Theileriasis in Texas White-Tailed Deer

Theileria sp. was found in 57 percent of 1,630 white-tailed deer (Odocoileus virginianus) killed in Texas. Fourteen affected deer which were necropsied had small involuted spleens, anemia, and varying degrees of lymphocytic depletion. Five splenectomized and five nonsplenectomized fawns were inoculated with blood from a parasitized deer. One fawn died. Surviving splenectomized deer did not regain preinoculation erythrocyte values. No signs of infection were seen in the nonsplenectomized deer. Some fifty million dollars are spent annually on deer hunting by hunters in Texas. Ranchers receive income from the deer harvest on numerous land areas. Deaths of deer, adversely affecting the rural economy, have occurred periodically in the Edwards Plateau area of Texas (Taylor 1947, Taylor and Hahn 1947, Marburger and Thomas 1965, Teer et al. 1965). An estimated 20,000-31,000 deer died in the Central Mineral Region of Texas, during JanuaryAugust, 1962 (Marburger and Thomas 1965:706). The actual causes of death were not determined at the time but diseases may have contributed to those losses. Anything which may contribute to decreased deer production is of major importance in this state. Several species of Theileria transmitted by a variety of ticks produce disease in both domestic and wild animals in Africa and the Middle East. Theileria parva is the cause of East Coast Fever, a devastating disease of cattle. Theileria species are known to occur in axis (Axis axis), fallow (Dama dama), and sika (Cervus hippon) deer in countries other than the United States. These animals apparently carry these parasites without clinical signs (Neitz 1957). Rarely have similar organisms been observed in ruminants in the United States. Spindler et al. (1958) reported a Babesialike organism in the erythrocytes of a whitetailed deer captured near Silver City, New Mexico, in 1957. Theileria infection in white-tailed deer in Missouri was reported by Schaeffler in 1961. Kreier et al. described Theileria in deer in 1962. Theileriasis was described by Schaeffler (1962) as a hemolytic hemoprotozoan infection which resulted in splenomegaly, multiple hemorrhages, and anemia. Seven deer were experimentally infected. The organism which Schaeffler reported to be highly pathogenic to deer was classified as a new species, Theileria cervi (Schaeffler 1962). Theileria in Texas white-tailed deer was first recognized by Dr. T. E. Franklin in a blood film obtained from the Rob and Bessie Welder Wildlife Foundation, Sinton, Texas, in 1962. His findings were confirmed by Dr. N. Levine at the University of Illinois. Other studies were not undertaken until the present investigation was initiated in 1964. Numerous anemic and emaciated deer were observed throughout central Texas during the summer of 1965. Examination 455 1A contribution of a cooperative project between the Texas Parks and Wildlife Department and the Department of Veterinary Pathology, College of Veterinary Medicine and the Texas Agricultural Experiment Station, Texas AM supported by Texas Pittman-Robertson Project W-93-R. 2 Present address: U. S. Forest Service, Forest Sciences Laboratory, Northeastern Forest Experiment Station, Morgantown, West Virginia. This content downloaded from 157.55.39.117 on Fri, 15 Jul 2016 06:25:45 UTC All use subject to http://about.jstor.org/terms 456 Journal of Wildlife Management, Vol. 31, No. 3, July 1967 Fig. 1. Theileria in deer erythrocytes. 100X, Giemsa’s stain. of blood smears from these anima!s suggested a high incidence of infection by Theileria sp. The following studies were initiated to determine the importance of this disease to the management and health of Texas white-tailed deer. MATERIALS AND METHODS A white-tailed deer approximately 2 months old was received at the Department of Pathology, Texas A&M University, from Burnet, Texas, in the fall of 1964. This fawn was weak and anemic and unable to stand. No other clinical signs were observed. Many pleomorphic organisms were present in the erythrocytes (Fig. 1). The organisms resembled those reported by Schaeffler as Theileria cervi. The fawn had several exacerbations of anemia but remained alert and would eat and drink eagerly if its head was supported until it died 8 days later. Blood collected from this fawn was inoculated into a nonsplenectomized adult deer. Fourteen days postinoculation, the parasites were observed in the erythrocytes of the adult deer. The parasitemia did not exceed 1 percent until the animal was splenectomized. Blood from this animal was used as inoculum for later experimental inoculations. Field Necropsies Fourteen clinically affected deer from the Edwards Plateau were examined and necropsied. Blood films were made from all deer and attempts were made to culture bacteria when gross lesions suggested bacterial disease. Bacterial cultures were negative. These animals were collected during the late summer and early fall of 1964 and 1965, a time when range conditions were generally poor. Blood Film Survey Approximately % of 254 counties in Texas support populations of deer. Samples of blood were obtained from the deer in each county that supported 1,000 or more deer. The aid of 30 biologists and 25 technicians was enlisted. Each man assigned in the sampling program was visited by a member of the disease research team, assigned specific collecting areas, and instructed in the proper procedures for collecting blood samples and making blood film preparations. In Texas, hunting rights to particular pastures within ranches are leased to hunters, some of whom are provided lodging in “camp houses” equipped with refrigerators.