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.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).
6.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.
7.A new species of the Simulium (Simulium) crocinum species-group (Diptera: Simuliidae) from Vietnam
Takaoka, H. ; Ya&rsquo ; cob, Z. ; Sofian-Azirun, M. ; Chen, C.D. ; Low, V.L. ; Lau, K.W. ; Pham, X.D.
Tropical Biomedicine 2019;36(1):245-251
A new black fly species, Simulium yukawai, is described on the basis of one
female and its pupal exuviae from Vietnam. This new species is placed in the S. crocinum
species-group of Simulium (Simulium) (Diptera: Simuliidae). It is characterized in the female
by the paraproct covered with 48–50 distinct hairs on its ventral and lateral surfaces, and in
the pupa by the frons and most of the thorax bare, gill with six dark filaments in three pairs
closely arising from the base, of which the two outer filaments of the dorsal and middle pairs
are much longer than other filaments, abdomen with distinct spine-combs on the dorsal
surface of segments 7–9, and cocoon wall-pocket shaped, with a large anterolateral window
on each side. Taxonomic notes are given to separate this new species from related species.
This species is the fourth member of the S. crocinum species-group known from Vietnam.
8.Observations of scrotal mass, liver mass, haemolytic jaundice, and central vestibular disorder in Brugia pahangi-infected dogs
Vinnie-Siow, W.Y ; Low, V.L. ; Tan, T.K. ; Teoh, Y.B. ; Sivanandam, S. ; Vellayan, S. ; Lim, Y.A.L.
Tropical Biomedicine 2019;36(1):252-256
Brugia pahangi is known to infect humans and dogs. Its associated symptoms and
complications, however, have not been fully understood in dogs. Herein, we reported the
observations of B. pahangi infections in dogs with scrotal mass, liver mass, haemolytic
jaundice, and central vestibular disorder.
9.Three new species of black flies (Diptera: Simuliidae) from the Lesser Sunda Archipelago, Indonesia
Takaoka, H. ; Sofian-Azirun, M. ; Chen, C.D ; Lau, K.W. ; Halim, M.R.A. ; Low, V.L. ; Suana, I.W.
Tropical Biomedicine 2018;35(4):951-974
Simulium (Gomphostilbia) dhangi sp. nov., S. (G.) sumbaense sp. nov. and S.
(Nevermannia) wayani sp. nov. are described from the Lesser Sunda Archipelago, Indonesia.
Simulium (G.) sumbaense sp. nov. is placed in the S. varicorne species-group and is
characterized by the pupal gill with eight filaments arranged as (1+1+1+1+2)+2 from
dorsal to ventral, while S. (G.) dhangi sp. nov., unplaced to group, is characterized by the
pupal gill composed of two inflated trunks and four slender filaments all arising basally,
and the short larval antenna as long as the stem of the labral fan. Simulium (N.) wayani
sp. nov. belongs to the S. ruficorne species-group and is characterized by the female
spermatheca with an unsclerotized neck, and pupal gill with four inflated filaments. The
number of species of black flies from the archipelago increases from 19 to 22.
10.Nematode control failure due to anthelmintic resistance in a sheep farm in Malaysia: First identification of the F200Y mutation in the isotype 1 β-tubulin gene
Khadijah, S. ; Wahaf, A.N.S. ; Syahmi, M.I. ; Tan, T.K. ; Low, V.L. ; Azrul, L.M. ; Chong, J.L ; Lim, Y.A.L ; Abdullah, C.I.
Tropical Biomedicine 2018;35(4):999-1006
This paper reports total nematode anthelmintic resistance towards albendazole,
fenbendazole, levamisole and ivermectin in a commercial sheep farm located in Terengganu,
Malaysia. Faecal Egg Count Reduction Test (FECRT) was conducted on 25 sheep, where
five sheep in each group were treated with the respective four anthelmintics based on live
bodyweight. The balance of five sheep placed in the control group were not treated with
any anthelmintics. At day 13 post-treatment, faecal egg count was conducted and nematode
worm egg count reduction percentage was calculated to determine the resistance status
towards the respective anthelmintics tested. Results showed that nematodes were resistant
to all the anthelmintics tested, namely albendazole, fenbendazole, levamisole and ivermectin
with reduction percentage of 87%, 46%, 94% and 68%, respectively. Subsequently, the third
stage larvae of Haemonchus contortus and Trichostrongylus colubriformis recovered
from post-treatment faecal cultures were subjected to allele-specific polymerase chain
reaction (AS-PCR) assay to determine the presence of the benzimidazole resistance gene.
This study reports the occurrence of the classical F200Y mutation in the isotype 1 β-
tubulin gene, for the first time in Malaysia.