Health education and formation: essential tools into the echinococcosis/hydatidosis prevention programs

Health Education represents essential elements in the control and eradication campaigns of Echinococcosis/Hydatidosis. The basic elements and the applicatory principles and methodologies are examined. Moreover, the most appropriate intervention methodologies are defined through reference target. There is also a description of the experiences and the methodologies adopted in different Countries of the Mediterranean basin, where the disease is endemic.

Cystic echinococcosis in Sardinia: the current role of sheep

Cystic echinococcosis is one of the most widespread parasitosis in the Mediterranean region. Unfortunately this is also true for Sardinia for various reasons, among which is the close relationship between sheep and dogs in the farms. This work first epidemiologically analyses hydatidosis in sheep in Sardinia and then examines the most important causes of the persistence of these metacestodosis in sheep. The work looks at the factors which are responsible for the enormous quantity of illegal slaughtering and the widespread habit of abandoning the sheep carcasses in the grazing areas, as well as possible initiatives which may eliminate these practices. Such initiatives must include reducing the financial costs and bureaucracy involved when sheep are slaughtered in abattoirs, and also increasing the value of sheep meat. In conclusion new checks and controls are hoped for at a political level which will increase the financial support for the farmers and encourage the use of recombinant vaccines which have already been tested in Sardinia. These are extremely useful for effectively curbing cystic echinococcosis.

Veterinary public health activities at FAO: echinococcosis/hydatid disease

Cystic hydatidosis is a zoonotic disease that remain as a significant cause of human morbidity and mortality in many parts of the world. The disease has veterinary public health implications. FAO is involved with some activities in the control of echinococcosis/hydatid disease: within the Animal Production and Health Division the Veterinary Public Health (VHP) Programme is constituted by members of the different Services (Animal Health, Animal Production, and Livestock Policy) within the Division. FAO regular programme has also established a global network of professionals directly involved in VPH. Furthermore FAO's Technical Cooperation Projects (TCP) is a tool to assist member countries in responding to urgent and unforeseen demands.

Short report: the use of a polymerase chain reaction to detect Echinococcus granulosus (G1 strain) eggs in soil samples

Cystic echinococcosis is a re-emerging disease in central Asia. A total of 120 soil samples taken from 30 gardens of rural homesteads in southern Kazakhstan were analyzed for the presence of taeniid eggs using a concentration technique. Of these, 21 (17.5%) were shown to be contaminated with taeniid eggs. These isolated taeniid eggs were further analyzed using a polymerase chain reaction specific for the G1 (sheep) strain of the tapeworm Echinococcus granulosus, and five samples were shown to be positive. This study demonstrates the widespread contamination of the environment with E. granulosus eggs in an Echinococcus-endemic area and thus the potential for indirect transmission of E. granulosus to humans from such sources.

Wilderness in the city: the urbanization of Echinococcus multilocularis

A distinct increase in fox populations, particularly in urban areas, has been observed in Europe. This is of particular concern in endemic regions of the small fox tapeworm Echinococcus multilocularis, the aetiological agent of human alveolar echinococcosis. Novel tools have facilitated the investigation of the ecology of urban foxes and have demonstrated the urban wildlife cycle of E. multilocularis. Such studies are essential for estimating the risk of transmission to humans and to determine the basics for the development of control strategies.

Echinococcus granulosus: oncosphere-specific transcription of genes encoding a host-protective antigen

A recombinant antigen vaccine has been developed which is effective in preventing the hydatid parasite, Echinococcus granulosus from infecting its animal intermediate hosts. The vaccine antigen, designated EG95, is expressed by a cDNA cloned from E. granulosus oncosphere mRNA. The gene encoding EG95 belongs to a small gene family where six of the members are transcribed in the oncosphere. Conditions were established which allowed specific RT-PCR amplification of mRNA for each gene family member and these conditions were applied to determine transcription patterns for each gene family member in gravid adult worms, oncospheres, and protoscoleces. The four eg95 gene family members which encode an identical EG95 protein, were transcribed only in the oncosphere. In contrast, two gene family members that encode variant EG95 proteins did not have transcription patterns confined to the oncosphere. These findings suggest a common biological role for four genes in the gene family and a separate role for the other, more variant gene family members.

The clinical and epidemiological features of hydatid disease in Northern Jordan

OBJECTIVE

To elaborate on the epidemiology of hydatid disease in Jordan as a model for the Middle East, and highlight the obstacles that face disease control in the region.

METHODS

The clinical and epidemiological data for 65 patients with the diagnosis of hydatid cyst (who were treated in the Department of Surgery, Jordan University of Science and Technology, Irbid and its affiliated hospitals, between January 1994 through to September 2003) were analyzed. Fifty-five patients were interviewed for details of life style.

RESULTS

Forty-six percent of patients were below 40- years of age. Fifty-seven percent were females. All interviewed patients gave history of contact with dogs and history of ingestion of raw vegetable food. The latter in addition to a high zoonotic infection rate and uncontrolled animal movement were factors contributing to the high prevalence.

CONCLUSION

Optimization of control programs in the Middle East requires the establishment of a regional center. Wide traveling has made it essential for physicians practicing in non-endemic areas to be aware of the diverse presentations of this disease when dealing with immigrants from endemic areas.

[Cystic echinococcosis in humans: our clinic experience]

Echinococcosis in humans is a zoonotic infection caused by larval stages of cestode species of the Echinococcus genus. In cystic echinococcosis (CE), caused by Echinococcus granulosus, the liver is the first and the more frequent involved organ, followed by the lung. Heart, spleen, kidney and brain are usually less involved. The finding of a cyst in course of echinococcosis is usually fortuitous, during ultrasound examination, X-ray or CT. The Authors report 4 cases of human CE admitted to the Department of Infectious Diseases University of Naples "Federico II". Each case is peculiar both for the organ involved by the cysts and for the symptomatolgy. The abdominal pain, in case 1 caused by gallstones, allowed, by the ultrasound examination, to find several hydatid cysts in the liver, never symptomatic until then. The woman, in case 2, was operated for cysts in the lung, without receiving pharmacological prophylaxis. The same occurred in case 4, in which the lack of prophylaxis caused very serious relapses. In case 3, the young woman underwent an ultrasound examination because of an abdominal pain. A unique large cyst extended only in the spleen. The specific serology for immunoglobulin anti-E. granulosus resulted positive 1:61 (n.v. < 50). The Albendazole therapy caused the disappareance of pain, quickly. Later, the patient was splenectomized. It's not clear why only the spleen was involved and why the anti-E. granulosus serum levels of were increased only a little. The man, in case 4, was admitted with chest pain and electrocardiographic findings of myocardial anterior ischemia. He underwent surgical treatment of three hepatic cysts by E. granulosus, during the previous year. Two-dimensional echocardiography, transesophageal echocardiography, and cardiac magnetic resonance revealed a round cystic mass, 6 x 6 mm, located in the middle interventricular septum. The cardiac isoenzymes were in the normal ranges, but the anti-E. granulosus immunoglobulins were positive 1:5120 (n.v. < 64). The patient was treated with Albendazole. This caused the almost simultaneous disappearance of the circular cystic and clinical and electrocardiographic findings of myocardial ischemia. A cardiac hydatid cyst is an uncommon lesion, occurring in about 0.4-2% of patients with echinococcosis. In conclusion, Cystic echinococcosis is a problem in Mediterranean regions because of the high population of stray dogs, favourable conditions created by man and, above all, the illegal slaughtering.

[Animal echinococcosis in Italy: epidemiological update]

Cystic Echinococcosis (CE) is one of the most widespread parasitoses in the Mediterranean Region (MR). This is due to various factors, the most important being the close association between man, sheep and dogs in areas where open farming is practised. Although this disease has been known for several years and many studies have been carried out, nowadays in Italy there are no complete epidemiological data on its diffusion and distribution. The available data show that CE is mainly diffused in those districts where the sheep-dog cycle can be perpetuated, such as central and southern Italy, and the islands. Furthermore, no data are available on biomolecular characterisation of the strains of Echinococcus granulosus in Italy, apart form those in Sardinia, where the G1 (sheep-dog) and G7 (pig-dog) strains were recently isolated. One of the reasons why CE is a problem with no easy solution is undoubtedly the difficulty of making a certain diagnosis in the dog, the principal definitive host of E. granulosus.

Echinococcus granulosus strain typing in North Africa: comparison of eight nuclear and mitochondrial DNA fragments

Recent studies of Echinococcus granulosus molecular strain typing have enabled a better understanding of the transmission cycle of cystic echinococcosis. There have been many publications in this area but there is a need for the evaluation of these tools. We have attempted to respond to this need in our study, which assessed 8 DNA fragments of 40 E. granulosus cysts from North Africa. Parasitological material was collected from 5 types of intermediate hosts, in 5 different countries. The primers chosen to amplify DNA targets were defined either in nuclear DNA, or in mitochondrial DNA. After amplification, PCR products were sequenced. The sequences obtained were aligned and comparisons were made within the group and with GenBank sequences. Whether the target was nuclear or mitochondrial, the same 2 main groups of genotypes were found. The first one, the 'sheep' strain, was found in the human, sheep and cattle samples collected in North Africa. The second one, the 'camel' strain, was found in the camel cysts and cattle and human cysts from Mauritania. These findings further confirm the congruence of the data given by the nuclear and the mitochondrial genome.

Transmission dynamics and control options for Echinococcus granulosus

Cystic echinococcosis, caused by the larval stage of Echinococcus granulosus, is a global public health problem. Whilst in a few localities, such as New Zealand, the parasite has been effectively controlled or even eradicated, in most endemic regions it remains a persistent problem. In some areas, such as the former Soviet Union, the disease incidence in humans has increased rapidly in recent years. It is important to have an understanding of the transmission dynamics, both between dogs and domestic livestock where the parasite maintains itself and from dogs to people. It is from this knowledge that effective control measures can be devised to reduce the prevalence of the parasite in animals and hence reduce the incidence of human disease. Mathematical models to describe the transmission of the parasite and the effects of different control strategies were first proposed over twenty years ago. Since then further information has been acquired, new technology has been developed and better computing technology has become available. In this review, we summarise these developments and put together a theoretical framework on the interpretation of surveillance information, how this affects transmission and how this information can be exploited to develop new intervention strategies for the control of the parasite. In particular, the parasite remains a persistent or re-emerging problem in countries of low economic output where resources for an intensive control programme, that has been successful in rich countries, are not available. By understanding of the transmission biology, including mathematical modelling, alternative and cost-effective means of control can be developed.

Transmission ecology of Echinococcus in wild-life in Australia and Africa

Following the introduction of E. granulosus into Australia with domestic animals during European settlement, the parasite quickly became established in the E. granulosus-naive native animals of the continent. The distribution of E. granulosus in wildlife in Australia is restricted by rainfall, but nevertheless the parasite is currently widespread and highly prevalent in many areas including numerous national parks and privately owned farms. The human population of Africa is rapidly increasing resulting in ever more pressure on wild-life populations and habitat. National parks, reserves and conservation areas now provide important tracts of preserved habitat for maintaining populations of wildlife that are also important in the maintenance of E. granulosus. In some parts of Africa, hydatid-infected humans provide a source of E. granulosus infection to wildlife definitive hosts. In many areas felids may also act as important definitive hosts for E. granulosus with the parasite being maintained in a prey/predator relationship between lions and a range of intermediate hosts. Populations of E. granulosus-infected wild-life both in Australia and Africa act as important reservoirs in perpetuating the transmission of E. granulosus to both domestic animals and humans. In Australia, E. granulosus-infected wild-life is infiltrating urban areas and currently represents a potentially important new public health problem.

Fenced pasture: a possible risk factor for human alveolar echinococcosis in Tibetan pastoralist communities of Sichuan, China

Alveolar echinococcosis, infection caused by the parasitic helminth Echinococcus multilocularis, is a zoonosis strongly linked to climatic and ecological factors. Cross-sectional survey data were used to test a hypothesis that partial fencing of pastures could promote alveolar echinococcosis transmission in semi-nomadic pastoral communities of the Tibetan plateau, PR China. Using multiple stepwise logistic regression with consideration of factors of age and gender, it was shown that partial fencing around the settlements in winter pasture was significantly and independently associated with the risk of human alveolar echinococcosis in the surveyed villages (P = 0.021). The underlying reason may lie in overgrazing, an assumed cause of population outbreaks of small mammal intermediate hosts of the parasite on the Tibetan plateau. Overgrazing may have been exacerbated by the reduction of communal pastures nearby the settlements due to introduction of partial fencing around group tenure pastures acquired by Tibetan pastoralist families.

Molecular characterization of Egyptian human and anima Echinococcus granulosus isolates by RAPD-PCR technique

Five primers of known, but arbitrary nucleotide sequence (OPH-03, OPH-05, OPH-12, OPH-15, OPH-18) were used to detect genetic variability in Egyptian human, camel and pig E. granulosus isolates. OPH-03, OPH-05 & OPH-15 proved useful as genetic markers of strain variation, while OPH-12 and OPH-18 allowed distinction at the genus level i.e. diversified from Cysticercus tenuicollis. OPH-03 was the most effective giving sharp distinct banding pattern and the least values of similarity coefficients. Some variations were detected within E. granulosus isolates from the same host. The level of heterogeneity was low in three of the human isolates, camel and pig strains. Individual variation was detectable within other 3 human isolates. Human and camel isolates were the most related pair, having similar patterns and the highest similarity coefficients. The study implies that human cases in Egypt are of the camel/dog strain, and camels are important hosts for the transmission of human hydatidosis.

Cystic echinococcosis in the Arctic and Sub-Arctic

The northern biotype ofEchinococcus granulosusoccurs throughout the holarctic zones of tundra and taiga, from eastern Fennoscandia to the Bering Strait in Eurasia and in North America from arctic Alaska approximately to the northern border of the United States. The cycle of the cestode is complex in taiga at lower latitudes, because of the greater diversity of potential hosts. In the Arctic and Subarctic, however, four patterns of predator/prey relationships may be discerned. Two natural cycles involve the wolf and wild reindeer and the wolf and elk (moose), respectively. Where deer of the two species coexist, both are prey of the wolf; the interactions of the wolf and elk are here described on the basis of long-term observations made on Isle Royale (in Lake Superior near the southern limit of taiga), where only the wolf and elk serve as hosts forE. granulosus. A synanthropic cycle involving herding-dogs and domesticated reindeer caused hyperendemicity of cystic echinococcosis in arctic Eurasia, mainly in northeastern Siberia. The 4th pattern, a semi-synanthropic cycle, formerly existed in Alaska, wherein sled-dogs of the indigenous hunters became infected by consuming the lungs of wild reindeer. The sequence of changes in life-style inherent in the process of acculturation affected the occurrence of cystic echinococcosis among nomadic Iñupiat in arctic Alaska. When those people became sedentary, the environs of their early villages soon became severely contaminated by faeces of dogs, and cases of cystic echinococcosis occurred. Compared to cystic echinococcosis caused byE. granulosusadapted to synanthropic hosts (dog and domestic ungulates), the infection produced by the northern biotype is relatively benign. Nearly all diagnosed cases of cystic echinococcosis (>300) in Alaska have occurred in indigenous people; only one fatality has been recorded (in a non-indigenous person). After sled-dogs were replaced by machines, cases have become rare in Alaska. A similar effect has been observed in Fennoscandia, in the Saami and domesticated reindeer. Recent records indicate that the prevalence of cystic echinococcosis is increasing in Russia, suggesting that dogs are used there in herding.

Molecular tools for studies on the transmission biology ofEchinococcus multilocularis

Two novel approaches for diagnosis of intestinalEchinococcus multilocularisinfection, the detection ofE. multilocularis-specific coproantigens in ELISA and of copro-DNA by PCR, have been successfully implemented. These methods have proven their value for thepost mortemand theintra vitamdiagnosis ofE. multilocularisin definitive hosts. They have also made novel approaches possible to study the transmission biology of the parasite as they allow detection of the infection in faecal samples collected in the environment. Coproantigen detection is the diagnostic method of choice as it is sensitive, fast and cheap. Studies on faecal samples collected in the field revealed that coproantigen detection did reflect the different prevalences in fox populations as assessed from foxes at necropsy and also the effect of deworming efforts in foxes as achieved by long-term distribution of praziquantel-containing baits. The use of PCR for routine diagnostic or large-scale purposes is hampered by the fact that DNA extraction from faecal material is a very laborious task. Therefore, PCR is rationally used for confirmatory purposes of copro-antigen-positive samples. As taeniid eggs cannot further be differentiated morphologically, PCR is the method of choice to identifyE. multilocularisinfections in faecal or environmental samples containing taeniid eggs. In intermediate rodent hosts, PCR is routinely used in epidemiological studies for identifyingE. multilocularisfrom liver lesions which are often very small, atypical or calcified.

The Tibetan hare Lepus oiostolus : a novel intermediate host for Echinococcus multilocularis

Multicystic hydatids have been found in the livers of hares ( Lepus oiostolus) examined from the Qinghai-Tibet plateau of China. In this study, the causative species was definitively identified as Echinococcus multilocularis by mitochondrial DNA sequencing. This is the first confirmation of larval E. multilocularis from hares. The hydatids contained protoscolices, suggesting that the hare may contribute to the transmission of E. multilocularis on the Tibetan plateau.

A model for the transmission of Echinococcus multilocularis in Hokkaido, Japan

A mathematical model for Echinococcus multilocularis transmission would be useful for estimating its prevalence and determining control strategies. We propose a mathematical model which quantitatively describes the transmission of E. multilocularis in Hokkaido, Japan. The model takes into account the influence of the dynamics of both the definitive and the intermediate host populations, which show large scale seasonal variation as they are wild animals. The simulations based on the model clarify the mechanism of seasonal transmission of E. multilocularis quantitatively, notwithstanding a lack of seasonal prevalence data. At present, human alveolar echinococcosis is prevalent throughout the mainland of Hokkaido. The risk of being infected in the human population has been investigated by analyzing the seasonal fluctuation in parasite egg dispersion in the environment. This is necessary for the planning of more suitable preventive measures against E. multilocularis.

[Clandestine slaughtering in Tunisia: investigation on the knowledge and practices of butchers concerning hydatidosis]

Echinococcosis is one of the major parasitic diseases in Tunisia, accounting for a considerable public health problem. We propose in this work to analyse the behaviour of butchers and to evaluate its impact on the hydatic cyst transmission.

MATERIAL AND METHODS

We carried out a national transversal descriptive survey that included 97 butcher shops using illegal practice, located in 18 regions (governorats) of Tunisia. The sampling procedure was implemented according to the level of disease endemicity.

RESULTS

60.8% of butcher shops were located along main roads and therefore supplying travellers. Among the animals slaughtered sheep come in first position (97.9%). More than 80% of the butchers kept aside a place around the butcher shop to sacrifice their animals. We noted the presence of dogs near butcher shop in 52.6% of cases and stray dogs in 43.3% of cases. Only 13.4% of the butchers knew the disease mode of transmission. Parasitized viscera were thrown into dustbins or further in the riverbed in 56.7%. More than 50% of butchers, having an inadequate behaviour in front of parasitized viscera or ignoring the disease cycle, were originating from an hyper or holoendemic area.

CONCLUSION

Illegal slaughtering practices have an important impact on transmission of cystic echinococcosis in Tunisia.

Investigation of risk factors for development of human hydatidosis among households raising livestock in Tibetan areas of western Sichuan province

OBJECTIVE

To identify factors influencing the development of hydatidosis in Tibetan areas of western Sichuan.

METHODS

A questionnaire investigation was carried out to collect data on factors related to hydatidosis among households raising livestock.

RESULTS

Analyses of data revealed that dogs rather than foxes were the most important source of AE transmission. People below 19 years old tended to suffering from CE rather than AE and people 19-38 years old, especially the females, were under an increasing risk of suffering from AE (female vs. male, OR = 2.438, CI = 1.317-4.514, P < 0.05). Increased risks of both AE and CE prevalence associated with nomadic life, aging, playing with dogs, not protecting food from flies, and raising yaks or sheep.

CONCLUSION

In addition to age, sex, environmental conditions and hygienic behaviors, raising yaks or sheep and playing with dogs also increase the risk of suffering from hydatidosis as well in this area.

Immunodiagnostic and molecular approaches for the detection of taeniid cestode infections

This article summarizes the most recent advances in techniques and applications for the detection of taeniid cestode-infected persons or animals. In addition, the use of molecular approaches for strain identification and control of parasite transmission is discussed.

Epidemiology of echinococcosis

BACKGROUND

Various species and infraspecific forms of the cestode genus Echinococcus are causative agents of human echinococcosis. Pathology, epidemiology and geographical occurrence vary widely between the different Echinococcus taxa. As a general rule, those forms of echinococcosis that are transmitted mainly by wild animals are rather rare, due to limited contact between humans and wildlife. This is the case with alveolar echinococcosis (AE) caused by Echinococcus multilocularis, the 'fox tapeworm' (except in regions where domestic dogs are heavily involved in the lifecycle), and for the South American endemic species E. oligarthrus and E. vogeli. On the other hand, most forms of cystic echinococcosis (CE) are transmitted in domestic lifecycles involving dogs and livestock and constitute an emerging public health problem, especially in regions with extensive livestock husbandry and non-supervised slaughter.

METHOD

This review focuses on two fields where a wealth of new information became available in recent years.

RESULTS AND CONCLUSIONS

New data demonstrate that ' E. granulosus', the causative agent of CE, is an assembly of several, rather diverse, species and genotypes that show fundamental differences, not only in their epidemiology, but also in their pathogenicity to humans. This fact may explain the unequal distribution of high-endemicity areas for human CE on regional scales, which previously, has been attributed to differences in human behaviour. In addition, new data suggest that E. multilocularis is expanding its geographical range in the northern hemisphere, and its transmission is intensifying, e.g. in central Europe. Moreover, the lifecycle (involving wild foxes and rodents) is rapidly becoming 'urbanised' due to the recent establishment of fox populations in cities and towns. This shift from sylvatic to synanthropic occurrence is likely to result in an increased pressure on the human population of infection from AE.

The origin and dispersion of human parasitic diseases in the old world (Africa, Europe and Madagascar)

The ancestors of present-day man (Homo sapiens sapiens) appeared in East Africa some three and a half million years ago (Australopithecs), and then migrated to Europe, Asia, and later to the Americas, thus beginning the differentiation process. The passage from nomadic to sedentary life took place in the Middle East in around 8000 BC. Wars, spontaneous migrations and forced migrations (slave trade) led to enormous mixtures of populations in Europe and Africa and favoured the spread of numerous parasitic diseases with specific strains according to geographic area. The three human plasmodia (Plasmodium falciparum, P. vivax, and P. malariae) were imported from Africa into the Mediterranean region with the first human migrations, but it was the Neolithic revolution (sedentarisation, irrigation, population increase) which brought about actual foci for malaria. The reservoir for Leishmania infantum and L. donovani--the dog--has been domesticated for thousands of years. Wild rodents as reservoirs of L. major have also long been in contact with man and probably were imported from tropical Africa across the Sahara. L. tropica, by contrast, followed the migrations of man, its only reservoir. L. infantum and L. donovani spread with man and his dogs from West Africa. Likewise, for thousands of years, the dog has played an important role in the spread and the endemic character of hydatidosis through sheep (in Europe and North Africa) and dromadary (in the Sahara and North Africa). Schistosoma haematobium and S. mansoni have existed since prehistoric times in populations living in or passing through the Sahara. These populations then transported them to countries of Northern Africa where the specific, intermediary hosts were already present. Madagascar was inhabited by populations of Indonesian origin who imported lymphatic filariosis across the Indian Ocean (possibly of African origin since the Indonesian sailors had spent time on the African coast before reaching Madagascar). Migrants coming from Africa and Arabia brought with them the two African forms of bilharziosis: S. haematobium and S. mansoni.