Boonlert Lumlertdacha

Bat Nipah virus, Thailand

Surveillance for Nipah virus (NV) was conducted in Thailands bat population. Immunoglobulin G antibodies to NV were detected with enzyme immunoassay in 82 of 1,304 bats. NV RNA was found in bat saliva and urine. These data suggest the persistence of NV infection in Thai bats.

Survey for Bat Lyssaviruses, Thailand

Surveillance for lyssaviruses was conducted among bat populations in 8 provinces in Thailand. In 2002 and 2003, a total of 932 bats of 11 species were captured and released after serum collection. Lyssavirus infection was determined by conducting virus neutralization assays on bat serum samples. Of collected samples, 538 were either hemolysed or insufficient in volume, which left 394 suitable for analysis. These samples included the following: Pteropus lylei (n = 335), Eonycteris spelaea (n = 45), Hipposideros armiger (n = 13), and Rousettus leschennaulti (n = 1). No serum samples had evidence of neutralizing antibodies when tested against rabies virus. However, 16 samples had detectable neutralizing antibodies against Aravan virus, Khujand virus, Irkut virus, or Australian bat lyssavirus; all were specifically associated with fruit bats P. lylei (n = 15) and E. spelaea (n = 1). These results are consistent with the presence of naturally occurring viruses related to new putative lyssavirus genotypes.

Transmission dynamics of rabies virus in Thailand: Implications for disease control

BackgroundIn Thailand, rabies remains a neglected disease with authorities continuing to rely on human death statistics while ignoring the financial burden resulting from an enormous increase in post-exposure prophylaxis. Past attempts to conduct a mass dog vaccination and sterilization program have been limited to Bangkok city and have not been successful. We have used molecular epidemiology to define geographic localization of rabies virus phylogroups and their pattern of spread in Thailand.MethodsWe analyzed 239 nucleoprotein gene sequences from animal and human brain samples collected from all over Thailand between 1998 and 2002. We then reconstructed a phylogenetic tree correlating these data with geographical information.ResultsAll sequences formed a monophyletic tree of 2 distinct phylogroups, TH1 and TH2. Three subgroups were identified in the TH1 subgroup and were distributed in the middle region of the country. Eight subgroups of TH2 viruses were identified widely distributed throughout the country overlapping the TH1 territory. There was a correlation between human-dependent transportation routes and the distribution of virus.ConclusionInter-regional migration paths of the viruses might be correlated with translocation of dogs associated with humans. Interconnecting factors between human socioeconomic and population density might determine the transmission dynamics of virus in a rural-to-urban polarity. The presence of 2 or more rabies virus groups in a location might be indicative of a gene flow, reflecting a translocation of dogs within such region and adjacent areas. Different approaches may be required for rabies control based on the homo- or heterogeneity of the virus. Areas containing homogeneous virus populations should be targeted first. Control of dog movement associated with humans is essential.

Survival of Naturally Infected Rabid Dogs and Cats

A total of 1820 dogs and 332 cats that appeared ill or had bitten humans or animals were observed for >or=10 days. Of these, 957 dogs and 94 cats that were confirmed to be rabid survived <10 days after admission to our institution. This study supports current recommendations that dogs and cats that are suspected of being rabid should be euthanized and examined or, if this is inappropriate, confined and observed for 10 days.

Furious and paralytic rabies of canine origin: neuroimaging with virological and cytokine studies.

Furious and paralytic rabies differ in clinical manifestations and survival periods. The authors studied magnetic resonance imaging (MRI) and cytokine and virus distribution in rabies-infected dogs of both clinical types. MRI examination of the brain and upper spinal cord was performed in two furious and two paralytic dogs during the early clinical stage. Rabies viral nucleoprotein RNA and 18 cytokine mRNAs at 12 different brain regions were studied. Rabies viral RNA was examined in four furious and four paralytic dogs during the early stage, and in one each during the late stage. Cytokine mRNAs were examined in two furious and two paralytic dogs during the early stage and in one each during the late stage. Larger quantities of rabies viral RNA were found in the brains of furious than in paralytic dogs. Interleukin-1β and interferon-γ mRNAs were found exclusively in the brains of paralytic dogs during the early stage. Abnormal hypersignal T2 changes were found at hippocampus, hypothalamus, brainstem, and spinal cord of paralytic dogs. More widespread changes of less intensity were seen in furious dog brains. During the late stage of infection, brains from furious and paralytic rabid dogs were similarly infected and there were less detectable cytokine mRNAs. These results suggest that the early stage of furious dog rabies is characterized by a moderate inflammation (as indicated by MRI lesions and brain cytokine detection) and a severe virus neuroinvasiveness. Paralytic rabies is characterized by delayed viral neuroinvasion and a more intense inflammation than furious rabies. Dogs may be a good model for study of the host inflammatory responses that may modulate rabies virus neuroinvasiveness.

Molecular epidemiology of rabies in Thailand

For the purpose of making clear the dynamics of rabies viruses that are prevalent among dogs in Asia, especially Thailand, nucleoprotein (N) genes of isolates derived from Thailand were partially sequenced, and a phylogenetic analysis was performed on the basis of the sequencing data. Firstly, all 27 isolates from Thailand belonged to one group that was distantly related to an isolate from China and was separated into at least six lineages. On the other hand, the isolate from Japan was related to viruses from the Arctic. Secondly, in order to analyze the diversity of the N gene more conveniently, restriction fragment length polymorphism (RFLP) analysis was performed on the N gene of 27 isolates from Thailand. The RFLP analysis could distinguish the lineages of each isolate, and the lineages of additional 34 isolates were deduced by this method. On examination of the geographical distribution of the six lineages, based on the results of phylogenetic and RFLP analyses, it was clear that infection cycles of the rabies virus in Thailand have tended to be maintained endemically.

Fluorescent Antibody Test for Rabies: Prospective Study of 8,987 Brains

A prospective study of 8,987 canine, feline, human, and other mammalian brains (and one avian brain) was undertaken. The brains were analyzed for rabies antigens; two samples were obtained from each brainstem, and one sample was obtained from each hippocampus. The samples were stained with rabies conjugate and examined by use of fluorescence microscopy. There were no false-negative results. We conclude, therefore, that postexposure rabies treatment is not requisite in all cases, provided that the fluorescent antibody test is performed without delay in a laboratory experienced with the procedure and microscopy results are fluorescent negative.

Rabies-Related Knowledge and Practices Among Persons At Risk of Bat Exposures in Thailand

Background Rabies is a fatal encephalitis caused by lyssaviruses. Evidence of lyssavirus circulation has recently emerged in Southeast Asian bats. A cross-sectional study was conducted in Thailand to assess rabies-related knowledge and practices among persons regularly exposed to bats and bat habitats. The objectives were to identify deficiencies in rabies awareness, describe the occurrence of bat exposures, and explore factors associated with transdermal bat exposures. Methods A survey was administered to a convenience sample of adult guano miners, bat hunters, game wardens, and residents/personnel at Buddhist temples where mass bat roosting occurs. The questionnaire elicited information on demographics, experience with bat exposures, and rabies knowledge. Participants were also asked to describe actions they would take in response to a bat bite as well as actions for a bite from a potentially rabid animal. Bivariate analysis was used to compare responses between groups and multivariable logistic regression was used to explore factors independently associated with being bitten or scratched by a bat. Findings Of 106 people interviewed, 11 (10%) identified bats as a potential source of rabies. A history of a bat bite or scratch was reported by 29 (27%), and 38 (36%) stated either that they would do nothing or that they did not know what they would do in response to a bat bite. Guano miners were less likely than other groups to indicate animal bites as a mechanism of rabies transmission (68% vs. 90%, p = 0.03) and were less likely to say they would respond appropriately to a bat bite or scratch (61% vs. 27%, p = 0.003). Guano mining, bat hunting, and being in a bat cave or roost area more than 5 times a year were associated with history of a bat bite or scratch. Conclusions These findings indicate the need for educational outreach to raise awareness of bat rabies, promote exposure prevention, and ensure appropriate health-seeking behaviors for bat-inflicted wounds, particularly among at-risk groups in Thailand.

Worldwide rabies deaths prevention—A focus on the current inadequacies in postexposure prophylaxis of animal bite victims

The World Health Organization reports that over 60,000 humans die of rabies annually, worldwide. Most occur in remote regions of developing countries. Almost all victims received no postexposure rabies prophylaxis (PEP). There are no facilities or health personnel able to provide it in many areas where the disease is prevalent. A first approach to correct this problem would be by extending provision of modern PEP to areas where human rabies is most prevalent.

Rabies research in resource-poor countries.

Many cost-benefit/effective rabies research projects need to be carried out in less-developed canine-endemic regions. Among these are educational approaches directed at the public and governments. They would address effective primary wound care, availability, and proper use of vaccines and immunoglobulins, better reporting of rabies, final elimination of dangerous nerve tissue-derived vaccines, and the recognition that rabies is still expanding its geographic range. Such efforts could also reduce deaths in victims who had received no or less than adequate postexposure prophylaxis. There is a need for new technology in canine population control and sustainable vaccination. We have virtually no workable plans on how to control bat rabies, particularly that from hematophagous bats. Preexposure vaccination of villagers in vampire rabies-endemic regions may be one temporary solution. Current efforts to reduce further the time required and vaccine dose required for effective postexposure vaccination need to be encouraged. We still have incomplete understanding of the transport channels from inoculation site to rabies virus antibody generating cells. The minimum antigen dose required to achieve a consistently protective and lasting immune response has been established for intramuscular vaccine administration, but is only estimated for intradermal use. Greater knowledge may have clinical benefits, particularly in the application of intradermal reduced dose vaccination methods. Curing human rabies is still an unattained goal that challenges new innovative researchers.