Disorders of the nervous system can cause chicks to act in abnormal—and often scary-looking—ways. Typically, you’ll see the head turned or twisted in an odd direction, a condition commonly referred to as “crookneck” or “wry neck.”
The technical word for twisted neck is “torticollis,” from the Latin words “torquere,” meaning to twist, and “collum,” meaning neck. When torticollis is not a steady pull, but occurs in painful muscle spasms, the technical term is “opisthotonos,” a Greek word meaning “drawn backward.”
Chicks experiencing nervous systems disorders also may appear uncoordinated, weak, staggery or paralyzed in one or both legs.
If left uncorrected, the neurological disorder may lead to trampling of the unfortunate chick by brooder mates or loss of the ability to eat and drink. The five most common conditions that cause torticollis in chicks are:
- congenital loco
- crazy chick disease
- head or neck injury
- Marek’s disease
Congenital loco is an inherited disorder caused by a recessive gene. It appears in chicks at the time of hatch.
Unless you hatch your own eggs, you are unlikely to see this condition. An affected chick’s neck twists backward. This throws the chick off balance and leaves it unable to consume food or water.
Although this condition appears to result from an inability to control the neck muscles, a few studies have indicated it may be caused by a defect in the ear structure. Chicks experiencing congenital loco rarely survive more than a few days.
A mysterious condition also called “congenital loco” occurs sporadically over a period of a few days, then disappears as mysteriously as it came.
This condition looks identical to congenital loco. But the fact that it doesn’t appear at the time of hatch and isn’t lethal indicates it may be a separate and unrelated issue, with an as-yet unknown cause.
To confuse things further, this mystifying condition is sometimes called “stargazing.”
Stargazing is a nervous system disorder that will causes a chick to bend the neck so far backward that the head touches its back. The beak will point skyward—hence the name “stargazing.”
The epileptic-like muscle spasms that pull the head back typically cause the bird to tip over. After a few days of struggling, the chick will die from lack of food and water.
This condition typically appears in chicks less than 1 week old, caused by vitamin B1 (thiamine) deficiency in the diet of the chick’s parents. Depending on the severity of the deficiency, the chick may recover if given a vitamin B1 supplement.
Crazy Chick Disease
Crazy chick disease resembles stargazing, except stargazing chicks stop eating. Chicks with the disorder continue to eat despite their dire condition.
The formal name for crazy chick disease is “avian encephalomalcia” (from the Greek words “enkephalos,” meaning “brain,” and “malakos,” meaning “soft”).
Encephalomalacia is a softening of the brain tissue that, if not treated early, results in permanent brain damage. An affected chick may stargaze or pull its head down between its legs, often twisting the head to one side.
This position puts the chick so far out of balance that if it tries to walk it tumbles over.
The primary cause of this disease is a deficiency in vitamin E, giving the disease its other formal name, “hypovitaminosis E.” The vitamin may actually be present in the diet but unavailable for metabolism.
For example, when vitamin E is furnished in the form of polyunsaturated fats—such as cod liver oil, corn oil, soybean oil or wheat germ oil—that have become rancid, the vitamin oxidizes and is no longer available for absorption.
Chicken actually require very little vitamin E requirements. This condition is therefore unlikely to occur where breeder flock rations and chick starter consist of appropriately formulated fresh rations.
A breeder flock ration deficient in vitamin E results in chicks that exhibit crazy chick disease within a week of hatch. If chicks develop this condition because their starter ration lacks sufficient metabolizable vitamin E, signs will appear within two weeks of being fed the deficient diet.
Without treatment, the chick’s brain eventually deteriorates to the extent that the chick can no longer function, whereupon it dies.
When started early enough to avoid serious damage to the brain, an effective treatment is to add 1⁄2 teaspoon vitamin AD&E powder per gallon of drinking water until signs disappear.
Head or Neck Injury
Torticollis is not always caused by disease but may result from a blow to the head or neck. Head injuries that lead to nervous system disorders are common in crested breeds. These tend to have skulls that are less bony than noncrested breeds.
If the crested skull bone doesn’t entirely enclose the brain—because of genetics or an injury—a blow can cause the brain to swell and press through the skull’s gap.
A chick with such a head injury may tuck its head down between its legs and perhaps move backward until the bird backs into the brooder wall or other obstacle. Depending on the extent of the injury, the condition may be temporary or permanent.
When raising chicks of crested breeds, providing a safe brooding environment is essential.
Unlike other nervous system disorders of chicks, Marek’s disease is caused by herpesviruses that replicate in feather follicles, are shed in dander and survive for a year or more in coop dust. Chicks acquite this highly contagious disease (which doesn’t affect humans) when chickens inhale contaminated dust or dander from infected birds.
The disease—named after veterinarian József Marek who first described it—is the most common viral disease of backyard chickens. It’s so common you can safely assume your chickens are infected, even if they don’t appear sick.
Marek’s disease infects primarily young and growing chickens. But it can also affect aging birds. This complex disease can take on many forms, including a nerve form that results in incoordination, muscle spasms and progressive paralysis of neck, leg or wing.
A transient nerve form that affects chicks 2 to 3 weeks of age appears as temporary limp paralysis of the neck or legs. This leaves birds with a twisted neck upon recovery from paralysis.
Marek’s disease switches off a chicken’s tumor-blocking genes and also attacks cells that produce antibodies, thus impairing the bird’s immune system. It typically occurs in combination with other diseases, especially coccidiosis and respiratory infections caused by E. coli bacteria.
Fatality of Marek’s disease depends on the virulence of the virus strain, as well as on the presence of any other debilitating conditions.
The first few weeks of a chick’s life are the most critical time for infection. Chicks that are isolated from mature chickens until they reach the age of 5 months develop a natural immunity.
Strains of some chicken breeds are genetically more resistant than others. Fayoumis are resistant to Marek’s, while Sebrights and Silkies tend to be particularly susceptible, as are some strains of Polish, among other exotic breeds.
No known treatment will cure chickens of Marek’s disease. But there is a vaccine. Most hatcheries offer the option of vaccinating chicks. If you hatch your own chicks, you can purchase the Marek’s vaccine and administer it yourself.
Because the vaccine does not work in chicks already exposed to Marek’s disease, administer it as soon after hatch as possible. Keep vaccinated chicks in isolation while their immunity develops.
Vaccination doesn’t prevent the possibility that the chickens may become infected by and spread Marek’s disease. But it does prevent the viruses from causing tumors and paralysis. And it reduces shedding of viruses by infected birds.
Seeing any of these nervous system disorders in baby chicks can be a decidedly disturbing experience. By learning to recognize each of these five neurological conditions you will stay equipped to rapidly deal with treatable conditions.
You can also prepare yourself for the inevitable regarding those that are not.
Sidebar: Minimize Marek’s
The following four management practices will help you reduce the risks of Marek’s disease.
- Brood chicks away from mature birds until they develop natural resistance by 5 months of age.
- Vaccinate newly hatched chicks. Vaccination does not prevent Marek’s disease. But it does prevent tumors and paralysis if administered before exposure to the virus.
- Keep turkeys with chickens, or put a little turkey poop in the chick brooder. Turkeys carry a related, though harmless, virus that keeps Marek’s from causing tumors in chickens.
- Breed for resistance. Some chickens carry resistance factor B21, which can be detected through blood testing.
This article originally appeared in the November/December 2020 issue of Chickens magazine.