Identification and molecular characterization of Brucella abortus and Brucella melitensis isolated from milk in cattle in Azerbaijan.

BACKGROUND: Azerbaijan currently ranks thirteenth in global incidence of human brucellosis, with an estimated annual incidence through 2000 at over 50 cases per million. Brucella melitensis has been isolated from patients and is thought to have been acquired through contact with small ruminants or as a foodborne infection. To reduce the burden of human brucellosis, the Azerbaijani government began in 2002, a nationwide vaccination control campaign in small ruminants. There is serological evidence of bovine brucellosis (presumably due to Brucella abortus) in Azerbaijan, but no prevalence estimates were available when this study started in March 2017. The aim of this study was to isolate and identify Brucella spp. from cow milk in the Ganja region, where brucellosis takes a heavy toll on humans and livestock. RESULTS: Blood and milk samples were collected from cows (n = 1075) in early lactation (up to 90-days) in farms that had a history of previous positive serological results and abortions. Twenty-two out of 57 milk samples collected from seropositive cows, showed growth on Farrell's media, when incubated with 5% CO2. Eight additional milk samples showed growth in the absence of CO2. The classical biotyping classified them as Brucella abortus (22) and Brucella melitensis (8). RT-PCR confirmed that strains belonged to the genus Brucella. MLVA profiles were obtained for DNA extracted from two B. abortus and six B. melitensis strains. While the B. abortus genetic profile was described in the MLVA database, matching the profile of B. abortus strains isolated in East Europe, Central Asia and China, we found a new genotype for the B. melitensis strains isolated in Azerbaijan, clustering with strains belonging to the American clade, rarely identified in the region. CONCLUSION: Despite the implementation of the vaccination program in small ruminants, our results suggest that spill-over events of B. melitensis from small ruminants to cattle have occurred. However, cattle are likely to be primarily infected with B. abortus, which warranted the implementation of a bovine brucellosis program. Such a program started in fall 2017. In the Ganja region, cattle should be considered as a potential source of B. abortus and B. melitensis for humans.

Working towards development of a sustainable brucellosis control programme, the Azerbaijan example.

Brucellosis caused by Brucella abortus and Brucella melitensis is endemic in the Republic of Azerbaijan but a complex mix of fiscal, political and technical constraints has impeded regulatory authority decision making for adoption of a sustainable national control programme. This paper reports a series of epidemiologic studies of the disease in animals and humans which we conducted between 2009 and 2020. A preliminary study and a subsequent larger study using vaccination of all non-pregnant female sheep and goats of breeding age and all females between 3 and 8 months with conjunctival Rev1 vaccine both recorded significant reduction in small ruminant seroprevalences. A case control study of winter pasture flocks found many case and control farmers used raw milk to make dairy products for sale, ate fresh cheese and sold dairy products in unregulated markets. Almost all farmers expressed willingness to pay a portion of the costs associated with elimination of brucellosis from their flocks. A pilot human study in 2009 led to a large study in 2017 which recorded an overall seroprevalence of 8.1% in humans. Persons in farm related occupations were at greater risk than urban persons and males were more likely to be seropositive than females. Risk factors included keeping small ruminants, using raw milk cheese and slaughtering animals whereas having heard education information about brucellosis and vaccinating against brucellosis were protective.