Aya Yajima - Academia.edu (original) (raw)

Papers by Aya Yajima

Background: A mathematical model based on the Markov methodology to predict the change in prevale... more Background: A mathematical model based on the Markov methodology to predict the change in prevalence of soil-transmitted helminth (STH) infections during public health control activities is not available, but would be an extremely efficient planning tool. Method: We used the parasitological data collected during a deworming and iron supplementation programme for women of child-bearing age conducted in Vietnam between 2006 and 2011 to develop a Markov transition probability model. The transition probabilities were calculated from the observed changes in prevalence in the different classes of intensity for each STH species during the first year of intervention. The model was then developed and used to estimate the prevalence in year 2, 3, 4 and 5 for each STH species and for 'any STH infection'. The prevalence predicted by the model was then compared with the prevalence observed at different times during programme implementation. Results: The comparison between the model-predicted prevalence and the observed prevalence proved a good fit of the model. Conclusions: We consider the Markov transition probability model to be a promising method of predicting changes in STH prevalence during control efforts. Further research to validate the model with observed data in different geographical and epidemiological settings is suggested to refine the prediction model.

Japanese Dental Science Review, 2008

International Journal of Oral and Maxillofacial Surgery, 2007

Journal of Cranio-maxillofacial Surgery, 2008

Objective: Extensive mandibular reconstructions using internal distraction devices which we devel... more Objective: Extensive mandibular reconstructions using internal distraction devices which we developed for transporting bone are shown. Methods: The distraction device comprises a bridging reconstruction plate, brackets with miniplates, traction mechanisms, and traction wire. Activation of the traction mechanism pulls the wires connected to the bracket, which then slides and carries the transport disc along a rail. The cylinder sleeve of the traction mechanism is passed through the skin in the retrogonial area, and the entire device except for a part of the traction mechanism remains inside the body. Four (59-, 61-, 38-, and 61-year-old) patients had segmental defects because of tumor removal. Segmental osteotomies were made to provide 1.5-cm transport discs. The distraction device was fixed to the mandible as simulated. After a 7-day latency period, the device was activated at a rate of 0.5 mm twice a day. Transport discs moved with the brackets sliding on the rails 44 mm + 44 mm (bilaterally), 80 mm, 51 mm, and 33 mm + 41 mm in the respective patients. At the end of distraction the traction mechanisms were removed, leaving only the other components during the consolidation period. Results: Series of panoramic radiograms after the end of distraction showed a segment of regenerated bone in the distracted zone. The regenerated bone was achieved with trifocal and bifocal distraction osteogenesis. Conclusion: The segmental defects of the mandible were reconstructed with the bone transport distraction osteogenesis using the internal devices. This method enables extensive mandibular reconstruction without vascularised free bone graft.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2012

The integration of vertical control programmes of neglected tropical diseases (NTDs) aims to cont... more The integration of vertical control programmes of neglected tropical diseases (NTDs) aims to contain operational cost, simplify the application of the control measures and further extend the coverage of interventions. The Preventive Chemotherapy and Transmission Control (PCT) databank was established by the WHO to facilitate access and sharing of information from national programmes with stakeholders involved in NTD control. The PCT databank contains compilations of historical and current information on disease-specific epidemiological situations, the geographical overlapping of NTDs and progress of control activities in all the NTD-endemic countries. A summary of country-specific epidemiological maps and the progress of control activities are available from the online PCT databank and the Country Profiles. Annual progress of preventive chemotherapy interventions targeting specific NTDs is reported in the Weekly Epidemiological Record (WER) published annually for each disease target...

The Bulletin of Tokyo Dental College, 2006

Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial re... more Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial region have recently become commercially available. The newly-developed CBCT system, CB Throne (Hitachi Medical Corp., Tokyo), is characterized by a number of features such as low dose, sub-millimeter spatial resolution, and a small footprint. This system has been clinically applied at Chiba Hospital, Tokyo Dental College, since April 2005. This article reports the characteristics of this system, and its diagnostic power for maxillofacial lesions and the pre-operative planning dental implants.

PLoS neglected tropical diseases, 2014

Japanese Dental Science Review, 2008

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2011

The authors conducted a systematic literature review with the following aims: to investigate how ... more The authors conducted a systematic literature review with the following aims: to investigate how frequently soil-transmitted helminthiasis (STH) infections are endemic where schistosomiasis is present; and to assess the correlation between the risk level of schistosomiasis and that of STH. Among 155 sites on which data were collected and analyzed, schistosomiasis was present in 130, all of which were also co-endemic for STH, whereas 25 sites were endemic only for STH. Ninety percent (117 out of 130) of the areas eligible for preventive chemotherapy (PC) against schistosomiasis are also eligible for PC against STH. This fact provides managers of control programmes with the operationally important indication that use of available information on endemicity of schistosomiasis is a valid tool to predict the presence of STH in the same geographical area and to estimate the need of PC for STH. The implementation of this tool is expected to save financial and human resources and help accelerate the scale-up of PC throughout the world.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009

Clonorchiasis is an emerging food-borne trematode infection in Vietnam. Due to the absence of cos... more Clonorchiasis is an emerging food-borne trematode infection in Vietnam. Due to the absence of cost-effective preventive measures its control largely relies on morbidity reduction by chemotherapy with praziquantel. We performed a comparative cost estimation of three different diagnostic and intervention approaches in areas of high and low prevalence of clonorchiasis in northern Vietnam in order to select more cost-effective chemotherapy. Our study confirmed that a questionnaire investigating the habit of eating raw, freshwater fish was a rapid, cost-effective and operationally feasible tool for identifying individuals at risk of clonorchiasis in both high-prevalence and low-prevalence areas. The cost of diagnosis and intervention per person and per true positive case was 20-fold higher in low-prevalence areas, regardless of the type of approach. Geographical mapping of high-risk areas prior to screening is, therefore, recommended to maximize the cost-effectiveness of the intervention activities.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009

a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r h e a l t h . c o m / j o u r n a l s / t r s t High latrine coverage is not reducing the prevalence of soil-transmitted helminthiasis in Hoa Binh province, Vietnam Summary A baseline epidemiological survey for parasite infections was conducted between December 2007 and January 2008 in 155 villagers in a rural commune in Hoa Binh province, Vietnam. The prevalence of Ascaris lumbricoides, Trichuris trichiura and hookworm infection was 13.5%, 45.2% and 58.1%, respectively. At least one of the parasites was detected in 72.3% of the samples. We found no association between infection with A. lumbricoides or T. trichiura and engagement in agriculture, while hookworm infection was more prevalent in populations having frequent contact with soil. Agricultural use of human faeces was not correlated with any of the infections. We suggest that the consumption of vegetables that are commonly fertilized with human faeces in the community has led to the high infection rates with A. lumbricoides and T. trichiura, rather than the manipulation of faeces in farming activity. This also explains the high infection prevalence, despite high latrine coverage (98.1%) in the study population. The presence of latrines alone is not sufficient to reduce the prevalence of helminthiasis in a rural agricultural community if fresh faeces are used as fertilizer.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2008

A high prevalence of the liver flukes Clonorchis sinensis and Opisthorchis viverrini has been rep... more A high prevalence of the liver flukes Clonorchis sinensis and Opisthorchis viverrini has been reported in a number of provinces in Vietnam. Knowledge about C. sinensis infection gained from Thailand over the past decade suggests that the habit of eating raw freshwater fish is a major risk factor for infection. However, further information to confirm this is needed. In the present study 1155 villagers in two communes in northern Vietnam were interviewed and their stools were examined for the presence of liver flukes. The prevalence of infection was 26% and was 3.6 times higher in males than in females. The habit of eating raw fish increased the risk of C. sinensis infection 53-fold. These results provide evidence of a strong correlation between the intensity of C. sinensis infection and the cumulative quantity of freshwater fish consumed in a lifetime and suggest that simple questionnaires could be used in endemic areas to quickly identify populations at risk and enable targeted treatment.

Seminars in Ultrasound, CT and MRI, 2007

With the arrival of arthrography, computed tomography, and magnetic resonance imaging, diagnostic... more With the arrival of arthrography, computed tomography, and magnetic resonance imaging, diagnostic imaging of the temporomandibular joint has improved tremendously over the last 20 years. In patients with temporomandibular joint pain and dysfunction, the main focus was on meniscal pathology. The purpose of this article is to discuss several osseous abnormalities and demonstrate their association with temporomandibular joint pain and dysfunction. Semin Ultrasound CT MRI 28:213-221

International Health, 2011

Infection with soil-transmitted helminths (STH) is a major public health problem in many developi... more Infection with soil-transmitted helminths (STH) is a major public health problem in many developing countries, with pregnant women and children particularly at risk. Preventive chemotherapy, which is the intervention currently recommended by the WHO against the main helminth infections including those caused by STHs, aims at reducing morbidity through periodical administration of anthelminthic drugs either alone or in combination. The Expanded Programme on Immunization is one of the most widely implemented health programmes in the world and has well established access to children and women. The present study investigated the cost of the provision of anthelminthic drugs during existing immunisation campaigns. In Lao PDR, use of this integrated approach compared with implementation of the vertical deworming campaign alone allowed a reduction of the individual cost of deworming by 10 times (from US$0.23 in the vertical deworming campaign to US$0.03 in the integrated campaign). When drug cost was excluded, the cost of deworming an individual was US$0.007, implying that deworming 100 children would cost less than US$1 if drug donation was in place. The burden posed on health workers by the integration process was perceived as minimal and manageable. Moreover, delivery of anthelminthic drugs during immunisation campaigns enabled campaign teams to observe drug intake directly, which assured safety. These findings prove that integration is an opportunity to maximise health benefits through the delivery of multiple health products and the attainment of high coverage.

PLoS Neglected Tropical Diseases, 2014

Background: A mathematical model based on the Markov methodology to predict the change in prevale... more Background: A mathematical model based on the Markov methodology to predict the change in prevalence of soil-transmitted helminth (STH) infections during public health control activities is not available, but would be an extremely efficient planning tool. Method: We used the parasitological data collected during a deworming and iron supplementation programme for women of child-bearing age conducted in Vietnam between 2006 and 2011 to develop a Markov transition probability model. The transition probabilities were calculated from the observed changes in prevalence in the different classes of intensity for each STH species during the first year of intervention. The model was then developed and used to estimate the prevalence in year 2, 3, 4 and 5 for each STH species and for 'any STH infection'. The prevalence predicted by the model was then compared with the prevalence observed at different times during programme implementation. Results: The comparison between the model-predicted prevalence and the observed prevalence proved a good fit of the model. Conclusions: We consider the Markov transition probability model to be a promising method of predicting changes in STH prevalence during control efforts. Further research to validate the model with observed data in different geographical and epidemiological settings is suggested to refine the prediction model.

Japanese Dental Science Review, 2008

International Journal of Oral and Maxillofacial Surgery, 2007

Journal of Cranio-maxillofacial Surgery, 2008

Objective: Extensive mandibular reconstructions using internal distraction devices which we devel... more Objective: Extensive mandibular reconstructions using internal distraction devices which we developed for transporting bone are shown. Methods: The distraction device comprises a bridging reconstruction plate, brackets with miniplates, traction mechanisms, and traction wire. Activation of the traction mechanism pulls the wires connected to the bracket, which then slides and carries the transport disc along a rail. The cylinder sleeve of the traction mechanism is passed through the skin in the retrogonial area, and the entire device except for a part of the traction mechanism remains inside the body. Four (59-, 61-, 38-, and 61-year-old) patients had segmental defects because of tumor removal. Segmental osteotomies were made to provide 1.5-cm transport discs. The distraction device was fixed to the mandible as simulated. After a 7-day latency period, the device was activated at a rate of 0.5 mm twice a day. Transport discs moved with the brackets sliding on the rails 44 mm + 44 mm (bilaterally), 80 mm, 51 mm, and 33 mm + 41 mm in the respective patients. At the end of distraction the traction mechanisms were removed, leaving only the other components during the consolidation period. Results: Series of panoramic radiograms after the end of distraction showed a segment of regenerated bone in the distracted zone. The regenerated bone was achieved with trifocal and bifocal distraction osteogenesis. Conclusion: The segmental defects of the mandible were reconstructed with the bone transport distraction osteogenesis using the internal devices. This method enables extensive mandibular reconstruction without vascularised free bone graft.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2012

The integration of vertical control programmes of neglected tropical diseases (NTDs) aims to cont... more The integration of vertical control programmes of neglected tropical diseases (NTDs) aims to contain operational cost, simplify the application of the control measures and further extend the coverage of interventions. The Preventive Chemotherapy and Transmission Control (PCT) databank was established by the WHO to facilitate access and sharing of information from national programmes with stakeholders involved in NTD control. The PCT databank contains compilations of historical and current information on disease-specific epidemiological situations, the geographical overlapping of NTDs and progress of control activities in all the NTD-endemic countries. A summary of country-specific epidemiological maps and the progress of control activities are available from the online PCT databank and the Country Profiles. Annual progress of preventive chemotherapy interventions targeting specific NTDs is reported in the Weekly Epidemiological Record (WER) published annually for each disease target...

The Bulletin of Tokyo Dental College, 2006

Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial re... more Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial region have recently become commercially available. The newly-developed CBCT system, CB Throne (Hitachi Medical Corp., Tokyo), is characterized by a number of features such as low dose, sub-millimeter spatial resolution, and a small footprint. This system has been clinically applied at Chiba Hospital, Tokyo Dental College, since April 2005. This article reports the characteristics of this system, and its diagnostic power for maxillofacial lesions and the pre-operative planning dental implants.

PLoS neglected tropical diseases, 2014

Japanese Dental Science Review, 2008

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2011

The authors conducted a systematic literature review with the following aims: to investigate how ... more The authors conducted a systematic literature review with the following aims: to investigate how frequently soil-transmitted helminthiasis (STH) infections are endemic where schistosomiasis is present; and to assess the correlation between the risk level of schistosomiasis and that of STH. Among 155 sites on which data were collected and analyzed, schistosomiasis was present in 130, all of which were also co-endemic for STH, whereas 25 sites were endemic only for STH. Ninety percent (117 out of 130) of the areas eligible for preventive chemotherapy (PC) against schistosomiasis are also eligible for PC against STH. This fact provides managers of control programmes with the operationally important indication that use of available information on endemicity of schistosomiasis is a valid tool to predict the presence of STH in the same geographical area and to estimate the need of PC for STH. The implementation of this tool is expected to save financial and human resources and help accelerate the scale-up of PC throughout the world.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009

Clonorchiasis is an emerging food-borne trematode infection in Vietnam. Due to the absence of cos... more Clonorchiasis is an emerging food-borne trematode infection in Vietnam. Due to the absence of cost-effective preventive measures its control largely relies on morbidity reduction by chemotherapy with praziquantel. We performed a comparative cost estimation of three different diagnostic and intervention approaches in areas of high and low prevalence of clonorchiasis in northern Vietnam in order to select more cost-effective chemotherapy. Our study confirmed that a questionnaire investigating the habit of eating raw, freshwater fish was a rapid, cost-effective and operationally feasible tool for identifying individuals at risk of clonorchiasis in both high-prevalence and low-prevalence areas. The cost of diagnosis and intervention per person and per true positive case was 20-fold higher in low-prevalence areas, regardless of the type of approach. Geographical mapping of high-risk areas prior to screening is, therefore, recommended to maximize the cost-effectiveness of the intervention activities.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009

a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r h e a l t h . c o m / j o u r n a l s / t r s t High latrine coverage is not reducing the prevalence of soil-transmitted helminthiasis in Hoa Binh province, Vietnam Summary A baseline epidemiological survey for parasite infections was conducted between December 2007 and January 2008 in 155 villagers in a rural commune in Hoa Binh province, Vietnam. The prevalence of Ascaris lumbricoides, Trichuris trichiura and hookworm infection was 13.5%, 45.2% and 58.1%, respectively. At least one of the parasites was detected in 72.3% of the samples. We found no association between infection with A. lumbricoides or T. trichiura and engagement in agriculture, while hookworm infection was more prevalent in populations having frequent contact with soil. Agricultural use of human faeces was not correlated with any of the infections. We suggest that the consumption of vegetables that are commonly fertilized with human faeces in the community has led to the high infection rates with A. lumbricoides and T. trichiura, rather than the manipulation of faeces in farming activity. This also explains the high infection prevalence, despite high latrine coverage (98.1%) in the study population. The presence of latrines alone is not sufficient to reduce the prevalence of helminthiasis in a rural agricultural community if fresh faeces are used as fertilizer.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2008

A high prevalence of the liver flukes Clonorchis sinensis and Opisthorchis viverrini has been rep... more A high prevalence of the liver flukes Clonorchis sinensis and Opisthorchis viverrini has been reported in a number of provinces in Vietnam. Knowledge about C. sinensis infection gained from Thailand over the past decade suggests that the habit of eating raw freshwater fish is a major risk factor for infection. However, further information to confirm this is needed. In the present study 1155 villagers in two communes in northern Vietnam were interviewed and their stools were examined for the presence of liver flukes. The prevalence of infection was 26% and was 3.6 times higher in males than in females. The habit of eating raw fish increased the risk of C. sinensis infection 53-fold. These results provide evidence of a strong correlation between the intensity of C. sinensis infection and the cumulative quantity of freshwater fish consumed in a lifetime and suggest that simple questionnaires could be used in endemic areas to quickly identify populations at risk and enable targeted treatment.

Seminars in Ultrasound, CT and MRI, 2007

With the arrival of arthrography, computed tomography, and magnetic resonance imaging, diagnostic... more With the arrival of arthrography, computed tomography, and magnetic resonance imaging, diagnostic imaging of the temporomandibular joint has improved tremendously over the last 20 years. In patients with temporomandibular joint pain and dysfunction, the main focus was on meniscal pathology. The purpose of this article is to discuss several osseous abnormalities and demonstrate their association with temporomandibular joint pain and dysfunction. Semin Ultrasound CT MRI 28:213-221

International Health, 2011

Infection with soil-transmitted helminths (STH) is a major public health problem in many developi... more Infection with soil-transmitted helminths (STH) is a major public health problem in many developing countries, with pregnant women and children particularly at risk. Preventive chemotherapy, which is the intervention currently recommended by the WHO against the main helminth infections including those caused by STHs, aims at reducing morbidity through periodical administration of anthelminthic drugs either alone or in combination. The Expanded Programme on Immunization is one of the most widely implemented health programmes in the world and has well established access to children and women. The present study investigated the cost of the provision of anthelminthic drugs during existing immunisation campaigns. In Lao PDR, use of this integrated approach compared with implementation of the vertical deworming campaign alone allowed a reduction of the individual cost of deworming by 10 times (from US$0.23 in the vertical deworming campaign to US$0.03 in the integrated campaign). When drug cost was excluded, the cost of deworming an individual was US$0.007, implying that deworming 100 children would cost less than US$1 if drug donation was in place. The burden posed on health workers by the integration process was perceived as minimal and manageable. Moreover, delivery of anthelminthic drugs during immunisation campaigns enabled campaign teams to observe drug intake directly, which assured safety. These findings prove that integration is an opportunity to maximise health benefits through the delivery of multiple health products and the attainment of high coverage.

PLoS Neglected Tropical Diseases, 2014