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.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.
3.Imported case of Leishmania tropica cutaneous leishmaniasis in a 10-year-old child in Malaysia
Tan, T.K. ; Yap, N.J. ; Leong, K.F. ; Teh, C.S. ; Tay, S.T. ; Lim, Y.A.L.
Tropical Biomedicine 2022;39(No.1):86-88
The present paper reported a first imported case of cutaneous leishmaniasis in a 10-yearold child who returned from Saudi Arabia to Malaysia. Six weeks after his travel to Malaysia,
two erythematous dermal nodules were developed over his right cheek and chin. Occurrence
of intracellular amastigote of Leishmania was observed through examination of skin biopsy
with hematoxylin and eosin stain. Furthermore, molecular analysis of ribosomal internal
transcribed spacer 1 (ITS1) of Leishmania spp. confirmed the child was infected with Leishmania
tropica. The child was given oral fluconazole and he had a 80% recovery before he went back
to Saudi Arabia.
4.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.
5.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.
6.Bioefficacy of mosquito mat vaporizers and associated metabolic detoxication mechanisms in Aedes aegypti (Linnaeus) in Selangor, Malaysia: A statewide assessment
Azratul-Hizayu, T. ; Chen, C.D. ; Lau, K.W. ; Azrizal-Wahid, N. ; Tan, T.K. ; Lim, Y.A.L. ; Sofian-Azirun, M. ; Low, V.L.
Tropical Biomedicine 2021;38(No.3):327-337
This study aims to examine the efficacy of mosquito mat vaporizers on Aedes aegypti and their associated metabolic detoxication mechanisms. For this purpose, Aedes aegypti (Linnaeus) was collected from nine districts in Selangor, Malaysia and tested with mosquito vaporizing mat bioassays. The same populations were also subjected to biochemical assays to investigate activities of detoxifying enzymes, namely non-specific esterase (EST), glutathione-S-transferase (GST) and mixed function oxidase (MFO). The efficacy of Ae. aegypti on the active ingredients tested in decreasing order were d- allethrin > dimefluthrin > prallethrin with PBO > prallethrin. The results further indicated significant enhancement mean levels of EST, GST and MFO in pyrethroid-resistant populations. The mortality rate of Ae. aegypti in response to pyrethroid active ingredients was associated with MFO activity, suggesting it is an important detoxification enzyme for the populations tested. In view of the presence of resistance against household insecticide products, pyrethroid efficacy on Ae. aegypti populations needs to be monitored closely to ensure the implementation of an effective vector control program in Malaysia.