Mycobacterium avium

Avian Tuberculosis

• AKA Avian Mycobacteriosis

• M. avium (most common), M. intracellularle, {M. genavense} and others

• MA or MAI complex (MAC, MAIC)= Mycobacterium avium-intracellularle infection in humans or birds

Avian TB

• Pet birds, poultry, captive & free-range wild birds

  • All orders

  • Esp Anseriformes (ducks & geese), Gruiformes (cranes) & Galliformes (chicken-types)

    • In CAPTUVE collections!

• NOT Zoonotic? Shared?

• Young children & immunocompromised adults get it!

  • Probably from environment, not birds

Avian Tb Cont.

• Transmission- thru feces (fecal-oral) or environment

  • fecal-oral → esp. caged birds

• Signs: emaciation, chronic wasting, +/- diarrhea, listlessness (not active), decreased egg production (poultry), swellings around eyes, rarely respiratory signs

• Much more common in adult vs young birds

Role of Stress

• Stress greatly increases susceptibility (rare to see non-stress_

• Types of Stressors:

  • Malnutrition, overcrowding, drought, extreme temperatures, other infections, pinioning (wing tip removal)

    • drought: no water, dehydration, no vegetation

What is a saprophyte?

A. A student who cheats on an exam

B. A pathogenic organism

C. An organism living on dead or decaying organic matter

D. A disease transmissible from people to animals

Sources of MAI complex

• Feces

• Ubiquitous environmental saprophytes (animals that’s dead or rotting)

• Surface water

• Soil

  • Acidic

  • Moist (marshy or prone to flood)

  • High in organic matter (saprophyte)

  • Contaminated with feces

Which came 1st?

• Are wild birds the source or the recipient? don’t know

• Both wild and captive birds may be carriers

  • What is a carrier?

Carrier

• Is infected with the agent, but shows no signs

• Capable of transmitting to others

• Types: True (Latent), Incubatory, Convalescent

  • True: never impacted by agent, infecting others

  • Incubatory: not yet clinically infected until incubation period is over, infecting others

  • Convalescent: recovered, can still pass to others

Importance of Avian TB

• Economic

  • Disease in poultry & caged birds (& swine)

  • Cross reactions in other LS (to TB)

• Loss of free-ranging colonies or species

  • 18,500 flamingos died in 1993 on 2 Kenyan lakes

Cross Reaction

• A type of False Positive reaction on a diagnostic test

• May occur when the animal is exposed to a similar agent, was infected but has eliminated the infection (but retains antibodies), or when they are vaccinated against the agent

  • M. avian, M/ bovis

Ante-mortem (diagnosis, before death)

• VERY difficult, esp in wild birds

• Clinical finding → clues

  • Chronic wasting, death (either after months, or sudden), emaciation, lethargy, poo quality feathers, distended abdomen (liver swelling & fluid build-up), lameness, +/- diarrhea, occular, cutaneous, or subcutaneous granulomas

• Normal carriers → insidious Dz

  • Subtle or sneaky (hidden)

Ante-mortem Dx Cont.

• Captive: intradermal tuberculin test, blood tests, culture (dead animals)

• Wild: none practical (fecal culture?)

  • false negatives

Poster-mortem Dx

• Liver, spleen, intestines (best luck)

  • Many other organs less frequently involved

• Granulomas (nodules), or diffuse inflammation

• Enlargement (liver & spleen)

• Muscular wasting

  • How assess? big, pectorals, keel: strength to flop wings

Definitive Dx

• Necropsy (post-mortem): suggestive

• Microscopic: more specific

  • Acid-fast bacteria (pretty certain)

• Definitive: culture &/or molecular identification of MAI complex bacteria

Treatment

• Rarely works

• Euthanasia to prevent transmission

Control/Prevention

• Captive: ID (intradermal tuberculin test) and remove infected birds, hygiene (remove feces & other contaminated material), avoid overcrowding (minimize stress), supply quality nutrition

  • Prevent contact with wild birds

• Wild: Good Luck!

  • Prevent contact with domestic birds!

Johne’s Disease

• Pronounced “Yo-Knees”

• AKA Paratuberculosis

• Mycobacterium avium subsp. paratuberculosis

• Still considered part of the MAI complex

  • Usually abbrev. “MAP”

Johne’s (MAP)

• Domestic: cattle, sheep, goats, farmed cervids

• Wild: many susceptible species but rare

  • Bovine: bison, bighorn, Mt. goat, etc.

  • Cervids: WTD, MD, elk, Sika etc,

  • Camelids: Camels, llama, alpaca

  • Lagomorphs: rabbits

  • Primates:

Johne’s

• Young animals more susceptible to infection

• Mid-Old age animals more likely to show signs

• Another chronic wasting disease!

  • Can take years!

Why might some people assume Johne’s is a disease of birds?

A. Dr. Johne was a famous ornithologist

B. The species name of the agent implies an avian host

C. The bacteria that causes Johne’s is airborne

D. Johne’s IS a disease of Birds!

Johne’s transmission

• Fecal-oral

  • In utero-BHS

• Environmental contamination occurs

Epidemiologic Triad (decided how severe an outbreak is going to be in a population)

• Host- age, immunocompetence (individual animal)

• Agent- strain virulence, pathogenicity, how it is transmitted, special features (spores)

• Environment- degree of contamination, humidity, exposure to UV (sunlight) (destroys pathogens), stressors affect host

Johne’s 2

• MAP survive in feces, soil & water: 1 year

• Healthy Carriers may shed for years (host)

• More problematic in Intensive LS operations (environmental)

• Eradication nearly impossible, Control in LS very valuable

Johne’s Signs

• Diarrhea

  • intermittent (recover, get again)

• Chronic wasting

  • losing weight over months or years

  • keeping intestine from absorbing nutrients properly

  • animals don’t get enough protein

• Hypoproteinemia → bottle jaw (fluid collected under jaw)

• Abnormal antlers/horns

• Fatal if clinical signs

IS Johne’s Zoonotic?

Does it cause Crohn’s Disease in humans?

• If MAP- Crohn’s more likely

• If Crohn’s, MAP more likely

• Does this prove causation? no, association

• What is the source of MAP?

Johne’s Dx

• Signs & lesions= suggestive (emaciation, Diarrhea, thickened {granulomatous} intestines, colon)

• LS-rectal scraping or biopsy with Acid-Fast bact= presumptive (diagnoses)

• Definitive- culture (feces inc.)

Johne’s Treatment

• None

• Prevent introduction

• Control in LS: Cull animals with signs, manure management, good husbandry

Johne’s control in wildlife

• Most impractical or impossible

• Increasing harvest to reduce density been tried- reduced, but not eliminate

• Do not use for translocations!

Why translocate WL?

Taking WL from one area and moving to another

• reestablish population

• Inc. genetic diversity in big population

• Can also lead to disease transmission

Johne’s in BHS

• CO & WY

  • Behavior facilitates fecal-oral transmission

Point Reye’s National Seashore

• Tule elk infected with MAP

• Clinical Disease rare

• Controversy for Mgmt

Pt. Reyes N.S.- Tomales Point

Wander, proved they had Johne’s disease

Mycobacterium leprae (& less commonly M. lepromatosis)

• Leprosy (human disease)

• Armadillo- only non primate to suffer from it

Leprosy

• Armadillos can transmit it to humans

  • Esp in TX & LA

• Humans probably gave it to armadillos 1st!

  • 400-500 years ago

Leprosy in Humans (Hansen’s Disease)- the extremes

• Tuberculoid leprosy- “Strong Immunity” non-pruritic rash (rash that doesn’t itch), mild peripheral nerve damage (numbness). Few bacteria (grow to have strong immunity)

• Lepromatous leprosy: “Weak Immunity” skin nodules or plaques loaded with M. leprae. May have severe peripheral nerve damage. May lose eyelashes & eyebrows, body hair, nails, ulcers (may get infected and → death)

• Dx: Skin biopsy- look for disseminated lesions with acid fast bacteria

Do Hansen’s Patients’ limbs fall off?

NO

Leprosy in Armadillos

• Why? Relatively low body temp & “Weak” immune response

• For every 5 exposed/infected only 1 has clinical disease

• Lepromatous Disease most common (more severe, die)

• Dx: Ear biopsy- dissemated disease w/ acid fast bacteria

M. Leprae

• Does NOT live long in environment (2 weeks max under moist conditions)

• Transmission route- close contact with an untreated person (or Armadillo) who has it (respiratory?)

• Handling Armadillos not advised- especially if they appear sick!

Questions

• Do any Mycobacteria spp have significant population level impacts on wildlife? No, can transmit to LS and be shared with humans)

• Why are they important?