Advances in Parasitology最新文献

Zoonotic parasites, including Toxocara species, of pet and stray cats are of public health importance. Justification for, and the design and implementation of prevention and control of human toxocariasis may benefit from an understanding of the zoonotic potential and prevalence of parasites in this definitive host species. This is the first systematic review and meta-analysis of cross-sectional studies, conducted to estimate the prevalence of Toxocara infection(s) in cats by geographical location, type (rural vs urban and stray vs pet), gender and age. Pooled data were assessed using a random effects-model as well as several meta-regression and stratified analyses conducted. Of 1733 peer-reviewed articles, 143 were included in this review and represented 2,158,069 cats from 51 countries. The global pooled (95% CI) prevalence of Toxocara infection in cats was 17.0% (16.1-17.8%), being highest in African (43.3%, 28.3-58.4%) and lowest in South American (12.6%, 8.2-17.0%) countries. In other WHO regions, prevalence rates of Toxocara were as follows: Eastern Mediterranean (21.6%, 15.1-28.1%), North America (18.3%, 15.4-21.2%), Europe (17.8%, 15.9-19.7%), Western Pacific (17.3%, 14.7-19.9%), and South-East Asia (14.9%, 9.8-20.1%). Prevalence of Toxocara was higher in low-income tropical countries and also in stray (28.6%, 25.1-32.1%) and young (≤12 months of age) (27.7%, 23.4-32.0%) cats than in pet (11.6%, 10.7-12.5%) and older cats (>12 months of age) (23.8%, 14.8-32.7%). This review indicates that ~118-150 million cats worldwide serve as definitive hosts of Toxocara, shedding eggs and thus contributing to the public health risk of human infection. Prevention and control of this zoonosis in cats should receive greater attention by health officials and cat owners, particularly in countries where risk factors and prevalence are highest.

Background: Human toxocariasis occurs worldwide and is caused by nematodes of the species of the genus Toxocara. Infection occurs by the ingestion of eggs and is usually asymptomatic or oligosymptomatic. However, severe manifestations occur. The burden of disease and its public health impact remain ill-defined. The aim of this review was to summarize all available data on the seroprevalence of toxocariasis on the African continent and factors associated with seropositivity.

Methods: Twenty-seven original papers published between 1991 and 2017 were identified that provided data suitable for this review. Case-control studies were included and the seroprevalence in the (healthy) control group was used as a surrogate parameter.

Results: Antibodies against Toxocara spp. were found to be frequent in most populations and regions in Africa with the exception of two publications, one from the Democratic Republic of the Congo and one from Djibouti, where all participants were seronegative. The highest proportion of participants with antibodies was found on the island of La Réunion with 359 out 387 study participants being positive (92.8%). Factors associated with seropositivity were reported across studies, including-among others-older age, contact with soil via geophagia, agricultural activity or playing with soil, contact with animals, especially dogs, and low socio-economic status, defined as absence of water supply or poor housing. Three Egyptian studies found male gender to be associated with toxocariasis, whereas in La Réunion females were at increased risk.

Conclusions: Exposure to toxocariasis seems to be very frequent and common in large parts of the African continent. However, no data are available for most countries. The public health impact of human toxocariasis and the frequency of severe manifestations remain unclear.

Soil-transmitted helminthiases (STHs) have been widely transmitted in China and the control of STHs was initiated by NIPD-CTDR since its foundation. Three national surveys on STHs have been carried out in China, and the infection rate has dropped from 53.58% in the first national survey (1988-92) to 4.49% in the third national survey (2014-16) due to strong interventions including mass drug administration, health education and environment improvement. National surveillance of STHs started in 2006 and has been implemented successively until now, which allows to understand the endemic status and trends of STHs prevalence in China. Surveillance has been expanded to 30 provinces of China since 2016. Integrated pilot programmes have been implemented between 2006 and 2009, in which an integrated strategy, with health education and control of infection sources as key components, was adopted. Since 2019, new control pilots have been started, which will be continued for five successive years to further explore appropriate control strategies in the current "new era". With the decline of infection rate of STHs, China is approaching the elimination stage for STHs. In order to achieve this final target, poverty alleviation programmes should be integrated with precise control measures, according to real situations.

The analysis of epidemiological data has played an important role for the academic research carried out by the National Institute of Parasitic Diseases, China CDC, since its foundation in 1950s. Those researches, e.g., the temporal-spatial patterns of disease transmission and the identification of risk factors, have contributed significantly to the national parasitic disease control and elimination programmes in China. With the development and application of epidemiological data analysis in the last decade, all research results improve our understanding of parasitic diseases epidemiology and related health issues through the application platform of epidemiological big data and analytical tools. In particular, implementation research on analytical predictions on disease outbreak or epidemic risks have provided references to the scientific guidance on effective preventions and interventions in the parasitic disease elimination in China, such as fliariasis, malaria and schistosomiasis. This review has reflected the function of data accumulation and application of temporospatial tools in parasitic diseases control, and the ways of the NIPD's sustained contributions to the disease control programmes in China.

Giardia intestinalis is a unicellular protozoan parasite that infects the small intestines of humans and animals. Giardiasis, the disease caused by the parasite, occurs globally across socioeconomic boundaries but is mainly endemic in developing countries and particularly within young children, where pronounced effects manifests in a failure to thrive condition. The molecular pathogenesis of Giardia has been studied using in vitro models of human and rat intestinal epithelial cells (IECs) and parasites from the two major human genotypes or assemblages (A and B). High-quality, genome sequencing of representative isolates from assemblages A (WB) and B (GS) has enabled exploration of these host-parasite models using 'omics' technologies, allowing deep and quantitative analyses of global gene expression changes in IECs and parasites during their interactions, cross-talk and competition. These include a major up-regulation of immune-related genes in the IECs early after the start of interactions, as well as competition between host cells and parasites for nutrients like sugars, amino acids and lipids, which is also reflected in their secretome interactions. Unique parasite proteins dominate these interactions, with many major up-regulated genes being either hypothetical proteins or members of Giardia-specific gene families like the high-cysteine-rich membrane proteins (HCMPs), variable surface proteins (VSPs), alpha-giardins and cysteine proteases. Furthermore, these proteins also dominate in the secretomes, suggesting that they are important virulence factors in Giardia and crucial molecular effectors at the host-parasite interface.

Dogs serve as the most important definitive hosts for Toxocara canis-a causative agent of human toxocariasis and one of the most widespread zoonotic helminth worldwide. The present study was undertaken to assess the global prevalence of T. canis infection in dogs. PubMed, Scopus, Web of Science, EMBASE and SciELO were searched to identify relevant studies. A random-effects model was used to estimate the overall and the subgroup-pooled prevalences across studies, and heterogeneity was assessed via the I² test. The data were categorized according to WHO-region, different types of dogs, risk factors and environmental variables. From a total of 4370 peer-reviewed publications, 229 articles that studied 13,010,004 dogs in 60 countries met the final inclusion criteria. The overall prevalence of Toxocara infection in dogs was 11.1% (95% CI, 10.6-11.7%). The estimated prevalence in the different WHO-regions ranged from 6.4% to 19.2%: Eastern Mediterranean (19.2%, 13.7-25.5%), Africa (18.5%, 13.7-23.9%), South-East Asia (11.9%, 6.8-18.2%), North America (11.1%, 10.6-11.7%), South America (10.9%, 7.6-14.6%), Europe (10.8%, 8.9-12.9%) and Western Pacific (6.4%, 3.3-10.2%). Young (<1 year of age), stray, rural and male dogs had a significantly (P<0.001) higher prevalence of infection than older, pet, urban or female dogs. The prevalence was higher in low income countries and regions at a low geographical latitude, close to the equator, characterized as having tropical climates. From this review, it is estimated that ≥100 million dogs are infected with Toxocara around the world. This highlights the need for an increased focus on implementing affordable, appropriate control programs to reduce the public health threat of toxocariasis as a zoonosis of global importance.

Toxocariasis in humans is considered a rare disease in Turkey, and the absence of specific symptoms of this disease is probably the main reason for clinicians to underestimate and underdiagnose the disease. Although there are several seroepidemiological studies on visceral larva migrans in the country, a comparison between them is difficult as the serological tests are not standardised. After the introduction of the easily accessible ELISA kit in the market, the number of seroepidemiological studies has increased in which the reported rates ranged between 1% and 56%. Similar to other countries, Toxocara seropositivity in Turkey is more common in men, childhood, in those living in rural area, having a low income level, owning dogs, and biting their nails or practicing geophagia. In addition, toxocariasis is a risk factor for veterinarians, farmers, and pet-shop workers. Toxocara seroprevalence is significantly higher in respiratory, neuropsychiatric, musculoskeletal, skin and abdominal disorders. There are also many studies showing the importance of eosinophilia in toxocariasis. In conclusion, although there are many studies on toxocariasis in Turkey, it is still not well understood to what extent the infection is responsible for a plethora ascribed symptoms. Standardisation of the diagnostic methods and the use of molecular techniques could further throw light in the real epidemiology and the role played by the infection to induce signs and symptoms.

Toxocara species are intestinal helminths of dogs and cats, the larval stages of which may infect humans and cause severe neural, ocular and visceral larva migrans disease. Such cases of severe overt disease represent only a small fraction of the of the US population who have been exposed and infected with Toxocara, subsequently developing IgG antibodies to the larvae. The true impact of exposure to Toxocara in this large group of Americans remains uncertain. Toxocara antibody positivity is associated with poverty, but other specific risk factors have been identified, including sex, age, rural residence, region of residence, race and exposure to pets. This seropositive status has also been associated with several childhood diseases, including asthma and epilepsy, increased serum lead levels, and poor neurocognitive function. Three large-scale NHANES studies have provided comprehensive datasets, while several smaller studies have explored specific disease associations. Each seroprevalence study must be interpreted in consideration of the sensitivity and specificity of the individual serological methods employed. This chapter summarizes all historical Toxocara prevalence data from dogs, cats and soil in the United States. It then carefully examines all previous human Toxocara seroprevalence surveys performed in the United States. Data from these surveys is assimilated, compared and discussed to determine the validity of findings and to accurately identify risk factors for Toxocara seropositivity. The validity of associations of exposure to Toxocara larvae and childhood diseases such as asthma and epilepsy and effects neurocognitive function within the American context are also explored.

This review covers the systematics and nomenclature of the Ascaridoid genus toxocara, and more specifically the species Toxocara canis and Toxocara cati. Also discussed is the discovery of the persistence of these larvae in the tissues of paratenic hosts, and the role that other species of this genus might or could play in other such hosts; including those where the life cycle has been described, i.e., Toxocara vitulorum, Toxocara pteropodis, Toxocara mackerrasae, and Toxocara tanuki. Also examined is the work that led to the realization that the larval stage leaving the egg actually being a third rather than a second stage larva. Also discussed on the work showing that the larvae can persist in paratenic host with remarkable longevity without undergoing any morphological change for years and that these larvae can be transmitted from one paratenic host to another by ingestion. People are usually infected by the ingestion of eggs containing third-stage larvae, but infections also occur on occasions from the ingestion of uncooked paratenic hosts.

China was once one of the most heavily endemic for lymphatic filariasis (LF), with a heavy disease burden. Due to decades of sustained efforts, LF was eliminated from China in 2007. The historical tales in the control and elimination of LF in China and current post-elimination surveillance are reviewed and concluded. In the course of LF control and elimination, National Technical Steering Group for Filariasis Control and Research, and Collaborating Research Group on the Transmission Threshold of Filariasis, led by the National Institute of Parasitic Diseases, carried out researches, developed control measures, and applied in practical control and surveillance. The main of the results include: in theoretical study, (1) formulating the microfilaria rate below 1% as the transmission threshold of filariasis, (2) developing anti-filarial drugs and establishing animal model for drug screening, (3) studying the vectorial capacity of mosquitoes transmitted filariasis; in clinical diagnostic and therapy, (1) developing antigens for serological diagnostics, (2) studying different administration regimes for alleviating the side-response of diethylcarbamazine (DEC), (3) studying on the recurrence of acute adenolymphangitis and lymphadenitis of malayan filariasis, (4) observing lymphoedema of the lower extremity using lymphangiography; in practical control and surveillance, (1) establishing the control strategy taking elimination of infection source as the major focus, (2) formulating safe, feasible and effective DEC-mass drug administration, (3) revealing the transmission pattern of filariasis at the post-control phase, (4) establishing comprehensive active surveillance system, (5) formulating the criteria of basic elimination and elimination of filariasis. In the post-elimination surveillance phase, special monitoring and investigation in key areas were conducted for clearing way potential residual infection sources. Two schemes on LF surveillance in the post-elimination phase and caring for chronic filariasis patients were issued to maintain the diagnosis and treatment skills of filariasis all levels of disease control and prevention workers in future. Also, the Notifiable Diseases Reporting System, which included LF in 2004, plays an important role in LF post-elimination surveillance to prevent LF resurgence in China. The strategies and measures of LF control, elimination and post-elimination surveillance in China provide valuable practical experience and promote the progress of Global Programme of Elimination of Lymphatic Filariasis in worldwide.