Showing papers in "Journal of Parasitology in 1972"

The Structure of Nematodes

Abstract: The egg the exoskeleton growth and moulting the epidermis musculature the nervous system the pseudocoelom the secretory-excretory system the digestive system the reproductive system nematode pathology.

Plant Parasitic Nematodes

Abstract: • Nematodes cannot move large distances unaided. However, they can be spread by surface water, and in soil adhering to vehicles and farm machinery. In un-infested areas, good hygiene should be adopted. They can also be spread in dust when they are in a dehydrated state over summer. Figure 1: A Pratylenchus thornei adult female viewed under the microscope. The nematode is approximately 0.65 mm long. Tips and Tactics

Demodex folliculorum (Simon) and D. brevis akbulatova of man: redescription and reevaluation.

Abstract: Demodex folliculorum and D. brevis are redescribed using statistical methods for meristic data and standard generic morphological criteria for all stages. Such data show that these are distinct species. Histological studies indicate that each of these utilizes different niches: D. folliculorum the hair follicle, D. brevis the sebaceous glands. Both species have life cycles consisting of ova, larvae, protonymphs, nymphs, and adults. Population counts of these stages revealed ratios of approximately 3.5:1.5:1.0:1.6:14.6 for D. folliculorum and 8.5:2.6:1.0:3.2:34.7 for D. brevis. The sex ratios (male: female) were 1:4.5 for the former and 1:3.4 for the latter. It is suggested that all host-parasite data obtained since Simon (1842) should be reworked in view of the fact that these two species are found on tle same host species, Homo sapiens, and even the same host individual.

Craig and Faust's Clinical Parasitology

Abstract: Craig and Faust's Clinical parasitology , Craig and Faust's Clinical parasitology , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Effects of different conditions on duration of infectivity of Toxoplasma gondii oocysts.

Abstract: Washed oocysts and cat feces containing oocysts were exposed to various environmental conditions in the laboratory and outdoors. Infectivity was tested every 14 days by injecting samples through tubes into stomachs of mice. The brains of the mice were examined (in wet films) 30 to 60 days later for T. gondii cysts. In the laboratory oocysts retained infectivity from 30 days (in uncovered dishes at 37 C) to 410 days or longer in covered and uncovered dishes at 4 C. Outdoors, infectivity was retained from 46 days (uncovered, exposed to direct sunlight, mean air temperature 20 C) to 410 days or longer (covered in shade, mean air temperature 19.5 C). Since cats normally bury their feces, the results suggest that T. gondii oocysts may remain infective for a year in warm climates, and longer in cool climates or in air-conditioned buildings. On the basis of 1969 discoveries, a number of authors in 1970 described the oocyst of Toxoplasma gondii which is passed for a brief period in the feces of experimentally infected cats. The literature, including recent discoveries, is reviewed by Dubey et al. (1970) and Hutchison et al. (1971). The oocyst of T. gondii seems morphologically similar but not identical to that of Isospora bigemina var. cati (Railliet and Lucet, 1891), called Isospora cati by Dubey et al. (1970). Toxoplasma is not considered a synonym of Isospora as Overdulve (1970) proposed because its life cycle is different. The coccidian oocyst is adapted to resist adverse conditions of the environment outside the host. As one phase of a complex study, we attempted to determine how long Toxoplasma gondii oocysts would remain infective under various environmental conditions, indoors and outdoors. MATERIALS AND METHODS Six 4-week-old kittens, born in the laboratory and negative for Toxoplasma by Sabin-Feldman dye test and fecal examination, were experimentally infected with the Beverley strain of T. gondii. This strain had been maintained in our laboratory through repeated passages from mouse to mouse Received for publication 17 March 1972. * From part of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Animal Parasitology, Texas AM monthly averages of daily maxima and minima were 5.5 to 35.5, monthly means were 12 to 29 C, and the mean for the year was 19.5 C. In each of the tests with 3 types of preparations under 5 sets of conditions, covered petri dishes we e paired with petri dishes having no cover. In each covered petri dish, the preparation was further protected by a pad of 10 layers of gauze whic was kept moist by rewetting every 3 to 4 days, or as often as needed to prevent complete drying. Covering and lack of covering in each of the 15 tests raised the total number of "treatments"

Spirocerca lupi: a continuing inquiry.

Abstract: Studies with Spirocerca lupi from 1951 through 1970 are reviewed. It is suggested that the primary reason for the lower prevalence of the parasite in dogs in the southeastern United States since 1963 is the reduction of dung beetle populations by insecticides. With its circuitous migration, Spirocerca provides an excellent model for studies of site-finding behavior. The developing worms cause extensive damage to the aorta, and death from hemorrhage may result as early as 12 days after infection when large numbers are present. Young adults may reach the esophagus by the 76th day, but this part of the migration occurs more commonly 3 to 4 months after infection. The fibroblasts in the reactive granuloma which develops around Spirocerca in the wall of the esophagus may be quite metaplastic and sometimes appear to be transitional between granuloma and sarcoma. A total of 58 cases of Spirocerca-associated sarcomas have been studied during the 20-year period. There is strong evidence of a causal relationship between Spirocerca and these sarcomas. The occurrence of the Spirocerca-associated sarcomas during the past 20 3-ears suggests that another oncogenic stimulus may be involved in the transformation of granuloma to sarcoma, possibly an agent in the environment to which there has been an increased intensity of exposure during this period. The intricacy and efficiency of form, function, and behavior of parasites evoke an intense esthetic feeling in the serious student of parasitology. More than a quarter century of activity in veterinary parasitology has provided me the opportunity to work with many beautiful and fascinating parasites, but none has been more striking and exciting than Spirocerca lupi (Rudolphi, 1809), the esophageal worm of the dog. Therefore, it is only natural that for this occasion I have chosen to review our work with this parasite, with the hope that I can convey to you something of the excitement which we have experienced in the unfolding of what I have come to think of as the "Spirocerca story." While most of my time will be devoted to reviewing the results of studies by our group and others, I particularly want to call attention to questions which remain unanswered and to opportunities for further studies of the fascinating host-parasite relationships in this model

Fine structure of the reproductive system of a frog lung fluke. 3. The spermatozoon and its differentiation.

Abstract: Monopartite sperm of the frog lung fluke, Haematoloechus medioplexus, arise by fusion of three juxtaposed cytoplasmic processes that grow out from a spermatid. Paired centrioles serve as nucleation sites for the axial units that grow into the 2 lateral processes, while the nucleus migrates into the central process. Such basal bodies, and attached rootlets, may aid in stabilizing the threadlike processes so that fusion can efficiently occur; basal bodies or rootlets are not seen in a mature sperm. The sperm is about 400 uL long and less than 1 u in diameter; the shaft resists bending, except for a terminal portion (25 to 50 Au) that undulates rapidly in living material. Typical transverse sections through the middle piece, which represents most of the shaft, show paired axial units, one on each side, a central mitochondrion, and two sets of cortical microtubules, some of which may be attached to the plasma membrane. Gametogenesis in the frog lung fluke, Haematoloechus medioplexus, has been studied in some detail at the light microscopic level (Burton, 1960), and the electron microscope has provided some information on fertilization in this trematode (Burton, 1967a). Electron microscopic studies of the structure and differentiation of trematode spermatozoa are few in number and generally lacking in detail (Shapiro et al., 1961; Gresson and Perry, 1961; Hershenov et al., 1966; Tulloch and Hershenov, 1967; Sato et al., 1967), and this is also the case as regards such studies of spermatozoa of cestodes (Gresson, 1962; Rosario, 1964; Lumsden, 1965; von Bonsdorff and Telkka, 1965; Swiderski, 1968; Morseth, 1969). One factor contributing to the difficulty in studying differentiation of trematode spermatozoa is the complexity of the process. A single spermatogonial cell ultimately gives rise to a rosette of 32 spermatids. As a result of incomplete cytokinesis at each division, the 32 cells remain connected by cytoplasmic bridges at their basal ends. The spermatids undergo a complex process of differentiation typically inReceived for publication 27 May 1971. * Supported by U. S. Public Health Service Grant AI-06448 and a Career Development Award (1-K3-GM-8620) from the Institute of General Medical Sciences. volving the formation and fusion of three cytoplasmic filaments several hundred microns in length (Burton, 1960; Hendelberg, 1962). Testes are filled with thousands of these filaments in various stages of differentiation, as well as germinal and spermatogonial cells, spermatocytes, and early spermatids. An ultrathin section (500 to 900 A), as examined in the electron microscope, will contain sections at various angles through hundreds of the aforementioned elements, and it is difficult and time-consuming to reconstruct each step of the complex process. The present study will set forth in some detail the sequence of structural changes involved in the differentiation of the spermatid of H. medioplexus into a mature threadlike sperma-

Scanning electron microscopy of integumental surface of schistosoma mansoni.

Abstract: The integumental surface of adult S. mansoni was studied by scanning electron microscopy at 50 to 10,000 magnifications. Many spines of variable size cover the inner surface of the oral sucker of the male and extend to the pharyngeal opening. Fewer and smaller globular spines cover the inner surface of the ventral sucker. Bosses of variable size with variable numbers (50 to 250) of spines occur on the greater part of the body surface but not in the gynecophoral canal. The posterior end of the male is devoid of bosses, but spines are freely distributed over the surface. The dorsal body surface is also characterized by papillalike integumental elevations of irregular size, shape, and distribution. These may be associated with clumps of small spines, and in some instances possess a cavity or crater. Larger spines protrude from some of the cavities. The female is free of bosses, but there is a heavy covering of anteriorly directed spines on the posterior part of the body. The structure of the integument of the schistosomes, particularly Schistosoma mansoni, has been investigated employing ultrathin sections suitable for examination in transmission electron microscopy (TEM) (Senft et al., 1961; Morris and Threadgold, 1968; Silk et al., 1969; Smith et al., 1969). These studies have indicated that the integument is a syncytium made up of a surface layer recognized as a cytoplasmic sheath or matrix, connected by cellular extensions to cell bodies (nuclei) buried in the parenchyma. Additionally, there are ultrastructural objects including mitochondria, cuticular channels, vesicles, and discoid granules. Golgi bodies, endoplasmic reticulum, and ribosomes are absent. Contrasted with the abundance of information dealing with subsurface integument, there is a paucity of observations, at comparable magnifications, made on the surface of the schistosome. This is understandable since there was no readily available means of examining the ultrastructure of surfaces other than by utilizing the incalculably small amount of information which could be derived Received for publication 23 March 1972. *Investigation supported by the United StatesJapan Cooperative Medical Science Program administered by the NIAID, NIH, Department of Health, Education, and Welfare, under Grant No. 5 R 22 AI-08207. t Department of Pathology and Laboratories, Nassau County Medical Center, East Meadow, New York 11554. t Division of Microbiology and Infectious Diseases, Southwest Foundation for Research and Education, San Antonio, Texas 78228. from nonsequential ultrathin TEM sections which pass through the surface. The roughness of the surface of the male S. mansoni and, conversely, the smoothness of the female first was recognized employing light microscopy. By this means it was possible to identify many elevated areas which were designated as tubercles covered with hairs. With the development of TEM came a change in nomenclature, i.e., the tubercles became bosses and the hairs became spines. Additionally, TEM occasionally revealed sections through such surface structures as openings of canaliculi and pores of various types. The present report is concerned with the surface microtopography of the adult S. mansoni as visualized with the scanning electron microcope (SEM). The SEM, with its great depth of field, i.e., at least 200 times that of a light microscope, and its resolution of 200 A or better, provides a means for determining the fine topography of body surfaces. Furthermore, an opportunity is afforded to correlate external features with those internal structures revealed by TEM. Other studies dealing with the ultrastructure of the schistosome surface are in progress and involve the use of specimens of known ages from 1 day to 27 weeks, i.e., from the schistosomule to the mature adults. By this means the maturation of surface structures may be correlated with time. To date, the SEM has been used by Hockley (1968), Johnson and Moriearty (1969), and Robson and Erasmus (1970) to study the surface features of the cercariae of S. mansoni, and by

The influence of human skin lipids on the cercarial penetration responses of Schistosoma haematobium and Schistosoma mansoni.

Abstract: The behavior of cercariae of Schistosoma haematobium and S. mansoni was studied by observation on agar plates. It was found that the addition of human skin lipid to the agar altered the behavior of the cercariae, inducing them to attempt penetration of the agar. Cercariae were not stimulated by purified skin sterols or cholesterol but responded to the free fatty acid fractions of lipid collected from human forearms. Further separation showed the substance which triggered response in the cercariae to be the unsaturated fraction of free fatty acids. Pure free fatty acids also elicited

Revision of the class Archiacanthocephala Meyer, 1931 (phylum Acanthocephala), with emphasis on Oligacanthorhynchidae Southwell et Macfie, 1925

Abstract: Class Archiacanthocephala is modified to include Moniliformida ord. n. All genera in Oligacanthorhynchidae were studied and several changes in classification of the family are made. Nephridiacanthus Meyer, 1931; Hamanniella Travassos, 1915; Travassosia Meyer, 1931; and Echinopardalis Travassos, 1918, are considered to be junior synonyms of Oligacanthorhynchus Travassos, 1915. Prosthenorchis elegans (Diesing, 1851) Travassos, 1915, P. lemuri Machado, 1950, and P. fraterna (Baer, 1959) comb. n. are retained in Prosthenorchis Travassos, 1915: all other species previously assigned to this genus are distributed among Pachysentis Meyer, 1931, Oncicola Travassos, 1916, and Neoncicola gen. n. The new genus is proposed for 7 species similar to Oncicola but with 30 rather than 36 proboscis hooks. Keys are provided for the orders in class Archiacanthocephala, and the 8 genera in Oligacanthorhynchidae accepted as valid. Each genus is redefined and a list of species in each is provided. No family in the Acanthocephala has a more confused literature than Oligacanthorhynchidae Southwell et Macfie, 1925. This condition has resulted from a number of causes: vague descriptions of species and uncertain definitions of genera by early authors, incorrect interpretations of morphology by more recent authors, and the homogeneity of the species themselves. Consequently it is almost impossible to identify an oligacanthorhynchid to genus, even using the keys of Petrochenko (1958), Golvan (1962), and Yamaguti (1963). During the past 10 years I have accumulated a large series of specimens representing all of the genera in the family. Several collectors have contributed specimens for study, most notably Dr. John F. Schacher who generously gave me a large collection which he assembled in Lebanon from 1961 to 1963. Study of these collections has made it possible to revise the family on sound morphological lines, without resorting to the separation of genera on the basis of definitive hosts, as has been historically accepted (e.g., Oligacanthorhynchus from birds, Hamanniella from opossums and edentates, etc.). Despite my efforts, and the efforts of others, it remains impossible to identify most juvenile forms to genus. The monotonous similarity of proboscis armature between most genera and species forces the systematist to rely on adult Received for publication 15 July 1971. characters, such as location of testes and shape of trunk, features that are unresolved in juveniles. The practice of describing juveniles as new species within a given genus in this family should be avoided, for it only continues to confound an already confused classification. The lists of species following the diagnoses of g nera in this paper have, for the most part, been uncritically drawn from the literature with little consideration of possible synonyms within each list. However, each species poorly known or known from juveniles only appears with a question mark before it. My interest here has been to resolve problems at the levels of genus and above; this should simplify the task for others who wish to further consider the species in each genus. In addition to studying whole mounts, stained with Semichon's carmine, I employed microdissections and serial sectioning to resolve certain problems, such as structure and insertions of the muscles of the proboscis receptacles. The typically thick walls of the trunk and the sheer size of many species make studies of whole mounts less practical than with most other families of Acanthocephala. The practice of describing proboscis armature as forming spiral rows of hooks has been avoided in this paper. The difficulties of counting hooks by this technique outweigh any advantage of ease of description. Instead, I consider the hooks to be arranged in short, approximately longitudinal rows.

Observations on hybridization of three species of North American Dermacentor ticks.

Abstract: Female Dermacentor andersoni Stiles confined on the host with male D. variabilis (Say) later produced infertile eggs, whereas the reciprocal cross sometimes yielded progeny of both sexes. Meiotic chromosome pairing, karyokinesis, and cytokinesis in some of these hybrid males suggest various degrees of chromosome homology. Certain morphological characters of the hybrids appeared intermediate while others resembled one parent species more than the other. Hybridization between D. andersoni X D. occidentalis Marx produced no progeny when male D. andersoni mated female D. occidentalis, but the reciprocal cross yielded offspring. Dermacentor variabilis is common east of the Rocky Mountains in the United States, in parts of California, Oregon, Idaho, Mexico, and Canada. D. occidentalis is prevalent from central Oregon to lower California. D. andersoni occurs in the Rocky Mountain States, western North Dakota, South Dakota, and Nebraska, south to New Mexico, California, and parts of Canada (British Columbia, Alberta, and Saskatchewan). The ranges of these taxa overlap in certain areas, yet there are some differences in apparent preferences for bioclimatic zones (Rapp, 1960; Wilkinson, 1967). Although peak activity of adults of one species might be out of phase with another (i.e., peak of D. variabilis activity is often a month later than that of D. andersoni), both species might simultaneously parasitize the more widely traveling hosts, such as ungulates and carnivores. On the host, there may be differences in preferred site of attachment as observed with D. andersoni and D. albipictus (Packard) on deer (Wilkinson, 1970), but Dermacentor males actively seek out receptive females (Berger et al., 1971) and could encounter individuals of both species. Thus there is some practical relevance to studReceived for publication 31 August 1971. * Acari: Ixodidae. t Supported in part by Public Health Service Research Grants AI-06169 and AI-09556 from the NIAID (principal investigator, James H. Oliver, Jr.). t Callaway Professor, Department of Biology, Georgia Southern College, Statesboro, Georgia 30458. ? Research Scientist, Research Station, Canada Department of Agriculture, Lethbridge, Alberta. II Sanitarian Director, Retired, U. S. Public Health Service, Rocky Mountain Laboratory, Hamilton, Montana 59840. ies of the outcome of crosses among these important disease vectors. MATERIALS AND METHODS Ticks were fed on rabbits, guinea pigs, and sheep by confining them in capsules on clipped areas of the hosts or in ear bags on rabbits (Bailey, 1960). Details of geographic origin of the species and particulars of each experiment are presented with the results of each experiment. Each of us conducted experiments unaware of similar experiments by the others. Experiments were conducted at Hamilton, Montana; Lawrence, Kansas; Berkeley, California; and Kamloops, British Columbia, and span a period from 1954 to the present. Preparation of tissues for cytological studies consisted of removing males from hosts 3, 4, 5, and 6 days after initial attachment and placing them in modified Carnoy's fixative for approximately 24 hr, before storing in a refrigerator. Subsequently, testes were removed, stained with acetocarmine, and typical squash preparations made.

Trypsin inactivation by intact Hymenolepis diminuta.

Abstract: Using azoalbumin as a substrate, it was demonstrated that intact Hymenolepis diminuta inactivate trypsin when incubated with this enzyme. At a given enzyme concentration ([E]), the per cent inactivation (%I) was relatively constant as the substrate concentration ([S]) was varied. However, at a given [S], the %I increased as the [E] decreased. It was also demonstrated that inactivation was dependent upon the time worms were exposed to the enzyme, the total worm weight present in the assay, and the pH of the assay medium. The %I was not related to worm surface area, and was unaffected by polyions and calcium ions in the incubation medium. These results are discussed in relation to the possible mechanism and physiological significance of this phenomenon. The mucosal surface of the mammalian intestine and the outer surface of the syncytial epidermis of the cestode, Hymenolepis diminuta, contain intrinsic membrane-bound enzymes (Crane, 1962; Newey et al., 1963; Arme and Read, 1970; Dike and Read, 1971a). Both surfaces are reported to adsorb enzymes of pancreatic origin (Ugolev, 1965; DeLaey, 1966a; Goldberg et al., 1968, 1969; Read, 1972). According to DeLaey (1966b), adsorption of amylase involves interaction with the mucosal glycocalyx and is readily reversible (Jesuitova et al., 1964). Amylase adsorption to the surface of H. diminuta is also reversible and is partially blocked by polyions (Read, 1972). However, the adsorption of proteolytic enzymes to isolated mucosal cells or subcellular particles is not readily reversible (Goldberg et al., 1968, 1969). According to Ugolev (1965), the adsorption of amylase on the mammalian mucosa results in an increase in enzyme activity. However, doubt has been cast on Ugolev's interpretation with the demonstration that the mammalian mucosa has intrinsic membrane-bound amylases (McMichael and Dahlqvist, 1968; Alpers and Solin, 1970). On the other hand, while Hymenolepis does not exhibit intrinsic amylase or disaccharidase activity, adsorption of pancreatic amylase to the worm surface results in an increase in amylolytic activity (Taylor and Thomas, 1968; Read, 1972). Adsorption of trypsin and chymotrypsin to isolated human Received for publication 24 February 1972. * This study was supported by a grant (AI-01384) from the NIH, U. S. Public Health Service. t U. S. Public Health Service Postdoctoral Fellow, 1-F02-AI-45108-01. mucosal cells or subcellular particles does not ter the kinetic parameters of these enzymes (Goldberg et al., 1969). However, in the presence of intact mammalian mucosa, proteolytic enzymes of pancreatic origin are inctivated (Borgstrom et al., 1957; Goldberg et al., 1968, 1969; Pappas and Gallogly, unpublished). Reichenbach-Klinke and Reichenbach-Klinke (1970) reported that trypsin is inactivated in the presence of the tapeworm, Proteocephalus longicollis. The present investigation was concerned with the effects of the tapeworm, Hymenolepis diminuta, on pancreatic trypsin. MATERIALS AND METHODS Hymenolepis diminuta were reared in the beetle, Tenebrio molitor. Male Sprague-Dawley rats (Holtzman Co.) weighing 80 to 100 g were infected with 30 H. diminuta cysticercoids and the worms removed 11 days postinfection. Worms were rinsed in 3 changes of Krebs-Ringer solution containing 25 mM Tris(hydroxymethyl) aminomethane-maleate buffer (pH 7.2) (KRT of Read, Rothman, and Simmons, 1963), randomized into groups (usually 10 worms/group), and incubated in fresh KRT at 37 C for 15 min prior to their addition to the assay medium. The assay medium consisted of 4 ml of KRT and 1 ml of an enzyme solution (Trypsin-type XI: DCC treated. 8,000 BAEE units/mg. Sigma Chemical Co., St. Louis) maintained at 37 C in a shaking water bath. When groups of worms were to be used during assays they were removed from the previous incubation medium (KRT) and allowed to incubate in the KRT-enzyme solution for 15 min prior to the addition of substrate (this period in the KRT-enzyme solution is hereafter referred to as the preincubation period); after preincubation the worms were removed. The reaction was initiated by the addition of 1 ml of an azoalbumin (bovine origin, Sigma) solution prewarmed to 37 C, and allowed to continue for a prede-

Transmission of four Central American strains of Plasmodium vivax from monkey to man.

Abstract: Infections of 4 different Central American strains of Plasmodium vivax in the Aotus trivirgatus monkey were shown to be infectious to Anopheles freeborni and A. maculatus mosquitoes. The A. freeborni were more readily infected than were the A. maculatus with each of the strains. A comparison of the infection ratios indicated that each strain of malaria was different with regard to its mosquito infectivity. Transmission of the infection to 17 men was obtained by the bites of infected A. freeborni mosquitoes after extrinsic incubation periods of 13 to 18 days. The prepatent periods in the men ranged from 9 to 16 days with a mean of 13.8 days. The Aotus trivirgatus monkey has been shown to be potentially useful as an experimental animal in studies on the human malarias. Young et al. (1966) first reported infection of this monkey with a strain of Plasmodium vivax from Panama. Subsequent adaptation of P. falciparum and P. malariae parasites (Geiman and Meagher, 1967; Geiman and Siddiqui, 1969) has increased interest in the study of different isolates of the malaria parasites in the Aotus monkey. One area which has concerned us has been the infection of mosquitoes with malaria by feeding on these animals for subsequent transmission studies to man. Previously, we have reported the results of transmission studies using P. falciparum and P. malariae from the Aotus monkey (Contacos and Collins, 1968, 1969; Collins et al., 1968). Reported here are the results of studies with different isolates of P. vivax from Central America. MATERIALS AND METHODS The 4 strains of P. vivax used in the studies were obtained from naturally acquired infections from El Salvador (Sal-I, Sal-II), Panama (Panama), and Nicaragua (NICA), and provided to us by the staff of the Central America Malaria Research Station, NCDC, San Salvador, El Salvador. Once the strains were established in A. trivirgatus monkeys, they were maintained by serial passage of infected blood. Aotus trivirgatus monkeys, obtained commercially, had their origin in Colombia, South America. Prior serologic and microscopic examination indicated that they were free of natural malarial infection. Received for publication 21 October 1971. The Anopheles freeborni mosquitoes were the F-l strain originally isolated from Marysville, California, and maintained in the laboratory since then (Hardman, 1947). The A. maculatus mosquitoes were obtained from the Institute of Medical Research, Kuala Lumpur, Malaysia (Ow Yang et al., 1963). The techniques used for the feedings on the monkeys and on the human volunteers are those previously reported (Collins et al., 1968).

Influence of temperature on the infectivity of eggs of Echinococcus granulosus in laboratory rodents.

Abstract: A comparison was made of the susceptibilities of Mongolian jirds (Meriones unguiculatus) and CF1 mice to infection with embryos of Echinococcus granulosus administered either intraperitoneally or orally. Optimal infectivity was obtained in both hosts using a dose of 1,000 eggs by the intraperitoneal route. This procedure was subsequently used in a series of experiments on the effects of exposure to subfreezing temperatures or moist heat on the survival and infectivity of eggs of E. granulosus. Eggs were found to survive for 24 hr at -30 C with no detectable effect on infectivity. One animal became infected after receiving eggs exposed to -50 C for 24 hr. No infections developed in animals inoculated with eggs subjected to -70 C. After 5 min incubation at 55 C the infectivity was significantly reduced, and incubation for an identical period of time at higher temperatures was sufficient to inhibit cystic development completely. These findings are discussed in relation to available information on the survival of taeniid eggs exposed to extremes of temperature. The influence of exposure to low temperatures on the survival of taeniid eggs has been investigated by a number of workers both in the field and in the laboratory. Jepsen and Roth (1949) showed that some eggs of Taenia saginata retained their infectivity for cattle after 23 weeks of exposure to winter temperatures on pastures in Denmark, and Sweatman and Williams (1963) demonstrated that eggs of Echinococcus granulosus were still infective for sheep after 4 winter months on grass plots in New Zealand. Gemmell (1969) found that a small proportion of embryos of Taenia hydatigena and Taenia ovis which had been exposed to -15 C for 24 hr produced viable cysts in lambs. Resistance to the effects of freezing was also shown by Schiller (1955) who was able to infect redbacked voles with eggs of E. multilocularis maintained at -26 C for 54 days, or at -51 C for 24 hr. Few data are available on the capacity of taeniid eggs to survive elevated temperatures. Nosik (1952) found that eggs of E. granulosus in water were no longer infective for sheep after 1 hr at 50 C, or 20 sec at 100 C, and Williams (1963) showed that eggs of T. pisiformis were no longer able to infect rabbits after immersion for 5 sec in water at 100 C. Meymarian and Schwabe (1962) were unable to activate eggs of E. granulosus in vitro after exposure to moist heat at 60 C for 10 min, 70 C for 5 min, or 100 C for 1 min. Received for publication 7 January 1971. There is a need for more precise definition of the factors which influence the survival of eggs of E. granulosus (WHO Expert Committee on Hydatidosis, 1968). This information would be of immediate use in the assessment of environmental contamination under a variety of climatic conditions and in the establishment of suitable handling and sterilization procedures for laboratory work. The extrapolation of data obtained for other taeniid species to E. granulosus is hazardous, but the assessment of survival and infectivity of this parasite is problematical. Many authors have used direct observation of the movement of embryos in artificial digestive media (Meymarian, 1961; Pamell, 1965; Laws 1967, 1968). However, activation has not been shown to be an indicator of infectivity, and embryos which do not activate may still be infective for laboratory rodents (Williams and Colli, 1970). The use of oral infections in the natural hosts (sheep or swine) has been largely precluded as an indicator of infectivity due to the high cost and extended duration of such experiments, the requirement for large numbers of cestode-free animals, and the extreme variability of infections produced by a standard dose of eggs. In the present study, the infectivity of eggs of E. granulosus for laboratory rodents was established, using both the intraperitoneal and oral routes of administration. Optimal conditions for manifestation of infectivity were chosen and the influence of exposure to sub-

IgG levels and host specificity in hydatid cyst fluid.

Abstract: IgG was found in sheep hydatid fluid at concentrations ranging between 1 and 3 Aug/ml by the specific radial immunodiffusion method. The species-specific antigenic determinants of the host immunoglobulins were found in hydatid cyst fluid from 4 different species of hosts. The albumin levels and albumin/IgG ratios of cyst fluid were also determined. It is postulated that these proteins enter the parasite by diffusion from the surrounding host tissues. Host serum protein components have been demonstrated in hydatid cyst fluid and attempts made to quantify them. Codounis and Polydorides (1936) detected albumin concentrations of 80 to 1,200 /ug/ml in human hydatid fluid (HHF). In studies with paper electrophoresis Magath (1959) reported a total protein concentration of 75 [g/ml in HHF, of which 33 /g/ml were in the albumin region and 13.5 1tg/ml in the gamma globulins. Goodchild and Kagan (1961) observed variations in the concentrations of protein in the albumin and gamma globulin regions of the cyst fluids of Echinococcus granulosus and E. multilocularis using paper and starch electrophoresis. They also found differences between cysts of E. granulosus from different host species. Chordi and Kagan (1965) identified and characterized 10 bands of parasite origin in sheep hydatid fluid (SHF) by means of immunoelectrophoresis. Nine other bands were common to host serum and of these albumin and gamma globulin were the major components. From an examination of the electrophoretic patterns reported by these authors it is clear that some parasite antigens in SHF also have electrophoretic mobilities in the albumin and gamma globulin regions. This suggested to us that measurements of their quantities of host albumin and gamma globulin in hydatid fluid by electrophoretic methods does not provide an accurate account of the levels of those components which are truly of host origin. This report concerns the results obtained using radial immunodiffusion as a specific method for determining the levels of host Received for publication 2 December 1971. albumin and immunoglobulin in sheep hydatid fluid. The species specificity of the immunoglobulins in the hydatid fluid obtained from cysts in different hosts was also investigated. MATERIALS AND METHODS Radial immunodiffusion was performed according to the method of Mancini et al. (1965) and immunoelectrophoresis by that of Scheidegger (1955). Rabbit anti-sheep IgG serum IgG was purified from the whole sheep serum by precipitation with 33% saturated ammonium sulfate followed by dialysis against 0.005 M phosphate buffer pH 8 and separation in a DEAEcellulose column, stabilized with the same buffer. The ascending portion of the first eluted peak was used to immunize rabbits. Each animal was inoculated intramuscularly with 300 uug of purified IgG in Freund's complete adjuvant, weekly for 5 weeks. In immunoelectrophoretic tests using normal sheep serum this rabbit antiserum detected a single band in the IgG region.

Habitat specificity and correlated aminopeptidase activity in the acanthocephalans Neoechinorhynchus cristatus and N. crassus.

Abstract: In natural concurrent infections of the large-scale sucker, Catostomus macrocheilus, the acanthocephalans Neoechinorhynchus cristatus and N. crassus occupied ecologically separate regions. N. crassus attached in the anterior intestine, while N. cristatus attached in the posterior intestine. Subadults of N. cristatus had a mean point of attachment 6 cm anterior to adults and occupied a longer section of intestine than did adults. There was no apparent intraspecies difference in distribution of N. crassus. Only subadults of N. cristatus were able to establish infections in abnormal host fishes. These data suggested that habitat specificity was well defined for both age groups of N. crassus and for adult N. cristatus, but was less so for subadult N. cristatus. Fluorometric aminopeptidase (APase) determinations showed the following: (1) extracts of each species possessed a characteristic and reproducible profile of APase activity; (2) posteriorly situated N. cristatus possessed greater and broader APase activity/mg worm protein than did anteriorly positioned N. crassus; (3) on the other hand, posterior host tissues in the environment of N. cristatus contained less activity than anterior host tissues where N. crassus attached; (4) during maturation of N. cristatus, APase levels decreased. Such a change in N. crassus was not observed. These findings suggest that high levels and a broad range of APase activity in subadult N. cristatus are correlated with its generalized habitat selection. The decrease in APase activity with age paralleled its increased habitat specificity. The demonstration of a biochemical basis for parasite-host specificity is difficult because several chemical as well as physical factors may be involved. Cohabiting parasites seldom have been subjects of such studies. Segregation of cohabitants in the environment may reflect the variation of a physiological adaptation in each species. If it is easily recognized, the adaptation and its relationship to habitat specificity may be studied in the laboratory. In preliminary examinations the acanthocephalan Neoechinorhynchus crassus Van Cleave, 1919, was found in large-scale suckers, Catostomus macrocheilus, of Hangman Creek near Tekoa, Washington, but not in those from the Palouse River east of Potlatch, Idaho. N. cristatus Lynch, 1936, was recovered from the same host from both areas. Concurrent infections by both parasites were common in Hangman Creek suckers, and each species tended to segregate in the intestine. As congeners, they Received for publication 6 January 1972. *From a dissertation submitted by the senior author to the graduate school as partial fulfillment of the requirements for the degree of Doctor of Philosophy. t Present address: Department of Biology, Rice University, Houston, Texas 77001. t Present address: Department of Bacteriology, University of Idaho, Moscow, Idaho 83843. represented an excellent model for study of the niche concept and physiological specificity of helminth parasites. Several studies have shown that helminths undergo a change in chemical composition during larval development (Goodchild and Wells, 1957; Archer and Hopkins, 1958; Hopkins and Hutchison, 1958; Mettrick and Cannon, 1970), suggesting that chemical changes are correlated with habitat specificity of developing worms. Using histochemical methods, Crompton (1963) demonstrated the presence of leucine aminopeptidase in the body wall of the acanthocephalan Polymorphus minutus. We have found that extracts of acanthocephalans and other helminths possess extensive and reproducible aminopeptidase (APase) activity on several a-amino acid-,-naphthylamide substrates. The purpose of this study was to examine changes in APase composition of N. cristatus and N. crassus during development from subadults to adults. A concurrent study of their interand intraspecies intestinal distributions gave insight into the dynamic relationship of ontogeny to habitat specificity. MATERIALS AND METHODS From September 1969 to June 1971, largescale suckers, Catostomus macrocheilus (Girard), were collected at monthly intervals by electric

Immunity in rats to superinfection with Fasciola hepatica.

Abstract: Infection of rats with an existing infection of F. hepatica resulted in 92.5% less flukes than had been recovered from infection of previously uninfected rats. The first infection was not detectably affected by the second. Under the experimental conditions, age or weight of the rats at the time of reinfection did not appreciably alter fluke recoveries. Rats were highly immune to superinfection under the conditions described. Some years ago, Thorpe and Broome (1962) suggested that an acquired immunity to a challenge infection had developed in rats previously exposed to irradiated metacercariae of Fasciola hepatica. Further reports have not been noted until the recent article of Corba et al. (1971) who reported that rats which received lymphoid cells from donor animals infected with F. hepatica and animals which had previously been exposed to irradiated metacercariae showed an immunity to challenge infection. While both papers indicated the capacity of rats to develop acquired immunity to F. hepatica, the presence of immunity in rats with an existing infection derived from normal metacercariae remains to be reported. Further, no information is presently available to show the effect, if any, of a challenge infection on an existing infection in rats. This study was designed to show the presence of acquired immunity in rats to superinfection with F. hepatica under conditions which allowed differentiation of parasites from first and second infections and with a control for the possible influence of age resist ance on fluke recovery. MATERIALS AND METHODS Male, CD albino rats (Charles River) were used in the experiment. Unexposed rats from this source have been repeatedly negative for F. hepatica at necropsy. Three groups of similar age and weight were infected as follows: Group 1-infected on days 0 and 49; Group 2-infected on day 0 only; Group 3-infected on day 49 only; and a fourth group (Group 4), whose age and weight on day 49 were similar to those of the above groups on day 0, was infected on day 49 only. All groups were necropsied on day 70. These time periods allowed for distinguishing the parasites resulting Received for publication 8 June 1972. from each infection on the basis of degree of development. Details of the experimental design are shown in the attached table. Metacercariae of F. hepatica were naturally shed by a laboratory-maintained culture of Lymnaea tomentosa infected previously with miracidia obtained from eggs of F. hepatica recovered from the bile of experimentally infected sheep. Each cyst was examined microscopically prior to use, and only those with typical internal morphology were selected (Hayes, 1970). All infections were with 5 metacercariae per rat given by esophageal intubation.

Response of mouse liver to infection with tetrathyridia of Mesocestoides (Cestoda).

Abstract: Tetrathyridia of Mesocestoides were injected intraperitoneally into a large group of mice. Mice were autopsied sequentially to study the progression of pathological lesions. Focal, then diffuse acute inflammation and anoxic hepatocyte necrosis occurred, followed by repair accompanied by massive parenchymal regeneration. Parasite encapsulation was delayed until regeneration had begun. At this time, eosinophils and plasma cells first appeared. In old infections hepatolobular architecture was lost, and there was portal lymphatic obstruction and ascites. These lesions were related to the migratory behavior of tetrathyridia, to the subsequent return of many to the coelom, and to the delayed appearance of specific host resistance. The interaction between tetrathyridia and liver is compared to that of other hepatic parasites. During the study of the asexual multiplication of Mesocestoides tetrathyridia by Specht and Voge (1965) several different gross lesions in the livers of mice were noted. The purpose of this paper is to report the microscopic composition of these lesions, to show progressive changes in their composition as correlated with duration of infection, and to demonstrate how they are dependent on parasite growth and migratory behavior. MATERIALS AND METHODS Swiss albino mice were injected intraperitoneally with 60 tetrathyridia each in 0.85% NaCl containing 500 units penicillin and 500 ,tg streptomycin per milliliter. Tetrathyridia were obtained from the stock infections in mice (Specht and Voge, 1965). Beginning with 2 days postinfection, 1 or 2 mice were examined every 24 hr through 10 days postinfection. From 10 days through 44 days, 1 mouse was examined every 3 days. From 44 days through 65 days, 1 mouse was examined every 7 days. Three mice were included which were selected at random from stock infections of longer duration (188 days, 365 days, and 455 days postinfection). These had received variable numbers of tetrathyridia. Mice were killed by hyperanesthesia; the abdomen was immediately opened Received for publication 28 December 1971. * USPHS General Research Support Grant 5 SO1 FR-5352-04. t Present address: Department of Pathology, Jackson Memorial Hospital, 1700 N.W. 10th Avenue, Miami, Florida 33136. + All correspondence pertaining to this paper and requests for reprints should be sent to Elmer A. Widmer. and the liver was dissected free and washed in 0.85% NaCl. Gross observations were recorded. The liver was selectively sliced so that different pieces contained variable numbers of lesions. Tissues were routinely fixed in 10% formalin, Bouin's, and Zenker's fluids. Carnoy's fluid was used in selected cases. Specimens were embedded in paraplast, sectioned at 7 p, and stained with hematoxylin and eosin, Mallory's trichrome, P.A.S., Masson's trichrome, or Feulgen following the procedures given by Lillie (1965).

Eimeria tenella in bacteria-free and conventionalized chicks.

Abstract: Isolator-reared, uninfected, bacteria-free chicks appeared active and healthy and grew slightly faster than uninfected conventional controls in commercial brooders. Differences between the 2 groups were observed in cecal histology and color and consistency of the cecal contents. Fourteen- day-old and 40-day-old bacteria-free chicks were more resistant than conventional controls to cecal coccidiosis as assessed by the development of clinical signs and cecal pathology and the extent of weight loss and mortality. This indicates that the presence of the flora is involved in the manifestation of clini- cal coccidiosis. The same results were obtained with 2 different diets and a total of 139 of 229 conven- tionals died of coccidiosis whereas none of 89 bacteria-free chicks succumbed. Increasing the oocyst dose increased the severity of the clinical signs in bacteria-free chicks and demonstrated that the flora was not alone responsible for the manifestation of ceoal coccidiosis. Histological observations, oocyst production determinations, and oocyst viability tests showed that the presence of the intestinal flora was not essential for the development of E. tenella. Since fewer first- and second-generation schizonts were observed in bacteria-free fowl, it appears that the presence of the flora favorably affected the early stages of the parasite. Oocyst production, however, was similar in both bacteria-free and con- ventional chicks. Bacteria-free chicks infected with E. tenella produced serum lysins against second- generation merozoites and resisted challenge after conventionalization (placement of bacteria-free chicks into conventional animal housing facilities) as well as conventional controls. Experiments with con- ventionalized chicks indicate that mortality, cecal pathology, and clinical signs, but probably not oocyst production, were related to the presence of the flora during E. tenella infection. The earlier in infection the flora was established in bacteria-free fowl the more similar to the conventional syndrome the disease became.

Reciprocal responses of eight species of galliform birds and three parasites: Heterakis gallinarum, Histomonas meleagridis, and Parahistomonas wenrichi.

Abstract: Embryonated eggs of Heterakis gallinarum from chickens and turkeys, carrying both Histomonas meleagridis of relatively low virulence and Parahistomonas wenrichi, were fed to 8 species of galliform birds. Heterakis developed best in young ring-necked pheasants, with young guinea fowl next best, and then young New Hampshire chickens. No mature heterakids were recovered from young chukar partridges and young turkeys or mature Japanese quail and bobwhites. In year-old Hungarian partridges a few female heterakids matured, but yielded only 8 embryonated eggs per 100, such eggs given. Histomonas meleagridis was detected in only 1 of 8 (12%) of each of the following: mature Japanese quail, bobwhites, Hungarian partridges and ring-necked pheasants, and infections were of short duration. Fifty percent of the guinea fowl and chickens, 62% of the turkeys, and 88% of the chukar partridges became infected. There was no mortality. Only the pheasants and chickens produced worms with eggs that transmitted Histomonas to susceptible turkey poults. P. wenrichi appeared in only guinea fowl, chickens, pheasants and turkeys, and usually only when Histomonas was absent or no longer in the tissues. During the past 18 years, more than 40 experiments conducted at this Laboratory have compared the responses of various species of galliform birds to one or more of the parasites associated with histomonad infections: Histomonas meleagridis (Smith, 1895) Tyzzer, 1920; Heterakis gallinarum (Schrank, 1788) Madsen, 1949; and Parahistomonas wenrichi (Lund, 1963) Honigberg and Kuldova, 1969. These comparisons, made with hosts given the same inoculum, usually included the responses of 5to 8-week-old New Hampshire chickens and Beltsville Small White turkeys (Lund and Ellis, 1967; Lund, 1967b; Lund and Chute, 1970, 1971a, b, 1972). Almost always, the size of the infective dose was governed by knowledge of the influence of three factors: the strain of parasite to be used, its adaptation to a particular host species (Lund et al., 1970), and the host species to be inoculated; this knowledge was obtained by pretesting the infective material. However, all three parasites were not studied in each experiment, and the influencing factors mentioned above were not uniform throughout. The present study employed for the first time the same inoculum for gallinaceous birds of eight species, with uniform methods throughout for studying responses of all eight hosts Received for publication 3 March 1972. and all three parasites, including the ability f the parasites to perpetuate their kind. MATERIALS AND METHODS