COCCIDIOSIS IN BIRDS AND MAMMALS 297 



Among the coccidial infections of lower animals, bovine coc- 

 cidiosis is probably the most important economically, with poultry 

 coccidiosis coming next. Tremendous losess occur each year, due 

 to coccidiosis of fur-bearing animals, particularly rabbits and foxes 

 raised on a commercial scale. Coccidiosis of swine, sheep, goats, 

 pets and experimental animals adds to the importance of discov- 

 ering some effective method of treating the disease. Animals have 

 been treated with a vast variety of drugs, particularly the com- 

 pounds and dyes known to possess more or less parasiticidal activ- 

 ity, but without any degree of success that other investigators have 

 been able to confirm. A certain amount of work has also been 

 done on the relation of diets to coccidiosis. Perhaps the most out- 

 standing of the recent contributions on this subject is the work 

 of Beach and his collaborators (Beach and C'Orl, 1925; Beach, 

 1925, and Beach and Davis, 1925) on the coccidiosis of chickens. 

 Using percentage mortality as a criterion of the efficacy of their 

 treatment, these workers found that a diet containing forty per 

 cent skim-milk powder was very effective in controlling experi- 

 mental poultry coccidiosis. They attributed the protective property 

 of this diet to its high content of lactose (50.6 per cent) which, 

 they showed experimentally, low^ered the pH of the cecal contents 

 from a normal range of 6.0 to 7.4 to a range of 4.4 to 5.6. It was 

 believed that the increased hydrogen-ion concentration of the 

 csecal contents was injurious to the merozoites. This treat- 

 ment did not eliminate coccidiosis but considerably reduced the 

 percentage mortality. Further investigations of this type are 

 needed. 



Host-Parasite Specificity. The problem of host-parasite specifi- 

 city probably ranks next to that of therapy in coccidiosis. Man is 

 concerned to know whether or not the coccidia of the lower ani- 

 mals are ever infective to him, whether or not the rats which live 

 in the barn are susceptible to infection by rabbit coccidia and 

 whether or not they can transmit it to cattle. Are the English 

 sparrows which fly from one poultry yard to another capable of 

 transmitting poultry coccidiosis biologically? A considerable quan- 

 tity of evidence has accumulated (see Andrews, 1927, for litera- 

 ture on host-parasite specificity of coccidia of mammals), most 

 of which tends to establish the fact that the coccidia of one species 

 of host are not infective to another. One notable exception to this 

 rule appears to be the cross-infectivity of the coccidia of cats and 



