A Review Of DNA Testing For Avian Infectious Diseases Over The Past Three Years

Many bird owners, breeders, and veterinarians have already discovered the extensive list of avian diagnostic tests offered by HealthGene Laboratory. Bird owners and aviculturalists have realized the benefits of DNA testing since screening all newly acquired birds provides owners with the opportunity to safely and immediately introduce new birds to their collections, while avoiding lengthy quarantine times. As illustrated in table 1, HeathGene conducts testing for common avian pathogens such as Chlamydia psittaci (Chlamydophila psittaci), Avian Polyomavirus, Psittacine Beak and Feather Disease (PBFD) virus, and Pacheco’s Disease virus. However, this list is not exhaustive. Other avian DNA diagnostic tests include Aspergillus spp., Toxoplasma gondii, Avian Paramyxovirus, Avian Tuberculosis and Trichomonas gallinae.

As table 1 illustrates, HealthGene Laboratory is pleased to present a three-year analysis of avian DNA diagnostic testing. This data represents the incidence of positive infection for some of the most notorious avian pathogens known to bird owners and breeders. These numbers denote samples submitted from an array of avian veterinary practitioners and a variety of species, signifying that most pathogenic organisms do not discriminate between species and virtually all birds are susceptible. The test results represent samples from birds displaying clinical symptoms of disease, as well as samples submitted for general screening.

The statistics presented in table 1 are only valuable to breeders and practitioners if they are clinically significant. In order to determine their clinical significance, one must examine the validity of the test underlying the result. To illustrate this idea, let’s look at the test used to identify Chamydia psittaci (Chlamydophila psittaci), as well as the organism itself. Chlamydia psittaci (Psittacosis) is one of the most common bacterial infections among companion birds. Diagnosis can often be a problem due to the fact that Chlamydia resides inside the cells of its host and therefore does not stimulate a high production of antibodies for serological testing. As table 1 illustrates, HealthGene has reported nearly a 12% positive infection rate for Chlamydia using a DNA-based test. These positive results are of clinical significance because this test actually detects the genetic material (DNA) of the pathogenic organism itself, thereby accurately confirming the organism’s presence in the biological sample (ex. blood, feces). DNA by itself (i.e. outside of the pathogens protective coat) cannot survive for prolonged periods of time since it is quickly degraded by the bird’s naturally occurring enzymes. Thus, the detection of a pathogens DNA is a failsafe marker that indicates the presence of the organism itself.

DNA testing has many other advantages over other diagnostic methods. For example, a pathogen can be detected during any stage of infection even if the host is not showing any clinical symptoms of disease. This is a major advantage over most forms of serological testing, which are based on the detection of antibodies and usually require an immune response. In certain cases, a bird’s immune system may be able to overcome or suppress an infection. In this scenario, the bird is considered a carrier of the infection and may actively shed the organism into its environment if exposed to different types of stress. Birds infected with Pacheco’s disease virus can display these symptoms. Pacheco’s disease is caused by a strain of herpesvirus that is dreaded by aviculturalists because of its very devastating and often fatal effects. It was first recognized in Brazil when birds started dying several days after becoming ill. Any bird that survives an outbreak should be considered a “latent” carrier of the virus and may actively shed the virus under different types of stress, thereby perpetuating the infection. As table 1 indicates, our laboratory results show a 3.8 % positive infection rate from the samples submitted.

HealthGene Laboratory would like emphasize that screening all newly acquired birds for the pathogenic organisms mentioned in table 1 should be part of every bird owners standard practice before exposing new birds to their collections. Veterinarians interested in conducting infectious testing should submit 0.2 ml blood samples in EDTA / lavender top tubes. Chloacal swabs, environmental swabs, feces and other samples can be submitted in any sterile container such as a red top tube or urine container. HealthGene Laboratory recommends submitting multiple samples, which significantly increases the effectiveness of the DNA diagnostic test. Please note that there is no extra charge for additional samples from the same animal. Results for infectious testing are typically provided within 2-3 business days following their arrival. HealthGene recommends that certain positive results for infectious agents (ex. Chlamydia psittaci) are resubmitted two weeks following treatment to ensure that treatment was successful.

Table 1. Infectious Avian DNA Testing by Species

The following avian DNA tests are available from HealthGene:

AVP2 - Avian General Profile (Avian Polyomavirus, PBFD virus, Pacheco’s Disease virus, Chlamydophila psittaci);

AHAP1 - Avian Health Awareness Profile (Aspergillus spp., Chlamydophila psittaci, Cryptosporidium spp., Avian tuberculosis, Toxoplasma gondii, Trichomonas gallinae);

A101 - Avian Sexing;
A102 - Avian Fingerprinting (Typing);
A104 - Avian Polyomavirus;
A106 - Chlamydophila psittaci;
A108 - PBFD virus;
A110 - Pacheco’s Disease virus;
A112 - Toxoplasma gondii;
A114 - Trichomonas gallinae;
A116 - Avian Paramyxovirus;
A118 - Avian Tuberculosis;
D329 - Cryptosporidium spp.;
D405 - Giardia spp.;
D409 - Aspergillus spp.;
D411 - West Nile virus;
D417 - Bordetella avium.