Biomedical subjects

B H Kay

Publications and source records attributed to B H Kay.

At least 19 recordsLinked to original sources

PubMed1995

Aedes aegypti control in the Lao People's Democratic Republic, with reference to copepods.

An evaluation of the Lao Aedes aegypti control program and of the predatory abilities of copepods from Vientiane, Lao People's Democratic Republic was undertaken before a field release of copepods in Thongkankam village, Vientiane. Copepods were transported to Australia for evaluation of predatory abilities and their survival under various nutrient and pH conditions. Mesocyclops guangxiensis was chosen for release over M. aspericornis due to its higher reproduction rate and its ability to survive in lower nutrient environments. Mesocyclops guangxiensis was released into 142 containers and 20 wells in a village in Vientiane. Copepods were present in 7% of the containers after one month and were absent six months postinoculation. In comparison, 100% of wells were still positive after six months, with average numbers of Ae. aegypti in the wells decreasing from 59.5 +/- 18.5 (+/- SEM) to 0 after six months. Numbers of Culex quinquefasciatus and Anopheles maculatus also decreased to 0 after six months. This study indicates that predacious copepods will be accepted by the community and could be integrated as a low-cost, persistent control agent into new strategies for improving surveillance and control of dengue vectors.

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PubMed1995

Changes in mosquito populations with expansion of the Ross River Reservoir, Australia, from stage 1 to stage 2A.

Female mosquitoes were collected at 4 sites around the Ross River reservoir (Stage 2A) from 484 carbon dioxide-supplemented light traps. The seasonal abundance from these collections during 1991-93 was compared statistically with that for similar collections done for the Stage 1 reservoir in 1984-85. Principally due to clearing of the forest prior to the inundation of the Stage 2A, several tree hole/plant axil and shaded pool species are no longer present or are rare. Due to extensive loss of marginal emergent vegetation and creation of expanses of shallow muddy pools, mean number per trap of Anopheles amictus and Aedes normanensis increased up to 36- and 282-fold, respectively, from Stage 1 to 2A. For Culex annulirostris, mean abundance did not exceed densities recorded for Stage 1. However, from examination of trends from 1991 to 1993, mean catches of Culex, Anopheles spp., and Mansonia uniformis were increasing despite the progressive reduction of the inundated area of the reservoir. Cluster analysis of species abundance indicated broad similarities with Stage 1 data, and differences in faunal composition of the reservoir area compared with that around Townsville. In view of the continuing stabilization of the Stage 2A reservoir area, continued surveillance of major vector species is recommended.

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PubMed1995

Aedes albopictus and other Aedes (Stegomyia) species in Fiji.

During an assessment of the dengue situation in Fiji in early 1992, a house-to-house survey of container-breeding Aedes was made. Discarded tires and water drums were identified as key breeding sites for the 4 potential dengue vectors: Aedes aegypti, Aedes albopictus, Aedes pseudoscutellaris, and Aedes polynesiensis. Aedes albopictus were detected on Viti Levu, Vanua Levu, and on Taveuni. Examination of early records and of used tire importation suggests entry into Fiji after July 1985 but well before July 1988 when the species was first detected. It is also possible the Ae. albopictus was introduced via aircraft from Hawaii. In Suva, the 4 Stegomyia species coexist, but in Lautoka, it appears that Ae. albopictus may be displacing Ae. pseudoscutellaris.

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PubMed1994

Response of biting midges (Diptera: Ceratopogonidae) to carbon dioxide, octenol, and light in southeastern Queensland, Australia.

The effect of 1-octen-3-ol (octenol) on catches of estuarine biting midges in encephalitis vector surveillance (EVS) traps was examined in southeastern Queensland. Octenol by itself was not attractive but appeared to act as a synergist with CO2 to increase catches of most species. For four of six species tested, a medium (about 6 mg/h) release rate of octenol captured the most individuals. Addition of light also increased the catch size of most species. Octenol in combination with CO2 could be used to enhance biting midge catch size, improving the sensitivity of surveillance for midges and the pathogens they vector.

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PubMed1994

Differential responses of Aedes and Culex mosquitoes to octenol or light in combination with carbon dioxide in Queensland, Australia.

Field studies were conducted with EVS (encephalitis vector surveillance) traps in south-eastern Queensland, Australia, to determine the relative response rates of mosquitoes to three levels (0.1, 4.5 and 30 mg/h) of 1-octen-3-ol (octenol) in combination with a standard bait of 2200 g carbon dioxide (CO2), compared with CO2 alone or CO2 with light from a 6V incandescent bulb. Compared to CO2 alone, Aedes vigilax collections increased significantly when CO2 was supplemented by all three octenol emission levels, but not by the addition of light. Furthermore, the 4.5 and 30 mg/h release rate of octenol gave a significant increase in numbers of Ae.vigilax relative to that from CO2+light. In contrast, collections of Culex annulirostris and Culex sitiens were not enhanced significantly by either the addition of light or octenol at all three levels. Fewer Cx sitiens were collected with octenol released at 4.5 mg/h in comparison to CO2 alone. These differential sampling rates should be taken into account when using EVS traps.

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PubMed1994

Vaccines against arthropods.

The possibility of vaccinating hosts against blood-feeding arthropods using antigens derived from salivary gland, gut, and other tissues is reviewed. These vaccines directed against vector arthropods also have the potential to effect the arthropods capacity to transmit pathogens, and this is distinct from transmission-blocking vaccines that use antigens derived from pathogens. Antigen extracts have been used in attempts to vaccinate against fleas, lice, keds, flies, mosquitoes, and a number of tick species. A vaccine against the cattle tick, Boophilus microplus (Canestrini), using a recombinant antigen, has been tested under field conditions. Ticks feeding on vaccinated hosts are damaged by an immune response directed against their gut cells. Some die on the host, others engorge but their fecundity is reduced. The Commonwealth Scientific Industrial Research Organization-Biotechnology Australia tick vaccine against B. microplus is cited as a model for the development of other vaccines. It is suggested that the weaker effects of vaccines against insects as compared with ticks are related to the different structure and physiologies of the gut rather than being related to time spent on the vertebrate host. These differences in the effects of vaccines on insects may favor vaccines which block the passage of pathogens into vector insects. Vaccines against mosquitoes have been shown to reduce susceptibility of mosquitoes to arboviruses. The potential of the different vaccines is discussed.

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PubMed1994

Quantitative sampling of immature Aedes aegypti in metal drums using sweep net and dipping methods.

The behavior of aquatic stages of Aedes aegypti was evaluated in 200-liter metal drums to develop improved surveillance. When known numbers of larvae recovered with a rectangular net and with a standard dipper were compared, all stages except 1st instar were most numerous in the top 1/3 of the drum. Water temperature was the only significant variable affecting the vertical distribution of 4th-instar larvae; light intensity and pH were nonsignificant factors. Rust in the water was also thought to influence distribution towards the surface layer. When 100-400 immatures were released into a full drum, immatures were detected by sweeping and dipping the surface layer on 93.3 and 72.9% of trials, respectively. The correlation coefficients (r) of recoveries of known numbers of immatures by sweeping and dipping varied from 0.92 to 0.98 and from 0.38 to 0.89, respectively. The coefficients of variation were 2-5 times smaller for sweeping than for dipping. Recoveries from dipping were shown to be affected by the water volume in the drum. Counts of 4th-instar larvae from one sweep around the top are sufficient to assess productivity in drums.

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PubMed1994

Laboratory studies of desiccation resistance in Mesocyclops (Copepoda: Cyclopoida).

The desiccation resistance of 4 species of Mesocyclops from varied geographical locations was tested against water content in sediment, temperature, and photoperiod. Trays containing sediment were inoculated with copepods and allowed to dry out for a period of 2 months and then reflooded. Both copepodids and adults of all species tested displayed desiccation resistance, with water content having greatest effect on survival.

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PubMed1994

Intersectoral approaches to dengue vector control.

Medical entomology in the context of urban vector control, especially for dengue, can be likened to the tail of a dog. Vertically structured Aedes aegypti campaigns such as run by Gorgas and Soper earlier this century relied on sufficient legislative backing for vector control to ensure that the tail was capable of wagging the dog. Under these conditions, especially where individual rights do not intrude, vertical programs will be successful. The global expansion of dengue, dengue hemorrhagic fever and its vectors, plus growing trends towards urban/periurban living indicate a more serious scenario than at present. In 1987, the Brundtland Report: "Our Common Future" decried sectoralism in problem solving. Following the United Nations Conference on Environment and Development (UNCED) in 1992, the resulting Commission on Sustainable Development has promoted the intersectoral message of health, environment and development. The WHO/FAO/UNEP/UNCHS Panel of Experts on Environmental Management for Vector Control has promoted this for some time and is attempting to build multidisciplinary projects against urban vector borne disease. Adequate solid waste management and recycling will reduce numbers of water bearing containers infested with Aedes aegypti and provision of reliable piped water supplies will impact heavily on infested water storage containers. Both should be encouraged as viable control options. For much of the world, vertical programs have been reported as prohibitively expensive, and unacceptable intrusion on human rights and thus unsustainable in the modern economic context. However there are successful modern examples.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1993

Surveillance of mosquitoes and arbovirus infection at the Ross River Dam (Stage 1), Australia.

This paper describes the temporal and spatial abundance of the mosquito fauna of the Ross River Dam (Stage 1) in northern Queensland, Australia. Culex annulirostris, Anopheles annulipes s.l., Mansonia uniformis, Mansonia septempunctata, and the nondam breeding Aedes vigilax were the major species collected by dry ice-supplemented light traps set at various distances from the edge of the reservoir. To estimate the level of arbovirus activity in these different zones, sentinel chicken flocks were bled 4 times a year and their antibody conversion rates determined by the hemagglutination-inhibition test. Although mosquito abundance at sites close to the reservoir were 1.5-6.1 times higher than at the more distant sites, arbovirus conversion rates, particularly to the alphaviruses Ross River and Sindbis, varied according to zone and year, suggesting that risk of infection was no greater around the dam than elsewhere.

Aedes↗

PubMed1993

Response of mosquitoes to carbon dioxide and 1-octen-3-ol in southeast Queensland, Australia.

Encephalitis vector surveillance (EVS) traps were used to study the attractant effect of CO2 and 1-octen-3-ol (octenol) on mosquitoes at 2 different locations in southeast Queensland. Octenol alone was only slightly attractive for Aedes vigilax. There was a significant increase in the numbers of Ae. vigilax and Aedes funereus caught when octenol was added to CO2, although catches of Culex annulirostris and Culex sitiens did not change significantly. The size and age compositions of Ae. vigilax attracted by CO2 and by octenol were comparable. These data suggest that octenol should be considered as a supplement to CO2-baited EVS traps for mosquito-based arbovirus surveillance in southeast Queensland.

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PubMed1993

Comparison of sampling efficacy of sweeping and dipping for Aedes aegypti larvae in tires.

A sweep net with a flexible plastic frame was compared to a dipper for sampling efficacy for Aedes aegypti larvae in different-sized tires. When known numbers of mosquito larvae were introduced into tires, from 2 to 6.8 times more larvae were recovered by sweeping than by dipping. Sediment in the tires significantly reduced the recovery of larvae by both methods. Sampling efficacy was affected by water level and tire size. In relation to dipping, sweeping showed less variation in percentage recovery, higher sensitivity for detecting larvae and had better correlations with known numbers of larvae in tires. We conclude that sweeping is superior to dipping for sampling mosquito larvae in tires.

Aedes↗

PubMed1993

Runnelling to control saltmarsh mosquitoes: long-term efficacy and environmental impacts.

Aedes vigilax is a problem mosquito species prevalent in subtropical Australian coastal wetlands. We evaluate the long-term impacts of runnelling, an environmentally benign habitat modification method, on mosquitoes and the wetland environment. Runnelling uses shallow channels to enhance flushing of the marsh. The method successfully reduced larval numbers to below nuisance levels for the 6.5 year study period. We did not detect any significant difference in the wetland environment between runnelled and unmodified parts of the study area. However, the spatial extent of the effects may have extended beyond the modified area.

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PubMed1992

Aedes aegypti (Diptera: Culicidae) vision: spectral sensitivity and other perceptual parameters of the female eye.

From measurements of the mean ommatidial diameter (17.2 microns) and mean interommatidial angle (6.2 degrees) of the eye of female Ae. aegypti (L.), a minimum resolvable angle of 12.3 degrees and an eye parameter of 1.6 microns were calculated. The eye had relatively poor acuity but high overall sensitivity to light. Electroretinographs revealed spectral sensitivity ranging from ultraviolet (323 nm) to orange-red (621 nm), with sensitivity peaks in the ultraviolet (lambda max323-345 nm) and green (lambda max523 nm) wavelengths. The retina is capable of some wavelength discrimination.

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PubMed1992

Aedes aegypti (Diptera: Culicidae) vision: response to stimuli from the optical environment.

Although Aedes aegypti (L.) are capable of some wavelength discrimination, behavioral experiments demonstrated that color was not a stimulus to which they responded. Optical stimuli that did affect Ae. aegypti behavior were luminous reflectance, vertical contrast, and movement. Stationary objects of low reflectance and solid color were the most attractive to males and females.

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PubMed1992

Release of Mesocyclops aspericornis (Copepoda) for control of larval Aedes polynesiensis (Diptera: Culicidae) in land crab burrows on an atoll of French Polynesia.

On Tereia Island, Rangiroa Atoll, 14,321 land crab burrows were treated with the copepod Mesocyclops aspericornis from January to June 1986, to control larvae of Aedes polynesiensis marks. In October 1987, the entire island of Tereia was retreated (17,300 burrows), and the neighboring island, Voisin, was left untreated as a control. From 5 to 15 mo after treatment, burrows with M. aspericornis contained an average of 2 Ae. polynesiensis immatures compared with 97 immatures from untreated burrows. Long-term larval control was successful in low-lying areas where burrows remained wet or were reflooded. Although there may have been other contributing factors, the major reason for lack of persistence of M. aspericornis in burrows over the entire island appeared to be poor resistance to desiccation. From all treated burrows in October 1987, M. aspericornis subsequently was found in 89.5, 39.1, and 24.1% of burrows sampled 5, 8, and 15 mo after treatment, respectively. The broad-scale results for Tereia indicated that there was no reduction of adult biting indices when compared with Voisin. Mark-release experiments on four occasions indicated that Ae. polynesiensis had a limited flight range and that the probability for interisland movement was low.

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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.

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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.

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