Egg Drop Syndrome 76 is a slow spreading virus that can infect non vaccinated flocks. If your hens eggs suddenly start looking dull, pale, or thin shelled in an otherwise healthy flock there is a strong possibility that your chickens may have Egg Drop Syndrome 76 if no other symptoms of other diseases are present.
Symptoms of Egg Drop Syndrome 76:
Symptoms of Egg Drop Syndrome 76 begin with a dull appearance of eggs days before eggs then appear as pale shelled eggs. As the condition progresses, hens then begin to lay soft shelled eggs and then it progresses to hens laying eggs with no shell. Chickens tend to eat their thin shelled eggs or eggs hatched without a shell and oftentimes, soft or shell-less eggs get trampled into the birds litter and often go unnoticed unless you are looking for them.
Loss of egg production-Usable egg production tends to drop by 10%-40% as Egg Drop Syndrome 76 progresses.
Hens appear distressed or depressed.
Feces often appear watery.
"Although it has been shown experimentally that eggs usually continue to be produced at a normal rate (so the disease name may be a misnomer), the number of useable eggs produced falls by 10%–40%. Egg production by the flock usually returns to normal. In flocks in which there has been some spread of virus and some of the birds have antibody (usually 10%–20%), the condition is seen as a failure to achieve predicted production targets; careful examination shows that these flocks experience a series of small group episodes of infection and disease. Birds with antibody slow the spread of virus.
There is no effect on fertility or hatchability of those eggs with a shell quality that is satisfactory for setting.
Poor egg shell quality at peak production in healthy hens should also raise strong suspicion of classical EDS ’76. With endemic or sporadic EDS ‘76, disease can develop in laying hens of any age.
In cage units, spread can be slow, and the signs may be overlooked or perceived as a small depression (2%–4%) of egg yield." (Merck Vet Manuel, 2020).
You can tell the difference between EDS '76 and Newcastle disease, Influenza virus infections and infectious bronchitis by the absence of other symptoms of those diseases and the absence of respiratory distress, absence of ridged or malformed eggs, and absence of poor internal egg quality. You should consult your local poultry vet for laboratory testing and confirmation for a definitive diagnosis.
Treatment for Egg Drop Syndrome 76:
There is no treatment for EDS ’76 but vaccination for prevention are available (contact your poultry vet). However, you can slow the spread by washing and disinfecting egg trays before use, and separating infected chickens from other birds.
Do not keep chickens with ducks or other waterfowl.
Keep feed dishes, water dishes and coop clean and disinfected. Make sure water is clean and chlorinated before use.
"The classic form has been eradicated from primary breeders. Use of dedicated equipment and egg trays for each farm, and/or washing and disinfecting plastic egg trays before use, can help to control the endemic form. The sporadic form can be prevented by separating chickens from other birds, especially waterfowl. General sanitary precautions are indicated, and potentially contaminated water should be chlorinated before use.
Inactivated vaccines with oil adjuvant are available and, if properly administered, successfully prevent the disease.
Symptoms of Egg Drop Syndrome 76 begin with a dull appearance of eggs days before eggs then appear as pale shelled eggs. As the condition progresses, hens then begin to lay soft shelled eggs and then it progresses to hens laying eggs with no shell. Chickens tend to eat their thin shelled eggs or eggs hatched without a shell and oftentimes, soft or shell-less eggs get trampled into the birds litter and often go unnoticed unless you are looking for them.
Loss of egg production-Usable egg production tends to drop by 10%-40% as Egg Drop Syndrome 76 progresses.
Hens appear distressed or depressed.
Feces often appear watery.
"Although it has been shown experimentally that eggs usually continue to be produced at a normal rate (so the disease name may be a misnomer), the number of useable eggs produced falls by 10%–40%. Egg production by the flock usually returns to normal. In flocks in which there has been some spread of virus and some of the birds have antibody (usually 10%–20%), the condition is seen as a failure to achieve predicted production targets; careful examination shows that these flocks experience a series of small group episodes of infection and disease. Birds with antibody slow the spread of virus.
There is no effect on fertility or hatchability of those eggs with a shell quality that is satisfactory for setting.
Poor egg shell quality at peak production in healthy hens should also raise strong suspicion of classical EDS ’76. With endemic or sporadic EDS ‘76, disease can develop in laying hens of any age.
In cage units, spread can be slow, and the signs may be overlooked or perceived as a small depression (2%–4%) of egg yield." (Merck Vet Manuel, 2020).
You can tell the difference between EDS '76 and Newcastle disease, Influenza virus infections and infectious bronchitis by the absence of other symptoms of those diseases and the absence of respiratory distress, absence of ridged or malformed eggs, and absence of poor internal egg quality. You should consult your local poultry vet for laboratory testing and confirmation for a definitive diagnosis.
Treatment for Egg Drop Syndrome 76:
There is no treatment for EDS ’76 but vaccination for prevention are available (contact your poultry vet). However, you can slow the spread by washing and disinfecting egg trays before use, and separating infected chickens from other birds.
Do not keep chickens with ducks or other waterfowl.
Keep feed dishes, water dishes and coop clean and disinfected. Make sure water is clean and chlorinated before use.
"The classic form has been eradicated from primary breeders. Use of dedicated equipment and egg trays for each farm, and/or washing and disinfecting plastic egg trays before use, can help to control the endemic form. The sporadic form can be prevented by separating chickens from other birds, especially waterfowl. General sanitary precautions are indicated, and potentially contaminated water should be chlorinated before use.
Inactivated vaccines with oil adjuvant are available and, if properly administered, successfully prevent the disease.
- Vaccines can reduce but do not prevent virus shedding.
- Vaccines are given during the growing period, usually at 14–18 wk of age, and can be combined with other vaccines, such as those for Newcastle disease.
- Sentinel chickens may be placed along with vaccinated chickens and periodically checked for antibodies, which would allow detection of the presence of virus in the flock. (Merck Vet Manuel)".
Testing hens for Egg Drop Syndrome 76:
Searching for evidence of seroconversion is the easiest diagnostic approach for nonvaccinated flocks.
"Experiments were carried out to study the epizootiology of the egg drop syndrome 1976 virus infection in chickens that were not adequately protected by vaccination. Virus excretion was demonstrated when chickens vaccinated at the recommended level were challenged within 10 days of vaccination and when chickens were challenged 6 weeks after administration of low doses of vaccine. In the latter experiment, those chickens which shed virus had all shown a poor haemagglutination inhibition antibody response to vaccination but had high serum neutralisation antibody titres when challenged" (Cook, Jk).
Searching for evidence of seroconversion is the easiest diagnostic approach for nonvaccinated flocks.
- When selecting birds for diagnosis, especially in cage units, it is important to target hens that have produced affected eggs, because if the problem is due to EDSV infection, these hens will already have seroconverted.
- A hemagglutination-inhibition test using fowl RBCs, and ELISA, are the serologic tests of choice.
- In addition, the serum neutralization test can be used for confirmation.
- The double immunodiffusion test also has been used.
- PCR-based tests and antigen capture ELISA tests have been used to detect EDSV DNA and antigen, respectively.
- EDSV can be isolated by inoculating embryonated duck or goose eggs or duck- or chick-embryo liver cell cultures. It is important to select recently infected birds for testing, but these can be difficult to identify, especially if the birds are on litter. An easier method is to feed affected eggs to antibody-free hens. These hens can then be tested for seroconversion after the first abnormal eggs are produced, or tested for evidence of EDSV DNA or antigen by PCR or antigen capture ELISA, respectively, or virus isolation can be attempted from the pouch shell gland of these hens
"Experiments were carried out to study the epizootiology of the egg drop syndrome 1976 virus infection in chickens that were not adequately protected by vaccination. Virus excretion was demonstrated when chickens vaccinated at the recommended level were challenged within 10 days of vaccination and when chickens were challenged 6 weeks after administration of low doses of vaccine. In the latter experiment, those chickens which shed virus had all shown a poor haemagglutination inhibition antibody response to vaccination but had high serum neutralisation antibody titres when challenged" (Cook, Jk).
References::
Overview of Egg drop syndrome 76. Merck Vet Manual. Retrieved on November 13, 2020 from https://www.merckvetmanual.com/poultry/egg-drop-syndrome-76/overview-of-egg-drop-syndrome-76-in-poultry#v3343835
Cook JK. Egg drop syndrome 1976 (EDS-76) virus infection in inadequately vaccinated chickens. Avian Pathol. 1983;12(1):9-16. doi: 10.1080/03079458308436144. PMID: 18766758.
Overview of Egg drop syndrome 76. Merck Vet Manual. Retrieved on November 13, 2020 from https://www.merckvetmanual.com/poultry/egg-drop-syndrome-76/overview-of-egg-drop-syndrome-76-in-poultry#v3343835
Cook JK. Egg drop syndrome 1976 (EDS-76) virus infection in inadequately vaccinated chickens. Avian Pathol. 1983;12(1):9-16. doi: 10.1080/03079458308436144. PMID: 18766758.
