A118 - Avian Tuberculosis

Description:

Mycobacterium is a genus comprising morphologically similar, aerobic, non-spore-forming and non-motile bacteria with wide variations in host affinity and pathogenic potential. Mycobacteria are more resistant to heat, pH changes, and routine disinfection than are other pathogenic non-spore-forming bacteria. In total, thirty-two species have been known to cause infection in humans and animals. Avian tuberculosis infection is commonly associated with two strains of mycobacteria, M. avium and M. genavense. M. avium has a wide spectrum of hosts including poultry, pigeons, raptors, ratites, wild birds, psittacines, and passerines. M. genavense commonly infects psittacines, and is occasionally responsible for infection in passerines.
M. avium infections are considered to be "open", meaning infected birds consistently shed large amounts of organism into the environment. M. avium is transmitted by ingestion and inhalation of aerosolized infectious organisms from feces. Incubation in birds can range from weeks to years. Oral ingestion of food and water contaminated with feces is the most common method of infection. Once ingested, the organism spreads throughout the bird's body and is shed in large numbers in the feces. In most cases, a bird infected with tuberculosis will develop symptoms such as progressive weight loss in spite of a good appetite, depression, diarrhea, increased thirst, and respiratory difficulty. Decreased egg production is often observed in birds that were laying eggs
Typically, three categories of infection are observed in birds infected by mycobacteria. The classic form is characterized by the presence of tubercles or granulomas throughout many organs in the body (i.e. liver, spleen lungs). A second observable form, known as paratuberculosis, is associated with lesions in the intestional tract and is often seen in amazons, pionus, and Brotogeris parrots. With this form, high numbers of organisms are shed in the feces. The third form known as nontuberculous, or atypical form, is very difficult to recognize. This form commonly occurs in finches, canaries, and small pisttacines. The liver is usually very enlarged and large numbers of mycobacteria are found in cytology and histopathology.

Diagnosis:

Diagnosis of tuberculosis in live birds is often very difficult. Serological testing and skin tests used to diagnose tuberculosis in humans do not work well in birds. It is sometimes possible to find acid-fast bacteria in the feces. However, this method is not specific because other acid-fast bacteria may also be present. Physical findings, such as a very elevated white blood cell count and low red blood cell count, as well as tests such as radiology (x-rays) and endoscopy can lead to a preliminary diagnosis. Nevertheless, definitive diagnosis is usually based on culturing the organism from the feces or from an organ. This process is labourious and time consuming and frequently requires specialized testing that is beyond the capacity of clinical laboratories. A PCR assay is now available that specifically detects the DNA of M. avium and M. genavense species in a sample. A positive result confirms M. avium or M. genavense infection.

Sample:

1. Whole Blood (0.1-0.3 ml) in a lavender top (EDTA) tube.
2. Feces in a sterile container.

Special Handling:

Store blood and tissue samples at 4°C until pick up or shipment.

Test Code:

A118