Sero-prevalence and risk factors associated with occurrence of anti-Brucella antibodies among slaughterhouse workers in Uganda.

Introduction: Brucellosis is a febrile zoonosis occurring among high-risk groups such as livestock keepers and abattoir workers and is a public health priority in Uganda. The technical complexities of bacteriological and molecular methods make serological approaches the cornerstone of diagnosis of human brucellosis in resource limited settings. Therefore, proper application and interpretation of serological tests is central to achieve a correct diagnosis. Materials and methods: We conducted a cross-sectional study to estimate the seroprevalence and factors associated with anti-Brucella antibodies among slaughterhouse workers processing ruminants and pigs in three regions of the country with serial testing using a combination of the Rose Bengal Test (RBT) and the BrucellaCapt test. An authorized clinician collected 543 blood samples from consenting abattoir workers as well as attribute medical and social demographic data. Univariable and multivariable logistic regression were used to determine factors associated with anti-Brucella sero-positivity. Results and discussion: The sero-prevalence among ruminant slaughterhouse workers ranged from 7.3% (95% CI: 4.8–10.7) using BrucellaCapt to 9.0% (95% CI: 6.3–12.7) using RBT. Slaughterhouse workers from the Eastern regions (AOR = 9.84, 95%CI 2.27–69.2, p = 0.006) and those who graze animals for alternative income (AOR = 2.36, 95% CI: 1.91–6.63, p = 0.040) were at a higher risk of exposure to Brucella. Similarly, those who wore Personal Protective Equipment (AOR = 4.83, 95%CI:1.63–18.0, p = 0.009) and those who slaughter cattle (AOR = 2.12, 95%CI: 1.25–6.0, p = 0.006) were at a higher risk of exposure to Brucella. Those who slaughter small ruminants (AOR = 1.54, 95%CI: 1.32–4.01, p = 0.048) were also at a higher risk of exposure to Brucella. Conclusions and recommendations: Our study demonstrates the combined practical application of the RBT and BrucellaCapt in the diagnosis of human brucellosis in endemic settings. Both pharmaceutical (e.g., routine testing and timely therapeutic intervention), and non-pharmaceutical (e.g., higher index of suspicion of brucellosis when investigating fevers of unknown origin and observation of strict abattoir hygiene) countermeasures should be considered for control of the disease in high-risk groups. Author summary: Brucellosis is a febrile zoonosis occurring among high-risk groups such as abattoir workers and is a public health priority in Uganda. Whereas bacteriological isolation is conclusive, and some molecular methods have been found useful for diagnosis of brucellosis, they are technically complex and may delay commencement of treatment. Therefore, clinicians from resource poor settings rely on clinical examination and serology for diagnosis of human brucellosis. However, brucellosis lacks pathognomonic signs, and clinically resembles other endemic febrile illnesses which complicates diagnosis. Poor quality Brucella antigens, serological tests not validated for human use, and lack of consensus on the tests of choice complicate diagnosis of brucellosis. Previously, many studies employed a variety of tests to estimate sero-prevalence of brucellosis in high-risk groups leading in some cases to over estimation of the disease in Uganda. Here we applied the RBT and BrucellaCapt tests in a serial testing scheme to detect contacts, short and long evolution cases of brucellosis and report a sero-prevalence ranging from 7.3% to 9.0% among slaughterhouse workers in Uganda. Brucella seropositivity was associated with the region where participants worked, the slaughter of cattle, small ruminants, and grazing animals as an activity outside the work of the slaughterhouse. [ABSTRACT FROM AUTHOR]