Beetles of the Family Scarabaeidae as Intermediate Hosts for Spirocerca lupi

Abstract

Varying numbers of adult dung beetles (family Scarabaeidae) were repeatedly exposed to large numbers of eggs of Spirocerca lupi in the laboratory. Third-stage larvae were recovered from individuals of six of nine species exposed for periods of 24 to 42 days. The number of larvae varied from 1 to 143. Geotrupes blackburnii appeared to be the best intermediate host of the beetles studied. This apparently is the first reported instance of the experimental infection of adult dung beetles by the feeding of eggs of Spirocerca lupi. The identification of the larvae was confirmed by feeding larvae to a dog which had no opportunity for previous exposure. Twelve worms were recovered from the wall of the aorta following the feeding of 18 larvae. The elucidation of the complex host-parasite relationships of Spirocerca lupi (Rudolphi, 1809) has become a matter of much greater importance as the result of the incrimination of the parasite as an inciting cause of esophageal sarcoma in the dog (Seibold et al., 1955; Ribelin and Bailey, 1958). Present knowledge on the association of Spirocerca and the malignant neoplasm; geographic distribution, prevalence, and epidemiology of the infection; and certain aspects of the host-parasite relationships have been reviewed by Bailey (1963). The primary objective of the first phase of this investigation was to determine what intermediate hosts could be infected in the laboratory to provide infective Spirocerca larvae for use in other phases of the project. Repeated attempts by one of us (W. S. B.) to infect the American and German cockroaches (Periplaneta americana and Blatta germanica) Received for publication 26 December 1962. * This investigation was supported in part by research grant C-6164 from the National Cancer Institute, National Institutes of Health. Approved by the Publications Committee, School of Veterinary Medicine, as paper number 921. The authors are indebted to Mrs. MayBelle Chitwood, Beltsville Parasitology Laboratory, USDA, for assistance in the identification of the spirurid larvae and to Mr. O. L. Cartwright, United States National Museum, for the identification of the beetles. were unsuccessful in preliminary studies conducted 1958 to 1960. Consequently, attention was directed to dung beetles since infective Spirocerca larvae had been found in several species of scarabaeid beetles collected in endemic areas. Seurat (1916) found the larvae in the following beetles in Algiers where the infection was very common in the dog: Scarabaeus (Ateuchus) sacer L., S. variolosus Fabr., Akis goryi Guer., Geotrupes douei Gory, Copris hispana L., and Gymnopleurus sturmi. Faust (1928) reported that Canthon was an intermediate host in China, but Theodorides (1952) has suggested that the beetles must have been Paragymnopleurus since Canthon had been found only in the American continents. Ono (1929, 1933), working in Manchuria, found infective Spirocerca larvae in the dragon fly Anax parthenope and in three species of dung beetles: Gymnopleurus sinnatus, Gymnopleurus mopsus, and Scarabaeus sacer var. peregrinus. The purpose of this paper is to report the results of the preliminary studies on the ability of adult beetles of different species of Scarabaeidae to serve as intermediate hosts for Spirocerca and the confirmation of the larval identification by infection of the definitive host. The results of other phases of the investigation will be published in detail in later