Medical Virology in Malaysia / 中国病毒学·英文版

Virology is a branch of biological science dealing with the study of viruses, and medical virology focuses on the study and control of diseases due to viruses that is of medical importance. The development of medical virology in Malaysia has its beginning in the Institute for Medical Research (IMR), following the establishment of the Division of Medical Zoology and Virus Research in the institute on 23 March 1953. The second institution in the country to establish diagnostic and research work in medical virology was Department of Medical Microbiology, Faculty of Medicine, University Malaya. This was followed by University Kebangsaan Malaysia, University Sains Malaysia and University of Sarawak Malaysia. The National Public Health Laboratory (NPHL) is the latest institution to establish a laboratory in 2003 for virus isolation and services to support country surveillance and outbreak investigation of infectious diseases due to viruses. In the field of medical virology, Malaysia contributed substantially in the areas of virus diagnostic services, development and research ranging from survey and documentation on the existence and prevalence of viruses causing diseases in Malaysia, clinical presentation and epidemiological features of virus diseases, evaluation of new diagnostic tests to pathogenesis of viral diseases. Malaysia contributed to the discoveries of at least 12 new viruses in the world. ASEAN plus Three (China, Japan, Republic of Korea) Emerging Infectious Programme was established to overcome the challenges and impact of emerging and re-emerging infectious diseases in this region. Malaysia as the co-ordinator of the laboratory component of the programme, contributed to strengthen the regional laboratory capability, capacity, laboratory-based surveillance and networking. The future of medical virology in Malaysia in terms of integration of diagnostic, reference and research to support the country's need will be enhanced and strengthened with the on-going development of the National Centre for Disease Control and Prevention (CDC Malaysia) which also incorporates a futuristic Special Diagnostic and Reference Laboratory.

Lessons from the Nipah virus outbreak in Malaysia

The Nipah virus outbreak in Malaysia (September 1998 to May 1999) resulted in 265 cases of acute encephalitis with 105 deaths, and near collapse of the billion-dollar pig-farming industry. Because it was initially attributed to Japanese encephalitis, early control measures were ineffective, and the outbreak spread to other parts of Malaysia and nearby Singapore. The isolation of the novel aetiological agent, the Nipah virus (NiV), from the cerebrospinal fluid of an outbreak victim was the turning point which led to outbreak control 2 months later. Together with the Hendra virus, NiV is now recognised as a new genus, Henipavirus (Hendra + Nipah), in the Paramyxoviridae family. Efforts of the local and international scientific community have since elucidated the epidemiology, clinico-pathophysiology and pathogenesis of this new disease. Humans contracted the infection from close contact with infected pigs, and formed the basis for pig-culling that eventually stopped the outbreak. NiV targeted medium-sized and small blood vessels resulting in endothelial multinucleated syncytia and fibrinoid necrosis. Autopsies revealed disseminated cerebral microinfarctions resulting from vasculitis-induced thrombosis and direct neuronal involvement. The discovery of NiV in the urine and saliva of Malaysian Island flying foxes (Pteropus hypomelanus and Petropus vampyrus) implicated these as natural reservoir hosts of NiV. It is probable that initial transmission of NiV from bats to pigs occurred in late 1997/early 1998 through contamination of pig swill by bat excretions, as a result of migration of these forest fruitbats to cultivated orchards and pig-farms, driven by fruiting failure of forest trees during the El Nino-related drought and anthropogenic fires in Indonesia in 1997-1998. This outbreak emphasizes the need for sharing information of any unusual illnesses in animals and humans, an open-minded approach and close collaboration and co-ordination between the medical profession, veterinarians and wildlife specialists in the investigation of such illnesses. Environmental mismanagement (such as deforestation and haze) has far-reaching effects, including encroachment of wildlife into human habitats and the introduction of zoonotic infections into domestic animals and humans.

A modified mycological medium for isolation and culture of Malassezia furfur

A mycological medium was developed for primary isolation and culture of lipophilic yeasts. It was initially based on published information of nutrients and trace components that would promote the growth of these yeasts. It was subsequently modified and adjusted to specifically promote the growth of lipophilic yeasts and simultaneously avoid the luxurious growth of other fungi and bacteria. With this medium, the conventional bacteriological procedures such as microbial streaking for pure culture and anti-microbial sensitivity testing could be carried out for these lipophilic yeasts.

Negative cross-reactivity of rabbit anti-Malassezia furfur antibodies with other yeasts

Anti-Malassezia furfur monospecific polyclonal antibodies was produced by repeated immunization of rabbit with Malassezia furfur yeast cells mixed with Freud adjuvant. The antibody titres of respective rabbit's serum samples prior to and after each immunization against M. furfur were assayed by indirect immunofluorescence technique using the M. furfur whole yeast antigen fixed in Teflon coated slides. The highest anti-M. furfur antibody titre achieved was 1 in 1280 dilution. At 1:20 dilution, none of the respective serum samples taken at various stages of immunization gave positive immunofluorescent staining against any of the other species of yeasts tested in this study. Anti-M. furfur monospecific polyclonal antibodies produced in rabbit in this study has the potential for diagnostic application in immunohistochemical detection of M. furfur in human tissues.

Seroprevalence of Malassezia furfur in an urban population in Malaysia

An in-house prepared M. furfur antigen was used to carry out a seroprevalence study in an urban population in Malaysia by indirect immunofluorescence assay. Of the 800 serum samples from all ages screened, 738 samples were positive for M. furfur specific IgG, giving an overall seropositive rate of 92.3%. There was no significant difference in the seropositive rates among the different gender group and races. However, there was a statistical significant difference in the seropositive rate among different age groups with a lower rate (73%) for the age group 5 years old and below, which increased rapidly to 99% for the 16 to 20 years old age group but declined slightly for the oldest age group. The degree of seropositivity, which semi-quantitatively reflect the anti-M. furfur specific IgG titre, did not show any significant difference among the gender and racial groups. On the other hand, there was a significant difference in the degree of seropositivity among the various age groups, with the 16 to 20 years old age group having the highest antibody titre and the extreme of age groups having the lower antibody titre.

Anthropogenic deforestation, El Ni?o and the emergence of Nipah virus in Malaysia

In late 1998, a novel paramyxovirus named Nipah virus, emerged in Malaysia, causing fatal disease in domestic pigs and humans with substantial economic loss to the local pig industry. Pteropid fruitbats have since been identified as a natural reservoir host. Over the last two decades, the forest habitat of these bats in Southeast Asia has been substantially reduced by deforestation for pulpwood and industrial plantation. In 1997/1998, slash-and-burn deforestation resulted in the formation of a severe haze that blanketed much of Southeast Asia in the months directly preceding the Nipah virus disease outbreak. This was exacerbated by a drought driven by the severe 1997-1998 El Ni?o Southern Oscillation (ENSO) event. We present data suggesting that this series of events led to a reduction in the availability of flowering and fruiting forest trees for foraging by fruitbats and culminated in unprecedented encroachment of fruitbats into cultivated fruit orchards in 1997/1998. These anthropogenic events, coupled with the location of piggeries in orchards and the design of pigsties allowed transmission of a novel paramyxovirus from its reservoir host to the domestic pig and ultimately to the human population.