Tuberculosis in Birds: Insights into the Mycobacterium avium Infections

Table 2

Diagnostic methods and tests used in birds [2, 3, 5, 23, 43–47].

Type of test	Performed in	Time required	Merits	Demerits
Observing gross lesions	Dead birds	1 hour	Easy diagnosis	Only presumptive diagnosis
Acid fast staining	Dead birds	1 hour	Easy definitive diagnosis	Less sensitive, Not able to distinguish amongst species
Isolation/Culture	Dead birds	About 4 weeks	Definitive diagnosis	Time consuming
Tuberculin test	Live birds	48 hours	Easy to perform; Definitive diagnosis	Time consuming, Test is not very sensitive, Possibility of false positive and false negative results
Agglutination test	Live birds	Few minutes	Can differentiate serotypes. Useful for screening large flocks for immediate culling	Occasionally false positive reactionsNot reliable in caged birds
ELISA	Live birds	2 hours	Definitive diagnosis; Can be used for exotic and pet birds	Less specific than tuberculin test; False positives may be there
DNA probes	Bacterial cultures	4–6 hours	Highly sensitive and specific	Probe may react with isolates that genetically or biochemically do not fit within the MAC
PCR	Dead/live birds/cultures	4 hours	Highly sensitive and specific	Requires specialized laboratory and trained personnel
RFLP	Bacterial cultures, clinical samples	1 day	Differentiates mycobacteria to the species level Discriminative for the analysis of strain relatedness	Insufficient quantities of gene makes visualization of digested fragments difficult
Multiplex PCR	Bacterial cultures/clinical samples	5–8 hrs	Rapid and inexpensive technique for subspecies identification and differential diagnosis of the MAC complex	Requires specialized laboratory
Sequencing of the 16S rRNA gene	Bacterial cultures	2 days	Powerful technique for differentiating species	Labor-intensive and difficult to implement in routine diagnosis
HPLC	Bacterial cultures	1 day	Can identify Mycobacteriumisolates to the species level	Uses costly equipment and requires substantial amounts of the test organism.
Real-Time PCR	Bacterial cultures/clinical samples	4–6 h	Low risk of sample contaminationOffers the possibility to quantify bacterial load	Sensitivity could be affected by the initial volume of DNA present
MIRU-VNTR/MATR-VNTR typing	Bacterial cultures/clinical samples	1 day	Improves RFLP discrimination Useful for determination of genotypic diversity of M. avium subspecies	Requires specialized laboratory
Pathogenicity tests	Live young birds	5–6 weeks	Likelihood of the etiological agent can be knownUseful in cases where the typing facilities are not available	Time consuming and concerned to ethical issues