Zoonoses in South-East Asia: a regional burden, a global threat

One health intervention for the control and elimination of scrub typhus, anthrax, and brucellosis in Southeast Asia: a systematic review

The "One Health" (OH) approach, introduced in 2004, integrates human, animal, and environmental health to address emerging and re-emerging diseases. This study evaluates OH strategies used by southeast Asian countries for brucellosis, anthrax, and scrub typhus. We systematically searched Medline, EMBASE, ProQuest, and EBSCO-CINHL up to May 11, 2023, screened 711 articles, and included ten studies (five on brucellosis, four on anthrax, and two on scrub typhus). Key strategies identified included intersectoral collaboration, vaccination initiatives, and comprehensive surveillance systems for both humans and animals. Additional efforts were noted in improving health infrastructure and implementing preventive measures. The review underscores that although some progress has been made, a more integrated OH approach is crucial for effective prevention and management of zoonotic diseases in southeast Asia, highlighting the need for enhanced collaboration and coordinated efforts across sectors.

Spatial epidemiology of human anthrax in Son La province, Vietnam, 2003-2022

AIMS

Anthrax is reported with frequency but poorly understood in Southeast Asian countries including Vietnam. In Vietnam, anthrax surveillance is national. However, case detection, prevention, and control are implemented locally at the provincial level. Here, we describe the epidemiological characteristics, identify spatial clusters of human anthrax, and compare the variation in livestock anthrax vaccine coverage to disease incidence in humans and livestock using historical data in Son La province, Vietnam (2003-2020).

METHODS AND RESULTS

Most human cases occurred between April and September. Most of the patients were male, aged 15-54 years old. The human cases were mainly reported by public district hospitals. There was a delay between disease onset and hospitalization of ~5 days. We identified spatial clusters of high-high incidence communes in the northern communes of the province using the local Moran's I statistic. The vaccine coverage sharply decreased across the study period. The province reported sporadic human anthrax outbreaks, while animal cases were only reported in 2005 and 2022.

CONCLUSIONS

These results suggest underreporting for human and livestock anthrax in the province. Intersectoral information sharing is needed to aid livestock vaccination planning, which currently relies on reported livestock cases. The spatial clusters identify areas for targeted surveillance and livestock vaccination, while the seasonal case data suggest prioritizing vaccination campaigns for February or early March ahead of the April peak. A regional approach for studying the role of livestock trading between Son La and neighbouring provinces in anthrax occurrence is recommended.

Spatial analysis of human and livestock anthrax in Lai Chau province, Vietnam (2004-2021)

Anthrax is reported globally with varying disease intensity and seasonality among countries. In Vietnam, anthrax epidemiology and ecology remain understudied. We used historical data of human and livestock anthrax from 2004 to 2021 in Lai Chau province, to identify spatial clusters of human and livestock anthrax, describe epidemiological characteristics, and compare livestock anthrax vaccine coverage to human and livestock disease incidence. Local Moran's I (LISA) using spatial Bayes smoothed commune-level cumulative incidence (per 10,000) for the study period, epidemiological descriptive statistics, livestock vaccine coverage data, and annual incidence rates (per 10,000) at provincial level were used. LISA identified a human anthrax hotspot (high-high) in the southeast which did not overlap spatially with livestock anthrax hotspots in southeastern and northeastern communes. Most human cases were male, aged 15-59 years, handled sick animals, and/or consumed contaminated meat. Almost all cases were reported by grassroot health facilities with a delay of 6.3 days between exposure and case notification to the national surveillance system. 80 % of human cases were reported from June-October. The increase in disease incidence occurred shortly after livestock anthrax vaccine coverage decreased. This study informs vaccination strategy and targeted surveillance and control measures in newly identified high-risk areas and seasons of anthrax.

The challenges of detecting Taenia solium and neurocysticercosis in low and middle-income countries: A scoping review of Lao People's Democratic Republic

OBJECTIVE

Taenia solium is a tapeworm of global importance due to the burden of disease associated with human epilepsy caused by neurocysticercosis. Unfortunately, diagnostic challenges impede control efforts in many low and middle-income countries. This review examines publications concerning Taenia species in the Lao PDR with a focus on T. solium to inform future research and control programmes.

METHODS

PubMed and Scopus databases were primary sources of evidence. Publications must have reported taeniasis or T. solium results from Lao PDR. Publications repeating results or samples were combined into unique projects.

RESULTS

A total of 64 publications were included and summarised into 46 projects. The majority of projects applied faecal microscopy as their only diagnostic technique. As a result, the specific species of Taenia was often not determined. Only five projects used molecular techniques to identify the species observed. Only case report of neurocysticercosis has been published. The northern region was included in half the number of projects compared to the south, despite being a high-risk area T. solium.

CONCLUSIONS

The diagnostic challenge of determining the species of Taenia present in a faecal sample presents a significant limitation to the control of T. solium in Lao PDR and is an experience that is relevant to many other low and middle-income countries. There must be an improved understanding of the distribution and frequency of T. solium if disease control efforts are to be intensified to reduce the burden of neurocysticercosis, as encouraged by WHO and others. It is hoped that this can be achieved through non-biological risk mapping tools and the more frequent application of molecular tools to routine sample collection. Diagnostic tools that are applicable to low resource settings should be a priority area of research for T. solium.

Growth in chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022 following disease emergence: a bibliometric and graphical analysis

BACKGROUND

ASEAN (Association of Southeast Asian Nations) is composed of ten Southeast Asian countries bound by socio-cultural ties that promote regional peace and stability. South Asia, located in the southern subregion of Asia, includes nine countries sharing similarities in geographical and ethno-cultural factors. Chikungunya is one of the most significant problems in Southeast and South Asian countries. Much of the current chikungunya epidemic in Southeast Asia is caused by the emergence of a virus strain that originated in Africa and spread to Southeast Asia. Meanwhile, in South Asia, three confirmed lineages are in circulation. Given the positive correlation between research activity and the improvement of the clinical framework of biomedical research, this article aimed to examine the growth of chikungunya virus-related research in ASEAN and South Asian countries.

METHODS

The Scopus database was used for this bibliometric analysis. The retrieved publications were subjected to a number of analyses, including those for the most prolific countries, journals, authors, institutions, and articles. Co-occurrence mapping of terms and keywords was used to determine the current state, emerging topics, and future prospects of chikungunya virus-related research. Bibliometrix and VOSviewer were used to analyze the data and visualize the collaboration network mapping.

RESULTS

The Scopus search engine identified 1280 chikungunya-related documents published by ASEAN and South Asian countries between 1967 and 2022. According to our findings, India was the most productive country in South Asia, and Thailand was the most productive country in Southeast Asia. In the early stages of the study, researchers investigated the vectors and outbreaks of the chikungunya virus. In recent years, the development of antivirus agents has emerged as a prominent topic.

CONCLUSIONS

Our study is the first to present the growth of chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022. In this study, the evaluation of the comprehensive profile of research on chikungunya can serve as a guide for future studies. In addition, a bibliometric analysis may serve as a resource for healthcare policymakers.

Increasing risks for emerging infectious diseases within a rapidly changing High Asia

The cold and arid mountains and plateaus of High Asia, inhabited by a relatively sparse human population, a high density of livestock, and wildlife such as the iconic snow leopard Panthera uncia, are usually considered low risk for disease outbreaks. However, based on current knowledge about drivers of disease emergence, we show that High Asia is rapidly developing conditions that favor increased emergence of infectious diseases and zoonoses. This is because of the existing prevalence of potentially serious pathogens in the system; intensifying environmental degradation; rapid changes in local ecological, socio-ecological, and socio-economic factors; and global risk intensifiers such as climate change and globalization. To better understand and manage the risks posed by diseases to humans, livestock, and wildlife, there is an urgent need for establishing a disease surveillance system and improving human and animal health care. Public health must be integrated with conservation programs, more ecologically sustainable development efforts and long-term disease surveillance.

Wild geckos considered as the natural reservoir of Salmonella Weltevreden in Southeast Asian countries

A total of 1,318 wild geckos were collected in Cambodia, Thailand and Vietnam (Hue and the Mekong Delta) from 2012 to 2015 to determine the prevalence of Salmonella Weltevreden. Those geckos belong to three species: common house gecko (Hemidactylus frenatus), flat-tailed house gecko (Hemidactylus platyurus) and four-clawed gecko (Gehyra mutilata). Of 1,318 gecko samples, 293 (22.2%) samples were positive for Salmonella in this study. The prevalence of Salmonella in geckos was 46.0% in Thailand, 17.3% in Cambodia and 16.3% in Vietnam. Among the Salmonella isolates, S. Weltevreden was the most predominant serovar (32.1%) isolated from wild geckos in these countries. There was no significant difference in the prevalence of Salmonella among gecko species. All S. Weltevreden isolates (100%) were susceptible to the nine antibiotics examined in this study. The PFGE assay by XbaI enzyme identified 19 different patterns from 75 S. Weltevreden isolates. These isolates showed high genetic heterogenicity, and there were specific types prevalent in each region. Furthermore, S. Weltevreden has been prevalent since the ancient times in this region. The results indicate that wild gecko seems to be an important natural reservoir for S. Weltevreden as well as a source of Salmonella infections in humans in Southeast Asian countries.

Copro-molecular identification of intestinal nematode infections in a rural community in East Malaysia

Soil-transmitted helminth (STH) infections are the most common intestinal parasitic infections of medical importance in humans. The infections are widely distributed throughout tropical and subtropical countries, particularly among disadvantaged and underprivileged communities. In Malaysia, STH infections is highly prevalent, especially among the indigenous groups. However, species identification through molecular studies is still lacking. Using molecular techniques, this study was conducted to identify STH species that infect humans. Faecal samples were collected from three Iban tribal longhouses in the rural area of Sarikei Division, Sarawak. Positive faecal samples by microscopy were subjected to PCR and sequenced for species identification. Based on the microscopy examination, the most prevalent STH infection was Ascaris, followed by hookworm and Trichuris. All microscopy-positive samples were then PCR-amplified. The amplicons were sequenced, aligned, and compared with other sequences in the GenBank database. The results showed that Ascaris lumbricoides was the predominant STH species, followed by Trichuris trichiura, Ancylostoma duodenale, and Necator americanus. Our findings were contradictory to past studies, as we showed that A. duodenale was more abundant than N. americanus. Socioeconomic improvement and health education programs should be included in the management and prevention of public health strategies against STH.

The potential of diagnostic point-of-care tests (POCTs) for infectious and zoonotic animal diseases in developing countries: Technical, regulatory and sociocultural considerations

Remote and rural communities in low‐ and middle‐income countries (LMICs) are disproportionately affected by infectious animal diseases due to their close contact with livestock and limited access to animal health personnel). However, animal disease surveillance and diagnosis in LMICs is often challenging, and turnaround times between sample submission and diagnosis can take days to weeks. This diagnostic gap and subsequent disease under‐reporting can allow emerging and transboundary animal pathogens to spread, with potentially serious and far‐reaching consequences. Point‐of‐care tests (POCTs), which allow for rapid diagnosis of infectious diseases in non‐laboratory settings, have the potential to significantly disrupt traditional animal health surveillance paradigms in LMICs. This literature review sought to identify POCTs currently available for diagnosing infectious animal diseases and to determine facilitators and barriers to their use and uptake in LMICs. Results indicated that some veterinary POCTs have been used for field‐based animal disease diagnosis in LMICs with good results. However, many POCTs target a small number of key agricultural and zoonotic animal diseases, while few exist for other important animal diseases. POCT evaluation is rarely taken beyond the laboratory and into the field where they are predicted to have the greatest impact, and where conditions can greatly affect test performance. A lack of mandated test validation regulations for veterinary POCTs has allowed tests of varying quality to enter the market, presenting challenges for potential customers. The use of substandard, improperly validated or unsuitable POCTs in LMICs can greatly undermine their true potential and can have far‐reaching negative impacts on disease control. To successfully implement novel rapid diagnostic pathways for animal disease in LMICs, technical, regulatory, socio‐political and economic challenges must be overcome, and further research is urgently needed before the potential of animal disease POCTs can be fully realized.

Current status of Blastocystis sp. in animals from Southeast Asia: a review

Blastocystis is the most frequently observed eukaryotic gastrointestinal symbiont in humans and animals. Its low host specificity and zoonotic potential suggest that animals might serve as possible reservoirs for transmission. The prevalence and subtype distributions of Blastocystis sp. in animal populations in Southeast Asia, a hotspot for zoonotic diseases, are reviewed. Recommendations for future research aimed at understanding the zoonotic role of Blastocystis are also included. Seven countries have, so far, reported Blastocystis infection in various animals, such as livestock, poultry, companion animals, and non-human primates. Pigs were the most studied animals, and there were records of 100% prevalence in pigs, cattle, and ostriches. Using polymerase chain reaction (PCR)-based approaches, twelve Blastocystis sp. subtypes (STs), namely ST1, ST2, ST3, ST4, ST5, ST6, ST7, ST8, ST9, ST10, ST12, and ST14 have been recognised infecting animals of Southeast Asia. ST1 and ST5 were the most frequently identified, and Malaysia observed the most diverse distribution of subtypes. Further investigations on Blastocystis sp. in various animal hosts, using adequate sample sizes and uniform detection methods, are essential for a better understanding of the distribution of this organism. Detailed genome studies, especially on STs shared by humans and animals, are also recommended.

Detection of novel coronaviruses in bats in Myanmar

The recent emergence of bat-borne zoonotic viruses warrants vigilant surveillance in their natural hosts. Of particular concern is the family of coronaviruses, which includes the causative agents of severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and most recently, Coronavirus Disease 2019 (COVID-19), an epidemic of acute respiratory illness originating from Wuhan, China in December 2019. Viral detection, discovery, and surveillance activities were undertaken in Myanmar to identify viruses in animals at high risk contact interfaces with people. Free-ranging bats were captured, and rectal and oral swabs and guano samples collected for coronaviral screening using broadly reactive consensus conventional polymerase chain reaction. Sequences from positives were compared to known coronaviruses. Three novel alphacoronaviruses, three novel betacoronaviruses, and one known alphacoronavirus previously identified in other southeast Asian countries were detected for the first time in bats in Myanmar. Ongoing land use change remains a prominent driver of zoonotic disease emergence in Myanmar, bringing humans into ever closer contact with wildlife, and justifying continued surveillance and vigilance at broad scales.

Cryptosporidium Infection Increases the Risk for Chronic Diarrhea Among People Living With HIV in Southeast Asia: A Systematic Review and Meta-Analysis

We conducted a systematic review research and meta-analysis to reveal the relationship between the risk of chronic diarrhea and Cryptosporidium infection in people living with HIV in Southeast Asia. We performed online peer-reviewed literature research from January 2005 to December 2017, which included PubMed, Science Direct, ProQuest, EBSCO, Cochrane, and Web of Science databases. Calculation of size effects in the meta-analysis was performed by STATA 13.0 software to estimate relative risks (RRs) with 95% confidence intervals (CIs) for any associations. Seven cross-sectional research articles were recruited in this study based on the inclusion and exclusion criteria. Our analysis revealed a significant relationship between cryptosporidiosis and the risk of chronic diarrhea in people living with HIV, with RR = 1.325; 95% CI = 1.157 to 1.517; and P < .000. Our results suggested that cryptosporidiosis increases the risk of chronic diarrhea, and low CD4⁺ lymphocyte cell counts aggravate the degree of diarrhea. Therefore, clinicians should be more aware in treating HIV-positive people, especially those with low CD4⁺ cell counts, and we suggest that Cryptosporidium laboratory examinations be conducted immediately.

Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination

Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.

Knowledge, Attitudes and Practices Associated with Brucellosis among Small-Scale Goat Farmers in Thailand

OBJECTIVES

This study aimed to identify occupational risk factors for brucellosis among small scale goat farmers in Thailand.

METHODS

To better understand farmers' knowledge, attitudes and practices associated with brucellosis we interviewed 51 farmers and tested 314 goats for Brucella melitensis.

RESULTS

All serological samples tested negative for Brucella infection. Based on previous research and estimates provided from the Thai national brucellosis surveillance system, zero seropositivity was less than expected. Findings from interviews with farmers demonstrate that most respondents were relatively new to goat farming with just over half (53%) reporting owning goats for five or fewer years. The majority of respondents demonstrated important gaps in knowledge on disease transmission in animals and knowledge of human brucellosis was particularly limited with just over half (54%) reporting that humans could become infected. Participants had a very low perceived risk of infection with the majority (91.7%) reporting that they or a member of their household were not at risk of the disease.

CONCLUSION

Overall findings from this study support that brucellosis poses an occupational risk to goat farmers with specific areas of concern including weak awareness of disease transmission to humans and lack of knowledge on specific safe farm practices such as quarantine practices. Findings from this study contribute to a more comprehensive understanding of brucellosis in Thailand by identifying specific occupational risk factors and describing areas where farmer education and training should be strengthened.

The importance of wild gecko as a source of human Salmonella infection

A total of 201 wild geckos from the region of Mekong Delta, Vietnam were collected to determine the viable number and survival period of Salmonella in their feces. Of the 101 samples examined, 24 (23.8%) were Salmonella positive. These 24 geckos excreted Salmonella in their feces in a range of 1 to 8.6 log CFU/g with a mean of 4.5 ± 3.2 log CFU/g. Among the Salmonella serovars, Salmonella Weltevreden was the most predominant serovar (37.5%). Moreover, Salmonella could survive for 6 weeks in gecko feces at room temperature in Vietnam. These results indicate that the wild gecko seems to play an important role as a reservoir for Salmonella and a source of Salmonella infection in humans in Southeast Asian countries.

One Health/EcoHealth capacity building programs in South and South East Asia: a mixed method rapid systematic review

BACKGROUND

Although One Health (OH) or EcoHealth (EH) have been acknowledged to provide comprehensive and holistic approaches to study complex problems, like zoonoses and emerging infectious diseases, there remains multiple challenges in implementing them in a problem-solving paradigm. One of the most commonly encountered barriers, especially in low- and middle-income countries, is limited capacity to undertake OH/EH inquiries. A rapid review was undertaken to conduct a situation analysis of the existing OH/EH capacity building programs, with a focused analysis of those programs with extensive OH engagement, to help map the current efforts in this area.

METHODS

A listing of the OH/EH projects/initiatives implemented in South Asia (SA) and South East Asia (SEA) was done, followed by analysis of documents related to the projects, available from peer-reviewed or grey literature sources. Quantitative data was extracted using a data extraction format, and a free listing of qualitative themes was undertaken.

RESULTS

In SEA, 13 unique OH/EH projects, with 37 capacity building programs, were identified. In contrast, in SA, the numbers were 8 and 11 respectively. In SA, programs were oriented to develop careers in program management, whereas, in SEA, the emphasis was on research. Two thirds of the programs in SEA had extensive OH engagement, whereas only one third of those in SA did. The target for the SEA programs was wider, including a population more representative of OH stakes. SEA program themes reveal utilization of multiple approaches, usually in shorter terms, and are growing towards integration with the traditional curricula. Such convergence of themes was lacking in SA programs. In both regions, the programs were driven by external donor agencies, with minimal local buy-in.

CONCLUSIONS

There is limited investment in research capacity building in both SA and SEA. The situation appears to be more stark in SA, whilst SEA has been able to use the systematic investment and support to develop the OH/EH agenda and strategize capacity building in the core competencies. In order to effectively address the disease emergence hotspots in these regions, there needs to be strategic funding decisions targeting capacity building in the core OH/EH competencies especially related to transdisciplinarity, systems thinking, and adaptive management.

Willingness to Consult a Veterinarian on Physician's Advice for Zoonotic Diseases: A Formal Role for Veterinarians in Medicine?

Physicians appear to find zoonotic diseases a challenge and consider that this topic belongs more to the veterinary profession. However, veterinarians have no formal role in clinical medicine. Data were collected as part of the Queensland Social Survey 2014 to determine the willingness of the public, if diagnosed with a zoonotic disease, to consult a veterinarian on the advice of a physician. Self-reported willingness to consult with a veterinarian at the respondent’s own expense was 79.8% (95% CI: 81.96%-77.46%) (976/1223). If the cost was funded by Medicare, the Australian public health insurance scheme, 90.7% (95% CI: 92.18%-88.92%) (1109/1223) would be willing to consult a veterinarian. Therefore, a large majority of Australian residents would be willing to consult with a veterinarian on the advice of their physician if they had a zoonotic disease. Does this indicate a possible new role for veterinarians under Clinical One Health?

Prevalence of Endemic Pig-Associated Zoonoses in Southeast Asia: A Review of Findings from the Lao People's Democratic Republic

The increasing intensification of pork production in southeast Asia necessitates an urgent requirement to better understand the dual impact of pig-associated zoonotic disease on both pig production and human health in the region. Sharing porous borders with five countries and representing many regional ethnicities and agricultural practices, the Lao People's Democratic Republic (Lao PDR) appears well placed to gauge the levels of pig-associated zoonoses circulating in the wider region. Despite this, little is known about the true impact of zoonotic pathogens such as leptospirosis, Trichinella, hepatitis E virus (HEV), Japanese encephalitis (JE), and Taenia solium on human health and livestock production in the country. A comprehensive review of the published prevalences of these five pig-associated zoonoses in Lao PDR has demonstrated that although suspicion remains high of their existence in pig reservoirs across the country, epidemiological data are scarce; only 31 epidemiological studies have been undertaken on these diseases in the past 25 years. A greater understanding of the zoonoses prevalence and subsequent risks associated with pork production in the southeast Asian region could help focus public health and food safety interventions at key points along the value chain, benefiting both livestock producers and the broader animal and human health systems in the region.

How to reach the poor? Surveillance in low-income countries, lessons from experiences in Cambodia and Madagascar

Surveillance of animal diseases in developing countries faces many constraints. Innovative tools and methods to enhance surveillance in remote and neglected areas should be defined, assessed and applied in close connection with local farmers, national stakeholders and international agencies. The authors performed a narrative synthesis of their own publications about surveillance in Madagascar and Cambodia. They analysed the data in light of their fieldwork experiences in the two countries' very challenging environments. The burden of animal and zoonotic diseases (e.g. avian influenza, African swine fever, Newcastle disease, Rift Valley fever) is huge in both countries which are among the poorest in the world. Being poor countries implies a lack of human and financial means to ensure effective surveillance of emerging and endemic diseases. Several recent projects have shown that new approaches can be proposed and tested in the field. Several advanced participatory approaches are promising and could be part of an innovative method for improving the dialogue among different actors in a surveillance system. Thus, participatory modelling, developed for natural resources management involving local stakeholders, could be applied to health management, including surveillance. Data transmission could benefit from the large mobile-phone coverage in these countries. Ecological studies and advances in the field of livestock surveillance should guide methods for enhancing wildlife monitoring and surveillance. Under the umbrella of the One Health paradigm, and in the framework of a risk-based surveillance concept, a combination of participatory methods and modern technologies could help to overcome the constraints present in low-income countries. These unconventional approaches should be merged in order to optimise surveillance of emerging and endemic diseases in challenging environments.