Publications by authors named "Thom Do"

12 Publications

  • Page 1 of 1

First Molecular Detection of in Stray Dogs from Thailand.

Pathogens 2021 May 22;10(6). Epub 2021 May 22.

Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.

In southern Thailand, the increasingly growing population of stray dogs is a concern to public health and environmental safety because of the lack of medical attention and control. More importantly, these animals are considered reservoirs for many zoonotic pathogens. The objective of this study was to molecularly detect canine vector-borne pathogens, and to perform genetic characterization of present in stray dogs from southern Thailand. Blood samples were collected from 174 stray dogs in two provinces (Songkhla and Narathiwat) in southern Thailand. PCR analyses were executed using specific primers based on the spp. 18S rRNA gene, Internal transcribed spacer 1 (ITS1) region, citrate synthase (gltA) gene, spp. 18S rRNA gene and heat shock protein (groEL) gene. The most common canine vector-borne pathogen found infecting stray dogs in this study was (24.7%) followed by (14.9%), (8.0%), (6.3%), and (1.72%). Concurrent infection with more than one pathogen occurred in 72 cases. Phylogenetic analysis based on the ITS1 region and 18S rRNA gene revealed that the isolates from this study shared a large proportion of their identities with each other and with other reported genotypes from Asia. This study highlights the molecular detection of in dogs in Thailand for the first time and presents the genetic characterization by sequencing the ITS1 region and 18S rRNA gene of from Thailand. Follow-up studies are needed to elucidate the origin, distribution, and vectors of parasites circulating in dogs in Thailand, as well as to determine to what extent dogs are important reservoir hosts for zoonotic canine vector-borne disease infection in the studied area.
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http://dx.doi.org/10.3390/pathogens10060639DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8224757PMC
May 2021

Molecular Detection of Tick-Borne Pathogens in Stray Dogs and sensu lato Ticks from Bangkok, Thailand.

Pathogens 2021 May 6;10(5). Epub 2021 May 6.

Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.

Canine tick-borne pathogens (CTBPs) such as , , , and are important pathogens in dogs worldwide. sensu lato, the main vector of several CTBPs, is the most common tick species found on dogs in Thailand. The present study identified CTBPs in dogs and ticks infested dogs. Samples (360 dog blood samples and 85 individual ticks) were collected from stray dogs residing in 37 temples from 24 districts in Bangkok and screened for CTBPs using molecular techniques. The most common CTBP found infecting dogs in this study was (38.3%) followed by (34.2%), (19.7%), (18.1%), and (13.9%), respectively. Furthermore, (22.4%) was the most common CTBP in ticks followed by (18.8%), (9.4%), (5.9%), and (2.4%), respectively. The detection of CTBPs from the present study highlights the potential risk of infections that may occur in stray dogs and their ticks residing in Bangkok temples. These findings underline the importance of performing active surveys to understand the complexity of distributions of CTBPs in dogs and their ticks in Thailand.
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http://dx.doi.org/10.3390/pathogens10050561DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8148546PMC
May 2021

Evaluation of hematological alteration of vector-borne pathogens in cats from Bangkok, Thailand.

BMC Vet Res 2021 Jan 18;17(1):28. Epub 2021 Jan 18.

Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, 10900, Bangkok, Thailand.

Background: Cats can be carriers of infected arthropods and be infected with several vector-borne pathogens (VBPs) but there is limited knowledge about their pathogenic role in cats. This study aimed to assess the prevalence of some feline vector-borne agents by molecular technique and to characterize the hematological findings associated with these infections in a cat population from Bangkok Thailand.

Results: PCR was positive with at least one pathogen in 237 out of 372 subjects (63.7%), with prevalence of 39.5% (147/372) for Babesia spp., 36.9% (137/372) for hemoplasmas and 3.2% (12/372) for Hepatozoon spp. The cats older than 1 year were at significantly greater risk for VBPs infection (P = 0.001; OR = 1.43; 95% CI: 1.12 - 1.81) and hemoplasmas infection (χ2 = 10.8, df = 1; P < 0.0001; OR = 2.45; 95% CI: 1.49 - 4.01). A significant association between hematological findings and hemoplasma infection were identified in the present study. Besides, VBPs infection revealed more frequent in male cats (χ2= 6.38, df = 1, P = 0.01). Macrocytic hypochromic type of anemia was observed in cats infested with blood-sucking arthropods compared to the non-infested cats presented.

Conclusions: The current study confirmed that Babesia, Hepatozoon and hemoplasmas had infected semi-domesticated cats in Bangkok, Thailand, with Babesia and hemoplasmas being dominant in prevalence. Some hematological findings were significantly associated with cats infected with vector-borne pathogens in this study including leukocyte count and platelets count that may help support veterinary technicians in diagnosis and appropriate treatment. Campaigns of VBPs monitoring in Bangkok emphasizing on the investigation of vectors and possible routes of the infection in animals should be conducted to prevent the transmission of the pathogens.
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http://dx.doi.org/10.1186/s12917-020-02737-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7812637PMC
January 2021

A case of Trypanosoma evansi in a German Shepherd dog in Vietnam.

Parasitol Int 2021 Feb 12;80:102198. Epub 2020 Sep 12.

Department of Parasitology, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 12406, Viet Nam.

A 2.5-year-old male German Shepherd was presented to a private veterinary clinic in Hanoi, Vietnam showing anorexia, weakness, lethargy, reluctant to go for walks with a recent history of intermittent fever. Clinical examination of the dog showed pale mucous membrane, impaired eyesight, edema of the back legs. Complete blood count revealed severe anemia; red blood cell 3.8 × 10/l, hemoglobin 8.7 g/dl, hematocrit 26.4%, associated with thrombocytopenia 145 × 10/l. Biochemical analysis showed a moderate increase of alanine transaminase (150.7 UI/l) and alkaline phosphatase activities (266 UI/I) with mild hypoglycemia (71.46 mg/dl). Trypanosoma evansi was observed in Giemsa-stained blood smears under microscopic observation which was confirmed by PCR. This is the first report of canine trypanosomiasis caused by T. evansi in Vietnam.
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http://dx.doi.org/10.1016/j.parint.2020.102198DOI Listing
February 2021

Molecular detection of pathogens in ticks and fleas collected from companion dogs and cats in East and Southeast Asia.

Parasit Vectors 2020 Aug 15;13(1):420. Epub 2020 Aug 15.

Dipartimento di Medicina Veterinaria, Università degli Studi di Bari, Bari, Italy.

Background: Ticks and fleas are considered amongst the most important arthropod vectors of medical and veterinary concern due to their ability to transmit pathogens to a range of animal species including dogs, cats and humans. By sharing a common environment with humans, companion animal-associated parasitic arthropods may potentially transmit zoonotic vector-borne pathogens (VBPs). This study aimed to molecularly detect pathogens from ticks and fleas from companion dogs and cats in East and Southeast Asia.

Methods: A total of 392 ticks and 248 fleas were collected from 401 infested animals (i.e. 271 dogs and 130 cats) from China, Taiwan, Indonesia, Malaysia, Singapore, Thailand, the Philippines and Vietnam, and molecularly screened for the presence of pathogens. Ticks were tested for Rickettsia spp., Anaplasma spp., Ehrlichia spp., Babesia spp. and Hepatozoon spp. while fleas were screened for the presence of Rickettsia spp. and Bartonella spp.

Result: Of the 392 ticks tested, 37 (9.4%) scored positive for at least one pathogen with Hepatozoon canis being the most prevalent (5.4%), followed by Ehrlichia canis (1.8%), Babesia vogeli (1%), Anaplasma platys (0.8%) and Rickettsia spp. (1%) [including Rickettsia sp. (0.5%), Rickettsia asembonensis (0.3%) and Rickettsia felis (0.3%)]. Out of 248 fleas tested, 106 (42.7%) were harboring at least one pathogen with R. felis being the most common (19.4%), followed by Bartonella spp. (16.5%), Rickettsia asembonensis (10.9%) and "Candidatus Rickettsia senegalensis" (0.4%). Furthermore, 35 Rhipicephalus sanguineus ticks were subjected to phylogenetic analysis, of which 34 ticks belonged to the tropical and only one belonged to the temperate lineage (Rh. sanguineus (sensu stricto)).

Conclusion: Our data reveals the circulation of different VBPs in ticks and fleas of dogs and cats from Asia, including zoonotic agents, which may represent a potential risk to animal and human health.
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http://dx.doi.org/10.1186/s13071-020-04288-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7429691PMC
August 2020

Genetic characterization and risk factors for feline hemoplasma infection in semi-domesticated cats in Bangkok, Thailand.

Vet World 2020 May 23;13(5):975-980. Epub 2020 May 23.

Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand.

Background And Aim: Stray cats are a reservoir for various zoonotic diseases relevant to public health in Thailand. The vector-borne infection, hemoplasmosis, also known as infectious anemia, is one such disease carried by domestic and wild felids. This study focuses on molecular characterization and phylogenetic analysis of hemoplasma in semi-domesticated cats in Bangkok, Thailand.

Materials And Methods: In total, 473 blood samples were collected from 53 temple communities in 34 metropolitan districts and assayed using polymerase chain reaction (PCR) to amplify partial 16S rRNA genes for hemoplasma detection. Risk factors for hemoplasma infection (gender, age, free-roaming, and ectoparasite exposure) were analyzed using Chi-square tests, logistic regression, and odds ratios (OR) with 95% confidence intervals (95% CI) using R software (version 3.6.1). A phylogenetic tree was established from genetic characterization of hemoplasmas.

Results: In total, 180 samples (38.05%) were positive for hemoplasma. Of half of the positive sequenced samples, 83.33% were infected with Mycoplasma haemominutum (), 13.33% with (), and 3.33% with Mycoplasma turicensis (). Cats over 5 years old were more likely to be infected than younger cats (p<0.005, OR=3.8, 95% CI=1.64-4.78). Cats were diagnosed as positive based on PCR assays in 97% (33/34) of districts surveyed. The phylogenetic tree showed two majority clusters with three clades of feline hemotropic mycoplasma.

Conclusions: Overall, the survey shows the prevalence (38.05%) and distribution of feline hemoplasma in semi-domesticated cats. This information will contribute to effective prevention and control strategies to minimize infections by feline vector-borne pathogens in Thailand.
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http://dx.doi.org/10.14202/vetworld.2020.975-980DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311864PMC
May 2020

A Refined Simple First-Order Shear Deformation Theory for Static Bending and Free Vibration Analysis of Advanced Composite Plates.

Materials (Basel) 2019 Jul 26;12(15). Epub 2019 Jul 26.

Faculty of Mechanical Engineering, Le Quy Don Technical University, Hanoi City 100000, Vietnam.

A refined simple first-order shear deformation theory is developed to investigate the static bending and free vibration of advanced composite plates such as functionally graded plates. By introducing the new distribution shape function, the transverse shear strain and shear stress have a parabolic distribution across the thickness of the plates, and they equal zero at the surfaces of the plates. Hence, the new refined theory needs no shear correction factor. The Navier solution is applied to investigate the static bending and free vibration of simply supported advanced composite plates. The proposed theory shows an improvement in calculating the deflections and frequencies of advanced composite plates. The formulation and transformation of the present theory are as simple as the simple first-order shear deformation. The comparisons of deflection, axial stresses, transverse shear stresses, and frequencies of the plates obtained by the proposed theory with published results of different theories are carried out to show the efficiency and accuracy of the new theory. In addition, some discussions on the influence of various parameters such as the power-law index, the slenderness ratio, and the aspect ratio are carried out, which are useful for the design and testing of advanced composite structures.
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http://dx.doi.org/10.3390/ma12152385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6695951PMC
July 2019

An Efficient Beam Element Based on Quasi-3D Theory for Static Bending Analysis of Functionally Graded Beams.

Materials (Basel) 2019 Jul 8;12(13). Epub 2019 Jul 8.

Department of Mechanics, Le Quy Don Technical University, Hanoi City 100000, Vietnam.

In this paper, a 2-node beam element is developed based on Quasi-3D beam theory and mixed formulation for static bending of functionally graded (FG) beams. The transverse shear strains and stresses of the proposed beam element are parabolic distributions through the thickness of the beam and the transverse shear stresses on the top and bottom surfaces of the beam vanish. The proposed beam element is free of shear-looking without selective or reduced integration. The material properties of the functionally graded beam are assumed to vary according to the power-law index of the volume fraction of the constituents through the thickness of the beam. The numerical results of this study are compared with published results to illustrate the accuracy and convenience rate of the new beam element. The influence of some parametrics on the bending behavior of FGM beams is investigated.
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http://dx.doi.org/10.3390/ma12132198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6651834PMC
July 2019

New Numerical Results from Simulations of Beams and Space Frame Systems with a Tuned Mass Damper.

Materials (Basel) 2019 Apr 23;12(8). Epub 2019 Apr 23.

Faculty of Mechanical Engineering, Le Quy Don Technical University, Ha Noi City 100000, Vietnam.

In working processes, mechanical systems are often affected by both internal and external forces, which are the cause of the forced vibrations of the structures. They can be destroyed if the amplitude of vibration reaches a high enough value. One of the most popular ways to reduce these forced vibrations is to attach tuned mass damper (TMD) devices, which are commonly added at the maximum displacement point of the structures. This paper presents the computed results of the free vibration and the vibration response of the space frame system under an external random load, which is described as a stationary process with white noise. Static and dynamic equations are formed through the finite element method. In addition, this work also establishes artificial neural networks (ANNs) in order to predict the vibration response of the first frequencies of the structure. Numerical studies show that the data set of the TMD device strongly affects the first frequencies of the mechanical system, and the proposed artificial intelligence (AI) model can predict exactly the vibration response of the first frequencies of the structure. For the forced vibration problem, we can find optimal parameters of the TMD device and thus obtain minimum displacements of the structure. The results of this work can be used as a reference when applying this type of structure to TMD devices.
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http://dx.doi.org/10.3390/ma12081329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6515429PMC
April 2019

Research on the Buckling Behavior of Functionally Graded Plates with Stiffeners Based on the Third-Order Shear Deformation Theory.

Materials (Basel) 2019 Apr 17;12(8). Epub 2019 Apr 17.

Faculty of Mechanical Engineering, Le Quy Don Technical University, Hanoi City 100000, Vietnam.

This paper presents a finite element formulation to study the mechanical buckling of stiffened functionally graded material (FGM) plates. The approach is based on a third-order shear deformation theory (TSDT) introduced by Guangyu Shi. The material properties of the plate were assumed to be varied in the thickness direction by a power law distribution, but the material of the stiffener was the same as that of the one of the bottom surface where the stiffener was placed. A parametric study was carried out to highlight the effect of material distribution, the thickness-to-width ratio, and stiffener parameters on the buckling characteristics of the stiffened FGM plates. Numerical results showed that the addition of stiffener to the FGM plate could significantly reduce the weight of the FGM plate but that both the FGM plates with and without stiffener had equally high strength in the same boundary condition and compression loading.
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http://dx.doi.org/10.3390/ma12081262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6515214PMC
April 2019

A Finite Element Model for Dynamic Analysis of Triple-Layer Composite Plates with Layers Connected by Shear Connectors Subjected to Moving Load.

Materials (Basel) 2019 Feb 16;12(4). Epub 2019 Feb 16.

Faculty of Mechanical Engineering, Le Quy Don Technical University, Ha Noi 100000, Vietnam.

Triple-layered composite plates are created by joining three composite layers using shear connectors. These layers, which are assumed to be always in contact and able to move relatively to each other during deformation, could be the same or different in geometric dimensions and material. They are applied in various engineering fields such as ship-building, aircraft wing manufacturing, etc. However, there are only a few publications regarding the calculation of this kind of plate. This paper proposes novel equations, which utilize Mindlin's theory and finite element modelling to simulate the forced vibration of triple-layered composite plates with layers connected by shear connectors subjected to a moving load. Moreover, a Matlab computation program is introduced to verify the reliability of the proposed equations, as well as the influence of some parameters, such as boundary conditions, the rigidity of the shear connector, thickness-to-length ratio, and the moving load velocity on the dynamic response of the composite plate.
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http://dx.doi.org/10.3390/ma12040598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6416568PMC
February 2019

A New Beam Model for Simulation of the Mechanical Behaviour of Variable Thickness Functionally Graded Material Beams Based on Modified First Order Shear Deformation Theory.

Materials (Basel) 2019 Jan 28;12(3). Epub 2019 Jan 28.

Center of Excellence for Automation and Precision Mechanical Engineering, Nguyen Tat Thanh University, Ho Chi Minh City 700000, Vietnam.

There are many beam models to simulate the variable thickness functionally graded material (FGM) beam, each model has advantages and disadvantages in computer aided engineering of the mechanical behavior of this beam. In this work, a new model of beam is presented to study the mechanical static bending, free vibration, and buckling behavior of the variable thickness functionally graded material beams. The formulations are based on modified first order shear deformation theory and interpolating polynomials. This new beam model is free of shear-locking for both thick and thin beams, is easy to apply in computation, and has efficiency in simulating the variable thickness beams. The effects of some parameters, such as the power-law material index, degree of non-uniformity index, and the length-to-height ratio, on the mechanical behavior of the variable thickness FGM beam are considered.
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http://dx.doi.org/10.3390/ma12030404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384869PMC
January 2019
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