Major Respiratory & Intestinal Diseases in Chickens

By Miltos Ioannou, Veterinarian

Broiler farming can be highly profitable when flock health is maintained at a high level. However, respiratory and intestinal diseases can spread quickly, especially in areas with hot and humid climates, causing severe economic losses.

Below is an analysis of the most important diseases, how they spread, the symptoms they cause, and how to prevent or manage them.

A. Respiratory Diseases

1. Infectious Bronchitis (IB)

• Epidemiology: Viral disease spread through the air as well as contaminated equipment, water, or droppings. Highly contagious, with an incubation period of 18–36 hours.

• Symptoms: Sneezing, coughing, nasal discharge, watery eyes, breathing difficulties. In laying hens: decreased egg production, misshapen or thin-shelled eggs.

• Prevention: Regular vaccination of chicks, good biosecurity, limiting visitors.

• Treatment: No antiviral drugs available. Antibiotics (e.g., Tylosin, Doxycycline) are used only to prevent secondary bacterial infections.

2. Chronic Respiratory Disease (CRD) – Mycoplasmosis

• Epidemiology: Caused by Mycoplasma gallisepticum. Spreads through direct contact, contaminated equipment, or vertically from mother to eggs.

• Symptoms: Sneezing, swollen sinuses, wheezing, watery discharge from eyes and nostrils, growth retardation.

• Prevention: Good hygiene, proper ventilation, use of vaccines in high-risk areas.

• Treatment: Antibiotics such as Tylosin, Tiamulin, or Doxycycline reduce clinical symptoms but do not completely eliminate the pathogen.

3. Colibacillosis (E. coli Infection)

• Epidemiology: Usually a secondary infection after respiratory viruses. Spreads through contaminated water, feed, dust, or droppings.

• Symptoms: Lethargy, open-mouth breathing, swollen joints, septicemia, sudden deaths.

• Prevention: Clean, dry litter, good ventilation, moisture control.

• Treatment: Antibiotics such as Amoxicillin or Doxycycline under veterinary guidance.

B. Intestinal Diseases

1. Coccidiosis

• Epidemiology: Caused by Eimeria spp. Oocysts survive for months in moist litter.

• Symptoms: Bloody diarrhea, loss of appetite, weakness, delayed growth, dehydration.

• Prevention: Vaccination of chicks, rotation of coccidiostats (Amprolium, Diclazuril, Monensin).

• Treatment: Administration of coccidiostats in water or feed under veterinary supervision.

2. Necrotic Enteritis (Clostridium perfringens)

• Epidemiology: Often occurs after coccidiosis or sudden dietary changes damaging the intestinal lining.

• Symptoms: Sudden deaths, foul-smelling droppings, lethargy, loss of appetite.

• Prevention: Control of coccidiosis, high-quality feed, use of probiotics.

• Treatment: Antibiotics such as Amoxicillin, Tylosin, Doxycycline, or Lincomycin, always under veterinary supervision.

3. Dysbacteriosis

• Epidemiology: Caused by an imbalance in the normal intestinal flora, usually due to stress, sudden dietary changes, or overuse of antibiotics.

• Symptoms: Watery droppings, poor feathering, uneven growth, reduced feed efficiency.

• Prevention & Treatment: Use of probiotics, prebiotics, balanced nutrition. Avoid unnecessary use of antibiotics.

Conclusion

Prevention is always more effective and economical than treatment.

• Vaccinate flocks on time.

• Maintain strict biosecurity and a clean environment.

• Use antibiotics only with a veterinary prescription.

Healthy birds = Better growth + Higher profits + Safe production