2026 ICD-10-CM Diagnosis Code B66.3Fascioliasis

ICD-10-CM Codes›A00–B99›B65-B83›B66

ICD-10-CM B66.3
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B66.3 is a billable ICD-10-CM diagnosis code for fascioliasis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 441 through 443. Coders also document this condition as disease caused by Fasciolidae. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Parasitic, other specified and unspecified infections.

Code Identity

ICD-10-CM Code
B66.3
Billable Status
Yes — Valid for Submission
Code Describes
Fascioliasis
Short Description
Fascioliasis
Same as the full description in the CMS dataset.
Parent Code
B66
Other fluke infections

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB65-B83Helminthiases
CategoryB66Other fluke infections
This CodeB66.3Fascioliasis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Disease caused by Fasciolidae
  • Fasciola gigantica infection
  • Infection by Fasciola
  • Infection by Fascioloides
  • Infection by Fascioloides magna
  • Nasopharyngeal fascioliasis
  • Sheep liver fluke infection

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Infection due to Fasciola gigantica
  • Infection due to Fasciola hepatica
  • Infection due to Fasciola indica
  • Sheep liver fluke disease

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Cirrhosis, cirrhotic(hepatic) (liver)
      • biliary (cholangiolitic) (cholangitic) (hypertrophic) (obstructive) (pericholangiolitic)
        • due to
          • flukes
    • Disease, diseased
      • liver (chronic) (organic)
        • fluke
          • sheep
    • Distoma hepaticum infestation
    • Distomiasis
      • bile passages
    • Distomiasis
      • hepatic
    • Distomiasis
      • liver
    • Fascioliasis
    • Flukes NEC
      • liver
    • Infection, infected, infective(opportunistic)
      • Fasciola (gigantica) (hepatica) (indica)
    • Infection, infected, infective(opportunistic)
      • sheep liver fluke
    • Infestation
      • Distoma hepaticum
    • Infestation
      • Fasciola (gigantica) (hepatica) (indica)
    • Infestation
      • fluke
        • liver (sheep)
    • Infestation
      • fluke
        • sheep liver

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF009
Parasitic, other specified and unspecified infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Fascioliasis

    liver disease caused by infections with parasitic flukes of the genus fasciola, such as fasciola hepatica.

Patient EducationClinical

Parasitic Diseases

Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Some parasitic diseases are easily treated and some are not.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert B66.3 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
121.3 Fascioliasis
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About B66.3Overview

Is B66.3 (Other fluke infections) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fascioliasis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B66.3 group to?

When fascioliasis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 441, 442, 443, with relative weights from 0.6997 to 1.7947 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of B66.3?

Under the General Equivalence Mappings, fascioliasis converts to ICD-9-CM 121.3 (fascioliasis). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.