Discipline: health & welfare;
Project title: Impact of Fasciola hepatica on dairy production and sustainable management on selected farms in South Africa
Principal researcher: Dr J.A. van Wyk, University of Pretoria.
Aim: To Investigate the potential threat of the liver fluke parasite (Fasciola sp.) to losses in production of dairy cows, in order to develop effective, sustainable methods of control.
Locality: Four farms in the Tsitsikamma region, of which three were judged by local farmers to be seriously affected by Fasciola, and the fourth with practically no problem.
Background to investigation: The eggs of Fasciola worms harboured in the livers of cattle, are passed in the faeces of the host, hatch in water and, for completion of the life cycle of the parasite, penetrate into the intermediate hosts, comprising Limnaea mud snails. The problem is that very few of the anti-Fasciola drugs may be used in lactating cows producing milk destined for human consumption. Additionally, there is a grave danger of development of resistant liver fluke worms if these drugs are over-used.
Project execution: Monthly on-farm evaluation of worm transmission is done by the researchers through snail recovery from muddy spots on the four farms. Secondly, blood serum is collected for analysis for enzymes resulting from liver cell damage by migrating Fasciola. Thirdly, worm eggs are counted on faecal samples from the trial cattle and fourthly, percentages of live and dead snails (empty shells) are determined, together with the proportions of mature and immature snails to study the fluctuation of levels of infection of snails with trematode parasites and to follow their seasonal cycling on pasture.
Preliminary results: 1) Whereas large numbers of the snails were recovered and some seasonal cycling illustrated for the three farms with problems with the parasite, there were none on the fourth farm, thus confirming, together with the absence of Fasciola eggs in the faeces of the cows, that this farm is free from the parasite. 2) Thus far relatively low numbers of eggs were obtained in the approximately 4500 worm egg counts done on faeces from the tested 160 heifers and lactating cows. 3) Uncommonly high levels of infestation of muddy patches with snail hosts have been found. 4) The snail hosts re-entered the muddy patches (their habitat) relatively quickly after extensive earthworks to drain the muddy patches. 5) Periodical fluctuation in levels of infection of snails with trematode parasites has been noticed.
Some envisaged management approaches in further phases of the project: Fasciola management is being targeted in the project, for example: (i) use of temporary, electrified fencing for separating the animals from snail-infested mud spots on pasture; (ii) rapid methods of evaluation of farms for the potential for sustaining Fasciola development; and (iii) training of farm workers in snail recovery as an early warning system for exposure to high levels of Fasciola sp.