Etiology: Syphacia muris is the most common pinworm found in rats, Syphacia obvelata is uncommonly seen.
Incidence: Incidence of infection is moderate.
Transmission: Transmission occurs via ingestion of ova.
Syphacia species adult females migrate from the cecum through the colon to the rectum, and deposit their eggs in a bolus on the perianal area. Eggs of Syphacia species are infective within 5-20 hours. The prepatent periods of Syphacia obvelata and Syphacia muris are 11-15 and 8-11 days, respectively.
Distribution: Adult Syphacia species are found in the cecum.
Clinical Signs: Clinical signs are not usually observed. Occasionally, heavy loads of pinworms may result in rectal prolapse or perianal irritation.
Cellophane tape test of the perianal area should be used to detect ova of the Syphacia species.
Place opened cecum and colon in a Petri dish containing saline. In a short amount of time, the pinworms will migrate out of the gut lumen into the saline. The pinworms can be detected with a dissecting microscope and speciated with use of light microscopy.
Syphacia muris: Round esophageal bulb. Small cervical alae (A.).
Female: 2.8 – 4 0 mm long. Vulva in anterior 1/4 of body.
Male: 1.2 – 1.3 mm long. Tail is long and pointed. 3 ventral mammelons: anterior mammelon is placed at the middle of the body, lengthwise.
Ova: 72-82 x 25-36 µm. Thin-shelled, ellipsoidal, flattened on one side (B.).
Syphacia obvelata: Round esophageal bulb. Small cervical alae.
Female: 3.4 – 5 8 mm long. Vulva in anterior 1/6 of body.
Male: 1.1 – 1.5 mm long. Tail is long and pointed. 3 ventral mammelons. Center mammelon is placed at the middle of the body, lengthwise.
Ova: 118-151 x 33-55 µm. Thin-shelled, banana-shaped.