Bacterial Issues in Pet Parrots

This was a question from a client. I felt that I should address the subject of bacteria in pet parrots, as there is a lot of confusion on interpretation of cultures in parrots.


My quaker recently died from a cause that left me shocked. My avian vet informed me that the cause of death is the most common for all pet birds and is one that is easily avoidable. It is E. coli infection, from the same E. coli that is indigenous to the human digestive system. How do birds get this infection? By our kissing and cuddling them. My quaker, Mr. Tzip, used to say: "I love you" while giving me birdie kisses and would steal carrots from my mouth. I had no idea he would pick up a fatal infection from this. I know we all love our birds but I also know that none of us would want to do anything harmful to them. That is why I am writing this letter.


Please let me offer my condolences about the loss of you pet quaker parakeet. Losing a dear feathered friend is always a tragedy, and if you feel somehow responsible, it seems to make it so much worse.

Let me teach you and my readers about bacterial infections in birds and Escherichia coli, aka E. coli., specifically. That may, in some way, assuage your guilt. So, what exactly is E. coli? We hear that name tossed around a lot these days, often in relation to food borne outbreaks from contaminated food products, such as hamburger meat, unpasteurized apple juice or cider, salad, salami or unpasteurized milk.

E. coli is a Gram negative bacterium in the Enterobacteriaceae family. There are many harmless or even beneficial strains of E. coli that occur widely in nature. E. coli is the predominant non-pathogenic (non-disease-causing) facultative anaerobic (can live and multiply with or without the presence of oxygen) member of the human intestinal microflora. Some strains can cause disease of the gastrointestinal tract, urinary tract and central nervous system in humans. Interestingly, the intestinal tracts of almost all birds (including some parrot species, especially cockatoos and Eclectus) and mammals, including non-human primates and horses are colonized by E. coli. Birds, especially psittacines, are less dependent on E. coli and rely more on Gram positive gut bacteria. However, softbills, including finches, songbirds and jays, pigeons and doves, poultry, waterfowl, raptors and ratites all have a high incidence of normal Gram negative bacteria in the gastrointestinal tract, including many strains of E. coli. These bacteria usually live quite benignly in the GI tract of these animals and birds, with no untoward consequences.

E. coli can comprise up to 30% of the bacterial flora in some psittacines, and other species, including cockatiels and budgerigars, still have some E. coli, just lesser amounts.

However, some strains of E. coli are among the most common bacterial pathogens responsible for diarrheal diseases in humans, especially children and those with less-than-optimal immune systems. Many cases of infant diarrhea in developing countries are caused by pathogenic strains of E. coli that cause toxin formation or that invade and destroy bowel mucosa. One very serious strain goes by the serotype: O157:H7, which causes diarrhea, copious bloody discharge and no fever. This strain produces a toxin that affects the kidneys, and can result in acute renal failure, especially in infants. In humans, this strain is often associated with the ingestion of inadequately cooked hamburger meat.

Bacteria often found in the human mouth

(Note: current research shows that there can be over 600 different bacterial species found in a healthy human's mouth.)

  1. Lactobacillus
  2. Clostridium
  3. Corynebacteria
  4. Proteus
  5. Prevotella
  6. Haemophilus
  7. Pseudomonas
  8. Staphylococcus
  9. Streptococcus
  10. E. coli
  11. Enterococcus
  12. Mycoplasma
  13. Neisseria
  14. Actinomyces

E. coli can certainly be responsible for causing all sorts of infections in psittacine birds, and can even penetrate through the pores in egg-shells, resulting in dead-in-shell embryos or death of recently hatched chicks. E. coli is identified as one of the most common causes of infection of the oviduct and reproductive tract in parrots.

I think it is safe to say that E. coli is a quite common bacterial organism, found in human mouths (25% of the time, anyway), it is found in dog and cat feces, manure used to fertilize produce and flowers, and it is found in the gastrointestinal tract of many animals we interact with on a daily basis. MOST of the time, it is harmless, and causes no problems whatsoever. However, a pathogenic strain may find its way into produce from the grocery store that has not been thoroughly rinsed, so when it is fed to a bird, it may result in serious, life-threatening or even fatal disease. A dangerous strain, such as O157:H7 would likely cause a human to become ill, but many healthy adult humans exposed may be able to mount an effective immune response. This strain won't be commonly found in a healthy human mouth.

Any time E. coli is found on a culture from other than the intestinal tract of a bird, it should be considered pathogenic. E. coli has the ability to proliferate uncontrollably outside of its normal home territory of the GI tract. But, some strains of E. coli can also cause gastrointestinal disease and diarrhea, often dangerous and potentially fatal, if not identified and treated in time.

How is E. coli diagnosed? Most commonly, it will be isolated and cultured from the bird, and then the lab will perform antibiotic sensitivity tests, to ascertain which antibiotics are most likely to succeed in treating this infection. Support care, including kaolin and pectin or bismuth subsalicylate, fluid therapy, supplemental heat and nutrition are all important to help care for the bird. Other tests, including a DNA PCR for identifying these bacteria, and sophisticated assays involving biochemical reactions, can also be performed. It may be possible to get a basic idea if E. coli could be the culprit in some isolates by assessing which antibiotics the organism is susceptible to. Blood tests to measure blood chemistries and also to check the complete blood count, including white blood cell count and differential are often helpful in determining if an infection caused by bacteria is present. Specific antibiotic therapy can successfully eliminate the bacteria from a bird's system, however, the organisms can survive in dried droppings and contaminated dander for quite a long time. So, clean up and disinfection of the bird's environment is mandatory.

Bacterial cultures in birds should never be used solely as a diagnostic method. These tests must also be evaluated in light of the physical examination, history, diet and other tests, most importantly the CBC, especially the white blood cell count (WBC). If the WBC is within the normal range and the differential (the percentages of the different white blood cells) is normal, then the bacteria may be "just passing through" and not the primary source of the problem. It is very important that avian vets learn the subtle differences between the differentials of the different parrots, as some have the heterophil as the primary white blood cell, others have the lymphocyte as the primary white blood cell, and yet others often have about equal numbers of hets and lymphocytes.

So, bottom line... do I think that your actions caused the death of your bird? No. However, I wasn't there, I didn't examine or treat your bird. And I never recommend allowing a bird to take food from a human's mouth, or share silverware, because we do harbor potentially dangerous bacteria for pet birds. But, it doesn't sound like you are responsible for your bird acquiring a fatal E. coli infection, if that is what it died from. Just because an organism is cultured from a bird's cloaca, that doesn't unequivocally mean that is what killed it. Many organisms harmlessly pass through the GI tract of pet birds every day, causing little or no problem. I just want you to understand that there can be many causes of death of a pet bird, not always what appears to be the most obvious.

Copyright 2009 Margaret A. Wissman, D.V.M., D.A.B.V.P.
All Rights Reserved

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