1.Modelling the effect of temperature change on the extrinsic incubation period and reproductive number of Plasmodium falciparum in Malaysia
Tropical Biomedicine 2012;29(1):121-128
Abstract. According to the report of the Intergovernmental Panel on Climate Change (IPCC),Malaysia will experience an increase of 3–5°C in the future. As the development of the
malaria parasite, Plasmodium falciparum, is sensitive to temperature, we investigated, using computer models, the effect of increase of 3º and 5ºC on the possible changes in the epidemiology of malaria transmission of P. falciparum in Malaysia. Four environmentally
different locations were selected: Kuala Lumpur (KL), Cameron Highlands (CH), Kota Kinabalu (KK) and Kinabalu Park (KP). The extrinsic incubation period (EIP) was estimated using hourly temperatures and the mean daily temperatures. The EIP values estimated using the
mean daily temperature were lower than those computed from hourly temperatures in warmer areas (KL, KK), but higher in the cooler areas (CH, KP). The computer simulations also
indicated that the EIP will be decreased if the temperature was raised by 3º or 5ºC, with the
effect more pronounced for the greater temperature increase, and for the cooler places. The
vector cohort that is still alive at a time to transmit malaria (sEIP) also increased when the
temperature was raised, with the increase more pronounced in the cooler areas. This study indicates an increase in temperature will have more significant effect in shortening the EIP in a cooler place (eg CH, KP), resulting in a greater sEIP, and consequently increasing the transmission intensity and malaria risk. A temperature increase arising from the global climate change will likely affect the epidemiology of malaria in Malaysia, especially in the cooler areas.
2.Taeniasis and neurocysticercosis among Malaysians
Tropical Biomedicine 2017;34(1):7-13
Taeniasis, endemic in Southeast Asia, is caused by Taenia saginata (for beef) or
Taenia solium and Taenia asiatica (for pork). T. solium also causes cysticercosis which can
affect various organs. Taeniasis and cysticercosis cases are rarely reported in Malaysia. We
report here two separate cases of beef taeniasis, and an interesting case of neurocysticercosis
in a Malay Muslim. The taeniasis cases involved a Malaysian Chinese and a native Sabahan.
Proglottids were recovered from them, and identification of the tapeworm done either from
the microscopic examination of the egg or using PCR-based molecular diagnosis. Upon
confirmation of taeniasis, both cases were given praziquantel and had been asymptomatic
since. The neurocysticercosis case involving a Muslim who presented with seizure, was
confirmed by histopathological examination of tissue sections taken from craniotomy excision
of the brain lesion. He was given one month course of albendazole 400 mg bid and
dexamethasone, and had been well and seizure free since. The two cases of taeniasis
documented here had acquired the disease through eating raw or undercooked contaminated
beef. For the neurocyticercosis case, it is suspected that he might have acquired the infection
in one of his travels through human to human transmission via contaminated food or water
consumption, given that Malaysia is not T. solium endemic area. Lastly praziquantel is an
effective drug for beef taeniasis, while a combination of albendazole and dexamethasone
work well for neurocysticercosis.
3.First detection of Babesia sp. in Bornean sun bear (Helarctos malayanus euryspilus Horsfield) in Sabah, Malaysia
Chua, T.H. ; Yeoh, B.N. ; Manin, B.O. ; Wong, S.T.
Tropical Biomedicine 2022;39(No.2):179-184
The Bornean sun bear, a subspecies of the endangered Malayan sun bear, resides only on Borneo
Island and little is known about diseases or parasites that may impact their health. In 2019, blood and
ticks were collected from 46 captive bears held at the Bornean Sun Bear Conservation Centre in Sabah,
Malaysia during annual health examinations in response to previous blood smear analysis that revealed
presumptive haemoparasites in more than half the resident bears. Polymerase chain reaction detected
a unique Babesia sp. in one of the bears. Disease surveillance of mosquitoes trapped along the outer
perimeter of the bears’ outdoor enclosure did not reveal any malaria parasites. This research marks the
first documented case in Bornean sun bears of both a Babesia sp. and the Ixodes tick Haemaphysalis
nr koningsbergeri. More research on incriminating the vector and the effects of Babesia infection on
the health of Bornean sun bears is needed. Due to the zoonotic nature of babesiosis, mitigative actions
should be taken to protect any humans that work with or come into close contact with these captive
bears or their enclosures.
4.Serotyping of dengue virus in 2016-17 outbreak in Kudat, Sabah, Malaysia
Aung, T.S. ; Gintarong, T. ; Balingi, D.B. ; Emran, A. ; Thein, T.T. ; Chua, T.H.
Tropical Biomedicine 2020;37(No.1):58-65
An outbreak of dengue in Kudat, northern Sabah in 2016-2017 provided an opportunity to investigate the circulating serotypes of dengue viruses of cases at Hospital Kudat. Between September 2016 and December 2017, a total of 156 dengue positive sera (tested positive by either NS1 antigen, or IgM & IgG antibody rapid test) were collected from dengue patients who had acute fever and showed signs and symptoms suggestive of dengue. RNA was extracted from the sera using QIAamp RNA Blood Mini Kit, and molecular amplification was performed using one-step RT-PCR kit, followed by nested PCR using HotStart Taq master mix kit with the primers of the dengue C-prM gene. There were 81 (52%) male and 75 (48%) female cases. The age group with the highest number of cases was the 10-19 years old, while the youngest infected was 8 months old and the oldest was 83 years old. RT-PCR results showed 88 sera dengue positive, 48 infected with a single serotype while another 40 with multiple serotypes. All four DENV serotypes were co-circulating during the outbreak period and DENV-1 was predominant. Molecular analysis also indicated 69.2%, 50.0%, 51.9% and 48.9% respectively of the NS1, IgM, IgG and IgM & IgG positive sera were RT-PCR positive for dengue. High number of cases were seen in December 2016, February and May 2017. The dengue outbreak might be related to switching of predominant serotype from DENV 4 to DENV 1.