[Mixed infection in ticks: a rule or an exception?].

A hypothesis for the independence of acts of infection in ticks with pathogens from each other in mixed infection has been tested on the basis of the data available in the literature. In most cases the number of ticks with mixed infection is consistent with the independence hypothesis and fails to reinforce the statement that there is antagonism of pathogens. But in some reports the number of mixed-infected ticks is 3-13 times higher than the calculated number according to the accepted hypothesis. These facts suggest that the natural tolerance of ticks to pathogens due to primary infection may be reduced. Other possible reasons for differences in the actual and calculated number of mixed infected ticks are also discussed.