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Signs are disheveled feathers, lameness, swollen hocks and feet, and sudden death in severe infections.  Antibiotics will help in some cases that haven’t advanced to blood poisoning.   To prevent the bacterial infection practice good hygiene, vaccinate the brood stock against reovirus infection, keep the flock’s stress levels down, and on a steady diet.   Probiotics from products like yogurt can help reduce the numbers of the bad bacteria in the digestive system.  There is no known effective vaccine but surviving birds are somewhat immune after an infection.

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The disease can strike so rapidly that there are no real observable symptoms other than dying birds.  Like most other viral disease the mortality depends upon the strength of the virus strain.   The main infection vector is wild birds that carry the virus without appearing sick, indeed they might not be sick.

Signs or symptoms include ruffled feathers, depression or listlessness, a drop in egg production, soft shelled eggs, poor appetite, purple coloring on the wattles and comb, swelling of the head, eyelids, combs, wattles, and  feet, diarrhea, bloody discharge from nostrils, inability to walk or stand, bleeding feet or leg shanks, respiratory symptoms, and large numbers of seemingly healthy birds dying.

The virus will mutate, sometimes getting milder as it spreads between flocks, sometimes becoming more virulent.  Chickens are not the preferred host for Avian Influenza so the virus has to mutate to survive and in that process it can become quite lethal and contagious.  Infected birds spread the virus in their feces and from nasal discharges that can contaminate feeders and waterers. Once infected the chickens are carriers for life.  The virus can survive in the water and mud where infected wild ducks are present and can remain outside a host for long times and are not harmed by freezing temperatures.  People and contaminated equipment can also spread the virus so nothing should be moved into your flock without through disinfection and cleaning.

Wild bird proof treadle chicken  feeder

The poultry industry considers backyard flocks as the greatest threat to their industry.  There is little to no biosecurity in home based flocks and they have much greater risk of becoming infected and people tend to not think about buying a new bird and bringing it into their flock.  Commercial poultry usually is brought in and removed in an all in/all out fashion with much tighter controls on biosecurity and the genetics of the brood stock.   

Free range birds will be nearly impossible to provide biosecurity but cooped birds should have the cooped bird tight, have all feed in treadle feeders, and use the nipple style water dispensers hung out of reach of wild birds.   As the virus is easily spread through fecal matter allowing wild birds to congregate is enough to contaminate your flock.  However, most wild birds have to work hard and long to feed themselves so keeping the feed away from the wild birds in a wild bird proof chicken feeder will mean very few birds will stick around long enough to leave droppings behind.

Neurological Newcastle Disease

The birds will appear depressed, have poor appetite, and egg production might stop completely. Eggs might have abnormal surface texture, color or shape.  Mortality is high with Newcastle disease, as high as 100%.  Vaccinated bird might not show the symptoms other than egg production slowing but they will be carriers and shed the live virus while the disease runs it course.   Body and head tremors are signs of a vaccination that didn’t quite take but those birds have a mild form of the disease and might recover with some nursing.

Vaccines for turkeys and chickens are available but they serve to  produce antibodies, not full immunity, but will lessen the effects of the disease.  Mass vaccination can be done through the drinking water but it can be less effective at ensuring all birds received a dose of the weakened or inert virus.

Vaccinating chicks after hatching is good but waiting a few weeks for the maternal antibodies to drop off is more effective.  Some chicks will have a reaction to the vaccine due to bacteria colonies in their lungs or digestive system.

Mushy Chick infected chick

The signs are listlessness, closed eyes, no appetite, diarrhea, pasty poop on the chickens vent area, and a swollen stomach.  Once infected the chicks are probably going to die in less than one week and antibiotics are of limited use as it is a systemic infection, not localized.

The best preventative measures re sanitation and hygiene from breeding flock right through hatching and hardening the chicks off.  Eggs that are extremely soiled with manure are more likely to pass the bacteria on to the yolk inside the egg. Culling is the most humane thing to do with a mush chick.  If you don’t have the heart to snap it’s neck use a ziplock bag and put the chick in the freezer to end its misery.

Pullorum diseased chicks

.  Treatment by Amoxycillin, poteniated sulponamide, tetracylines, and fluoroquinolones.

Surviving birds are carriers of the bacteria and should not be used for breeding stock.  The birds will be immune from future infections but will pass the disease down through their eggs and contaminate other birds.  Vaccines are not recommended as the carriers should be put down to stop the spread of the disease.

Air Sac Disease

If a bird comes down with CRD expect the cause to be stress caused by overcrowding, poor sanitation, wet litter, parasites, or poor feed.  The symptoms will be watery eyes, breathing difficulties, weight loss, green mucus in the droppings and even death.
 Mycoplasma synoviae (MS)

Is an infections with symptoms of arthritis, synovitis and bursitis in hens and turkeys.  The birds will show signs of being lame, tired, and slow growth.   Mortality rates are low, around 10% and young chickens and turkey poults are susceptible.   Wet litter can exacerbate the symptoms.    The birds become more and more exhausted as the disease progresses.  The cause is M. synoviae, a microorganism that can be transferred through respiratory means. 
Keeping birds in sanitary conditions and keeping wild birds, rats, mice, and other rodents away from the flock will go a long way in minimizing the amount of disease you have to deal with.  Hybrid birds will be more vigorous and healthy than pure breed birds and biosecurity is an absolute must if you want to minimize the chances of contagion.

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Signs of infection are listlessness, poor appetite, slow growth, diarrhea, white plaque in the mouth, throat, and around the vent.  It can be treated with Nysatin at the rate of 100 ppm in the feed for seven to ten days, copper sulphate at a rate of one kg per ton of feed for five days, or copper sulphate at a rate of 1 gm per liter of water for three days.  This is a fungal yeast so antibiotics isn’t going to help.   Good sanitation,  copper sulphate at 200 gm per ton of feed fed continually or till fifteen weeks of age will ensure the disease is knocked down.

You can control the yeast by adding 5 ppm of Clorox or sodium hypochlorite, or using chlorinated tap water.

Mareks Disease paralysis

Usually spread through respiratory means and also dander from infected feather follicles.  The surviving birds remain carriers for life.  The virus is quite hardy, surviving outside of a host for over a year and resistant to ammonia and phenol based disinfectants.  It easily survives freeing and thawing.
Signs of Mareks disease are paralysis of the legs, wings, and neck, loss of weight, grey or irregular pupils, partial blindness, skin around feather follicles is rough and raised.  .Prevention depends upon biosecurity, sanitation and hygiene, all in and all out production where possible, purchasing resistant strains, and vaccination.  Once again a good bird proof treadle feeder is a must.

Mareks paralysis

.  That also means not relying upon disinfectants other than lime to expose the birds to all sorts of bacteria and viruses.   Good nutrition, clean and un-crowded coops are a necessity if you attempt this route.  Deliberate exposure to disease rather than attempting biosecurity and allow the fittest to survive.

Purebred animals are always less vigorous and less hardy and that extends to disease as well.  Deliberately exposing the birds instead of biosecurity, antibiotics, and coddling the flock is the only possible way to breed resistance into the flock.  Any surviving birds will be the most resistant to the disease and should be used as the brood stock for future generations.