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.
The primary cause of omphalitis in poultry is contact of an open navel with contaminated surfaces. If young poultry are in contaminated environments before their navels are completely closed, bacteria can migrate up the patent yolk stalk and infect the yolk sac. Opportunistic bacteria (coliforms, staphylococci, Pseudomonas spp, and Proteus spp) are often involved, and mixed infections are common. It is associated with poor regulation of incubation temperature and humidity and enhanced by marked contamination of hatching eggs, incubators, or transportation boxes. Chilling or overheating during shipment or early placement may increase losses.
In poultry with omphalitis, the navel may be inflamed and fail to close, presenting a wet spot on the abdomen; a scab may be present. Affected birds are depressed and anorexic and huddle near heat sources with a drooping head. They fail to gain weight, and there is increased mortality from hatch to two weeks of age. Affected chicks or poults usually appear normal until a few hours before death. Losses of as much as 15% in chickens and 50% in turkeys have been seen.
Young fowl are dehydrated and have a persistent, unabsorbed yolk in the body cavity, which may be congested, malodorous, and contain solidified yolk material. Peritonitis may be extensive.
There is no specific treatment for omphalitis in poultry; 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.