130 LIFE-lIISlOP.y OF AFEICAX LIVER FLUKE. 



where it is almost as common as F. hepaiica, and mixed 

 infections of the two flukes occur. Specimens have also been 

 obtained by me from Xatal, from the Eastern ProA-ince and the 

 Western Province of the Union of Sonth Africa, and from cattle 

 sent from Rhodesia. 



With regard to preventiye measures, the following pre- 

 cautions are sug-o-ested : Where Limnnea nafalenais occurs, 

 vegetation should be reduced to a minimum at the edges of 

 the ponds and streams, and reeds and bulrushes should be cut 

 back. These plants are favourite jilaces for breeding and the 

 food for choice for the snails, and their absence is therefore a 

 deterrent to the spread of fluke. The Limnaea also feed 

 greedily on the leaves of the blue water lily, on the underside 

 of whose leaves they lay their egg- masses. 



Cattle and sheep should be kept from damp, marshy soil, 

 where Limnaea is present in the water. I have found infected 

 snails twenty feet from the edge of the water in marshy spots 

 in Xatal. AVatering of stock with water that has been stored 

 for two days is almost sure to be safe. The cercariae of Fasciola 

 (jijjantica rarely suivive more than thirty-six hours in water, 

 and unless there are facilities, such as grass or debris on which 

 they can encyst, they either i)erish or else they encyst on the 

 sides of the storage tank, just above the level of tlie water. The 

 cysts are not easily washed off when water is drawn, but can 

 be scoured or scraped oft^ and buraed when the tank is empty. 

 The latter precaution of burning is necessary, as the c^^sts 

 remain alive for considerable periods. 



Some recent experiences and observations in the open have 

 shown me that ducks are very efficient in destroying pond 

 snails, and, in the absence of the necessary molluscs, the life 

 cycle of the parasite fails. It is possible that the ducks may 

 transport the eggs of the snails from one pond to another, but 

 it seems to me that the danger therefrom is i>m^-h Ip-^' than that 

 due to the presence of the snails, nil kinds of which are greedily 

 devoured bv the ducks. 



