Marek’s Disease in Chickens
Marek’s disease, also called “MD” or “fowl paralysis,” is a highly contagious disease spread by the herpes virus. It’s one of the most common chicken illnesses, so it pays to know what this disease is, how it spreads, and how to treat it.
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What Is Marek’s Disease In Chickens?
In her book “The Chicken Health Handbook,” Gail Damerow writes, “Marek’s is one of the most widely studied chicken diseases; entire books have been written about this one condition alone. It is so common that you can safely assume your chickens have the virus, even if they don’t show any signs of infection.”
The herpes virus Alphaherpesvirinae causes the disease. It has the ability to evade a chicken’s immune system and infect white blood cells, causing some to become cancerous. These cells then infect internal organs such as the kidney or liver, nerves, muscle, and skin.
There are five forms of Marek’s disease. Each form has different symptoms, and vastly different mortality rates. The five forms of Marek’s disease are:
- Eye form
- Nerve form (neural leukosis)
- Nerve form transient (pseudobotulism)
- Skin form
- Visceral Form (visceral leukosis)
How Does Marek’s Disease Spread?
According to the Merck Veterinary Manual, the virus that causes Marek’s disease matures in the epithelium of the feather follicle. The epithelium is a layer of cells that line hollow surfaces and organs, such as the feather.
The disease spreads through fluff and dander. A bird is infected when they inhale the dust or fluff. The virus can also spread through oral and nasal secretions, as well as through the gloves and shoes of a handler or backyard chicken keeper. However, infected hens cannot pass the virus on to their chicks through the egg.
Mareks’ disease can survive for months in the bedding of the coop. Once present, it will quickly spread to all the other birds in the flock.
Can Humans Get Marek’s Disease From Chickens?
Good news! Humans cannot become infected with the herpes virus that causes Marek’s. In this age of constant worry over zoonotic disease, we can do a happy dance over that one. 🙂
Marek’s Disease Symptoms
Marek’s disease most commonly affects young chickens, between 8 and 20 weeks of age. It’s more common in hens than in roosters. And, once a chicken is infected it will carry the virus for the rest of its life.
Not all chickens will show symptoms of Marek’s disease. Some breeds, and some strains of the virus, don’t exhibit any symptoms at all. Some forms of the virus have a 0% mortality rate, while other strains have 60% to 80% mortality. Therefore, there’s quite a different in how this virus manifests, and affects a flock!
According to Damerow, each of the following forms of Marek’s displays different symptoms.
Eye Form (Gray Eye)
The Eye Form of Marek’s is considered rare, and has up to a 25% mortality rate. Symptoms include:
- Graying, shrunken iris
- Irregular-shaped pupil
- Unequal-size pupils
- Blindness in one or both eyes
Nerve Form (neural leukosis)
The neural leukosis form of Marek’s is considered sporadic, and has up to a 20% mortality rate. Symptoms include:
- Lack of coordination or walking stilted
- Muscle spasms
- Progressive paralysis of the neck, legs, or wing
- Weight loss
- Paleness
- Enlarged crop
- Gasping
Nerve Form, Transient (pseudobotulism)
The pseudobotulism form of Marek’s is common. However, it has a 0% mortality rate. Symptoms include:
- Temporary limp paralysis of neck or legs
Skin Form
The skin form of Marek’s is rare, and has a 0% mortality rate. Symptoms include:
- Enlarged feather follicles, especially on legs
- Red, bloody looking shanks
Visceral Form (visceral leukosis)
The visceral form of Marek’s is common, and has a 60% to 80% mortality rate. Symptoms include:
- Rapid weight loss
- Sometimes greenish diarrhea
- Massive internal tumors
Treatment: Medical
Unfortunately, there is no medical cure for Marek’s disease.
Treatment: Herbal
That said, you might be able to help reduce the severity of Marek’s disease symptoms in your birds with antiviral herbs.
Oregano Oil
For example, oil of oregano is a powerful antiviral, and there’s no harm in adding a drop or two to your chicken’s water to see if it can help.
Although it’s always important to purchase and use quality herbs and ingredients, this is doubly important with oil of oregano. Purchase the highest quality oregano oil you can afford. We use North American Herb and Spice Oil of Oregano, and have for over a decade. It’s very potent, and one bottle will last you years.
Dosing: I would start with one drop of oregano oil per gallon of water. Again, please keep in mind that this is a theoretical treatment, and I could find no information on exact dosing for chickens.
As a quick aside, oil of oregano is the best treatment I’ve found for treating food poisoning. It works every time, especially if you take it the moment you start feeling ill. I don’t travel without it.
Chinese Skullcap
Another herb to try is Chinese skullcap (Scutellaria baicalensis). In his book “Herbal Antivirals,” herbalist Stephen Buhner states that Chinese skullcap is a broad-spectrum antiviral that inhibits viral replication, suppresses viral gene expression, reduces viral RNA in infected cells, protects cell membranes from virus-initiated cytokines, and much more.
Keep in mind that the specific herpes virus that causes Marek’s, Alphaherpesviri, is not listed in Buhner’s guide as being affected by Chinese skullcap. However, Buhner’s guide doesn’t cover viruses that affect animals and not humans.
As a self-taught herbalist, I’ve used Chinese skullcap, along with licorice, isatis, and other herbs, to successfully treat shingles, which is caused by the herpes zoster virus. I’ve never had a chicken come down with visible symptoms of Marek’s, but if I did I wouldn’t hesitate to try treating it with Chinese skullcap and oil of oregano. It likely won’t cure the condition, but it might help alleviate the severity of symptoms and provide your chicken with some relief.
Dosing: I would start with five drops of Chinese skullcap per gallon of water. Again, please keep in mind that this is a theoretical treatment, and I could find no information on exact dosing for chickens.
If you decide to try skullcap, make sure you purchase Chinese skullcap (Scutellaria baicalensis), NOT American skullcap (Scutellaria lateriflora). Chinese skullcap is antiviral, while its American counterpart is better suited to treating depression and nerve issues.
Prevention
There is only one way to prevent the spread of lethal Marek’s disease: vaccination.
Vaccinate Young Chicks
One of the best ways to prevent Marek’s disease is to vaccinate young chicks as soon after hatch as possible. Most commercial hatcheries offer the option to vaccinate against Marek’s, and it’s definitely a good investment. If you have a broody hen and plan to let her raise chicks, you can purchase the vaccine and administer it yourself on hatch day.
Keep in mind that vaccination is not 100% foolproof. The vaccine won’t prevent your chicken from becoming infected with Marek’s disease. However, it will protect your chickens from paralysis and tumors. It will also reduce the viral load the chickens carry and shed throughout their life.
According to Mississippi State Extension, less than 5% of vaccinated birds will show symptoms. So, this is one vaccine that it definitely pays to get for your birds.
Last Word
Thankfully, I’ve never had a chicken with visible symptoms of Marek’s disease. However, as highly transmissible as Marek’s is, there’s a good chance that day will come. If and when it does, I won’t think twice about trying herbal treatments like oil of oregano and Chinese skullcap. I have many past successes using both of these herbs, and truly believe that they are a viable treatment option.
I’d love to hear back from you. Have you ever had Marek’s in your flock?
