February 2007 Issue
Actinobacillus pleuropneumoniae (APP):
A contagious economic threat
Absent treatment, the disease progresses very rapidly and death can occur within a few hours.
What is APP?
APP is the causative agent of the contagious swine pleuropneumonia. In its acute form, animals exhibit dyspnea, coughing, anorexia, depression, fever and occasionally vomiting. Absent treatment, the disease progresses very rapidly and death can occur within a few hours. Chronic infections cause coughing and pleuritis.
Four RTX toxins, ApxI, ApxII, ApxIII and ApxIV, play a predominant role in the pathogenicity of APP. While most toxins appear in many of the serological responses induced after infection, only ApxIV appears in all of the more than 15 serotypes of APP.
IDEXX has developed a new test that detects antibodies solely for the ApxIV toxin, the only common toxin to all the APP serotypes.
Some serological tests claim to detect antibodies against all serotypes. However, false positive results for APP often occur with these tests due to cross-reacting antibodies for other bacteria harbored by the animal. IDEXX has developed a new test that detects antibodies solely for the ApxIV toxin, the only common toxin to all the APP serotypes. This test, CHEKIT* APP-ApxIV* ELISA, provides a reliable tool to monitor swine for this serious disease.
The Economic Impact of APP
APP can spread rapidly among hogs in crowded conditions with potentially devastating results. When hogs infected with APP and other infections such as PRRS, Aujeszky's disease, mycoplasma, etc., are mixed in a herd in a stressful environment, severe clinical signs appear quickly.
Piglets are at risk as they lose their maternal-derived antibodies at approximately 8-12 weeks of age.
It is important to both monitor a herd for infection with APP and to determine when to vaccinate piglets for optimum protection. CHEKIT* APP-ApxIV serves both of these functions.
Monitoring Herds and Controlling the Disease
One current serological test for APP detects antibodies against the ApxII, a toxin produced by all APP serotypes except serotype 10 and 14. Unfortunately, other bacterial species, such as Actinobacillus suis, produce a similar toxin that cross-reacts with this test, diminishing its reliability.
IDEXX CHEKIT* APP-ApxIV reacts only with the ApxIV toxin, with a specificity of 99-100%. Monitoring with CHEKIT* APP-ApxIV determines the herd epidemiological status for all serotypes of APP.
Non-pathogenic Actinobacillus isolates were evaluated with the CHEKIT* APP-ApxIV kit. Two new non-pathogenic Actinobacillus isolates (0347 and 9953L55) were recently isolated from pigs with no signs of pleuropneumonia. The strain 9953L55 resulted in false positive results in a conventional lipopolysaccharide based assay (Gottschalk et al., 2003). These two atypical strains have all phenotypic characteristics of APP and were initially antigenically and biochemically identified as APP. However, phylogenetic analyses showed that although the strains were genetically similar to APP, they were in fact a new bacterial species (A. porcitonsillarum). Animals experimentally infected with each of these strains showed no clinical signs, macroscopic or microscopic lesions. CHEKIT* APP-ApxIV was used to test samples collected on day 55 d.p.i. from the four animals infected with strain 9953L55 (A. porcitonsillarum). All four sera scored clearly negative. Data of confirmed APP negative (n=134) and experimentally APP infected animals with three different serotypes (APP/6, APP/7, APP/10 collected + 30 d.p.i.) are shown on the same graph.
Vaccination is the best lifetime prevention for APP. It is important to vaccinate piglets at the proper time to avoid vaccine ineffectiveness, thus requiring expensive revaccination. Maternal derived antibodies (MDA) in piglets cross-react with vaccines. A study on two different herds in Hungary helped determine a good target age for vaccination. The first herd had 2,300 sows and the second, 1,000 sows. Both farms applied the farrow to finish system where the growers were transferred to fattening houses at 90 days of age. Severe APP problems were identified in the finisher phase in both herds. CHEKIT* APP-ApxIV was used to analyze the same number of samples collected from piglets from age one week in the first herd and age six weeks in the second.
In both herds, the CHEKIT* APP-ApxIV test confirmed that between ages eight and twelve weeks, maternal derived antibodies reduce constantly.
Blood samples were drawn every two weeks. In both herds, the CHEKIT* APP-ApxIV test confirmed that between ages eight and twelve weeks, maternal derived antibodies reduce constantly. This targeted an appropriate age range for ideal vaccination time. To ensure differentiation of vaccinated from infected animals, use a subunit vaccine based on the outer membrane protein and three of the toxoids produced by APP, ApxI, ApxII and ApxIII. Antibodies to ApxIV will not be produced by the animal’s immune system and CHEKIT* APP-ApxIV* ELISA can be used with confidence to screen vaccinated (ApxIV-negative) pigs from infected (ApxIV-positive) animals.
Bovine Brucellosis
Disease
Bovine brucellosis is usually caused by Brucella abortus, less frequently by B. melitensis and rarely by B. suis. Both of the B. abortus and B. melitensis strains are readily transmissible to humans as undulant or Malta fevers. In cows, brucellosis causes abortion with bacteria in uterine discharges and milk, orchitis, infertility and arthropathy.
Diagnosis
There are a number of screening tests used to detect and monitor herds for brucellosis. Among these, the ELISA tests are the most robust and technically simple.
IDEXX has modern ELISA test kits for both serum and milk. The IDEXX CHEKIT* Brucellose Serum and CHEKIT* Brucellose Milk are fast, reliable, easy-to-use kits with very high specificity and excellent sensitivity. Both tests allow short and overnight incubation, identical incubation conditions for samples and conjugate, use RFU reagents and are 10-plate monophasic kits. Adapted for automation and use with xChek* software, they save time and money.
CHEKIT* Brucellose Serum and CHEKIT* Brucellose Milk are two of the many innovative products that consistently meet the requirements of IDEXX customers.
IDEXX CHEKIT* APP-ApxIV
Actinobacillus pleuropneumoniae (APP), the causative agent of the contagious swine disease, can infect entire herds resulting in severe economic loss.
IDEXX CHEKIT* APP-ApxIV is the only serological test for APP that covers all of the multiple serotypes of this disease without false positive results from cross reaction of other bacteria. By screening for the ApxIV toxin, the only one that is common to all serotypes of the disease, CHEKIT* APP-ApxIV provides a reliable method to monitor swine herds for this serious disease.
IDEXX CHEKIT* APP-ApxIV is the only serological test for APP that covers all of the multiple serotypes of this disease without false positive results from cross reaction of other bacteria.
Use CHEKIT* APP-ApxIV to determine when to vaccinate piglets. Between eight to twelve weeks of age, piglets lose the maternal derived antibodies (MDA) to ApxIV. Monitoring piglets with CHEKIT* APP-ApxIV, shows when the MDA have waned and indicates the optimum time to vaccinate. Vaccines with outer membrane protein and three toxoids (ApxI, ApxII and ApxIII) will provide lifetime protection against APP for piglets. As well, the absence of ApxIV antibodies will allow differentiation between vaccinated and infected animals in any subsequent herd screening with CHEKIT* APP-ApxIV.
Unique characteristics of IDEXX CHEKIT* APP-ApxIV:
- Specificity of 99–100%
- Sensitivity of 95–100%
- Unique serological screening method covering all serotypes
- No cross reaction with other bacteria
- Differentiation between vaccinated and infected animals
- Monophasic assay, no duplicate testing needed
- Time saving protocol (results available after ±3 hours)
- Test kit including stripped microtiter plates
Total Counts Report
xChek* is capable of producing a large number of reports, including the Total Counts Report. The Total Counts Report gives you the number of negative, positive, suspect and total number of samples for each case selected. It also gives you a grand total for each category for all of the cases selected. When creating the report, you can select the assay as well as the date range. The Total Counts Report allows a variety of uses. You may want to use it to determine a percentage of positive samples when testing presumed negative flocks or herds. You can also use the report to determine monthly or quarterly tallies for testing in your lab.
To create the Total Counts Report choose Reports > Total Counts from the menu bar. In the Total Counts dialog box, choose the assay and the data range (or leave the date range open to select all cases). You can also select the spreadsheet option if you want to save the data as a Microsoft® Excel spreadsheet.
Events Around the World
- Orlando, Florida USA—March 3–6, 2007
American Association of Swine Veterinarians (AASV)
- Stendal, Germany—March 7–9, 2007
BHV1-BVD-MPT-Meeting – International
- St. Paul, Minnesota USA—March 13–15, 2007
Midwest Poultry Federation (MPF)
- Fort Worth, Texas USA—March 23–26, 2007
Texas and Southwestern Cattle Raisers Association (TSCRA)
- Las Vegas, Nevada USA—March 26–29, 2007
Western Poultry Disease Conference (WPDC)
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