Louis Olivier

Observations on the migration of avian schistosomes in mammals previously unexposed to cercariae.

The cercariae of schistosomes which normally reach the adult stage in birds have long been known to be able to penetrate the skin of man and various other mammals. When these cercariae penetrate man they may cause a severe papular dermatitis which has been the subject of extensive investigations over a period of many years (Cort, 1950). Vogel (1930) and Brackett (1940) studied biopsies of typical papules caused by avian schistosomes in the human skin and found that the worms remained in the

The early larval stages of Schistosoma mansoni Sambon, 1907 in the snail host, Australorbis glabratus (Say, 1818).

In a series of related studies Cort and his associates have presented information on the early larval stages of trematodes belonging to the groups Strigeata (Cort and Olivier, 1941), Schistosomatoidea (Cort and Olivier, 1943b; Cort, Ameel, and Olivier, 1944), Plagiorchioidea (Cort and Olivier, 1943a; Cort and Ameel, 1944), and the Fasciolatoidea (Cort, Ameel, and Van der Woude, 1948). In these investigations the morphology of the larval stages was studied in considerable detail and special emphasis was placed on determination of the method of reproduction. Prior to these studies, detailed information on the early developmental stages of trematodes in the groups mentioned was very meager. Two of the studies dealt with schistosomes. Cort and Olivier (1943b) reported on the early developmental stages of Trichobilharzia stagnicolae (Talbot, 1936). It was shown that the mother sporocysts are relatively large, elongate, sausageshaped sacs usually located in the head-foot region of the snail. They produce numerous daughter sporocysts by means of multiplication of the germinal cells (primary polyembryony) and by a special form of polyembryony involving germinal masses2 (secondary polyembryony). In the daughter sporocysts the cercarial embryos are also produced by multiplication of the germinal cells and by polyembryony involving germinal masses in the same manner as the daughters themselves were produced. In the second of the two studies dealing with schistosomes Cort, Ameel, and Olivier (1944), desribed the developmental stages of Schistosomatium douthitti (Cort, 1914). They found that division of the germinal cells in the miracidium results in production of about 200 germinal cells in the young mother sporocyst. Each of these germinal cells develops into one daughter sporocyst. These daughters leave the mother and migrate to the digestive gland. Germinal cells carried in the daughter sporocysts multiply until about 200 cells result. Most of these cells develop into cercariae, but a few give rise to germinal masses which in turn produce cercariae. No germinal masses were seen in the mother sporocysts and only a few were seen in the daughter sporocysts, suggesting that polyembryony by germinal masses in this species is relatively uncommon. It was felt desirable to compare the development of the schistosomes of man with that described for T. stagnicolae and S. douthitti. There is little available information on the early larval stages of Schistosoma haematobium and Schistosoma japonicum. Only Maldonado and Acosta-Matienzo (1947) have presented detailed in-

NATURAL RESISTANCE TO TAENIA TAENIAEFORMIS I. STRAIN DIFFERENCES IN SUSCEPTIBILITY OF RODENTS

Mice, rats, guinea pigs, and hamsters were fed eggs of Taenia taeniaeformis. Wide differences in susceptibility to infection were found. Mice of some strains were as susceptible as rats while in other mouse strains no larvae survived to produce normal cysts. Rat strains also differed both as to number and size of liver lesions formed. In guinea pigs larvae reached the liver but none survived to form normal cysts. In hamsters there was no evidence of migration to the liver. A series of four experiments revealed that the sex of mice has little or no effect on susceptibility to infection. The importance of quantitative study of cyst size as well as cyst number is emphasized.

Studies on natural resistance to Taenia taeniaeformis in mice. II. The effect of cortisone.

Mice of three strains were fed eggs of Taenia taeniaeformis, and the effect of small amounts of cortisone acetate on development of larvae in the mouse livers was studied. Cortisone has a profound effect on larval survival and can make refractory hosts highly susceptible. To be effective the cortisone must be given before the 12th day of infection. It is effective when used for 8, or even 4, days. It is postulated that the cortisone is effective, at least in part, because of its inhibition of antibody production. It has been shown that strains of mice exhibit great differences in their susceptibility to infection with Taenia taeniaeformis (Olivier, 1962 for review). Since cortisone influences the capacity of organisms to resist a wide variety of infectious agents, it was of interest to learn what effect cortisone might have on the response of mice to this parasite. Accordingly, cortisone was given to mice infected with Taenia taeniaeformis, and the lesions developing in the mouse livers were studied. MATERIALS AND METHODS The procedures used for collection of tapeworm eggs, preparation of egg suspensions, exposure of mice, and examination of the mice have been described previously (Olivier, 1962). Of the three mouse strains used, two (A/LN and C57BL/6JN) are closely inbred lines, and the third (C3H/p) is a random-bred strain. Cortisone acetate (Merck Cortone) was used in all experiments. It was given daily, subcutaneously, in 0.1 ml of fluid. The daily amount of cortisone was always 0.2 mg except as indicated in the text. This amount was chosen more or less arbitrarily, but it turned out to be favorable. The cortisone did not affect the weight of the mice and had no noticeable effect on their health. When the cortisone schedule was varied from one group of animals to another, saline injections were given in such a way that all animals in the experiment received the same total number of daily injections. Thus, when cortisone was started in one group, injections of saline were started in all other groups, and either cortisone or saline was then given daily to all animals including controls until the cortisone schedule was completed in the last animals. Experimental procedure The usual pattern of the experiments was to Received for publication 25 June 1962. * Laboratory of Parasitic Diseases. feed eggs from a single suspension to a series of mice, give some of the mice cortisone injections, and examine the mice approximately 4 weeks after infection in order to record the number and size of all liver lesions. The number of days on which cortisone was given was varied from group to group and from experiment to experiment. In some cases the cortisone injections began 4 days (-4) before the mice were fed eggs. The day eggs were fed was designated as day 1. Cortisone was continued in some cases up to day 20. In the last two experiments some of the mice were examined more than 4 weeks after infection. The diameter of the liver lesions indicates the quality and vitality of the larvae. All lesions having a diameter of 4 mm or more after a 4-week period of development in the liver contain normal larvae. The size of the large lesions is proportional to the size of the larvae in the lesions since the cyst wall is very thin. Some lesions less than 4 mm in diameter may contain living larvae, but the larvae are relatively retarded and some are obviously abnormal or moribund. The small lesions have no parasite in them and so represent only remnants of the tissue response to infection. Thus, mice with small lesions are hosts that have not permitted the successful development of the larvae, while mice with large lesions are hosts that have permitted the larvae to develop normally.

Observations on vectors of schistosomiasis mansoni kept out of water in the laboratory. I.

Recently, the habits and seasonal cycles of Australorbis glabratus and Tropicorbis centimetralis, intermediate hosts of Schistosoma mansoni, were studied intensively in the field in Brazil (Olivier and Barbosa, 1955a, b). In the course of these studies, the observations of Barbosa and Dobbin (1952) concerning the ability of A. glabratus to live out of water were confirmed and extended, and similar observations were made on T. centimetralis. In conjunction with these field studies, the snails were also studied in the laboratory where the environmental conditions were more constant and under a measure of control and where individual snails could be observed for long periods of time. Some of the experiments were designed to determine how long the two vector species could live out of water in the laboratory and whether there are strain differences within the species with respect to their ability to do this. In one group of such experiments, the snails were maintained without water in unglazed clay jars for long periods of time. The results of these experiments will be described here.

Nitrogenous Excretory Products of Taenia taeniaeformis Larvae

The work reported here is a continuation of a study of the catabolic nitrogenous products of parasitic larvae living under axenic conditions. Previous papers have described the results obtained with certain nematode larvae (Weinstein and Haskins, 1955; Haskins and Weinstein, 1957a, b, c). This report extends the observations to another class, the Cestoda. Apparently there is no published information concerning the nitrogenous products released by cestodes into the ambient medium. However, urea, uric acid, creatinine, and betaine have been found in Echinococcus cyst fluid (Mazzocco, 1923; Fl6ssner, 1925; Lemaire and Ribere, 1935; Codounis and Polydorides, 1936); ammonia has been found in the tissues of Moniezia expansa (van Grembergen and Pennoit-DeCooman, 1944); Schopfer (1932) reported urea and uric acid from the cyst fluid of Cysticercus tenuicollis; and Salisbury and Anderson (1939) found ammonia, urea, and uric acid in the tissue of larval Taenia taeniaeformis (Cysticercus fasciolaris).

The influence of light on the emergence of Schistosomatium Douthitti cercariae from their snail host.

It has long been known that under laboratory conditions the cercariae of Schistosomatium douthitti (Cort) normally emerge from their snail host in the evening. It is assumed that this is also true under field conditions. In infection experiments involving this species, then, the investigator must either set up the experiments at night or during the morning following the emergence of the cercariae when they are 12 hours or more old. The inconvenience of doing routine infection experiments at night and the undesirability of using cercariae 12 hours or more after they have emerged tend to limit the use of this species for experimentation. When S. douthitti was being considered for use in laboratory experiments it was recognized that the species would be more useful if the cercariae could be induced to emerge earlier in the day. Modification of the daily light cycle suggested itself as the most likely way that this could be brought about. Accordingly, an experiment was designed to test whether the shedding cycle could be changed by alteration of the light cycle. The results of this experiment are reported here.

Experimental Schistosome Dermatitis in Rabbits.

that in the skin of unsensitized persons there was a slow dissolution of the parasites in the epidermis with the formation of parakeratotic plaques. On the other hand, Olivier (1949a, 1953) showed that following skin penetration of unsensitized mice, hamsters, guinea pigs, rabbits, and rhesus monkeys by avian schistosome cercariae, some of these worms migrated to the lungs of these animals. Penner (1941) showed that a schistosome of small mammals, Schistosomatium douthitti, could penetrate the skin of monkeys and migrate to the lungs. These observations demonstrated that although some of the schistosome cercariae that penetrate unsensitized laboratory animals may be destroyed in the skin, others leave the skin and reach the lungs. Furthermore, the observations on the migration of the schistosomes in monkeys suggest that migration of the same species to the lungs of man is a possibility. In order to learn more concerning the fate of avian schistosomes in both sensitized and unsensitized animals, a study was made in rabbits of the skin reactions to these parasites. Rabbits were sensitized to schistosomes; skin biopsies were then made from these and from control rabbits after a challenge exposure to the same species of parasite. MATERIALS AND METHODS

Larval trematode infection in juveniles and adults of Physa parken Currier.

Studies on the ecological relations of larval trematode infections in Stagnicola emarginata angulata (Sowerby) have been carried out during the last five summers at the University of Michigan Biological Station (see Cort, McMullen, and Brackett, 1937; Cort, McMullen, Olivier, and Brackett, 1940a). One of the most interesting parts of this work has been the comparison of infections in juvenile and adult snails. In the summers of 1938 and 1939 the ecological studies were extended to include the larval trematode infections of juveniles and adults of Physa parkeri Currier, a very large beach snail, and, in addition, its life cycle was worked out. Two preliminary publications have already been made on certain phases of this work (Cort, McMullen, and Olivier, 1938; Cort, McMullen, Olivier, and Brackett, 1940b). In this paper all the data obtained on the life cycle of P. parkeri and on its larval trematode infections are presented.

A new trematode, Allassogonoporus marginate, from the muskrat.

Forty-five trematodes were collected from the small intestine of a muskrat (Ondatra zibethica L.) trapped in the vicinity of Whitehall, Michigan. The specimens differ notably from all described species and cannot be included in any of the existing genera. The species is named Allassogonoporus marginalis n. g., n. sp. and is assigned tentatively to the family LECITHODENDRIIDAE. The first account of trematodes from the muskrat was made by Leidy (1888). He reported two species, one as Echinostomum echinatum Zeder and the other, of which he had only two specimens, as Amphistomum subtriquetrum Rud. Barker (1915) regarded the latter as Wardius zibethicus and listed nine species, seven of which were described briefly by himself and his associates. Price (1931) added four new species and a key. Recently Warwick (1936) tabulated all of the parasites that have been reported from the muskrat in Europe and North America. This list included twenty-one species of trematodes and, of these, Notocotylus quinquiserialis, Cladorchis subtriquetrus, and Fasciola hepatica have been collected in Europe. It is probable that certain species listed by Warwick, such as Fasciola hepatica and Paragonimus sp., are only occasional parasites in the muskrat. It is of interest to note that Ondatra zibethica L. is a North American species introduced into Europe.