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Transcript
Managing Abortive Disease
Test With Confidence™
Controlling reproduction losses in
ruminant herds—impact and diagnostic
solutions of four major abortive diseases.
•Chlamydiosis
•Neosporosis
•Q Fever
•Toxoplasmosis
Abortifacient infectious diseases level a massive impact on herd
productivity in every region of the world. Some of these diseases
can travel undetected in herds and result in unforeseen abortion
outbreaks; some can cause fetal or newborn deaths and induce
infertility; and some can result in a persistent or recurring infection
in herds with long-term poor reproductive performance. The total
reproductive losses resulting from these diseases are a primary
threat to the long-term economic vitality of herds. In addition, many of
these diseases are a threat to human public health, both emphasizing
the need to control transmission and complicating the procedures
required to do so. This brochure explores four major ruminant
infectious diseases affecting herd reproduction—Chlamydiosis,
Neosporosis, Q Fever, and Toxoplasmosis—and discusses the latest
diagnostic tools to control each.
Four diseases, One protocol
Chlamydiosis
Chlamydophila abortus, formerly known as
Chlamydia psittaci immunotype 1, is the
causative agent of ovine chlamydiosis (enzootic
abortion). The disease primarily affects sheep
and goats and less commonly, cattle and deer.
C. abortus causes considerable reproductive
losses worldwide, particularly in areas where
herds are kept closely congregated during
lambing season.
Vast amounts of bacteria are shed at the
time of abortion or birth in the placenta and
in uterine discharges. This contagious time
period can extend from more than two weeks
prior to abortion/birth to more than two weeks
following. Initial C. abortus infection occurs after
a susceptible animal is exposed to infected
parturition material, and symptoms are often
inapparent. In nonpregnant or late-gestational
ewes, the infection can remain latent until the
next conception.1 Chlamydial placentitis begins
around 90 days into gestation, at a moment
coinciding with a period of significant fetal growth, resulting in a diffuse
inflammatory response and placental tissue necrosis. Abortion occurs lateterm, with no other outward symptoms.
Chlamydiosis in small ruminants is also a zoonosis, posing a particular risk
for pregnant women, with documented cases of human placentitis and
abortion. Any source of potential infection must be handled with biosafety
precautions. Human infection response may vary from subclinical through
acute influenza-like symptoms.
Direct diagnosis of an infection relies on a sympathetic history and the
presence of a necrotic placenta containing a large quantity of the agent.
Indirect serological testing is faster and more accessible, and antibodies
can be detected in serum in the last month of gestation and following an
abortion or a suspicious birth for up to 3 months.2
IDEXX Laboratories offers the IDEXX Chlamydiosis Total Ab Test,
an indirect enzyme-linked immunoassay (ELISA) for the detection of
antibodies against C. abortus in serum and plasma of ruminants. The test
contains two plates (strips), offers results in just 2.5 hours, and is adapted
to automation technologies.
Indirect serological testing is faster and more accessible, and
antibodies can be detected in serum in the last month of gestation
and following an abortion or a suspicious birth for up to 3 months.
Chlamydia Classification: This diagram demonstrates the differences between the new and old classification of the order
Chlamydales, showing the new species classification Chlamydophila abortus
Order
Family
Genus
Species
Chlamydophila
Chlamydiaceae
Chlamydophila
Chlamydiales
Chlamydia
Parachlamydiaceae
C. abortus
C. psittaci
C. felis
C. caviae
C. pecorum
C. pneumoniae
Mammals
BIrds
Cats
Guinea pig
Mammals
Humans
Chlamydia
C. trachomatis
C. suis
C. muridarum
Humans
Swine
Mice, Hamsters
N. hartmanellae
P. acanthamoebae
W. chondrophila
S. negevensis
Waddliaceae
Simkaniaceae
Typical Host
Chlamydia psittaci
C. pecorum
C. pneumoniae
C. trachomatis
Chlamydiales
Chlamydiaceae
Chlamydia
Hartmanella
Old Classification
New Classification
IDEXX Chlamydiosis Total Ab Test performance on 81 caprine samples
Number of Samples
IDEXX Chlamydiosis
Total Ab Test
Three naturally infected herds
20
19 (95%) positive
One experimentally infected herd
19
17 (89%) positive
Two confirmed negative herds
42
42 (100%) negative
The table shows the high specificity and sensitivity of the IDEXX Chlamydiosis Total Ab Test for 81
goat samples across 6 herds from France.3
The IDEXX Chlamydiosis Total Ab Test demonstrated 100% specificity
and 89% to 95% sensitivity in a trial of 81 caprine samples across three
naturally infected herds, one experimentally infected herd, and two
known negative herds. For bovine herds, research has found the IDEXX
Chlamydiosis Total Ab Test to be more sensitive than the complement
fixation test (CFT).3
Neosporosis
Neospora caninum is a protozoal parasite
that causes neosporosis, a major source of
infectious abortion in cattle. This apicomplexan
species is morphologically similar to
Toxoplasma gondii, with dogs serving as the
definitive host. Intermediate hosts susceptible
to infection include cattle, sheep, goats, dogs,
horses, and deer.
The primary clinical features are abortion and
newborn illness or death. Seropositive cattle
will continue to have elevated abortion rates in
future pregnancies and an overall decreased
milk production. Primary transmission is through
congenital infections, the spread of N. caninum
oocysts in dog feces, and vertically from cow
to calf. Offspring exposed in utero can be
born healthy, yet be chronically infected. If
bred, these offspring may initiate seropositive
pedigrees, significantly affecting reproduction
and milk production rates of the herd.
Sensitivity: The IDEXX Neospora Ab Test
detected 96.6% of bovine infections in 89 positive
samples from Germany, France, and Hungary.4
Direct diagnosis of neosporosis is possible through a histological
examination or by testing aborted fetal tissue for N. caninum organisms
using either an immunofluorescence assay (IFA) or a polymerase chain
reaction (PCR) test. Indirect diagnosis can be performed on cows using
an indirect IFA or an ELISA.
All cows that have aborted should be screened by serological assay,
and confirmed by a direct assay on fetal tissue or by performing a
histopathology analysis. If any cow is positive, the entire herd should be
screened for N. caninum antibodies.
Current ELISA technology expedites and automates the process of herd
screening, without compromising quality. IDEXX Neospora Ab Test,
offers rapid detection of antibodies against N. caninum in samples of
bovine, ovine, and caprine serum and plasma. A recent trial of the IDEXX
Neospora Ab Test demonstrated nearly 100% specificity and over 96%
sensitivity in determining the serological status of ruminants from several
regions across Europe.
Specificity: The IDEXX Neospora Ab Test demonstrated excellent
specificity in 964 negative cattle, goat and sheep samples from different
regions of Europe.4
Positive bovine samples, goats n = 89
10
Negatives
9
–
8
Positives
–/+
Norway
bovine, n=145
+
Frequency
3
Germany
bovine, n=268
France
caprine, n=42
Switzerland
ovine, n=418
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
OD
0.070
0.016
0.109
0.025
0.090
0.022
0.085
0.064
0.072
0.024
0.072
0.054
%
0.8
1.8
4.0
2.5
2.0
2.3
1.1
6.5
-0.5
2.1
0.1
4.6
5
4
Switzerland
bovine, n=35
Mean
7
6
France
bovine, n=56
Spec.
100.0%
100.0%
100.0%
100.0%
100.0%
99.5%
2
1
15
0
13
0
14
0
11
0
12
0
90
10
0
80
60
70
50
30
40
20
0
10
–1
0
0
% Classes
Life cycle of Neospora caninum
Ingestion of infected tissue
(e.g., fetus, placenta) may cause
dogs to shed Neospora caninum
oocysts in their feces. These
oocysts are very resistant and
may survive up to weeks and/or
months in the environment.
Newly infected cow
Cattle may become infected by
ingesting Neospora caninum oocysts.
Infection during pregnancy
If these calves survive, they are
considered to be chronically infected.
Oocyst shedding
Oocyst
shedding
.
Abortion
Abortion
Chronically N. caninum-infected cows
exhibit an abortion rate two to three
times higher than uninfected cows.
Chronically
infected
healthy calf
N. caninum infection in cows
may cause abortion, stillbirth,
weak calves and a decrease in
milk production.
Breeding cow
If these infected cattle
are used for breeding
purposes, vertical
transmission of the
infection from cow
to calf may occur
In breeding herd
operations, chronically
infected pedigrees
could result from
this cycle.
Q Fever
Q Fever affects cattle, sheep, goats, domestic
pets, and various wild animals, and is among
the most hazardous to humans of cattleborne diseases, with human epidemics and
laboratory infections being common. Coxiella
burnetii—the small, intracellular bacterium that
causes Q Fever—was formerly classified in the
Rickettsiaceae family. However, phylogenetic
investigation has shown C. burnetii to be distant
from the Rickettsia genus, and it has since been
reclassified into the Coxiellaceae family in the
order of Legionellales. C. burnetii is distinguished
from rickettsiae in that this pleomorphic
bacterium produces a small, dense, highly
resistant sporelike form significant to its infectious
and hardy characteristics.
Parallel comparison of IDEXX Q Fever Ab
Test and CF Test on 81 caprine samples.
Sensitivity
(Infected herd. Total of 16 animals):
IDEXX Q Fever Ab Test
16/16
100%
CF
15/16
93%
IDEXX Q Fever Ab Test
21/21
100%
CF
21/21
100%
IDEXX Q Fever Ab Test
44/44
100%
CF
44/44
100%
(Experimentally infected herd. Total of 21 animals):
Specificity
(3 negative herds. Total of 44 animals):
Overall correlation between both methods:
c = [(36+44)/81]*100 = 98%
The IDEXX Q Fever Ab Test correlates very
well with the complement fixation test in a
trial of 81 samples from six goat herds. 3
CF +
CF –
+
–
36
0
26
1
44
45
37
44
81
C. burnetii aerosolizes on particles easily, is resistant to heat, drying,
and many disinfectants, and requires only a few organisms to induce
disease in susceptible animals. Infection may result from inhaling airborne
contaminant, contact with infected animals and their reproductive tissues,
and through vertical and sexual transmission. C. burnetii is excreted in
massive amounts in lochia, placentas and other birthing matter, as well
as in milk, urine, feces, and possibly blood. Ticks may also transmit the
bacteria. As a result of its durability, ease of transmission, and risk to
humans, C. burnetii is listed as an OIE Containment Group 3 pathogen and
is considered a potential bioterrorism threat.
Monitoring, biosafety protocols, and prevention techniques are
critical to protecting herds and humans from C. burnetii exposure.
In ruminants and other animals, Q Fever often has few outward symptoms
until late-term abortions occur without warning, either sporadically or as
part of a rare epidemic outbreak. C. burnetii infections persist for years, and
may be lifelong. Additional symptoms may include the birth of dead or weak
offspring, retained placenta, metritis, and infertility.
All late abortions in ruminants should be investigated for Q Fever,
with care to protect human and other animal health. The IDEXX Q
Fever Ab Test Test has shown great suitability to assess this.
Pregnant women are at particular risk, for whom infection may cause
placentitis, which can lead to premature birth, growth restriction,
spontaneous abortion, or fetal death.
For direct diagnosis of C. burnetii, samples can come from the placenta,
vaginal discharge, aborted fetal tissue (liver, lung or stomach), milk,
colostrum, or feces. Indirect serological assays are often used for individual
diagnosis and herd screening, including IFA, CFT, and ELISA. Because of
their ease of use, reliability, and scalability, ELISA test kits have become the
choice tool for veterinary diagnosis and large-scale routine herd monitoring.
The IDEXX Q Fever Ab Test, available from IDEXX Laboratories, has shown
excellent specificity and high sensitivity consistently competitive with the
complement fixation test.
Monitoring, biosafety protocols and prevention techniques are critical to
protecting herds and humans from C. burnetii exposure. All late abortions
in ruminants should be investigated for Q Fever, with care to protect human
and other animal health. If seropositive animals are found: 1) ensure all milk
is properly pasteurized; 2) disinfect animal facilities regularly, especially
parturition areas, with a 10% bleach solution; 3) keep pregnant animals
in separate pens; 4) always quickly remove all birthing matter, including
aborted fetuses and dispose of properly to prevent contact with domestic
animals or wildlife; and 5) keep manure from infected herds away from
gardens and populated areas. To reduce risk of herd exposure to Q Fever,
minimize introduction of new animals, regrouping of herds, and exposure to
ticks and wildlife.2
Toxoplasmosis
The intestinal coccidium Toxoplasma gondii is
a significant cause of abortion and the birth of
weak offspring among sheep and goats infected
during pregnancy. The female usually has no
symptoms. Early-term infections can result in fetal
death and resorption, causing the appearance of
infertility. Infection mid-pregnancy can produce
weak or stillborn offspring, often accompanied by
a mummified fetus. Late-term infections produce
infected but clinically normal offspring. Future
pregnancies are not impacted by a past infection.
Cats are the definitive host for the sexual
phase of the T. gondii life cycle, and most
warm-blooded animals, including humans,
can serve as intermediate hosts for the asexual
phase. Cats may become infected by eating
intermediate hosts such as rodents. T. gondii
oocysts are shed in cat feces for several days
after infection; these oocysts release infectious
spores into the environment for one to five days.
Sporulated oocysts are highly resistant and may
remain infective in the environment for a year
or more. The most likely sources of human and
animal infection is through consuming raw or
undercooked meat containing live T. gondii tissue
cysts, or from exposure to oocysts in cat feces.
Direct diagnosis of T. gondii presence in tissue is difficult and
expensive. The ELISA as an indirect serological test is well suited to
diagnostics in herds and offers automated interpretation.
Toxoplasmosis is widespread in human populations, with about 30% of
the population having had a past exposure. While most healthy people will
experience no symptoms from an initial infection, very young, elderly, or
immunosuppressed individuals may become ill. In particular, this zoonosis
is a threat to pregnant women and fetal health, and in this aspect especially,
represents a significant public health concern.2
T. gondii should be suspected whenever late abortion occurs in ruminants,
especially when tiny (2–3 mm) white necrotic spots are visible on the
cotyledons, with little or no accompanying inflammation. Direct diagnosis
of T. gondii presence in tissue is difficult and expensive. A wide variety of
indirect serological tests are available, including the dye test, IFA, direct
agglutination test (DAT), and ELISA. The dye test uses live tachyzoites, so
may pose a laboratory risk. The ELISA is well suited to diagnostics in herds
and offers automated interpretation. IDEXX Laboratories offers the IDEXX
Toxotest Ab Test for testing the serum or plasma of ruminants, as part of its
broad line of abortive disease diagnostic kits. The test features two plates
(strips) and gives rapid, highly sensitive results, all in a format identical to
other IDEXX abortive disease assay tests presented in this article.
Abortive Disease
Conclusion
Reproductive losses in a herd can be huge. Fetal resorption or undefined
infertility often remain undetected. Routine monitoring of herds for exposure,
controlling the introduction of potential agent carriers, appropriate biosafety
procedures, and vaccination where possible are together the best security
against reproductive diseases. Developing a systematic approach to
disease monitoring and control by using appropriate, fast, and reliable
diagnostic tests such as ELISAs can make the work easier to manage and
more affordable in the long-term.
Four diseases, Chlamydia, Neospora, Q Fever and Toxotest, one
protocol: IDEXX ELISA abortive disease tests offer matching formats
to make testing easier.
• Rapid turnaround and reliable results
• Common incubation times
• Ready-to-use conjugates
• Read at 450 nm
• Two plate kits with strip plates for small series
• Adapted to automation
References
1. Terrestrial animal health code 2006. 15th ed. OIE: Paris; 2006. Available at:
http://www.oie.int/eng/normes/mcode/en_sommaire.htm. Accessed July 18, 2007.
2. M
anual of diagnostic tests and vaccines for terrestrial animals 2004. 5th ed. OIE: Paris; 2004.
Available at: http://www.oie.int/eng/normes/mmanual/A_summry.htm. Accessed July 18, 2007.
3. Schalch L, Russo P, De Sa C, Reynaud A, Bommeli W. Combined testing of ruminant serum samples for Chlamydia
psittaci and Coxiella burnetii specific antibodies by ELISA. Proceedings from: VIth Congress FeMeSPRum; May 14–16,
1998; Postojna, Slovenia; 514–18.
4. S
pecificity and sensitivity studies for IDEXX Neospora Ab Test conducted by IDEXX Switzerland, January/February 2007.
Data on file with IDEXX Laboratories, Inc.
For more information about Abortive Disease, please contact
your IDEXX representative or visit idexx.com/ruminants.
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