Guidance Regarding Sample Collection and Refinement of Fecal Flotation Exam for the Isolation of Aspiculuris tetraptera

Abstract

Aspiculuris tetraptera continues to be a problem in rodent vivaria, in part due to difficulties in parasite detection. Although PCR testing is highly sensitive, it is expensive and does not always provide immediate results. Consequently, many institutions rely on passive fecal flotation as a quick inhouse exam for diagnosing A. tetraptera infections. To increase the sensitivity of this test, we examined multiple parameters to determine the optimal test protocol. A 30-min soaking period prior to fecal flotation for 15 min allowed fecal pellets to soften and facilitated efficient egg isolation. We also evaluated the effect of time of day, sample size, age, sex, and housing status on egg isolation. No evidence of cyclical egg shedding was found, and although larger fecal sample sizes did not result in more eggs isolated, their use reduced the incidence of false-negative exams. The most eggs were isolated from 8- and 12-wk-old mice, and as mice aged, the number of eggs isolated declined. Overall, neither sex nor housing status influenced the number of eggs isolated. Finally, examination of multiple diagnostic tests (fecal flotation exam, direct examination of cecal and colonic contents, and fecal PCR) revealed that no single test was definitive, thus indicating that multiple tests might be required to successfully screen mice with low pinworm burdens. These findings provide guidance regarding sample selection, collection, and processing to efficiently detect A. tetraptera.

Figure 1.

Summary of study parameters.

Figure 2.

Prior to flotation exam, fecal pellets were either soaked for 30 min (soaked) or processed immediately (nonsoaked), and the eggs isolated were counted (n = 10 trials per group; solid horizontal lines indicate the median values for each group of data points; Mann–Whitney, P = 0.0084).

Figure 3.

The eggs isolated during fecal flotation from sample sizes of 2, 5, or 10 fecal pellets were counted. Larger sample size did not result in the isolation of more eggs (n = 15 trials per group; solid horizontal lines indicate median values for each group of data points; Kruskal–Wallis, P = 0.28).

Figure 4.

The number of eggs isolated by fecal flotation was evaluated in fecal pellets collected from 1600 to 0800, 0800 to 1200, or 1200 to 1600 (n = 50 cages per group; solid horizontal lines indicate median values for each group of data points; Kruskal–Wallis, P < 0.0001).

Figure 5.

Variability in egg excretion was examined over the course of 5 d by using individual cages of group-housed mice (cage nos. 1 through 5 contained male mice, and cage nos. 6 through 10 contained female mice). Each line represents a different cage.

Figure 6.

Eggs isolated by fecal flotation of samples collected from 8-, 12-, 16-, 20-, and 24-wk-old mice were counted. More eggs were isolated from 8- and 12-wk-old mice compared with older mice (n = 25 cages at each time point; solid horizontal lines indicate median values for each group of data points; Kruskal–Wallis with Dunn multiple comparison posthoc; *, P < 0.05; †, P < 0.01; §, P < 0.0001).

Figure 7.

Eggs isolated by fecal flotation of samples collected from 8-, 12-, 16-, 20-, and 24-wk-old mice housed as breeders (Breeding), in groups (Group), and singly (Single) were evaluated. Over time, fewer eggs were isolated from all mice, regardless of housing status, as they cleared their infections (n = 5 to 10 cages per time point per housing group; data presented as mean ± SEM; *, P < 0.05, Tukey multiple-comparison posthoc).