Infected Raccoons Research Articles

Epizootiologic Studies on Filarioids of the Raccoon

Filarioid worms (Dirofilaria immitis, D. tenuis, Dipetalonema procyonis, and D. Ilewellyni) were discovered in raccoons (Procyon lotor) in Maryland. Raccoons were trapped in lowland, upland, and agricultural-residential areas, which were further classified as stream borders, poorly drained, and well drained. Data on incidence of D. Ilewellyni were analyzed on basis of host distribution within these areas to indicate type of habitat in which one might seek the vector. It was concluded that exposure takes place in the spring of the year. The arthropod found associated most often with the raccoon in spring was Ixodes texanus. Larvae of this tick which were fed on infected raccoons presented no evi- dence of development of the microfilariae. Feeding experiments were also conducted with mosquitoes: Aedes aegypti, A. canadensis, A. sollicitans, A. triseriatus, A. vexans, Culex pipiens, Anopheles punctipen- nis, and A. quadrimaculatus. Although microfilariae remained alive and active in the gut contents of all these mosquitoes for 2 days, only in Aedes aegypti did they enter the hemocele, but no developmental changes were noted and all microfilariae were dead by the eighth day. Although the intermediate host of D. llewellyni was not determined, evaluation of the accumulated data provides criteria for seeking the vector. It appeared unlikely that exposure of the raccoons took place in the den or that the filarioids were transmitted by an ectoparasite commonly found in raccoon dens. The data suggest that the vector is available only early in spring, although there are infected raccoons throughout the year. Prevalence in juveniles was 21 percent; in subadults, 64 percent; in adults, 87 percent.

Life History of Heterobilharzia americana Price 1929, a Schistosome of the Raccoon and Other Mammals in Southeastern United States

The life cycle of Heterobilharzia americana, a bloodfluke of the raccoon, nutria, dog, and rabbit in southern Louisiana, was completed in the laboratory. The cercariae were found in naturally infected Lymnaea cubensis at Pass a Loutre in the Mississippi River delta. Although infected Pseudosuccinea columella was not found in nature, in laboratory experiments it was as susceptible as L. cubensis. Cercariae were liberated from the infected snails about 4 weeks after exposure. The eggs, oval with a smooth shell, contain miracidia which resemble those of other known species of mammalian schistosomes, except that the number of ciliated epidermal plates is 22 instead of 21. The furcocercous, apharyngeate cercaria has six pairs of flame cells and five pairs of penetration glands; it has eyespots and furcal fin-folds. It swims towards the light close to the water surface. In mice the migrating schistosomula caused pulmonary hemorrhages of two sizes, the earlier ones being the larger. The developing worms became sexually mature in the liver on the 40th day, but eggs containing mature miracidia were not observed until the 68th day following infection. Two species of schistosomes, Schistosomatium douthitti (Cort 1914) and Heterobilharzia americana Price 1929, are known to occur in mammals in the United States. The life cycle stages of S. douthitti have been studied by H. Price (1931) and others (Kagan et al., 1954). The original description of H. americana was based on two male specimens from a bobcat (Lynx rufus floridanus) taken in Florida. Later, Price (1943) described the female and redescribed the male from specimens found in a raccoon (Procyon lotor) in Texas. More recently this species was reported in raccoons in North Carolina (Miller and Harkema, 1960) and Florida (W. H. Leigh, pers. comm., 1960). In the coastal swamplands of Louisiana and the mud flats of the Mississippi River delta, it has been found in the raccoon, nutria (Myocastor coypus), and dog (Malek et al., 1961). Brief notes on the life cycle were published by Lee Received for publication 9 July 1962. *A portion from a thesis submitted to the Graduate School of Tulane University in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The study was supported in part by research grants 2E-2 and E-2898 from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Public Health Service. t Present address: Department of Parasitology, Faculty of Medicine, University of Singapore, Singapore. in 1960 and by Greene in 1962. In the present repor the stages in the life cycle are described more fully. MATERIALS AND METHODS Eggs were obtained by gravity sedimentation in 0.85% saline from feces of infected raccoons captured locally and maintained in the laboratory. The miracidia were hatched and concentrated from washed feces in Erlenmeyer flasks filled to the brim with aged tap water, the miracidia being pipetted from the water surface. The side-armflask method described by McMullen and Beaver (1945) for concentrating miracidia of bird schistosomes was found unsuitable for H. americana. Lymnaea cubensis (Pfeiffer) and Pseudosuccinea columella (Say), collected in the vicinity of New Orleans, were used as laboratory intermediate hosts. As the former species adapted poorly to laboratory conditions, snails from field collections, negative on repeated checking for cercariae, were used for experimental infections. P. columella used in the experiments were laboratory bred and maintained in aerated aquaria. L. cubensis was maintained in aquaterraria. Both species were fed fresh lettuce. Some snails were exposed en masse by placing them together with many miracidia in a stender dish 50 mm in diameter. Others were exposed to five miracidia each in a shell vial, 45 mm high and 15 mm in diameter, containing a small quantity of water. To prevent the snails' escape from the water, a piece of nylon net, about 4 cm square, was pushed down to the level of the water surface. The snails were examined for cercariae daily beginning at 20 days after exposure and continuing for at least 3 weeks. Swiss white mice were infected by placing them

Life History, Morphology and Taxonomy of Atriotaenia (Ershovia) procyonis (Cestoda: Linstowiidae), a Parasite of the Raccoon

While investigating the intestinal parasites of vertebrates from Franklin County, Ohio, a high level of tapeworm infection was encountered in the raccoon (Procyon lotor lotor). This tapeworm proved to be one of the linstowids originally described by Chandler (1942) as Oochoristica procyonis. Since these specimens seemed to disagree in some respects with the species description, an extensive study of the morphology was undertaken in order to define more completely the species limits. The clarification of the characteristics of this cestode brought up the problem of its proper taxonomic position. As a result of investigation into this problem, the author decided that this species should be referred to as Atriotaenia (Ershovia) procyonis (Chandler, 1942) Spassky, 1951. The reasons are presented in the discussion. Further investigation revealed that the life history was not known. With ample material readily available, the life history of this cestode was completed in the laboratory. Extensive trapping activities led to a survey of the incidence in feral raccoons. MATERIALS AND METHODS Cestodes were obtained by trapping raccoons with especially constructed live traps. Trapped animals were housed in outdoor pens and served as a source of gravid proglottids and eggs used in feeding experiments. Five suckling, 2-week-old raccoons were obtained for future use in life history experiments. These were subsequently weaned and maintained on a diet of fresh ground beef, dog chow checkers, and water. These animals were kept in indoor cages, well isolated from the adult, infected raccoons. Fecal examinations were made periodically to determine whether the animals were still uninfected. They all remained so until used for feeding experiments. Cultures of the flour beetle Tribolium castaneum (Hbst.), used as an experimental intermediate host, were maintained in large mason jars and fed on a mixture of wheat flour and brewers yeast. These cultures were kept at room temperatures which varied from 22? to 29? C. Gravid proglottids used in feeding experiments were obtained either from the feces of infected raccoons or from living worms recovered from sacrificed animals. Two proglottids were placed on a small piece of filter paper, moistened, and teased apart with two small needles. In each feeding experiment, 10 beetles, starved for the previous 48 hours, were allowed to feed on the proglottids for 24 hours. These beetles were then returned to culture jars and left undisturbed until they were examined for stages of cysticercoid development. When dissecting beetles, the body (after removal of head, elytra, wings and legs) was placed in a drop of insect saline solution, teased apart, and the larval stages removed. During these dissections, care was taken to keep the entire digestive tract of the insect intact so that examination for early larval stages penetrating the gut could be carried out. Cysticercoids recovered from beetles, when fed to uninfected raccoons, were embedded in small pieces of ground beef about the size of the human thumb. Daily fecal examinations for gravid proglottids were then carried out. Some of the raccoons infected in this manner were sacrificed, and both immature and adult worms were removed from the small intestine.

Studies on the mortality of mosquitoes infected with Dirofilaria tenuis Chandler 1942

Summary An attempt was made to study periodicity of D. tenuis through mosquito mortality, and determine the effect of the larvae of this filariid on mosquito mortality. Dirofilaria tenuis appears to be nocturnal in periodicity with the microfilariae being at their maximum in the peripheral blood at about midnight. Mosquitoes fed on a lightly infected raccoon reached a peak mortality on the third day. Mosquitoes fed on a heavily infected raccoon suffer greatest mortality on the second day, followed by a high ensuing mortality accented on the eighth and ninth day. As the number of microfilariae ingested by the mosquito increases, it appears that the time it takes the microfilariae to enter the tubules decreases. Generally mosquito mortality increased as the number of microfilariae ingested increased.