Why did my chicken die?

Written by Sue Clarke. Provided by New Zealand Lifestyle Block, incorporating Growing Today, magazine.

When chickens fall sick and/or die, the small flock poultry keeper often puts it down to one of three things: if it has faeces-stained vent feathers, it's worms; if the bird was lame, it's Mareks disease; if it was a sudden death, it's because they can!

If the cause is a bacterial or viral disease it's difficult to know which one, as many have similar symptoms. Many poultry diseases are present in NZ and probably sweep through 'backyard flocks' virtually un-noticed, and certainly undiagnosed.

Without a post mortem, sending samples to a laboratory, and/or investigation by a poultry specialist, the cause of deaths in your poultry is probably due to one of a great range of disease organisms.

The following common diseases cause a lot of the unexplained deaths you will see in your flock.

1. Coccidiosis
This is caused by a parasite which invades the gut and causes symptoms such as blood in the faeces (although not always), and is a common killer of young birds.

The other major parasites - worms, lice and mites - can cause severe debilitation, especially in young birds, but do not cause death unless the bird already has a compromised health status.

2. Infectious Bronchitis
A common respiratory virus, Infectious Bronchitis (IB) can be transmitted on the wind, in dust, and in feather particles from up to two kilometres away.

Sometimes it manifests with respiratory symptoms, but in young chicks it can cause kidney damage with symptoms of white, urate-stained vent feathers, then death, or in older laying birds with wrinkled, misshapen eggs and watery whites.

Other viral diseases with respiratory symptoms are Infectious Laryngotracheitis (ILT), where sneezing, coughing with blood-tinged mucus, and some deaths occurs. This is more common in the warmer regions of the country, from the Waikato north.

3. Mycoplasma
Mycoplasma is another disease causing respiratory distress, sneezing, and swelling sinus around the eyes and nose. Most birds in the country will test positive for mycoplasma, having been exposed to it from infected parents.

4. Infectious Coryza
This is a bacterial infection involving respiratory signs, and is also pretty common. Both mycoplasma and infectious coryza cause depression and sickness, but are not as likely to cause sudden death.

5. Fowl Pox
This is a virus spread by insect bites to the comb and face, and is a problem in areas north of about Lake Taupo where biting insects are important in the spread of disease. Birds moving to regions further south while they are incubating the disease may unwittingly transport it.

There are two forms: dry pox is characterised by scabby lumps on the comb, wattles and face. Wet pox has the lumps inside the mouth and throat, and is more likely to result in death through suffocation.

6. Fowl Cholera
Also known as Pasturella, this bacterial disease is far more common than you might expect. Spread by wild birds and rodents, it can appear as sudden deaths around point of lay (as young birds begin to lay), with birds losing condition.

Sensible commercial free range farmers vaccinate their birds at point of lay, as Fowl Cholera is easily spread.

7. Necrotic Enteritis
This is caused by clostridial bacteria, and is often a secondary invader after another intestinal disease such as Coccidiosis.

It can arise from mouldy feed, or by moulds which grow in feed troughs when wet mash is fed, then left to harden and cake the trough. Yellowish diarrhoea and birds in poor condition may be the only signs. You may think it is worms, but will find a worm treatment does nothelp.

8. Erysipelas
Erysipelas is a disease usually associated with turkeys, but it has cropped up in free range poultry flocks more frequently in recent years.

It affects native birds like weka and takahe, as well as pigs and sheep. It causes post-dipping lameness in sheep, and post docking arthritis in lambs; having chickens and sheep together increases the risk.

It is characterised by sudden deaths, usually in young birds; on post mortem there are haemorrhages around the heart. It is a very resistant bug which remains in the soil for long periods, and enters via small cuts in the mouth and skin.

9. Marek's disease
Although often fatal, Marek's doesn't tend to cause sudden death.

The number affected in an unvaccinated flock can be as high as 60%. Once infected, mortality is high, reaching nearly 100% over a 10-week period.

Vaccinated flocks (if you have ex-commercial layer hens they will be vaccinated) do fare better, with less than 5% affected. Pullets are more likely to be affected than cockerels.

Marek's is a highly contagious virus caught by chicks in their first weeks of life from older birds. It has an incubation period of 3-4 months, manifesting with visible symptoms when birds are about 15-25 weeks of age, mainly as lameness, but also as blindness, wasting, scouring, bleeding sores which don't heal, or enlarged feather follicles.

Lame birds can sometimes recover, giving them immunity, although they cannot pass this immunity on. However, resistant birds (that don't contract it) can pass on their resistance to their chicks.

Can you save them?

Many of the diseases mentioned cannot be treated, although antibiotics - prescribed by a vet - may be of some use in cases of bacterial infection.

Isolation from other birds in a draft-free pen with access to clean water, perhaps with added vitamins suitable for birds (obtainable from pet shops) and nutritious feed, is the best you can do for a sick bird.

Have lots of birds died?

If you suddenly have lots of dead birds in mysterious circumstances it might be worth thinking of the exotic diseases we still don't have in NZ. An outbreak of Avian Influenza, Newcastle Disease or Infectious Bursal Disease could be as devastating to New Zealand's poultry industry as Foot and Mouth would be to the sheep, cattle and pig industry, not to mention the hundreds of unique native birds we have in NZ.

You can report them to the emergency disease hot line 0800 80 99 66 run by MAF Biosecurity NZ.

How to avoid importing disease

• Buy from a reliable person whose practices are hygienic, and whose birds exhibit signs of good health.
• Keep age groups separated for as long as practicable, so young birds gain some immunity before mixing with adult birds.
• Do not introduce birds from a different source to your flock until they have spent at least two weeks in isolation first.
• Make sure feeding and drinking equipment is kept clean and free from mould and algae.
• Try not to visit everyone else's chickens and then come back to your own wearing the same footwear and clothes - diseases are easily spread this way. Commercial poultry reps will change clothes, have showers and carry disinfectant with them to avoid the possibility of carrying diseases from farm to farm.
• Try to keep wild birds, especially sparrows and starlings, from getting into the poultry feed. Set rat/stoat/ferret traps, and use bait stations around the boundaries of your shed or chicken run.

This article was provided by NZ Lifestyle Block, incorporating Growing Today magazine.
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