Seminal Vesicle Disease

Seminal vesicle disease is a significant health condition affecting intact male guinea pigs, characterized by inflammation, infection, or abnormal enlargement of the seminal vesicles. These paired accessory reproductive glands are responsible for producing seminal fluid that nourishes and transports sperm during reproduction. When disease affects these structures, it can lead to substantial discomfort, systemic illness, and potentially life-threatening complications if left untreated. Understanding this condition is essential for cavy owners who keep intact males, whether for breeding purposes or as companions.

This condition occurs with moderate frequency in the guinea pig population, with intact males over three years of age being particularly susceptible. The causes range from bacterial infections ascending from the urinary tract to age-related degenerative changes in the glandular tissue. Impaction of the seminal vesicles with inspissated secretions is another common presentation, particularly in older boars who may have reduced reproductive activity. The warm, protein-rich environment of the seminal vesicles creates an ideal setting for bacterial proliferation when normal drainage is compromised.

The impact of seminal vesicle disease on a guinea pig's health and quality of life can be considerable. Affected animals often experience significant pain and discomfort, leading to decreased appetite, reduced activity, and behavioral changes. Because guinea pigs are prey animals that instinctively hide signs of illness, owners may not recognize the severity of the condition until it has progressed substantially. The inflammation can spread to surrounding structures, including the bladder and prostate, creating a complex multi-organ disease process that becomes increasingly difficult to manage.

Fortunately, seminal vesicle disease is treatable when identified early and managed by an experienced exotic veterinarian. Treatment success depends heavily on the underlying cause, the extent of tissue involvement, and how quickly intervention begins. Early detection through regular health monitoring and prompt veterinary attention at the first signs of illness significantly improves outcomes. For breeding males, this condition can have important implications for fertility, making awareness and prevention particularly important for cavy breeders maintaining intact boars.

The primary causes of seminal vesicle disease in guinea pigs are bacterial infections, impaction of glandular secretions, and age-related degenerative changes. Bacterial infections most commonly occur when organisms ascend from the urinary tract or migrate from other infected sites in the body. Common causative bacteria include Escherichia coli, Streptococcus species, Staphylococcus species, and Pasteurella multocida. These organisms can establish infection when the guinea pig's immune system is compromised or when anatomical abnormalities allow bacterial colonization of normally sterile reproductive structures.

While seminal vesicle disease is not considered a hereditary condition, certain anatomical variations may predispose individual guinea pigs to developing problems. Males with naturally narrower reproductive tract anatomy may be more susceptible to impaction and subsequent infection. There is no strong breed predisposition documented for this condition, though any genetic factors affecting immune function or reproductive tract development could theoretically influence susceptibility. Breeders should be aware that males who have experienced this condition may pass anatomical variations to offspring.

Environmental factors play a significant role in the development of seminal vesicle disease. Poor husbandry conditions, including dirty bedding, inadequate cage cleaning, and unsanitary water sources, increase the bacterial load in the guinea pig's environment and elevate infection risk. Inappropriate bedding materials, particularly those that retain moisture or harbor bacteria, can contribute to urogenital infections that may ascend to the seminal vesicles. Inadequate cage ventilation and high ambient humidity create conditions favorable for bacterial growth and can stress the guinea pig's immune system.

Several risk factors increase a male guinea pig's likelihood of developing seminal vesicle disease. Age is perhaps the most significant factor, with males over three years being at substantially higher risk due to reduced glandular function and immune senescence. Intact males who are not regularly breeding may develop inspissated secretions that block normal glandular drainage. Obesity places additional stress on the reproductive system and can impair normal anatomical function. Vitamin C deficiency, common in guinea pigs, compromises immune function and tissue integrity, making affected animals more vulnerable to infection. Previous urinary tract infections or reproductive tract surgeries also increase risk.

The disease mechanism typically begins with either bacterial colonization or mechanical obstruction of the seminal vesicle ducts. When bacteria establish infection, they trigger an inflammatory response that causes swelling, pain, and altered glandular function. The inflammation can lead to abscess formation within the glandular tissue, creating pockets of infection that are difficult to resolve with antibiotics alone. In cases of impaction, accumulated secretions stretch the vesicle walls, compress surrounding structures, and create an environment conducive to secondary bacterial infection. Progressive enlargement can eventually compress the urethra, bladder, or colon, leading to urinary obstruction or constipation.

Early warning signs of seminal vesicle disease are often subtle and easily overlooked, reflecting the guinea pig's natural tendency as a prey animal to mask signs of vulnerability. Initial symptoms may include mild changes in posture, with affected males adopting a slightly hunched stance or showing reluctance to stretch fully when moving. Owners may notice their guinea pig spending more time in hiding spots or showing decreased enthusiasm for social interaction. Subtle changes in eating patterns, such as taking longer to finish meals or showing preference for softer foods, can indicate early discomfort. These early signs warrant close monitoring and consideration of veterinary evaluation before the condition progresses.

As the disease advances, more recognizable symptoms emerge. Affected guinea pigs commonly display discomfort when the perineal region is touched or when they attempt to urinate or defecate. Straining during urination or the production of small, frequent amounts of urine suggests involvement of the urinary system. Some males may vocalize or squeak when attempting to eliminate, indicating pain. Blood in the urine, while not always present, is a concerning sign that warrants immediate veterinary attention. Discharge from the penile sheath, ranging from cloudy to purulent, may be observed in cases of active infection.

Behavioral changes become increasingly apparent as seminal vesicle disease progresses. Affected guinea pigs typically show marked decreases in activity levels, spending extended periods immobile or reluctant to move around their enclosure. Appetite reduction is common and concerning, as guinea pigs require continuous food intake to maintain healthy gut function. Social animals by nature, sick guinea pigs may isolate themselves from cage mates or show uncharacteristic aggression when approached. Teeth grinding, known as bruxism, often indicates pain in guinea pigs and may be heard during quiet moments. Some males may repeatedly stretch or shift position as they attempt to find a comfortable posture.

Physical examination may reveal several characteristic signs of seminal vesicle disease. Abdominal palpation often detects enlarged, firm, or painful masses in the caudal abdomen corresponding to the affected seminal vesicles. The perineal region may appear swollen or asymmetrical, and gentle pressure may elicit pain responses. Weight loss becomes apparent as the condition persists, with affected guinea pigs showing prominent spine and hip bones despite previously healthy body condition. The coat quality often deteriorates, appearing rough, unkempt, or greasy due to reduced grooming behavior. In severe cases, abdominal distension may be visible.

Symptom progression follows a predictable pattern if the condition remains untreated. Mild discomfort evolves into obvious pain, with affected guinea pigs showing increasingly pronounced signs of distress. Appetite continues to decline, leading to weight loss and potential GI stasis, a life-threatening condition in guinea pigs. Urinary symptoms may worsen, with complete urinary obstruction possible in severe cases where enlarged vesicles compress the urethra. Secondary infections can develop as the guinea pig's immune system becomes overwhelmed, potentially leading to sepsis. The animal's overall condition deteriorates progressively, with weakness, dehydration, and hypothermia indicating advanced illness.

Certain symptoms constitute emergencies requiring immediate veterinary care. Complete inability to urinate, indicated by repeated unsuccessful straining attempts and a distended bladder, represents a life-threatening emergency. Signs of sepsis, including fever or hypothermia, rapid breathing, extreme lethargy, and collapse, require urgent intervention. Severe abdominal distension or rigid abdomen suggests possible rupture or severe internal complications. Any guinea pig that has stopped eating entirely for more than twelve hours is at risk of hepatic lipidosis and GI stasis, both serious conditions requiring prompt treatment. Respiratory distress accompanying reproductive tract disease may indicate systemic spread of infection.

Diagnosis of seminal vesicle disease begins with a comprehensive physical examination by a veterinarian experienced with exotic species and guinea pig medicine specifically. The veterinarian will obtain a detailed history, including the guinea pig's age, breeding status, housing conditions, diet, and timeline of symptom development. Physical examination includes careful palpation of the abdomen to assess for masses, pain responses, and organ enlargement. The perineal region receives particular attention, with evaluation of symmetry, swelling, and any discharge from the penile sheath. Rectal examination, while technically challenging in guinea pigs, may provide additional information about the size and texture of reproductive structures.

Diagnostic testing provides essential information for confirming seminal vesicle disease and guiding treatment decisions. Abdominal radiographs reveal the size and position of reproductive structures, identify calcifications or masses, and assess for secondary changes such as bladder distension or constipation. Ultrasound examination offers superior soft tissue detail, allowing visualization of the seminal vesicle architecture, identification of abscesses or fluid accumulation, and assessment of blood flow to affected organs. Complete blood count and serum chemistry panels evaluate overall health status, identify signs of infection or inflammation, and assess organ function. Urinalysis may reveal blood, bacteria, or inflammatory cells suggesting urinary tract involvement. Culture and sensitivity testing of any discharge helps identify causative organisms and guide antibiotic selection.

Differential diagnosis for seminal vesicle disease includes several conditions that may present with similar symptoms. Prostatic disease, including benign enlargement and infection, produces comparable clinical signs and requires differentiation through imaging studies. Bladder stones or urinary tract infections cause straining and blood in urine but typically show characteristic radiographic changes. Testicular tumors or orchitis create perineal swelling and discomfort but involve different anatomical structures. Impaction of the perineal sebaceous glands, common in boars, causes local swelling but lacks the systemic signs associated with seminal vesicle disease. Intestinal obstruction or severe constipation may cause similar abdominal discomfort and requires careful evaluation to distinguish from reproductive tract pathology.

Once seminal vesicle disease is confirmed, the veterinarian assesses severity to guide treatment planning and establish prognosis. Severity staging considers the size of affected vesicles, presence of abscessation, extent of involvement of surrounding structures, and the guinea pig's overall health status. Mild cases may involve simple enlargement without infection, while moderate cases show evidence of bacterial involvement. Severe cases demonstrate abscess formation, multi-organ involvement, or systemic signs of sepsis. This assessment helps determine whether medical management alone may suffice or whether surgical intervention is necessary. The veterinarian discusses findings with the owner, explains treatment options, and helps establish realistic expectations for outcome.

Emergency and immediate treatment focuses on stabilizing the guinea pig and addressing life-threatening complications before definitive therapy begins. Patients presenting with urinary obstruction require immediate catheterization or cystocentesis to relieve bladder pressure and prevent rupture. Fluid therapy corrects dehydration, supports kidney function, and helps maintain blood pressure in compromised patients. Pain management is essential, with guinea pig-safe analgesics such as meloxicam or buprenorphine administered to improve comfort and encourage eating. Temperature support helps hypothermic patients, as guinea pigs lose body heat rapidly when ill. Oxygen supplementation benefits patients showing respiratory compromise.

Medical management forms the cornerstone of treatment for many cases of seminal vesicle disease. Antibiotic therapy targets identified or suspected bacterial pathogens, with drug selection guided by culture and sensitivity results when available. Guinea pig-safe antibiotics include trimethoprim-sulfa combinations, enrofloxacin, chloramphenicol, and azithromycin. It is critically important to avoid penicillin-type antibiotics, cephalosporins, clindamycin, and lincomycin, as these can cause fatal disruption of the guinea pig's intestinal flora, leading to enterotoxemia and death. Antibiotic courses typically extend for two to four weeks, with reassessment determining need for continuation. Anti-inflammatory medications reduce swelling and pain, improving comfort and supporting appetite.

Surgical intervention becomes necessary when medical management fails to resolve the condition or when anatomical abnormalities require correction. Surgical options include drainage of abscesses, removal of impacted material, and in severe cases, surgical excision of affected seminal vesicles. Castration may be recommended in conjunction with other procedures, as removing the hormonal stimulus to the accessory glands can aid recovery and prevent recurrence. Surgery in guinea pigs carries inherent risks related to anesthesia and their sensitive gastrointestinal system, but experienced exotic surgeons achieve good outcomes with appropriate patient preparation and post-operative care. Surgical candidates should be stabilized before procedures whenever possible.

Supportive care is essential for recovery regardless of whether medical or surgical treatment is pursued. Syringe feeding with critical care formulas maintains gut function and prevents hepatic lipidosis in guinea pigs who have reduced or stopped eating. Feeding every four to six hours with appropriate volumes ensures adequate caloric and fiber intake. Vitamin C supplementation at therapeutic doses supports immune function and tissue healing, with doses of 50 to 100 milligrams daily appropriate for ill guinea pigs. Subcutaneous fluid administration helps maintain hydration in patients not drinking adequately. Gentle massage of the perineal region may help promote drainage of inspissated material in some cases. Maintaining the guinea pig at appropriate environmental temperature and providing soft bedding improves comfort.

Alternative and complementary treatments may support conventional therapy but should not replace veterinary care for this potentially serious condition. Probiotics help maintain healthy gut flora during antibiotic therapy and reduce risk of dysbiosis. Gentle warm compresses applied to the perineal region may provide comfort and promote circulation. Ensuring the guinea pig has a stress-free environment supports immune function and healing. Some owners find that providing favorite foods encourages eating in recovering patients. Herbal remedies marketed for urinary health have not been scientifically validated for guinea pigs and should only be used under veterinary guidance if at all.

Treatment decisions should consider multiple factors including the guinea pig's age, overall health status, severity of disease, owner's ability to provide nursing care, and financial considerations. Older guinea pigs or those with concurrent health conditions may have reduced tolerance for aggressive interventions. The owner's ability to administer medications, provide syringe feeding, and monitor for complications influences treatment success. Open communication between the veterinarian and owner ensures appropriate treatment planning that balances the best chance of cure with quality of life considerations. In some severe or advanced cases, humane euthanasia may be the most compassionate option.

Recovery timeline for seminal vesicle disease varies considerably depending on disease severity, treatment approach, and individual patient factors. Mild cases treated medically may show significant improvement within one to two weeks, with complete resolution over four to six weeks. Moderate cases with bacterial infection typically require longer antibiotic courses and may take six to eight weeks to resolve fully. Surgical cases often show rapid improvement in clinical signs following the procedure, but complete healing requires several weeks of careful post-operative management. Owners should anticipate that recovery will be a gradual process requiring patience and consistent care throughout the healing period.

Post-treatment care plays a crucial role in successful recovery and preventing relapse. Continued syringe feeding supports nutrition until the guinea pig is eating independently and maintaining weight. Follow-up veterinary appointments allow monitoring of healing progress and early detection of any complications. Medications must be administered as prescribed for the full course, even if the guinea pig appears improved. Wound care following surgery includes monitoring for signs of infection, swelling, or dehiscence. The guinea pig should be housed in a clean environment with soft bedding that will not irritate healing tissues. Activity restriction may be recommended following surgery to prevent strain on healing structures. Close monitoring of urination and defecation patterns helps identify any ongoing urinary or GI involvement.

Prognosis depends on several factors that influence the likelihood of full recovery. Earlier intervention generally leads to better outcomes, as advanced disease is more difficult to resolve completely. The underlying cause affects prognosis, with simple impaction having better outcomes than established abscessation. The guinea pig's overall health and immune function influence healing capacity, with healthier animals recovering more readily. Success of treatment in resolving infection, as demonstrated by follow-up testing, indicates favorable prognosis. Age influences recovery, with younger guinea pigs generally having better regenerative capacity. Complete response to treatment without recurrence during the first several months suggests good long-term outlook.

Long-term outlook for guinea pigs who recover from seminal vesicle disease is generally favorable when the underlying cause has been addressed. Males who have undergone successful treatment may return to normal reproductive function if desired, though some may have reduced fertility. Those who have been castrated as part of treatment will obviously not be able to breed but can otherwise live normal lives. Regular monitoring helps detect any recurrence early, when intervention is most effective. Some guinea pigs remain predisposed to recurrence and may benefit from ongoing preventive measures. With appropriate management, most recovered guinea pigs enjoy good quality of life and normal life expectancy for their age.

Primary prevention of seminal vesicle disease focuses on maintaining optimal health and reducing risk factors in intact male guinea pigs. Ensuring adequate vitamin C intake is fundamental, as deficiency compromises immune function and tissue integrity throughout the body, including the reproductive tract. Daily vitamin C supplementation at 25 to 50 milligrams for healthy adult males, provided through fresh vegetables or species-appropriate supplements, helps maintain immune competence. Keeping males at healthy body weight reduces strain on reproductive organs and maintains normal anatomical relationships. Providing regular opportunities for exercise promotes circulation and overall health. Maintaining intact males in appropriate breeding programs or considering castration for non-breeding pets reduces the accumulation of reproductive secretions.

Environmental prevention addresses housing and husbandry factors that influence disease risk. Maintaining scrupulously clean cages with regular bedding changes reduces bacterial load in the guinea pig's environment. Selecting appropriate bedding materials that wick moisture away from the body and do not harbor bacteria protects urogenital health. Paper-based bedding or fleece liners with absorbent underlayers are preferred over dusty or aromatic wood shavings. Ensuring adequate cage ventilation prevents humidity buildup while avoiding drafts that can stress the immune system. Cleaning food dishes and water bottles daily prevents bacterial contamination of food and water sources. Quarantine procedures for new animals help prevent introduction of infectious organisms.

Dietary prevention centers on the hay-based diet essential for guinea pig health. Unlimited timothy hay or other grass hays provides fiber necessary for proper gut function and naturally wears teeth to prevent dental problems that can cause systemic stress. Fresh vegetables, particularly those high in vitamin C such as bell peppers and leafy greens, should be offered daily. Avoiding excessive sugars and starches in the diet maintains healthy gut flora and prevents obesity. Clean, fresh water must be available at all times to support urinary health and prevent concentrated urine that may irritate reproductive structures. High-quality guinea pig pellets formulated with vitamin C can supplement the diet but should not replace hay and vegetables.

Health maintenance through regular veterinary care enables early detection and intervention. Annual or biannual wellness examinations by an exotic veterinarian familiar with guinea pigs allow assessment of reproductive health in intact males. Weight monitoring at home helps detect early changes that may indicate developing illness. Regular grooming and perineal inspection allows owners to identify swelling, discharge, or other abnormalities early. Prompt attention to any urinary symptoms, including straining, blood in urine, or changes in urination patterns, enables treatment before secondary complications develop. Dental examinations ensure teeth remain healthy, as dental pain causes systemic stress that may predispose to other illnesses.

Early intervention strategies help prevent progression of minor issues to serious disease. Addressing urinary tract infections promptly prevents ascending infection to reproductive structures. Managing constipation through dietary adjustment and hydration prevents straining that may affect pelvic organs. Treating any illness promptly with appropriate veterinary care prevents the immune suppression associated with chronic disease. Owners should develop familiarity with normal appearance and behavior so they can recognize subtle early changes indicating developing problems. Establishing a relationship with an exotic veterinarian before emergencies arise ensures prompt access to appropriate care when needed.

Daily management of guinea pigs recovering from or living with seminal vesicle disease requires attention to care routines that support ongoing health. Medication administration must follow prescribed schedules, with antibiotics given at consistent times to maintain therapeutic blood levels. Syringe feeding schedules should be maintained until the guinea pig reliably eats independently and maintains stable weight. Daily monitoring of appetite, activity level, and elimination patterns helps detect any concerning changes early. Gentle handling prevents stress while allowing necessary health checks. The guinea pig should have quiet rest periods throughout the day to support healing and reduce stress. Keeping a daily log of observations helps track progress and provides valuable information for veterinary follow-up visits.

Home environment modifications support recovery and ongoing management. The cage setup should allow easy access to food, water, and hiding areas without requiring excessive movement for compromised patients. Ramps to elevated areas should be removed or made less steep during recovery from surgery. Bedding should be soft, clean, and changed frequently to prevent irritation and infection. Temperature should be maintained in the comfortable range of 65 to 75 degrees Fahrenheit, as ill guinea pigs are susceptible to temperature stress. Hiding houses provide security but should allow the owner to monitor the guinea pig easily. Cage placement should be in a quiet area away from loud noises and household traffic while still allowing social interaction with the family.

Maintaining quality of life is essential even while managing health conditions. Guinea pigs are highly social animals, and maintaining contact with bonded cage mates supports emotional wellbeing, though supervision may be needed if the ill guinea pig is being harassed or cannot compete for resources. Providing favorite foods within dietary guidelines encourages eating and provides positive experiences. Gentle interaction and handling, when tolerated, maintains the human-animal bond and allows monitoring. Floor time for exercise should be modified based on the guinea pig's condition and veterinary recommendations. Environmental enrichment such as hay tunnels, safe chew toys, and exploration opportunities supports mental health within physical limitations.

Ongoing monitoring remains important even after initial recovery. Regular weight checks, ideally weekly, help detect early changes that may indicate recurrence or other developing problems. Observing urination and defecation patterns ensures these functions remain normal. Periodic perineal inspection checks for any swelling or discharge. Following up with the veterinarian as recommended allows professional assessment of continued health. Any return of previous symptoms or development of new concerns should prompt prompt veterinary evaluation. Males who have recovered from seminal vesicle disease may remain at elevated risk for recurrence and benefit from heightened awareness.

Caregiver support and resources help owners provide optimal care for guinea pigs with health challenges. Connecting with guinea pig rescue organizations and online communities provides access to experienced owners who can offer practical advice. Keeping veterinary contact information readily available ensures quick access to professional guidance when questions arise. Understanding what constitutes an emergency versus a routine concern helps owners make appropriate decisions about urgency of care. Financial planning for ongoing veterinary needs reduces stress when care is needed. Self-care for caregivers is also important, as managing a chronically ill pet can be emotionally demanding. Recognizing when to seek additional support or consider quality of life decisions is part of responsible pet ownership.

Seminal vesicle disease does not show strong breed predisposition in guinea pigs, as it primarily relates to sex hormones and reproductive anatomy common to all intact males rather than breed-specific characteristics. However, certain factors associated with some breeds or breeding situations may influence risk. Larger breed guinea pigs may have correspondingly larger reproductive structures that could potentially be more susceptible to impaction, though this relationship has not been definitively established. Guinea pigs from intensive breeding operations may experience reproductive stress that could theoretically increase susceptibility, though individual variation likely plays a larger role than breed characteristics.

All intact male guinea pigs share essentially equivalent risk for developing seminal vesicle disease, with individual factors being more predictive than breed. Males kept as single pets without breeding opportunity may develop inspissated secretions at higher rates than actively breeding boars. Older males across all breeds show increased incidence, reflecting age-related changes in glandular function and immune competence. Males with history of urinary tract problems may be predisposed regardless of breed. Any male guinea pig showing signs compatible with reproductive tract disease should receive prompt veterinary evaluation regardless of breed background.

Screening recommendations for breeders focus on general reproductive health rather than breed-specific concerns for seminal vesicle disease. Breeding males should receive regular veterinary examinations that include assessment of reproductive structures. Any male showing fertility problems, discomfort, or changes in breeding behavior should be evaluated for reproductive tract disease. Breeders should maintain records of any reproductive health issues in their lines, as this information helps identify individual animals or family lines that may have increased susceptibility. Retiring males from breeding programs before advanced age reduces risk of reproductive tract problems while ensuring genetic contribution has been secured. Responsible breeding practices include health screening and careful record-keeping to promote overall reproductive health in breeding populations.

Several conditions commonly co-occur with or develop secondary to seminal vesicle disease in guinea pigs. Urinary tract infections frequently accompany seminal vesicle disease, either as a primary cause of ascending infection or as a secondary consequence of altered urine flow and local inflammation. Bladder stones may develop when urinary stasis and infection alter urine composition, creating conditions favorable for stone formation. Prostatic disease, including benign enlargement and prostatitis, may occur concurrently given the anatomical and functional relationships between these reproductive structures. Constipation can develop when enlarged seminal vesicles compress the descending colon. GI stasis, a life-threatening condition in guinea pigs, may occur secondary to pain, reduced food intake, and systemic illness associated with seminal vesicle disease.

Conditions presenting with similar symptoms to seminal vesicle disease require differentiation during diagnostic evaluation. Bladder sludge or stones cause straining, pain, and blood in urine similar to seminal vesicle involvement. Testicular tumors or infection create perineal swelling that may be confused with seminal vesicle enlargement. Impacted perineal scent glands, common in male guinea pigs, cause local swelling and discomfort but are generally superficial. Prostatic enlargement produces similar abdominal findings on palpation. Intestinal obstruction or severe constipation may cause abdominal distension and discomfort mimicking reproductive tract disease. Careful diagnostic evaluation distinguishes among these possibilities.

Potential complications of untreated or severe seminal vesicle disease include several serious conditions. Abscess rupture can lead to peritonitis, a life-threatening infection of the abdominal cavity. Urethral obstruction from external compression causes urinary retention and potential bladder rupture. Sepsis develops when infection spreads systemically, causing multi-organ dysfunction. Chronic pain and illness lead to progressive weight loss and debilitation. Secondary hepatic lipidosis may develop from prolonged anorexia. Adhesions from chronic inflammation can affect function of adjacent organs. Recognizing these potential complications emphasizes the importance of prompt diagnosis and appropriate treatment for seminal vesicle disease.