BRUCELLOSIS - Chapter 3.1.4 - Infection with B. abortus, B. melitensis and B. suis

Sep 14, 2026

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Brucellosis is an animal and human infection caused by multiple Brucella species, mainly B. abortus, B. melitensis and B. suis, with distinct host patterns in cattle, sheep and goats, and pigs. Clinical disease in animals includes abortion, infertility, retained placenta and reproductive tract inflammation, with organisms excreted in uterine discharges, milk, urine and semen. Diagnosis relies on isolation from relevant materials; detection may use staining, serology, and PCR-based DNA testing. The document also details screening and confirmatory immunity tests and key vaccine and diagnostic biological requirements.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages47

Reading Time1 h 58 min

AccessFree to download

Summary

Description of the disease

Detection of the agent

Serological and cellular immunity tests

Requirements for vaccines and diagnostic biologicals

Introduction

Causal pathogens

C H A P T E R 3 . 1 . 4 . BRUCELLOSIS ( INFECTION WITH B. ABORTUS, B. ME LIT ENSIS AND B. SU IS) SUMMARY Description of the disease: Brucellosis is the generic name used for the animal and human infections caused by several species of the genus Brucella, mainly Brucella abortus, B. melitensis and B. suis. Infection with Brucella in cattle is usually caused by B. abortus, less frequently by B. melitensis, and occasionally by B. suis. Brucella melitensis is the main causative agent of infection with Brucella in sheep and goats. Brucella melitensis and B. abortus may also infect other species, including camels. Infection with Brucella in pigs is due to B. suis biovars 1–3, but the disease caused by biovar 2 differs in its host range and its limited geographical distribution. In some areas, B. suis infection has become established in wild pigs. Clinically, infection with Brucella in animals is characterised by one or more of the following signs: abortion, infertility, retained placenta, orchitis, epididymitis and, rarely, arthritis, with excretion of the organisms in uterine discharges, milk, urine and semen. Unequivocal diagnosis depends on the isolation of Brucella from abortion material, udder secretions or from tissues removed at post-mortem. Brucella abortus, B. melitensis and B. suis are highly pathogenic for humans, and potentially contaminated tissues, cultures and materials must be handled under appropriate containment conditions. Detection of the agent: Indication of Brucella is provided by the demonstration of Brucella-like organisms in abortion material or vaginal discharge using modified acid-fast staining, and is considered presumptive, especially if supported by serological tests. Polymerase chain reaction (PCR) methods are additional means for detection of the presence of Brucella DNA in a sample. Whenever possible, Brucella spp. should be isolated by culturing samples from uterine discharges, aborted fetuses, udder secretions or selected tissues, such as lymph nodes and male and female reproductive organs. Species and biovars can be identified by phage lysis, and by cultural, biochemical and serological tests. PCR can provide the basis of complementary identification and typing methods based on specific genomic sequences. Serological and cellular immunity tests: Serological tests indicate exposure to Brucella species, but cannot identify the aetiological agent to the species level. The buffered Brucella antigen tests (rose bengal test and buffered plate agglutination test), the complement fixation test, the enzyme-linked immunosorbent assays (ELISA) or the fluorescence polarisation assay, are suitable tests for screening of herds/flocks and individual small ruminants, camelids and bovines (cattle and buffaloes). However, no single serological test is appropriate in each animal species and all epidemiological situations, and some of these tests are not adequate for diagnosing brucellosis in pigs. Therefore, the reactivity of samples that are positive in screening tests should be assessed using an established confirmatory or complementary strategy. The indirect ELISA or milk ring test performed on bulk milk samples is effective for screening and monitoring dairy cattle. The brucellin skin test can be used in unvaccinated ruminants, camels and swine as either a screening or a confirmatory herd test when positive serological reactors occur in the absence of obvious risk factors. Requirements for vaccines and diagnostic biologicals: Brucella abortus strain 19 and B. melitensis strain Rev.1 remain the reference vaccines for the control of Brucella infections in cattle and in sheep and goats, respectively, with which any other vaccines should be compared. Both should be prepared from adequately derived seed cultures. The rough B. abortus strain RB51 vaccine has also become the official vaccine for prevention of B. abortus infection in cattle in some countries. No suitable vaccines exist for the control of Bru

FAQs

Which Brucella species are mainly associated with brucellosis in animals and humans?

Brucellosis is caused by several Brucella species, mainly B. abortus, B. melitensis and B. suis. The text also notes B. canis and that B. ovis infection in sheep is covered separately.

How is brucellosis diagnosed in animals?

Unequivocal diagnosis depends on isolating Brucella from abortion material, udder secretions, or post-mortem tissues. Presumptive detection can use modified acid-fast staining and serology, while PCR can detect Brucella DNA in a sample.

What serological and cellular immunity tests are used for screening and confirmation?

Serological tests indicate exposure but may not identify the agent to species level. The document lists rose bengal test, buffered plate agglutination, complement fixation, ELISA and fluorescence polarisation for screening, with confirmatory strategies required because no single test fits all species and epidemiological situations.

What vaccine and diagnostic biological requirements are specified?

Reference vaccines include B. abortus strain 19 for cattle and B. melitensis strain Rev.1 for sheep and goats, with other vaccines to be compared to these. RB51 is an official vaccine for B. abortus in some countries; no suitable vaccines exist for swine. Brucellin and serological test antigens must meet preparation standards and be derived from specified smooth strains.

Sep 14, 2026

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