20e - Brucellosis outbreak in northwestern Tajikistan in 2023: a matched case-control study
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Background : A sharp increase in brucellosis incidence was observed in northwestern Tajikistan (from 1.0/100,000 people in 2022 to 32,7/100,000 by May 2023). Most cases, 82% (84/103), were from the same village (population=10,712). We investigated to identify risk factors and mitigate disease.
Methods : Using a case-control design, we conducted face-to-face interviews and collected blood from May-July 2023. Cases were the first person in a household diagnosed with brucellosis in February-June 2023. Two controls were selected for each case (neighbors from different households matched by age and sex). Controls testing positive were excluded (13%). We conducted conditional multivariable logistic regression to assess association with brucellosis.
Results : Of 84 cases, 57 (58%) met inclusion criteria. Of which, 68% were 15-44 years old and 44% were male. Common symptoms were joint pain (95%), fever (84%), weakness (72%), and night sweats (65%). All cases and 94% of controls (n=114) had unvaccinated livestock (mostly cattle, sheep or goats). A greater proportion of cases than controls had consumed homemade kaymak (clotted cream from unpasteurized milk) (89% vs 36%), home-produced meat (98% vs 82%) or neighborhood-produced milk (81% vs 61%); or engaged in animal slaughter (42% vs 11%) or animal grooming (32% vs 10%). Brucellosis was associated with consumption of homemade kaymak (adjusted odds ratio [AOR]=60.6, confidence interval [CI]=4.2-873.0, p=0.003), homemade meat (AOR=55.1, CI=1.2-2,549.0, p=0.040), neighborhood milk (AOR=8.6, CI=1.6-47.9, p=0.014), animal slaughter (AOR=50.9, CI=2.8-919.0, p=0.008) or animal grooming (AOR=15.6, CI=1.1-234.0, p=0.047).
Conclusions Contact with unvaccinated livestock or consumption of their products was a key contributor to this outbreak. Cases were likely higher than reported. Following our investigation, an education and vaccination was carried out and no more brucellosis cases were reported after August 2023.