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Prepared by: MW Lightowlers, The University of Melbourne, 250 Princes Highway,

Werribee, Victoria, 3030, Australia. Facsimile: +61 3 9741 4561; Email:

Hydatid disease is a parasitic infection which causes widespread human

morbidity and mortality. Livestock animals, particularly sheep, are involved

in the parasite’s lifecycle.A defined antigen vaccine has been developed which

can prevent hydatid infection in sheep. The vaccine has been shown to be

highly effective in animal trials, with almost complete immunity persisting for

more than a year after vaccination. Use of the vaccine in livestock may

decrease transmission of the parasite and, indirectly, reduce the incidence of

infections in humans. In some regions animal vaccination or other hydatid

control measures are unlikely to be applicable. In these areas, direct

vaccination of humans against hydatid infection may be a valuable option. It

is likely that the hydatid vaccine would be effective in humans. The vaccine

has the potential to be developed as the world’s first vaccine against a

parasitic infection in humans.This document outlines the progress made to date

with the hydatid vaccine and raises for consideration future actions which

could lead to an evaluation of the vaccine in human clinical trials.

Hydatid disease is a parasitic infection caused by cestodes of the genus

Echinococcus. The most important and widespread of these parasites is E.

granulosus, which causes cystic hydatid disease. The lifecycle involves two

mammalian hosts. Dogs and other canids are infected with the parasite in the

small intestine and eggs are released with faeces. Ingestion of the eggs by a

wide variety of herbivorous animals leads to the growth of hydatid cysts in

tissues. When infected tissues are eaten by a dog, the lifecycle is

completed. Humans become infected by accidental ingestion of microscopic eggs

derived from dog faeces. Hydatid cysts occur most frequently in the liver and

lungs, though they may occur in any site. Cysts may grow to a volume of more

than a litre. Surgery is the standard form of treatment; drugs are of limited

value. Human infections are most common in the Mediterranean region,

sub-Saharan Africa, Russia, China and South America (ref 1-4).

Control programs for hydatid disease have been, or are being, undertaken either

nationally or in regional areas in Argentina, Australia, Brazil, Bulgaria,

Chile, China, Cyprus, Egypt, Greece, Iceland, Italy, Jordan, Kenya, Lebanon,

Morocco, New Zealand, Peru, Portugal, Russia, Spain, Syria, Turkey, Uruguay and

Yugoslavia. These programs rely on public education, restrictions on livestock

slaughtering and control measures in dogs. Despite substantial efforts to

reduce transmission of the parasite, hydatid disease remains a serious cause of

human mortality in many parts of the world.1 Recently, a vaccine has been

developed as a new tool to assist with control of hydatid disease.

The EG95 vaccine has been developed to prevent infection with E. granulosus in

intermediate hosts (refs 5-7). The vaccine contains a protein which occurs in

the parasite egg and early developmental stages. Parasites attempting to

establish an infection in a vaccinated host are killed by the immune responses

induced by the vaccine.

The vaccine protein is obtained from E. granulosus mRNA expressed in bacteria

using recombinant DNA techniques (ref 6). Immunisation with the protein,

termed EG95, has been shown to prevent hydatid infection in sheep (refs 6,7).

The vaccine for sheep consists of a sterile solution of 50g of EG95 protein and

an adjuvant (immunological stimulant Quil A). Two immunizations with the

vaccine induces immunity against infection with E. granulosus eggs. The

mechanism by which the vaccine has its effect is through antibody and

complement mediated lysis of the parasite oncosphere early in the establishment

of a new infection. Protection can be demonstrated either following challenge

infection or by demonstrating lysis of the parasite in vitro in the presence of

specific serum antibodies to the vaccine. The characteristics of the immunity

stimulated by the EG95 vaccine are summarised in Table 1.

The EG95 vaccine can be produced on an industrial scale and it is being

developed further for widespread use in livestock animals. Reduction in the

prevalence of the disease in farm animals would be expected to have an

important impact on the potential for transmission of the parasite by dogs and,

indirectly, reduce the number of new human infections. Use of the vaccine

together with dog control measures and public education may increase the

effectiveness of hydatid control campaigns and reduce the period of time over

which control measures are required. This would have a substantial impact on

the incidence of human hydatid infections.

* Two immunizations stimulates greater than 95% protection against hydatid

infection in sheep.·

* More than 50% of vaccinated animals have no viable hydatid cysts after

challenge infection with E. granulosus.·

* Immunity persists for at least a full year after two immunizations with

the vaccine.·

* Approximately 80% immunity is induced in sheep after a single

injection.·

* Solid immunity is transferred with colostral antibody from a vaccinated

dam to neonatal offspring.

* The vaccine has been shown to be similarly effective in trials

carried out

in Argentina, Australia, China and New Zealand.

* The vaccine has been shown to be effective in other animal hosts of E.

granulosus, including goats and cattle.

Regions of the world in which human hydatid disease has its highest prevalence

are commonly remote, where the people are poor and where animal health

infrastructure is rudimentary or non-existent. In these circumstances,

prevention of new cases of human hydatid disease using existing control

measures, or animal vaccination, is unlikely to be effective in the foreseeable

future.

Human vaccination for prevention of infectious diseases has become universally

recognised and available. Medical infrastructure is in place to support the

existing human vaccination programs, even in the remote regions of the world

where hydatid disease is most prevalent. Should an effective human vaccine

become available for hydatid disease, this may offer some communities their

only prospect for prevention of the disease. A vaccine for humans would also

prevent infections, which result from sylvatic transmission of the parasite.

The EG95 vaccine has its effect by preventing new infections, it does not

remove an infection, which exists prior to vaccination. Children’s behaviour

places them at particular risk of infection with hydatid disease, particularly

after the age at which they are independently mobile. A human vaccine would be

used in children at about the age of 4-6 months, around the time that children

commonly receive immunizations against diphtheria, tetanus and polio.

Ideally, children would receive two immunizations with vaccine, however work in

animals suggests that a substantial degree of immunity can be stimulated by a

single injection. Any requirements for booster injections would need to be

determined during clinical trials of the vaccine. It is possible that exposure

to the parasite in endemic areas would provide a natural boosting of the immune

responses stimulated by early childhood vaccination, minimizing the need to

provide booster injections.

While vaccination of humans against important infectious diseases caused by

viruses and bacteria has been very successful, there have been no human

vaccines to prevent any of the important parasitic infections. Despite

intensive effort, attempts to develop vaccines against diseases such as malaria

or schistosomiasis have had limited success experimentally and have not led to

practical vaccines. In contrast, the hydatid vaccine has been shown to be

extremely effective in several natural animal host species. The parasite which

causes hydatid disease in man is the same one which infects animals and the

biology of the infections in man and animals is very similar. For these

reasons, it is very likely that the EG95 vaccine would be effective against

hydatid disease in humans. Successful development of the vaccine may lead to

the first human vaccine against a parasitic disease.

1. Consideration needs to be given to the concept of a human vaccine for

hydatid disease by international experts in echinococcosis and human health and

those involved in the epidemiology and control of hydatid disease. Support for

the concept would need to be expressed by regional, national and international

bodies concerned with human health.

2. Identify a source of funding for preparation of vaccine under Good

Manufacturing Practice guidelines for use in initial human clinical trials

(estimated to be US$ 300,000).

3. Identify an industry partner for development of the vaccine, either

under contract or as a collaborative commercial development.

4. Establish a suitably experienced and qualified Clinical Trial

Management group to carry out the trials.

5. Initiate Phase 1 Clinical Trials in volunteers, assessing safety and

immunogenicity in adults using existing vaccine adjuvants licensed for use in

humans. Protective responses to be determined in vitro using the oncosphere

killing assay.

6 Evaluation of initial trial data and decision to proceed or not proceed.

7. Identify a source of funding for further vaccine development.

8. Safety and immunogenicity trials in children.

9. Identify potentially suitable regions for undertaking trials in

children in endemic areas. Establish baseline data concerning the prevalence and

incidence of hydatid disease.

10. Conduct Clinical Trials in children in endemic areas with immunological

and radiological assessments.

11. Assessment of the Clinical Trial outcomes.

Initial Phase 1 trials could be completed within 1-2 years of identifying a

source of financial support. Further safety and immunogenicity trials would be

likely to take another year. Clinical Trials in endemic areas would be

expected to require 5 or more years due to the slow growth of hydatid cysts. A

successful vaccine development program would see the vaccine being available

around 2010. The immunogenicity of the vaccine, duration of immunity and number of

immunizations required are some of the issues, which may have an important

bearing on the practical usefulness of vaccination in humans. Generic

technologies for improving vaccination strategies, including DNA and edible

vaccines, are the subjects of intense research. During the time that the

initial safety and immunogenicity trials were being undertaken with the EG95

vaccine, providing the "proof of principal" for induction of protective immune

responses against E. granulosus in humans, new developments in vaccine science

may provide alternative, effective methods for vaccine delivery.

1. Schantz PM, Chai J, Craig PS, Eckert J, Jenkins DJ, Macpherson CNL &

Thakur A. 1995. Epidemiology and control of hydatid disease. In Echinococcus

and Hydatid Disease, RCA Thompson & AJ Lymbery eds, pp 233-331; CAB

International, Wallingford

2. Gemmell MA, Lawson JR & Roberts MG 1987. Towards global control of

cystic and alveolar hydatid diseases. Parasitol Today. 3:144151.

3. Eckert,J, Gemmell MA, & Soulsby EJL 1981. FAO/UNEP/WHO Guidelines for

the surveillance, prevention and control of echinococcosis/hydatidosis, World

Health Organization, Geneva

4. Matossian RM, Rickard MD & Smyth JD 1977. Hydatidosis: a global problem

of increasing importance. Bull WH O. 55:499-507.

5. Heath DD & Lawrence SB 1996. Antigenic polypeptides of Echinococcus

granulosus oncospheres and definition of protective molecules. Parasite

Immunol 18: 347-357.

6. Lightowlers MW, Lawrence SB, Gauci CG, Young J, Ralston MJ, Maas D &

Heath DD. 1996. Vaccination against hydatidosis using a defined recombinant

antigen. Parasite Immunol 18:457-462.

7. Lightowlers MW, Jensen O, Fernandez E, Iriarte JA, Woollard, DJ,

GauciCG, Jenkins DJ & Heath DD. 1999. Vaccination trials in Australia and Argentina

confirm the effectiveness of the EG95 hydatid vaccine in sheep. Int J Parasitol 29: 531-534.

Immunodiagnosis of cystic echinococcosis (CE) is useful not only for the primary diagnosis but also for the follow up of patients after surgical or pharmacological treatment, or both. Immunodiagnostic techniques include initial screening tests, to identify crude antigens, such as latex agglutination, double diffusion, indirect hemoagglutination, and enzyme-linked immunosorbent assay, followed by confirmatory tests to identify specific antigens, for example arc-5 immunoelectrophoresis and immunoblotting. The choice of serodiagnostic technique depends primarily on its sensitivity and specificity. Despite the development of sensitive techniques, such as immunoblotting, the immunodiagnosis of CE remains a complex task. The first problem is that most conventional tests give a high percentage of false negative results (up to 25%). Other problems include the presence of false positive patients and the lack of standardisation responsible for the discrepant results reported by the various laboratories.

During the last WHO-IWGE meeting in Bariloche Alberto Nieto, Phil Craig and I proposed the organisation of a new Network to standardise techniques and antigen preparations, to characterise new antigens, to produce recombinant antigens.

I invite all the colleagues interested in this proposal to contact me as soon as possible.

1.Authors of the information sheet

Indicate the name, surname, address and telephone number of the author of this sheet.

2. Planning author (s)

Write the name(s) of the Company, office, Service, Association, School, etc. that have had responsibility for the intervention and that anyway have the documentation needed to provide further information requested. Write the full address and telephone number including dialling code and E-mail address.

3. Intervention/campaign title

Write the title for the intervention/campaign; if a title has not been defined write the name under which the initiative has been most often referred to; if no title can be assigned write "not defined".

4. Intervention/campaign period

Write the month and year of the start and end of the intervention/campaign.

5. Geographical area of intervention/campaign

Write the name(s) of the geographical area(s) in which the intervention/campaign was carried out. In the case of a village write its name, the town and its province.

Wherever the geographical area cannot be suitably defined as above, write the name of the territorial area that allows it to be identifiable.

Include a map if necessary.

7.Social area of intervention/campaign

• Cross (more than one choice if necessary).
• Briefly specify the type or the characteristics of the social area in which the intervention has been carried out (e. g. state middle school, farm, advisory bureau, suburban area, old town centre, …).

8. Target groups

• Cross (more than one choice if necessary).
• Specify the group(s) of people targeted in the intervention.

9. Purpose of intervention

Describe the needs, problems and people that have motivated and determined the type of intervention (e. g. indications of the Regional or Local Health Plan, national or regional factors, direct request, problems highlighted by data of Health Services, statistical information, epidemiological data, …).

Indicate any preliminary studies under taken and research instruments used.

10. Objectives

Indicate the Health objectives (e. g. the reduction of incidence of disease both in animals and humans, the reduction of the mortality rate).

Indicate the objectives which are strictly educational in relation to the period of achievement (short, medium or long term) and in relation to their areas: 1) knowledge, 2) attitudes, 3) behaviour (for example: the acquisition of information on the pathology, to change incorrect habits (feed dogs with infested lungs and livers), to encourage the habit of incinerating infested lungs and livers or periodically dose dogs.

Indicate any other objectives (e. g. Health Services: increase the use of public or private slaughterhouses, develop relationships for collaborating with scholastic institutions; e. g. for education: better the communication capacity of workers in the Veterinary Service).

11. Contents

Briefly describe the stages of the project.

12. Methods and instruments used

• Cross (more than one choice if necessary).
• Specify methods and instruments in relation to the context of their use (e. g. a debate with breeders during which slides were shown, group work headed by teachers…)

13. Costs

Detail the intervention costs even if was not part of a control campaign.

14. Financial funding

Indicate, when possible, the sources of financial funding.

15. Who has carried out the project?

Write the name(s) of the Company, Office, Service, Association, School, etc. that have carried out the project.

17. Parameters used for the control of the results obtained from the intervention

Describe criteria, methods and instruments for the evaluation of the intervention. It is recommended that the required elements be referred to the evaluation of the process (e. g. level of resources used, degree of community participation) and of the end product (how for the objectives were reached).

18. Intervention procedure

Briefly describe the stages carried out in the intervention in the order and integration.

19. Organisation aspects

Indicate any deliberation, total costs, personnel involved (number and professional qualification), Health Services or structures involved.

Diagnostic criteria for case definition and classification in Alveolar Echinococcosis (AE).^*