9 Common Diseases in Chickens & the Most Effective Prevention Methods
Poultry farming in Vietnam faces many challenges due to the country’s hot and humid climate. These environmental conditions create an ideal environment for bacteria and viruses that cause common chicken diseases such as Coryza, ORT, Fowl Typhoid, and many others to thrive. Fortunately, most of these diseases can be effectively prevented through proper farm management and biosecurity practices. Farmers should equip themselves with basic veterinary knowledge and follow standard husbandry procedures to minimize losses. Let’s explore these 9 common diseases in chickens.
1. Coryza (Infectious Coryza)
Cause:
- Caused by the bacterium Haemophilus paragallinarum (currently known as Avibacterium paragallinarum).
Symptoms:
Coryza is a contagious respiratory disease that significantly affects poultry production worldwide. The most common signs include:
- Nasal discharge
- Swelling around the face and eyes
- Difficulty breathing
- Depression and lethargy
- Loss of appetite
- Reduced egg production
Prevention:
- Keep poultry houses dry and protected from wind and rain.
- Disinfect the barn regularly (2–3 times per month).
- Provide balanced nutrition to strengthen the immune system.
Treatment:
If symptoms appear, isolate infected birds immediately. Veterinary consultation is recommended for diagnosis and treatment. Commonly used antibiotics include Moxcolis, Amoxy, and Nexymix.
2. ORT (Ornithobacterium Rhinotracheale Infection)
Cause:
- Caused by the bacterium Ornithobacterium rhinotracheale.
Symptoms:
ORT is one of the most serious respiratory diseases in chickens and can cause high mortality rates. Typical signs include:
- Sneezing
- Labored breathing
- High fever
- Poor growth
- Decreased egg production
Prevention:
- Maintain proper sanitation using effective disinfectants.
- Ensure good ventilation and replace litter frequently.
- Supplement feed with immune-supporting nutrients and organic additives.
Treatment:
ORT outbreaks are common during rainy seasons. Because antibiotic resistance has become widespread, fever reduction and supportive care should accompany antibiotic treatment. Antibiotics are usually administered for 2–3 days under veterinary guidance.
3. Gumboro Disease (Infectious Bursal Disease)
Cause:
- Caused by a virus belonging to the Birnaviridae family (double-stranded RNA virus).
Symptoms:
After an incubation period of about two days, affected birds may show:
- Depression
- Loss of appetite
- Ruffled feathers
- White foamy diarrhea, sometimes mixed with blood
- Pecking around the vent area
- Sudden death
Prevention:
- Maintain strict hygiene and disinfect poultry houses regularly.
- Provide a nutritionally balanced diet to strengthen immunity.
- Follow a proper vaccination schedule.
Treatment:
Although there is no specific antiviral treatment, early supportive therapy and immune boosters can improve survival rates. Electrolytes, vitamins, glucose, and vitamin C supplements are often recommended.
4. Newcastle Disease (Commonly Associated with Severe Depression in Chickens)
Cause:
- Newcastle Disease Virus (NDV).
Symptoms:
This highly contagious viral disease often affects native chicken breeds. Clinical signs include:
- Respiratory distress
- Coughing
- Dull eyes
- Bloody diarrhea
- Trembling legs
- Nervous disorders and loss of coordination
Prevention:
- Maintain good farm hygiene.
- Follow the recommended Newcastle vaccination program.
- Enhance immunity with vitamins and proper nutrition.
Treatment:
There is no specific cure. Supportive care with vitamins B and C, electrolytes, and veterinary-prescribed medications may help reduce mortality.
5. Blackhead Disease (Histomoniasis)
Cause:
- Caused by the protozoan parasite Histomonas meleagridis.
Symptoms:
- Unsteady walking
- Trembling legs
- Ruffled feathers
- Yellow diarrhea mixed with blood
- Bluish discoloration of the head
- Poor appetite and stunted growth
Prevention:
- Keep poultry houses clean and dry.
- Apply proper sanitation and parasite control measures.
- Use lime around outdoor areas to reduce parasite eggs.
Treatment:
Common medications include:
- Metronidazole (50–60 mg/kg body weight/day)
- Dimetridazole
- Ronidazole
- Ipronidazole
Treatment is generally maintained for 3–5 consecutive days.
6. Infectious Bronchitis (IB)
Cause:
- Caused by the Coronavirus affecting poultry.
Symptoms:
Clinical signs vary depending on the bird’s age.
Young chicks:
- Coughing
- Wheezing
- Nasal discharge
- Difficulty breathing
- Mortality rates may reach 40%.
Laying hens:
- Egg production may drop by up to 70%.
- Poor eggshell quality and misshapen eggs.
Prevention:
- Regularly disinfect poultry houses.
- Improve overall nutrition and immune support.
- Implement a proper vaccination program.
Treatment:
There is no specific treatment for Infectious Bronchitis. Management focuses on supportive care, reducing secondary bacterial infections, and maintaining a clean environment.
7. Fowl Typhoid
Cause:
- Caused by Salmonella bacteria.
Symptoms:
Young chicks (8–10 days old):
- Depression
- Dehydration
- Sticky vent area
- Bloating
- Reduced feed intake
Laying hens:
- Poor egg quality
- Increased production of soft-shelled or abnormal eggs
Prevention:
- Maintain clean water and feed sources.
- Regularly disinfect poultry facilities.
- Practice strict biosecurity measures.
Treatment:
Electrolyte and vitamin supplements are commonly used as supportive therapy. Products containing oral rehydration salts may help affected birds recover.
8. Marek’s Disease
Cause:
- Caused by the Herpesvirus.
Symptoms:
The virus forms tumors in various internal organs, including:
- Liver
- Lungs
- Spleen
- Intestines
As tumors enlarge, they compress nerves and may cause:
- Paralysis
- Blindness
- Weight loss
A typical dead bird may be found lying with one leg stretched forward and the other backward.
Prevention:
- Apply thorough cleaning and disinfection procedures.
- Raise different age groups separately.
- Isolate sick birds promptly.
- Vaccinate chicks according to veterinary recommendations.
Treatment:
Currently, there is no effective treatment for Marek’s Disease. Prevention through vaccination remains the best strategy.
9. Necrotic Enteritis
Cause:
- Caused by Clostridium perfringens type A and C.
Symptoms:
- Bloody diarrhea
- Yellowish-white mucus in feces
- Loss of appetite
- Sudden death
Conventional anti-diarrheal medications are often ineffective.
Prevention:
- Keep poultry houses clean and dry.
- Regularly disinfect barns and equipment.
- Follow vaccination and biosecurity protocols.
- Avoid overuse of antibiotics to reduce resistance.
Treatment:
There is no specific cure. Infected birds should be isolated immediately. Supportive nutrition and veterinary-prescribed feed additives may help suppress bacterial growth during recovery.
Conclusion
Common chicken diseases can cause severe economic losses in poultry production. While some diseases can be effectively treated, others still have no specific cure. Therefore, maintaining a clean environment, providing balanced nutrition, implementing strict biosecurity measures, and following a proper vaccination schedule remain the most effective ways to protect your flock.
In addition, poultry farmers should avoid the excessive use of antibiotics and gradually adopt sustainable and organic farming practices to reduce antimicrobial resistance and improve long-term flock health.
