• Humans can contract many of the diseases that affect chickens.many chickens on the farm image by Ivonne Wierink from Fotolia.com
  
  Chickens are susceptible to a variety of diseases that affect the eyes and cause debilitating symptoms. Bacteria, fungal growth, viruses and even injuries sustained on the farm can cause these infections. Owners should closely monitor the health of the flock to catch the early symptoms of potentially fatal chicken diseases.
  
  

Avian Conjunctivitis

• Conjunctivitis is the technical term for what humans know as "pink eye." Infected birds will show encrustations and thick growths around the eyes and in some cases the growths can totally encase the eye, rendering the bird partially or completely blind. Other symptoms can include reddening of the eyes, watery eyes, respiratory problems and even death. A number of infections can cause conjunctivitis, including bacteria, parasites and some injuries.
  
  

Marek's Disease

• This is a highly contagious viral disease causing blindness in one or both eyes of a chicken along with other debilitating symptoms. According to the Department of Animal Science at the University of California Davis, Marek's disease takes four to 12 weeks to grow in a flock before infected chickens begin to show the first signs of infection. The best strategy against the disease is to conduct vaccination regimens on all young flocks before introducing them to the farm.
  
  

Ammonia Burns

• Ammonia gases created by the buildup of damp and soiled litter can cause lopsided shape to the eyes of chickens along with facial swelling and blindness, according to the Welp Hatcheries website. Prevention is the best defense against this condition with frequent changes of litter and added vitamin A into the diet of the flock.
  
  

Mycoplasma Infection

• This slow-acting disease of the eyes and respiratory system is characterized by red or swollen eyes, tail bobbing, slow growth and lesions leading to death. Treatment with broad-spectrum antibiotics is the method of fighting this disease with handlers working to decrease airborne particles around the nest that could cause secondary infections.