Control and prevention of emerging parasitic zoonoses

Emerging zoonoses have been defined as zoonoses that are newly recognised or newly evolved, or that have occurred previously but show an increase in incidence or expansion in geographical, host or vector range. Among parasitic zoonoses, protozoa are particularly likely to emerge. Control and prevention of emerging parasitic zoonoses are complex tasks that require an integrative and multidisciplinary approach. Reduction of parasite burden is certainly a major objective but cannot be set alone. Therefore, environmental and ecological modifications need to be implemented to reduce not only the parasitic load, but also the risk of parasite transmission. Finally, education and behavioral changes are critical for the success of both control and prevention of these diseases. However, without appropriate financial resources specifically allocated at the local and national levels as well as through international cooperation, control and prevention of these emerging parasitic diseases will not be possible.     

Canine gastrointestinal parasitic zoonoses in India

Although well recognized and studied in developed countries, canine parasitic zoonoses pose a lowly prioritized public health problem in developing countries such as India, where conditions are conducive for transmission. A study of the most recent parasite survey determining prevalence and epidemiology of canine parasitic zoonoses among tea-growing communities of northeast India demonstrated the endemicity of the problem. This particular study serves as a model using conventional, as well as molecular parasitological, tools to provide novel insights into the role of dogs as mechanical transmitters of human parasites such as Ascaris and Trichuris, and discusses the risks dogs pose with regards to zoonotic transmission of hookworms and Giardia.     

Human behaviour and the epidemiology of parasitic zoonoses

The behaviour of Homo sapiens has a pivotal role to play in the macro and microepidemiology of emerging or re-emerging parasitic zoonoses. Changing demographics and the concomitant alterations to the environment, climate, technology, land use and changes in human behavior, converge to favour the emergence and spread of parasitic zoonoses. The recent unprecedented movements of people, their animals and their parasites around the world, introduce and mix genes, cultural preferences, customs, and behavioral patterns. The increasing proclivity for eating meat, fish, crabs, shrimp, molluscs raw, undercooked, smoked, pickled or dried facilitates a number of protozoan (Toxoplasma), trematode (Fasciola sp., Paragonimus spp., Clonorchis sp., Opisthorchis spp., Heterophyes sp., Metagonimus sp., Echinostoma spp., Nanophyetus sp.) cestode (Taenia spp, Diphyllobothrum sp.) and nematode (Trichinella spp., Capillaria spp., Gnathostoma spp., Anisakis sp., Parastrongylus spp.) caused zoonoses. The increasing world population and the inability to keep pace with the provision of adequate sanitation and clean, safe drinking water, has led to an increased importance of waterborne zoonoses, such as those caused by Giardia, Cryptosporidium and Toxoplasma. Our close relationship with and the numerous uses to which we put companion animals and their ubiquitous distribution has resulted in dogs and cats unwitting participation in sharing over 60 parasite species including: Giardia, Cryptosporidium, Toxoplasma, most foodborne trematode species, Diphyllobothrum, Echinococcus spp., Ancylostoma and Toxocara. Changing human behaviour through education, to encourage the proper cooking of food, which may have cultural and social significance, will remain as challenging as controlling stray and feral pet populations, improving hygiene levels and the provision of safe drinking water and the proper use of sanctuary facilities. Long pre-patent periods and the normally insidious sub-clinical nature of most zoonoses makes advice requiring behavioural change for their control a difficult task. Our clearer understanding of the heterogeneity of susceptibility to infection, the complex genetic variations of people and parasite species and the development of molecular epidemiological tools is shedding more light on transmission routes and the spectrum of disease that is observed. Improved and new serological, molecular and imaging diagnostic tests and the development of broad spectrum chemotherapeutic agents has led to the attenuation of morbidity and mortality due to parasitic zoonoses in economically advantaged regions. Such advancements, in partnership with supportive behavioural change, has the potential for a sustainable global reduction in the burden of ill health due to parasitic zoonoses. Whether this will materialise is a challenge for us all.     

Fish-borne parasitic zoonoses: status and issues

The fish-borne parasitic zoonoses have been limited for the most part to populations living in low- and middle-income countries, but the geographical limits and populations at risk are expanding because of growing international markets, improved transportation systems, and demographic changes such as population movements. While many in developed countries will recognize meat-borne zoonoses such as trichinellosis and cysticercosis, far fewer are acquainted with the fish-borne parasitic zoonoses which are mostly helminthic diseases caused by trematodes, cestodes and nematodes. Yet these zoonoses are responsible for large numbers of human infections around the world. The list of potential fish-borne parasitic zoonoses is quite large. However, in this review, emphasis has been placed on liver fluke diseases such as clonorchiasis, opisthorchiasis and metorchiasis, as well as on intestinal trematodiasis (the heterophyids and echinostomes), anisakiasis (due to Anisakis simplex larvae), and diphyllobothriasis. The life cycles, distributions, epidemiology, clinical aspects, and, importantly, the research needed for improved risk assessments, clinical management and prevention and control of these important parasitic diseases are reviewed.     

宠物重要人兽共患寄生虫病

随着宠物饲养的盛行,与宠物相关的人兽共患寄生虫病愈加得到高度重视。为了避免和减少人兽共患寄生虫病的流行,本文就几种重要的宠物人兽共患寄生虫病的流行情况、诊断及防治等作一介绍,以期提高认识,防患未然。     

Ticks (Acari: Ixodoidea) in China: Geographical distribution,host diversity,and specificity

Ticks are obligate blood‐sucking ectoparasites, which not only directly damage through bites but also transmit many pathogens. China has a high diversity of tick species, 125 species have been reported, including 111 hard tick and 14 soft tick species. Many of the ticks are important vectors of pathogens, resulting in zoonoses. The dynamics of ticks are affected by both the host and habitat environment. However, systematic studies on the geographical distribution, host diversity, and specificity of ticks are limited in China. To achieve this goal, the relevant available data were summarized and analyzed in this study. Ticks are distributed in all parts of China and Xinjiang has the most records of ticks. The distribution of ticks in adjacent areas is similar, indicating that the habitat environment affects their distribution. Most ticks are widely distributed, whereas some species are endemic to their distributed regions. Ticks are parasitic on mammals, birds, and reptiles, of which mammals are the main host species. Overall, most ticks parasitize different hosts, only a few ticks have strict host specificity, such as ticks that are specifically parasitic on reptiles and bats. In addition, environmental changes and control efforts also influence the dynamics of ticks. These results can better reveal tick biological traits and are valuable for tick control.     

Prevalence Studies of Dementia in Mainland China,Hong Kong and Taiwan: A Systematic Review and Meta-Analysis

Background

Many studies have considered the prevalence of dementia in mainland China, Hong Kong and Taiwan. However, area level estimates have not been produced. This study examines area differences across mainland China, Hong Kong and Taiwan adjusting for the effect of methodological factors with the aim of producing estimates of the numbers of people with dementia in these areas.

Method and Findings

A search of Chinese and English databases identified 76 dementia prevalence studies based on samples drawn from mainland China, Hong Kong and Taiwan between 1980 and 2012. A pattern of significantly decreasing prevalence was observed from northern, central, southern areas of mainland China, Hong Kong and Taiwan. Area variations in dementia prevalence were not explained by differences in methodological factors (diagnostic criteria, age range, study sample size and sampling method), socioeconomic level or life expectancy between areas. The results of meta-analysis were applied to current population data to provide best estimate. Based on the DSM-IV diagnostic criteria, the total number of people aged 60 and over with dementia in mainland China, Hong Kong and Taiwan is 8.4 million (4.6%, 95% CI: 3.4, 5.8) and in northern, central and southern areas are 3.8 (5.1%, 95% CI: 4.1, 6.1), 3.2 (4.4%, 95% CI: 3.2, 5.6) and 1.2 (3.9%, 95% CI: 2.3, 5.4) million respectively. These estimates were mainly based on the studies existing in highly developed areas and potentially affected by incomplete and insufficient data.

Conclusions

The findings of this review provide a robust estimate of area differences in dementia prevalence. Application of the estimated prevalence to population data reveals the number of people with dementia is expected to double every 20 years, areas in mainland China will be facing the greatest dementia challenge.     

Contamination by helminths in public places of the province of Chubut, Argentina

Canine-borne helminthiases constitute a worldwide problem. Some of these parasites can originate serious pathologies in humans. Given the potential existence of these zoonoses in Argentina, horizontal surveys on contamination degree evaluated as faeces per hectare and on parasite prevalence in faeces were carried out in six localities of the Province of Chubut. The behaviour of people visiting public places was also analyzed qualitatively. All of the survey sites were contaminated with faeces and with some parasitic forms. Contamination degrees ranged from 32 to 147 faeces/ha. Toxocara sp. (17.4%), Strongyloides sp. (5.1%), and Ancylostoma. sp (5.6%) were the main genera among other parasites detected. As a whole, the analysis revealed that contamination degree, prevalence and human behaviour in relation to the exposure to the parasite would be the main factors to be taken into account in formulating control measures. Transmission risk patterns in Chubut were not homogeneous; therefore, studies and control strategies should be devised and implemented at the local scale.     

Anthropogenic Effects of Reservoir Construction on the Parasite Fauna of Aquatic Wildlife

The creation of large freshwater reservoirs is one of the most dramatic anthropogenic impacts on the natural environment. With worldwide rising demand for water, the construction of more reservoirs is inevitable. Although the effects of reservoir construction on many medically important parasites are well known and appreciated, changes to aquatic wildlife host–parasite interactions have been largely undervalued even though a large body of literature exists. The present review examines changes in the wildlife parasite fauna during the impoundment of reservoirs, focusing on the parasites of invertebrates, fish, and birds, the effects both upstream and downstream of the reservoir, parasitic zoonoses, the associated pollution generated, and assesses the impact of the recently completed Three Gorges Dam in China on the Yangtze River’s parasite fauna.     

Immunity and genetics: their relation to control of parasitic zoonoses.

Effective control of parasitic zoonoses will ultimately require a combination of several approaches, including hygiene/sanitation, pasture management, chemotherapy and immunoprophylaxis. Development of vaccines, and other approaches to improving protective immunity, require a detailed understanding of parasite immunogenicity and host immune responsiveness. It is increasingly recognized that there is considerable variation in both of these parameters, and that this variation is genetically determined. Recent studies in this area and the consequences for control are discussed.     

同一健康理念下中国野生动物源疫病监测及响应体系发展对策

现代人类新发传染病中, 有60.3%是人兽共患病, 其中71.8%源于野生动物。野生动物是许多病原体的贮存库, 对人类和饲养动物会产生潜在的生物安全威胁。目前, 中国针对饲养动物疫病的监测检测系统和法律法规较为健全, 但针对野生动物的疫源疫病监测仍比较薄弱。根据“One Health”的理念, 野生动物疫源疫病的有效监测与相应防治措施的落实, 不仅可以为人兽共患病的大规模流行做出预警并降低其几率, 同时也为野生动物种群的健康提供了保障。本研究通过国际案例的比较分析, 提出有效的野生动物疫源疫病监测系统特征。同时, 通过对我国现有监测体系的研究分析, 结合利益相关方访谈以及实地调查, 提出了完善现有系统的主要措施建议。建议包括: (1)推进不同政府部门间的资源互通, 提高国家疫病监测体系应对跨学科、跨领域问题的综合能力; (2)针对人及饲养动物与野生动物接触频繁的生产生活方式, 应建立重点监测管理和响应机制; (3)提高对科学技术的重视, 包括建立野生动物疫病参考实验室、提升相关工作人员的技术能力等, 保障科学的监测方案和检测方法; (4)建立基于公众和现有监测资源的信息上报、汇总系统, 提升野生动物疫病监测的公众参与度和信息透明度。     

日本血吸虫GST蛋白和14-3-3蛋白的研究进展

血吸虫病是严重危害人类健康的人兽共患病之一,在全球范围内,血吸虫病曾在76个国家和地区流行,有超过2亿人感染了血吸虫病。目前,世界上采取了一些人畜同步治疗等综合防治措施,虽取得了一定的成效,但仍面临着成本高、再感染率高等一系列问题。因此,寻找新的治疗药物、疫苗候选分子以及开发高度特异且敏感的标准化免疫诊断试剂是当前日本血吸虫病基础研究的重要内容。主要对WHO提出的最具潜力的疫苗候选分子血吸虫GST蛋白以及参与血吸虫许多生物学功能的14-3-3蛋白的最新研究进展进行一些阐述。     

宠物重要人兽共患细菌病流行现状及其控制策略

随着我国社会经济发展和城市化进程的加速,宠物数量日益增多,宠物人兽共患病发病率日渐增高,本文对我国宠物重要人兽共患细菌病流行状况、原因进行了阐述,并提出了防控对策。     

我国人与犬、猫共患病防控存在的主要问题与对策建议

随着社会经济的发展、城市化进程的加速及人们生活水平的不断提高,越来越多的宠物走进了人们的家庭,在人类社会生活中发挥了积极作用。但同时,宠物也是人兽共患病的重要传染源和传播媒介。与人类关系最为密切的犬、猫在人兽共患病的防控中具有重要的意义。在已报道的200多种主要的人兽共患病中,与宠物犬、猫有直接或间接关系的有70余种。随着宠物犬猫数量的大幅攀升和宠物业的飞速发展,我国人与犬猫共患病可能会出现逐步高发的趋势,疫病防控工作面临着许多问题。为了完善宠物管理制度,建立有效的防疫监督体系,对人与犬猫共患病实行有效的防控,本文就完善法律法规、形成综合管理机制,加强卫生监督、强化无害化处理、培养专业人才以及广泛开展宣传教育等6个方面提出了相关建议。     

Modeling the transmission dynamics and control of hepatitis B virus in China

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV) and is a major global health problem. HBV is the most common serious viral infection and a leading cause of death in mainland China. Around 130 million people in China are carriers of HBV, almost a third of the people infected with HBV worldwide and about 10% of the general population in the country; among them 30 million are chronically infected. Every year, 300,000 people die from HBV-related diseases in China, accounting for 40-50% of HBV-related deaths worldwide. Despite an effective vaccination program for newborn babies since the 1990s, which has reduced chronic HBV infection in children, the incidence of hepatitis B is still increasing in China. We propose a mathematical model to understand the transmission dynamics and prevalence of HBV infection in China. Based on the data reported by the Ministry of Health of China, the model provides an approximate estimate of the basic reproduction number R₀=2.406. This indicates that hepatitis B is endemic in China and is approaching its equilibrium with the current immunization program and control measures. Although China made a great progress in increasing coverage among infants with hepatitis B vaccine, it has a long and hard battle to fight in order to significantly reduce the incidence and eventually eradicate the virus.     

A review of taeniasis and cysticercosis in the Lao People's Democratic Republic

Taeniasis and cysticercosis are important but underreported parasitic zoonoses in the Lao People's Democratic Republic (Lao PDR). Reports of human and pig cysticercosis are rather limited and based largely on anecdotal evidence. To date, no structured surveys of disease prevalence or incidence have been reported. However, one unpublished pilot survey of pig cysticercosis in a slaughterhouse in northern Laos estimated prevalence to be 1.7%, without speciation of parasite cysts. Over the past 20 years, nine surveys of intestinal helminthic infection have been conducted; the prevalence of human taeniasis ranged from 0 to 14.0%. The study designs and sample sizes varied greatly, however a high degree of spatial and age variation in taeniasis prevalence was evident. These results are however inconclusive as the species of tapeworm infecting the people was not determined. To further our knowledge of taeniasis and cysticercosis in Lao PDR, structured community-based surveys in high-risk areas are required in combination with the use of sensitive and specific diagnostic tests capable of identifying the pork tapeworm, Taenia solium. This will enable the development and implementation of control measures that are both appropriate and sustainable if T. solium is shown to be a public health threat.     

Egg rejection and clutch phenotype variation in the plain prinia Prinia inornata

Avian hosts of brood parasites can evolve anti‐parasitic defenses to recognize and reject foreign eggs from their nests. Theory predicts that higher inter‐clutch and lower intra‐clutch variation in egg appearance facilitates hosts to detect parasitic eggs as egg‐rejection mainly depends on the appearance of the egg. Therefore, we predict that egg patterns and rejection rates will differ when hosts face different intensity of cuckoo parasitism. We tested this prediction in two populations of the plain prinia Prinia inornata: Guangxi in mainland China with high diversity and density of cuckoo species, and Taiwan where there is only one breeding cuckoo species, the oriental cuckoo Cuculus optatus. As expected, egg patterns were similar within clutches but different among clutches (polymorphic eggs) in the mainland population, while the island population produced more uniform egg morphs. Furthermore, the mainland population showed a high rate of egg rejection, while the island population exhibited dramatically reduced egg grasp‐rejection ability in the absence of parasitism by the common cuckoo Cuculus canorus. Our study suggests that prinias show lower intra‐clutch consistency in egg colour and lose egg‐rejecting ability under relaxed selection pressure from brood parasitism.     

Detection and characterisation of parasites causing emerging zoonoses

Understanding the epidemiology of zoonotic parasitic infections is dependent upon the availability of accurate and sensitive diagnostic techniques. The development of molecular diagnostic methods, particularly those utilising PCR for the detection of zoonoses will contribute greatly to the identification and control of these pathogens, by increasing the speed of diagnosis, specificity and sensitivity, reproducibility and ease of interpretation. Molecular characterisation studies allow us to distinguish between closely related infectious agents and to document the patterns of transmission of 'strains' and species within populations. This will allow precise determinations to be made about the aetiological agent, its characteristics and the source of infection. This review focuses on recent detection and characterisation techniques for both emerging and re-emerging parasite zoonoses.     

Behavioural and phylogeographic observations on Epipomponia nawai (Dyer, 1904): An East Asian moth (Lepidoptera; Epipyropidae) whose larvae are ectoparasitic on cicadas (Hemiptera; Cicadidae; Sonatini)

The lepidopteran family of the Epipyropidae contains currently 32 known species of moths with larvae that are parasitic on plant and leafhoppers as well as cicadas. This paper focuses on behavioural aspects of the final instar of the cicada parasite Epipomponia nawai (Dyer 1904) on the cicada Hyalessa maculaticollis (de Motschulsky 1866) and represents only the second report of the species from South Korea. This species is a new host for E. nawai in Korea, since in the past it had only been reported once from Meimuna opalifera and Oncotympana fuscata in Korea. Molecular relationships between specimens of E. nawai collected in China, Japan, and Korea were analysed. The Chinese haplotypes fell into two groups: one clearly related to the Korean haplotype, but the other tightly affiliated with the Japanese haplotype. The findings suggest two routes for the occurrence of E. nawai in mainland China. Once the host cicada was dead or too weak to move, the caterpillar crawled away from it, seeking a place to pupate. Very little is known about parasitic Lepidoptera and therefore any information on host species or behavioural aspects is of importance.     

Agricultural policy and sustainable livestock development

Future agricultural and rural development is, to a large extent, influenced by the projected food needs of 2.5 billion people expected to swell the world population by 2020. This increase will require more food in general and, in view of recent experience in East Asia, more animal products. To achieve this increase will require judicious use of resources, and trade, especially in those countries where natural resources are insufficient to support food production. Achieving food sufficiency in a sustainable manner is a major challenge for farmers, agro-industries, researchers and governments. The latter play an important role as many of the farmers' choices are, to a large extent, directed by government or supra-government, often through macro- and micro-economic policy. In many countries the economic, environmental, trade and agricultural policies have not been conducive to an agricultural development that is risk-free with respect to the environment, animal welfare or public health. The recent decline of government support in agriculture forced farmers in Western countries to think about more risk adverse agricultural practices and more efficient production systems. On the other hand, many countries in Eastern Europe and the former Soviet Union, as well as other developing countries, are still going through a painful process of adjustment to new market conditions. International banks and development agencies have a mandate to help developing countries, but are somewhat restricted both by needing to work directly with governments and by their perceived dogmatic approach to development. Changing policies do, now and in the future, also affect the development of animal disease control programmes, including the control of parasitic diseases. On the one hand there is an increasing interest in risk-free control practices, and on the other hand a demand for greater regulatory control over the production process. As parasitic diseases of animals are closely linked to the environment (i.e. grazing and waste management) and public health (i.e. parasitic zoonoses), the new interest in sustainable agriculture provides a challenge for those concerned with the control and prevention of animal parasitism.