Mycoplasma Infections in Turkeys
By Ephraim Keren, VMD, IC News Editor
Mycoplasma infections have been a significant cause of economic losses in the poultry industry, worldwide.
As with other infectious diseases, vaccination and treatment have traditionally been regarded as bulwarks to mycoplasma control. More recently, turkey raisers have come to recognize that keeping mycoplasma away from their flocks is more cost effective.
Biosecurity measures such as strict hygienic protocols regarding personnel and equipment are practiced in these operations. These practices are supported by routine serologic surveillance to confirm that the birds are mycoplasma free and/or to detect infection earlier.
The ImmunoComb® Antibody Test Kit for MG-MS-MM is specifically designed for confirming mycoplasma infection in turkeys. When positive results are detected by other screening tests, such as HI, these samples should be retested by the ImmunoComb® dot-ELISA, which is a more specific technique. This approach supports good management programs by confirming mycoplasma-free status of flocks and provides early detection to minimize damages if and when infections do occur.
Three mycoplasmas have historically been associated with problems in turkeys. They are briefly reviewed below.
Mycoplasma gallisepticum (MG) is a primary cause of respiratory disease, but may also lead to secondary infection with other mycoplasmas and bacteria, such as E. coli. Loss of production and down-grading at processing is often seen due to air sac disease.
Following its introduction into the flock, MG often persists as a subclinical infection. An outbreak of clinical disease may result when a large number of birds become infected, or other diseases or stress factors are present. MG may be transmitted directly via the aerosol route as well as by contaminated dust and feathers. Vertical (egg) transmission is also considered to be an important mode of transmission.
Mycoplasma synoviae (MS) is usually associated with subclinical upper respiratory infections of turkeys, which may become more severe when combined with viral and bacterial infections. Systemic infection often causes inflammation of the synovial membranes, predominantly those of the tendons of the legs, leading to ’infectious synovitis’. Poor growth or precipitation of air sac disease and leg problems with significant mortality may also be observed. Lateral infection (via direct contact with the respiratory tract) and vertical transmission both play a major role in spread of MG infection in chickens and turkeys.
Mycoplasma meleagridis (MM) infection in turkeys is associated with respiratory disease, skeletal abnormalities, poor growth, and reduced hatchability in breeders. Infection may be silent or severe, especially in the presence of other infections or environmental problems.
MM is predominantly transmitted vertically from parent stock and persists in the oviduct more than MG or MS. Infection is also spread via contact with infected birds or contaminated equipment.
Q Fever: An Overview
By Ephraim Keren, VMD
Q fever is a zoonotic disease caused by bacteria, Coxiella burnetii. Cattle, sheep and goats are the primary reservoirs of C. burnetii, however, the infection is recognized in many other animals. Infections are often inapparent, both in animals and humans.
Abortion in apparently healthy goats and sheep has been linked to infection by C. burnetii. Infected animals may shed high numbers of organisms in the aborted tissues and fluids as well as in milk, urine and feces. The organisms can survive in the environment for long periods as they are resistant to heat, drying and many common disinfectants.
Infection in humans usually occurs by inhalation of airborne organisms in contaminated barnyard dust. Ingestion of contaminated milk or food and tick bites are less common modes of transmission of Q fever. Clinical illness, is characterized by fever, headaches, GI signs and pneumonia. If left untreated, a chronic disease leading to endocarditis and death may result.
Diagnosis
Q fever serology is the preferred diagnostic method over other laboratory techniques (e.g. bacterial isolation, PCR and immunohistochemistry). Several procedures have been used to measure antibodies to Coxiella burnetii antigens: indirect ImmunoFluorescence Assay (IFA), Complement Fixation (CF) and ELISA. IFA (regarded as the reference) and ELISA have been found to be as specific and more sensitive than CF.
Coxiella burnetii exists in two antigenic phases (I and II). This phenomenon is noteworthy for diagnosing Q fever disease. In the acute stage of illness, antibody levels to phase II appear earlier and are greater than to phase I. Antibodies to phase I antigens of C. burnetii take longer to appear and indicate chronic exposure to the bacteria. Antibodies to phase I and II antigens have been known to persist for months or years after initial infection.
Biogal’s Dot-ELISA ImmunoComb® kit for sheep employs the phase II strain of C. burnetii. As such, the kit is suitable for detecting antibodies in both acute and chronic stages of the disease.
Prevention and Control
Q fever is an insidious animal disease with worldwide public health importance. Routine testing of livestock for antibodies to C. burnetii should be practiced in order to identify infected animals. Additional measures should be taken to prevent exposure of people to potential sources of infection, namely the environment and by-products of these animals.
References
1) www.cdc.gov/ncidod/dvrd/qfever/IFA
2) Raoult, D. & Marrie, T. (1995). Q Fever. Clinical Infectious Diseases, 20, 489-496.
Clinical Study: ImmunoComb® Parvo IgM & IgG Kits Prove Valuable
By Ephraim Keren, VMD
A recently published study concluded that Biogal’s dot-ELISA ImmunoComb® test was a reliable method for confirming the diagnosis of parvovirus (CPV-2) infection in acutely ill dogs(1).
Case selection
Twenty-five dogs were selected for this study based upon the following criteria:
1. No previous vaccination for canine parvovirus (or distemper),
2. Compatible clinical symptoms (e.g., fever, diarrhea, vomiting),
3. Leucopenia (WBC ≤ 5,500 l/µl),
4. A positive antibody titer to CPV (≥ 1:80) by HAI*.
Upon presentation, a fecal-sample from each dog was checked for CPV antigen using a commercial immunochromotographic assay.
Results
Significant levels of IgM and IgG serum antibodies (≥S3) were found in all 25 dogs in this study, while only 5 dogs (20%) had CPV antigen detected on their feces. The authors noted that the IgM titers of the naturally infected dogs in this study were quantitatively higher than IgM levels found in healthy dogs following vaccination, as described in an earlier study.
Editor’s Comment
This study provides “food for thought” for veterinarians, who might rule out a diagnosis of canine parvovirus in clinical cases without considering serologic data. In 80% of the clinical cases of CPV reported here, serology proved to be a more reliable diagnostic parameter than the fecal antigen test.
(1) Waner, T., et. al. (2004). Diagnosis of acute Parvovirus infection (CPV-2) in naturally infected dogs using serum IgM and IgG rapid dot ELISA. IJVM. 59 (1-2), 12-15.
* HAI tests were performed by the Cornell Diagnostic Laboratory (Ithaca, N.Y.).
From the Editor: To Revaccinate or Not?
By Ephraim Keren, VMD
This past summer, I met with a friend and colleague of mine from the U.S. while he was visiting Israel. He informed me that he recently sold his clinic, but continued to see small animals on a ’house-call’ basis. While discussing his interest in holistic medicine, he told me that he advocates vaccinating puppies one-time against canine Distemper and Parvovirus. When I questioned this recommendation, he simply replied that he advises his clients to test their dogs’ antibody levels if they have any doubt whether or not a revaccination is required.
The subject of “over-vaccinating” of pets has gained momentum during the past several years. As more veterinarians and pet owners have started asking about the duration of immunity following vaccination, the veterinary industry and research community have responded. For example, a multivalent (Distemper – Parvovirus) vaccination with a 3-year label for duration of immunity is now available in the U.S.
In a recent publication, investigators reported on dogs that were protected against disease (by virus challenge) four years after being vaccinated with a commercially available multivalent vaccine(1). The work demonstrated a highly significant association between the presence of specific antibodies in the animals and protection against viral challenge. All vaccinated dogs that mounted an antibody response were protected. All of the unvaccinated controls and one “non-responder” developed clinical disease follow challenge.
These findings are probably not surprising to most of our readers and/or ImmunoComb® test users. They are certainly consistent with my colleague’s advice to his clients who ask about when to revaccinate their pets. Namely, if specific antibodies are present, the dog does not need to be revaccinated.
For those veterinarians who might be considering a more ’holistic’ approach to vaccinations, I would like to point out that the puppies in this work were confirmed to be sero-negative for antibodies vs. canine Distemper and Parvovirus before the first vaccination (out of 2) was administered at 7 to 8 weeks of age. As such, the issue of potential interference of immunization in pups by the presence of maternal antibodies was not addressed.
(1) Abdelmagid, O. Y., et al. (2004). Evaluation of the efficacy and duration of immunity of a canine combination vaccine against virulent Parvovirus, Infectious canine Hepatitis virus, and Distemper virus experimental challenges. Veterinary Therapeutic, 5(3), 173-186. (Research funded by Schering-Plough Animal Health.)
Vet Forum: Serology in Poultry
By Ephraim Keren, VMD
Question:
How valuable is one serologic test (’flock profile’) for determining the flock’s immunity to a specific disease?
Answer:
Assessing a single serologic profile of a flock is like a ’still frame’ snapshot. The presence of antibodies to a particular antigen (i.e. virus) indicates that the birds have mounted an immune response to the agent either by infection or vaccination. However, one test will not tell you the about the biologic dynamics of immunity which is more comparable to a ’motion picture.’ Therefore, most veterinarians prefer repeated testing rather than a single test in order to better assess the health and immune status of a flock.
It is important to establish a ’baseline’ antibody profile, which can then be used for comparison with future tests. In monitoring a vaccination program for example, it would be helpful to look at antibody levels (in a statistically significant number of birds) in the flock both before and after vaccination.
The pre-vaccination tests will give information to help determine when and if the birds should probably be vaccinated. The post-vaccination test will assess whether or not the birds exhibited a humoral immunologic response (i.e. a rise in antibody titer) to the vaccination and if the birds are ’protected’.
I would like to thank Dr. Marigold Manalo for her question to the Vet Forum. Dr. Manalo was the veterinary consultant for Glenwood Technologies International, Inc., in the Philippines. She also has a small animal practice.