section name header

Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • The indolizidine alkaloid slaframine, or “slobber factor,” is a mycotoxin produced by the “blackpatch” fungus Rhizoctonia leguminicola
  • Slaframine is a pathogen of legumes, usually red clover (Trifolium pratense)
  • Recent research involving nucleic acid sequencing suggests that the blackpatch fungus should be reclassified into the phylum Ascomycota as a new genus of ascomycete
  • Other, less common substrates include alfalfa (Medicago sativa) and ladino or white clover (Trifolium repens)
  • Following ingestion, slaframine is converted to an active metabolite (a ketoimine) in the liver that has a high affinity for the muscarinic receptor subtype responsible for regulation of exocrine glands (salivary glands and pancreas)
  • The “blackpatch” fungus produces another indolizidine alkaloid, swainsonine, that may lead to signs including stiffness, weight loss, and violent behavior

Signalment!!navigator!!

There are no breed, age, or sex predilections.

Signs!!navigator!!

  • Onset of hypersalivation (drooling) within hours of ingestion is the hallmark of this condition. Polydipsia is a consequence of fluid loss
  • Less commonly reported signs include anorexia, weight loss, excessive lacrimation, polyuria, pollakiuria, abortion, colic, and diarrhea. Neurologic signs including stiffness and violent behavior may occur in slobbering horses in which significant ingestion of swainsonine has occurred

Causes and Risk Factors!!navigator!!

  • Blackpatch is the fungal disease of clover associated with slaframine production. The plant pathogen, R. leguminicola, is most likely to grow on clover during warm, wet, humid weather
  • A moist, humid environment with a temperature range of 25–29°C (the fungus does not grow at temperatures below 25°C) and a substrate pH of 5.9–7.5 is necessary to support growth. The fungus appears as dark spots or concentric rings on infected leaves and stems. Contaminated seed spreads the fungus. Consumption of infected pastures or second-cutting forage is usually associated with intoxication
  • Geographic locations in which blackpatch has been confirmed include the midwestern and southeastern USA, Canada, Brazil, Japan, and the Netherlands

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Excessive salivation (sialorrhea) may result from dental disease, stomatitis, or foreign objects lodged in the oral cavity or the pharynx
  • Ptyalism may result from inflammation of the oral mucosa or salivary glands by penetrating wounds or plant awns such as foxtail
  • Hypersalivation seen in organophosphate and carbamate poisoning is associated with more life-threatening signs of dyspnea, colic, and diarrhea
  • Staggering, nervousness, and lack of coordination may also be seen in animals affected with swainsonine toxicosis associated with locoism

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

  • Diagnosis is usually based on recognition of rapid onset of profuse salivation associated with consumption of legume forage infected with R. leguminicola
  • Chemical analysis of suspect forage will confirm the presence of slaframine
  • Slaframine can be detected in plasma samples obtained from affected animals
  • Plant pathologists can confirm blackpatch disease on suspect forages

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

N/A

Treatment ⬆ ⬇

TREATMENT

Although specific antidotes are not available or in most cases necessary, introduction of uncontaminated forage will resolve the condition in 1–3 days.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

The administration of atropine has been suggested for severe cases. Empirical evidence suggests that atropine given prior to exposure will prevent hypersalivation, although administration after the onset of hypersalivation is not particularly effective. Atropine should be used cautiously in horses because the risk of gastrointestinal side effects is significant (ileus, colic, etc.).

Contraindications/Possible Interactions!!navigator!!

N/A

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Resolution of the problem occurs when horses are provided with uncontaminated forage.

Patient Monitoring!!navigator!!

N/A

Prevention/Avoidance!!navigator!!

Storage of contaminated hay for several months results in significant reduction in toxicity. Red clover hay containing 50–100 ppm slaframine contained only about 7 ppm after 10 months of storage. Reseeding with newer clover varieties that are resistant to Rhizoctonia infection can solve persistent problems on a specific premises.

Possible Complications!!navigator!!

N/A

Course and Prognosis!!navigator!!

Removal of contaminated forage results in uncomplicated recovery in 1–3 days.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Suggested Reading ⬆ ⬇

Croom WJ, Hagler WM, Froetschel MA, Johnson AD. The involvement of slaframine and swainsonine in slobbers syndrome: a review. J Anim Sci 1995;73:1499–1508.

Kagan IA. Blackpatch of clover, cause of slobbers syndrome: a review of the disease and the pathogen, Rhizoctonia leguminicola. Front Vet Sci 2016;3:3.

Author(s) ⬆

Authors: Stan W. Casteel and Philip J. Johnson

Consulting Editors: Wilson K. Rumbeiha and Steve Ensley