Diagnosi di brucellosi e reazioni sierologiche falsamente positive: Una discesa nel "maelström" legislativo

Because of the economic losses due to abortions and infertility caused by brucellosis in livestock animals and the risk of transmission to humans, eradication plans are in place in Italy and other European Countries, consisting of the systematic diagnosis of brucellosis in ruminant herds and slaughter of infected animals. The diagnosis of brucellosis in ruminants (bovines, sheep, goats and buffaloes) is performed by means of official serological tests, such as rapid Seroagglutination test and Complement Fixation test. Both tests detect antibodies produced against the smooth Lipopolysaccharide (LPS) of the Brucella outer membrane. Because of the high analytical sensitivity and the systematic application of those tests, the prevalence of the disease has been markedly reduced. However, both tests fail to solve false positive serological reactions (FPSR), i.e. animals that test positive but are affected by other gram negative organisms, such as Salmonella spp, Escherichia coli O157, and Yersinia enterocolitica (Y.e.) O:9, that share components of Brucella LPS. According to Italian Veterinary Regulations, the status of FPSR in herds free from brucellosis cannot be explained and confirmed with other tests. The present review discusses this "Achille's heel" of the Italian regulations. Several diagnostic tests have been developed, based on other antigens or strategies: 1) ELISA tests based on Outer membrane proteins (OMP); 2) an ELISA test based on cytosoluble extracts from Brucella Rough strains, that have a different composition of LPS; 3) the brucellin test; 4) PCR, for the search of Y.e. O:9 in animal faeces, or Brucella spp. in organs.Moreover, the epidemiological situation in several regions is analysed. For instance, in regions such as Emilia Romagna and Veneto, that are officially free from brucellosis, specific regulations to solve FPSR are in place. On the opposite, the regions of the South of Italy present a critic situation, as officially free herds with cases of FPSR and infected herds may be present.