Case Study: Avian Encephalomyelitis

I’ve now worked on fifteen case studies: some have had happy endings (i.e. amputated toe, broken leg and survivors of a forest fire), and unfortunately, others not so much.

I came across this story when first-time chicken owner, Michelle, posted for help deciphering what was going on in her flock. It started with the illness of her cockerel, then morphed to include two of her pullets. After many online messages back and forth and the study of x-rays, videos, lab and necropsy reports I think we were able to sort out the different, but overlapping, strands to this story. (And thanks to my online vet tech friend Debra who screened all the material and pointed out where I had overlooked some key details).

Jack, 4 month old Swedish Flower Cockerel

October 28: Jack started having balance issues, but no other symptoms and was eating and drinking normally. He was isolated from the flock for observation.

November 18: Jack continued to have problems with his balance and gait. He was taken to a state licensed Avian Veterinarian, who recommended they take x-rays. Unfortunately he was not sedated and panicked during the procedure causing him to die of a ‘stroke’. Michelle feels that he died of stress in his weakened state. Based on the x-rays, it was determined Jack had a mass in his abdomen that was likely compressing a nerve and possibly causing his balance issues.

Prior to this, Michelle had a phone consult with another vet who suggested he might have Marek’s Disease. Concerned about that diagnosis she opted to have him necropsied to obtain a clear idea as to what was causing his issues. None of her other 34 chickens were showing signs of illness.

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Nov 23: Two of her pullets – Sunny, a 6 month old Speckled Sussex and Lola, a 5 month old Black Sex-Link – started showing signs of weakness, difficulty walking and distancing themselves from the flock. Michelle isolated them immediately.

Lola had dark green diarrhea during the week of her quarantine, although she wasn’t eating anything other than chicken feed. She wasn’t vaccinated for Marek’s at the hatchery. Sunny came from a different hatchery and was vaccinated.

Nov 30: Jack’s final necropsy results reported he had adequate body condition, a slightly pale liver, a slightly enlarged spleen, but his bursa, heart, lungs, liver and intestine were normal. His brainstem and white matter of the brain showed small lymphocytes and rare granulocytes.

His cause of death was determined to be viral Avian Encephalomyelitis and Michelle was given no further information other than a link to an article on A.E. She was told there were no signs of Marek’s Disease in Jack’s brain. (As someone who has experienced Marek’s in my flock I concur that his balance and gait issues appeared to be caused by a neurological issue and not the typical Marek’s leg paralysis).

The lab didn’t find any signs of the mass that was reported to have been seen by the first veterinarian on the x-rays.

Jack tested negative for Avian Influenza, Marek’s Disease, Mycoplasma gallisepticum and Mycoplasma synoviae. He couldn’t be tested for Avian Encephalitis because it requires blood work from a live subject.

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The lab wanted to obtain blood samples in order to test for AE from the two symptomatic pullets, so they were submitted for testing, euthanasia and necropsy. On admission they were reported to be hunched, their feathers were ruffled and one was reluctant to stand or walk and was sitting on her hocks.

While waiting for their necropsy results Michelle consulted a third vet, this one also with avian experience. Unfortunately their response didn’t provide any more clarity, but just left her with more questions.

“Your cockerel tested negative for Marek’s (which would have been my first guess) and had a weird pattern on brain histology (leading them to say encephalitis). Encephalitis means inflammation of neural tissue which could be from an infectious organism (bacteria, viral) or even a vitamin B deficiency.”

Dec 10: The final necropsy report indicated both pullets had good body condition. Sunny had pale, swollen kidneys; two cysts on her ovary; a grossly enlarged spleen and an enlarged liver.

Lola had severe hemorrhagic peritonitis and an enlarged ovary covered with dozens of large follicles and cysts (she had recently started laying). Lymphoma was found in her ovaries, oviducts, mesentery, pancreas, kidney, cecal and intestinal walls, one lung and part of her liver. In other words, she was riddled with cancer.

Both tested negative for Avian Influenza, Mycoplasma gallisepticum, Mycoplasma synoviae and also surprisingly, for Avian Encephalitis.

The cause of death was deemed Marek’s for both pullets, which was confirmed by blood work. Lola’s contributing cause of death was Lymphoma (cancerous tumours caused by Marek’s).

Michelle’s story illustrates what I am seeing more often with small flock keepers: the difficulty of diagnosing and getting good veterinary care for our birds. Between phone consults, in-person visits, lab testing and online support she talked with four different veterinarians. That she was given varying advice speaks to the complexity of chicken health issues.

Lots of small flock keepers think that chickens are low maintenance pets, until they run into symptoms that could point to a number of diseases. If you’re dealing with a ‘mystery’ illness it’s important to consult an experienced Avian Vet and to invest in testing to figure out what pathogens are affecting your flock.

In this case, what was first suspected as Marek’s Disease turned out to be Avian Encephalomyelitis and the subsequent birds that were assumed to have AE were diagnosed with Marek’s. Without the necropsies and lab work that provided clear diagnoses Michelle would have been left wondering what had affected her three birds, and how she can help her remaining flock.

I’m sorry this case study doesn’t have a happy ending, but am hopeful that Michelle will be able to recognize the symptoms of Avian Encephalomyelitis or Marek’s Disease if it strikes again. It’s imperative to reduce stressors in her flock which might trigger underlying illness.

One of the vet’s gave her this advice: “In my flock, young birds in the same age range would receive aggressive B vitamin supplementation (about 1cc vitamin B injectable complex given orally once, followed by over-the-counter human Vitamin B complex – 1 tab per bird – once daily in a treat, liked mashed boiled eggs) for a week or so. Failure to respond (within 24-36 hours) would get me to add in an antibiotic of some kind – tetracyclines may still be available over the counter for adding into water (check feed stores or online).

Many thanks to Michelle Buterbaugh for sharing her story, x-rays, reports and photos. And thanks to Debra Watt, Veterinary Technician, for her advice and fact-checking throughout my research.