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Game Bird Diseases

GB_DISEASE_SURVEILLANCE_JULY_2015

GB_DISEASE_SURVEILLANCE_JUNE_2015

GB_DISEASE_SURVEILLANCE_MAY_2015

GB Disease Surveillance Monthly Report May 2014

GB Disease Surveillance Monthly Report June 2014

GB Disease Surveillance Monthly Report July 2014

GB Disease Surveillance Monthly Report August 2014


Aspergillosis
Caused by the inhalation of fungal spores. The disease affects the respiratory tract and may occur in day-old chicks due to hatchery contamination. It can also occur in older birds due to spores on mouldy straw and hay. There is no treatment for this condition.

Ataxia Syndrome
Affects Pheasants. The cause is unknown but may be viral in origin. Affected birds remain alert but show in-coordination. Incidence on a shoot is generally low. No treatment available.

Avian Influenza
A viral disease causing very high mortality (Fowl Plague). It is a notifiable disease.
There is no treatment and no vaccine is available in the UK for this condition.

Blackhead – see Histomoniasis

Bumblefoot
A swelling of the foot pad due to Staphylococcal bacterial infection. The treatment of individual birds is often not effective.

Coccidiosis
There is at least three different types seen in Pheasants and three in Partridges affecting the intestinal tract. It is controlled by feeding coccidiostats to younger birds. The disease occurs as a result of decreased feed intake, overwhelming infection or management failures.

Colibacillosis
E.coli causes secondary bacterial infections, particularly in younger birds. Results in poor growth rates and can cause high mortality. May be treated with antibiotics.

Coronavirus
A viral disease that can cause respiratory disease or kidney damage. Kidney damage is particularly severe in breeding birds. Strains of the virus in game birds are often different from those in domestic poultry,

so poultry vaccines may be of limited value. There is no treatment available for infected birds.
Egg Peritonitis
Caused by egg yolks entering the body cavity. It can result in high mortality particularly in early lay. The exact cause of this condition is not fully understood. It may also be due to a specific infection such as Salmonella or Pasteurella. In these cases treatment may be beneficial.

Erysipelas
More commonly seen in older birds over 12 weeks old. It can cause sudden high mortality or lameness due to arthritis. Treat with antibiotics and prevent with vaccination. Can be caught by humans – take care!

Fleas

Blood sucking insects. In heavy infestations can affect bird performance.

Fowl Pox
A viral infection spread by biting flies. Can result in skin lesions or lesions within the mouth - the latter condition is usually fatal. No treatment, but vaccination is possible.

Gapes
Caused by the worm Syngamus trachea. The lifecycle of the worm is either direct or via earthworms so land can remain contaminated for many years. Seen particularly in birds in release pens. 

Gut Worms
A number of species may be present including Heterakis, Capillaria and Ascaridia.
Heterakis can carry the Histomonas (Blackhead) parasite. Capillaria can cause severe disease with loss of condition and egg production. Routine control of worms in breeding stock and in birds in release pens is advised.

Hexamita

Histomoniasis (Blackhead)
Caused by a protozoan parasite. Causes scour, loss of condition and deaths. Can be carried in Heterakis worms. No specific treatment available but can be prevented by worm control and good management practices.

Leucosis
A viral disease that causes tumours in older birds. Relatively rare in game birds. No treatment is available.

Lice and Mites

Biting and blood-sucking insects affecting the skin. Control can prove difficult.

Marble Spleen Disease

Causes sudden death. Due to an Adenovirus infection. No treatment or vaccine at present available.

Mycoplasma

A bacterial disease causing a respiratory infection and reduced egg output. Spreads between birds and via the egg. Clinical disease is often started by stress. Controlled and treated with antibiotics. Vaccination of limited use in game birds.

Newcastle Disease (Fowl Pest)
A viral disease that may cause nervous signs and high mortality. It is a notifiable disease and it can be prevented by vaccination. There is no treatment for affected birds.

Pasteurellosis

Can cause high mortality in birds of all ages. Rats act as a reservoir of infection. Can cause egg peritonitis in laying birds. Treated with antibiotics. Prevented by vaccination.

Pseudo-Tuberculosis
Caused by Yersinia pseudotuberculosis - a bacterial infection. Treated with antibiotics. No vaccine available.

Rickets
Soft bones in young birds. May be nutritional in origin.

Rotavirus
Viral infection that damages the gut lining in chicks between three and fourteen days old. Causes the chicks to scour and mortality may be up to 10%.

Salmonellosis
There are many types of Salmonella bacteria and most do not cause disease except in young birds under stress. Can cause disease in humans. Treated with antibiotics. Birds can be monitored for the presence of disease.

Scour
Due to a variety of infections and non-infectious cause

Spironucleosis (Hexamita)
Often seen in young birds with enteritis. Hexamita possibly does not cause disease by itself. Controlled by treating the underlying bacterial enteritis with antibiotics and re-hydration salts.

Starve-outs
Deaths in young chicks that fail to find food. Can be due to poor chicks and poor management. When significant levels are detected it is believed to be due to severe stress to the chicks in the first 24 hours of life.

Trichomoniasis
Often seen in young birds with enteritis. These protozoa may possibly cause disease by themselves but in most cases there is also an underlying bacterial enteritis. Controlled by treating the underlying bacterial enteritis with antibiotics and re-hydration salts.

Tuberculosis
Affected birds lose condition and eventually die. Usually a disease of birds two years old or more. No treatment available.   

Visceral Gout
Seen particularly in young chicks that fail to find water or in birds of any age that are moved and do not acclimatise. No treatment for affected birds.

Yolk Sac Infection
Causes mortality in chicks up to seven days old. Due to a variety of bacteria that affect the yolk sac of the chick at hatching. Regarded as a hatchery management problem.

DISEASES THAT CAN BE SPREAD FROM GAMEBIRDS TO HUMANS. (Zoonotic Diseases)

A number of bacterial diseases can be spread directly from game birds to humans. This may be either by people handling the birds, or the disease being present in the environment or on the equipment with which the birds have been in contact. Some of the diseases are comparatively rare and some may cause no clinical disease in the game birds but may cause serious disease in humans. In most cases, disease spread to humans can be prevented by good personal hygiene. The following are the most likely diseases to be caught by humans from game birds.

Avian Tuberculosis
Avian tuberculosis is usually seen in game birds over two years old. The organism that causes the disease, Mycobacterium avium, survives a long time in the environment and contaminates not only the environment but also equipment etc. Disease in humans is rare but cases have been recorded.

Campylobacteriosis
Campylobacter do not appear to cause disease in game birds and large numbers of Campylobacter bacteria can be present in the intestines of birds without them showing any clinical signs. Affected people will have diarrhoea, abdominal pain and nausea – the typical signs of food poisoning.

Chlamydiosis
( Ornithosis, Psittacosis). Chlamydia are bacteria-like organisms. They cause disease in a wide range of domestic birds including game birds and the disease can be particularly severe in ducks. In birds, signs of disease can be very variable, from little or no

obvious clinical signs to depression with eye and nasal discharges and scour. Infection in humans working with infected birds can be very serious, particularly in the very young and the aged. Clinical signs are most commonly severe ‘flu-like symptoms, and deaths in vulnerable people have been widely reported. Anyone working with birds who develops a severe ‘flu-like condition should tell their doctor about their connection with birds.

Escherichia coli (E.coli)
Most of the strains of E.coli that affect game birds are not of significance in human disease. However birds can carry strains of E.coli in their intestines that are infectious to humans (particularly strain 0157) without themselves showing any signs of disease. E.coli is spread in the faeces of birds so it is important that those handling them wash and disinfect their hands well after handling birds or anything contaminated by faeces

Erysipelas.
This bacterial disease causes rapid deaths in infected game birds and is seen most commonly in adults or those approaching maturity. In humans, the disease can cause skin lesions but in more severe cases infections of the heart and brain can result in fatalities.

Listeriosis.
This disease is very rare in game birds but young birds could pick up infection from contaminated soil. It is particularly likely to affect young birds either causing a generalized infection or specifically affecting the brain. In humans the disease could be caught from contact with infected birds.

Pasteurellosis
This disease can cause rapid deaths in game birds with adult birds being most commonly affected. In laying birds, egg peritonitis is often seen. Rats often spread the disease, so vermin control is important in the control of the disease. Disease spread to humans from birds is rare if the immune system of the human is working normally.

Salmonellosis
Many birds will carry Salmonellae in their guts without showing any signs of infection. Young chicks may die of a generalized infection caused by Salmonellosis but this is rare in older birds. However many Salmonellae cause disease in humans. Affected peoples will have diarrhoea, abdominal pain and nausea. Deaths due to Salmonellosis are not unknown.

In most cases, washing and disinfecting hands before eating or smoking and after handling birds can prevent bacterial diseases. Of particular danger is opening up infected carcasses with Erysipelas, Listeriosis and Salmonellosis. It is advised that dead birds should be submitted to your veterinary surgeon and not opened up by the stockperson. 
There are reports in the medical literature of other infections in humans by viruses and parasites that originated in birds. These are usually isolated cases, mainly from abroad, and if good hygiene is observed, then the danger of human infections from birds are relatively low.

ASPERGILLOSIS

Aspergillosis is caused by a fungal infection and results from the birds breathing in the fungal spores. It is more commonly seen in young game birds but lesions may also be present in older birds which have access to highly contaminated areas.
The fungus is found mainly on plant material and damp and warm conditions enhance its growth. In game birds poor quality bedding is the main source of infection – it should not be present on commercially produced bedding but chopped untreated straw of unknown origin is always a potential hazard.
In older birds bales of straw left as wind breaks and straw used in breeding pens are common sources of infection. In addition to bedding, mouldy food can be a significant source of infection. Large numbers of spores can be released at harvest by the combine harvester after a warm damp season but by this stage young game birds are less likely to be confined and significant levels of disease are rare.

Death is caused in young birds that have breathed in large numbers of the fungal spores when the fungus grows in the windpipe, lungs and air sacs of the birds. With lower levels of infection birds may survive but do not thrive. High mortality levels are less common in older birds where poor performance is more commonly seen.

There is no treatment available for infected game birds and antibiotics are contraindicated. The disease does not spread between birds so the control of an outbreak of disease depends on controlling the source of the infection. The disease can be prevented by carefully sourcing and storing bedding and feed and discarding any material that is excessively dusty or is mouldy.

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AVIAN INFLUENZA AND THE GAME BIRD INDUSTRY

High-pathogenic Avian Influenza is a highly lethal virus disease that can affect all species of birds but particularly domestic poultry and species such as game birds.

Symptoms in an individual bird may include nervous signs, depression, coughing, a swollen congested comb and wattles, hock haemorrhages and scour.

On a flock basis, symptoms of a highly pathogenic strain of Avian Influenza are dramatic.  The birds will be very quiet with decreased activity levels, decreased feed and water intake and decreased egg production. Most noticeably the disease will be sudden in onset, severe, short-lasting and with very high mortality.

The most likely route for the spread of the disease to the UK is via wild birds that act as a reservoir of disease. All bird species are susceptible but waterfowl are the most likely carriers and domestic poultry are particularly vulnerable to epidemics of the severe form of the disease.
Other possible routes for the spread of disease into the UK include both the legal and illegal trades in poultry, poultry products, game birds and wild birds. It is therefore important that all imports of birds and eggs are notified to DEFRA.

Once in the country the disease can be further spread by people moving between premises. The disease is transmitted by the secretions from infected birds. With close contact between birds, spread may be via secretions from the respiratory system. The disease can also be spread via the faeces, allowing rapid spread between water fowl through contaminated ponds and between sites on contaminated footwear. Hence, faecal spread can result in the disease being transmitted via contaminated feed, water, equipment and clothing.
Clinically normal carrier birds may introduce disease into flocks and as the disease may be transmitted via eggs, broken contaminated eggs may infect chicks in incubators.

Good biosecurity is therefore essential to prevent spread of the disease and good personal hygiene is important to prevent any chance of the disease being transmitted to bird handlers.

Good biosecurity also prevents the spread of many other diseases including Newcastle Disease, which is another notifiable disease like Avian Influenza that can cause high mortality in susceptible flocks of birds. 

DISEASE CONTROL:  The disease is notifiable and anyone suspecting that their birds have the disease must notify DEFRA immediately.

Under the ‘The Avian Influenza (Preventive Measures) Regulations 2005’ anyone with over 50 birds that are kept commercially and are confined for any period of time must register their premises with DEFRA. Most game farms and shoots will fall into this category.

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BLACKHEAD DISEASE (HISTOMONIASIS) IN GAME BIRDS

Blackhead disease is caused by the protozoan parasite Histomonas meleagridis usually acting with secondary bacteria to cause the lesions seen in birds at post-mortem examination.  The name ‘Blackhead’ for the disease is misleading as in game birds it causes no distinctive change to the colour of the head. The name originated from a discolouration of the head that was originally noted in turkeys affected with the disease.

The parasite lives in the caecae of the birds and can be carried by the caecal worm Heterakis gallinarum. In turn the larvae of the caecal worm can be carried by earthworms. Although Blackhead is primarily a disease of turkeys, both chickens and game birds can be affected. There are no drugs currently available to control the parasite, and although at present the disease is most common in breeding birds it can also affect birds in rearing and release pens.

The disease is caused by the parasite multiplying in the caecal walls. The bird may pick up parasites directly from the faeces of another infected bird but more usually the caecal worm, Heterakis, is involved. The Blackhead parasite can live in the caecal worm or its eggs for up to four years which protects the parasite from the environment. In addition the caecal worm larvae may be ingested and then protected by earthworms so once land is infected by this parasite they can be present for a considerable length of time even if there are no birds present. Once the parasite has been ingested by a susceptible bird, infection can result.

Although the oral route of infection is considered the most likely, it has been shown in turkeys that the parasite can enter via the cloaca when the birds are kept on dirty litter. There is no reason to suppose this cannot also occur in other species, so good hygiene plays its part in controlling the disease.

Affected birds become depressed, emaciated and pass light-coloured scour. Mortality levels in an affected flock can be significant. Post-mortem examination shows enlarged caecae and typical liver lesions.  There is no specific treatment for the disease but treatment for the secondary bacteria can be beneficial.

100% prevention of the disease is not possible in birds kept on grass. Regular worming to minimize levels of caecal worms is important in disease control as are good hygiene practices. Preventing the birds having to access to feed spilled on the ground together with giving the birds access to clean, dry areas are also important. The use of antibiotics to prevent the secondary infections can be beneficial in cases of disease but would not be recommended as a routine preventative measure.

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COCCIDIOSIS CONTROL IN RED-LEGGED PARTRIDGES

Although coccidiosis is seen in all species of game birds, we see far more clinical disease in red-legged partridges than in the other species. Anything in the rearing period that reduces a red-legged partridge’s intake of food medicated with Avatec ® is likely to result in increased levels of coccidial oocysts and possibly clinical disease.

Prevention of coccidiosis starts with recognising that oocysts are very hardy and survive easily from one season to the next in buildings, often in small cracks and crevices once the building has been cleaned out.  The oocysts are resistant to most common disinfectants so houses need to be disinfected with a product that is specifically formulated to destroy coccidial oocysts such as Bi-oo-Cyst ® to ensure chicks do not enter a highly contaminated rearing house.

Food medicated with the coccidiostat Avatec ® should be provided from day 1. The coccidiostat is not designed to kill all the oocysts but to maintain them at sub-clinical levels whilst allowing the bird to develop immunity. Any interference with food intake therefore can create clinical disease.

Common events that can reduce the feed intake of red-legged partridges include changes to feed pellet size, overstocking with insufficient feeders, poor weather conditions so birds are less inclined to go to feeders, very hot weather that suppresses appetite and aerial predators that limit feeding times. Diseases that cause the birds to scour also reduce the availability of medication in feed.

Many of these stresses can be controlled by good management, feed changes should always be managed gradually and birds going into release pens should be kept on the same feed and same type of feeders as they had in rear. Providing sufficient space for the birds together with sufficient feeders and drinkers is also good basic management.

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CORONAVIRUS INFECTION IN PHEASANTS

Coronavirus infection in pheasants causes clinical problems mainly in the breeding stock. It was first reported in Great Britain causing kidney disease and significant mortality in 1994. Since then the disease has become more common. Blood samples from clinically normal pheasants have shown antibodies to Coronavirus suggesting birds may be affected without showing signs of disease. There are many different strains of Coronavirus. Those affecting chickens tend to cause respiratory disease or in laying hens production may be decreased and eggshell quality is affected but kidney involvement is rare. In Pheasants, egg quality does not appear to be affected but egg production and fertility may be depressed. It is believed that the strains affecting Pheasants and causing clinical disease are different from those affecting chickens. Pheasants that die of Coronavirus usually show signs of visceral gout. There is no medication available to control outbreaks of this disease and the use of antibiotics and / or multivitamins has no discernible beneficial effect.

Visceral gout on the heart of a pheasant

Spread of disease:

The source of infection in pheasant breeding flocks usually cannot be determined but it is most likely introduced by a Pheasant that is carrying the virus without showing any clinical signs. In flocks where birds are caught up after the shooting season and with no previous history of disease, then the most likely source of infection is a bird that has come in over the boundary. If birds have been bought in, then disease could enter in birds that appear clinically normal. Chickens and other poultry could possibly carry infection but it is less likely that they will carry Pheasant strains of the virus. In chickens, airborne spread over 1000m has been reported so both birds resident within that radius but not actually on the site of infection and infected birds being transported along roads within 1000m of stock are theoretical, but unlikely, sources of infection.

Control of Coronavirus infections:

Most of the research into Coronavirus infections has been undertaken in poultry. The virus spreads rapidly amongst birds in a flock via both the respiratory tract and via faeces. After clinical recovery the virus can persist in a bird for several months. True egg transmission is not believed to be significant but transmission by surface contamination of eggs is likely to occur if eggs are not adequately disinfected. There is no evidence of spread by insects. Good biosecurity is required to prevent spread between flocks.

In cases of disease in Pheasants it is likely that, in addition to caught-up breeding birds being affected, the disease may also be present in the wild population. There is no absolute way of preventing outbreaks in subsequent years but with good management techniques the disease may cease to appear in the breeding birds on sites that have previously been affected.

The disease in the wild population will be lower if every effort has been made to reduce the number of wild birds at the end of the shooting season. Known infected birds – and all the birds in an affected breeding flock should be assumed to be infected – should not be released back into the wild as this will form a large reserve of infection available to the next generation of breeding birds.

In an attempted to induce immunity in the birds, poultry vaccines have been used on the basis that if a few infected birds enter the breeding pens, the spread of disease may be prevented or reduced. As there are many distinct strains of Coronavirus it is not possible to ensure control with the limited number of poultry vaccines that are available. Pheasants may be vaccinated by eye-drop as they enter the laying pens.

An interesting outbreak of disease occurred during the 2004 season when disease was diagnosed in 8-week-old birds in a release pen. The clinical signs of kidney damage were similar to those seen in breeding birds although the level of mortality experienced was not as high. The birds had been in the pen for about two weeks and there was no history of disease in the flock of origin. It was concluded that the birds were most likely infected after entering the release pen by wild birds present in the pen.

What to do if disease is suspected:

As with all disease outbreaks, it is important that a rapid diagnosis is made. In the case of Coronavirus, this is to prevent spread of disease to other flocks and so that a programme of control for subsequent seasons can be formulated.  In breeding flocks it may also be necessary to plan to replace any shortfall of eggs that looks likely to occur.

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Gapeworm Infection

Gapeworms are the most significant of the worm infestations to affect game birds. Infection is caused by a roundworm called Syngamus trachea and the clinical signs of 'gapes' results from physical blockage of the windpipe by the worms. Clinical signs may however vary in birds from the typical outstretched neck and open beak as a bird attempts to breathe, to a cough and shaking of the head, 'a snick',as the bird attempts to remove the windpipe obstruction. In  some cases these typical signs are not present and affected birds loose condition and may die with few respiratory signs being seen.

Syngamus

Life-cycle of the parasite: Adult worms, present in the windpipe of infected birds, produce eggs that are coughed up by the bird and are then swallowed to be passed out in the faeces. Worm larvae develop in the eggs. When another bird picks these eggs up as it feeds that bird will then become infected. An alternative route for infection is that earthworms eat the eggs containing larvae and the larvae migrate to the muscles of the earthworm where they remain until the worm is eaten by another bird. As earthworms can live up to eight years, infection can be present on land from which birds have been excluded for several years. Once a bird has swallowed larvae, the larvae make their way to the windpipe via the lungs - this usually takes about 4-5 days. Therefore, even if birds have been successfully wormed it could be as little as one week before clinical signs are again seen in the birds. The frequency between worming needs therefore to be adjusted depending on the level of infection in the pens.

Control of gapeworm disease: Clinical disease is seen in both breeding birds and in rearing stock, particularly those in the release pens. Birds appear to develop some form of immunity as they get older but this seems to decline as the breeding season approaches.

If birds are overwintered on the farm they should be routinely wormed before being moved to their winter quarters. All breeding stock should be wormed when they are moved to the breeding pens and if the breeding pens have been used in the previous year the birds should be wormed again two weeks after the initial treatment. As worm burdens can adversely affect egg production birds should always be treated if clinical disease is confirmed.

In rearing birds disease can be seen from two weeks of age but more usually it is seen in the release pens. This may be because rearing fields are often changed yearly and although infection can remain in the earthworm population, levels of infection will have declined if the area has not been used to rear birds for several years. In contrast release pens are often in the same place for many years and so infection is able to remain at significant levels even when birds are not present. In addition, members of the crow family may also be infected with gapeworms and these may have access to release pens but should not have access to rearing pens. All birds entering the release pens should be wormed routinely after being in the pens for 7-10 days. This will allow them to pick up some worms prior to treatment and hopefully allows some immunity to develop. Some keepers prefer to wait until clinical signs are present before treating the birds and if the management of the birds is good this can be very effective.

The most highly contaminated areas in the release pens are usually around the feeders and drinkers. Significant control of infection can be obtained by placing the feeders and drinkers off the ground on a weld-mesh grid to prevent birds picking up food off the floor from these areas. Regularly moving feeders and drinkers to clean ground will also help reduce contamination and subsequent infections. Providing additional feeders and drinkers will further reduce the level of contamination as will the use of suitable disinfectants on contaminated areas.

It can be seen from the lifecycle of the gapeworm that complete control of infection is virtually impossible for game birds. Control of gapes depends both on the sensible use of medication and good management, particularly of feeding and drinking areas in release pens. Other respiratory diseases can give similar clinical signs to gapes so it is important that if clinical disease is seen a correct diagnosis is obtained from your veterinary surgeon so that appropriate medication can be given.

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Mycoplasma Infection

Mycoplasma infections can cause clinical disease in all ages of birds. Stress and other infections can activate disease in carrier birds (i.e. birds with the organism present but which are not 'ill'). The presence of Mycoplasma can also increase the severity of other diseases that are present in the birds. It is economically one of the most important diseases of game-birds in the UK and hence every effort needs to be taken to control the condition.

Signs of disease

Swollen facial sinuses are one of the most obvious signs of active clinical infection but other signs may include sneezing, eye discharges and breathing through a partly opened beak. If joints are affected, then birds may be lame and in laying birds the disease is associated with reduced egg production.

Mycoplasma

Just as important however is the effect of Mycoplasmosis exacerbating other diseases. In these cases disease is more severe and proves harder to control.

Spread of disease

Most forms of Mycoplasmosis seen in game birds can be spread via the egg, as well as by direct contact between birds, and via faeces and other secretions. The congregation of birds around drinkers and feeders provides an ideal opportunity for the spread of this disease. As the disease can be present in birds that show no clinical signs, the absence of clinical signs in birds that are caught up before the breeding season is no guarantee that the birds are Mycoplasma-free.

Control of Mycoplasmosis

As the disease can be spread via the egg and as Mycoplasma adversely affects egg production, one of the most important times for Mycoplasma control in game birds is before and during the breeding season. In addition, the breeding season is one of particular stress for the adult birds and so it is a time when they are particularly vulnerable to infection.

Birds showing clinical signs of disease at catching up should be rejected from the breeding flock. Infection can be controlled, but not usually eliminated, by a variety of antibiotics and control is greatly improved by good management as this helps to minimise the stresses affecting the birds. The choice of antibiotic and the medication schedule will depend on a variety of circumstances and should be decided in consultation with the owner’s veterinary surgeon. The objective will be to minimise the amount of infection in the breeding birds during the breeding season. This will ensure that the levels of infection transmitted via the eggs are also minimal.

There is a vaccine available in this country to control Mycoplasma gallisepticum in layer pullets. This vaccine is not licensed for use in game birds and if used would only control the one strain of Mycoplasma. It is not effective in birds already carrying the disease. As the vaccine must be given as a very fine droplet in a spray to be effective – eye-drop administration is not likely to be effective - there are few flocks of game birds in the country where administration of the vaccine could be done effectively.

Control of Mycoplasma disease in rearing birds can also be achieved by antibiotic treatment. It should be remembered that wild birds are often carriers of this disease so they should be discouraged from remaining around the breeding, rearing and release pens.

If you have breeding birds,the time to consult your veterinary surgeon to formulate a Mycoplasma control programme is at the beginning of the new breeding season. If you buy in chicks or poults for further rearing, check what medication the parent birds have received and ask about their disease status. You should then contact your veterinary surgeon about two weeks before you take delivery of the birds to discuss what, if any, action you may need to take when the birds are delivered.

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Rotavirus Infection

Rotavirus infection can be seen in birds of all ages but its effects are most dramatically seen in young birds between 3 and 14 days old. The infection affects the gut resulting in wet droppings, the birds are rapidly depressed and vent pecking is common. Affected birds often eat the litter and may die because of the damage done to the gut by the virus or by gizzard impaction. A significant number of the birds that survive the infection become stunted. Although disease and deaths are most commonly seen in younger birds all ages can be affected. In the older birds other viruses, in addition to Rotavirus, are often isolated from scouring birds. Many birds suffer from subclinical disease so the absence of clinical disease does not ensure that Rotavirus is not present within a flock. Falls in egg production due to Rotavirus infection have not been recorded in gamebirds but have been seen under experimental conditions in chickens and turkeys.

Birds start to scour 2 – 5 days after becoming infected. Affected birds will huddle and deaths may be seen in severe cases within a few hours of the first clinical signs being observed. Death rates will vary but can be as high as 10% in severe outbreaks. Whilst showing clinical signs the affected birds pass large numbers of virus particles in their droppings and they can continue to pass virus for up to two weeks.

Swollen caecae

The virus particles excreted are able to persist on the land for some considerable time and so the virus can be transmitted between birds both by direct contact and by the virus being transported about on contaminated boots, equipment etc. There is no evidence that the virus is spread on or in the egg but the fact that birds can show disease so early in life does suggest that some birds are exposed to the virus at a very early age. There is no evidence of birds carrying the infection for long periods of time in their guts but with older birds often having sub-clinical infection, the virus can be transmitted about a site from the older to the younger birds.

Due to the persistence of the virus on the ground it is practically impossible to ensure that flocks remain clear of the disease. Transmission of the virus can be minimised by ensuring that the most vulnerable young stock are visited before older stock on the farm and that boots and clothing are regularly cleaned and changed when moving between older and younger stock.

It is not possible to diagnose Rotavirus infection from a simple post-mortem examination as the lesions seen can be caused by a variety of conditions. Further laboratory testing is required to confirm the presence of Rotavirus. There are some kits designed to rapidly identify the presence of mammalian Rotaviruses but these are not very useful in detecting Rotaviruses from gamebirds as they give too may incorrect results. For accurate diagnosis Electron microscopy or a PAGE (PolyAcrylamide Gel Electrophoresis) test that detects the presence of the genetic material from the Rotavirus is required. With both these tests, results will not be immediately available at the time of the post-mortem examination.

There is no specific treatment for Rotavirus infection. Affected birds need to be given re-hydration salts via the water to prevent dehydration and using a water disinfectant that is effective against viruses E.g. Virkon-S, will prevent birds being infected from a contaminated water supply. In some cases antibiotics may be effective against any secondary bacterial infections but will have no direct impact on the course of the Rotavirus infection. Vaccines to control Rotavirus are not at present commercially available but The Game Conservancy has being doing work with a test vaccine, which appears to have had some success in their trials. However given the different strains of virus that occur, the development of an effective commercial vaccine may prove difficult.

Conclusions:

1) Where rotavirus infection is suspected, ensure adequate testing is done to confirm the diagnosis.

2) In suspect cases and even before diagnosis, chicks should be given re-hydration salts and the water supply should be treated with a suitable disinfectant. The sooner treatment commences the less should be the losses.

3) Check hygiene practices on the site. Are there suitable facilities for staff to clean boots, equipment and themselves?

4) Check that as a general rule younger birds are visited first on the site. If sick birds are found then clean boots, equipment and hands before attending to other birds on the site. Any birds known to be sick should always be visited last and if possible isolated from other birds on site.

5) Check stocking levels and other condition in the houses to ensure other stresses on the birds

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Scour in Pheasants and Partridges

Scour (diarrhoea) which may be very watery, yellow and frothy, or black and blood stained often results in sick birds and if they are not treated, the birds rapidly lose condition and may in severe cases die.

There are many causes of scour, some of which are related to poor management, and it is important that the cause is identified for suitable and effective treatment of the bird. It is not possible, simply by looking at the type or colour of scour, to determine the cause. Not all frothy droppings for example signify protozoal infection. If birds are treated incorrectly, then their condition continues to deteriorate.

Causes of scour include viruses, bacteria, protozoa, food problems and poisoning.

Most birds are able to cope with some level of potential disease-causing organisms. It is when birds are stressed that their immune system is unable to cope and scouring occurs. These stress factors can include rapid changes in environmental temperature, poor weather conditions, overcrowding, bitting, food changes, moving etc.

To try to prevent scour we need to reduce or eliminate the causal organisms and minimise the potential stresses on the birds.

Viral causes of scour

Rotavirus infection in birds of 3-14 days of age will often produce a very watery scour. Affected birds huddle to keep warm and deaths may occur. Rotavirus is however not the only virus that causes scour and other viruses may cause similar symptoms.

People moving about the site easily spread viruses and viruses spread rapidly within a shed once introduced. Overcrowding of chicks and poor environmental conditions (excess humidity and poor temperature control) all contribute to making conditions more severe.

There is no specific treatment for viral infections but treating with rehydration salts to prevent dehydration can help support the birds. Acidifying the water may also be beneficial.

Bacterial Scour

A wide variety of bacteria can be recovered from scouring birds and these include Clostridia, E.coli and Spirochaete bacteria. In most cases the bacteria are naturally present in the bird’s gut but do not cause any clinical disease until the bird is under stress. Stresses that can induce disease include overcrowding, rapid temperature changes and other diseases.

Bacterial enteritis

Affected birds are usually depressed and may pass frothy droppings. Control of the underlying stress factors together with antibiotic treatment and rehydration salts should be effective in controlling the problem.

Protozoal Diseases

a) Trichomonas and Hexamita (Spironucleosis) Protozoa

Protozoa are normal inhabitants of the bird's gut but when present in large numbers may contribute to causing disease although the primary disaese is usually bacterial in origin. Affected birds become depressed and pass yellow, frothy caecal droppings. The protozoa are not known to persist on land from one year to the next. Disease, where these parasites are present, is usually seen in birds under stress and the removal of stress together with treatment with re-hydration salts and an antibiotic to control the bacterial enteritis should be effective in controlling the scour.

Spironucleosis

b) Coccidiosis

Coccidia are non-motile parasites and at least three different species are known to affect Pheasants with different species affecting Partridges. Affected birds may have loose droppings, they can rapidly lose condition and some mortality may occur. Coccidial oocysts are highly resistant and can survive on land for a long period of time even without any birds being present.

Pheasant coccidial oocysts

Pheasant coccidial oocysts - microscopic view

Once ingested their numbers multiply rapidly within the bird so it is usual for game bird feed to have a coccidiostat included. In birds exposed to small number of coccidia, a good immunity develops and it is usual for older birds to be immune to disease.

Food problems

There should be few problems with food prepared by the game feed companies. If there is a scour problem when birds receive a new batch of food and no other causes are obvious on veterinary examination, then a food problem may be suspected. If it is a food problem and the suspect food is removed then the scour should rapidly cease. If food is badly stored and fungal growths occur, they can produce mycotoxins. These toxins can cause a wide variety of symptoms that may be severe and can cause high mortality. Suspect food should not be used. If a food problem is suspected, then a veterinary examination is required.

Poisoning

Birds may be exposed both to natural and synthetic poisons and in some cases these can result in scour. The diagnosis of these conditions is often dependent on a good clinical history being taken and examination of the bird’s environment is often necessary. Once poisoning has occurred, there are rarely any specific antidotes available and supportive treatment of the birds is usually the best that is possible.

In conclusion:

It can be seen that there are many causes of scour in game birds and it is important that they are correctly investigated so that appropriate action can be taken. Where treatment is delayed, birds can rapidly lose condition with mortality occurring in the worst affected birds. It is not unusual for survivors to show signs of ill thrift due to severe damage to the gut lining

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  Sandhill Veterinary Services 14 Long Street, Topcliffe YO7 3RW telephone 01845 578710 fax 01845 577685 email rtb@sandhillvet.co.uk