Under-reporting giardiasis: time to consider the public health implications

Area of Science:

• Medical Parasitology
• Infectious Diseases
• Gastroenterology

Background:

• Giardiasis, caused by Giardia duodenalis, is a prevalent global gastrointestinal infection.
• Locally acquired cases in the UK are frequently underdiagnosed due to misconceptions linking giardiasis solely to foreign travel.
• Infections can lead to persistent irritable bowel syndrome-like symptoms.

Purpose of the Study:

• To evaluate the effectiveness of existing selection criteria for Giardia duodenalis testing in a large Scottish Health Board.
• To determine the proportion of laboratory-confirmed giardiasis cases that would have been missed under previous diagnostic guidelines.
• To advocate for improved testing strategies for Giardia duodenalis.

Main Methods:

• A change in testing methodology led to the screening of all stools for Giardia duodenalis.
• Clinical details were collected for 28 positive cases identified via ELISA and microscopy.
• These cases were assessed against the previous selection criteria, which included travel history and specific clinical indicators.

Main Results:

• Ninety-three percent (26 out of 28) of confirmed Giardia duodenalis cases would have been excluded by the previous selection criteria.
• Only two of the nine patients who reported foreign travel had visited 'high-risk' regions.
• Seven travel-associated cases would have been missed due to travel to perceived 'low-risk' areas.

Conclusions:

• Current selection criteria for Giardia duodenalis testing are inadequate and lead to significant underdiagnosis of locally acquired infections.
• Broadening testing to include all routinely submitted stools is recommended to ensure accurate identification and effective treatment.
• Enhanced diagnostic strategies are crucial for managing this neglected parasitic pathogen.