Diseases of Broilers

Overview

Disease is any abnormal condition that interferes with the normal functioning of a living organism. Broiler diseases are commonly grouped by cause as viral, bacterial, parasitic, and non-infectious problems, including conditions such as leg weakness. The cause helps determine the appropriate response. Antibiotics act against susceptible bacteria, while anticoccidial products act against coccidia. Lasota vaccine helps protect birds against Newcastle disease, while Gumboro vaccine helps protect them against infectious bursal disease. A treatment chosen for the wrong cause may not help the birds, so the likely cause should be established before treatment whenever possible.

Important: This page is general education and not a substitute for professional veterinary advice.

Quick reference

Viral diseases

Antibiotics do not treat viral infections, and using them for a viral disease wastes money and encourages drug resistance. Control relies on vaccination, biosecurity and good management.

Newcastle disease

Caused by the Newcastle disease virus. Early signs include coughing, gasping and nasal discharge, followed by paralysis, twisted neck, greenish watery diarrhoea, reduced feed and water intake, and sudden death. It is highly contagious and can cause heavy mortality. There is no effective treatment, so vaccination is essential. Vaccination does not give complete protection on its own, so combine it with good biosecurity and proper vaccine storage and handling.

Lasota vaccine administration

Gumboro disease (Infectious Bursal Disease)

Caused by the Infectious Bursal Disease Virus (IBDV). Signs include whitish watery diarrhoea, dullness, ruffled feathers, trembling, vent picking, loss of appetite, and sudden death. It is highly contagious and can cause heavy mortality. Gumboro disease also damages the immune system, so survivors may become more susceptible to other infections and may respond poorly to some vaccines. Birds can be protected against Gumboro disease through proper, timely vaccination, combined with good biosecurity and proper vaccine handling.

Gumboro vaccine administration

Avian influenza (bird flu)

A highly contagious viral disease that has caused outbreaks in Nigeria. Warning signs include sudden high mortality, swelling of the head and face, bluish or dark combs and wattles, bleeding under the skin of the legs, loss of appetite and respiratory signs. Because these overlap with Newcastle disease, only laboratory testing can confirm it.

If you suspect avian influenza: do not sell, move or slaughter the birds, limit access to the pen, wash your hands and change clothes and footwear after handling birds, and report immediately to your state veterinary officer or nearest veterinary clinic. The virus can infect people, so do not handle sick or dead birds with bare hands.

Bacterial diseases

Antibiotics work against bacterial infections but are ineffective against viral diseases such as Newcastle disease and Gumboro disease, so using them on those outbreaks wastes money. Always observe the withdrawal period: the time that must pass after the last dose before birds can be sold or slaughtered for consumption. It is labelled on the drug pack, and ignoring it can leave antibiotic residues in meat, creating a food safety risk.

Fowl typhoid

Caused by Salmonella gallinarum. Signs include yellowish diarrhoea, pale combs and wattles, dehydration, reduced feed intake and weakness. Deaths build up over several days rather than all at once, but losses can be high if treatment is greatly delayed. The disease spreads through carrier birds, contaminated feed, water, equipment, and flies.

To prevent it, keep litter dry and clean, and follow a proper broiler medication schedule. Drugs such as Enrofloxacin, Amoxycol, Amocol or GDE Biotics could be used for its treatment.

Chronic respiratory disease (CRD)

Caused mainly by Mycoplasma gallisepticum. Signs include persistent coughing, sneezing and nasal discharge, often from about the third week. It is made worse by poor ventilation, overcrowding, ammonia from wet litter, and secondary infections such as E. coli. CRD mix is a widely used antibiotic treatment, along with antibiotics such as tylosin or doxycycline, and the withdrawal period must be observed. Prevent it with good ventilation, correct stocking density, dry litter and chicks from Mycoplasma-free breeder flocks.

Colibacillosis (E. coli infection)

Caused by Escherichia coli, and it often follows another problem such as CRD, Newcastle disease, Gumboro disease or poor litter and ventilation. Signs include breathing difficulty, dullness, reduced feed intake, diarrhoea, swollen abdomen and death. Prevent it with clean drinking water, dry litter, good ventilation and sanitation. Enrofloxacin is a commonly used antibiotic for treatment.

Parasitic diseases

Coccidiosis

Caused by protozoa of the genus Eimeria, including E. tenella, E. maxima, E. acervulina, E. necatrix and E. brunetti. The typical sign is brownish watery diarrhoea that turns blood-stained or bloody if untreated, with reduced feed intake, dehydration and dullness.

Deaths are usually more gradual than in Gumboro or Newcastle disease, but losses become significant if treatment is delayed. Prevent it by keeping litter dry and clean, maintaining clean drinkers, and following a medication schedule that includes a suitable coccidiostat. If signs appear, anticoccidial drugs such as Amprolium, Keptox or Embazin Forte should be used promptly.

Worms (internal parasites)

Roundworms can affect broilers, especially those raised on ground that has held poultry before. Signs include poor growth, weight loss, pale combs and diarrhoea. Remove old litter and disinfect the pen before each new batch, keep litter dry and deworm with a suitable poultry dewormer such as Piperazine or Levamisole.

Non-infectious problems

Leg weakness and lameness

Broilers can become lame because their weight increases faster than their skeleton can support. Other causes include an imbalance of calcium, phosphorus or vitamin D3 in the feed (which can cause rickets), and injuries. Lame birds struggle to compete for feed and water.

Separate affected birds and place feed and water within easy reach. To prevent it, use a balanced broiler feed from a reputable source. The drug Tipara can be used to treat affected birds.

Ascites (water belly)

A non-infectious condition in which fluid collects in the abdomen, linked to very fast growth combined with low oxygen supply. Poor ventilation and cold stress make it worse. Affected birds have swollen abdomens, breathe with difficulty and may have bluish combs. Prevent it with good ventilation, avoiding sudden temperature drops, and not forcing growth too fast.

Summary of broiler medication schedule from Day old to 4 weeks to prevent and control diseases

Important: This schedule shows the timing and purpose of each medication, based on practical field experience. Always follow the manufacturer's dosage on the product label, or a veterinarian's instruction. Not all antibiotics and coccidiostats can be mixed together, because some combinations can reduce the effectiveness of a drug or cause problems in the birds. If you are unsure whether two products can be given together, consult a veterinarian.

Important: Preventive medication stops after week 4, but give appropriate treatment if the birds show signs of disease. Observe good biosecurity to reduce the chance of birds getting sick, and strictly observe the withdrawal period of every drug before selling or slaughtering birds, to avoid unsafe meat.

Factors that predispose broilers to diseases

Most outbreaks start with a management failure. These factors raise the risk:

• Poor ventilation: Ammonia and moisture build up, irritating the respiratory tract and weakening defences against airborne infections like CRD and Newcastle disease.
• Overcrowding: More stress, less movement, and faster spread of disease through close contact and shared feeders and drinkers.
• Poor sanitation: Dirty feeders, drinkers and equipment let bacteria, viruses and parasites accumulate and reinfect the flock.
• Wet litter: Damp litter helps coccidia oocysts and bacteria survive and multiply, raising the risk of coccidiosis and fowl typhoid.
• Stressful handling: Rough handling, sudden temperature changes, transport and constant disturbance suppress the immune system.
• Nutritional problems: Inadequate or unbalanced nutrients, vitamins or minerals weaken immunity and can cause problems such as leg weakness.
• Poor vaccination practice: Missed dates, expired or badly stored vaccines, or wrong administration leave birds unprotected against Newcastle and Gumboro.
• Weak biosecurity: Visitors, shared equipment, wild birds, rodents and flies bring disease onto the farm. Restrict entry, use a footbath, and keep new birds apart from existing stock.