Seasonal abundance of Ornithodoros (O.) savignyi and prevalence of infection with Borrelia spirochetes in Egypt.

The seasonal dynamics of Ornithodoros (O.) savignyi and infection with Borrelia sp. in the tick, domestic animals and man were investigated in the village of Dahshore, Giza governorate from August 1996 through July 1997. The tick population densities of adults and immatures were high during the period from June to October with maximum levels in August and September respectively. Adults predominated (58.6%-80.0%) in October to May with the highest abundance in January while immatures prevailed (51.3%-65.8%) during the rest of the year reaching a peak in September. Of 1202 tick examined, the spirochetes were detected in 427 (35.5%). The annual infection rate in adults and immatures varied from 34.4%-36.9% with no significant difference among larvae, nymphs, males and females. Of 1396 sera from man and 553 sera from host animals tested, 309 (22.1%) and 157 (28.4%), respectively, were reactive for antibody to Borrelia sp. antigen with the highest infection rate in camel (47.8%), followed by sheep (23.8%), goat (18.0%) and cow (16.0%), then the least in buffalo (10.9%). Changes in prevalence of Borrelia infection in the tick population correlated positively with changes in antibody prevalence in man and camel and with changes in the tick population density. The four events were lowest in winter and early spring and increased afterward to reach maxima during summer or the early fall (July-September).