Control of hydatidosis

Using a One Health approach to prioritize zoonotic diseases in China, 2019

Background

China is vulnerable to zoonotic disease transmission due to a large agricultural work force, sizable domestic livestock population, and a highly biodiverse ecology. To better address this threat, representatives from the human, animal, and environmental health sectors in China held a One Health Zoonotic Disease Prioritization (OHZDP) workshop in May 2019 to develop a list of priority zoonotic diseases for multisectoral, One Health collaboration.

Methods

Representatives used the OHZDP Process, developed by the US Centers for Disease Control and Prevention (US CDC), to prioritize zoonotic diseases for China. Representatives defined the criteria used for prioritization and determined questions and weights for each individual criterion. A review of English and Chinese literature was conducted prior to the workshop to collect disease specific information on prevalence, morbidity, mortality, and Disability-Adjusted Life Years (DALYs) from China and the Western Pacific Region for zoonotic diseases considered for prioritization.

Results

Thirty zoonotic diseases were evaluated for prioritization. Criteria selected included: 1) disease hazard/severity (case fatality rate) in humans, 2) epidemic scale and intensity (in humans and animals) in China, 3) economic impact, 4) prevention and control, and 5) social impact. Disease specific information was obtained from 792 articles (637 in English and 155 in Chinese) and subject matter experts for the prioritization process. Following discussion of the OHZDP Tool output among disease experts, five priority zoonotic diseases were identified for China: avian influenza, echinococcosis, rabies, plague, and brucellosis.

Conclusion

Representatives agreed on a list of five priority zoonotic diseases that can serve as a foundation to strengthen One Health collaboration for disease prevention and control in China; this list was developed prior to the emergence of SARS-CoV-2 and the COVID-19 pandemic. Next steps focused on establishing a multisectoral, One Health coordination mechanism, improving multisectoral linkages in laboratory testing and surveillance platforms, creating multisectoral preparedness and response plans, and increasing workforce capacity.

Review on Epidemiology and Public Health Significance of Hydatidosis

Hydatidosis is a zoonotic parasitic disease caused by larval stages (hydatid cysts) of cestodes belonging to the genus Echinococcus and the family Taeniidae. Hydatid cyst, which is the larval stage of Echinococcus, is a bladder-like cyst formed in various organs and tissues following the growth of the oncospheres of an Echninoccus tape worm in that specific organ or tissue. The epidemiology and control of hydatidosis is often considered to be a veterinary matter since the disease can be regulated by controlling parasites in animals. However, collaboration between veterinarians and public health workers is essential for the successful control of hydotidosis. Therefore, the objective of this paper was to review The epidemiology, economic and public health importance of hydatidosis. The developmental stage of Echinococcus is that eggs develop to oncospheres, this oncospheres develop to hydatid cyst in the intermediate host and the hydatid cyst if consumed by final host develops to the adult Echinococcus. Human echinococcosis is a zoonotic infection caused by the tape worm of the genus Echinococcus. Echinococcus granucosus granulosis cause cystic echinococcosis (CE), Echinococcus multilocularis cause alveolar echinoloccosis (AE), and Echinococcus vogeli and Echinococcus oligarthus cause polycystic echinococcosis (PE). From these Echinococcus mulitilocularis is rare but is the most virulent, Echinococcus vegeli and Echinococcus oligarthus are the rarest. Hydatidosis is a zoonotic cosmopolitan parasitic disease found in almost all countries of the world. This disease causes a significant economic loss directly by causing organ or carcass condemnation and indirectly by affecting human and animal health which increase the cost for diagnosis, treatment and control of the disease. Public awareness creation about the transmission and control of the disease and its public health significance and collaboration between veterinarians and public health workers in the prevention and control of the disease is mandatory.

Knowledge, attitudes and practices regarding echinococcosis in Xizang Autonomous Region, China

Background

Echinococcosis is a neglected zoonotic parasitic disease caused echinococcus parasitizes, poseing a significant economic burden on both humans and animals. There are limited studies on echinococcosis in China, especially Xizang Autonomous Region, although the area is endemic area for echinococcosis. The study aimed to provide information for strategic prevention against this disease.

Methods

A cross-sectional survey was conducted among the residents in Xizang Autonomous Region, China to evaluate their knowledge, attitudes and practices on endemicity of echinococcosis. A face-to-face survey was conducted to collect the data using a well-designed questionnaire. The contents included basic personal information, knowledge, attitudes and practices about echinococcosis, personal hygiene and behavior habits, dog feeding and whether they had received the information on echinococcosis, and so on. We surveyed 840 persons in practice. All data analysis was performed using Epi Info 7.2.

Results

Of the total particpants, 86.8% had a primary education level or below (including primary and illiterate), and even 45.0% were illiterate. Farmers and herdsmen represent the main occupations in this study. People who know all the echinococcosis-related knowledge in the questionnaire only accounted for 8.7% of the participants. However, none of the participants was aware of routes of echinococcosis infection in human or dogs. The data showed participants with higher educational background had the high awareness rate of echinococcosis-related knowledge or attitudes (chi-square for trend, χ² = 21.23, p<0.05 & χ² = 48.43, p<0.05). In addition, The percentage of the participant with awareness of echinococcosis-related practices was associated with their age and principle occupation (χ² = 52.72, p<0.05 & χ² = 20.63, p<0.05).

Conclusions

Xizang Autonomous Region is an epidemic area of Echinococcosis. The prevalence of the disease has been largely due to the lack of knowledge, awareness, and poor hygiene practice in local residences. Therefore, effective disease prevention education and awareness campaigns in community will be significantly helpful in prevention and control of echinococcosis.

Echinococcosis transmission on the Tibetan Plateau

Since the mid-1990s detailed studies and field investigations on the Tibetan Plateau have revealed human echinococcosis to be an under-reported major public health problem, particularly in the dominant pastoral communities in the eastern and central regions. Human prevalence surveys showed that cystic echinococcosis (CE, caused by Echinococcus granulosus) and alveolar echinococcosis (AE, caused by Echinococcus multilocularis) are co-endemic with higher burdens of each disease than other endemic world regions. Epidemiological investigations identified some major risk factors for human CE and AE including dog ownership, husbandry practices and landscape features. Dogs appear to be the major zoonotic reservoir for both E. granulosus and E. multilocularis, but the latter is also transmitted in complex wildlife cycles. Small mammal assemblages especially of vole and pika species thrive on the Plateau and contribute to patterns of E. multilocularis transmission which are influenced by landscape characteristics and anthropogenic factors. Tibetan foxes are a principal definitive host for both E. multilocularis and E. shiquicus. In 2006 a national echinococcosis control programme was initiated in Tibetan communities in northwest Sichuan Province and rolled out to all of western China by 2010, and included improved surveillance (and treatment access) of human disease and regular deworming of dogs with annual copro-testing. Control of echinococcosis in Tibetan pastoral communities poses a difficult challenge for delivery and sustainability.

Praziquantel treatment of dogs for four consecutive years decreased the transmission of Echinococcus intermedius G7 to pigs in villages in Lithuania

Echinococcus granulosus sensu lato comprises a number of recognized species which cause cystic echinococcosis (CE) in humans and intermediate hosts. These species have particular geographic distributions, with E. granulosus sensu stricto (genotypes G1/2/3 and micro variants) being most widely spread. In Lithuania, E. intermedius (G7) is known to be the only species circulating between pigs and dogs but is also infecting cattle and humans. In fact, recent reports showed a rise of the incidence to 1.13 human cases/100,000 inhabitants/year. Most of the pigs reared on the backyard farms in Lithuania are slaughtered on site during the cold season (October–April) and are used for own consumption. Therefore, in this study, we examined the impact on taeniid transmission of treating dogs with baits containing an oral formulation of praziquantel every two months during the pig slaughtering season in endemic villages in Lithuania. This study started in November 2006 and ended in January 2011; the first dog treatment was administered in February 2007. The results show that the prevalence of E. intermedius, E. multilocularis and Taenia spp. decreased significantly in treated dogs from the second year of the study when compared to untreated dogs. The treatment of dogs also had an impact on reducing the incidence of CE in fattener pigs from 17.6% (2006-2007) to 3.8% (2008; P < 0.05) and in sows from 26.9% (2006-2007) to 3.6% (2008), and eventually to zero in 2010 (P < 0.05) in fatteners and sows as compared to animals from “control” areas (30.7% and 63.7%, respectively). The results document a significant decrease in the transmission of E. intermedius (G7) after treatment of dogs with praziquantel in a relatively short time on farm level in Lithuania. Taeniid prevalence in dogs remained low in 2017 in the areas where anthelmintic intervention was performed until 2010 and, surprisingly, it was also strongly reduced in control areas. Reduction of taeniid transmission is likely associated with a decrease in the number of dogs in the villages as well as an overall decline in backyard pig farming after 2014 due to the outbreaks of African swine fever in Lithuania.

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The prevalence of E. intermedius, E. multilocularis and Taenia spp. decreased significantly in dogs treated strategically during the home slaughter season for pigs.

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Dog treatment also reduced the incidence and intensity of CE in fattener pigs and sows.

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Treatment should target all dogs, not just free-roaming dogs.

Community perception and knowledge of cystic echinococcosis in the High Atlas Mountains, Morocco

Background

Cystic echinococcosis (CE), a neglected zoonosis caused by the larval stage of the tapeworm Echinococcus granulosus, remains a public health issue in many developing countries that practice extensive sheep breeding. Control of CE is difficult and requires a community-based integrated approach. We assessed the communities’ knowledge and perception of CE, its animal hosts, and its control in a CE endemic area of the High Atlas Mountains, Morocco.

Methods

We conducted twenty focus group discussions (FGDs) stratified by gender with villagers, butchers and students in ten Berber villages that were purposefully selected for their CE prevalence.

Results

This community considers CE to be a severe and relatively common disease in humans and animals but has a poor understanding of the parasite’s life cycle. Risk behaviour and disabling factors for disease control are mainly related to cultural practices in sheep breeding and home slaughtering, dog keeping, and offal disposal at home, as well as in slaughterhouses. Participants in our focus group discussions were supportive of control measures as management of canine populations, waste disposal, and monitoring of slaughterhouses.

Conclusions

The uncontrolled stray dog population and dogs having access to offal (both at village dumps and slaughterhouses) suggest that authorities should be more closely involved in CE control. This study also highlights the need for improved knowledge about the transmission cycle of the parasite among communities and health professionals. Inter-sectoral collaboration between health staff, veterinarians, and social scientists appears to be crucial for sustainable control of this parasitic zoonosis.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-6372-y) contains supplementary material, which is available to authorized users.

A study to assess the awareness of risk factors of cystic echinococcosis in Turkey

OBJECTIVES

To determine the knowledge, attitudes, practices, and awareness for risk factors associated with cystic echinococcosis (CE) among animal breeders, nurses, nursing students, dietitians, food professionals and other public groups in Turkey. Methods: Questionnaire forms were prepared in compliance with the individuals' diversity, and a survey was created about agents, transmission modes, epidemiology, treatment, and risk factors for CE. The descriptive survey was performed between May 2015 and May 2016 by face-to-face communication. Data were collected from a total of 647 individuals, including 95 animal breeders, 92 nurses, 249 nursing students, 49 dietitians, 28 food professionals and 134 people from other public groups from Turkey. Survey data were evaluated in terms of percentages and means and analyzed by the Pearson's chi-square test and Mann-Whitney U test to determine the relationships between questionnaire answers and socio-demographic attributes, such as age, gender, educational level, and profession. Non-categorical variables were compared via Spearman's rho correlation analysis with statistical significance set at the 0.05 level. Results: We determined low awareness for vegetable washing, raw vegetables and offal consumption, informative courses, contact with dogs, and administration of antiparasitic drugs to dogs. Conclusion: The participants of this survey were found to be with insufficient knowledge regarding risk factors of CE. We advocate the implementation of training programs to improve public awareness on this important disease.

Knowledge, attitudes, and practices regarding cystic echinococcosis and sheep herding in Peru: a mixed-methods approach

BACKGROUND

The parasitic disease, cystic echinococcosis (CE), is prevalent in low-income, livestock-raising communities and 2000 new people will be diagnosed this year in South America alone. The disease usually passes from livestock to dogs to humans, making it a zoonotic disease and part of the One Health Initiative. Control of CE has been infamously difficult; no endemic areas of South America have succeeded in maintaining sustainable eradication of the parasite. For the current study, we aimed to gain a better understanding of the knowledge, attitudes, and practices of rural sheep farmers and other community leaders regarding their sheep herding practices and perspectives about a control program for CE. We also hope to identify potential barriers and opportunities that could occur in a control program. The authors conducted Knowledge, Attitude and Practices (KAP) surveys and semi-structured interviews in rural communities in the highlands of Peru. The KAP surveys were administered to 51 local shepherds, and the semi-structured interviews were administered to 40 individuals, including shepherds, community leaders, and health care providers.

RESULTS

We found that the shepherds already deworm their sheep at a median of 2 times per year (N = 49, range 2-4) and have a mean willingness-to-pay of U.S. $ 0.60 for dog dewormer medication (N = 20, range = 0.00- $2.00 USD). We were not able to learn the deworming agent or agents that were being used, for neither sheep nor dogs. Additionally, 90% of shepherds slaughter their own sheep (N = 49). We also learned that the main barriers to an effective control program include: lack of education about the cause and control options for CE, accessibility to the distant communities and sparse grazing pastures, and a lack of economic incentive.

CONCLUSIONS

Findings suggest it may be feasible to develop an effective CE control program which can be used to create an improved protocol to control CE in the region.

Echinococcosis: Control and Prevention

Human cystic echinococcosis (CE) has been eliminated or significantly reduced as a public health problem in several previously highly endemic regions. This has been achieved by the long-term application of prevention and control measures primarily targeted to deworming dogs, health education, meat inspection, and effective surveillance in livestock and human populations. Human CE, however, remains a serious neglected zoonotic disease in many resource-poor pastoral regions. The incidence of human alveolar echinococcosis (AE) has increased in continental Europe and is a major public health problem in parts of Eurasia. Better understanding of wildlife ecology for fox and small mammal hosts has enabled targeted anthelmintic baiting of fox populations and development of spatially explicit models to predict population dynamics for key intermediate host species and human AE risk in endemic landscapes. Challenges that remain for echinococcosis control include effective intervention in resource-poor communities, better availability of surveillance tools, optimal application of livestock vaccination, and management and ecology of dog and wildlife host populations.

Echinococcus granulosus infection in dogs in Sidi Kacem Province (North-West Morocco)

This study was undertaken in the Province of Sidi Kacem in northwest Morocco between April 2010 and March 2011. The main objective of the study was to determine the prevalence of Echinococcus granulosus (Eg) infection in owned dogs. This province was selected as a case study because of the social conditions, geographic and climatic diversity making it a model representative of many parts of Morocco. The survey was carried out in 23 rural communes and in the 5 municipalities (urban districts) of the Province and sampling was undertaken in randomly selected households. A total of 273 owned dogs comprising 232 from the 23 rural communes (rural dogs) and 41 from the 5 municipalities (urban dogs) were tested. Arecoline hydrobromide purgation was selected as the diagnostic method of choice to enable visualisation of expelled worms by dog owners, thereby imparting messages on the transmission mode of Eg to humans and farm animals. Of the 273 dogs tested, purgation was effective in a total of 224 dogs (82.1%). The overall estimated prevalence of Eg infection was 35.3% (79/224, 95% CI 22.3-47.0%). Dogs inhabiting rural communes were at greater risk of infection (38.0%, 95% CI 31.1-45.3%) than dogs roaming in municipalities or urban areas (18.8%, 95% CI 7.2-36.4%) and the prevalence of infection was higher in those inhabiting rural communes with slaughterhouses (62.7%, 95% CI 48.1-75.9%) than in communes without (29.1%, 95% CI 21.7-37.2%). This first assessment of Eg infection in Sidi Kacem Province indicates a key role of rural slaughterhouses in parasite transmission to dogs.

Serology and longevity of immunity against Echinococcus granulosus in sheep and llama induced by an oil-based EG95 vaccine

An oil-based formulation of the EG95 vaccine to protect grazing animals against infection with Echinococcus granulosus was formulated in Argentina. The efficacy of the vaccine was monitored by serology in sheep and llama (Lama glama) and was compared to the serology in sheep previously published using a QuilA-adjuvanted vaccine. Long-term efficacy was also tested in sheep by challenging with E. granulosus eggs of the G1 strain 4 years after the beginning of the trial. The serological results for both sheep and llama were similar to those described previously, except that there was a more rapid response after the first vaccination. A third vaccination given after 1 year resulted in a transient boost in serology that lasted for about 12 months, which was similar to results previously described. Sheep challenged after 4 years with three vaccinations presented 84·2% reduction of live cysts counts compared with control group, and after a fourth vaccination prior to challenge, this reduction was 94·7%. The oil-based vaccine appeared to be bio-equivalent to the QuilA vaccine.

Dog population management for the control of human echinococcosis

Cystic and alveolar hydatid disease of humans caused by infection with Echinococcus granulosus or Echinococcus multilocularis are significant zoonoses in developing countries. For human infections, the main definitive host is the dog, and reduction in the population of unwanted dogs, together with anthelmintic treatment of wanted dogs, are recommended control procedures for these zoonoses. Both owned and unowned dogs have been shown to be a major source of Echinococcus spp. infection in developing countries. Unowned dogs are the most challenging category in dog population management for the control of major zoonotic diseases. Unowned dogs are those dogs that do not have an owner, and those dogs whose owner cannot readily be identified. Control of numbers of unowned dogs can be done in various ways if funds are available. Fertility control and humane euthanasia are likely to be the most effective procedures in developing countries. Fertility control requires significant funding, and where resources are scarce humane euthanasia may be the most effective option. Both procedures are ongoing events, with no predictable end point. This paper examines the sociology and technology for the population management of owned and unowned dogs, specifically for the reduction of human hydatid disease. Examples are given for developing and developed countries. Although a "One Health" approach is desirable, the technology for hydatid control is different from that for rabies, and FAO Animal Welfare recommendations for dog population management should be adjusted accordingly.

A comparison of loop-mediated isothermal amplification (LAMP) with other surveillance tools for Echinococcus granulosus diagnosis in canine definitive hosts

BACKGROUND

Cystic echinococcosis is highly prevalent in northwest China. A cost-effective, easy to operate diagnostic tool with high sensitivity and specificity would greatly facilitate the monitoring of Echinococcus infections in canine definitive hosts.

METHODS

The primers used in the LAMP assay were based on the mitochondrial nad5 gene of E. granulosus sensu stricto (E. granulosus s.s., or E.g.s.s.) and were designed using Primer Explorer V4 software. The developed LAMP assay was compared with a conventional PCR method, copro-ELISA and microscopy, using the faeces of dogs experimentally infected with E.g.s.s., and field-collected faeces of domestic dogs including 190 from Qinghai province highly endemic for E.g.s.s. and 30 controls from an area in Gansu, where a domestic dog de-worming program was in operation.

RESULTS

The positivity rates obtained for the field-collected faecal samples were 12.6%, 1.6% and 2.1% by the LAMP, PCR and copro-ELISA assays, respectively. All samples obtained from the control dogs were negative. Compared with the conventional PCR, the LAMP assay provided 88.8% specificity and 100% sensitivity. The higher sensitivity of the LAMP method was also shown by the fact that it could detect the presence of laboratory challenge dog infections of E. granulsous s.s. four days earlier than the PCR method. Three copro-samples shown positive by the commercial copro-ELISA were all negative by LAMP, PCR and microscopy, which suggests these samples may have originated from another infection rather than E. granulsous s.s., possibly E. shiquicus or E. Canadensis, which is also present in China.

CONCLUSIONS

We have developed a potentially useful surveillance tool for determining the prevalence of canine E. granulosus s.s. infections in the field. The LAMP assay may lead to a more cost-effective and practicable way of tracking Echinococcus infections in canids, especially when combined with the copro-ELISA.

A village-based multidisciplinary study on factors affecting the intensity of cystic echinococcosis in an endemic region of the Tibetan plateau, China

We investigated and quantified the factors which may affect the prevalence of cystic echinococcosis caused by Echinococcus granulosus in Rangtang County using a multidisciplinary approach. From a previously performed field survey, epidemiological data were linked with environmental data. Altitude and land surface temperature were extracted from remote-sensing images. Cumulative logistic regression models were used to identify and quantify the potential risk factors. The multiple regression models confirmed that yaks (χ² = 4·0447, P = 0·0443), dogs (χ² = 8·3455, P = 0·0039) and altitude (χ2 = 7·6223, P = 0·0058) were positively correlated with the prevalence of cystic echinococcosis, while land surface temperature may have a negative association. The findings showed that dogs and yaks play the most important role in the transmission of cystic echinococcosis, while altitude and land surface temperature may also be involved in the transmission.

Pilot field trial of the EG95 vaccine against ovine cystic echinococcosis in Rio Negro, Argentina: early impact and preliminary data

Cystic echinococcosis is endemic in the Rio Negro province of Argentina. After 30 years of control using praziquantel in dogs the transmission rate to humans and sheep has decreased significantly, however transmission persists. The objective of the study is to assess the impact of the inclusion of the EG95 vaccine for sheep in the control programme, including analysis of the vaccine's operative feasibility in field conditions. The vaccine was applied in an area comprising four communities of native people including 79 farms with 3146 lambs and 311 dogs in total. Seventy one farms were designated as control areas where no vaccinations were undertaken while vaccinations of lambs undertaken on 91 farms. Lambs received two vaccinations with the EG95 vaccine followed by a single booster injection when the animals were 1-1.5 years of age. Farm locations were defined using GPS coordinates for the houses. Evidence for Echinococcus granulosus transmission was monitored by coproantigen ELISA on samples of dog faeces, by E. granulosus-specific PCR using soil samples, and anti-E. granulosus antibody assessments in sera from 2 to 4 teeth lambs, purgation of dogs to detect E. granulosus worms and necropsy on adult sheep. Before the vaccine was introduced, 26.2% of sheep with 2-4 teeth were positive using ELISA/WB, the prevalence decreased to 7.8% at the third year following use of the vaccine. Necropsy of animals older than 6 years (not vaccinated) showed that 66.1% of animals were infected with E. granulosus. In dogs, 4% was found positive for E. granulosus using arecoline purgation and 24.7% of the farms were infected using coproELISA/WB. During the first year of vaccination 2721 lambs received the first vaccine dose and 2448 received a booster. In the second year 2138 lambs were initially vaccinated and 1745 received a booster, and 1308 animals received the third dose. During the third year 1110 lambs received the first dose from which 539 received a booster and 723 animals received the third dose. An analysis of advantages and limitations of the diagnostic techniques used and the ability of the geospatial analysis to detect risk area are included. Based in the immunodiagnostic techniques, the EG95 vaccine has been able to prevent the infection in animals up to 3 years old. Also, the difficulties in the field for the correct vaccine administration and the social features and habits that may impact on echinococcosis control are included in the analysis.

Characterization of a surface glycoprotein from Echinococcus multilocularis and its mucosal vaccine potential in dogs

Alveolar echinococcosis is a refractory disease caused by the metacestode stage of Echinococcus multilocularis. The life cycle of this parasite is maintained primarily between foxes and many species of rodents; thus, dogs are thought to be a minor definitive host except in some endemic areas. However, dogs are highly susceptible to E. multilocularis infection. Because of the close contact between dogs and humans, infection of dogs with this parasite can be an important risk to human health. Therefore, new measures and tools to control and prevent parasite transmission required. Using 2-dimensional electrophoresis followed by western blot (2D-WB) analysis, a large glycoprotein component of protoscoleces was identified based on reactivity to intestinal IgA in dogs experimentally infected with E. multilocularis. This component, designated SRf1, was purified by gel filtration using a Superose 6 column. Glycosylation analysis and immunostaining revealed that SRf1 could be distinguished from Em2, a major mucin-type antigen of E. multilocularis. Dogs (n = 6) were immunized intranasally with 500 µg of SRf1 with cholera toxin subunit B by using a spray syringe, and a booster was given orally using an enteric capsule containing 15 mg of the same antigen. As a result, dogs immunized with this antigen showed an 87.6% reduction in worm numbers compared to control dogs (n = 5) who received only PBS administration. A weak serum antibody response was observed in SRf1-immunized dogs, but there was no correlation between antibody response and worm number. We demonstrated for the first time that mucosal immunization using SRf1, a glycoprotein component newly isolated from E. multilocularis protoscoleces, induced a protection response to E. multilocularis infection in dogs. Thus, our data indicated that mucosal immunization using surface antigens will be an important tool to facilitate the development of practical vaccines for definitive hosts.

A systematic review of the epidemiology of echinococcosis in domestic and wild animals

BACKGROUND

Human echinococcosis is a neglected zoonosis caused by parasites of the genus Echinococcus. The most frequent clinical forms of echinococcosis, cystic echinococcosis (CE) and alveolar echinococcosis (AE), are responsible for a substantial health and economic burden, particularly to low-income societies. Quantitative epidemiology can provide important information to improve the understanding of parasite transmission and hence is an important part of efforts to control this disease. The purpose of this review is to give an insight on factors associated with echinococcosis in animal hosts by summarising significant results reported from epidemiological studies identified through a systematic search.

METHODOLOGY AND PRINCIPAL FINDINGS

The systematic search was conducted mainly in electronic databases but a few additional records were obtained from other sources. Retrieved entries were examined in order to identify available peer-reviewed epidemiological studies that found significant risk factors for infection using associative statistical methods. One hundred studies met the eligibility criteria and were suitable for data extraction. Epidemiological factors associated with increased risk of E. granulosus infection in dogs included feeding with raw viscera, possibility of scavenging dead animals, lack of anthelmintic treatment and owners' poor health education and indicators of poverty. Key factors associated with E. granulosus infection in intermediate hosts were related to the hosts' age and the intensity of environmental contamination with parasite eggs. E. multilocularis transmission dynamics in animal hosts depended on the interaction of several ecological factors, such as hosts' population densities, host-prey interactions, landscape characteristics, climate conditions and human-related activities.

CONCLUSIONS/SIGNIFICANCE

Results derived from epidemiological studies provide a better understanding of the behavioural, biological and ecological factors involved in the transmission of this parasite and hence can aid in the design of more effective control strategies.

A monoclonal antibody-based copro-ELISA kit for canine echinococcosis to support the PAHO effort for hydatid disease control in South America

Cystic echinococcosis is still a major concern in South America. While some regions show advances in the control of the disease, others have among the highest incidence in the world. To reverse this situation the Pan American Health Organization (PAHO) has launched a regional project on cystic echinococcosis control and surveillance. An early concern of the program was the lack of a standardized diagnostic tool to monitor infection in dogs, a key target of control programs. Under this premise, we have developed a new copro-ELISA test after extensive screening of a large panel of monoclonal antibodies (MAbs) and polyclonal sera, which performs with high standards of sensitivity (92.6%) and specificity (86.4%) as established by necropsy diagnosis of dogs. The key component of the test, MAbEg9 has a convenient IgG isotype and reacts with a periodate-resistant epitope found in high molecular weight components of the worm. Time-course analysis of experimentally infected dogs showed that even animals with a very low number of parasites could be detected as early as day 20 post infection. The test was formulated in a ready-to-use kit format with proven stability of each component for a minimum of 3 months at room temperature. This characteristic facilitates its standardized use and shipping to other laboratories, which was demonstrated by the identical results obtained by two different laboratories in Peru and our own laboratory when a large number of field samples were analyzed independently in a blind fashion.

Cystic echinococcosis, caused by infection with the larval stage of the Echinococcus granulosus tapeworm, is a life-threatening zoonosis of worldwide distribution. The adult worm parasitizes the small intestine of dogs, which become infected after eating offal of an animal contaminated with the parasite, and releases eggs into the environment that can be accidentally ingested by domestic animals or humans, maintaining the life cycle of the parasite. Deworming of dogs is a major component of control programs, and simple and reliable methods are needed to monitor the base-line infection in the canine population. The lack of these tests was recognized as a major obstacle to the PAHO effort to control the disease in South America. This paper describes the development of a diagnostic assay that detects parasite antigens in dog feces. The key component is a monoclonal antibody carefully selected to attain high levels of sensitivity and specificity, which were established with a large panel of field fecal samples obtained from animals diagnosed by necropsy. Several aspects of the long-term stability of the test were optimized to facilitate its shelf-life and transference to other laboratories.

Cystic echinococcosis in slaughtered domestic ruminants from Tunisia

A total of 10,818 domestic ruminants (3913 cattle, 2722 sheep, 3779 goats, 404 dromedaries) slaughtered in various abattoirs in Tunisia between 2003 and 2010 were examined for the presence of Echinococcus granulosus hydatid cysts. The prevalence of cystic echinococcosis (CE) was 16.42% in sheep, 8.56% in cattle, 5.94% in dromedaries and 2.88% in goats. CE prevalence increased with age according to an asymptotic model and there was evidence of variation in infection pressure depending on the region of Tunisia where the animals were slaughtered. Cattle appeared to have the highest infection pressure of the species examined. The mean intensity of hepatic cysts was higher than that of pulmonary cysts in all species. The highest mean intensity of infection with E. granulosus larvae was observed in cattle (18.14) followed by sheep (9.58), goats (2.31) and dromedaries (2.12). The abundance of infection increased in a linear fashion with age in all animal species. Cyst abundance varied with species of animal and district of Tunisia. Cysts from dromedaries were more fertile (44.44%) than those from sheep (30.25%), goats (30.32%) and cattle (0.95%). The viability of the protoscoleces from fertile cysts from cattle (78.45%) was higher than those from sheep (70.71%) and camels (69.57%). The lowest protoscolex viability was recorded for hydatid cysts from goats (20.21%). This epidemiological study confirms the importance of CE in all domestic ruminant species, particularly in sheep, throughout Tunisia and emphasizes the need to interrupt parasite transmission by preventive integrated approaches in a CE control programme.

Challenges for diagnosis and control of cystic hydatid disease

This paper is based on the experience of the authors, with the aim to define the challenges for Echinococcus granulosus (E.g./CE) diagnosis and control for those countries that may now or in the future be contemplating control of hydatid disease. A variety of methods are available for diagnosis in humans but a universal gold standard is lacking. Diagnosis in definitive hosts can avoid necropsy by the use of methods such as coproantigen detection but test performance is variable between populations. A sylvatic cycle adds challenges in some countries and the epidemiology of the parasite in these hosts is poorly understood. Control by solely administering praziquantel to dogs is not effective in developing countries where the disease is endemic. Additional avenues to pursue include the instigation of participatory planning, use of an existing vaccination for intermediate hosts and development of a vaccine and long-acting anthelmitic implants for definitive hosts. Promoting public acceptance of control of the dog population by humane euthanasia and reduced reproduction is also essential.

Gene cloning, expression, and localization of antigen 5 in the life cycle of Echinococcus granulosus

Antigen 5 (Ag5) has been identified as a dominant component of cyst fluid of Echinococcus granulosus and is considered as a member of serine proteases family, which in other helminth, plays an important role in the egg hatch and larva invasion. However, whether Ag5 is expressed and secreted in all life stages is unknown. In this study, according to the sequence in GenBank, we cloned and sequenced the open reading frame (ORF) of Ag5 gene from the protoscolices of E. granulosus isolated from the sheep in Qinhai Province of China, and found several substitutions and a base insert and deletion in a short region near the stop code, leading to a frameshift mutation which is conserved with the homologue of other cestode. The ORF is 1,455 bp in length, encoding 484 amino acids with a secretory signal peptide. Bioinformatics analysis predicted several phosphorylation and myristoylation sites and a N-glycosylation site and a species-specific linear B epitope in the protein. The ORF was cloned into the plasmid pET28a(+) vector and expressed in Escherichia coli . The recombinant protein was purified by affinity chromatography. Anti-rEgAg5 antiserum was prepared in rats and used to analyze the localization of Ag5 in protoscolex and adult worm by immunofluorescence technique. Results demonstrated that the Ag5 is strongly expressed in the tegument of protoscolex and the embryonic membrane of egg and surface of oncosphere; meanwhile, it is also weakly expressed in tegument of the adult. This study showed that Ag5 is expressed in all stages of life cycle, secreted from the surface of the worm and may be anchored in membrane by its myristoylation sites; these characteristics make it a candidate antigen for diagnosis and vaccine for both intermediate and definitive hosts.

[Study of lesional aspects of hydatid echinococcosis in man in Mauritania: fertility, histology of hydatid cysts and protoscolex viability]

A lesional study on human hydatidosis (localization, fertility of cysts, protoscolex viability, and histological structure) focused on 63 human hydatid cysts from patients operated at CHN of Nouakchott was conducted during the period 1997-2007. The authors report the following results: the annual surgical incidence rate was in the order of 1.2% per 100,000 inhabitants. The lung was the primary localization of cyst (52%) followed by the liver (33%), spleen (4%), brain (3%), heart (2%), breasts (2%), kidney (2%), diaphragm (1%), and peritoneum (1%). The pulmonary cysts were larger and more fertile (76%) with protoscoleces also more viable (70%) compared with liver cysts (67-62%). The histology of hydatid cysts revealed in most cases a histological structure consistent with that described in the literature: thick cuticle, membrane proligeous, and capsules visible.

Evaluation of oxfendazole, praziquantel and albendazole against cystic echinococcosis: a randomized clinical trial in naturally infected sheep

Background

Cystic Echinococosis (CE) is a zoonotic disease caused by larval stage Echinococcus granulosus. We determined the effects of high dose of Oxfendazole (OXF), combination Oxfendazole/Praziquantel (PZQ), and combination Albendazole (ABZ)/Praziquantel against CE in sheep.

Methodology/Principal Findings

A randomized placebo-controlled trial was carried out on 118 randomly selected ewes. They were randomly assigned to one of the following groups: 1) placebo; 2) OXF 60 mg/Kg of body weight (BW) weekly for four weeks; 3) ABZ 30 mg/Kg BW + PZQ 40 mg/Kg BW weekly for 6 weeks, and 4) OXF 30 mg/Kg BW+ PZQ 40 mg/Kg BW biweekly for 3 administrations (6 weeks). Percent protoscolex (PSC) viability was evaluated using a 0.1% aqueous eosin vital stain for each cyst. “Noninfective” sheep were those that had no viable PSCs; “low-medium infective” were those that had 1% to 60% PSC viability; and “high infective” were those with more than 60% PSC viability. We evaluated 92 of the 118 sheep. ABZ/PZQ led the lowest PSC viability for lung cysts (12.7%), while OXF/PZQ did so for liver cysts (13.5%). The percentage of either “noninfective” or “low-medium infective” sheep was 90%, 93.8% and 88.9% for OXF, ABZ/PZQ and OXF/PZQ group as compared to 50% “noninfective” or “low-medium infective” for placebo. After performing all necropsies, CE prevalence in the flock of sheep was 95.7% (88/92) with a total number of 1094 cysts (12.4 cysts/animal). On average, the two-drug-combination groups resulted pulmonary cysts that were 6 mm smaller and hepatic cysts that were 4.2 mm smaller than placebo (p<0.05).

Conclusions/Significance

We demonstrate that Oxfendazole at 60 mg, combination Oxfendazole/Praziquantel and combination Albendazole/Praziquantel are successful schemas that can be added to control measures in animals and merits further study for the treatment of animal CE. Further investigations on different schedules of monotherapy or combined chemotherapy are needed, as well as studies to evaluate the safety and efficacy of Oxfendazole in humans.

Cystic Echinococcosis (CE) is a near-cosmopolitan parasitic zoonosis that causes economic losses in many regions of the world. This parasitic infection can be regarded as an emerging or re-emerging disease causing considerable losses in livestock production. CE is produced by the larval cystic stage (hydatid) of the dog parasite Echinococcus granulosus. After infective eggs are ingested, cysts develop mainly in lungs and liver of humans and animals (sheep, cattle, pigs, horses, etc). Infected people may require surgery and/or Albendazole-based chemotherapy. In this study, we evaluated the effects of Oxfendazole alone (an antiparasitic drug used in animals), Oxfendazole plus Praziquantel, and Albendazole plus Praziquantel against hydatid cysts in sheep over 4 to 6 weeks of treatment. All of the treatments in this study were efficacious in killing the larval stages and, therefore, in minimizing the risk of a dog acquiring new infections (taenias). These treatment schemes can be added to control measures in animals and eventually could be used for the treatment of human infection. Further investigations on different schedules of monotherapy or combined chemotherapy are needed, as well as studies to evaluate the safety and efficacy of Oxfendazole in humans.

[Complicated hydatid cysts of the lung]

BACKGROUND

Hydatid disease which is caused by the parasite Echinococcus granulosis is one of the most important helminthic diseases. The parasitic infection is endemic in many areas worldwide, including the Mediterranean region. The lung is the second most common involved organ. In the present study, we review cases of complicated pulmonary hydatidosis, discussing pathophysiological mechanisms and the clinical, radiological features, as well as natural history and therapeutic options.

METHODS

A retrospective study was conducted in the adult pulmonary department of The Tunis Chest Diseases and Surgery Training Hospital, a tertiary referral hospital for pulmonary diseases in Tunisia.

RESULTS

52 cases (mean age=34.6 years) were evaluated between 1998 and 2008. Rupture of the hydatid cyst occurred into the bronchi in the majority of cases (86.5%) and into the pleura in 9.6%. Extrathoracic involvement was found in 17.3% of the cases. Diagnosis of pulmonary hydatidosis was based on a consistent clinical and radiological presentation. Recourse to CT scan of the chest was helpful for diagnosis in 28% of the patients. Fibre-optic bronchoscopy (performed in 64.5% of cases) confirmed the diagnosis in 4 patients with total endoscopic extraction of hydatid cyst membrane in 2 cases. Surgical treatment was performed in 44 cases; resection of lung parenchyma was necessary in 8 patients (18.2%). Medical treatment was associated in 2 cases. Outcome revealed recurrence of pulmonary hydatidosis in 3 patients, and the death of 1 patient with chronic pulmonary hypertension due to chronic hydatid pulmonary embolism.

CONCLUSION

Complicated pulmonary hydatidosis may present some diagnostic difficulties, even in endemic regions. Management may be difficult, costly, and may require pulmonary resections.

An oral recombinant vaccine in dogs against Echinococcus granulosus, the causative agent of human hydatid disease: a pilot study

Dogs are the main source of human cystic echinococcosis. An oral vaccine would be an important contribution to control programs in endemic countries. We conducted two parallel experimental trials in Morocco and Tunisia of a new oral vaccine candidate against Echinococcus granulosus in 28 dogs. The vaccine was prepared using two recombinant proteins from adult worms, a tropomyosin (EgTrp) and a fibrillar protein similar to paramyosin (EgA31), cloned and expressed in a live attenuated strain of Salmonella enterica serovar typhimurium.

In each country, five dogs were vaccinated with the associated EgA31 and EgTrp; three dogs received only the vector Salmonella; and six dogs were used as different controls. The vaccinated dogs received two oral doses of the vaccine 21 d apart, and were challenged 20 d later with 75,000 living protoscoleces. The controls were challenged under the same conditions. All dogs were sacrificed 26–29 d postchallenge, before the appearance of eggs, for safety reasons.

We studied the histological responses to both the vaccine and control at the level of the duodenum, the natural localization of the cestode. Here we show a significant decrease of parasite burden in vaccinated dogs (70% to 80%) and a slower development rate in all remaining worms. The Salmonella vaccine EgA31-EgTrp demonstrated a high efficacy against E. granulosus promoting its potential role in reducing transmission to humans and animals.

In many countries in the world, livestock and humans are affected with hydatid disease, which is caused by the development, in the viscera, of the larval stage of the cestode Echinococcus granulosus. They become infected by ingesting the eggs of this parasite, which are passed in the feces of the dog—the host of the adult worm. Domestic dogs are key in the transmission to livestock and humans.

This disease remains a major economic and public health problem in affected countries. Because dogs are quickly reinfected, control programs in these locations include monthly anthelmintic deworming. These control measures, however, are burdensome for the owner, so they often fail. In contrast, vaccination can take place in control programs at different stages of the parasite life cycle. For example, currently an effective recombinant vaccine for sheep has been developed that should work indirectly to reduce infection in dogs, which tend to eat sheep offal. However, we propose that a recombinant oral vaccine given to the small number of dogs keeping the herd would decrease the number of Echinococcus granulosus adult worms and, consequently, the number of infective eggs. This measure would help reduce the contamination risk factors for humans and livestock, and would be cost-effective for the owners of the dogs.

A modified coproantigen test used for surveillance of Echinococcus spp. in Tibetan dogs

Recently an immunological test for Echinococcus spp. antigens in dog faeces has been developed. The antigens appear to be carbohydrates, which survive proteolytic digestion and environmental degradation. For ELISA a capture antibody is used to capture the antigens, followed by a detection antibody. This paper describes a modification of the test whereby capture and detection antibodies are generated exclusively to the carbohydrate portion of the parasite tegument. Faecal extracts were heated to 70 degrees C overnight and the addition of foetal calf serum to the extracts was not necessary. The use of this modification as a surveillance tool in an extensive field trial of hydatid control in Western Sichuan is described. From 2003 onwards all dogs received a treatment with praziquantel pills in the spring and the autumn of each year. On each of six occasions 580 faecal samples were collected from 29 villages and analysed. Prevalence of Echinococcus spp. coproantigen-positive samples was 50% in year 2000, and decreased from 35% to 17% through 2003-2005. This coproantigen technique is now being used as part of the Chinese National Hydatid Disease Control Program, initially in 10 counties in Sichuan Province.

Brief historical remarks as an introduction for the international symposium on taeniasis/cysticercosis and echinococcosis

Some historical remarks are made on the background information leading to the international symposium on taeniasis/cysticercosis and echincoccosis with focus on Asia and the Pacific.