Piloting Enhanced Surveillance of Giardiasis in Maine

BACKGROUND: Giardiasis is a diarrheal illness caused by the parasite Giardia intestinalis which may result in an asymptomatic infection or symptoms lasting 1-2+ weeks, including diarrhea, abdominal cramps, gas, and dehydration. Maine does not investigate giardiasis, not allowing for characterization of state-specific risk factors. Maine recognized giardiasis surveillance needed prioritization when a recent surveillance system evaluation cited an incidence of 16.4 per 100,000, over three times the national rate of 4.8 per 100,000 in 2013. The analysis also identified that the clinical component of the updated 2011 federal case definition was not adopted, which requires clinical confirmation via healthcare providers. This pilot was developed to assess the feasibility, necessary resources, and benefits of implementing investigations for giardiasis in Maine.

METHODS: Enhanced surveillance calls for application of the updated case definition to differentiate between symptomatic cases and asymptomatic carriers through follow-up with reporting providers, followed by case interviews to discern exposure risks. Descriptive statistics from enhanced surveillance reports were analyzed using SAS 9.3 for six months (June-November). Additionally, qualitative feedback regarding the sustainability of enhanced surveillance was solicited from stakeholders.

RESULTS: Maine received 109 reports of giardiasis from June 1, 2014 to November 30, 2014. Of these reports, 67% (n=73) were confirmed symptomatic cases and 30% (n=33) were asymptomatic carriers who did not meet the case definition; 3% (n=3) were probable epi-linked cases identified by symptomatic interviewees. Thirty-four percent of cases (n=25) cases specifically noted exposure to untreated water. The majority of reports occurred in August, September, and October; these months also represent high-incidence times for various other notifiable conditions. Ten (13.7%) cases were lost-to-follow up. Healthcare provider interviews took approximately 10 minutes; case interviews took 20-30 minutes to complete after an average of 1.7 attempts to contact the case.

CONCLUSIONS: This new approach of interviewing cases would align Maine’s giardiasis surveillance with the updated 2011 national surveillance case definition. However, the increased surveillance burden of case interviews did not provide as many anticipated benefits to offset its time and resource cost.  Additionally, infections were noted among expected primary exposure risks including untreated water from natural water sources. Although certain risks were recognized and will aid in prevention efforts specific to Maine, no preventable clusters or outbreaks were identified. From these results, Maine will adopt an abridged process for healthcare provider follow-up only, to comply with the newest case definition.