1.Effects of vitamin B fortified sucrose solution on the longevity and reproductive potentials of laboratory-bred Culex quinquefasciatus Say adult
Tan, S.B., Nazni, W.A., Lee, H.L.
Tropical Biomedicine 2016;33(1):141-148
Laboratory colonised mosquitoes are usually maintained on vitamin B complex
fortified sucrose solution, however only few studies were conducted to evaluate the effects
of such practice. This study aimed to determine the effects of different concentrations of
sucrose solution fortified with and without 1% vitamin B complex on the longevity and
reproductive potential of adult female of a local strain of Culex quinquefasciatus Say. Two
arms of studies were carried out separately and each arm was triplicated. In one arm,
concentrations of sucrose solution at 0%, 1%, 3%, 5% and 10% fortified with 1% Vitamin B
complex were fed to the mosquitoes, while in the other arm, similar sucrose concentrations
were used but without 1% vitamin B complex. Adult Cx. quinquefasciatus maintained on 5%
sucrose solution fortified with 1% vitamin B complex exhibited significant extended vitality
and longevity in stimulating ovarian development, compared with other vitamin fortified
sucrose concentrations (p<0.05). The vitality and longevity of F0 and F1 males were 76.67±2.19
days and 57.67±8.19 days respectively. The F0 females survived the longest duration of
107.67±5.61 days and the F1 females survived 90.67±12.47 days with higher number of eggs
laid, i.e. 1427.67±62.89 eggs at a higher hatchability rate of 57.05±8.39% or 814.49 eggs
hatched. Thus, 5% sucrose solution fortified with 1% Vitamin B complex should be used to
produce colonies of homogenous mosquitoes as this exerts positive biological effects on
laboratory-bred Cx. quinquefasciatus.
2.Insecticide resistance development in Aedes aegypti upon selection pressure with malathion
Hidayati, H.* ; Nazni, W.A. ; Lee, H.L. ; Sofian-Azirun, M.
Tropical Biomedicine 2011;28(2):425-437
Bioassay test against malathion had been carried out with larval and adult stages
of Aedes aegypti. The mosquitoes were under selection pressure against malathion for fortyfive
consecutive generations. The rate of resistance development was measured by LC50 and
LT50 values. The larvae and adult females, after subjection to malathion selection for 45
generations, developed high resistance level to malathion, with resistance ratio of 52.7 and
3.24 folds, respectively over control mosquitoes. Cross-resistance towards the same and
different groups of insecticides was determined using the F44 and F45 malathion-selected
adult females. Insecticides tested were DDT (4.0%), permethrin (0.75%), propoxur (0.1%),
fenitrothion (1%), λ-cyhalothrin (0.05%) and cyfluthrin (0.15%). Results indicated that the
mosquitoes were highly resistant to DDT and fenitrothion, moderately resistant to propoxur,
tolerant to permethrin and λ-cyhalothrin, and very low resistant to cyfluthrin.
3.Morphological descriptions on the larvae of Hypopygiopsis fumipennis (Walker, 1856) (Diptera: Calliphoridae)
Heo, C.C ; Latif, B ; Silahuddin, S.A ; Nazni, W.A ; Omar, B.
Tropical Biomedicine 2015;32(1):151-159
The study on biodiversity of forensically important Diptera in the tropical rain
forest in Malaysia is scarce. Thus, a preliminary survey was conducted at a jungle fringe near
Kampung Bahagia Bukit Lagong, Sungai Buloh, Selangor. A rat carcass was offered to attract
carrion flies and we collected an adult female calliphorid, Hypopygiopsis fumipennis (Walker,
1856) during the fresh stage of carcass decomposition. The female fly was allowed to oviposit
on chicken liver in a container and the resulting larvae were reared to the adult stage. Along
the developmental process, several individuals from each instar were collected and preserved
in 70% ethanol and then processed on the slides. We recorded the duration of development for
each instar and described its larval features for the first time. The third instar larvae of H.
fumipennis showed accessory oral sclerite present, anterior spiracle with 13-15 papillae,
intersegmental spines mostly unicuspid with pointed end, and posterior spiracles heavily
sclerotized with inter-slit projections. Some larval differences between H. fumipennis and
Hypopygiopsis violacea were noted.
4.Scanning electron microscopic evaluation of the successful sterilization of Lucilia cuprina (Wiedemann) utilized in maggot debridement therapy (mdt)
Yeong, Y.S., ; Nazni, W.A.* ; Santana, R.L. ; Mohd Noor, I. ; Lee, H.L. ; Mohd Sofian, A.
Tropical Biomedicine 2011;28(2):325-332
In Malaysia, maggot debridement therapy (MDT) utilizes maggots of Lucilia
cuprina (Wiedemann) to debride necrotic tissue from wound surface, reduce bacterial infection
and therefore, enhance wound healing process. To evaluate the sterility of the sterile maggots
produced after sterilization process before delivering onto patient wounds. Sterility of sterile
maggots is crucial in ensuring the safe usage of MDT and patient’s health. Eggs of L. cuprina
collected from a laboratory colony were divided into treated group (sterilized) and control
group (non-sterilized). Treated group underwent sterilization while eggs from control group
were allowed to hatch without sterilization. Sodium hypochlorite and formaldehyde were the
main disinfectants used in this sterilization process. Scanning electron microscope (SEM)
was used to examine and ascertain the sterility of sterile maggots. SEM results showed that
all sterilized L. cuprina eggs and maggots achieved sterility and all were cleared from
bacterial contamination. In contrast, all non-sterilized eggs and maggots were found to be
colonized by microorganisms. Sterilization method employed to sterilize eggs and maggots
used in Malaysia MDT was proven successful and MDT is safe to be used as wound management
tools.
5.A new record for Lispe orientalis Wiedemann, 1824 (Diptera: Muscidae) from peninsular Malaysia
Chew, W.K. ; Kurahashi, H. ; Nazni, W.A. ; Heo, C.C. ; Heah, S.K. ; Jeffery, J. ; Lee, H.L.
Tropical Biomedicine 2012;29(3):489-492
Lispe orientalis Wiedemann, 1824 is recorded for the first time in peninsular Malaysia. Specimens were collected from a mushroom cultivation farm in Genting Highlands,
Pahang (3°25’18"N 101°47’48"E). Previously, this species had been recorded from Azerbaijin, India, Russia, Tajikistan, Thailand, Turkey and South Korea. The male of Lispe orientalis can be determined by the following characteristics: body non-metallic, ashy gray, third antennal segment black, R5 cell not narrow apically, hind metatarsus normal, legs entirely black, femora with long bristle-like hairs on av and pv surfaces, hind tibia without av and pv seta and the palpi orangish in colour.
6.Similar vertical transmission rates of dengue and chikungunya viruses in a transgenic and a non-transformed Aedes aegypti (L.) laboratory strain
Mansor, S.M., Haninah A. Ummu, Angamuthu, C., Lee, H.L., Murad, S., Nazni, W.A.
Tropical Biomedicine 2016;33(1):120-134
The increase of the burden of dengue and chikungunya and the relative failure of
traditional vector control strategies have highlighted the need to develop new control methods.
RIDL-SIT, a vector control method based on the release of engineered male mosquitoes, has
shown promising results from field trials conducted in the Cayman Islands and Brazil. In large
scale use, a small proportion of females might be released along with the males. Such females
are potential virus vectors; here we investigate the vertical transmission of dengue and
chikungunya of homozygous OX513A females.We provided females of OX513A-My1 and a
wild type comparator strain with blood meals artificially infected with dengue serotype 1, 2,
3, 4 or chikungunya viruses. For 14 days post-feeding, eggs laid by females were collected.
Larvae and their mothers were first tested by qRT-PCR, then by inoculation on cell cultures to
search for infectious viral particles. We found no significant difference between the minimum
infection rate of OX513A-My1 and wild type females. We also discussed the potential number
of females being released, a fraction of the female wild population. Consequently, we conclude
that there are no evidence that OX513A-My females, if released into the environment, would
cause more harm than their wild counterparts.
7.Status of pyrethroid resistance in Aedes (Stegomyia) aegypti (Linneaus) from dengue hotspots in Klang Valley, Malaysia
Siti-Futri, F.F. ; Rosilawati, R. ; Wan, K.L. ; Cheong, Y.L. ; Nazni, W.A. ; Lee, H.L.
Tropical Biomedicine 2020;37(No.1):201-209
The continued absence of an effective and safe tetravalent dengue vaccine and the lack of specific anti-viral treatment have made mosquito vector control using chemical insecticides as the mainstream for dengue prevention and control. However, the long-term use of chemical insecticides may induce resistance. Hence detection of insecticide resistance in dengue vectors is crucially important in ensuring the insecticide-based intervention in dengue control program is still effective and reliable. In this study, the susceptibility status of Aedes aegypti from five selected dengue hotspots in Klang Valley, Malaysia against pyrethroids was determined by employing the World Health Organization (WHO) protocol of adult bioassay. Four types of pyrethroids were tested against adult female Aedes aegypti to determine the knockdown rate, post 24-h adult mortality and resistance ratio. All field-collected Aedes aegypti strains were resistant to the four pyrethroids tested, except for the Taman Sungai Jelok (TSJ) strain. Permethrin exhibited the lowest knockdown rate against Aedes aegypti, followed by deltamethrin, cyfluthrin and lambda-cyhalothrin. This present study indicated the widespread of pyrethroid resistance in Aedes aegypti in Klang Valley, indicating the needs of implementing alternative measures in vector control program. The data in this study can be utilised as an input for insecticide resistance management of Aedes aegypti in Malaysia.
8.Pteridine fluorescence in age-determination of immature Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae)
Roziah, A. ; Rosilawati, R. ; Nazni, W.A. ; Norazizah, A. ; Khairul Asuad, M. ; Lee, H.L.
Tropical Biomedicine 2019;36(2):488-494
In the practice of forensic entomology, the chronological age of the maggots
retrieved from the cadaver is used to determine the minimum post-mortem interval (mPMI)
i.e. minimum time of death. The conventional method of aging the maggots is based on
measuring the growth rate of these maggots. Although effective, the constraint associated
with conventional method necessitates the development of new age determination method,
such as pteridine determination. Pteridine, a by-product of protein metabolism in insects is
known to correlate with the age of a variety of dipterans. A number of studies were
conducted on aging the adults of forensically important flies. In this study, pteridine was
extracted from Chrysomya megacephala and Chrysomya rufifacies maggots of known
age using established methods and determined by measuring the fluorescence at excitation
of 330nm and the emissions between 350nm and 600nm. Results exhibited significant
positive linear relationships between the pteridine accumulations and age of the fly
immature. Pteridine determination is a potential new age determination tool that can be
used to determine mPMI.
9.A preliminary proteomic study of permethrin resistant and susceptible Aedes aegypti (L.)
Rosilawati, R ; Nabila, R. ; Siti Futri Farahininajua, F. ; Nazni, W.A. ; Lee, H.L.
Tropical Biomedicine 2019;36(4):855-865
The mechanism of insecticide resistance is traditionally attributed to detoxification
enzymes, target site alteration, decreased penetration of insecticides and behavioural
resistance. Other form of mechanisms, such as the role of protein(s) in resistance is unknown.
In the present study, the protein profiling of both IMR-PSS strain (permethrin-selected) and
IMR-LS strain (laboratory-susceptible) 24 hours post exposure period to permethrin was
carried out via 1D-gel electrophoresis and liquid chromatography mass spectrometry (LC-MS/
MS). The bands which appeared in the gel of 1D-electrophoresis revealed an abundance of
proteins. The band pattern of both strains looked macroscopically alike and differed only in
band intensity. However, LC-MS/MS analysis revealed that the IMR-PSS strain produced extra
388 peptides that were not found in the IMR-LS strain, indicating that IMR-PSS strain reacted
differently from IMR-LS strain as a result of persistent exposure to permethrin. Since the
complex banding patterns of 1D-gel electrophoresis were difficult to interpret the significance
of the protein difference between IMR-PSS and IMR-LS strain, hence LC-MS/MS analysis is
ideally suited for better protein resolution and thus will allow more in-depth comparison of
the complex pattern. The findings here provide the first preliminary evidence that insecticide
resistance in mosquito induces up regulation of proteins that may be protective to mosquitoes
against insecticide and proteins could be another mechanism that contributes to development
of resistance.
10.Single and co-breeding of different mosquito species in fogging-free and dengue risk areas in West Malaysia
Wan-Norafikah, O. ; Chen, C.D. ; Mohd-Amir, M.H ; Azahari, A.H. ; Zainal-Abidin, A.H ; Nazni, W.A. ; Mariam, M. ; Mohd-Shahizan, J. ; Sofian-Azirun, M.
Tropical Biomedicine 2018;35(3):826-838
Ovitrap surveillance was carried out in fifteen localities encompassing foggingfree
and dengue risk areas in West Malaysia to determine on the dispersal and prevalence of
single and co-breeding of mosquito larvae particularly Aedes. Ovitraps were sited randomly
indoors and outdoors within human settlements in all study areas. All the localities exhibited
positive ovitraps with single breeding of Ae. albopictus that ranged between 64.29% and
100.00%. These findings indicated Ae. albopictus as the predominant container-breeding
species in all study areas. The co-breeding of Ae. aegypti with Ae. albopictus larvae (34
ovitraps), Ae. albopictus with Culex quinquefasciatus larvae (32 ovitraps) as well as Cx.
quinquefasciatus with Armigeres subalbatus larvae (1 ovitrap) were also detected in certain
study localities. Interestingly, co-breeding of Ae. albopictus with Ar. subalbatus larvae as
well as Ae. albopictus with Uranotaenia sp. larvae in Malaysia is reported for the first time in
the present study. Better understanding of the co-breeding scenario involving different species
of mosquito larvae is needed to ensure the efficacy of vector control actions to be conducted.