Proventricular Dilatation Disease in Parrots: Signs, Testing and Treatment

By Dr Duncan Houston

Proventricular dilatation disease, commonly shortened to PDD, is one of the most feared diagnoses in parrot medicine.

An affected bird may lose weight despite continuing to eat, regurgitate food, pass undigested seeds or gradually develop weakness, tremors, poor coordination and difficulty perching. However, the disease is also frequently misunderstood because many healthy parrots test positive for parrot bornavirus without developing clinical PDD.

The diagnosis should never be made from one positive PCR result, one enlarged proventriculus or one vague neurological sign. PDD is a clinical and pathological disease syndrome. Parrot bornavirus infection is the underlying viral infection associated with that syndrome, but infection and disease are not interchangeable.

Quick Answer

Proventricular dilatation disease is an inflammatory neurological disease most commonly associated with parrot bornavirus. It damages nerves controlling the gastrointestinal tract and may also affect the brain, spinal cord and peripheral nerves.

Parrot bornavirus-positive birds may remain healthy for years, while clinically affected birds may develop progressive gastrointestinal or neurological disease. Diagnosis usually combines clinical signs, imaging, repeated PCR testing, serology and sometimes tissue biopsy or post-mortem histopathology. There is currently no proven cure, antiviral treatment or commercially available vaccine, but supportive and palliative care may stabilise selected birds. (Merck Veterinary Manual)

What Is Proventricular Dilatation Disease?

PDD is an inflammatory disease of the nervous system.

The virus itself can be present throughout many tissues, but the major clinical damage is associated with inflammation around nerves and nerve ganglia. This is known as lymphoplasmacytic ganglioneuritis.

When nerves controlling the gastrointestinal tract are affected, normal movement of food through the crop, proventriculus, ventriculus and intestines becomes impaired.

The proventriculus is the bird’s glandular stomach. It normally releases digestive enzymes before food moves into the muscular ventriculus, or gizzard. When nerve function deteriorates, food may remain in the gastrointestinal tract for too long and the proventriculus may become severely enlarged.

However, the name PDD can be misleading. Some infected birds develop mainly neurological signs and never show dramatic proventricular enlargement. The condition is also described as avian ganglioneuritis, neuropathic ganglioneuritis or neuropathic gastric dilatation. (Merck Veterinary Manual)

Parrot Bornavirus Infection Is Not the Same as PDD

This distinction changes how test results should be interpreted.

Situation	What it means
Parrot bornavirus-negative bird without signs	Infection has not been detected, although one negative test cannot guarantee that the bird is free from infection
Parrot bornavirus-positive bird without signs	The bird is infected or has evidence of exposure but does not currently have clinical PDD
Parrot bornavirus-positive bird with compatible signs	PDD becomes more likely, but other diseases still need to be excluded
Compatible signs with negative PCR	PDD is still possible because viral shedding is intermittent and testing can miss infection
Dilated proventriculus without confirmed infection	PDD is one differential, but obstruction, heavy metal poisoning, infection, neoplasia and other gastrointestinal diseases must be considered

Asymptomatic infection is common. Current Merck guidance notes that studies in Europe and North America have found parrot bornavirus in approximately 15% to 40% of apparently healthy parrots.

A 2026 necropsy study of 210 parrots found parrot bornavirus RNA in 50 birds. Only 18 of those 50 virus-positive birds had gross lesions typically associated with PDD. This was a selected population of deceased birds rather than healthy household parrots, but it further demonstrates that viral infection does not automatically produce characteristic disease. (Merck Veterinary Manual)

Does a Positive Test Mean the Bird Will Eventually Become Sick?

Not necessarily.

Some positive birds remain clinically normal for prolonged periods. Other birds develop gastrointestinal, neurological or mixed disease. At present, a positive PCR or antibody result cannot reliably predict:

• Whether clinical disease will develop

• When it will develop

• How severe it will become

• Which organ system will be affected

• Whether the bird will remain an asymptomatic carrier

Host immunity, viral genotype, age at infection, stress, concurrent disease and other poorly understood factors may influence whether infection progresses into PDD. (Wiley Online Library)

Which Birds Can Develop PDD?

Classic PDD is primarily recognised in parrots.

All parrot species should be considered potentially susceptible, but the condition has been particularly well documented in:

• Macaws

• African grey parrots

• Amazon parrots

• Conures

• Cockatoos

• Eclectus parrots

• Cockatiels

• Other psittacine species

Macaws, conures and African grey parrots are frequently represented in clinical reports, although that may partly reflect their popularity, longevity and likelihood of being referred for specialist care. (Merck Veterinary Manual)

Can Non-Parrot Birds Get Bornavirus Disease?

Bornaviruses have been identified in numerous bird orders, including canaries, waterfowl and raptors. However, these birds may carry different bornavirus species, and their disease patterns are not necessarily identical to classic parrot PDD.

A study of 201 canaries found an association between canary bornavirus infection and PDD-like gastrointestinal or neurological signs. This supports the possibility of related ganglioneuritis syndromes outside parrots, but owners should not assume that every bornavirus found in a chicken, duck, falcon or canary behaves like parrot bornavirus. (PubMed)

For a pet-owner article, PDD is most accurately discussed as a predominantly psittacine disease.

How Does Parrot Bornavirus Spread?

The exact transmission pathways and their relative importance remain incompletely understood.

Evidence supports possible shedding through:

• Faeces

• Urates

• Cloacal material

• Respiratory or oral secretions

• Feather dust or contaminated material

• Eggs and infected embryos

Viral shedding can be intermittent, meaning that an infected bird may test positive on one occasion and negative on another. (Merck Veterinary Manual)

Is Direct Bird-to-Bird Transmission Easy?

Not always.

Natural outbreaks demonstrate that parrot bornavirus can move between birds and facilities. In one outbreak investigation, birds exposed to affected parrots became infected and developed PDD, with the same viral strain later detected in another aviary. (ASM Journals)

However, one experimental study found no transmission to fully fledged sentinel cockatiels or canaries housed in contact with infected birds over four months. This suggests that ordinary direct contact may sometimes be inefficient, particularly in healthy adult birds. (PubMed)

The apparent contradiction probably reflects differences in:

• Viral strain

• Bird species

• Age

• Immune status

• Duration and intensity of exposure

• Wounds or damaged mucosa

• Environmental contamination

• Intermittent viral shedding

The safe clinical assumption is that transmission can occur, but not every exposed bird will become infected.

Can Parent Birds Pass It to Their Chicks?

Yes, vertical transmission is possible.

A controlled cockatiel study detected infectious parrot bornavirus in embryos and yolk material from infected breeding birds. Transmission was influenced by the age at which the parents had originally become infected, suggesting that vertical spread may occur more efficiently in some breeding situations than others. (PMC)

Breeding a known positive bird therefore requires specialist veterinary and aviary-management advice.

Does the Virus Survive for Years in the Environment?

Parrot bornavirus is an enveloped and relatively fragile virus. It is not considered as environmentally resistant as circoviruses or bacterial spores and is susceptible to detergents, routine disinfectants and ultraviolet light.

That does not mean hygiene can be relaxed. Fresh faecal and urate contamination, shared equipment and repeated exposure can still spread infection within a collection. (Merck Veterinary Manual)

What Are the Signs of PDD?

Birds may have gastrointestinal signs, neurological signs or a combination of both.

The severity can range from subtle weight loss to rapid neurological deterioration.

Gastrointestinal Signs

Possible signs include:

• Progressive weight loss

• Weight loss despite a normal or increased appetite

• Regurgitation

• Crop stasis or delayed crop emptying

• Undigested seeds or food particles in the droppings

• Poor digestion

• Increased volume of droppings

• Reduced faecal production in advanced gastrointestinal stasis

• Abdominal enlargement

• Reduced appetite

• Intermittent vomiting-like movements

• General weakness

• Recurrent secondary bacterial or fungal gastrointestinal infections

Food may sit within the proventriculus and ventriculus because the damaged nerves cannot coordinate normal contractions. The bird may continue eating while absorbing inadequate nutrition and progressively losing muscle. (Merck Veterinary Manual)

Undigested Seed Does Not Automatically Mean PDD

Whole or partially digested food in droppings is an important sign, but possible alternatives include:

• Macrorhabdus ornithogaster infection

• Pancreatic disease

• Severe intestinal inflammation

• Gastrointestinal parasites

• Heavy metal poisoning

• Gastrointestinal obstruction

• Advanced liver disease

• Rapid gastrointestinal transit

• Poor-quality or inappropriate food

• Other causes of gastrointestinal dysmotility

PDD should be investigated rather than assumed.

Neurological Signs

Possible neurological signs include:

• Weakness

• Poor balance

• Difficulty perching

• Falling from the perch

• Ataxia or incoordination

• Tremors

• Head tremors

• Abnormal gait

• Reduced awareness of limb position

• Leg weakness or paralysis

• Head tilt

• Abnormal eye movements

• Seizures

• Apparent blindness

• Abnormal vocalisation

• Sudden behavioural change

• Collapse

Some birds develop severe central nervous system disease without obvious gastrointestinal dilation. In a Brazilian study of symptomatic, bornavirus-positive parrots, neurological signs were more common than undigested seed, regurgitation or radiographic proventricular enlargement. (PubMed)

Is Feather Damaging Behaviour a Sign of Bornavirus?

Parrot bornavirus has been found more frequently in some groups of birds showing feather-damaging behaviour or unexplained neurological signs.

However, feather damaging is highly nonspecific and can be caused by:

• Skin disease

• Pain

• Poor nutrition

• Lack of sleep

• Reproductive behaviour

• Environmental frustration

• Anxiety

• Liver disease

• Viral feather disease

• Parasites

• Learned behaviour

A positive bornavirus result does not prove that the virus caused the feather damage. (Wiley Online Library)

How Worried Should You Be?

Lower Immediate Risk

The bird:

• Is clinically normal

• Maintains a stable weight

• Eats and passes normal droppings

• Has an incidental positive PCR or antibody test

• Shows no regurgitation or neurological abnormalities

Action: Do not medicate or euthanise the bird based only on the result. Separate the bird from confirmed-negative birds and discuss repeat testing and long-term monitoring with an avian veterinarian.

Moderate Risk

The bird has:

• Mild but persistent weight loss

• Occasional undigested food in droppings

• A mild voice or behavioural change

• Intermittent regurgitation

• Reduced stamina

• A suspicious but not definitive imaging result

Action: Arrange an avian veterinary examination within 24 hours. Begin daily weight monitoring and collect photographs or videos of droppings and behaviour.

High Risk

The bird has:

• Recurrent regurgitation

• Significant weight loss

• Delayed crop emptying

• Difficulty perching

• Tremors or intermittent incoordination

• A clearly enlarged proventriculus

• Progressive weakness

• Secondary infection or dehydration

Action: Seek same-day avian veterinary care. Hospitalisation, fluid support and assisted nutrition may be required.

Critical

The bird:

• Cannot remain perched

• Is collapsing

• Has repeated seizures

• Is open-mouth breathing

• Is choking or aspirating regurgitated material

• Cannot swallow safely

• Has severe abdominal distension

• Cannot keep food down

• Has profound weakness or abnormal awareness

Action: Treat this as an emergency and attend an avian veterinary hospital immediately.

When Is PDD an Emergency?

Seek immediate veterinary care when a bird develops:

• Repeated regurgitation with weakness

• Open-mouth breathing

• Pronounced tail bobbing

• Sudden collapse

• Inability to perch

• Repeated falling

• Seizures

• Severe incoordination

• Apparent blindness

• Marked abdominal enlargement

• Little or no faecal output

• Inability to swallow

• Feed or fluid coming from the nostrils

• Rapid deterioration over several hours

• Severe dehydration

• Profound weight loss or prominent keel bone

• Black, bloody or otherwise severely abnormal droppings

A weak or regurgitating bird is at risk of aspiration pneumonia. Neurologically abnormal birds may also injure themselves by falling or becoming trapped.

Do not repeatedly handle or exercise a bird that is struggling to balance or breathe.

What Should You Do Right Now?

1. Separate the Bird From Other Birds

Use a physically separate room or airspace where possible.

Provide:

• Separate food and water bowls

• Separate cleaning equipment

• Dedicated towels or cage liners

• Separate handling tools

• Care after confirmed-negative birds have been attended to

Isolation protects the flock while the diagnosis and viral status are investigated.

2. Keep the Bird Quiet and Secure

Use a low, stable perch or remove the perch if the bird is falling.

Pad the cage bottom with clean towels or paper so that a fall is less likely to cause injury. Keep the bird comfortably warm, but do not overheat a bird that is panting or open-mouth breathing.

3. Record the Bird’s Weight

Use an accurate gram scale.

Weigh at approximately the same time each day, preferably before the morning meal. Record:

• Weight

• Appetite

• Regurgitation

• Dropping appearance

• Activity

• Balance

• Medications

• Any food remaining in the crop

A progressive trend is much more useful than one isolated measurement.

4. Photograph the Droppings

Photograph any:

• Undigested food

• Change in colour

• Change in volume

• Reduction in faecal material

• Increased urine

• Blood or black material

Bring fresh samples when the veterinary clinic requests them.

5. Record Neurological Episodes

Film tremors, falling, abnormal walking or seizures from a safe distance.

Do not provoke the bird to repeat the sign for the camera.

6. Do Not Force Feed a Regurgitating or Neurologically Abnormal Bird

Force feeding can lead to aspiration when swallowing and crop function are impaired.

Nutritional support may be essential, but the method, formula, volume and frequency should be selected after the bird’s crop function and swallowing safety have been assessed.

7. Do Not Start Leftover Medication

Do not give:

• Celecoxib

• Meloxicam

• Steroids

• Human anti-inflammatory medication

• Antibiotics

• Antifungal medication

• Metoclopramide or another prokinetic

• Another bird’s prescription

These medications can cause serious adverse effects or complicate diagnosis when used without an avian treatment plan.

What Else Can Look Like PDD?

PDD has no single outward sign that is completely specific.

Main presentation	Important alternatives
Weight loss despite eating	Macrorhabdus, pancreatic disease, liver disease, cancer, chronic infection, malnutrition or parasites
Regurgitation	Crop infection, candidiasis, obstruction, heavy metals, reproductive behaviour or inappropriate feeding
Undigested food in droppings	Macrorhabdus, pancreatic insufficiency, intestinal disease, parasites or rapid transit
Enlarged proventriculus	Obstruction, heavy metal poisoning, neoplasia, fungal or bacterial proventriculitis, Macrorhabdus or functional dysmotility
Ataxia or tremors	Lead or zinc toxicity, hypocalcaemia, trauma, liver disease, infection, neoplasia or other viral disease
Seizures	Heavy metals, metabolic disease, head trauma, encephalitis, liver failure or hypoglycaemia
Weakness and inability to perch	Malnutrition, systemic infection, cardiac disease, musculoskeletal injury or advanced organ disease
Feather damaging	Behavioural, dermatological, nutritional, reproductive and numerous medical causes

Parrot bornavirus may also occur alongside circovirus or polyomavirus. A positive bornavirus result should not prevent the veterinarian from looking for concurrent disease. Mixed viral infections were identified frequently in the 2026 Polish necropsy population. (PMC)

How Is PDD Diagnosed?

There is no single perfect live-bird test.

Diagnosis usually depends on combining:

1. Clinical signs

2. Body-weight and physical findings

3. Radiographs or other imaging

4. PCR testing

5. Antibody testing

6. Tissue histopathology where appropriate

The strength of the diagnosis comes from how well these findings agree.

Physical Examination

An avian veterinarian will assess:

• Current and previous body weight

• Pectoral-muscle condition

• Crop emptying

• Abdominal enlargement

• Hydration

• Droppings

• Coordination

• Grip strength

• Ability to perch

• Vision and awareness

• Evidence of aspiration or secondary infection

A severely compromised bird may need stabilisation before extensive examination or restraint.

Radiographs

Radiographs may reveal:

• An enlarged proventriculus

• Enlargement of the ventriculus

• Retained food

• Altered intestinal gas patterns

• Abdominal organ displacement

• Aspiration pneumonia

• Other diseases that may explain the signs

Contrast radiography or fluoroscopy may demonstrate delayed gastrointestinal transit.

However, proventricular enlargement is not specific for PDD. A bird can also have PDD without dramatic enlargement, particularly when neurological signs dominate. (Merck Veterinary Manual)

PCR Testing

RT-PCR detects parrot bornavirus RNA.

Samples may include:

• Fresh droppings

• Cloacal swabs

• Choanal or crop samples

• Feather calami

• Tissue samples

A positive PCR result provides evidence that viral RNA was present in the submitted sample. It does not prove that the virus caused the bird’s current signs.

Why Can an Infected Bird Test Negative?

Viral shedding is intermittent.

The virus may not be present in the submitted droppings or swab at that particular moment. Sampling technique, sample degradation and genetic differences between virus strains can also affect detection.

A single negative PCR result does not rule out infection or PDD. (Merck Veterinary Manual)

How Many Samples Should Be Collected?

Laboratory protocols vary.

The Schubot Center for Avian Health recommends collecting fresh droppings or cloacal swabs from three different days within a 7-to-21-day period for an individual bird. Repeated samples improve the chance of detecting intermittent shedding. (TAMU Vet School)

For broader infection-status assessment, PCR and serology may be repeated at intervals of approximately four to six weeks. Current Merck guidance recommends up to three testing rounds before treating repeatedly negative birds as likely negative. (Merck Veterinary Manual)

Serology

Serology detects antibodies the bird has produced against parrot bornavirus.

A positive antibody result suggests exposure and an immune response. It does not prove that the bird has active clinical PDD or that the virus is currently being shed.

A negative result may occur:

• Early in infection

• Before seroconversion

• In a bird producing a weak immune response

• Because of differences between the test antigen and viral strain

Combining serology with PCR usually provides more useful information than either test alone. (ASM Journals)

How Should PCR and Serology Results Be Interpreted?

Test result	Practical interpretation
PCR positive and serology positive	Strong evidence of infection. Keep separate from negative birds and assess whether clinical disease is present.
PCR positive and serology negative	Possible early infection, intermittent infection or false-positive contamination. Separate and retest in four to six weeks.
PCR negative and serology positive	Previous or persistent infection is possible. A negative PCR may reflect intermittent shedding. Separate from negative birds and repeat testing.
PCR negative and serology negative	Reassuring but not definitive after one test. Serial testing is needed when exposure risk or clinical suspicion is significant.

A healthy bird that is positive by both methods should be considered infected, but the result does not predict whether that bird will develop PDD. (Merck Veterinary Manual)

Tissue Biopsy and Histopathology

The characteristic lesion is lymphoplasmacytic inflammation involving nerve ganglia and nerve plexuses.

Potential biopsy sites include the crop and other gastrointestinal tissues. However, lesions are patchy and may not be present in the small section collected.

Crop biopsy is less invasive than proventricular or ventricular biopsy, but false-negative results are common. Historical studies found that some confirmed PDD cases lacked diagnostic lesions in crop tissue. Proventricular biopsy is not routinely performed because the diseased organ may be thin, fragile and prone to leakage or dehiscence. (Sage Journals)

The strongest definitive diagnosis is often obtained after death through histopathological examination and immunohistochemistry of several tissues, including:

• Crop

• Proventriculus

• Ventriculus

• Duodenum

• Brain

• Spinal cord

• Peripheral nerves

• Adrenal tissue

• Heart

• Kidney

A negative crop biopsy cannot safely overrule strongly compatible clinical signs and other diagnostic findings.

Can PDD Be Cured?

There is currently no proven cure.

No antiviral medication has consistently eliminated parrot bornavirus or prevented progression of clinical disease. Treatment is therefore supportive and palliative, aiming to:

• Maintain nutrition and hydration

• Improve gastrointestinal movement

• Reduce inflammation

• Control neurological signs

• Treat secondary infections

• Preserve comfort and quality of life

Some birds deteriorate despite intensive care. Others stabilise and live for months or years. (Merck Veterinary Manual)

Supportive Nutrition

The diet may need to be changed to food that is easier to digest and move through the gastrointestinal tract.

Depending on the bird, the veterinarian may recommend:

• A nutritionally complete recovery formula

• Softened or easily digestible pellets

• Smaller, more frequent meals

• Reduced whole-seed intake when seeds are passing undigested

• Assisted feeding where swallowing is safe

• Additional calorie and protein support

• Monitoring of crop-emptying time

The correct diet depends on the bird’s species, body condition and gastrointestinal function.

A bird with severe crop stasis or recurrent regurgitation should not simply receive larger meals. More food entering a poorly moving gastrointestinal tract can make retention and aspiration risk worse.

Fluid and Hospital Support

Affected birds may require:

• Warmed fluid therapy

• Oxygen

• Temperature support

• Assisted feeding

• Anti-nausea treatment

• Monitoring for aspiration pneumonia

• Correction of electrolyte abnormalities

• Protection from falls

• Hospitalisation during severe deterioration

Weak birds can lose substantial body weight quickly and have little physiological reserve.

Prokinetic Medication

Drugs such as cisapride or metoclopramide may be used in selected birds to improve gastrointestinal movement.

They are not appropriate in every case. A mechanical obstruction should be excluded before stimulating gastrointestinal contractions, and the dose must be selected for the individual bird. (Merck Veterinary Manual)

Anti-Inflammatory Treatment

Non-steroidal anti-inflammatory drugs including meloxicam and celecoxib have historically been used because much of the clinical damage appears to result from immune-mediated inflammation around nerves.

Responses are variable, and long-term success has not been demonstrated consistently. These drugs also carry potential kidney, gastrointestinal and other systemic risks, especially in dehydrated or severely underweight birds. (MDPI)

A bird should not receive celecoxib merely because a PCR result is positive.

Cyclosporine: A Promising but Preliminary Treatment

A 2025 case series described six psittacine birds with clinical PDD treated with cyclosporine and itraconazole.

Several birds showed improvements in appetite, body weight, attitude, regurgitation or radiographic proventricular size. Some remained clinically stable for prolonged periods. However:

• Only six birds were reported

• There was no untreated control group

• The treatment was palliative rather than curative

• The virus remained detectable

• At least one bird later died

• Immunosuppression, kidney injury, liver injury, leukopenia and secondary fungal infection remain concerns

The authors concluded that further prospective research is needed. Cyclosporine should therefore be regarded as an emerging specialist option for selected refractory cases, not the new standard cure for PDD. (MDPI)

Itraconazole was used to reduce fungal-infection risk and may also alter cyclosporine concentrations. That combination introduces additional drug-interaction and toxicity concerns and requires close bloodwork monitoring.

Antibiotics and Antifungal Medication

Antibiotics do not treat parrot bornavirus.

They may be required when gastrointestinal stasis leads to secondary bacterial overgrowth, aspiration pneumonia or another confirmed bacterial infection.

Antifungal medication may be needed when candidiasis, aspergillosis or another fungal complication is present. Routine broad-spectrum medication without evidence of secondary infection can worsen dysbiosis and create additional adverse effects. (Merck Veterinary Manual)

Neurological Medication

Depending on the signs, an avian veterinarian may consider medication for:

• Seizures

• Neuropathic discomfort

• Severe tremors

• Self-trauma

• Anxiety associated with neurological dysfunction

These medications control complications. They do not eliminate the underlying virus.

Are Steroids Recommended?

Systemic corticosteroids are not a routine home treatment for PDD.

They can suppress immune activity, potentially worsen secondary infections and complicate interpretation of the bird’s response. They may occasionally be considered by an experienced avian veterinarian for a carefully selected situation, but should not be treated as a general rescue medication.

What Is the Prognosis?

The prognosis for a parrot bornavirus-positive bird without clinical disease is very different from the prognosis for a bird with advanced PDD.

Asymptomatic Positive Bird

The bird may remain clinically healthy for years and should not be euthanised solely because of a positive result.

Long-term management focuses on:

• Separation from negative birds

• Weight monitoring

• Stress reduction

• Repeat testing

• Early investigation of gastrointestinal or neurological changes

Current veterinary guidance specifically advises against euthanising clinically healthy positive birds. (Merck Veterinary Manual)

Clinically Affected Bird

Once significant gastrointestinal or neurological disease develops, the prognosis is generally guarded.

Some birds respond to supportive or anti-inflammatory treatment and remain stable for months or years. Others progress rapidly or relapse after an initial improvement.

Poorer prognostic signs include:

• Severe muscle wasting

• Inability to maintain weight

• Persistent regurgitation

• Aspiration pneumonia

• Inability to perch

• Repeated seizures

• Advanced neurological dysfunction

• Severe gastrointestinal dilatation

• Proventricular or ventricular rupture

• Multiple secondary infections

• Inability to eat or swallow safely

• Poor response to intensive supportive care

The treatment goal should be meaningful comfort and function, not simply extending life regardless of quality.

Managing a Healthy Parrot Bornavirus-Positive Bird

A positive result is not an immediate medical catastrophe.

Keep the Bird Separate From Confirmed-Negative Birds

Positive birds may be housed with other confirmed-positive birds when they are compatible and clinically stable.

Do not share:

• Food bowls

• Water bowls

• Perches

• Toys

• Cleaning tools

• Towels

• Carriers

• Feeding equipment

Monitor Weight and Droppings

Record weight at least weekly, and more frequently when any change is suspected.

Look for:

• Progressive weight loss

• Undigested food

• Regurgitation

• Reduced droppings

• Poor crop emptying

• Changes in coordination

• Reduced grip or perching ability

Avoid Unnecessary Medication

There is no evidence that every healthy positive bird benefits from lifelong celecoxib, meloxicam, antibiotics or antifungal medication.

Medication exposes the bird to side effects without proving that clinical disease will be prevented.

Reduce Reproductive and Environmental Stress

Breeding, overcrowding, frequent relocation, poor nutrition and unstable social conditions may contribute to clinical deterioration in susceptible birds.

This does not mean stress alone causes PDD. It means maintaining stable husbandry is sensible when managing a persistent viral infection.

Discuss Breeding Carefully

Vertical transmission has been demonstrated experimentally. Known positive birds should not be bred casually or sold as negative breeding stock. (PMC)

How Should New Birds Be Screened?

General new-bird quarantine is often described as approximately 30 to 40 days. That period is valuable for detecting many acute illnesses, but it is not enough by itself to clear a bird of parrot bornavirus. (Lafeber Company)

A stronger bornavirus screening plan may include:

1. Examination by an avian veterinarian on arrival

2. Strict quarantine in separate airspace

3. PCR testing using samples from several days

4. Serology

5. Repeat PCR and serology after approximately four to six weeks

6. Additional repeat testing when results remain negative but exposure risk is high

7. Introduction only after the overall test pattern and health assessment are reassuring

Because shedding is intermittent, it may take several months rather than one convenient calendar month to classify a bird confidently. (PMC)

How Can PDD and Parrot Bornavirus Be Prevented?

Complete prevention is difficult, but risk can be reduced.

Quarantine Every New Bird

Use a separate room and preferably a different ventilation system.

Care for established negative birds first and quarantined birds last.

Change clothing, clean footwear and wash hands between groups.

Test Before Introduction

Use both PCR and serology where available.

Do not rely on one faecal PCR or one veterinary visual examination.

Separate Positive and Negative Populations

The most practical control strategy in a multi-bird collection is maintaining separate epidemiological groups:

• Confirmed negative

• Questionable or awaiting retesting

• Confirmed positive

• Clinically ill

Each group should have dedicated equipment.

Clean Organic Material Before Disinfecting

Remove droppings, food and dust first.

Then apply a bird-safe disinfectant according to the manufacturer’s instructions. An enveloped virus is relatively easy to inactivate once the contaminated organic material has been removed.

Avoid Overcrowding

Overcrowding increases environmental contamination, social stress and the difficulty of maintaining separate equipment and hygiene.

Maintain Good Nutrition

A balanced, species-appropriate diet will not prevent viral infection, but it supports immune function, body condition and the bird’s ability to tolerate chronic disease.

Monitor Breeding Collections

Because vertical transmission can occur, breeding facilities require testing plans covering:

• Parent birds

• Eggs or embryos in selected circumstances

• Hand-reared chicks

• Movement between aviaries

• Newly acquired breeding stock

Is There a Vaccine?

There is no commercially available vaccine for pet parrots.

Experimental viral-vector vaccines have protected cockatiels against challenge infection in research settings, but these products have not become routine clinical vaccines. (PubMed)

Common PDD Mistakes

Assuming a Positive PCR Means the Bird Has PDD

PCR detects viral RNA. It does not diagnose clinical ganglioneuritis.

Assuming One Negative PCR Clears the Bird

Intermittent shedding makes false-negative results possible.

Diagnosing PDD From an Enlarged Proventriculus Alone

Proventricular enlargement has several important differentials.

Waiting for Severe Weight Loss

Birds may hide illness. A small progressive decline in gram weight can be clinically important.

Treating Every Positive Bird With Celecoxib

There is no evidence that routine treatment of asymptomatic positive birds prevents clinical disease.

Starting Antibiotics for Undigested Seed

Antibiotics do not treat viral ganglioneuritis and may delay diagnosis of Macrorhabdus, obstruction, toxicosis or other disease.

Force Feeding a Regurgitating Bird

Aspiration can be fatal. Swallowing and gastrointestinal movement need to be assessed first.

Ending Quarantine After 30 Days and One Test

Bornavirus screening often requires serial testing over a longer period.

Euthanising a Healthy Positive Bird

A positive bird may remain clinically normal. Separation and monitoring are appropriate unless there are separate welfare concerns.

Keeping Positive and Negative Birds Together Because Nobody Looks Sick

Asymptomatic infection and intermittent shedding make visual screening unreliable.

Frequently Asked Questions

Does a positive bornavirus test mean my bird has PDD?

No. It means there is evidence of infection or exposure. Clinical PDD requires compatible disease signs and supporting diagnostic findings.

Can a bird test negative and still have PDD?

Yes. Viral shedding is intermittent, and one PCR sample may miss infection. Repeat PCR, serology, imaging and other tests may be needed.

Is an enlarged proventriculus always caused by PDD?

No. Obstruction, heavy metal poisoning, Macrorhabdus, other infections, neoplasia and functional gastrointestinal disease can also cause enlargement or delayed emptying.

Can a bird recover from PDD?

Some birds stabilise for prolonged periods with supportive and palliative care. There is no proven cure, and relapse or progression remains possible.

Should a healthy bornavirus-positive bird be euthanised?

No. Current veterinary guidance does not recommend euthanasia solely because an otherwise healthy bird tests positive. The bird should be separated from confirmed-negative birds and monitored.

Is a 30-day quarantine enough to rule out bornavirus?

No. General quarantine is useful, but bornavirus testing often requires several samples and repeat PCR plus serology at four-to-six-week intervals.

Final Thoughts

Proventricular dilatation disease and parrot bornavirus infection are related, but they are not the same diagnosis.

A positive PCR result does not prove the bird has PDD. A negative result does not reliably exclude it. An enlarged proventriculus raises concern but is not specific enough to stand alone.

The most useful approach is to combine:

1. The bird’s clinical signs

2. Daily or weekly body-weight trends

3. Radiographic and gastrointestinal findings

4. Repeated PCR testing

5. Serology

6. Histopathology where appropriate

7. A careful search for competing diagnoses

There is no proven cure, but that does not mean every positive or affected bird has the same outcome. Clinically healthy positive birds may remain well for years. Some birds with clinical disease can be stabilised, while severely affected birds may continue to deteriorate despite intensive treatment.

The most important practical decision is not whether the laboratory report contains the word “positive.” It is whether the bird is maintaining weight, digesting food, moving normally and living comfortably.

---

ASK A VET™ can help you organise body-weight records, droppings photographs, neurological videos, PCR and antibody results, imaging reports and medication history while you work with your avian veterinarian. A bird with repeated regurgitation, open-mouth breathing, collapse, seizures or inability to perch still requires immediate hands-on veterinary care.