Abstract Changes in the total protein concentration of haemolymph and ovaries in Ornithodoros erraticus mated fed females uninfected and infected with Borrelia crocidurae were studied during vitellogenesis and at the end of oviposition. In the uninfected mated females, engorgement was followed by a decrease in the haemolymph total protein concentration immediately and for the following 2 days after feeding, then the level of haemolymph protein gradually increased on the following days to reach maximum levels on 5 – 9 d.a.f. The ovary total protein level increased gradually on the 1^st d.a.f, then the increase continued evidently on the following days to reach a maximum on 9 d.a.f (day of oviposition).At the end of oviposition the level of haemolymph and ovaries total protein largely decreased. The increase in the level of haemolymph proteins was positively correlated with the increase in the ovary total protein, ovary weight and number of mature oocytes inside the ovary. Changes in the haemolymph and ovaries total protein concentration of mated females infected with Borrelia crocidurae followed the same pattern of the uninfected ones. However, borrelial infection reduced the level of haemolymph and ovaries total protein during most of the preoviposition period (3 – 9 d.a.f). Also the weight of ovary and number of mature oocytes were lower in the infected than uninfected on the 5^th- 9^th and 3^rd-9^thd.a.f, respectively. Freshly deposited eggs of the infected females had lower total protein concentration than those deposited by uninfected females.