Endemic instability of ovine babesiosis in Turkey: A country-wide sero-epidemiological study.

Ovine babesiosis is an endemic tick-borne disease of small ruminants in the Middle East, European, and some African and Asian countries, including Turkey. This study assessed whether the endemic status of this disease was stable or instable, which is important for disease control efforts. For this aim, 4115 sheep blood samples were collected from 81 cities in the seven geographical regions of Turkey. The diagnosis of Babesia ovis was made using microscopic and serological techniques. Thin blood smears were prepared from anticoagulated venous blood. Serum samples were screened for specific antibodies using an enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody test (IFAT). Recombinant Babesia ovis secreted antigen 1 (rBoSA1) was used in the ELISA. The antigen slides used in the IFAT were prepared from the B. ovis-infected blood at a high level of parasitemia (5 %). The animals were divided into three groups according to their age: group I (one to six months), group II (6-12 months), and group III (older than one year). The endemic status of B. ovis was determined according to the inoculation rate (h value) calculations. Babesia spp. merozoites were observed in 40 (0.97 %) of the slides. Seropositivity rates were 29.89 % (1230/4115) and 49.16 % (2023/4115) by the ELISA and IFAT, respectively. According to the IFAT results, 31.7 %, 33.6 %, and 52.8 % of the animals were seropositive in groups I, II, and III, respectively. The inoculation rates of the animals indicated that the endemic status of ovine babesiosis was mostly instable throughout the country. Endemic stability was found only in group I from four regions (Central Anatolia, Eastern Anatolia, Aegean, and Mediterranean). Based on these results, the risk of clinical infection due to tick infestation was high when the maternal immunity and non-specific age resistance weakens or disappears. Thus, vaccination is needed to protect sheep against B. ovis infections in Turkey.