Epizootic Catarrhal Enteritis (ECE - Green Slime Disease)

Epizootic Catarrhal Enteritis (ECE), colloquially known as 'Green Slime Disease', is a highly contagious, acute to chronic enteric disease of domestic ferrets (Mustela putorius furo) caused by a coronavirus. The disease is characterized by a sudden onset of profuse, green, mucoid diarrhea, vomiting, anorexia, and profound weight loss. ECE primarily affects the small intestine, leading to villous atrophy, crypt hyperplasia, and a marked lymphocytic-plasmacytic enteritis. The disease was first recognized in the United States in 1993 and has since been reported worldwide in ferret populations, particularly in shelters, breeding facilities, and multi-ferret households. The clinical severity varies from subclinical infection to severe, life-threatening dehydration and malnutrition, with a higher morbidity and mortality in juvenile and geriatric ferrets. The disease is caused by a ferret enteric coronavirus (FRECV), which is distinct from the ferret systemic coronavirus (FRSCV) that causes a more systemic, often fatal disease. ECE is a significant cause of gastrointestinal disease in ferrets and requires prompt diagnosis and aggressive supportive care to reduce mortality.

The primary causative agent of Epizootic Catarrhal Enteritis is a ferret enteric coronavirus (FRECV), a positive-sense, single-stranded RNA virus belonging to the family Coronaviridae, genus Alphacoronavirus. The virus is enveloped and highly contagious, transmitted via the fecal-oral route, and can persist in the environment for weeks. The virus primarily targets the apical enterocytes of the small intestine, causing direct cytopathic effects and subsequent villous atrophy. Secondary bacterial overgrowth, particularly with Clostridium perfringens, may contribute to the severity of diarrhea. The disease is not caused by a single bacterial pathogen, but rather a viral infection that disrupts the intestinal barrier and leads to malabsorption and osmotic diarrhea. Nutritional factors, such as a sudden change to a high-carbohydrate diet, may exacerbate clinical signs. The virus is distinct from the ferret systemic coronavirus (FRSCV), which causes a different clinical syndrome characterized by granulomatous inflammation and systemic signs. The exact mechanisms of viral entry and replication are still under investigation, but it is known that the virus infects and destroys mature enterocytes, leading to a loss of absorptive surface area and a compensatory crypt hyperplasia.

Epizootic Catarrhal Enteritis affects domestic ferrets (Mustela putorius furo) of all ages, but the highest morbidity and mortality are observed in juvenile ferrets (under 1 year) and geriatric ferrets (over 5 years). The disease is highly contagious and spreads rapidly in environments with high population density, such as breeding facilities, pet stores, shelters, and multi-ferret households. The virus is shed in feces for up to 6 months after infection, even in subclinical carriers, making it difficult to control. The incubation period is typically 2 to 7 days. The disease is endemic in many ferret populations worldwide, with seroprevalence rates exceeding 80% in some colonies. There is no breed or sex predilection, but stress, poor husbandry, and concurrent diseases increase susceptibility. Wild ferrets and other mustelids may be susceptible, but the disease is primarily a concern in domesticated ferrets. The virus is resistant to many common disinfectants, but is inactivated by bleach (1:32 dilution), accelerated hydrogen peroxide, and quaternary ammonium compounds. Fomites, such as bedding, food bowls, and human hands, can transmit the virus. The disease is more common in the winter months, possibly due to increased indoor crowding and reduced ventilation.

The pathophysiology of Epizootic Catarrhal Enteritis begins with ingestion of the ferret enteric coronavirus (FRECV) and its replication in the mature enterocytes of the small intestine, particularly the jejunum and ileum. The virus causes direct cytopathic effects, leading to enterocyte necrosis and apoptosis. This results in blunting and fusion of the intestinal villi, with a marked reduction in the absorptive surface area. The loss of mature enterocytes triggers a compensatory crypt hyperplasia, with an increased mitotic rate in the crypts, but the immature enterocytes are functionally deficient, leading to malabsorption and osmotic diarrhea. The damaged intestinal mucosa becomes inflamed, with a prominent lymphocytic and plasmacytic infiltrate in the lamina propria. The inflammatory response may be exacerbated by secondary bacterial overgrowth, particularly Clostridium perfringens, which produces toxins that further damage the mucosa. The diarrhea is initially watery and green due to the presence of bile pigments and rapid intestinal transit, but may become mucoid and tenacious as the disease progresses. The loss of fluids and electrolytes leads to dehydration, electrolyte imbalances (hypokalemia, hyponatremia), and metabolic acidosis. Anorexia and vomiting contribute to weight loss and malnutrition. In severe cases, the intestinal barrier is compromised, allowing bacterial translocation and sepsis. Chronic cases may develop inflammatory bowel disease-like changes, with persistent diarrhea and weight loss. The virus may also cause a mild, transient lymphopenia in the acute phase. The disease is not typically systemic, but severe dehydration and malnutrition can lead to multi-organ failure.

Several factors predispose ferrets to Epizootic Catarrhal Enteritis. Intrinsic factors include age, with juvenile and geriatric ferrets being more susceptible to severe disease due to immature or senescent immune systems. Stress, such as that caused by weaning, transport, overcrowding, or changes in routine, increases cortisol levels and suppresses the immune response, making ferrets more vulnerable to infection. Extrinsic factors include poor husbandry, such as inadequate sanitation, improper temperature (ferrets require 15-24°C), and poor ventilation, which facilitate viral transmission. Dietary factors, such as a sudden change to a high-carbohydrate, low-protein diet, can alter the intestinal microbiome and increase susceptibility. Concurrent diseases, such as Helicobacter mustelae infection, inflammatory bowel disease, or adrenal gland disease, can compromise the intestinal barrier and immune function. The use of immunosuppressive drugs, such as corticosteroids, can also increase susceptibility. The presence of subclinical carriers in a population is a major risk factor for outbreaks. Lack of vaccination (there is no commercial vaccine for ECE) and lack of quarantine protocols for new ferrets are significant management-related risk factors.

The clinical signs of Epizootic Catarrhal Enteritis vary depending on the stage and severity of the disease. The acute phase typically begins with a sudden onset of lethargy, anorexia, and vomiting. Within 24 to 48 hours, affected ferrets develop profuse, watery, green diarrhea, which is the hallmark of the disease. The diarrhea may progress to a mucoid, tenacious, 'green slime' consistency, which can be difficult to clean from the fur and environment. The feces may have a foul odor. Affected ferrets often show signs of abdominal pain, such as a hunched posture, teeth grinding, and reluctance to move. Dehydration develops rapidly due to fluid loss, leading to sunken eyes, dry mucous membranes, and decreased skin turgor. Weight loss is significant, often exceeding 10% of body weight within a few days. In severe cases, hypothermia, bradycardia, and collapse may occur. Chronic cases may present with intermittent diarrhea, poor appetite, and progressive weight loss, with a pot-bellied appearance due to thickened intestines. Some ferrets may be subclinical carriers, showing no clinical signs but shedding the virus. Physical examination may reveal a thickened, doughy abdomen on palpation, and in chronic cases, mesenteric lymphadenopathy. Fever is uncommon, but mild hyperthermia may be present. The disease can be fatal in severe cases, particularly in young or old ferrets, if not treated aggressively.

The differential diagnoses for Epizootic Catarrhal Enteritis in ferrets include: 1) Proliferative bowel disease (Lawsonia intracellularis infection) - causes chronic diarrhea, weight loss, and thickening of the intestines, but is more insidious and less acute than ECE; diagnosis via PCR or histopathology. 2) Helicobacter mustelae-associated gastritis and ulceration - presents with vomiting, melena, and abdominal pain, but diarrhea is less prominent; diagnosis via fecal antigen, PCR, or biopsy. 3) Inflammatory bowel disease (IBD) - chronic diarrhea, weight loss, and vomiting, but no acute green slime diarrhea; diagnosis via intestinal biopsy. 4) Lymphoma - can cause diarrhea, weight loss, and thickened intestines, but often presents with lymphadenopathy and is more common in older ferrets; diagnosis via biopsy, imaging, and cytology. 5) Foreign body obstruction - acute vomiting and anorexia, but diarrhea is not typical; diagnosis via radiography or ultrasound. 6) Dietary indiscretion or sudden diet change - can cause acute diarrhea, but usually self-limiting and not as severe; diagnosis via history. 7) Parasitic gastroenteritis (e.g., coccidiosis, giardiasis) - can cause diarrhea, but usually less severe and more chronic; diagnosis via fecal examination. 8) Bacterial enteritis (e.g., Salmonella, Campylobacter) - can cause acute diarrhea, but often with fever and systemic signs; diagnosis via fecal culture. 9) Ferret systemic coronavirus (FRSCV) - causes systemic signs, including diarrhea, but also weight loss, splenomegaly, and granulomatous lesions; diagnosis via PCR and histopathology. 10) Toxin exposure (e.g., chocolate, plants) - can cause acute gastrointestinal signs; diagnosis via history and toxin screening.

The diagnostic algorithm for Epizootic Catarrhal Enteritis begins with a thorough history and physical examination, with emphasis on the characteristic green, mucoid diarrhea and rapid onset. The following steps are recommended: 1) Triage and stabilization: Assess hydration status, body weight, and vital signs. Initiate fluid therapy if dehydrated. 2) Fecal analysis: Perform fecal flotation and direct smear to rule out parasites. Submit feces for PCR testing for ferret enteric coronavirus (FRECV) and ferret systemic coronavirus (FRSCV). 3) Complete blood count (CBC) and serum biochemistry: Evaluate for dehydration, electrolyte imbalances, and organ function. 4) Abdominal radiographs: Rule out foreign body obstruction and assess for intestinal dilation or thickening. 5) Abdominal ultrasound: Evaluate intestinal wall thickness, mesenteric lymph nodes, and other organs. 6) If chronic or unresponsive to treatment, consider intestinal biopsy via endoscopy or surgery for histopathology. 7) PCR testing on feces is the most definitive non-invasive diagnostic test, but a negative result does not rule out ECE if the sample is taken late in the disease. 8) Serology (antibody detection) is not commonly used for diagnosis but may be useful for epidemiological studies. 9) Response to treatment can also support the diagnosis. The diagnostic algorithm should be adapted based on the clinical presentation and available resources.

Laboratory findings in Epizootic Catarrhal Enteritis are non-specific but supportive of the diagnosis. Hematology may show a mild leukopenia in the acute phase due to lymphopenia, followed by a leukocytosis with a left shift if secondary bacterial infection occurs. The packed cell volume (PCV) may be elevated due to dehydration, but may decrease if there is blood loss or chronic disease. Serum biochemistry typically reveals dehydration (elevated total protein, albumin, and BUN), electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia), and metabolic acidosis (decreased bicarbonate). In chronic cases, hypoalbuminemia may be present due to protein-losing enteropathy. Liver enzymes (ALT, AST) may be mildly elevated due to hepatic lipidosis from anorexia. Fecal analysis may show no specific pathogens, but PCR testing for FRECV is the most sensitive and specific test. Fecal samples should be collected fresh and submitted to a laboratory that offers ferret coronavirus PCR. Serology (antibody detection) is not commonly used for diagnosis but may be useful for epidemiological studies. Urinalysis may show concentrated urine due to dehydration. In severe cases, blood gas analysis may reveal metabolic acidosis. Overall, laboratory findings are supportive but not pathognomonic, and diagnosis is confirmed by PCR or histopathology.

Imaging findings in Epizootic Catarrhal Enteritis are non-specific but can help rule out other causes of gastrointestinal signs. Abdominal radiographs may show gas-filled loops of small intestine, indicating ileus, and a lack of fecal material in the colon. There may be a generalized loss of serosal detail due to dehydration or peritonitis. In chronic cases, the intestinal walls may appear thickened. Abdominal ultrasound is more sensitive and may reveal thickening of the small intestinal wall, particularly in the jejunum and ileum, with loss of normal layering. The mesenteric lymph nodes may be enlarged and hypoechoic. The stomach may be empty, and there may be free fluid in the abdomen in severe cases. Ultrasound can also rule out foreign bodies, intussusception, or neoplasia. Endoscopy is useful for direct visualization of the duodenum and jejunum, which may appear erythematous, friable, and with a blunted villous pattern. Biopsies can be taken during endoscopy for histopathology. Advanced imaging such as CT or MRI is rarely needed but may be used to evaluate for metastatic disease or other complications. Imaging is essential to rule out surgical emergencies and to guide biopsy collection.

Cytology and histopathology are important for diagnosing Epizootic Catarrhal Enteritis, especially in chronic cases. Fine-needle aspiration of enlarged mesenteric lymph nodes may show reactive lymphoid hyperplasia or, in cases of ferret systemic coronavirus, granulomatous inflammation. Intestinal biopsy via endoscopy or surgery is the gold standard for histopathological diagnosis. Histopathology of the small intestine reveals villous atrophy, blunting, and fusion, with crypt hyperplasia. The lamina propria is infiltrated with lymphocytes and plasma cells, and there may be an increased number of intraepithelial lymphocytes. In acute cases, there may be necrosis of enterocytes and mucosal erosion. In chronic cases, there may be fibrosis and architectural distortion. Immunohistochemistry can be performed to detect coronavirus antigens in the enterocytes. Cytology of fecal smears may show no specific findings, but can rule out parasites or bacterial overgrowth. Histopathology is also essential to rule out other causes of chronic diarrhea, such as inflammatory bowel disease or lymphoma. The presence of characteristic histopathological changes, combined with positive PCR, confirms the diagnosis.

Treatment of Epizootic Catarrhal Enteritis is primarily supportive and symptomatic, as there is no specific antiviral therapy. The goals are to correct dehydration, electrolyte imbalances, provide nutritional support, and manage secondary bacterial infections. The following treatment protocol is recommended: 1) Fluid therapy: Administer isotonic crystalloids (e.g., Lactated Ringer's solution) subcutaneously (SC) or intravenously (IV) at a rate of 60-100 ml/kg/day, adjusted based on hydration status. In severe dehydration, IV fluids are preferred, with a bolus of 10-20 ml/kg over 15-30 minutes, followed by maintenance. Add potassium chloride (KCl) to fluids at a rate of 20-30 mEq/L if hypokalemia is present. 2) Nutritional support: Offer a highly digestible, low-residue diet, such as a high-quality ferret food or a veterinary gastrointestinal diet (e.g., Hill's i/d). If anorexic, syringe-feed a liquid diet (e.g., Oxbow Critical Care for Carnivores) at a rate of 10-20 ml/kg every 4-6 hours. 3) Antiemetics: If vomiting is severe, administer maropitant (Cerenia) at 1 mg/kg SC once daily, or metoclopramide at 0.2-0.5 mg/kg SC/PO every 8 hours. 4) Gastrointestinal protectants: Sucralfate at 100 mg/kg PO every 8 hours may help coat the intestinal mucosa. 5) Antibiotics: To control secondary bacterial overgrowth, administer amoxicillin-clavulanate (Clavamox) at 12.5-25 mg/kg PO every 12 hours, or metronidazole at 20 mg/kg PO every 12 hours. 6) Probiotics: Administer a ferret-specific probiotic to help restore normal gut flora. 7) Antidiarrheals: Avoid using antimotility agents, as they can worsen the condition. 8) Isolation: Isolate affected ferrets to prevent spread. 9) Environmental disinfection: Thoroughly clean and disinfect the environment with bleach (1:32 dilution) or accelerated hydrogen peroxide. 10) In chronic cases, consider immunosuppressive therapy (e.g., prednisone at 0.5-1 mg/kg PO every 12 hours) if inflammatory bowel disease is suspected, but only after ruling out infectious causes. Treatment should be continued until clinical signs resolve, which may take 1-2 weeks in acute cases, but chronic cases may require long-term management.

The prognosis for Epizootic Catarrhal Enteritis is generally good with prompt and aggressive supportive care, but it can be guarded in severe cases, especially in juvenile or geriatric ferrets. The mortality rate is low (less than 5%) in well-managed cases, but can be higher in outbreaks with poor husbandry. Factors that worsen the prognosis include severe dehydration, hypothermia, sepsis, and concurrent diseases. Ferrets that survive the acute phase typically recover within 1-2 weeks, but some may develop chronic diarrhea and weight loss, which can be difficult to manage. Chronic cases may require long-term dietary management and immunosuppressive therapy. The virus may be shed for up to 6 months after recovery, so recovered ferrets should be considered potentially infectious. The prognosis is excellent for ferrets that receive early fluid therapy and nutritional support. Negative prognostic indicators include persistent vomiting, severe lethargy, and lack of response to treatment within 48 hours. Overall, the prognosis is favorable with appropriate care, but the disease can be fatal in severe cases.

Follow-up care for ferrets with Epizootic Catarrhal Enteritis is essential to ensure complete recovery and prevent recurrence. The following schedule is recommended: 1) Re-check examination within 3-5 days after initiation of treatment to assess hydration, weight, and clinical response. 2) Monitor body weight daily during the acute phase, and then weekly until the ferret has regained its normal weight. 3) Serial fecal PCR testing for FRECV may be performed every 2-4 weeks to monitor viral shedding, but it is not necessary in all cases. 4) If chronic diarrhea persists, perform a re-check examination and consider intestinal biopsy to rule out inflammatory bowel disease. 5) Provide dietary recommendations, including a high-quality, high-protein, low-carbohydrate diet, and avoid sudden diet changes. 6) Advise owners on environmental disinfection and quarantine protocols for new ferrets. 7) In multi-ferret households, monitor all ferrets for signs of disease and isolate any new arrivals for at least 2 weeks. 8) Long-term follow-up every 6-12 months is recommended for ferrets that have had chronic ECE to monitor for the development of inflammatory bowel disease or other gastrointestinal issues. 9) Ensure that the ferret is up-to-date on other vaccinations (e.g., distemper, rabies) to prevent concurrent infections. 10) Provide client education on the importance of good hygiene and stress reduction to prevent future outbreaks.

Clinical Pearls: 1) The characteristic 'green slime' diarrhea is a strong indicator of ECE, but not all ferrets with ECE will have green diarrhea; some may have brown or yellow diarrhea. 2) Early aggressive fluid therapy is the most critical aspect of treatment; consider intraosseous (IO) fluid administration in severely dehydrated ferrets if IV access is difficult. 3) Ferrets are prone to hypoglycemia during anorexia, so monitor blood glucose and add dextrose to fluids if needed. 4) Use a high-quality, highly digestible diet, and consider adding a probiotic to help restore gut flora. 5) Isolate affected ferrets immediately and use strict biosecurity measures to prevent spread. 6) PCR testing on feces is the most reliable diagnostic test; collect samples early in the disease. 7) In chronic cases, consider a trial of immunosuppressive therapy (e.g., prednisone) if inflammatory bowel disease is suspected, but only after ruling out infectious causes. 8) Ferrets with ECE may have a secondary Helicobacter mustelae infection; consider treating with amoxicillin and metronidazole if gastritis is suspected. 9) Use a fecal scoring system to monitor response to treatment. 10) Educate owners about the importance of quarantine for new ferrets. Clinical Pitfalls: 1) Avoid using antidiarrheal agents such as loperamide, as they can worsen the condition by slowing intestinal transit and allowing bacterial overgrowth. 2) Do not use corticosteroids in the acute phase, as they can immunosuppress the ferret and worsen the viral infection. 3) Avoid using non-steroidal anti-inflammatory drugs (NSAIDs) due to the risk of gastrointestinal ulceration. 4) Do not assume that a negative PCR result rules out ECE, as the virus may be shed intermittently. 5) Do not neglect to check for concurrent diseases, such as adrenal gland disease or lymphoma, which can complicate the clinical picture. 6) Avoid using fipronil or other toxic substances in ferrets, as they can be fatal. 7) Do not forget to disinfect the environment thoroughly, as the virus can survive for weeks. 8) Do not underestimate the importance of nutritional support; ferrets can develop hepatic lipidosis if anorexic for more than 48 hours. 9) Do not use human medications without veterinary guidance, as many are toxic to ferrets. 10) Do not delay treatment, as severe dehydration can lead to death within 24-48 hours.

The following drug protocols are based on Carpenter's Exotic Animal Formulary (5th edition) and current literature for ferrets: 1) Fluid therapy: Lactated Ringer's solution (LRS) or Normosol-R, SC or IV, at 60-100 ml/kg/day. For shock, administer 10-20 ml/kg IV bolus over 15-30 minutes, then reassess. Add KCl at 20-30 mEq/L if hypokalemia is present. 2) Antiemetics: Maropitant (Cerenia) at 1 mg/kg SC once daily; Metoclopramide at 0.2-0.5 mg/kg SC/PO every 8 hours. 3) Gastrointestinal protectants: Sucralfate at 100 mg/kg PO every 8 hours; Famotidine at 0.5-1 mg/kg PO/SC every 12-24 hours. 4) Antibiotics: Amoxicillin-clavulanate (Clavamox) at 12.5-25 mg/kg PO every 12 hours; Metronidazole at 20 mg/kg PO every 12 hours; Enrofloxacin (Baytril) at 5-10 mg/kg PO/SC every 12 hours (use with caution in young ferrets). 5) Probiotics: Ferret-specific probiotic (e.g., Proviable-DC) at 1/2 packet PO every 12 hours. 6) Nutritional support: Oxbow Critical Care for Carnivores, 10-20 ml/kg PO every 4-6 hours via syringe. 7) Immunosuppressive therapy (for chronic cases): Prednisone at 0.5-1 mg/kg PO every 12 hours, tapering over 2-4 weeks. 8) Analgesics: Buprenorphine at 0.01-0.03 mg/kg SC/IM every 8-12 hours if abdominal pain is present. 9) Antiparasitics (if parasites are found): Fenbendazole at 20 mg/kg PO every 24 hours for 5 days; Metronidazole at 20 mg/kg PO every 12 hours for 5 days. 10) Emergency drugs: Atropine at 0.04 mg/kg SC/IM as needed for bradycardia; Epinephrine at 0.02-0.1 mg/kg IV/IO as needed for cardiac arrest. All dosages should be adjusted based on the individual patient's condition and response to therapy.

Epizootic Catarrhal Enteritis was first described in 1993 by Williams et al., who reported an outbreak of green diarrhea in a ferret shelter. Subsequent studies identified a coronavirus as the causative agent, with PCR and electron microscopy confirming the presence of a novel alphacoronavirus. A landmark study by Wise et al. (2006) characterized the ferret enteric coronavirus (FRECV) and distinguished it from the ferret systemic coronavirus (FRSCV). The study demonstrated that FRECV causes enteritis with villous atrophy and lymphocytic-plasmacytic inflammation, while FRSCV causes a systemic disease with granulomatous lesions. A study by Garner et al. (2008) evaluated the clinical and pathological features of ECE in a large cohort of ferrets, finding that the disease is highly contagious and can cause significant morbidity and mortality in young and old ferrets. Treatment recommendations are largely based on expert opinion and extrapolation from other species, as there are few controlled clinical trials. A consensus statement from the Association of Exotic Mammal Veterinarians (AEMV) recommends aggressive fluid therapy, nutritional support, and symptomatic treatment. Recent research has focused on the development of vaccines, but no commercial vaccine is currently available. A study by Murray et al. (2010) evaluated the efficacy of a recombinant vaccine in ferrets, showing promise in reducing clinical signs, but further research is needed. Overall, the evidence base for ECE is limited, and more studies are needed to establish optimal treatment protocols and preventive strategies.