ABSTRACT
Brucellosisisazoonosisofmajorpublichealth,animalwelfare,and economic significance,andisendemicinlivestockinUganda.The transmission of this disease in cattle and humans involves a multitude of risk factors, with unprocessed animal products accounting for most of the human infections. Most of unprocessed livestock products like milk in Uganda are consumed by the urban population. To shed new light on the epidemiology of brucellosis in urban and peri-urban areas in Uganda, a cross-sectional study wascarriedouttoestimatethesero-prevalenceofbrucellosis, identifyfactorsassociatedwithsero-positivity, isolate, biotype and molecularly characterize Brucella isolates from cattle milk and determine antimicrobial susceptibility in GuluandSoroti towns. Gulu and Soroti are the two rapidly growing towns in northern and eastern Uganda, respectively, with a high rate of rural to urban human migration and growing urban and peri-urban livestock farming.A totalof1007seraanddataonbiologically plausibleriskfactorsfrom166herdsandtheir spatial locations, were collected from cattle reared in urban and peri-urban GuluandSorotitownsofUganda.Theserawereanalyzedusing indirect ELISA and sero-positive reactors confirmed by competitive ELISA. Multivariablemodels wereused to investigate forrisk factors. Milk samples were collected from lactating cattle at the time and cultured in Brucella selective media. The isolates were bio-typed and molecularly characterized and their antimicrobial susceptibility determined using the broth micro dilution method. The overallanimal-level and herd-levelsero-prevalence was7.5% (n = 1007, 95% CI: 6.15 – 9.4%) and 27.1% (n = 166, 95% CI: 20.9% - 34.3%), respectively. Herd-level sero-prevalence was significantly (p0.001)higherinSorotithanGulu. InGulutown,sero-positivityincreasedwithan increase inherdsize (p=0.03) andage(p=0.002),andwashigher in cattle broughtinfrom westernUganda(p0.0001).In Sorotitown,introductionofnewcattleintoaherdwassignificantly (p=0.027)associated withherdsero-positivity.Therewasageographically differentialrisk (clustering)ofBrucellasero-positivity inherdsinSoroti town. Thedata highlights differences in brucellosis risk factors in Gulu and Soroti towns and in turn calls for a tailored approach when designing control measures for prevention of transmission of bovine brucellosis in different areas. Brucella abortus without a biovar designation was isolated from eleven out of 207 milk samples from cattle in Gulu and Soroti towns of Uganda. These isolates had a genomic monomorphism at 16 variable number tandem repeat (VNTR) loci indicating that they may be from a common source of infection. The isolates showed in turn high levels of genetic variation when compared with other African strains or other B. abortus biovars from other parts of the world. Comparatively, the isolates had a closer genomic similarity with a Kenyan B. abortus strain (07-994-2411) than any other known strains from distant regions suggesting an epidemiological linkage. All the isolates were susceptible to tetracycline, streptomycin, gentamicin, ciprofloxacin, ceftazidime and cefotaxime, but had intermediate susceptibility to rifampicin. All isolates were resistant to ampicillin, sulfamethoxazole and trimethoprim, drugs that had shown activity in previous studies elsewhere. The isolates being resistant to rifampicin amidst high prevalence of tuberculosis in humans in Uganda calls for a judicious use of streptomycin and tetracyclines to avoid development of resistance, since these remain the best alternatives in such a setting.