Distribution of meningeal worm (Pneumostrongylus tenuis) in deer in the southeastern United States.

Pneumostrongylus tenuis was found in the meninges of 1,197 (49.7%) of 2,409 white-tailed deer collected in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Tennessee, Virginia, and West Virginia. Infected deer were not found in South Carolina and St. Croix of the U. S. Virgin Islands. In the southeastern United States, meningeal worm appears to occur mainly in deer of oak-pine subclimax and climax deciduous forest types. It was not found in areas having a sandy soil and a predominantly pine forest. During the past few years considerable attention has been given to the biology of Pneumostrongylus tenuis Dougherty, 1945, the meningeal worm of white-tailed deer (Odocoileus virginianus). This helminth, apparently restricted to eastern North America, is noteworthy because it is a neurotropic form which generally produces a silent infection in the normal host (Anderson, 1963, 1965b; Anderson and Strelive, 1967; Lankester and Anderson, 1968) but can cause neurologic disturbances including paralysis in unusual hosts. Neurologic disease caused by P. tenuis has been produced experimentally in moose (Anderson, 1964), wapiti and mule deer (Anderson et al., 1966), woodland caribou (Anderson and Strelive, 1968), sheep (Anderson and Strelive, 1966b), and guinea pigs (Anderson and Strelive, 1966a; Spratt and Anderson, 1968). Neurologic disease associated with naturally acquired infections of meningeal worm has been reported in domestic sheep (Kennedy et al., 1952; Whitlock, 1952, 1959; Nielson and Aftosmis, 1964), moose (Smith et al., 1964; Anderson, 1965a; Kurtz et al., 1966; Karns, 1967a; Smith and Archibald, 1967; Behrend and Witter, 1968), and caribou (Behrend and Witter, 1968). The same disease probably occurs in wild wapiti in certain Received for publication 15 April 1969. * This study was supported by an appropriation from the Congress of the United States. Funds were administered and research coordinated under the Federal Aid in Wildlife Restoration Act (50 Stat. 917) and through Contract Nos. 1416-0008-676 and 14-16-0008-777, Bureau of Sport Fisheries and Wildlife, U. S. Department of the Interior. parts of eastern North America (Anderson et al., 1966). Although P. tenuis occurs rather extensively in eastern North America, precise data concerning its abundance and distribution have not been available. In view of rapidly expanding white-tailed deer populations throughout this section of North America and the proven pathogenicity of P. tenuis to other animals which come into contact with deer, it is essential that more information be obtained on its distribution. This article presents results of an extensive survey to determine the distribution of meningeal worm among white-tailed deer of the southeastern United States. MATERIALS AND METHODS From 1960 through early 1969 heads of 2,409 white-tailed deer were examined for P. tenuis. Animals originated from 137 counties in 13 southeastern states and St. Croix of the U. S. Virgin Islands (Fig. 1). Most deer heads were from animals killed by hunters during annual harvests in each state but some were obtained from deer dying of natural causes or collected for research purposes. Approximately two-thirds of the deer were females. Since hunters were reluctant to donate heads of mature bucks, does and immature bucks were most prevalent in the samples. Heads from hunter-killed animals were frozen prior to examination, while others were examined within 12 hr following death. After thawing, frozen and fresh heads were examined similarly. For individual examination, the head was skinned and freed of extraneous tissue. Horizontal cuts were made immediately posterior to the eyes and at the external occipital protuberance, with care taken not to damage the meninges. Frontal bones were opened along the sagittal crest, and bones lifted with a screwdriver. Bits of bone were removed with needle-nosed pliers until the brain with intact meninges was exposed. The olfactory bulb was grasped with a large pair of forceps, and tissue severed adjacent to the cribriform plate.