Control of fasciolosis in cattle and buffaloes in Indonesia, Philippines and Cambodia

• National Veterinary Diagnostic Laboratory, Cambodia
• Central Mindanao University, Philippines
• University of Southern Mindanao, Philippines
• Research Institute for Veterinary Science, Indonesia

Disease caused by the parasitic fluke Fasciola gigantica is probably the most important constraint to the productivity and health of cattle and buffaloes in many areas of the humid tropics, including most of Southeast Asia.
Infection, termed fasciolosis, is particularly prevalent in areas where rice is grown using irrigation. This is because the rice paddies are ideal homes for a snail which is the intermediate host for the parasite. When cattle and buffalo dung are used as fertiliser in the rice fields, the parasite can then infect the snail (an essential stage in its life cycle). Later, the parasite leaves the snail, lives briefly in the water and contaminates the rice plants; when the rice straw is fed to the cattle this completes the infection cycle.
Infected animals are anaemic and, compared to healthy counterparts, are slow-growing and achieve a lower final weight and size. As well as lowered meat and milk productivity, and less efficient feed conversion, this means reduced working capacity. In countries where 80% of the power for land cultivation is provided by cattle and buffaloes, such a loss is especially significant.
Farmers do little to control the problem; the disease is so common and unspectacular that it is either simply accepted or is just not recognised at all, and the poor condition of infected animals is considered normal.
Before ACIAR project AS1/1991/023, information on the epidemiology of the disease and on control methods was inadequate, and most knowledge was derived from the related species F. hepatica in temperate systems. However that project led to development of the effective control methods that are now available and appropriate for use in Indonesia, where irrigated rice is grown seasonally. The next step, and the reason for this project, was to develop and extend the methods for wider use in Southeast Asia and elsewhere.

The main purpose of the project was to further develop strategies for the control of the tropical liver fluke parasite, originally developed for Indonesia through ACIAR-funded research, and extend the work to large ruminants in the Philippines and Cambodia.

Abattoirs in Cambodia and the Philippines were surveyed to find the prevalence of infection of animals and to record the basic biological statistics about parasite load and host conditions. Scientists compared the incidence of the disease and its effects in different regions and seasons.
The team developed a simulation model for fasciolosis control, using knowledge of the region's agriculture, social customs and infection parameters. The differences in resistance to infection between cattle breeds in Australia, Cambodia and the Philippines were compared.
Control of fasciolosis using anthelmintic compounds was evaluated at field sites, and the project also studied biological control using ducks (through competition for the tropical liver fluke from the poultry fluke Echinostoma revolutum and through consumption of the snail hosts) in the rice fields. A problem arose because the ducks are also commonly infected with a schistosome parasite, which has a free-living stage in the water that burrows into human skin, causing an unpleasant and itchy dermatitis. This is the principal reason why Indonesian village farmers have been reluctant to use ducks for biological control.

The overall output of the project was to demonstrate that the application of a scientifically based fasciolosis control program can alleviate poverty through increased animal production. The initial impact of the research was restricted to the sites where the research took place, but animal owners who participated in the research learnt how to increase the income they derived from animal production.
The scientists developed options for fasciolosis control that required minimal use of anthelmintic medications. The control program is based on the following five elements:
1. Prevent animals grazing in rice fields adjacent to a village or cattle pen for up to a month after harvest, to reduce their risk of ingesting the infective metacercariae;
2. Feed only the top two-thirds of freshly cut rice stalks, cut 20-30 cm above ground level, to avoid feeding the metacercariae;
3. Kill metacercariae on the lower third of the rice stalks by exposing them to sunlight for three days before feeding to cattle;
4. Before using cattle or buffalo dung as fertiliser in rice fields, mix it with duck or chicken manure that has been naturally infected with the poultry fluke (the problem of biological control using ducks, where the ducks were infected with the schistosome, was solved by using village chickens instead);
5. Treat cattle with triclabenzadole about 6 weeks after harvesting the second seasonal rice crop.
These recommendations have been made available to extension services in Indonesia, Cambodia, the Philippines and through representative networks to Vietnam, Thailand and Laos. The extension is being assisted by the availability of pamphlets and other material and the production of a laboratory manual providing technical support for researchers and extension workers.
A fasciolosis control network of researchers is now well established, giving a region-wide perspective to the research effort. For instance, the project supported an international workshop to standardise laboratory procedures for research into fasciolosis.