A new public health problem arises from animal trypanosomes that afflict human by a disease called atypical human trypanosomiasis. Although humans have an innate protection against most Trypanosoma species, nineteen cases of atypical human trypanosomiasis caused by the animal trypanosome as T. b. brucei , T. vivax, T. congolense , T. evansi and T. lewisi have been recorded. Some of theserecorded cases were transient, six required trypanocidal treatments however two patients died. Rodent trypanosome, T.lewisi is transmitted via ingestion of fleas or their feces containing the infective stage, the metacyclic trypomastigote. Because of the high densities of various species of rodents and their distribution all over the country especially in rural areas, the present work aimed to evaluate the trypanosomiasis among rodents collected from November to March 2016 and study transmission probability by their fleas in some rural areas in Abu Alnomros Center, Giza. The overall trypanosomiasis prevalence among the different rodent species was (21 rats) 24.7%. All the infected rats belonged to Rattus r. spp where the prevalence of infection with Trypanosoma lewisi among that species was very high 51.2% while none of rats belonged to Rattus norvegicus were infected. That may be attributed to the solid immunity gained by the R. norvegicus where most of the collected norvegicus were aged and weighed more than 200 grams. There was an inverse significant correlation between the densities of parasites and the weights of the hosts. The rat which recorded the highest parasite density (60,000 parasites/ microliter) was a female Rattus r. captured indoor (inside house). As to sex of Rattus rattus spp no significant difference was found between males and females in trypanosomiasis. Also there was no significant correlation between the densities of parasites and the number of white blood cells among Rattus rattus spp. All positive rats were collected indoors (from houses) and all the rats which were captured from outdoors (farms) were negative for T. lewisi. The difference between infections with trypanosomiasis among rats inhabited the houses and that found in farms was highly significant. Only two species of fleas were found on rats, Xenopsylla cheopis and Leptopsylla segnis. The oriental fleas, X. cheopis, were found mainly on R. norvegicus where 57.5% of R. norvegicus were positive for X. cheopis while only one rat was positive for L. segnis. On other hand the
rat fleas, L.segnis, were found mainly on Rattus rattus spp where 39% of these rats were positive for L. segnis. The present work revealed a significant correlation between the infection with T. lewisi and the presence of L. segnis on the rats however that correlation regarding X. cheopis was not significant.