What is mycobacterium avium complex?

Mycobacterium avium complex (MAC) is caused by a group of organisms (over 30 serovars) including, Mycobacterium avium. The organisms may cause disease not only in birds, but other warm and cold-blooded vertebrate species. In humans it tends to be an opportunistic infection that is primarily found in immunocompromised individuals. MAC organisms are common in water, water mists or vapors, dust, soil, and bird droppings.

How is MAC spread?

MAC organisms usually enter the body through contaminated food and water however, transmission can also occur through inhalation of infective aerosols. MAC is probably not passed from person to person.

Who is at risk for infection?

MAC occurs most often in people with AIDS and other immunocompromised individuals. Most people who get MAC have fewer than 50 t-cells. MAC almost never occurs in people with over 100 t-cells. People who are anemic (low red blood cells) are also at higher risk for MAC.

Is MAC infection serious?

Infections with Mycobacterium avium (MAC) can lead to disseminated disease including blood infections, hepatitis, skin lesions, and pneumonia.

How can I protect myself?

• Take measures to protect persons at high risk from being infected.
• All persons in contact with infected birds should be informed about the nature of the disease.
• Minimize animal contactÑespecially with birds and bird droppings. Be aware that pigeons, common in most urban areas, can also transmit the organism that causes cryptococcosis, another opportunistic infection that affects immunocompromised individuals.
• Persons at risk should wear protective clothing, gloves, surgical cap and a respirator with an N95 rating or a higher-efficiency respirator when cleaning cages or handling birds. Surgical masks may not be effective in preventing transmission of MAC.
• Practice preventative husbandry.
• Position cages to prevent the transfer of fecal matter feathers and other materials from one cage to another.
• Perform procedures in a laminar flow hood whenever possible

What are the signs of MAC infection?

The most common symptoms of MAC are persistent fevers which may be accompanied by night sweats, weight loss, a loss of appetite, fatigue, or progressively severe diarrhea. Symptoms of early MAC disease often involve the gastrointestinal tract. Painful joints, bone, brain, and skin infections can result from MAC bacteria spreading through the body. Some physical signs of MAC may include swollen or enlarged abdominal lymph nodes, usually on only one side of the body, and an enlarged liver and spleen. Respiratory symptoms (cough and difficulty breathing) are relatively uncommon.

What do I do if an exposure or injury occurs?

Exposure to aerosols, bites or scratches involving animals or injuries from objects contaminated with body fluids from animals require immediate first aid and medical attention. Notify your supervisor! Then, between the hours of 8:00 am and 5:00 pm., call or proceed to Stanford Occupational Health Clinic; 480 Oak Road, Rm B15; 5-5308. After 5:00 pm and before 8:00 am., call or proceed to the Stanford Emergency Room, H126 (in the hospital, next to the cafeteria), 723-2670.

General Questions?
Call the Laboratory Animal Occupational Health Surveillance Program's Health Provider:
Stanford University Occupational Health Center (650) 725-5308
Veterinary Service Center
(650) 723-3876
or Stanford Environmental Health & Safety
(650) 723-0448.

This document provided by:
Laboratory Animal Occupational Health Surveillance Program
Department of Environmental Health and Safety
Stanford University

For more information, or to make comments on this page, please contact the EH&S Biosafety Officer: esegal@stanford.edu

Last modified: Tuesday, April 27, 2010

Helpful websites:
http://www.projectinform.org/info/mac/index.shtml
http://www.atdn.org/simple/mac.html
http://www.aidsinfonet.org/fact_sheets/view/514