What we can learn from 2687 autopsies
STUDY: Causes of Mortality in Backyard Poultry in Eight States in the United States
YEAR: 2019 WEB: pubmed.ncbi.nlm.nih.gov/31084344/ This study looked at autopsy results from 2015-2017 from diagnostic labs in Hawaii, Texas, Georgia, South Carolina, Pennsylvania, Iowa, Colorado, and California, to understand the common causes of death in backyard chickens.
While this data is interesting and useful, poultry expert Sue Clarke says it’s important to note the US has diseases that aren’t in NZ.
“They have avian influenza outbreaks, Newcastle disease, and infectious bursal disease (IBD, also known as ‘gumboro’). These all badly affect the immune system, and mean birds are wide open to any other infections going, so this data may be different from what you’d get if you did something similar in NZ.”
The study found the primary causes of death fell into five categories. Nb: total bird numbers are more than 100% as some birds had more than one issue.
Neoplasia (42%)
This is the uncontrolled, abnormal growth of tissue or cells, either benign (not cancer) or malignant (cancer). It was the most common primary diagnosis, involving 42% of the total birds autopsied.
Of these, 63% were diagnosed with Marek’s disease or leucosis, both malignant cancers induced by a virus.
There were 414 cases (36%) of neoplasia not attributed to a virus. The most common was ovarian cancer.
Viral (7%)
Infectious bronchitis was the most commonly detected virus (81 birds), followed by infectious laryngotracheitis virus (39 birds).
Non-infectious (27%)
These deaths were the result of management-related, nutritional, and metabolic diseases in backyard flocks. Common causes included:
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incorrect or inadequate diet (10% of all deaths in this category), eg too low in protein and/or crucial amino acids, too high in calcium, overfeeding causing fatal liver haemorrhages;
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starvation and/or dehydration;
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inadequate housing, eg too hot, cold, humid;
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poor husbandry, ie no or inadequate protection from predators, access to toxins (eg lead in soil, poison rodent bait, botulism in compost pile).
Bacterial (42%)
Of the 1135 birds with bacterial infections, the most common was E. coli detected in 34%, followed by Mycoplasma gallispeticum (26%) and other similar bacteria. All cause chronic respiratory disease.
Associated reproductive diseases were diagnosed in 30 of the affected birds, including peritonitis, salpingitis, vent prolapse, and egg-laying abnormalities.
What is mycoplasmosis?
Also known as: Mycoplasma gallisepticum (MG) infection,
CRD (chronic respiratory disease)
A chronic respiratory disease caused by the bacteria, Mycoplasma gallisepticum. Most birds in NZ will test positive for it as it's widespread, and many birds have no symptoms. It's most severe in chicks aged 4-7 weeks as they have an immature immune system, and in adult birds suffering from another illness.
Symptoms: nasal discharge, sneezing, swelling in the sinuses around the eyes and nose, watery eyes, low appetite, lameness due to swollen hocks or footpads.
Treatment: Offer supportive care. Antibiotics may help if birds get a secondary infection.
Parasitic (28%)
Coccidiosis was the most common cause, accounting for almost a third of deaths in this category. Nearly half were birds under the age of 4 months. A quarter of birds were affected by more than one parasite.
Also known as:
cocci (‘cocksy')
Coccidiosis is the most common killer of young chicks in their first few weeks of life, especially at the 4-6 week mark.
Coccidia are gut parasites that cause coccidiosis. Their eggs (oocysts) are easily transported, even on the feet of flies. They thrive in hot, wet conditions like those you commonly find in a brooder.
Chicks need gradual exposure so they can develop an immune response. Medicated starter feed (containing a preventative coccidiostat) for the first 6 weeks retards but doesn't entirely prevent the growth of coccidia they ingest. This helps chicks avoid a potentially fatal infestation but gives them enough exposure for their immune system to respond. However, medicated feed won't stop chicks getting sick if they're exposed to a sudden, large infestation.
Check chicks regularly throughout the day as it's crucial to catch any sign of infection as early as possible.
bloody droppings; standing with their eyes closed,
Symptoms:
cold feet.
Treatment:
Have coccidiosis medication on hand before you need it. If you see symptoms, treat all chicks immediately or they can die very quickly (within 24 hours). The best options are Coxiprol and Baycox, available online, at some pet stores, and from your vet.