A Family Guide To Keeping Chickens (48 page)

Although Ivermectin can be purchased under the Small Animal Exemption Scheme for non-food producing animals, it isn’t licensed (as it hasn’t undergone full clinical trials) for chickens. Vets may prescribe it using their clinical judgement but there will be a withdrawal period when eggs cannot be eaten.

Recognizing Infectious Diseases

This is only intended as a brief guide to some of the most common or important diseases. Although it’s useful to know the symptoms, only a vet can give an accurate diagnosis and prescribe antibiotics if necessary. If several birds are affected by a condition, or there are a number of unexplained deaths, veterinary advice should be sought without delay.

This very infectious respiratory disease can appear within a few days of being contracted. Symptoms are foamy eyes, swollen sinuses, rasping breath and sneezing. There is often a sickly smell. Another strain of the disease produces hot and swollen joints.

Mycoplasma can prove fatal to some chickens, while others in the flock may show few signs. Antibiotics administered in the initial stages can help aid recovery.

Birds that recover are liable to further attacks and will remain carriers of the disease. If young stock is introduced to a flock that carries mycoplasma they are likely to become infected, even though the older birds remain apparently healthy.

Mycoplasma can be transmitted by poultry or wild birds – stress is often the trigger. The disease is able to survive for several hours on clothing and poultry equipment. It can also be present in hatching eggs. There is a vaccine.

Mycoplasma

There are several types of respiratory disease and more than one can be present – a blood test may be required to determine the cause or causes of the symptoms.

Signs are similar to mycoplasma, but the disease spreads rapidly through the entire flock. Following the respiratory symptoms, there may be kidney damage and infection of the reproductive organs. This will be revealed in soft-shelled or misshapen eggs, and the bird will remain a carrier of the disease.

Damage to the oviduct can also result in eggs descending into the abdomen, leading to egg peritonitis.

The virus is killed by disinfectant so good hygiene and keeping stress to a minimum are preventative measures. There is a vaccine, which must be given when the birds are young.

In humans this disease is known as ‘farmer’s lung’ and is caused by fungal spores in mouldy hay, straw or bark. Signs are breathlessness, lethargy and thirst, but the disease shows few symptoms until it is advanced. Successful treatment is difficult.

Young bird with Coccidiosis

Coccidia eggs (oocysts) are picked up by the bird and develop in the gut. They multiply rapidly and feed in the intestine, causing destruction of the gut walls. Eventually more oocysts are passed in droppings to continue the cycle.

The disease often proves fatal, especially in young birds. Older chickens (apart from ex-battery hens) have frequently been exposed to low levels of infection, giving them some immunity, but can still be at risk in certain conditions.

The birds stop eating, and become hunched and miserable, with ruffled feathers. There is often watery diarrhoea, which may be white or have blood in it. Immediate veterinary attention will be required.

The vet can prescribe treatments but prevention is better than cure. Traditionally, chicks have been given feed containing a coccidiostat but a vaccine is now available. Check when buying young birds that they have been protected against coccidiosis.

Good husbandry is essential too. The oocysts can be transmitted on boots and clothing, and are very resilient to the usual disinfectants. They are killed by extremes of temperature but can survive for long periods in empty housing.

Warm, humid conditions (e.g. a brooder or shed with damp bedding) are ideal for the oocysts to enter the first stage of their development. When eaten by a chicken, they will be ready to start multiplying.

Indoor birds are most at risk – bedding must be kept clean and dry. Standing drinkers on wire mesh helps to keep the birds out of wet floor litter. Make sure feeders and drinkers are free from droppings and cleaned regularly.

Good ventilation helps to avoid humidity. Stress factors, such as overcrowding, will encourage disease.

Use a product designed to kill coccidia oocysts before moving new chickens into housing previously occupied by other birds. The ground is also liable to contamination and should be treated with a suitable sanitizing agent if birds can’t be regularly moved.

This herpes virus is usually seen in young birds, especially pullets coming into lay. Stress is particularly likely to cause the virus to surface. The usual signs are
birds becoming thin and weak, with lameness leading to paralysis of legs and wings. Sometimes birds die suddenly without any obvious symptoms. Affected birds should be culled – there is no cure and any birds that do survive will remain carriers.

The virus is mainly passed on via feather debris and can survive for at least twelve months in henhouse dust. Some breeds are particularly susceptible to this disease (e.g. Silkies and Sebrights) but chicks can be vaccinated.

Marek’s disease

Although rare in the UK, this is included because it’s a notifiable disease – an outbreak must be reported to DEFRA. Apart from being fatal to chickens, it can cause flu-type symptoms and conjunctivitis in humans.

The most obvious indication is a large number of deaths in the flock. Other signs are varied and include respiratory symptoms, severe diarrhoea or paralysis where the neck twists. Laying may suddenly decline, with a high proportion of soft-shelled eggs.

If you think your birds may have contracted Newcastle disease, or experience many unexplained deaths, you should contact your vet immediately.

The disease can be carried by wild birds, especially pigeons, and also on clothing. There are disinfectants that will destroy the virus and there is a vaccine.

This is another notifiable disease, causing numerous deaths in birds and potential infection in humans. Symptoms vary from mild to severe, and may include respiratory problems, swollen heads, dark combs and wattles, diarrhoea, lethargy, not eating and a sudden drop in egg production. There will be many sick and dying birds.

The disease can be carried by waterfowl, although they may show few signs, and is mainly spread via droppings. There is currently no vaccine available, although the virus can be destroyed by certain disinfectants.

Inform the vet immediately if you suspect avian influenza or if there are a number of unexplained deaths.

This rarely causes illness in chickens but can cause severe diarrhoea and vomiting if passed to humans. Commercial flocks are routinely vaccinated and tested. Small flocks can also be tested by means of a droppings sample. Maintaining good hygiene in the kitchen will minimize risks.

Heart Disease