This work aimed to study the pathogenic effect of the Paenibacillus larvae spores on adult honey bee workers to explain the death many of them in the communities affected by American foul brood disease. This work was done through two methods; first injected the microbial suspension in the intersegmental membrane of the back lymph cavity of adult bee workers. The blood films were done after 1, 2, 4&12 hrs. beginning of the injection method, while with the feeding method it carried out after one, two and three months. During the first period of the microbial injection one hour later an elongation and minor abnormalities were occurred in some blood cells. The second stage began after 2 hrs. is characterized by loss of the blood cells dye strength. After 4 hrs. the third stage is characterized by increase atrophies of some blood cells. The fourth and final stage   after 24 hrs. abnormalities in most blood cells with sharp decline in their numbers clearly. This stage considers beginning end of the blood cells alive and the rapid death of most of bee workers was detected.  This experiment affirms that adult bee workers can be affected by the Paenibacillus larvae spores. That may be one reason  of death bee workers in infected bee colonies by the American foul brood disease.