Publications (14)22.76 Total impact
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Article: Influence of Orientia tsutsugamushi infection on the developmental biology of Leptotrombidium imphalum and Leptotrombidium chiangraiensis (Acari: Trombiculidae).
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ABSTRACT: Leptotrombidium chiangraiensis Tanskul & Linthicum, and Leptotrombidium imphalum Vercammen-Grandjean are important vectors of scrub typhus in rice field habitats in northern Thailand. The developmental biology of all stages of the life cycle of two generations of these species of mites infected with Orientia tsutsugamushi (Hayashi) and uninfected mites is reported. The development of the infected lines of both F1 and F2 L. chiangraiensis were significantly longer than their respective uninfected lines (P < 0.05). The developmental times of uninfected and infected F1 lines of L. imphalum were not significantly different; however, F2 infected lines took significantly longer to develop (P < 0.05). Both F1 and F2 generations of infected L. imphalum and L. chiangraiensis oviposited on average >150 fewer eggs than uninfected mites.Journal of Medical Entomology 11/2012; 49(6):1270-5. · 1.76 Impact Factor -
Article: Laboratory evaluation of the response of Aedes aegypti and Aedes albopictus uninfected and infected with dengue virus to deet.
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ABSTRACT: Laboratory studies were conducted to compare the response of Aedes aegypti (L.) and Aedes albopictus (Skuse) adults, uninfected and infected with four serotypes of dengue virus to a repellent containing 5% N, N-diethyl-3-methylbenzamide (deet). The results showed that mosquitoes infected with the four serotypes of dengue responded similarly to uninfected mosquitoes.Journal of Medical Entomology 03/2011; 48(2):334-6. · 1.76 Impact Factor -
Article: Malaria vectors of Timor-Leste.
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ABSTRACT: The island of Timor lies at the south-eastern edge of Indonesia on the boundary of the Oriental and Australian faunal regions. The country of Timor-Leste, which occupies the eastern part of the island, is malarious, but anopheline faunal surveys and malaria vector incrimination date back to the 1960 s. Over the last decade the malaria vectors of south-east Asia and the south-west Pacific have been intensely studied using molecular techniques that can confirm identification within complexes of isomorphic species. The aim of this study is to accurately identify the Anopheles fauna of Timor-Leste using these techniques. The survey was carried out over the period February to June 2001. Standard entomological techniques--human landing collections, larval collections and CO2 baited light traps--were used to collect anophelines from the main geographical regions: coastal plains, inland plains, and highlands. Specimens were processed for identification by morphology and genotyped for the ribosomal DNA ITS2 by restriction analysis and/or DNA sequencing. Phylogenetic relationship of Anopheles sundaicus and Anopheles subpictus individuals was also assessed using DNA sequences from the ITS2 and mitochondrial cytochrome-b. All specimens, other than those from larval surveys, were processed to detect the presence of the Plasmodium parasite circumsporozoite protein by ELISA for vector incrimination. Of 2,030 specimens collected, seven species were identified by morphology: Anopheles barbirostris, Anopheles aconitus, Anopheles annularis, Anopheles maculatus, Anopheles peditaeniatus, An. sundaicus and Anopheles vagus. These were confirmed by molecular analysis with the addition of Anopheles flavirostris and an unidentified species designated here as An. vagus genotype B. This latter species was morphologically similar to An. vagus and An. subpictus and is likely to be the An. subpictus described by other workers for Timor. However, genetically this species showed strong affinities to the An. sundaicus complex. Anopheles vagus was the most common species but was rarely collected coming to bite humans; An. barbirostris and An. vagus genotype B were the two most common species collected in human landing catches and both were found positive for CS protein. The anopheline fauna of Timor-Leste is of Oriental origin with no evidence of elements from the Australian Region. The existence of species complexes will make the use of morphological markers problematic in the country. Using molecular analysis a number of issues regarding the anopheline fauna of Timor-Leste were resolved and nine putative species of Anopheles were identified; two species: An. barbirostris and An. vagus genotype B, were incriminated as malaria vectors.Malaria Journal 01/2010; 9:40. · 3.19 Impact Factor -
Article: Transstadial and transovarial transmission of Orientia tsutsugamushi in Leptotrombidium imphalum and Leptotrombidium chiangraiensis (Acari: Trombiculidae).
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ABSTRACT: Transovarial transmission of Orientia tsutsugamushi (Hayashi) in laboratory colonies of Leptotrombidium chiangraiensis Tanskul & Linthicum and Leptotrombidium imphalum (Vercammen-Grandjean & Langston) (Acari: Trombiculidae) was studied for two generations. In L. chiangraiensis, the transovarial and filial infection rate was 100% in each generation. Only infected females were produced. In L. imphalum, the transovarial infection rate of the parental generation was 100% but declined to 93.3% in the F1 generation. The overall filial infection rate was 100% in the F1 but was only 62.3% in the F2 generation. In infected lines, only infected females were produced in the F1 generation, but 1.5% of the F2 progeny were infected males. Lower rates of transovarial transmission in L. imphalum may be the cause of the lower natural infection rates found in nature.Journal of Medical Entomology 11/2009; 46(6):1442-5. · 1.76 Impact Factor -
Article: Vector competence of Australian Culex gelidus Theobald (Diptera: Culicidae) for endemic and exotic arboviruses
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ABSTRACT: The recent recognition of established populations of the mosquito, Culex gelidus Theobald, in Australia has raised concerns about local transmission of arboviruses. The vector competence of a mainland population of Cx. gelidus was investigated for two local alphaviruses, Ross River (RRV) and Barmah Forest (BFV) viruses, and three flaviviruses, Japanese encephalitis (JEV), Kunjin (KUNV) and Murray Valley encephalitis (MVEV) viruses. Colonised mosquitoes were exposed to virus via blood-soaked pledgets and transmission was tested using a capillary-tube method. The important Australian vectors, Aedes vigilax (Skuse) and Culex annulirostris Skuse, were used as internal controls for the alphaviruses and flaviviruses, respectively. Overall, Cx. gelidus was a more efficient vector of flaviviruses than alphaviruses. Culex gelidus was refractory to infection with BFV, and nearly 25% transmitted RRV, which was comparable to Ae. vigilax. Culex gelidus was susceptible to all three flaviviruses, with transmission rates of 96%, 95% and 41% for JEV, KUNV and MVEV, respectively. JEV transmission rates in Cx. annulirostris were unexpectedly low and this was possibly due to differences in susceptibility to JEV genotypes I and II. Considering the high susceptibility to the flaviviruses demonstrated here, and the natural infections with RRV and JEV that have been detected from northern Australian populations, the establishment of the exotic mosquito, Cx. gelidus, in Australia is potentially a significant public health concern.Australian Journal of Entomology 08/2009; 48(3):234 - 240. · 0.97 Impact Factor -
Article: Laboratory and field evaluation of SS220 and deet against mosquitoes in Queensland, Australia.
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ABSTRACT: Laboratory and field efficacy trials comparing deet (N,N-diethyl-3-methylbenzamide) and SS220 [(IS, 2'S)-2-methylpiperindinyl-3-cyclohexen-1-carboxamide] against mosquitoes in Queensland, Australia, were conducted. In the laboratory, both compounds provided between 150 and 195 min of protection against Aedes aegypti and between 18 and 80 min of protection against Anopheles farauti. In laboratory tests against Culex annulirostris, 20% SS220 provided 3 h of protection and 20% deet provided >6 h of protection. A field efficacy test was conducted at Redcliffe, Queensland in January 2008 and the predominant mosquito species collected was Cx. annulirostris (84.4% of collection). In the field, 20% SS220 provided significantly better protection against mosquitoes than 20% deet. Seven hours after application, SS220 provided greater than 96.0% protection against all mosquitoes, whereas 20% deet provided 58.9% protection.Journal of the American Mosquito Control Association 06/2009; 25(2):174-8. · 0.91 Impact Factor -
Article: Seroconversion to filarial antigens in Australian defence force personnel in Timor-Leste.
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ABSTRACT: To investigate whether Australian soldiers were exposed to filarial parasites that cause lymphatic filariasis during a 6-month deployment to Timor-Leste, antifilarial antibody levels were measured in 907 soldiers using an enzyme linked immunosorbent assay (ELISA). Initial testing using Dirofilaria immitis antigen demonstrated that 49 of 907 (5.4%) soldiers developed antifilarial antibodies of the IgG1 subclass after deployment, whereas 1 of 944 (0.1%) seroconverted to the IgG4 subclass. When a sub sample of 88 D. immitis-reactive sera was subject to testing with an antifilarial antibody test using Brugia malayi antigen, 46 had elevated IgG antibodies, whereas 5 had elevated antibodies of the IgG4 subclass. A total of 24 soldiers seroconverted to B. malayi, as measured by parasite-specific IgG, whereas 1 seroconverted to IgG4. The relatively low number of seroconversions indicates a low but measurable risk of exposure to human filarial parasites among Australian soldiers deployed to Timor-Leste. However, to reduce the risk of exposure to these parasites, soldiers deploying to endemic areas should practice strict adherence to personal protective measures against mosquito bites.The American journal of tropical medicine and hygiene 05/2008; 78(4):560-3. · 2.59 Impact Factor -
Article: Expectoration of Flaviviruses during sugar feeding by mosquitoes (Diptera: Culicidae).
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ABSTRACT: Biological transmission of arboviruses to a vertebrate host occurs when virions are expelled along with saliva during blood feeding by a hematophagous arthropod. We undertook experiments to determine whether mosquitoes expectorate flaviviruses in their saliva while sugar feeding. Batches of Culex annulirostris Skuse and Culex gelidus Theobald (Diptera: Culicidae) were orally infected with Japanese encephalitis (family Flaviviridae, genus Flavivirus, JEV), Kunjin (family Flaviviridae, genus Flavivirus, KUNV; a subtype of West Nile virus), and Murray Valley encephalitis (family Flaviviridae, genus Flavivirus, MVEV) viruses. After a 7-d extrinsic incubation, these mosquitoes were offered sucrose meals via cotton pledgets, which were removed daily and processed for viral RNA by using real-time TaqMan reverse transcriptase-polymerase chain reaction (RT-PCR) assays. JEV, MVEV, and KUNV RNA was detected in all pledgets removed from batches of Cx. gelidus on days 7-14 postexposure. In contrast, detection rates were variable for Cx. annulirostris, with KUNV detected in 0.3 M sucrose pledgets on all days postexposure, and JEV and MVEV detected on 57 and 50% of days postexposure, respectively. Higher concentrations of sucrose in the pledget did not increase virus detection rates. When individual JEV-infected Cx. gelidus were exposed to the sucrose pledget, 73% of mosquitoes expectorated virus with titers that were detectable by TaqMan RT-PCR. These results clearly show that flaviviruses are expectorated by infected mosquitoes during the process of sugar feeding on artificial pledgets. Potential applications of the method for arboviral bioassays and field surveillance are discussed.Journal of Medical Entomology 10/2007; 44(5):845-50. · 1.76 Impact Factor -
Article: Evaluation of bifenthrin and permethrin as barrier treatments for military tents against mosquitoes in Queensland, Australia.
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ABSTRACT: A study comparing the effectiveness of barrier treatment of military tents with bifenthrin and permethrin in preventing entry of mosquitoes was conducted at Wide Bay Training Area, Queensland, Australia. Five military tents were erected at a site in bushland at Mosquito Creek, about 2 km from the coast. Two tents were sprayed with bifenthrin (Bistar 80SC, 0.1% mix, 12.5 ml/liter) and 2 with permethrin (Perigen 500, 1.2%, 24 ml/liter). One was left untreated and served as a control. Carbon dioxide-baited traps were placed inside each tent 0, 2, 4, 6, and 8 wk after treatment, and a single trap was placed in forest 50 m from the tents. The predominant mosquito species collected was Aedes vigilax (78% of collection). Compared to the untreated control, protection against mosquitoes entering treated tents was initially 78.6% for bifenthrin-treated tents and 84.3% for permethrin. At 4 wk, protection was 68.6% for bifenthrin and 50.7% for permethrin. After 6 wk, less than 34% protection was provided by either insecticide. There was no significant difference between the protection provided by either insecticide treatment. The study showed that barrier tent treatments provide a reasonable increase in preventing the entry of mosquitoes for at least 4 wk.Journal of the American Mosquito Control Association 07/2007; 23(2):208-12. · 0.91 Impact Factor -
Article: Laboratory evaluation of methylated coconut oil as a larvicide for Anopheles farauti and Culex annulirostris.
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ABSTRACT: The toxicity of methylated coconut oil (MCO) was compared with a commercially available oil larvicide (Golden Bear Oil GB-1111) in laboratory bioassays of 4th-stage larvae of Anopheles farauti Laveran and Culex annulirostris Skuse. Both larvicides were more toxic to Cx. annulirostris than to An. farauti and the LD50 (dose lethal to 50% of the test organisms) after 24 h exposure indicated that MCO was more toxic than GB-1111 for both An. farauti (LD50 = 8.6 microl versus 13.0 microl/156 cm2) and Cx. annulirostris (LD50 = 1.2 microl versus 3.6 microl/156 cm2). However, for LD95 GB-1111 was more toxic than MCO for both An. farauti (LD95 = 29 microl versus 48.0 microl/156 cm2) and Cx. annulirostris (LD95 = 7.2 microl versus 18.0 microl/156 cm2). Further study of MCO is warranted and may determine whether the addition of surfactant to MCO will lower the LD95. The possibility of community participation in the production and use of coconut products including MCO for malaria vector control is discussed.Journal of the American Mosquito Control Association 01/2006; 21(4):477-9. · 0.91 Impact Factor -
Article: Laboratory and field evaluation of commercial repellent formulations against mosquitoes (Diptera: Culicidae) in Queensland, Australia
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ABSTRACT: This paper is published with the approval of the Director General Defence Health Services (Australia). The opinions expressed herein are those of the authors and do not necessarily reflect those of the Australian Defence Force (ADF), Defence Health Service or any extant Defence policy. Mention of a commercial product does not constitute an endorse-ment of the product by the ADF. Abstract Laboratory tests of commercial repellent formulations were conducted against Anopheles farauti Laveran, Culex annulirostris Skuse, Ochlerotatus vigilax (Skuse) and Stegomyia aegypti (L.). The majority of repellent formulations tested contain N,N,-diethyl-3-methylbenzamide (also known as diethyl-m-toluamide, commonly called deet). Two formulations containing picaridin (1-piperidinecar-boxylate acid, 2-(2-hydroxyethyl)-1-methylpropylester, also known as KBR 3023), one containing ethyl butylacetylaminopropionate (EBAP) and two formulations containing essential oils (e.g. Cit-ronella oil) were also tested. In the laboratory tests, repellent formulations containing deet provided the best protection, and picaridin and EBAP also provided good protection. Citronella oil provided only limited protection. Two field trials to compare commercially available repellent formulations containing picaridin and deet against mosquitoes at Redcliffe, Queensland, were conducted. In the first, Autan Repel, containing 9.3% picaridin, RID, containing 10% deet, and Bushman Ultra, con-taining 80% deet in a gel, were compared. In the second, Autan Repel Army 20, containing 19.2% picaridin, OFF! Skintastic, containing 7% deet, and Aerogard, containing 12% deet, were compared. The predominant mosquito in both tests was Cx. annulirostris. Bushman provided >95% protection against all mosquitoes for at least 8 h when tests ceased. The other deet repellents also provided good protection against mosquitoes, with RID providing 5 h, Skintastic 4 h and Aerogard 2 h protection. The Autan repel (9.3% picaridin) provided >95% protection for 3 h, and Autan Repel Army (19.2% picaridin) provided 4 h protection. These studies have shown that commercial formulations of both deet and picaridin provide good protection against Cx. annulirostris, an important vector of arbovi-ruses in Australia.Australian Journal of Entomology 01/2005; 44. · 0.97 Impact Factor -
Article: Occurrence of Orientia tsutsugamushi in small mammals from Thailand.
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ABSTRACT: Extensive sampling of small mammals was conducted in eight provinces of Thailand between September 9, 1992 and April 29, 2001. A total of 3,498 specimens representing 22 species were collected. Eighty-eight percent (3,089 of 3,498) of the animals were collected from a region in Chiangrai Province, which is commonly recognized as endemic for human scrub typhus. Blood and tissue samples from each animal were tested for the presence of Orientia tsutsugamushi, the etiologic agent of scrub typhus. The predominant species collected were Rattus rattus (53%, n = 1,863), R. losea (18%, n = 638), Bandicota indica (16%, n = 564), and R. exulans (4%, n = 146). Orientia tsutsugamushi was detected in 10 of the 22 species of mammals that included R. bukit (25% infected, 1 of 4), R. rattus (23%, 419 of 1,855), R. argentiventer (22%, 5 of 23), R. berdmorei (22%, 2 of 9), R. losea (13%, 82 of 638), B. indica (9%, 52 of 564), R. koratensis (8%, 1 of 12), B. savilei (3%, 1 of 30), R. exulans (1%, 2 of 146), and Tupaia glis (2%, 1 of 49). Infected animals were found in Chiangrai (18% infected, 563 of 3,084), Bangkok (11%, 1 of 9), Sukothai (3%, 1 of 30), and Nonthaburi (1%, 1 of 69) Provinces. The implications towards scrub typhus maintenance and transmission are discussed.The American journal of tropical medicine and hygiene 12/2003; 69(5):519-24. · 2.59 Impact Factor -
Article: Survey of personal protection measures against mosquitoes among Australian defense force personnel deployed to East Timor.
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ABSTRACT: A questionnaire was completed by 955 Australian Defense Force soldiers from two battalion groups to determine their usage of mosquito repellents and bed nets during peacekeeping duties in East Timor. The survey showed that most soldiers (84%) used repellents, but only 19% used them daily. The soldiers used a number of repellent formulations; however, few soldiers used the Australian Defense Force deet (diethyl methylbenzamide) formulation containing 35% deet in a gel. Most soldiers preferred several commercial formulations, which contained 7 to 80% deet. The occurrence of mosquito-borne disease in soldiers was not affected by repellent usage, as the use of repellents was comparable between infected and noninfected individuals. The overall frequency of bed net usage differed in the two battalion groups. The occurrence of malaria in soldiers from one battalion group who did not sleep under a bed net every night of their deployment was significantly (p = 0.007) higher than those who did.Military medicine 04/2003; 168(3):227-30. · 0.92 Impact Factor -
Article: Efficiency of Leptotrombidium chiggers (Acari: Trombiculidae) at transmitting Orientia tsutsugamushi to laboratory mice.
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ABSTRACT: Thirteen different laboratory colonies of Leptotrombidim chiggers [L. chiangraiensis Tanskul & Linthicum, L. deliense Walch and L. imphalum (Vercammen-Grandjean &Langston)] were evaluated for their ability to transmit Orientia tsutsugamushi (Hyashi) to mice. Of 4,372 transmission attempts using individual chiggers from all 13 colonies, 75% (n = 3,275) successfully infected mice. Transmission rates for the individual chigger colonies ranged from 7 to 80%. Increasing the number of chiggers that fed on a given mouse generally increased transmission rates. Transmission of O. tsutsugamushi to mice by different generations (F1-F11) of certain chigger colonies was stable; however, transmission rates varied greatly in other colonies. Transmission rates (both vertical and horizontal) of several L. changraiensis colonies and the L. deliense colony were the highest, suggesting that these colonies may be useful for the development of a chigger-challenge model that can be used to evaluate the efficacy of candidate scrub typhus vaccines or therapeutic agents in laboratory mice.Journal of Medical Entomology 05/2002; 39(3):521-5. · 1.76 Impact Factor
Top co-authors
Top Journals
Institutions
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2009–2012
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Armed Forces Research Institute of Medical Sciences
Bangkok, Bangkok, Thailand
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2003–2011
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Australian Army Malaria Institute
Sydney, New South Wales, Australia
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2006
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University of QueenslandÂ
- School of Population Health
Brisbane, Queensland, Australia
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