Evaluation of the Minnesota Department of Health Giardia Surveillance System

BACKGROUND:  Giardiasis is a diarrheal illness caused by a flagellate protozoan, Giardia intestinalis (also known as G. lamblia or G. duodenalis). Transmitted by the fecal-oral route, giardiasis is the most frequently reported intestinal parasitic disease in Minnesota and the rest of the United States. The Minnesota Department of Health (MDH) began enhanced surveillance for giardiasis cases in 2013. Enhanced surveillance includes follow-up with reporting clinicians to obtain missing case information and, excluding recent immigrants, case interviews to collect symptom and exposure history. Prior to this, case interviews were conducted from 2002 to 2006, but stopped due to lack of resources. The primary intent of reintroducing case interviews in 2013 was to collect exposure data that could help identify outbreaks.

METHODS:  The system was evaluated using the current CDC recommended guidelines for evaluating public health surveillance systems. System attributes were assessed and scored on a 4-point scale (poor, fair, good, and excellent). Scores from a 5-year period of passive surveillance (2008-2012) were compared to the first year of enhanced surveillance (2013).

RESULTS:  The addition of enhanced surveillance activities benefited Minnesota residents by improving data completeness and the system’s potential to detect outbreaks. Enhanced surveillance significantly reduced the number of cases with missing data in key demographic categories: sex, race, county of residence, age, and recent immigrant status (p <0.01 for all comparisons). Integrating new data fields into the Minnesota Electronic Disease Surveillance System (MEDSS) and cross-referencing cases with those documented by the MDH refugee health program will further ensure data quality. Additionally, non-English speakers were underrepresented in case interviews due to a language barrier, and efforts to hire translators to reach these residents should continue. Despite a shift in diagnostic practices from 7% of laboratories using rapid tests in 2000 to 75% in 2013, the positive predictive value of the system remains unknown. Specimens are not submitted to the MDH Public Health Laboratory (PHL) for confirmatory testing. Enhanced surveillance is more complex, but the system was flexible enough to easily accommodate these changes. Stability of the system is dependent on external funding; benefits of enhanced surveillance should be communicated to funding partners to ensure these activities can continue.

CONCLUSIONS:  Overall, enhanced surveillance activities improved the usefulness and functionality of the system and should continue. Further integration of the system with existing structures at MDH including MEDSS, the refugee health program, and the MDH PHL will continue to improve the system’s effectiveness.