporobolus virginicus) and the numbers of mosquito larvae. Runnelling had a statistically significant effect on only two of the seven variables. These were the height of Sporobolus, which increased near runnels, and the number of mosquito larvae, which decreased. The main difference between ditching, OMWM and runnelling lies in the magnitude of the habitat modification. Ditching involves the greatest alteration to the marsh, and runnelling the least. Consequently, runnelling has a smaller effect on the estuarine environment as a whole than does either ditching or OMWM.

Animals↗
PubMed1988

Isolation and characterization of dengue viruses serotype 1 from an epidemic in northern Queensland, Australia.

Thirteen strains of dengue type 1 were isolated from the lymphocyte fractions of 69 acute phase blood samples collected at Thursday Island Hospital during 1981 and 1982. One further strain of type 1 was isolated from 7 blood samples despatched by air from Cairns Base Hospital during 1982. Four of these Australian isolates representing the beginning, middle, and end of the epidemic were examined by restriction enzyme mapping and were found to be identical for the nine restriction enzymes used. The maps differed from those derived from two Malaysian dengue type 1 strains isolated during the epidemic of 1981-82 in that country. This suggests reliance on serological typing to establish global circulation patterns of epidemic dengue is insufficient and that more specific methods such as genome mapping are useful.

Adolescent↗
PubMed1988

Type-specific monoclonal antibodies produced to proteins of Murray Valley encephalitis virus.

Two monoclonal antibodies have been produced to the flavivirus, Murray Valley encephalitis (MVE). Immunofluorescent antibody and ELISA tests revealed that one antibody was specific for MVE while the other cross-reacted weakly with Alfuy and Kunjin viruses. These antibodies have neither haemagglutination inhibition nor neutralising activity. One of the monoclonal antibodies reacted with the envelope glycoprotein (E) and a 45,000 MW protein, while the other reacted with a protein of 23,000 daltons. Competitive binding assays confirmed that these antibodies reacted with unrelated epitopes.

Antibodies, Monoclonal↗
PubMed1988

Anti-mosquito antibodies decrease the reproductive capacity of Aedes aegypti.

Aedes aegypti (L.) fed on rabbits immunized with mosquito antigens showed a reduction in fecundity in the first oviposition and decreased viability of the progeny. Feeding behaviour of mosquitoes was not affected and no significant mortality was observed due to the presence of anti-mosquito antibodies in the bloodmeal. Antibodies were detected in the oocytes of mosquitoes 48 h after the bloodmeal. The role of specific antibodies in influencing fecundity is discussed.

Aedes↗
PubMed1987

An enzyme immunoassay to detect Australian flaviviruses and identify the encephalitic subgroup using monoclonal antibodies.

An antigen-capture enzyme-linked immunosorbent assay (ELISA) has been developed to detect antigens of Australian flaviviruses in mosquito pools, suckling mouse brain and infected cell culture supernatant fluid. A monoclonal antibody reactive to an epitope on the envelope glycoprotein common to all flaviviruses was used as the capture antibody. Purified rabbit IgG, produced against Murray Valley encephalitis (MVE) virus, which reacted with eight Australian flaviviruses in haemagglutination inhibition (HI) and in an indirect fluorescent antibody test, was used as the indicator antibody in direct and indirect antigen-capture ELISA. A monoclonal antibody specific for a subgroup of encephalitic flaviviruses was conjugated to horseradish peroxidase and used as the indicator antibody to distinguish MVE, Kunjin and Alfuy viruses from the remainder tested. This ELISA could detect viral antigen in mosquito cell culture fluids and suckling mouse brain preparations at titres as low as 1000 TCID50/100 microliters. Viral antigen in a single mosquito infected with MVE could be detected in a pool of 500.

Animals↗