Abstract
Background:
Coxiella burnetii causes Q fever and represents a globally important zoonotic disease affecting both humans and animals. In ruminants, particularly sheep, the infection is often subclinical but can lead to reproductive losses, including abortion, stillbirth, weak lambs, and reduced fertility, with significant economic impact. In humans, C. burnetii causes acute febrile illness, pneumonia, or hepatitis and may progress to endocarditis. Despite its public and veterinary health relevance, information on the epidemiology and distribution of Q fever in Algeria remains limited, especially in major sheep-producing areas such as Tiaret Province.

Aim:
This study aimed to determine the seroprevalence of C. burnetii infection in sheep from Tiaret Province, northwestern Algeria, and to identify key animal-level factors associated with seropositivity.

Methods:
A cross-sectional study was conducted between December 2023 and July 2024. A total of 184 serum samples collected from sheep of different ages, genders, herd sizes, and management systems were tested for anti-C. burnetii antibodies using a commercial indirect enzyme-linked immunosorbent assay (IDVet®, France). Doubtful samples were excluded from the statistical analysis. Univariate and multivariate logistic regression analyses were performed to assess the relationship between seropositivity and selected explanatory variables.

Results:
The obtained results reveal a seroprevalence of 37.50% at the animal level. Univariate analysis indicated that seropositivity was significantly associated with age, herd size, herd composition, and farm type. Multivariable analysis confirmed that sheep aged ≥4 years (odds ratio (OR) = 4.16; p = 0.02) and herds containing >250 animals (OR = 37.47; p < 0.001) were at significantly higher risk of infection.

Conclusion:
Coxiella burnetii infection is endemic among sheep in Tiaret Province. The identification of age and herd size as major risk factors underscores the need for improved reproductive management, enhanced biosecurity practices, and targeted surveillance measures. Integrating these practices within a One Health framework is essential for reducing disease transmission, protecting public health, and mitigating economic losses in Algerian sheep production systems.

Key words: Algeria; Coxiella burnetii; Q fever; Risk factors; Seroprevalence.