Cystic prostatic disease associated with adrenocortical lesions in the ferret (Mustela putorius furo)

Gynaecomastia in a male neutered cat with an adrenal tumour and associated hyperprogesteronism, hypercortisolism and hyperaldosteronism

Case summary

A 7-year-old male neutered domestic longhair cat was presented with chronic progressive gynaecomastia, polydipsia, polyphagia, weight loss and poor fur regrowth. Sexualised behavioural changes were not reported and virilisation was not present on physical examination. Pertinent haematology, biochemistry and urinalysis findings at the time of referral included mild hypokalaemia. Left adrenomegaly and mild prostatomegaly were identified on a CT scan. Evaluation of adrenal hormones with a low-dose dexamethasone suppression test, serum progesterone, testosterone, oestradiol, plasma aldosterone, renin, plasma metanephrine and normetanephrine measurement supported a diagnosis of hyperprogesteronism, hyperaldosteronism and hypercortisolism. Adrenalectomy was performed and histopathology was consistent with an adrenocortical tumour. Clinical signs and hormone elevations resolved postoperatively.

Relevance and novel information

To our knowledge, this is the second report of gynaecomastia secondary to an adrenal tumour in a male neutered cat and the first associated with hyperprogesteronism.

Disorders of the Urinary and Reproductive Systems in Ferrets

Urogenital lesions are relatively common in ferrets. Renal disease is diagnosed as in traditional small animal medicine; however, peculiarities in ferrets include physiologically low levels of creatinine. Renal cysts are very common in ferrets but are usually incidental findings. Uroliths are usually composed of struvite or cystine. Urethral obstruction in male ferrets is predominantly caused by adrenal-associated prostatic disease. Spontaneous cystitis is rare in ferrets. Primary reproductive disease is uncommon in ferrets in the United States where animals are usually neutered at 6 weeks of age. In other countries, ferrets either remain unneutered or are neutered at 5 to 6 months of age. Ferrets are seasonal breeders, and female are induced ovulators. Prolonged estrus and hyperestrogenism often causes profound bone marrow suppression.

Endocrinopathy and Aging in Ferrets

Ferrets have become more popular as household pets and as animal models in biomedical research in the past 2 decades. The average life span of ferrets is about 5-11 years with onset of geriatric diseases between 3-4 years including endocrinopathies, neoplasia, gastrointestinal diseases, cardiomyopathy, splenomegaly, renal diseases, dental diseases, and cataract. Endocrinopathies are the most common noninfectious disease affecting middle-aged and older ferrets. Spontaneous neoplasms affecting the endocrine system of ferrets appear to be increasing in prevalence with a preponderance toward proliferative lesions in the adrenal cortex and pancreatic islet cells. Diet, gonadectomy, and genetics may predispose ferrets to an increased incidence of these endocrinopathies. These functional proliferative lesions cause hypersecretion of hormones that alter the physiology and metabolism of the affected ferrets resulting in a wide range of clinical manifestations. However, there is an apparent dearth of information available in the literature about the causal relationship between aging and neoplasia in ferrets. This review provides a comprehensive overview of the anatomy and physiology of endocrine organs, disease incidence, age at diagnosis, clinical signs, pathology, and molecular markers available for diagnosis of various endocrine disorders in ferrets.

Reproductive Medicine in Ferrets

In the United States, desexing is performed routinely in ferrets at the age of 6 weeks, therefore reproductive tract diseases are not so common. However, in Europe most ferrets are desexed when they are several months old, or they are kept as intact animals. For this reason, diseases of the reproductive organs and a prolonged estrus are far more frequent in Europe than in the United States. This article summarizes and reviews the anatomy, reproductive physiology, management of reproduction (including surgical and hormonal contraception) and reproductive tract diseases in male and female ferrets.

Biology and Diseases of Ferrets

Ferrets (Mustela putorius furo) belong to the ancient family Mustelidae, which is believed to date back to the Eocene period, some 40 million years ago. The taxonomic groups in the family Mustelidae, as recognized by Nowak (1999), include 67 species in 25 genera from North, Central, and South America; Eurasia; and Africa. No other carnivore shows such diversity of adaptation, being found in a wide variety of ecosystems ranging from arctic tundra to tropical rainforests. Mustelids have retained many primitive characteristics, which include relatively small size, short stocky legs, five toes per foot, elongated braincase, and short rostrum (Anderson, 1989). The Mustelinae is the central subfamily of the Mustelidae. The best-known members of the Mustelinae are the weasels, mink, ferrets (genus Mustela), and the martens (genus Martes) (Anderson, 1989). The genus Mustela is divided into five subgenera: Mustela (weasels), Lutreola (European mink), Vison (American mink), Putorius (ferrets), and Grammogale (South American weasels). The smallest member of the Mustelidae family is the least weasel (Mustela nivalis), which weighs as little as 25 g, and the largest member is the sea otter (Enhydra lutris), which can weigh as much as 45 kg (Nowak, 1999).

Advanced diagnostic approaches and current medical management of insulinomas and adrenocortical disease in ferrets (Mustela putorius furo)

Endocrine neoplasia is the most common tumor type in domestic ferrets, especially in middle-aged to older ferrets. Islet cell tumors and adrenocortical tumors constitute the major types of endocrine neoplasms. Insulinoma is a tumor that produces and releases excessive amounts of insulin. Evaluation of fasted blood glucose levels provides a quick diagnostic assessment for the detection of insulinomas. Use of glucocorticoids, diazoxide, and diet modification are some of the medical treatment options for insulinomas. Adrenocortical neoplasia in ferrets usually overproduces one or more sex hormones. Sex hormones which can result in progressive alopecia, vulvar swelling in females, and prostagomegaly in males. Abdominal ultrasonography and sex hormone assays can be used to diagnose adrenocortical neoplasms. Drugs such as leuprolide acetate, deslorelin acetate, and the hormone melatonin can be used to treat adrenocortical neoplasms in ferrets when surgery is not an option.

FERRETS

This chapter familiarizes veterinarians with basic knowledge of ferret biology, medicine, surgery, and care. Ferrets have a long, slender body with short muscular legs, a long thin tail, small eyes, and short ears. The life span of the ferret is 5 to 8 years. Ferrets may be housed singly or in groups, inside or outside of a house. When kept outdoors, however, they must be protected from extreme weather. Ferrets have difficulty tolerating temperatures above 90°F or below 20°F, and appropriate precautions must be taken to prevent their exposure to these extremes. Ferrets are carnivorous and require a suitable diet. A diet that is high in good-quality animal protein and fat and low in complex carbohydrates and fiber is recommended. Ferrets are routinely immunized against canine distemper virus (CDV) and rabies virus. Ferrets are quite susceptible to CDV, and there is a 100% mortality rate in unvaccinated ferrets infected with CDV. When a new ferret is brought into the household, a quarantine period is recommended before introducing it to other animals, particularly other ferrets. The purpose of the quarantine period is to identify and prevent transmission of infectious disease potentially carried by the new ferret. The duration of this period allows for the development of any clinical signs in a seemingly healthy ferret following entrance into the new household.

Prostatic squamous metaplasia in a cat with interstitial cell neoplasia in a retained testis

An 11-year-old cat with a retained testis was presented with a chronic history of dysuria and bladder atony. Medical therapy failed to alleviate the clinical signs. Contrast radiography demonstrated a diffusely narrowed urethra. During a celiotomy and prepubic urethrostomy, a retained testis, stenosed urethra, and irregularly enlarged prostate were observed. Histopathologic diagnosis was retained testis with a well-differentiated interstitial cell tumor, a poorly differentiated interstitial cell tumor, and marked squamous metaplasia of the prostatic epithelium with suppurative prostatitis. Neoplastic interstitial cells were immunoreactive for Melan A, consistent with reports of Melan A expression in steroid hormone-producing tissue. This is the first report of prostatic squamous metaplasia associated with testicular neoplasia in a felid.

Laboratory Findings, Histopathology, and Immunophenotype of Lymphoma in Domestic Ferrets

Lymphoma is a common tumor in ferrets, but anatomic distribution, histomorphology, immunophenotype, laboratory abnormalities, and response to chemotherapy are incompletely defined. In this study, lymphoma was diagnosed by histopathology of tumor tissue in 29 ferrets ranging in age from 0.8 to 8.5 years, including 12 males and 17 females. Tumors involved the viscera of the abdominal cavity (n = 11), thoracic cavity (n = 1), or abdominal and thoracic cavities (n = 7); the skin (n = 2); or the viscera of both body cavities plus other sites (n = 8). Microscopically, all tumors had diffuse architecture. Assessment by histomorphology and immunophenotype classified tumors as peripheral T-cell lymphoma (n = 17), anaplastic large T-cell lymphoma (n = 5), anaplastic large B-cell lymphoma (n = 4), diffuse large B-cell lymphoma (n = 1), and Hodgkin-like lymphoma (n = 2). Cytologic evaluation of tumor tissue was diagnostic in 11 of 13 cases. Twenty-two of 27 ferrets had anemia, 2 had leukemia, and 5 were neutropenic. Common comorbid disorders were adrenal disease (n = 27) and insulinoma (n = 6). Tumors most frequently involved mesenteric lymph nodes, while enlargement of peripheral lymph nodes was uncommon (n = 3). Ferrets with Hodgkin-like lymphoma had massive enlargement of single lymph nodes. Mean survival of ferrets not immediately euthanized was 5.0 months (T-cell lymphoma) and 8.4 months (B-cell lymphoma). Ferrets treated with chemotherapy survived an average of 4.3 months (T-cell lymphoma, n = 9) or 8.8 months (B-cell lymphoma, n = 4). Results indicate that lymphomas in ferrets most commonly affect abdominal viscera, may be amenable to cytologic diagnosis, are frequently associated with anemia and, in some cases, may be chemosensitive, resulting in relatively long survival times.

Long-term outcome of domestic ferrets treated surgically for hyperadrenocorticism: 130 cases (1995-2004)

OBJECTIVE

To determine the long-term survival rate and factors that affect survival time of domestic ferrets treated surgically for hyperadrenocorticism.

STUDY DESIGN

Retrospective case series.

ANIMALS

130 ferrets with hyperadrenocorticism that were treated surgically.

PROCEDURES

Medical records of ferrets surgically treated for hyperadrenocorticism were reviewed. Data recorded included signalment, duration of clinical signs prior to hospital admission, CBC values, serum biochemical analysis results, anesthetic time, surgical time, concurrent diseases, adrenal gland affected (right, left, or both [bilateral]), histopathologic diagnosis, surgical procedure, caudal vena caval involvement (yes or no), postoperative melena (yes or no), days in hospital after surgery, and whether clinical signs of hyperadrenocorticism developed after surgery.

RESULTS

130 ferrets were entered in the study (11 of 130 ferrets were admitted and underwent surgery twice). The 1- and 2-year survival rates were 98% and 88%, respectively. A 50% survival rate was never reached. Combined partial adrenal gland resection with cryosurgery had a significantly negative effect on survival time. No other risk factors were identified. Survival time was not significantly affected by either histopathologic diagnosis or specific affected adrenal gland (right, left, or bilateral).

CONCLUSIONS AND CLINICAL RELEVANCE

Ferrets with adrenal gland masses that were treated surgically had a good prognosis. Survival time of ferrets with hyperadrenocorticism undergoing surgery was not affected by the histologic characteristic of the tumor, the adrenal glands affected (right, left, or bilateral), or complete versus partial adrenal gland resection. Debulking was a sufficient surgical technique to allow a favorable long-term outcome when complete excision was not possible.

Adrenal gland disease in ferrets

Adrenal gland disease in ferrets is unique to this species, with clinical signs and pathophysiology different from those seen in the dog. Its prevalence is increasing; 70% of pet ferrets in the United States were affected in 2003. The exact causes of the adrenal gland changes that lead to the disease are not known. Early oophorohysterectomies and neutering, combined with the artificially prolonged photoperiod experienced by indoor pet ferrets, and a possible genetic component, may be contributing factors. Signs of adrenal gland disease include progressive hair loss, pruritus, lethargy, atrophy, and, in female ferrets, vulvar swelling. An understanding of the signs and physiologic changes is necessary for diagnosis and treatment. A review of anatomy, physiology, and current surgical and medical options is presented.

Issues to consider for preparing ferrets as research subjects in the laboratory

The domestic or European ferret (Mustela putorius furo) has been domesticated for thousands of years. Ferrets have been used for hunting and fur production, as pets, and as models in biomedical research. Despite the relatively small numbers used in the laboratory, ferrets have some unique applications including study of human influenza and severe acute respiratory syndrome (SARS)-associated corona virus. They have served as models for peptic ulcer disease, carotenoid metabolism, cystic fibrosis, and drug emesis screening, among others. Most research ferrets are males, due to estrus-related health problems in females. They may be housed conventionally and are easy to care for when their biology and behavior are understood. Due to the small number of ferret suppliers, animals are often shipped long distances, requiring air transport and intermediate handlers. It is important to minimize shipment stress, especially with weanling and pregnant animals. Additional expertise is required for success with pregnant and whelping ferrets and for rearing of neonates. The animals have specific dietary requirements, and proper nutrition is key. Successful housing requires knowledge of ferret behaviors including social behavior, eating habits, a general inquisitive nature, and a species-typical need to burrow and hide. Regular handling is necessary to maintain well-being. A ferret health care program consists of physical examination, immunization, clinical pathology, and a working knowledge of common ferret diseases. Various research methodologies have been described, from basic procedures such as blood collection to major invasive survival surgery. Ferrets have a distinct niche in biomedical research and are hardy animals that thrive well in the laboratory.

Adrenal cortical carcinomas with myxoid differentiation in the domestic ferret (Mustela putorius furo)

A total of 15 adrenocortical carcinomas with myxoid differentiation from 15 ferrets were evaluated in this retrospective study. Six of these ferrets (40%) either were euthanatized or died due to invasive and/or metastatic disease. The myxoid component was a variable part (between 5% and 95%) of the adrenal cortical neoplasm and consisted of sheets and cords of small, polygonal neoplastic cells that formed lumenlike spaces. Such spaces contained a variable amount of alcian blue (pH 2.5)-positive mucinous product (i.e., acidic mucopolysaccharides). Neoplastic cells were negative for the argentaffin reaction, but immunohistochemically they were strongly positive for vimentin and alpha-inhibin and lightly positive for synaptophysin. Proliferating cell nuclear antigen (PCNA)-labeling indices (LI) of adrenal cortical neoplastic cells within the myxoid component of the neoplasm were significantly elevated (P < 0.05) compared with those of typical neoplastic adrenal cortical cells or the adjacent nonneoplastic zona reticularis. Ultrastructurally, cells in the myxoid component exhibited a typical adrenocortical phenotype characterized by cytoplasmic lipid vacuoles, prominent rough and smooth endoplasmic reticulum, and zonula adherens. This lesion was interpreted as an adrenal cortical carcinoma with myxoid differentiation and appeared to be highly malignant based on PCNA LI, rate of invasion into adjacent tissue, and metastasis (6/15). This report is the first description of this histologic variant in the ferret, which morphologically resembled the rare myxoid variant of adrenocortical carcinoma described in humans.

Ferret urogenital diseases

Improved nutrition and client education have decreased the incidence of certain urinary tract diseases in ferrets. Early neutering programs at commercial breeding farms in the United States have also led to a marked decrease in the incidence of reproductive tract disease, especially estrogen-induced bone marrow suppression. However, the increased incidence of adrenal disease and its secondary effects on reproductive and associated urinary tract tissue presents an ongoing challenge for the clinician working with pet ferrets. Acute and chronic renal failure remain important, though less common, disease entities. It is imperative that the veterinarian working with pet ferrets be aware of the clinical presentation and clinicopathologic abnormalities associated with these syndromes.