1.First molecular genotyping of A302S mutation in the gamma aminobutyric acid (GABA) receptor in Aedes albopictus from Malaysia
Tropical Biomedicine 2015;32(3):554-556
Given the lack of molecular evidence in altered target-site insecticide resistance
mechanism in Aedes albopictus (Skuse) worldwide, the present study aims to detect the
presence of A302S mutation in the gene encoding the gamma aminobutyric acid receptor
resistant to dieldrin (Rdl) in Ae. albopictus for the first time from its native range of South East
Asia, namely Malaysia. World Health Organization (WHO) adult susceptibility bioassay indicated
a relatively low level of dieldrin resistance (two-fold) in Ae. albopictus from Petaling Jaya,
Selangor. However, PCR-RFLP and direct sequencing methods revealed the presence of the
A302S mutation with the predomination of heterozygous genotype (40 out of 82 individuals),
followed by the resistant genotype with 11 individuals. This study represents the first fieldevolved
instance of A302S mutation in Malaysian insect species.
2.Distribution and abundance of black flies (Diptera: Simuliidae) in recreation parks in Selangor State, Peninsular Malaysia
Chen, C.D. ; Takaoka, H. ; Tan, P.R. ; Lau, K.W. ; Low, V.L. ; Leong, C.S. ; Karen-Chia, H.M. ; Sofian-Azirun, M
Tropical Biomedicine 2016;33(3):583-588
A preliminary survey of larvae and pupae of black flies (Diptera: Simuliidae) was
conducted in three recreation parks [Templer Recreation Park (TRP), Congkak River Forest
Reserve (CRFR) and Ampang Forest Reserve (AFR)] located in Selangor State, which is
located 18 to 35 km from Kuala Lumpur city center, Malaysia. This study was initiated to
determine the distribution and abundance of filarial vectors, Simulium spp. A total of 12
species of black flies belonging to three subgenera (Gomphostilbia, Simulium and
Nevermannia) were collected. Simulium (Simulium) nobile was incriminated as the most
dominant species in all recreation parks. This study is a first report on the distribution and
abundance of black flies obtained from recreation parks in Malaysia.
3.Risk factors associated with flea infestation on cats
Azrizal-Wahid, N. ; Sofian-Azirun, M. ; Low, V.L
Tropical Biomedicine 2019;36(4):810-821
Fleas are the common cause of skin disorders in cats. They are well-known for
transmitting various pathogens to both cats and humans. Accordingly, this study was conducted
to gain insights on the risk factors associated with flea infestation on cats. Flea combing
conducted on 426 cats from four distinct regions in Peninsular Malaysia revealed a relatively
high rate of flea infestation on 306 cats (71.83%). A total of 651 fleas were collected, all of
them were identified as Ctenocephalides felis with the total intensity of 2.13 and abundance
of 1.53. The sex ratio of fleas was female-biased at 2.5:1 (♀=464, ♂=187). Statistical analysis
of the data revealed that flea infestation was significantly (P<0.05) associated with several
risk factors including region, age, weight, status (stray, sheltered, pet), body condition, and
hair length. Higher flea prevalence was also observed in female cats (77.99%), big-sized cats
(91.76%), stray cats (84.94%), cats with clean body condition (73.35%), and cats with long
hairs (78.38%) as compared to their contemporaries within the same comparison variables.
The high infestation of fleas in this study is indicative of cats as a flea reservoir particularly
C. felis. Thus the findings of this study and the knowledge gained on the risk factors can be
used to develop and improve control measures and management of flea infestations.
4.Serological survey of canine vector-borne diseases in two animal shelters in central Peninsular Malaysia
Vinnie-Siow, W.Y. ; Low, V.L. ; Tan, T.K. ; Teoh, Y.B. ; Prakash, B.K. ; Lim, Y.A.L.
Tropical Biomedicine 2021;38(No.1):145-149
Canine vector-borne diseases (CVBDs) are increasingly becoming a cause for global concern
because of their high morbidity and mortality rates in dogs. However, information on their
occurrence in Malaysia is still scanty. In this study, a total of 103 dog blood samples were
collected from two animal shelters in central Peninsular Malaysia and tested for the
antibodies against Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi, and the antigen of
Dirofilaria immitis. Of the 103 tested dogs, 44.7% (46) were found to be seropositive for Ehrlichia
spp., 30.1% (31) for Anaplasma spp. and 13.6% (14) for D. immitis. Co-infections of Anaplasma
spp. + Ehrlichia spp. (18.5%, 19) were most prevalent, followed by Anaplasma spp. + D. immitis
(1.9%; two) and D. immitis + Ehrlichia spp. (1.0%; one). Furthermore, three dogs (2.9%) were
also found to have triple infection, testing seropositive for Ehrlichia spp., Anaplasma spp. and
D. immitis. The dogs which were found to be seropositive with at least one pathogen were
66.7% (32/51) at shelter A, and 55.8% (29/52) at shelter B. Serological evidence showed that
the exposure of major vector-borne diseases in dogs in shelters was relatively high in the
surveyed areas. Routine detection and control of vector-borne diseases are of paramount
importance for reducing the risk of CVBDs transmission in dogs and humans.
5.Descriptions of the female, male and mature larva of Simulium contractum Takaoka (Diptera: Simuliidae) from Sulawesi, Indonesia
Takaoka, H. ; Sofian-Azirun, M. ; Chen, C.D. ; Halim, M.R.A. ; Lau, K.W. ; Low, V.L. ; Wayan Suana, I.
Tropical Biomedicine 2020;37(No.3):683-690
Simulium (Simulium) contractum Takaoka from Sulawesi, Indonesia was known only as the pupa. Its female, male and mature larva are described for the first time. The tentative assignment of this species in the Simulium dumogaense species-group is confirmed by the adult characters including the female and male genitalia. The female and male of this species are similar to those of Simulium (Simulium) tumpaense Takaoka & Roberts but are distinguished by the yellowish femora.
6.Morphological revision of Simulium (Gomphostilbia) ogatai (Rubtsov) in the S. ceylonicum species-group (Diptera: Simuliidae) from Japan
Takaoka, H. ; Otsuka, Y. ; Fukuda, M. ; Low, V.L. ; Ya&rsquo ; cob, Z.
Tropical Biomedicine 2022;39(No.2):231-238
Simulium (Gomphostilbia) ogatai (Rubtsov) from Japan, the only Palaearctic species in the S. ceylonicum
species-group, is morphologically revised. Its female is described for the first time and its male and
pupa are redescribed based on specimens from Gifu, Honshu. It is characterized in the female and male
by the base of the radius with a tuft of yellow hairs, in the female by the head slightly wider than the
thorax, 5.89 times as wide as the greatest width of the frons, and short sensory vesicle 0.21–0.24 times
as long as the third palpal segment; in the male by the number of upper-eye (large) facets in 15 vertical
columns and 16 horizontal rows, and hind basitarsus spindle-shaped, enlarged, 3.79 times as long as
wide, and 0.83 and 1.00 times as wide as the greatest width of the hind tibia and femur, respectively;
and in the pupa by the terminal hooks simple and cone-like, and the cocoon with an anterodorsal
projection. Taxonomic notes for this species are given relevant to several related species in the Oriental
Region, and its assignment to the S. ceylonicum species-group is confirmed.
7.Morphological and genetic analyses of Simulium (Gomphostilbia) okinawense Takaoka and S. (G.) tokarense Takaoka (Diptera: Simuliidae) from the Nansei Islands, Japan: redescription and transfer from the S. ceylonicum species-group to the S. asakoae species-group
Takaoka, H. ; Otsuka, Y. ; Fukuda, M. ; Low, V.L. ; Ya&rsquo ; cob, Z.
Tropical Biomedicine 2023;40(No.1):88-100
Simulium (Gomphostilbia) okinawense Takaoka and S. (G.) tokarense Takaoka, both from the Nansei
Islands, Japan, were morphologically reexamined and genetically analysed by using the COI gene
sequences. The female, male, pupa and mature larva of the two species are redescribed. Morphological
reexamination shows that both species are more similar to species in the S. asakoae species-group than
to those in the S. ceylonicum species-group, by having a medium-long female sensory vesicle, yellow tuft
hairs (S. (G.) okinawense) or yellow tuft hairs mixed with a few to several dark hairs (S. (G.) tokarense)
at the base of the radial vein in the female and male, and medium-long larval postgenal cleft. However,
the body of the male ventral plate (viewed ventrally) is parallel-sided (S. (G.) okinawense) or parallelsided or slightly narrowed (S. (G.) tokarense) and not emarginated basally, differing from those of most
species in the S. asakoae species-group. Our genetic analysis shows that S. (G.) tokarense is in the S.
asakoae species-group, and S. (G.) okinawense formed a separate sister clade with other members of
the S. asakoae species-group with high bootstrap support. From the results of morphological and genetic
analysis combined, S. (G.) okinawense and S. (G.) tokarense are transferred from the S. ceylonicum
species-group to the S. asakoae species-group.
8.Morphological redescription of Simulium takahasii (Rubtsov), the first species of the subgenus Wilhelmia Enderlein (Diptera: Simuliidae) recognized in East Asia
Takaoka, H. ; Otsuka, Y. ; Fukuda, M. ; Low, V.L. ; Ya&rsquo ; cob, Z.
Tropical Biomedicine 2023;40(No.2):266-272
Simulium takahasii (Rubtsov), which was originally described from Japan, and recorded from Korea and
China, is the first among the 19 species of the subgenus Wilhelmia Enderlein recorded from East Asia.
It is striking in mating, blood-feeding and ovipositing in captivity and in experimentally transmitting
Dirofilaria immitis (Leidy) and Brugia pahangi (Buckley & Edeson), and it is a severe biter of cattle and
horses, rarely of humans. Nevertheless, updated information about its morphological characteristics
was lacking, making comparisons with related species described from China difficult, since species of
the subgenus Wilhelmia are almost indistinguishable from one another, in particular, in their female
terminalia, male genitalia and most of larval features. In this study, as many morphological characteristics
as possible of S. takahasii based on specimens from Japan are redescribed. New information about
many features of this species including the length of the female sensory vesicle against the third palpal
segment, number of male upper-eye (large) facets, arrangement of the eight pupal gill filaments,
presence or absence of tiny dark setae on the dorsum of the larval abdomen and the number of rows
and hooklets of the larval posterior circlet will be useful in evaluating the species status of several
Wilhelmia species in China including the species regarded as S. takahasii.
9.Lactic acid bacteria waste infusion as a source of attraction and oviposition stimulation of gravid female Aedes albopictus mosquitoes
Suria, M.M. ; Yap, P.C. ; Low, V.L. ; AbuBakar, S. ; Lee, H.Y.
Tropical Biomedicine 2022;39(No.4):499-503
The Plasmodium knowlesi secreted protein with an altered thrombospondin repeat (PkSPATR) is an
important protein that helps in the parasite’s invasion into the host cell. This protein has been regarded
as one of the potential vaccine candidates against P. knowlesi infection. This study investigates the
genetic diversity and natural selection of PkSPATR gene of P. knowlesi clinical isolates from Malaysia.
PCR amplification of the full length PkSPATR gene was performed on 60 blood samples of infected P.
knowlesi patients from Peninsular Malaysia and Malaysian Borneo. The amplified PCR products were
cloned and sequenced. Sequence analysis of PkSPATR from Malaysia showed higher nucleotide diversity
(CDS p: 0.01462) than previously reported Plasmodium vivax PvSPATR (p = 0.0003). PkSPATR from
Peninsular Malaysia was observed to have slightly higher diversity (CDS p: 0.01307) than those from
Malaysian Borneo (CDS p: 0.01212). Natural selection analysis on PkSPATR indicated significant purifying
selection. Multiple amino acid sequence alignment revealed 69 polymorphic sites. The phylogenetic
tree and haplotype network did not show any distinct clustering of PkSPATR. The low genetic diversity
level, natural selection and absence of clustering implied functional constrains of the PkSPATR protein.
10.Two new black fly species of the Simulium (Simulium) rufibasis subgroup (Diptera: Simuliidae) from Taiwan
Takaoka, H. ; Low, V.L. ; Huang, Y.T. ; Fukuda, M. ; Ya&rsquo ; cob, Z.
Tropical Biomedicine 2021;38(No.3):403-412
Simulium (Simulium) rufibasis Brunetti originally described from India was once considered a geographic generalist widely distributed in the Oriental Region. In this study, the species previously regarded as S. (S.) rufibasis in Taiwan was morphologically re-evaluated and found to be distinguished in the male and pupa from true S. (S.) rufibasis from India. This new species is described as S. (S.) hehuanense sp. nov. based on a female, a male and their pupal exuviae in Taiwan. This new species is placed in the S. rufibasis subgroup of the S. tuberosum species-group, and is similar to S. (S.) yamatoense Takaoka, Adler & Fukuda from Japan and Korea, but it is barely distinguished by the slenderer forebasitarsi of the female and male. Another new, related species, S. (S.) xiulinense sp. nov., is described based on a male and its pupal exuviae. This new species is distinguished from S. (S.) hehuanense sp. nov. by the number of male upper-eye (large) facets in 20 or 21 vertical columns and 22 horizontal rows (19 vertical columns and 19 horizontal rows in the latter species), and presence of a pair of dorsolateral shiny spots on male abdominal segment 5 (absence in the latter species). Both new species inhabit streams at high elevations (ca, 2,600 m). They differ from S. (S.) sp. (probably S. (S.) arisanum Shiraki) from Taiwan, of the same subgroup, which breeds in streams at low elevations (433–685 m), by the pupal head and thorax covered with tubercles (bare in the latter species).