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Huggins LG, Koehler AV, Gasser RB, Traub RJ. Advanced approaches for the diagnosis and chemoprevention of canine vector-borne pathogens and parasites-Implications for the Asia-Pacific region and beyond. ADVANCES IN PARASITOLOGY 2023; 120:1-85. [PMID: 36948727 DOI: 10.1016/bs.apar.2022.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Vector-borne pathogens (VBPs) of canines are a diverse range of infectious agents, including viruses, bacteria, protozoa and multicellular parasites, that are pernicious and potentially lethal to their hosts. Dogs across the globe are afflicted by canine VBPs, but the range of different ectoparasites and the VBPs that they transmit predominate in tropical regions. Countries within the Asia-Pacific have had limited prior research dedicated to exploring the epidemiology of canine VBPs, whilst the few studies that have been conducted show VBP prevalence to be high, with significant impacts on dog health. Moreover, such impacts are not restricted to dogs, as some canine VBPs are zoonotic. We reviewed the status of canine VBPs in the Asia-Pacific, with particular focus on nations in the tropics, whilst also investigating the history of VBP diagnosis and examining recent progress in the field, including advanced molecular methods, such as next-generation sequencing (NGS). These tools are rapidly changing the way parasites are detected and discovered, demonstrating a sensitivity equal to, or exceeding that of, conventional molecular diagnostics. We also provide a background to the armoury of chemopreventive products available for protecting dogs from VBP. Here, field-based research within high VBP pressure environments has underscored the importance of ectoparasiticide mode of action on their overall efficacy. The future of canine VBP diagnosis and prevention at a global level is also explored, highlighting how evolving portable sequencing technologies may permit diagnosis at point-of-care, whilst further research into chemopreventives will be essential if VBP transmission is to be effectively controlled.
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Affiliation(s)
- Lucas G Huggins
- Faculty of Veterinary and Agricultural Sciences, Melbourne Veterinary School, The University of Melbourne, Parkville, VIC, Australia.
| | - Anson V Koehler
- Faculty of Veterinary and Agricultural Sciences, Melbourne Veterinary School, The University of Melbourne, Parkville, VIC, Australia
| | - Robin B Gasser
- Faculty of Veterinary and Agricultural Sciences, Melbourne Veterinary School, The University of Melbourne, Parkville, VIC, Australia
| | - Rebecca J Traub
- Faculty of Veterinary and Agricultural Sciences, Melbourne Veterinary School, The University of Melbourne, Parkville, VIC, Australia
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Nguyen VL, Dantas-Torres F, Otranto D. Canine and feline vector-borne diseases of zoonotic concern in Southeast Asia. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2021. [PMCID: PMC8906074 DOI: 10.1016/j.crpvbd.2020.100001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Dogs and cats are important hosts and reservoirs of many viral, bacterial, protozoal, and helminthic pathogens transmitted by arthropods, including some of zoonotic concern. By sharing the same environment, these companion animals play an important role in the transmission of zoonotic pathogens to humans in various regions and socioeconomic contexts. While canine and feline vector-borne diseases (VBD) are of major concern in wealthy regions (e.g. Europe and North America), less attention has been received in developing countries such as those in Southeast Asia (SEA). This review provides summarized and updated information on canine and feline VBD with emphasis on those of zoonotic concern in SEA. Of these, zoonotic bacteria (i.e. Bartonella henselae, Bartonella clarridgeiae, and Rickettsia felis) and filarial nematodes (i.e. Brugia malayi, Dirofilaria repens, and Dirofilaria immitis) stand out as the most important in veterinary and human medicine. Additionally, the recent finding of Leishmania infantum in dogs in SEA raised more concerns about the spreading of this zoonotic agent in this region. Further epidemiological surveys, especially in countries with extremely scant information such as Cambodia, Laos, Myanmar, and Timor-Leste are advocated. Additionally, effective control measures of canine and feline VBD as well as their arthropod vectors should be simultaneously performed for the management of zoonotic infections. Many canine and feline vector-borne infections affect animals and humans in Southeast Asia. Ticks, fleas and mosquitoes are the most common vectors transmitting pathogens to dogs, cats and humans in Southeast Asia. Bartonella henselae, Rickettsia felis and Dirofilaria repens are of concern to human health in this region. Collaboration between governments and researchers is encouraged for a better management of vector-borne diseases.
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Affiliation(s)
- Viet-Linh Nguyen
- Department of Veterinary Medicine, University of Bari, Bari, Italy
| | - Filipe Dantas-Torres
- Department of Veterinary Medicine, University of Bari, Bari, Italy
- Department of Immunology, Aggeu Magalhães Institute, Recife, Brazil
| | - Domenico Otranto
- Department of Veterinary Medicine, University of Bari, Bari, Italy
- Faculty of Veterinary Sciences, Bu-Ali Sina University, Hamedan, Iran
- Corresponding author. Department of Veterinary Medicine, University of Bari, Bari, Italy.
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Satjawongvanit H, Phumee A, Tiawsirisup S, Sungpradit S, Brownell N, Siriyasatien P, Preativatanyou K. Molecular Analysis of Canine Filaria and Its Wolbachia Endosymbionts in Domestic Dogs Collected from Two Animal University Hospitals in Bangkok Metropolitan Region, Thailand. Pathogens 2019; 8:pathogens8030114. [PMID: 31362350 PMCID: PMC6789508 DOI: 10.3390/pathogens8030114] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 11/16/2022] Open
Abstract
Canine filariasis is caused by several nematode species, such as Dirofilaria immitis, Dirofilaria repens, Brugia pahangi, Brugia malayi, and Acanthocheilonema reconditum. Zoonotic filariasis is one of the world's neglected tropical diseases. Since 2000, the World Health Organization (WHO) has promoted a global filarial eradication program to eliminate filariasis by 2020. Apart from vector control strategies, the infection control of reservoir hosts is necessary for more effective filariasis control. In addition, many studies have reported that Wolbachia is necessary for the development, reproduction, and survival of the filarial nematode. Consequently, the use of antibiotics to kill Wolbachia in nematodes has now become an alternative strategy to control filariasis. Previously, a case of subconjunctival dirofilariasis caused by Dirofilaria spp. has been reported in a woman who resides in the center of Bangkok, Thailand. Therefore, our study aimed to principally demonstrate the presence of filarial nematodes and Wolbachia bacteria in blood collected from domestic dogs from the Bangkok Metropolitan Region, Thailand. A total of 57 blood samples from dogs with suspected dirofilariasis who had visited veterinary clinics in Bangkok were collected. The investigations for the presence of microfilaria were carried out by using both microscopic and molecular examinations. PCR was used as the molecular detection method for the filarial nematodes based on the COI and ITS1 regions. The demonstration of Wolbachia was performed using PCR to amplify the FtsZ gene. All positive samples by PCR were then cloned and sequenced. The results showed that the filarial nematodes were detected in 16 samples (28.07%) using microscopic examinations. The molecular detection of filarial species using COI-PCR revealed that 50 samples (87.72%) were positive; these consisted of 33 (57.89%), 13 (22.81%), and 4 (7.02%) samples for D. immitis, B. pahangi, and B. malayi, respectively. While the ITS1-PCR showed that 41 samples (71.93%) were positive-30 samples (52.63%) were identified as containing D. immitis and 11 samples (19.30%) were identified to have B. pahangi, whereas B. malayi was not detected. Forty-seven samples (82.45%) were positive for Wolbachia DNA and the phylogenetic tree of all positive Wolbachia was classified into the supergroup C clade. This study has established fundamental data on filariasis associated with Wolbachia infection in domestic dogs in the Bangkok Metropolitan Region. An extensive survey of dog blood samples would provide valuable epidemiologic data on potential zoonotic filariasis in Thailand. In addition, this information could be used for the future development of more effective prevention and control strategies for canine filariasis in Thailand.
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Affiliation(s)
| | - Atchara Phumee
- Vector Biology and Vector Borne Disease Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
- Thai Red Cross Emerging Infectious Disease-Health Science Centre, World Health Organization Collaborating Centre for Research and Training on Viral Zoonoses, Chulalongkorn Hospital, Bangkok 10330, Thailand
| | - Sonthaya Tiawsirisup
- Veterinary Parasitology Unit, Department of Veterinary Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Sivapong Sungpradit
- Department of Pre-clinic and Applied Animal Science, Faculty of Veterinary Science, Mahidol University, Salaya, Nakhon Pathom 73170, Thailand
| | - Narisa Brownell
- Vector Biology and Vector Borne Disease Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
| | - Padet Siriyasatien
- Vector Biology and Vector Borne Disease Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
| | - Kanok Preativatanyou
- Vector Biology and Vector Borne Disease Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand.
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Sanpool O, Tantrawatpan C, Thanchomnang T, Janwan P, Intapan PM, Rodpai R, Lulitanond V, Taweethavonsawat P, Maleewong W. Pyrosequencing Using SL and 5S rRNA as Molecular Markers for Identifying Zoonotic Filarial Nematodes in Blood Samples and Mosquitoes. Vector Borne Zoonotic Dis 2016; 16:326-33. [PMID: 27008279 DOI: 10.1089/vbz.2015.1914] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUNDS Lymphatic filariasis is principally caused by Wuchereria bancrofti, and Brugia malayi. The other two filarial nematode species, Brugia pahangi and Dirofilaria immitis, possibly cause human zoonotic diseases. METHODS We propose the development of a PCR assay linked with DNA pyrosequencing as a rapid tool to identify W. bancrofti, B. malayi, B. pahangi, and D. immitis in blood samples and mosquitoes. Primers targeting the fragment of the 5S ribosomal RNA and spliced leader sequences were newly designed and developed to identify these four filarial nematodes. Analytical sensitivity and specificity were evaluated. RESULTS Pyrosequencing determination of nucleotide variations within 36 nucleotides for B. malayi and B. pahangi, and 32 nucleotides for W. bancrofti and D. immitis is sufficient for differentiation of those filarial nematodes, and for detection of intraspecies genetic variation of B. malayi. This analysis could detect a single B. malayi, B. pahangi, W. bancrofti, and D. immitis microfilaria in blood samples. CONCLUSIONS Overall, the PCR-linked pyrosequencing-based method was faster than direct sequencing and less expensive than real-time PCR or direct sequencing. This is the possibility of choice that can be applied in a high-throughput platform for identification and surveillance of reservoirs and vectors infected with lymphatic filaria in endemic areas.
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Affiliation(s)
- Oranuch Sanpool
- 1 Department of Parasitology, Faculty of Medicine, Khon Kaen University , Khon Kaen, Thailand .,2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand .,3 Faculty of Medicine, Mahasarakham University , Mahasarakham, Thailand
| | - Chairat Tantrawatpan
- 2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand .,4 Division of Cell Biology, Department of Preclinical Sciences, Faculty of Medicine, Thammasat University , Pathum Thani, Thailand
| | - Tongjit Thanchomnang
- 2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand .,3 Faculty of Medicine, Mahasarakham University , Mahasarakham, Thailand
| | - Penchom Janwan
- 2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand .,5 Department of Medical Technology, School of Allied Health Sciences and Public Health, Walailak University , Nakhon Si Thammarat, Thailand
| | - Pewpan M Intapan
- 1 Department of Parasitology, Faculty of Medicine, Khon Kaen University , Khon Kaen, Thailand .,2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand
| | - Rutchanee Rodpai
- 1 Department of Parasitology, Faculty of Medicine, Khon Kaen University , Khon Kaen, Thailand .,2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand
| | - Viraphong Lulitanond
- 2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand .,6 Department of Microbiology, Faculty of Medicine, Khon Kaen University , Khon Kaen, Thailand
| | - Piyanan Taweethavonsawat
- 7 Parasitology Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University , Bangkok, Thailand
| | - Wanchai Maleewong
- 1 Department of Parasitology, Faculty of Medicine, Khon Kaen University , Khon Kaen, Thailand .,2 Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University , Khon Kaen, Thailand
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Thanchomnang T, Intapan PM, Tantrawatpan C, Lulitanond V, Chungpivat S, Taweethavonsawat P, Kaewkong W, Sanpool O, Janwan P, Choochote W, Maleewong W. Rapid detection and identification of Wuchereria bancrofti, Brugia malayi, B. pahangi, and Dirofilaria immitis in mosquito vectors and blood samples by high resolution melting real-time PCR. THE KOREAN JOURNAL OF PARASITOLOGY 2013; 51:645-50. [PMID: 24516268 PMCID: PMC3916452 DOI: 10.3347/kjp.2013.51.6.645] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 08/03/2013] [Accepted: 10/11/2013] [Indexed: 12/02/2022]
Abstract
A simple, rapid, and high-throughput method for detection and identification of Wuchereria bancrofti, Brugia malayi, Brugia pahangi, and Dirofilaria immitis in mosquito vectors and blood samples was developed using a real-time PCR combined with high-resolution melting (HRM) analysis. Amplicons of the 4 filarial species were generated from 5S rRNA and spliced leader sequences by the real-time PCR and their melting temperatures were determined by the HRM method. Melting of amplicons from W. bancrofti, B. malayi, D. immitis, and B. pahangi peaked at 81.5±0.2℃, 79.0±0.3℃, 76.8±0.1℃, and 79.9±0.1℃, respectively. This assay is relatively cheap since it does not require synthesis of hybridization probes. Its sensitivity and specificity were 100%. It is a rapid and technically simple approach, and an important tool for population surveys as well as molecular xenomonitoring of parasites in vectors.
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Affiliation(s)
- Tongjit Thanchomnang
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Faculty of Medicine, Mahasarakham University, Mahasarakham 44000, Thailand
| | - Pewpan M Intapan
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Chairat Tantrawatpan
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Division of Cell Biology, Department of Preclinical Sciences, Faculty of Medicine, Thammasat University, Rangsit Campus, Pathum Thani 12121, Thailand
| | - Viraphong Lulitanond
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Sudchit Chungpivat
- Parasitology Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Piyanan Taweethavonsawat
- Parasitology Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Worasak Kaewkong
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Biochemistry, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand
| | - Oranuch Sanpool
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Penchom Janwan
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Wej Choochote
- Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Wanchai Maleewong
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. ; Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
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Wongkamchai S, Monkong N, Mahannol P, Taweethavonsawat P, Loymak S, Foongladda S. Rapid detection and identification of Brugia malayi, B. pahangi, and Dirofilaria immitis by high-resolution melting assay. Vector Borne Zoonotic Dis 2012. [PMID: 23199268 DOI: 10.1089/vbz.2012.0971] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Human lymphatic filariasis is caused by filarial worms such as Brugia malayi for which the major reservoir is domestic cats. However, domestic cats or dogs also carry nonhuman filaria such as Brugia pahangi and Dirofilaria immitis. We have developed a single-tube, real-time PCR with a high-resolution melting (HRM) analysis assay for detection and identification of B. malayi, B. pahangi, and D. immitis in blood samples. The designated primer pair in the PCR can amplify a 114-bp region of mitochondrial 12S rRNA genes of these filarial worms. Subsequently, the HRM assay showed a specific melting temperature for each species. The assay showed the highest sensitivity and specificity in comparison with DNA sequences after assessment with 34 cat and 14 dog blood samples. This assay could be helpful for epidemiological studies of reservoirs and vectors.
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Affiliation(s)
- Sirichit Wongkamchai
- Department of Parasitology, Faculty of Medicine Siriraj Hospital, Bangkok, Thailand
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Thanchomnang T, Intapan P, Sri-Aroon P, Lulitanond V, Janwan P, Sanpool O, Maleewong W. Molecular detection of Schistosoma japonicum in infected snails and mouse faeces using a real-time PCR assay with FRET hybridisation probes. Mem Inst Oswaldo Cruz 2012; 106:831-6. [PMID: 22124555 DOI: 10.1590/s0074-02762011000700008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 09/06/2011] [Indexed: 11/22/2022] Open
Abstract
A real-time polymerase chain reaction (PCR) assay with fluorescence resonance energy transfer (FRET) hybridisation probes combined with melting curve analysis was developed to detect Schistosoma japonicum in experimentally infected snails and in faecal samples of infected mice. This procedure is based on melting curve analysis of a hybrid between an amplicon from the S. japonicum internal transcribed spacer region 2 sequence, which is a 192-bp S. japonicum-specific sequence, and fluorophore-labelled specific probes. Real-time FRET PCR could detect as little as a single cercaria artificially introduced into a pool of 10 non-infected snails and a single egg inoculated in 100 mg of non-infected mouse faeces. All S. japonicum-infected snails and all faecal samples from infected mice were positive. Non-infected snails, non-infected mouse faeces and genomic DNA from other parasites were negative. This assay is rapid and has potential for epidemiological S. japonicum surveys in snails, intermediate hosts and faecal samples of final hosts.
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Affiliation(s)
- Tongjit Thanchomnang
- Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, 40002 Khon Kaen, Thailand
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Tantrawatpan C, Intapan PM, Thanchomnang T, Lulitanond V, Boonmars T, Wu Z, Morakote N, Maleewong W. Differential detection of Trichinella papuae, T. spiralis and T. pseudospiralis by real-time fluorescence resonance energy transfer PCR and melting curve analysis. Vet Parasitol 2011; 185:210-5. [PMID: 22037059 DOI: 10.1016/j.vetpar.2011.09.043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/26/2011] [Accepted: 09/30/2011] [Indexed: 11/17/2022]
Abstract
Trichinellosis caused by nematodes of Trichinella spp. is a zoonotic foodborne disease. Three Trichinella species of the parasite including Trichinella spiralis, Trichinella papuae and Trichinella pseudospiralis, have been etiologic agents of human trichinellosis in Thailand. Definite diagnosis of this helminthiasis is based on a finding of the Trichinella larva (e) in a muscle biopsy. The parasite species or genotype can be determined using molecular methods, e.g., polymerase chain reaction (PCR). This study has utilized real-time fluorescence resonance energy transfer PCR (real-time FRET PCR) and a melting curve analysis for the differential diagnosis of trichinellosis. Three common Trichinella species in Thailand were studied using one set of primers and fluorophore-labeled hybridization probes specific for the small subunit of the mitochondrial ribosomal RNA gene. Using fewer than 35 cycles as the cut-off for positivity and using different melting temperatures (T(m)), this assay detected T. spiralis, T. papuae and T. pseudospiralis in muscle tissue and found the mean T(m) ± SD values to be 51.79 ± 0.06, 66.09 ± 0.46 and 51.46 ± 0.09, respectively. The analytical sensitivity of the technique enabled the detection of a single Trichinella larva of each species, and the detection limit for the target DNA sequence was 16 copies of positive control plasmid. A test of the technique's analytical specificity showed no fluorescence signal for a panel of 19 non-Trichinella parasites or for human and mouse genomic DNA. Due to the sensitivity and specificity of the detection of these Trichinella species, as well as the fast and high-throughput nature of these tools, this method has application potential in differentiating non-encapsulated larvae of T. papuae from T. spiralis and T. pseudospiralis in tissues of infected humans and animals.
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Affiliation(s)
- Chairat Tantrawatpan
- Research and Diagnostic Center for Emerging Infectious Diseases, Khon Kaen University, Khon Kaen 40002, Thailand
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Abstract
Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.
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