Fasciolosis - caused by infection with the tropical liver fluke Fasciola gigantica - is the third most important livestock disease in Indonesia (after only Newcastle disease and haemonchosis), and the most important disease of cattle and buffalo. Infection is characterised by weight loss, anaemia, reduced productivity (including draught output), and reduced reproductive performance. About one-third of Indonesia's 10 million cattle and buffalo are affected, and loss of production has been estimated at around A$100 m annually.

Although fasciolosis is a serious disease in most humid tropical regions of the world, it has been the subject of little research, probably because it is common and unspectacular, and the clinical signs are often regarded as the norm, or attributed to poor nutrition. Fasciola hepatica, the liver fluke of ruminants in temperate climates, has been much better studied. Unfortunately, however, most control strategies for F. hepatica would not work for F. gigantica; the species have major biological and epidemiological differences, and control options are quite different in temperate and developing tropical regions.

Australian and Indonesian collaborators - led by veterinary epidemiologist Associate Prof. D.B. Copeman of the Graduate School of Tropical Veterinary Science at James Cook University - will focus on four control strategies likely to be applicable in the Indonesian context: grazing/fodder management, snail control, chemotherapy and vaccination. In doing so, they will test the following hypotheses:

That knowledge of the length of time metacercariae (the fluke's immature form) survive, and where on a rice stalk they encyst, will provide a practical means of avoiding infection with F. gigantica (With this knowledge, farmers should select the proportion of the stalk that has no metacercariae, or withhold rice stalks from stock until metacercariae die.)

That reduction in the number of intermediate host snails and reduction in their rate of infection with F. gigantica can be achieved by promoting infection of these snails with an intestinal fluke of birds, Echinostoma revolutum
(Recent BALITVET research has shown that snails infected with this fluke are infertile and not susceptible to F. gigantica infection. Village chickens and ducks are often infected with E. revolutum, and, since these birds have access to rice fields after harvest, it is possible that some control of F. gigantica through this means already exists.)

That fasciolosis can be controlled economically using chemotherapy, especially where infection is seasonal and there are distinct wet and dry seasons (eastern Indonesia)
(A number of modern drugs are effective against F. gigantica in cattle and buffalo. However, they are expensive, and the number of doses, timing and likely benefit of treatment must be known before recommendations for their use can be made.)

That vaccination is a cost-effective means of control of fasciolosis (If a vaccine against F. gigantica to be developed in another ACIAR project (9049) is successful under laboratory conditions, it could be evaluated in a field trial integrated with the other studies.)

The team will undertake two experiments in the first year of the project. The first will determine the effect of desiccation, sunshine and temperature on longevity of metacercariae of F. gigantica; and the second will examine longevity of metacercariae that encyst on rice stalks at various stages of their growth. In the first year, the collaborators will also survey about 1000 farmers to map the distribution of infection with F. gigantica in the Bogor district. In the second and third years farmers will be recruited into field trials to assess the effectiveness of methods to control F. gigantica - by denying stock access to viable metacercariae; by using ducks and chickens infected with E. revolutum; by using chemotherapy; and possibly by field testing the vaccine.

Benefits will accrue not only in Indonesia, but throughout the humid tropics. Losses in productivity of cattle and buffalo due to loss of meat, draught and reproductive output, estimated at A$44 for each infected animal, could be saved. The main beneficiaries will be smallholder farmers and rural communities. Science in Indonesia will also benefit. The project offers training opportunities for at least four Indonesian scientists. Other Indonesian scientists, and technical and extension workers, will also benefit from being involved in solving an important constraint to production. As well as extending their research experience, Australian scientists may gain useful insights into improved control of F. hepatica.