Tropical biomedicine最新文献

Antibody cross-reactivity among flaviviruses is a major limitation in understanding the prevalence without vector control measures. In this study, we investigated the presence of Zika virus (ZIKV)-specific antibodies and the significance of their cross-reactivity with other flaviviruses, which could affect the serological specificity in both symptomatic and asymptomatic pregnant women. Among the results obtained from 217 serum samples tested for ZIKV-specific IgM and IgG, no specific predictions regarding seropositivity or exposure due to extensive cross-reactivity with dengue virus (DENV) serology could be made. Clear-cut positivity was observed in 1.8% (n = 4) and 1.0% (n = 2) for ZIKV IgM and IgG, respectively. The same samples assessed for DENV showed 1.3% (n = 3) seropositivity each for IgM and IgG levels. None of the samples were positive for ZIKV and DENV IgM or IgG. However, one sample (0.4%) tested positive for ZIKV and DENV IgM. No significant correlation was observed between DENV IgM and IgG when comparing the overlapped serotiters. On the other hand, the ZIKV IgG-positive sample showed higher serotiters for DENV IgG, indicating cross-reactivity with ZIKV but without statistical significance. Therefore, screening for the incidence of ZIKV becomes particularly challenging in a population where the presence or pre-exposure to DENV is observed. Our observations further suggest that unless flavivirus prevalence is properly addressed, determining the prevalence of ZIKV antibodies, which may be confounded with other uninvestigated flaviviruses, will be complicated.

We aimed at determination of acaricidal, larvacidal, and repellent activities of green synthesized silver nanoparticles (SNP) against Hyalomma dromedarii as one of the most common ticks in camels. SNP were green synthesized by reducing Lupinus albus extract through the precipitation technique. The acaricidal, larvicidal, and repellent activity of SNP against H. dromedarii was studied through the adult immersion test (AIT), the larval packet test (LPT), the vertical movement behavior of tick's larvae method, anti-acetylcholinesterase (AChE) activity, and oxidative enzyme activity. The green synthesized SNP displayed a spherical form with a size ranging from 25-90 nm; whereas the most distribution of particles size was reported at 50-65 nm. SNP dose-dependently (p<0.001) increased the mortality rate of H. dromedarii adult; whereas at 16 and 32 µg/mL completely killed the adult females. Treatment of exposure of H. dromedarii adult to SNP markedly (p<0.001) declined the mean number, weight, and hatchability of eggs. Treatment of H. dromedarii larvae with SNP reduced the viability rate of larvae with the LC₅₀ and LC₉₀ values of 3.1 and 6.9 µg/mL, respectively. Exposure of H. dromedarii larvae to SNP, especially at ½ LC50 and LC50, markedly (p<0.001) increased the oxidative stress and declined the level of antioxidant enzymes in H. dromedarii larvae; whereas, markedly suppressed the AChE activity of the larvae stage of H. dromedarii in comparison to the control group. These results showed that SNP green synthesized by L. albus extract had promising acaricidal, larvicidal and repellent activity against H. dromedarii adults and larvae as a dose-dependent response. SNP also considrably decreased the level of acetylcholinesterase and antioxidant activity and also provokes oxidative stress in H. dromedarii larvae. However, more investigation must be designed to clear the accurate mechanisms and the efficacy of SNP in practical use.

The biting midge Culicoides peregrinus Kieffer is a significant pest and vector species, and knowledge of its genetic diversity and genetic structure is critically important for designing an effective control program. However, such information is limited to only small sample-size DNA barcoding studies. Therefore, in this study, we used mitochondrial cytochrome c oxidase I (COI) to examine genetic structure and diversity of C. peregrinus from northeastern Thailand. In addition, we also inferred genetic relationships between C. peregrinus from Thailand and those reported from other countries across the geographic range of the species. Maximum intraspecific genetic divergence (3.83%) within Thai specimens was relatively high compared to other Culicoides species. Genetic structure analysis revealed that 71% (32 from 45) of population comparisons were highly significantly different. A high level of genetic structure among populations, even between those in close geographic proximity (22 km geographic distance) suggested that there has been little or no movement between local populations. This is possibly due to the ability to exploit diverse types of breeding site and a generalist feeding habit which enables C. peregrinus to complete its life cycle within cattle pens. Genetic relationships between Thai C. peregrinus and those reported from other countries revealed three genetically divergent lineages (A, B and C) associated with geographic origins. Specimens from Thailand + China formed lineage A, those from Australia formed lineage B and India + Bangladesh belonged to lineage C. These genetically divergent lineages also agree with morphological variation of the wing pale marking spots. Further investigation using independent genetic loci from nuclear genes will be very useful to resolve taxonomic status of these divergent lineages.

In Malaysia presently, the main cause of human malaria is by the zoonotic monkey parasite Plasmodium knowlesi. A previous study has suggested that the P. knowlesi merozoite surface protein 1 (Pkmsp-1) block IV to be a suitable multiplicity of infection (MOI) genotyping marker for knowlesimalaria. This study therefore aimed to investigate the usefulness of Pkmsp-1 block IV in assessing the MOI of P. knowlesi in clinical isolates from Malaysia. Two allele-specific PCR primer pairs targeting the two allelic families of block IV (T1 and T2) were designed, and used to genotype P. knowlesi in 200 blood samples (100 from Peninsular Malaysia and 100 from Malaysian Borneo). Results showed that the mean MOI in Malaysian Borneo was slightly higher as compared to Peninsular Malaysia (1.58 and 1.40, respectively). Almost half of the total blood samples from Malaysian Borneo (52%) had polyclonal infections (i.e., more than one allele of any family type) as compared to Peninsular Malaysia (33%) samples. The T1 allelic family was more prevalent in Peninsular Malaysia (n=75) than in Malaysian Borneo (n=60). The T2 allelic family, however, was more prevalent in the Malaysian Borneo (n=87 vs n=53 respectively). This study shows that the single locus Pkmsp-1 block IV can serve as a simple alternative genetic marker for estimating knowlesi malaria MOI in a population. Future MOI studies should focus on macaque populations as macaques are the natural host of P. knowlesi.

Immune responses are largely regulated by cytokines. Genetic polymorphisms of the regulatory coding regions are recognized to impact the expression of cytokines. The abnormal cytokine levels in hepatitis C virus (HCV) infection seems to be involved in disease progression, viral survival, and therapeutic response. The current study assesses the polymorphisms associated with IL-6, IL-10, IL28B, IFN-γ, TGF-β, and TNF-α on the genotypic susceptibility to HCV infection and Ribavirin response to Peg interferon. Droplet digital polymerase chain reaction (PCR) was used to assess the gene polymorphisms associated with IL-6 A/G (rs2069837), IL-10-1082 G/A (rs1800896)], IL28B C/T (rs12979860), IFN-γ +874 A/T (rs2430561), TGF-β 1-509 C/T (rs1800469) and TNF-α-308 G/A promoter (rs1800629) from stored samples of 200 healthy individuals and 300 HCV infected patients. There was a significant association of AG and AA genotypes of IL28B, IFN-γ, TGF-β1, and TNF-α over HCV susceptibility and treatment outcome. However, no association between IL-6 and IL-10 gene polymorphism to HCV susceptibility response to the treatment. The observations indicate IL28B CT, TGF-β1 CT, TT and TNF- AG with AA genotypes influence the cytokine expression, which is related to susceptibility and resistance to HCV infection and combined antiviral therapy.

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.

Trichomonas tenax, an oral flagellated protozoon found in humans, potentially associated with the inflammation of periodontal tissues and decreased immunity that causes the tissue damage and tooth loss from chronic infection. Currently, there is a lack of data regarding the prevalence of T. tenax infection in Thailand. Therefore, this study aimed to measure prevalence of T. tenax in periodontal disease patients by using polymerase chain reaction (PCR) to amplify the 18S ribosomal RNA (18S rRNA) gene and to determine the factors associated with the presence of this protozoan. A cross-sectional descriptive study was conducted among 230 patients with periodontal disease, who visited the oral health center of Suranaree University of Technology Hospital, Thailand from 2021 to 2022. Dental plaque specimens were collected and examined to identify the presence of T. tenax using the PCR-based 18S rRNA gene. The occurrence of factors associated with T. tenax infection was analyzed by the chi-square test and binary logistic regression. The prevalence of T. tenax infection was 13.48% (31/230), in patients, including 96.77% (30/31) and 3.23% (1/31) in periodontitis and gingivitis patients, respectively. The presence of T. tenax was associated with periodontal disease (p<0.001) and the Periodontal Screening and Record (PSR) index (p=0.001). The significant risk factors for T. tenax infection were periodontitis (OR_adj=239.89, 95% CI=23.801-2417.746), no-underlying disease (OR_adj=0.31, 95% CI=0.099-0.942), and male sex (OR_adj=0.25, 95% CI=0.062-0.981). Dentists should be concerned about this oral protozoan in periodontitis patients. Furthermore, epidemiologic studies of T. tenax are still needed to investigate the mechanism of pathogenesis from T. tenax infection.

Most of the public health importance coronaviruses, such as Severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV) and SARS-CoV-2 are likely originated from bats and spread to humans through intermediate hosts; civet cats, dromedary camel and Malayan pangolin, respectively. SARS-CoV-2-like coronaviruses were detected in Thailand, which is neighbouring with Kelantan in East Coast Malaysia. To date, there is no report on the presence of public health concerns (SARS-CoV, SARS-CoV-2 and MERS-CoV) coronaviruses in bats from Malaysia. This study was aimed to elucidate the presence of these coronaviruses in bat samples from East Coast, Malaysia. A total of hundred seventy oropharyngeal swab samples were collected from three states of East Coast Malaysia. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was conducted based on partial 3' Untranslated region (3'UTR) or ORF10 gene and the products were sequenced. The sequences were compared with all coronavirus sequences from the National Center for Biotechnology Information-GenBank (NCBI-GenBank) using NCBI-Basic Local Alignment Search Tool (NCBI-BLAST) software. A phylogenetic tree was constructed to determine the genetic relationship among the detected coronaviruses with the reference coronaviruses from the NCBI-GenBank. Our results showed that SARSCoV-2-like viruses were present in 3% (5/170) of the bats from East Coast Malaysia that have 98-99% sequence identities and are genetically related to SARS-CoV-2 from humans. This finding indicates the presence of SARS-CoV-2-like viruses in bats from East Coast Malaysia that may become a public health concern in the future.

The susceptibility levels of Malaysian Aedes albopictus larvae sampled from several agricultural, fogging-free residential and dengue prone residential areas against different larvicides were evaluated using revised diagnostic doses derived from the 2xLC99 values of the reference strain. Upon 24-hour recovery period of WHO larval bioassay, incipient resistance was observed among Ae. albopictus larvae from rubber estates against fenitrothion (96.67% mortality) and permethin (97.00% mortality) while Ae. albopictus larvae from rice cultivation areas were moderately resistant to fenthion (94.33% mortality). Aedes albopictus larvae from dengue prone residential areas developed moderate to high resistance against dichlorodiphenyltrichloroethane (DDT), fenitrothion, fenthion, propoxur and permethrin (79.67% - 97.33% mortality). Moderate to high resistance were also demonstrated among all populations of Ae. albopictus larvae against temephos and chlorpyrifos (63.00% - 97.67% mortality). Except for Ae. albopictus larvae from oil palm plantations, all Ae. albopictus larval populations were also highly resistant to bendiocarb (65.67% - 89.67% mortality). Cross resistance between larvicides from similar and different insecticide classes were also revealed in this study. The use of revised diagnostic doses established from the local reference strain could reduce the possibility of underestimation or overestimation of the insecticide susceptibility status of field strain populations.

Beetles (Coleoptera) are known to constitute forensic evidence in medico-legal investigations as their presence can be used to date human remains in almost all decomposition stages. Many forensic studies focus on the successional colonization pattern of flies (Diptera); however, beetles have not so far been studied extensively for this aspect. A beetle of the genus Afromorgus Scholtz, 1986, A. chinensis (Boheman, 1858) (Scarabaeoidea: Trogidae), was found beneath a late decaying rabbit carcass at Paya Indah Wetland, Dengkil, Malaysia, for the first time. Both genus and species are already known to occur in Malaysia from literature.