Helminths of the Cotton Rat in Southern Virginia, with Comments on the Sex Ratios of Parasitic Nematode Populations

Abstract

Thirty-eight cotton rats, Sigmodon hispidus, were collected in Virginia and examined for their helminth fauna. The cestodes recovered were: Choanotaenia nebraskensis (8% incidence), Hymenolepis diminuta (18%) and Raillietina bakeri (18%) from the intestine, and larval Taenia taeniaeformis (16%) from the liver. This is the first report of C. nebraskensis from the cotton rat. The nematodes found were Longistriata adunca (76%) from the intestine and Mastophorus muris (42%) from the stomach. The heaviest infections were produced by L. adunca (41 worms per infected host) and R. bakeri (21 worms per infected host). Twenty hosts harbored two or more species of worms. Mastophorus muris and C. nebraskensis were more common in female than male hosts. The sex ratio of the 1201 L. adunca collected was determined. Young cotton rats have a 1: 1 female worm to male worm sex ratio. Older hosts have more female than male worms. INTRODUCTION The helminth fauna of the cotton rat, Sigmodon hispidus, is relatively well known. Baylis (1945) and Melvin and Chandler (1950) published species lists of cotton rat helminths from the southern United States and Florida and Texas, respectively. Harkema and Kartman (1948) compared the helminth fauna and ectoparasites of cotton rats from North Carolina and Georgia. They studied the general incidence and intensity of infection, seasonal variation and other host-parasite relationships. Hugghins (1951) surveyed and compared the helminths and ectoparasites of roof rats and cotton rats in Texas. Lanier (1951) studied the helminths of Sigmodon hispidus in Florida. Recently, Kinsella (1974) compared the helminths of cotton rats from saltwater and freshwater marshes in northern Florida. He also included a checklist of all the helminths known from the cotton