1.Effects of a juvenile hormone analogue pyriproxyfen on monogynous and polygynous colonies of the Pharaoh ant Monomorium pharaonis (Hymenoptera: Formicidae)
Tropical Biomedicine 2015;32(3):453-462
To evaluate the effects of the juvenile hormone analogue pyriproxyfen on colonies
of the Pharaoh ant Monomorium pharaonis (L.), peanut oil containing different concentrations
(0.3, 0.6, or 0.9%) of pyriproxyfen was fed to monogynous (1 queen, 500 workers, and 0.1 g of
brood) and polygynous (8 queens, 50 workers, and 0.1 g of brood) laboratory colonies of M.
pharaonis. Due to its delayed activity, pyriproxyfen at all concentrations resulted in colony
elimination. Significant reductions in brood volume were recorded at weeks 3 – 6, and
complete brood mortality was observed at week 8 in all treated colonies. Brood mortality was
attributed to the disruption of brood development and cessation of egg production by queens.
All polygynous colonies exhibited significant reduction in the number of queens present at
week 10 compared to week 1. Number of workers was significantly lower in all treated
colonies compared to control colonies at week 8 due to old-age attrition of the workers
without replacement. At least 98.67 ± 1.33% of workers were dead at week 10 in all treated
colonies. Thus, treatment with slow acting pyriproxyfen at concentrations of 0.3 – 0.9% is an
effective strategy for eliminating Pharaoh ant colonies.
2.Molecular detection of Haemophilus parasuis serotypes 4, 5 or 12 and 13 in Peninsular Malaysia
Lee, C.Y. ; Ooi, P.T. ; Zunita, Z. ; Noordin, M.M.
Tropical Biomedicine 2019;36(2):482-487
Although the economic importance of Haemophilus parasuis infection causing
Glasser’s disease is prevalent throughout pig farms in Peninsular Malaysia, there is a
dearth of knowledge on its actual nature. In this study, a multiplex PCR was performed to
screen for three major predominant virulent strains of H. parasuis, which are serotypes 4,
5 or 12 and 13. A total of 175 tissues or bodily fluid samples of various parts were collected
from diseased animals from October, 2016 to February, 2018; with total of 62.9% positive
detection of H. parasuis. The highest detection was found to be in the pericardial sac
fibrin (90.9%) followed by pleural fibrin, lung, pleural fluid, tonsil, pericardial sac, peritoneal
fluid, abdominal fibrin, joint fluid, brain and pericardium. Serotype 13 was the highest
(40/110) followed by serotype 4(37/110), serotype 5(31/110) and 12 samples were nontypable
(12/110). The presence of untypable serotype also drives to further identification
of other serotypes in Malaysia.
3.First molecular detection of porcine circovirus type 4 (PCV4) in Malaysia
Tan, C.Y. ; Thanawongnuwech, R. ; Arshad, S.S. ; Hassan, L. ; Lee, C.Y. ; Low, S.E. ; Fong, W.C.M. ; Ooi, P.T.
Tropical Biomedicine 2023;40(No.3):301-306
Porcine circovirus type 4 (PCV4) is the newest member in the porcine circovirus family, first reported in
2020. To date, the presence of PCV4 has only been reported in China, South Korea and most recently
in Thailand. Detection of PCV4 have been reported in various production stages of pigs from piglets,
finishers to sows; associated with a myriad of clinical manifestations including porcine dermatitis and
nephropathy syndrome (PDNS), postweaning multisystemic wasting syndrome (PMWS), respiratory,
enteric and neurological diseases. While successful virus isolation and culture has yet to be reported,
pathogenicity of PCV4 has been demonstrated through infectious clone studies. The objective of this
study is to investigate the presence of PCV4 in Malaysian porcine population to update the epidemiology
of porcine circoviruses in Malaysia. A total of 49 samples from commercial intensive pig farms,
abattoir and wild boar population were subjected to conventional polymerase chain reaction assay to
detect PCV4 capsid (cap) genome. Resulting cap nucleotide sequences were analyzed for maximum
likelihood phylogeny relationship. Results revealed that PCV4 is present in Peninsular Malaysia at a
molecular prevalence of 4.08% (2 / 49 samples). Both PCV4 positive samples originated from clinically
healthy finishers. Malaysian PCV4 strains were classified as genotype PCV4b, and were found to be
phylogenetically distinct from the China, South Korea and Thailand strains. With this latest update of
the novel PCV4 in Malaysia, it is clear that more attention needs to be given to the investigation of
novel porcine circoviruses (PCV) and management of PCV diseases.
4.Whole genome sequencing of Streptococcus suis revealed potential drug resistance and zoonotic transmission in companion cat
Lee, C.Y. ; Selvarajah, G.T. ; Zakaria, Z. ; Mustaffa-Kamal, F. ; Gan, H.M. ; Voon, K.G.L. ; Fong, M.W.C ; Ooi, P.T.
Tropical Biomedicine 2024;41(No.1):97-108
Streptococcus suis is a bacterium of clinical importance in diverse animal hosts including companion
animals and humans. Companion animals are closely associated in the living environment of humans
and are potential reservoirs for zoonotic pathogens. Given the zoonotic potential of S. suis, it is crucial
to determine whether this bacterium is present among the companion animal population. This study
aimed to detect Streptococcus suis in companion animals namely cats and dogs of the central west
coast of Peninsular Malaysia and further characterize the positive isolates via molecular and genomic
approach. The detection of S. suis was done via bacterial isolation and polymerase chain reaction assay
of gdh and recN gene from oral swabs. Characterization was done by multiplex PCR serotyping, as well
as muti-locus sequence typing, AMR gene prediction, MGE identification and phylogenomic analysis
on whole genome sequence acquired from Illumina and Oxford Nanopore sequencing. Among the 115
samples, PCR assay detected 2/59 of the cats were positive for S. suis serotype 8 while all screened
dog samples were negative. This study further described the first complete whole genome of S. suis
strain SS/UPM/MY/F001 isolated from the oral cavity of a companion cat. Genomic analysis revealed a
novel strain of S. suis having a unique MLST profile and antimicrobial resistance genes of mefA, msrD,
patA, patB and vanY. Mobile genetic elements were described, and pathogenic determinants matched
to human and swine strains were identified. Phylogenetic tree analysis on the core genome alignment
revealed strain SS/UPM/MY/F001 was distinct from other S. suis strains. This study provided insight
into the detection and genomic features of the S. suis isolate of a companion cat and highlighted its
potential for antimicrobial resistance and pathogenicity.