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IDEXX Animal Health Updates
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your timely update of animal health and diagnostics
information.
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November 2003 Worldwide Edition
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IN THIS
ISSUE
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THE LATEST NEWS
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 In Ruminant Testing |
| Brucella abortus and Brucella
melitensis—organisms that can cause reproductive disease in
ruminants and potentially in humans |
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Disease
Brucella, particularly Brucella abortus (B. abortus),
is the causative agent of bovine brucellosis. In some countries with
close association between cattle, sheep and goats, infection can also
be caused by Brucella melitensis (B. melitensis). B.
melitensis is the principal organism that causes reproductive
disease in small ruminants.
In 1887, Sir David Bruce described B. melitensis causing
abortion in sheep and goats as the cause of Malta fever in humans. In
1897, the Danish veterinarian Frederik Bang found a relation between B.
abortus and abortion in cattle.16 B. abortus
and B. melitensis are also causes of undulant fever in
humans.8 Abortion in cows, mostly in the first three months
of pregnancy or after seven months due to placentitis without any
other signs of disease, is the most outstanding clinical feature of
the disease. If a carrier state develops, in the majority of the
infected cows, the clinical manifestations may be reduced milk
production, infertility and resorption of the fetus, and a higher
frequency of retained placentas. Disease in bulls may produce
infection of the seminal vesicles and testicles, causing orchitis and
epidymitis, which can result in shedding of the organism in semen.
Long-standing infections may result in arthritis, tendonitis and
bursitis in some cattle
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| Figure 1 |
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In sheep and goats, B. melitensis is the principal cause
of abortion, with occasional abortion due to B. abortus.
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Table 1: Brucella species, their hosts and clinical signs
of disease.
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| Species |
Host |
Disease |
| B. abortus |
cattle, sheep, goat, swine, horses, humans |
abortion, orchitis, bursitis, undulant fever |
| B. melitensis |
goat, sheep, cattle, humans |
abortion, sporadic abortion, Malta fever |
| B. suis |
swine, humans |
abortion, orchitis, arthritis, spondylitis, undulant fever |
| B. ovis |
sheep |
epididymitis, sporadic abortion |
| B. canis |
dog, human |
abortion, epididymitis, discospondylitis, infertility, undulant
fever |
| B. neotomae |
Neotomae lepida (round worm) |
apathogen |
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The primary modes of disease transmission are direct by copulation,
or indirect by ingestion of infected tissue of aborted fetuses, fetal
membranes, uterine fluids or milk. Transmission by artificial
insemination may occur as well.
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Brucella spp.
Brucella spp. are facultative intracellular, small
Gram-negative coccoid rods. They are rigid and do not have a capsule.
Brucellae are able to grow in either aerobic or microaerophilic
conditions, and have special requirements for culture. There are
smooth and rough forms of culture colonies based on lipopolysaccharide
expression (Figure 2). For B. abortus and B. melitensis,
the smooth strains are considered virulent.7
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| Figure 2 |
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Pasteurization and disinfectants easily inactivate Brucella spp.
However, the organisms can survive in urine for several days, in
manure for several months, in milk for six weeks, in butter for four
months and in meat stored in packing plant coolers for 14 days.14
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Zoonotic risk
B. abortus and B. melitensis are zoonotic agents.
Infection may occur via either the conjunctiva or abraded skin, but
ingestion of contaminated dairy products constitutes the main risk to
the public.3 In 2000, the EU member states reported 2857
cases of brucellosis in humans compared to 3899 in 1999.9 Brucella
spp. may cause orchitis, chronic arthritis and infertility in humans.
Veterinarians and farmers who work with Brucella-infected
ruminants and consumers of raw milk products from infected animals are
at risk for abortion, orchitis, chronic arthritis and infertility.12
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Scope
Several member states of the EU have already gained an official status
of being free of bovine brucellosis (Austria, Denmark, Finland,
Germany, Luxembourg, Sweden and the province of Bolzano in Italy). The
Netherlands, Great Britain and Norway are officially bovine
brucellosis-free as well. In most of the other member states of the
EU, eradication programs for bovine brucellosis have been implemented.9
While nine members of the EU are recognized as officially free of B.
melitensis, four EU member states have not yet reached this
status for any of their regions. In Greece, ovine and caprine
brucellosis due to B. melitensis is a significant problem for
human health and animal production.9
The United States is free of brucellosis except for Texas and
Missouri, which are almost free. Australia has been free of bovine
brucellosis since 1992.4 In Central and South America and
eastern European countries, brucellosis is still a serious problem.
In dairy farms with intensive production in tropical areas, up to
80% of the cattle can be infected. For extensive beef and milk farms
in the Sahel region in Africa, up to 30% of the cattle are assumed to
be infected.14
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Diagnosis
For direct diagnosis of Brucella spp., microscopic evaluation
of stained smears from aborted tissue or cultured material,
immunofluorescence staining, phage typing and PCR are commonly used.
The diagnosis of bovine brucellosis is almost exclusively based on
serological tests for the detection of antibodies to B. abortus
and B. melitensis.10
A variety of serological tests can be used:
- Serum agglutination test (SAT)
- Plate agglutination
- Card test (rose-bengal-test)
- Mercaptoethanol test
- Rivanol agglutination test
- Agar gel immunodiffusion
- Complement fixation
- Brucella ring test (Bang ring test)
- ELISA
The OIE and the EU have implemented recommendations and guidelines
for the use of these serological tests. Because the serum
agglutination test is unsatisfactory for the detection of bovine
brucellosis, it is no longer recommended by the OIE.3
Because the diagnostic performance of some enzyme-linked immunosorbent
assays and the fluorescence polarization assay are comparable with, or
better than, that of complement fixations tests, and because they are
more robust and simpler to perform, their use may be preferred.11,
15 All serological brucellosis tests show to a different extent
cross-reactivity with LPS antigens from other bacteria, such as Yersinia
enterocolitica (0:3, 0:6, 0:9) or E. coli (O157:H7).
Serological techniques are the mainstay of diagnosis and mass
testing programs. The most successful of the serological diagnostic
tests for B. abortus and B. melitensis are based on
the detection of antibodies to LPS antigen of smooth Brucella
strains.10
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IDEXX HerdChek* Brucella Antibody Tests
IDEXX Laboratories offers three ELISA systems for the detection of
antibody to Brucella:
HerdChek Brucella abortus Antibody Test Kit
The HerdChek B. abortus test is an indirect enzyme
immunoassay for the detection of antibody to Brucella abortus
in bovine milk samples, using LPS antigens.
- Six-strip microtiter plate format
- Detects antibodies to Brucella LPS antigens
- Brucella abortus strain 1199/3 antigen†
- Monoclonal IgG1 conjugate†
- Sensitive to test bulk milk of up to 200 milk samples‡
- Easy-to-use reagents
- Kit interpretation guidelines for areas using vaccination to
control B. abortus, and for B. abortus-free or
nonvaccinated populations
For more information, download
the information sheet. 
Note: Only the indirect ELISA format is recommended by the OIE to
test milk samples.3
HerdChek Brucella abortus Antibody Test Kit
(Serum)
The HerdChek B. abortus (Serum) test is an indirect enzyme
immunoassay for the detection of antibody to Brucella abortus
in bovine serum samples, using LPS antigens.
- Six-strip microtiter plate format
- Detects antibodies to Brucella LPS antigens†
- Brucella abortus strain 1199/3 antigen†
- Monoclonal IgG1 conjugate†
- Ready-to-use reagents
IDEXX has validated this test for testing pools of 10 serum or
plasma samples (data on file). Contact IDEXX Technical Services for
more information. In the U.S., call 1-800-943-3999.
Outside the U.S., contact your local IDEXX representative.
For more information, download
the information sheet.
HerdChek Brucellosis Antibody Test Kit (small ruminant,
sheep and goats)
- Optimized for the detection of antibody to Brucella spp.
in serum samples from sheep and goat
- For use in conjunction with the HerdChek B. abortus
Antibody Test Kit (Serum)
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Disease control and eradication
There are two approaches: vaccination for disease control and "test
and cull" for disease eradication.
Vaccination of calves with B. abortus strain 19 increases
resistance to infection, but protection may not be complete and some
vaccinated cattle may become infected. Also some vaccinated cattle may
develop antibodies that interfere with diagnostic test results. Strain
RB 51 vaccine from an attenuated rough B. abortus strain has
largely replaced strain 19 vaccines because it does not cause
production of antibodies that interfere with serological tests.1
But the RB 51 vaccine can cause infection in calves if administered to
pregnant cattle. Even humans can be at risk for infection with RB 51
if they have contact with aborted infected tissue, placenta, blood or
amniotic fluid without wearing gloves, masks or eye protection.
Another potential risk for health hazard is vaccine administration by
unintentional needle stick injuries.5 For brucellosis
vaccines, there have been cases of suspected or confirmed adverse
effects in humans reported.2
Vaccination can help to reduce the number of reactors, but when
proceeding from a control to an eradication program, a test and
slaughter program is necessary.1 Countries that are free of
brucellosis or that have implemented brucellosis-control programs may
require Brucella spp.-free certification prior to shipping
cattle into their regions.
In areas with high prevalence of brucellosis, testing individual
serum, plasma or milk samples is a highly sensitive diagnostic tool
that is recommended by the OIE Manual of Standards for Diagnostic
Tests and Vaccines and by the EU regulation number 535/2002, Directive
64/432.6 In regions with low prevalence of brucellosis,
testing serum or plasma pools of 10 samples or bulk milk samples is a
very cost-efficient and reliable diagnostic tool for surveillance
testing.
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The LATEST NEWS
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| In transmissible spongiform
encephalopathy (TSE) testing |
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| Three second-generation postmortem TSE
products are in the late stages of development at IDEXX
The IDEXX Production Animal Services team has developed products
for the detection of bovine spongiform encephalopathy (BSE), scrapie
and chronic wasting disease (CWD). The tests represent significant
advancements in postmortem TSE testing. Sample preparation is
greatly simplified due to a novel chemical ligand licensed from
Microsens Biotechnologies that selectively captures PrPSc
in the presence of PrPC. These advancements have resulted
in a second-generation test with no proteinase K treatment, no
centrifugation, room-temperature incubation, less hands-on time and
results in under 4.5 hours. The CWD test has been submitted to the
USDA for approval in the United States, and the BSE and scrapie
tests have been accepted into the current round of TSE diagnostic
validation in the European Union. Stay tuned for further updates and
announcements as these exciting new tests become approved for use.
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TECHNICAL TIP OF THE MONTH
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Determination of kit expiration dates. Why is the kit's
expiration date sooner than its components?
Initially, lots of individual components making up the test kit
are tested to confirm performance is maintained over the long term.
Based on this testing, the component is given a certain expiration
date. Then, to determine the expiration date of the kit, there is
multi-lot testing of the kit as a whole. This testing may show good
performance past, for example, a 12-month expiration date, but to
ensure the highest quality product throughout the life of the test
kit, we may not give it the full dating observed in the other
components. Lastly, we are limited by our outline of production on a
kit-by-kit basis with the USDA, which specifies the allowable
expiration dates for each kit.
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LEARN MORE
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To learn more about our products and services, innovative
technologies, trusted service and support, and our global offices,
visit our Web site.
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VISIT US AT THE FOLLOWING EVENTS
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Bangkok, Thailand—November 9–13, 2003
The 11th International Symposium of the World Association of
Veterinary Laboratory Diagnosticians (ISWALD)
IDEXX will present on the following topics:
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Comparison of the Novel, Rapid Seprion Assay and a Standard
Proteinase K Immunoblotting Assay for the Detection of BSE and
other Transmissible Spongiform Encephalopathies
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Current Data on Detection of BVDV and BDV Infection Using
HerdChek* BVDV Antigen ELISA
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Serological Monitoring of Salmonella Infection in Swine
Using the HerdChek* Salmonella Antibody ELISA
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Atlanta, Georgia, USA—January 28–30, 2004
The
International Poultry Exposition (IPE)
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PEOPLE ON THE MOVE
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Amie Carmillo joins the Production Animal
Services team as a marketing associate in Westbrook, Maine, USA. She
received a B.A and an M.S. in biology, and recently received an MBA
from Babson College. Previously, she worked for Biogen, Inc.
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