2027 ICD-10-CM Diagnosis Code B66.3Fascioliasis

ICD-10-CM Codes›A00–B99›B65-B83›B66

ICD-10-CM B66.3
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

B66.3 is a billable ICD-10-CM diagnosis code for fascioliasis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 441 through 443. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 8 closely related codes. 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to B66.3: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

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

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name B66.3, its category, or a range that includes it.

Applicable To 1

These notes mention B66.3.

  • B81.4 Mixed intestinal helminthiases
    Infection due to intestinal helminths classified to more than one of the categories B65.0-B81.3 and B81.8 names B65.0-B81.3, which includes this code

Code First 1

These codes say to code first a condition named in the note, and B66.3 is one of the conditions named.

  • K67 Disorders of peritoneum in infectious diseases classified elsewhere
    helminthiasis (B65.0 -B83.9) names B65.0 -B83.9, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About B66.3Overview

What is the ICD-10 code for fascioliasis?

The ICD-10-CM code for fascioliasis is B66.3 (sometimes written as B663). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does B66.3 group to?

When fascioliasis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 442, 441, 443, with relative weights from 0.6890 to 1.8226 depending on complications. Higher weights mean higher Medicare reimbursement.

Is B66.3 a CC or MCC?

CMS lists B66.3 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 8 closely related codes in its exclusion list.

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.