Mareks in vaccinated chickens, or something else?

[ChickenBrittle]

We recently lost one of our chickens after fighting for a couple weeks trying to get her right. We did antibiotics and eventually tube feeding as she would not eat or drink. We had a necropsy done and the preliminary guess is Mareks, but they sent the panels off and it will be another few weeks before they know anything for sure.

We noticed her issue more than 2 weeks ago at this point, and no other bird is showing anything usual behavior wise or looks wise. We are hoping that whatever was wrong was not contagious and is not going to hurt the rest of the flock. Our entire flock was vaccinated for Mareks as chicks.

Below is the necropsy report that came back this morning. I was hoping some experienced eyes could take a look at this while we anxiously await for lab results.

History
When noticed was sick, swelling in front of eyes, lethargic, lost weight. Gave antibiotic injection 2x/day for 1week. No improvement. Picked very little at food then stopped. Started tube feeding. No improvement, became more lethargic w/comb looking even more pale and dry, weak. No other birds have shown any symptoms or decreased appetite.

Necropsy​

Gross Pathology
Presented for necropsy is a 1028gm, 2 years old breed Salmon Faverolle hen in poor nutritional condition and good postmortem condition. The breast muscles are shrunken and the keel is prominent. The BCS is 4/9. The eyelids were swollen. There is very little subcutaneous and visceral fat. The feathers are clean. The air sacs are clear. The crop contains no mash and feed. The feet and joints are normal. The venctriculus contains little ingesta. The GI tract is long and appears normal with a tan serosa. Her jejunum contains semi firm green feces (no worms or blood noted). The duodenum contains green liquid feces, and the cecum contains some semi-firm green to brown feces.

The kidneys are maroon and appear normal. The liver is enlarged, hard and firm to touch, shows pan tan too range areas on its right lobe and has small white to grayish-white tubercular nodules in its parenchyma. The spleen is pale and enlarged. The lungs are pale, and filled with fluid and sink in formalin. The trachea lumen is patent and appears normal. The mouth contains mucus. The heart is maroon and appears anatomically normal.

The sciatic nerves are small and symmetrical. The oviduct is small. The ovarian clusters are inactive. The brain is pale.



GROSS FINDINGS: BCS 4/9; liver enlarged with tubercles on its parenchyma, spleen enlarged and pale, lungs edematous and filled with fluid, swollen eyelids and infraorbital sinuses.



Comments: We suspect it to be a cause of Mareks disease. The liver is enlarged with tubercles on its parenchyma, spleen enlarged and pale, lungs edematous and filled with fluid. Histology will help confirm the lesions and help to rule out if the condition is neoplastic or infectious.

 

[azygous]

There are multiple strains of Marek's, not all of them covered by the vaccine, which does not prevent Marek's, but only promotes resistance. It's still a possibility for vaxed chickens to get Marek's.

However, my money is on ALV, otherwise known as lymphoid leucosis, very similar to Marek's and not covered in the vaccine. The enlarged liver with the precancerous lesions is the signature finding for this virus. The lack of nerve damage in the sciatic nerve also points to ALV.

 

[ChickenBrittle]

So the report came back and it was indeed Marek's. None of the other chickens have shown any symptoms or have any issues.

Since the Marek's vaccine promotes resistance and doesn't provide a full immunity, does this mean that the rest of the birds may be safe?