Overview of Omphalitis in Poultry
(Navel ill, “Mushy chick” disease, Yolk sac infection)
Omphalitis is a condition characterized by infected yolk sacs, often accompanied by unhealed navels in young fowl. It is infectious but noncontagious and is associated with poor regulation of incubation temperature or humidity and marked contamination of the hatching eggs or incubator. If young poultry are placed in contaminated transportation boxes before their navels are completely closed, bacteria can migrate up the patent yolk stalk and infect the yolk sac.
The navel may be inflamed and fail to close, producing a wet spot on the abdomen; a scab may be present. Opportunistic bacteria (coliforms, staphylococci, Pseudomonas spp, and Proteus spp) are often involved, and mixed infections are common. Proteolytic bacteria are prevalent in outbreaks. The yolk sac is not absorbed and often is highly congested or may contain solidified pieces of yolk material; peritonitis may be extensive. Edema of the sternal subcutis may be seen. Affected chicks or poults usually appear normal until a few hours before death. They have little interest in food and water and are often found severely dehydrated. Depression, drooping of the head, and huddling near the heat source usually are the only signs. Mortality often begins at hatching and continues to 10–14 days of age, with losses of as much as 15% in chickens and 50% in turkeys. Chilling or overheating during shipment may increase losses. Persistent, unabsorbed, infected yolks often produce chicks or poults with reduced weight gain.
There is no specific treatment; antibiotic use is based on the prevalent bacterial type involved. Even then, treatment may not result in satisfactory outcomes, because severely affected chicks and poults often die, and unaffected birds are unlikely to be aided by antibiotic treatment. The disease is prevented by careful control of temperature, humidity, and sanitation in the incubator. Only clean, uncracked eggs should be set. If it is necessary to set dirty eggs, they should be segregated from clean eggs. Sanitizing detergents must be used according to directions if eggs are washed. Time, temperature, and frequent changes of water are as critical as the concentration of sanitizer in both wash and rinse water. The rinse should be warmer than the wash water (which should be warmer than the internal temperature of the egg) but should not be >60°C.
The incubator should be cleaned and disinfected thoroughly between hatches. If fumigation is to be done with formaldehyde, vents should be closed. Thirty mL of 40% formaldehyde/0.6 m3, or paraformaldehyde (in the strength recommended by the manufacturer), should be allowed to evaporate in the closed incubator or hatcher. The machines are readily contaminated after fumigation unless the exterior of the machines and the rooms in which they are located are also cleaned and disinfected.