However, weanling and immunodeficient mice may develop clinical disease. It has been reported by several investigators that young mice may develop diarrhea, dehydration, weight loss, rough coat, lethargy, abdominal distension, and hunched posture and may die, although in none of the reported cases were other potential causes of the clinical signs excluded. In severe infections, the intestine is reddened and filled with fluid and gas. Pinworms commonly infecting laboratory rodents include the rat pinworm Syphacia muris and, in mice, Syphacia obvelata and Aspicularis tetraptera. S. obvelata has also been reported to infect humans.
Life cycles are direct, with adult worms inhabiting the cecum and colon.
The eggs are very light and will aerosolize, resulting in widespread environmental contamination. Embryonated eggs are infective to another rodent and can survive for extended periods at room temperature. The prevalence of infection remains high, even in well-managed animal colonies. Pinworm burden in an infected rodent population is a function of age, sex, and host immune status. In enzootically infected colonies, weanling animals develop the greatest parasite loads, males are more heavily parasitized than females, and pinworm numbers diminish with increasing age of the host.