Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt.

The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.