Characterization of rat pinworm (Syphacia muris) epidemiology as a means to increase detection and elimination

Rodent pinworms persist in many institutions, suggesting deficiencies in eradication and diagnostic processes. When pinworms are detected, treatment success is common, but false-negative test results during health surveillance or after treatment likely contribute to the continued presence of this parasite. PCR testing is not always practical, and increased information regarding the life cycle and general epidemiology of pinworm infestations could improve the sensitivity of traditional nonPCR detection methods and improve eradication efforts. We therefore investigated a pinworm (Syphacia muris) infestation in Sprague-Dawley rats (Rattus norvegicus) to develop a more accurate testing strategy. In addition, we sought to determine the duration of egg viability by using an in vitro hatching protocol to assess environmental persistence. Finally, we tested the ovicidal efficacy of a disinfectant used at our institution. Eggs were shed in higher numbers in the midafternoon as compared with other times of the day, and the sex of the host had no consistent effect on egg shedding. Egg shedding showed periodicity over time, with shedding decreasing to 0 at 2- to 3-wk intervals. Neither cecal examination nor tape tests alone reliably predicted pinworm infestation, and results of the 2 tests did not necessarily coincide. Eggs aged for as long as 7 mo remained viable, indicating a potential for recontamination from the environment. Finally, gaseous chlorine dioxide was an effective ovicidal agent, with a kill rate of 99.7%. These results suggest that strategies for S. muris eradication can be optimized to increase detection and elimination.