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
| |
Chlamydophila
psittaci |
Polyomavirus |
PBFD virus |
Pacheco's Disease virus |
Total |
Positive |
Total |
Positive |
Total |
Positive |
Total |
Positive |
| African Grey species |
493 |
61 |
307 |
4 |
436 |
38 |
291 |
6 |
| Amazon species |
492 |
38 |
250 |
8 |
132 |
6 |
278 |
13 |
| Budgie species |
233 |
55 |
29 |
4 |
29 |
6 |
45 |
8 |
| Caique species |
39 |
6 |
16 |
2 |
16 |
0 |
20 |
0 |
| Cockatiel species |
583 |
78 |
151 |
19 |
108 |
2 |
84 |
7 |
| Cockatoo species |
326 |
45 |
220 |
9 |
276 |
11 |
198 |
6 |
| Conure species |
426 |
41 |
271 |
11 |
295 |
15 |
252 |
5 |
| Finch species |
32 |
12 |
0 |
0 |
0 |
0 |
0 |
0 |
| Lory species |
191 |
11 |
94 |
2 |
119 |
2 |
99 |
0 |
| Lovebird species |
284 |
32 |
186 |
19 |
163 |
25 |
119 |
0 |
| Macaw species |
464 |
47 |
326 |
13 |
291 |
4 |
374 |
26 |
| Parakeet species |
187 |
39 |
95 |
15 |
108 |
8 |
68 |
4 |
| Parrot, Eclectus |
92 |
6 |
72 |
5 |
78 |
6 |
74 |
2 |
| Parrot, Jardine's |
21 |
1 |
13 |
1 |
71 |
0 |
15 |
0 |
| Parrot, Meyer's |
44 |
2 |
22 |
7 |
28 |
0 |
23 |
0 |
| Parrot, Senegal |
254 |
18 |
236 |
25 |
245 |
29 |
292 |
4 |
| Pionus species |
109 |
11 |
66 |
2 |
91 |
0 |
81 |
8 |
| TOTAL TESTS: |
4267 |
503 |
2354 |
146 |
2486 |
151 |
2313 |
89 |
| % of Positive Tests: |
11.8% |
6.2% |
6.0% |
3.8% |
The following avian DNA tests are
available from HealthGene:
(Avian
Polyomavirus, PBFD virus, Pacheco’s Disease virus,
Chlamydophila psittaci);
(Aspergillus spp., Chlamydophila psittaci,
Cryptosporidium spp., Avian tuberculosis, Toxoplasma
gondii, Trichomonas gallinae);
