Heterogeneous shedding of Brucella abortus in milk and its effect on the control of animal brucellosis.
OBJECTIVE
To ascertain whether in Brucella abortus-infected water buffalo herds, the number of newly infected animals could be reduced by culling superspreaders (the animals secreting > or =10(4) CFU per ml of milk).


RESULTS
The number of B. abortus present in the milk (CFU per ml) from 500 water buffaloes was measured by the culture. Each animal was tested three times, at one month intervals. The presence or the absence of B. abortus in each milk sample was confirmed by PCR. A majority of infected animals shed the pathogen at a low level (< or =10(3) CFU ml(-1)). However, a few infected individuals (superspreaders) shed large numbers of B. abortus (> or =10(4) CFU ml(-1)). Quantitative PCR of B. abortus positive milk samples gave comparable results to culture. Culling of the superspreaders was sufficient to arrest the spread of infection.


CONCLUSIONS
The approach described here can reduce significantly the cost of controlling brucellosis. Culture and quantitative PCR tests identify superspreaders and, compared with the serological tests in use to detect brucellosis, provide also a more accurate estimate of the disease incidence.
Capparelli
R
R
Faculty of Biotechnological Sciences, University of Naples Federico II, Naples, Italy.
Parlato
M
M
Iannaccone
M
M
Roperto
S
S
Marabelli
R
R
Roperto
F
F
Iannelli
D
D
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D002003:Brucella abortus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D002007:Brucellosis, Bovine / Q000175:diagnosis* / Q000382:microbiology / Q000517:prevention & control; D002020:Buffaloes / Q000276:immunology / Q000382:microbiology*; D002417:Cattle; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000662:veterinary
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial