Incubation Problems due to Breeders’ Microbial & Fungal Infections.




 Responsible microorganism






Mycoplasma gallisepticum

Mycoplasma meleagridis

Mycoplasma synoviae

Mycoplasma anatum




General view:

Embryo Mortality after day 15th of incubation.

Mortality of embryos immediately after eggshell piping.


Infection spreading:

 Infection is transmitted inside the breeder hen by close contact of the infected air sacs of the breeder bird with the follicles of its ovary. Mycoplasma infection is transmitted to the yolk shack of the egg thus the embryo is infected.

Additional spreading of the disease happens inside incubators and chick transport boxes.



By post mortem examination of the embryo immediately after piping the eggshell

We find a foamy yellowish exudate inside the thoracic air sacks of the embryo. This post mortem examination should be performed to at least 20 samples and repeated three times for three consecutive incubation cycles.


The veterinarian must always correlate these findings to possible clinical signs of the disease on the breeding flock.











Salmonella Gallinarum








General view:

 Some fertile eggs are not developed at all. Another part of the batch of these embryos dies during incubation and hatching time. Some embryos stay alive and become carriers of the disease.


Infection spreading:

The gonads of the breeders (ovary and testicles) are infected. The infected hens lay infected eggs. A healthy hen may even give infected eggs if it is mated by an infected rooster.

 The percentage of infected eggs may be between 1-50%.


Diagnosis and prevention:

 Some of the eggs examined do not have developed blastoderm.

 Routine disinfection of the eggs before placement inside the incubator







 Salmonella Typhimurium




Many other Salmonella









General view:

 Dead embryos. If the embryos do not die they infect healthy chicks of the same batch.


Infection spreading:

 Paratyphoid is a breeders’ food borne disease. The flock is infected by consuming feed contaminated by S. Typhimurium. Then it transmits the microbe by the feces. The egg is infected when passing through the cloaca. Thus S. Typhimurium is already present on the egg shells.

Salmonella Typhimurium find its way through the pores of the egg shell during the first week of incubation.

 Infected chicks that survive infect the healthy ones by the hatcher dust and egg shell contact.

Another way of spreading of the disease is by chick sexing procedure, transfer boxes and brooding spaces.


Diagnosis and prevention

Regular microbiological examination of the breeder feed.

Routine disinfection of the eggs before placement inside the incubator








Escherichia Coli


 Together with:


Staphylococcus Aureus


Streptococcus Faecalis




General view:


Dead embryos. If the embryos do not die they infect healthy chicks of the same batch. The chicks that survive usually develop omphalitis (yolk sack infection). If Staphylococcus Aureus is complicated the chick dies at the first 3 days after hatching. If Streptococcus Faecalis is complicated the chicks die by septicemia at the age of 10-20 days.


Infection spreading:


Pathogenic strains of Escherichia coli infect the intestine of the breeders. Then the uterus is infected through hen’s cloaca from which the eggs are infected.

Inside the hatchers the infection of the chick’s lungs and air sacks is air borne.


Diagnosis and prevention:


Routine disinfection of the eggs before placement inside the incubator






Aspergillus Fumigatus



General view:


Some embryos die during incubation. Most of them Survive.


Infection spreading:


The eggs are contaminated from the environment of by the nest material. Washed eggs or eggs dipped in antibiotic solutions are more susceptible to infection by Aspergillus Fumigatus. The infection is done through the pores of their eggshell.

Inside the hatchers the infection is transmitted   by air.


Diagnosis and prevention:


Sometimes we can detect Aspergillosis by candling of the eggs. The Aspergillosis infection lesions are present inside the egg’s air cell.

Careful disinfection of the incubators and the eggs before placement. Disinfection of the hatchers. Regular cleaning of the nests.




Source: Poultry Clinical Pathology by Efstratios B. Artopoios, 1st Edition in Greek language.1980, Editor: Thessaloniki Veterinary School

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