Sensitivity and specificity of an indirect enzyme-linked immunoassay for the diagnosis of Brucella canis infection in dogs

• Published in: Journal of medical microbiology Vol. 51; no. 8; pp. 656 - 660
• Main Authors: LUCERO, N.E, ESCOBAR, G.I, AYALA, S.M, LOPEZ, G
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01-08-2002; Society for General Microbiology
• Subjects: Agglutination Tests - veterinary; Animal bacterial diseases; Animals; Antibodies, Bacterial - blood; Bacterial diseases; Bacteriological methods and techniques used in bacteriology; Bacteriology; Biological and medical sciences; Brucella - isolation & purification; Brucellosis - diagnosis; Brucellosis - microbiology; Brucellosis - veterinary; Dog Diseases - diagnosis; Dog Diseases - microbiology; Dogs; Enzyme-Linked Immunosorbent Assay - methods; Enzyme-Linked Immunosorbent Assay - veterinary; Female; Fundamental and applied biological sciences. Psychology; Infectious diseases; Male; Medical sciences; Microbiology; Sensitivity and Specificity; Performance evaluation; Fissipedia; Carnivora; Brucella canis; Enzyme immunoassay; Infection; Vertebrata; Mammalia; Brucellaceae; Bacteriosis; Bacteria; Brucellosis; Diagnosis; Veterinary; Dog; ELISA assay
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/0022-1317-51-8-656

Brucellosis Laboratory, ANLIS Dr C. G. Malbrán, Avda Velez Sarsfield 563, 1281 Buenos Aires and *Zoonosis Center, Municipalidad Lomas de Zamora, 12 de octubre 1060, Banfield, Argentina
Corresponding author: Dr N. E. Lucero (e-mail: nidia{at}elsitio.net ).
Received 31 Jan. 2002; accepted 8 March 2002.
Abstract
The diagnosis of B. canis infection in dogs is based on bacteriological examination and serological methods including agglutination and gel diffusion tests. Bacteriological studies are the only methods that have been considered specific but, as intermittent periods of abacteraemia may occur, a negative blood culture cannot be used as a criterion for excluding canine brucellosis. Close contact between people and infected dogs increases the risk of transmission; however, its impact on public health is probably underestimated due to lack of reporting and inadequate diagnostic services. This paper describes an indirect enzyme-linked immunoassay (IELISA) procedure for the diagnosis of brucellosis caused by B. canis in a population of normal and infected dogs previously screened by the buffered plate antigen test (BPAT) and rapid slide agglutination test (RSAT). The serological survey was performed with 446 field sera. The 270 sera from the asymptomatic group found negative by BPA, RSAT and blood culture showed IELISA specificities of 96.7% and 100%, respectively, when cut-off values of OD 0.237 and 0.281 were selected. For 52 sera from culture-positive dogs, IELISA sensitivity was 100% with cut-off values of OD 414 0.237 and 0.281. OD 414 0.281 was selected because this value provided the highest accuracy with minimal false-negative and false-positive results. This cut-off value was used to study 124 blood culture-negative but RSAT positive sera. IELISA produced 107 positive results; the 17 sera that were negative by IELISA presented a wide range of reactivities by RSAT (2 were RSAT positive at 1 in 2 dilution and 15 were weakly positive with pure serum). These samples were probably from animals at an early stage of the infection or were false-positive results. The IELISA described here detects IgG and IgA antibodies that are useful for evaluating the clinical status of dogs. Although RSAT is a practical screening test, a supplementary technique such as IELISA should be used on all positive RSAT samples to ensure diagnostic specificity. Furthermore, people in contact with infected dogs could be investigated for possible transmission. The procedure described in this study was relatively simple and could have widespread applications.