Showing papers in "Parasitology in 1976"

Methods in coccidiosis research: separation of oocysts from faeces.

Abstract: Factors which may be important in the large-scale extraction of coccidial oocysts from faeces ha.ve been investigated with Eimeria tenella. Age of bird, inoculum, feeding status at the time of inoculation, period of collection, feeding status during collection, collection medium, homogenization and sieving, flotation, washing, sporulation and further purification have all been considered. The aim has been to establish a method to produce the maximum number of oocysts of a required degree of purity and viability, with the expenditure of the minimum amount of physical effort, time, animals and chemicals. In our method, groups of chickens 3-4 weeks of age are inoculated with 5000 oocysts of E. tenella and food is supplied ad lib. Over the period 5-8 days after inoculation, faeces are collected in trays containing 2% (w/v) potassium dichromate solution, while food intake is restricted. The faecal material is homogenized, passed once through 40 and 100 mesh sieves, centrifuged and the oocysts recovered from the sediment by 3 flotations in saturated salt solution. Following washing, oocysts are sporulated by forced aeration at 30 degrees C and may be further purified by hypochlorite treatment, or passage in 5% Tween 80 solution through a glass bead column followed by sucrose density gradient centrifugation. Routine passages along these lines over a 5 year period have given a recovery of 46% of the oocysts excreted by over 7000 birds.

The tylenchid (Nematoda) egg shell: structure, composition and permeability

Abstract: The fine structure of egg shells of four different genera belonging to the order Tylenchida has been examined. The species examined were Meloidogyne javanica, Rotylenchulus reniformis, Tylenchulus semipenetrans and Pratylenchus minyus. They are all similar in their basic structure, being composed of vitelline membrane, chitin and lipid layers, but there is considerable variability in the thickness of these layers.We have retained the conventional nomenclature because of its convenience, but it is clear that these layers have a variety of chemical components. However, they do appear to contain the compounds from which they take their name. Thus chitin occurs in the chitin layer, and lipid in the lipid layer. The latter is removed by the technique used in isolating the shell from the egg. Chemical analysis of the hydrolysis products of these shells has revealed a high (35 %) proline content which appears to be a characteristic of those nematode egg shells which have been examined so far. These analyses and treatment with enzymes indicate that the chitin layer is a chitin–protein complex.Experiments on the permeability of eggs of M. javanica at different temperatures indicate that changes in permeability are not due to the melting of a single lipid with a distinct melting point as had been thought in the past. We have found that Arrhenius activation energies calculated from the two slopes of an Arrhenius plot were 17·8 kcal/mol and 43·0 kcal/mol respectively, the transition from one to the other taking place at 62°C. We think that these changes are due to changes in the properties of lipoprotein membranes in the lipid layer. These membranes appear to be of paramount importance in controlling the permeability of the nematode egg shell.

Immunity to primary and challenge infections of Trichinella spiralis in mice: a re-examination of conventional parameters.

Abstract: In young (6- to 8-week-old) NIH strain inbred mice expulsion of a primary infection of Trichinella spiralis began on day 8 and was virtually complete by day 11-5. In older mice expulsion occurred 1 or 2 days earlier. Experience of a primary infection elicited strong immunity to challenge, whether the challenge was given immediately after worm expulsion (day 14) or delayed (day 42). Challenge infections were expelled rapidly the majority of worms being lost during the first day. Immunity to challenge was elicited by low-level primary infections and was effective against large ventionally accepted parameters of immunity to T. spiralis in mice which, it is considered, are applicable only to mice with a genetically determined low-level of responsiveness to the parasite.

Immunity to coccidiosis: stages of the life-cycle of Eimeria maxima which induce, and are affected by, the response of the host.

Abstract: An attempt was made to determine the relative importance of the different life-cycle stages of Eimeria maxima in the induction of immunity and also those stages most affected by the immune response of the host. In one experiment the life-cycle was controlled by chemotherapy but in all other experiments partial life-cycles were induced by transfers of infected mucosa between hosts. The results indicated that the second generation schizont stage is probably that most concerned in the induction of protective immunity and that sexual stages are most susceptible to immune inhibition. After initial inhibition in the immune host the earlier asexual stages were able to resume development when transferred to a susceptible host. The longer the period of exposure to the immune environment, the less able was the parasite to recover.

The immunity arising from continuous low-level infection with Eimeria maxima and Eimeria acervulina.

Abstract: Chicks were given daily inoculations of 1 or 5 oocysts of Eimeria maxima or 5 or 20 oocysts of E. acervulina. The inoculations ceased after 20 days with E. maxima or 25 days with E. acervulina when oocyst production had stopped. The responses to subsequent heavy challenges showed that with both species the immunity arising from the serial inoculations was stronger and/or more enduring than that produced by single inoculations of comparable numbers of oocysts.

A genetic investigation of virulence in a rodent malaria parasite.

Abstract: The genetic basis of virulence in a line (YM) of Plasmodium yoelii yoelii was investigated in a cross with a mild line (A/C). The blood forms of the virulent line developed extensively in mature erythrocytes of mice, causing death of the host within 7 days; infections with the mild line were normally restricted to reticulocytes, infected animals recovering after three weeks. Lines YM and A/C differed additionally in enzyme and drug-sensitivity markers. Studies on infections established from each line alone from sporozoite mixtures of the two lines and from the cross between the lines showed that the appearance of virulence had been caused by a genetic change in the parasite, and not by other factors such as a concurrent infection with another organism. An analysis of the characters of 56 clones derived from the cross showed that the virulence character had undergone recombination with the other markers, and appeared to be inherited in Mendelian fashion. Three clones exhibited atypical virulence, although it was not clear whether this had been produced by genetic recombination.

Schistosoma mansoni in the baboon (Papio anubis): parasitological responses of Kenyan baboons to different exposures of a local parasite strain.

Abstract: The course of infection with a local strain of Schistosoma mansoni was investigated in Kenyan baboons (Papio anubis). A single exposure to 5000 cercariae per baboon (cpb) killed five 4-8 kg baboons; a sixth survived the full 30-week post-exposure period, with suppressed egg production after week 11. Lower doses were not lethal. A single exposure to 1000 cpb gave satisfactory adult worm recoveries, high and steady faecal egg excretion, and a high tissue egg recovery, predominantly from the large intestine. A similar but less consistent picture was obtained with a single exposure to 200 cpb. Baboons receiving 5 monthly exposures of 200 cpb (1000 cpb total) showed some evidence of the development of protective immunity. Three animals showed patterns resembling those for 200 and 1000 cpb. The other 3 had suppressed egg production (faecal and tissue) indicating, perhaps, some immunological process. They also had an abnormally high percentage of eggs in the liver.

Accelerated expulsion of adult Trichinella spiralis in mice given lymphoid cells and serum from infected donors

Abstract: Immunity to the adult stage of Trichinella spiralis , assessed by an acceleration of worm expulsion, was transferred to recipient mice with mesenteric lymph node cells (MLNC) or serum taken from infected donors. Immunity was transferred most effectively by MLNC taken from donors infected for 8 days, i.e. donors actively responding to infection. Transfer of both MLNC and serum brought about a marked acceleration of worm expulsion in all cases, even where MLNC or serum given separately failed to transfer a significant degree of immunity.

Studies on the induction of permeability in Ascaris lumbricoides eggs.

Abstract: The initial process in the hatching mechanism of Ascaris eggs is the sudden onset of permeability in the previously impermeable ascaroside membrane. During this change the ascaroside membrane remains intact and no chemical changes can be detected. Using the molecular probe 1-anilino-8-naphthalene sulphonic acid no conformational changes were detected in the ascaroside membrane during the induction of permeability. It is suggested that either the permeability change is due to a very localized chemical or conformational change, not detectable by conventional analytical techniques, or the change is due to mechanical damage of the ascaroside membrane, brought about by the activity of the infective larva.

Experiments with defined multispecific coccidial infections in lambs.

Abstract: The behaviour of four species of Eimeria was studied in lambs which were given either monospecific or multispecific infections. In the presence of other species the patency of oocyst production of E. ovina and E. weybridgensis was extended and the total number of oocysts produced by all species except E. ninakohlyakimovae was increased. Clinical symptoms were observed only in lambs which received E. ninakohlyakimovae.

The effect of human immune IgG on the in vitro development of Plasmodium falciparum.

Abstract: Plasmodium falciparum parasites infecting Aotus trivirgatus erythrocytes were cultured in media (Harvard and TC199) augmented with human, foetal calf, or other sera. Conditions were established which supported growth of parasites and allowed cyclical multiplication when fresh erythrocytes (from Aotus or Homo) were added in sub-culture (mean multiplication rate: X3). Immunoglobulin G pools, prepared from plasma collected in endemic malarious areas in Africa and from unexposed Britons, were tested for effects on the in vitro growth (measured by incorporation of tritiated leucine) and multiplication of parasites. Whilst non-immune IgG was without effect, IgG from both East and West Africa inhibited the multiplication of East African (Uganda-Palo Alto strain) parasites.

Seasonal variation in the population dynamics of Caryophyllaeus laticeps.

Abstract: The biological parameters which generate seasonal fluctuations in the size of populations of Caryophyllaeus laticeps are examined in detail. A mathematical model is formulated to describe the dynamics of the adult parasite within the fish host Abramis brama, and the predictions of the model are compared with observed population data. The seasonality of parasite population size is shown to be caused by the combined effects of a temperature dependent mortality rate and flucate of larval parasites. The observed overdispersed distribution of adult parasite numbers within the host population is shown to be generated by variability in feeding habits between individual members of the fish population. The theoretical population model is used as a framework for the investigation of, among other factors, the comparative influences of the immigration and death rates on the dynamics of the adult parasite, the future behaviour of the system under altered environmental conditions and the importance of chance effects in the dynamics of individual parasite populations within a single host. The stability of the dynamics of the complete life-cycle of C. laticeps is discussed in relation to the inherent biological complexity of host/helminth parasite interactions.

Boophilus microplus: the effect of host resistance on larval attachments and growth.

Abstract: Growth and behaviour of Boophilus microplus larvae on British breed cattle, with different resistance levels to the tick, were studied to elucidate the nature of resistance. On highly resistant animals, larval growth rate was slower for the first 3 days, but by day 4 they had attained the normal weight and the majority were subsequently able to moult. Using phosphorus-32 labelled larvae, it was found that attachment times were shorter and more time was spent wandering on highly resistant animals during the first 16 h. On the second day, attachments had stabilized, but more detachments were still made from highly resistant animals. This was considered to impose an additional stress as the cattle skin environment can rapidly desiccate larvae. However, the larvae were able to compensate by uptake of fluid from the host. Loss by repulsion of live larvae from the host or drowning in serous exudate were also not considered of major importance. The nature of rejection is discussed in a further paper. The distribution of larvae after 24 h suggests that their early behaviour largely determines the areas favoured by adults. Movement to, and accumulation in, favoured areas is discussed.

Echinococcus granulosus: development in vitro from oncosphere to immature hydatid cyst.

Abstract: Echinococcus granulosus cysts were cultured in vitro from the oncosphere, and cyst morphogenesis is described. Cysts grew to a mean diameter of 16 mm in 120 days, with a maximum of 20 mm. An amorphous layer was apparent around the larvae during early post-oncospheral re-organization. Organisms became vesicular at 6 days and laminations appeared in the amorphous layer at 10 days. Confluence of proliferating cells to form the syncytium of the germinal membrane was observed.

The cestocidal effect of complement in normal and immune sera in vitro.

Abstract: The effects of complement and/or specific antibodies on the larval and adult stages of Echinococcus granulosus were studied in vitro . Lysis and death of both protoscoleces and adult E. granulosus occurred within 10 min to 24 h in 50% fresh normal sera used as a source of complement, without the presence of specific antibodies. The lytic and lethal reaction was marked in fresh sera from guinea-pigs, calves, dogs, man and sheep, but only slight in fresh sera from English rabbits and horses. Guinea-pig sera were shown to be complement deficient after reacting with worms and all reactions were abolished after sera had been heated to 56 °C for 30 min. Fluorescent antibody studies failed to detect host antibodies at the parasite tegument. It is suggested that activation of the complement system occurs via the alternate pathway, that it acts independently of the immune system and that it is lethal to a wide range of cestode parasites. In contrast, marked agglutination/precipitation reactions with protoscoleces and precipitation reactions with adult E. granulosus were observed after incubation in heat inactivated 50% canine antisera, but not in normal sera. The antigen-antibody nature of these reactions was established by fluorescent antibody studies and the areas of antibody attack pinpointed. In spite of these reactions, worms remained healthy and active over a period of 8 days.

Development of Isospora bigemina in dogs and other mammals

Abstract: The life-cycle of canine Isospora bigemina was studied in dogs, cattle, cats and mice. Under experimental conditions dogs served as both definitive and intermediate hosts. Unsporulated oocysts (11 X 12 mum) were shed in the faeces and sporulated outside the host within 12 h at 30-37 degrees C and 36 to 48 h at 23 degrees C. Sporulated oocysts measured 12 X 13 mum and contained 2 sporocysts which in turn contained 4 sporozoites. Sporocysts averaged 6 X 9 mum and sporozoites averaged 2 X 6 mum. Although no stages were found microscopically in tissues or in faeces of 23 dogs orally inoculated with sporulated oocysts, the oocysts were infectious because 5 of 14 dogs that ingested tissues of dogs fed oocysts, shed oocysts. Prepatent periods were 7 to 15 days; patency was 1-3 days. No dogs became ill. In the naturally infected dog and one experimentally infected dog, schizonts were found in epithelial cells, distal to the host cell nucleus at the tips of villi throughout the small intestine. Schizonts were 5-7 mum and contained 3-12 merozoites. In the naturally infected dog, gametes were found in the same location. Male gametocytes were 6-8 mum and contained 6-12 microgametes, and female gametes were 7-8 mum. Sporulated I. bigemina oocysts from a naturally infected dog were not infectious to cattle, cats or mice. Structurally identical oocysts were shed by 2 dogs after ingesting hearts and diaphragm from naturally infected cattle; these oocysts were also not infectious to cattle. Although dogs acted as both intermediate and definitive hosts under experimentation, this is not likely to occur in nature. A canine-bovine-canine cycle would appear to be the natural mode of infection but I. bigemina was not infectious to cattle under experimental conditions.

Some observations on the sexual differentiation of Eimeria tenella using single sporozoite infections in chicken embryos.

Abstract: Unsporulated oocysts were recovered from the allantoic cavity of 5 chicken embryos inoculated with a single sporozoite of Eimeria tenella; some of these oocysts sporulated. Both macrogametes and microgametes are required for the formation of viable oocysts. The results conclusively demonstrate the bisexual nature of the sporozoite, suggest that sexual differentiation is influenced by environmental factors, and show that true clones of Eimeria can be established from individual sporozoites.

The sites occupied by the acanthocephalan Pomphorhynchus laevis in the alimentary canal of fish.

Abstract: The distribution of the acanthocephalan Pomphorhynchus laevis along the alimentary tract of several species of freshwater fish was studied in both natural and experimental infections. The parasite exhibits a clear preference for a particular region of the alimentary canal, which differs from host species to host species, but it is capable of surviving in all regions of the intestine. In some host species, but not in all, its growth rate may be reduced in regions outside of the preferred site. The parasite remains in the same site throughout the period of infection, emigrations occurring only preparatory to complete loss of the parasite from the host. The presence of cestodes in the region of the preferred site has no effect upon the distribution of the parasite. At high levels of infection the range of the parasite's distribution is extended. The feeding of larval parasites to fish by stomach tube also leads to an extension of range, whereas when fish are allowed to feed on cystacanths removed from their intermediate host the parasite establishes in a more anterior position than usual and in a site that it does not occupy to any extent in natural infections. It is concluded that the distribution of P. laevis in the alimentary canal offish is determined primarily by the process of liberation, activation and establishment of the parasite, and that it normally attaches in the first available space and remains there. Unsuitable physico-chemical or feeding conditions affect only its growth, not the site that it occupies. It is suggested that P. laevis may be atypical in this respect.

Effects of a series of infections of Ostertagia circumcincta on gastric secretion of sheep.

Abstract: Sheep which had been either previously infected with O. circumcincta or maintained worm-free, were surgically prepared with separated fundic pouches and abomasal cannulae and subsequently infected with 20000 O. circumcincta larvae three times weekly.A reduction in food intake and increases in total acid output from the pouches and plasma pepsinogen levels were evident in both groups of sheep 4 days after repeated infections commenced; effects which increased in severity after 12 or more days. Except for a transient period of slight failure, previously infected sheep retained the capacity to acidify their abomasal contents whereas previously worm-free sheep lost this capacity. These changes were reversed between 2 and 7 days after treatment with thiabendazole (88 mg.kg−1).Secretory capacity of the fundic pouches was tested with histamine (40 μg.kg−1), the histamine antagonist (burimamide 8mg.kg−1) and atropine (100 μg kg−1). Ostertagiasis reduced or abolished the stimulatory effects of histamine. An increase in secretion volume and acid output was obtained after food was freshly provided, even though as little as 25 gm was consumed. Atropine and burimamide both caused a profound decrease in pouch secretion and acid output.These data are consistent with the hypothesis previously stated that in ostertagiasis the hypersecretion from fundic pouches is due to increased levels of circulating gastrin.

Evasion of the haemocytic defence reaction of certain insects by larvae of Hymenolepis diminuta (Cestoda).

Abstract: Larvae of Hymenolepis diminuta develop in the haemocoele of the beetles Tribolium and Tenebrio, and of the locust Schistocerca gregaria, without being encapsulated by haemocytes. The mechanism of this evasion of the haemocytic defence reaction has been examined using various techniques. Larvae grown in culture and injected into S. gregaria have a few or no haemocytes adherent even after 8h, although latex beads injected at the same time have been thickly encapsulated. This, and results of transplanting cysticercoids and host tissue between different insect species, suggests that the surface of the larvae may bear an inherent similarity to the surface of host tissues and thus escape recognition as 'not-self' by the host's haemocytes.

The tegument of Schistosoma mansoni: a histochemical investigation.

Abstract: The main components of the schistome tegument were found to be neutral glycoprotein and phospholipid; a small quantity of glycolipid was observed in the male dorsal tegument. The tegument can be differentiated from other schisotsome tissues on the basis of enzyme content; three hydrolytic enzymes were shown to be specifically localized in the tegument: alkaline phosphatase, adenosine triphosphatase and indoxyl esterase. It is suggested that these enzymes could be used as intrinsic markers for tegument structures. The subtegumental cells appear to be the major sites of biosynthetic activity since they contain large amounts of RNA and mitochondrial enzymes.

Schistosoma mansoni: the occurrence of microvilli on the surface of the tegument during transformation from cercaria to schistosomulum.

Abstract: Microvilli are developed on the surface of Schistosoma mansoni schistosomula during penetration of the host skin; they form rapidly but are lost approximately 90 min after penetration. Identical microvilli are also formed on schistosomula which have penetrated a mouse skin preparation in vitro, and on schistosomula prepared by mechanical separation of the tail from the body of the cercaria. The microvilli, which are limited by the trilaminate tegumental membrane of the cercaria, eventually degenerate and are cast off from the surface of the tegument. There is little change in the surface area of the schistosomulum at this time, and the formation and loss of microvilli coincides with the replacement of the cercarial tegumental membrane by the new heptalaminate membrane. It is suggested that during the cercaria/schistosomulum transformation, some intramembraneous components of the original cercarial membran e may migrate into the new heptalaminate membrane and thus be retained, while other peripheral components such as the glycocalyx are almost certainly lost.

The tylenchid (Nematoda) egg shell: formation of the egg shell in Meloidogyne javanica

Abstract: Oogonia of Meloidogyne javanica are radially arranged around a central rachis to which they are attached by cytoplasmic bridges. As the oocytes mature the rachis disappears and the oocytes pass through the oviduct in tandem. The oviduct-spermatotheca valve is constructed of two rows of tightly packed cells of which there are four per row. The nuclei of these cells are large and contain balloon-shaped cytoplasmic invaginations. The spermatotheca is characterized by microtubules which extend to its lumen and by invaginations of plasmalemma. Cells of the distal uterine region contain large intracytoplasmic spaces bordered by endoplasmic reticulum whereas proximal uterine cells have dense cytoplasm and large areas of compact endoplasmic reticulum. Egg-shell formation begins in the spermatotheca with the modification of the oolemma to form the vitelline layer. The chitinous layer begins in the distal portion of the uterus and appears to originate from the egg. Proline-containing protein is incorporated into the chitinous and lipid layers as the egg passes through the mid-region of the uterus and formation of the lipid layer in this region completes egg development.

Fine structural observations on oocyte development in monogeneans.

Abstract: The ultrastructural changes accompanying oocyte differentiation in the ovaries of the monogeneans, Diclidophora merlangi, Diplozoon paradoxum and Calicotyle kroyeri have been described. In each case, oogenesis in the ovary proceeds as far as meiotic prophase in the primary oocyte. A three-stage sequence of development based on oocyte morphology is proposed: (1) Oogonia and early, immature primary oocytes are typically undifferentiated, with chromatin-laden nuclei occupying most of the cell volume. The cytoplasm contains small clumps of mitochrondria and unattached ribosomal aggregates. There is evidence of mitosis and, in later stages, meiotic prophase is indicated by the appearance of nuclear synaptonemal complexes. (2) Maturing primary oocytes are characterized by increased nucleolar volume associated with the production of RNA for export to the cytoplasm. An organized GER and Golgi apparatus are established and involved in the synthesis and packaging of membrane-limited cortical granules. Annulate lamellae and nucleolus-like bodies appear in the cytoplasm and, with development, the cells increase in size and, peripherally, become interdigitated. (3) Mature primary oocytes represent a resting phase when cellular activity is minimal. Golgi disappear and the ER fragments or becomes reduced in dimensions. Mitochondria and free ribo-somes are numerous and cortical granules move to the cell periphery. The cells separate and, when mature, are released from the ovary. There are minor species differences in oocyte ultrastructure and development.

Cross-immunity to Schistosoma mansoni and S. haematobium in the hamster.

Abstract: Hamsters (WO strain) with a primary infection of Schistosoma mansoni or S. haematobium rapidly developed immunity to homologous challenge judged by the lung recovery assay. Immunity was detected at 4–5 weeks and reached a plateau 6 weeks after infection. Using this information, hamsters with an 8-week primary infection with S. mansoni or S. haematobium were tested for resistance to homologous reinfection and resistance to a challenge with the other species of schistosome. Primary infection with S. mansoni or S. haematobium conferred a high level of immunity to reinfection with either species of schistosome judged by the perfusion assay, involving recovery of adult worms 6–10 weeks following challenge. Estimation of the level of immunity with the lung recovery assay, 5 days after challenge, indicated that immunity due to a primary infection with S.mansoni acted at or before migration of the challenge through the lungs but immunity stimulated by a primary S. haematobium infection was only partially effective at the lung stage and substantial destruction of challenging organisms occurred at a later stage of development. Antibodies in immune sera of hamsters with a primary S. mansoni or S. haematobium infection were shown to bind to common antigens on the surface of young schistosomula of either species by u.v. microscopy using as detecting agent a fluorescein-labelled rabbit antiserum directed against hamster globulins.

Seasonal abundance of Neoechinorhynchus cylindratus taken from largemouth bass (Micropterus salmoides) in a heated reservoir.

Abstract: Samples of largemouth bass were collected from Par Pond located on the Energy Research and Development Administration's Savannah River Plant in Aiken, South Carolina, from June 1972 to May 1973 inclusive. The sampling stations reflected water temperatures which were both normal and greater than 10 degrees C above normal for the area. The acanthocephalan Neoechinorhynchus cylindratus was the dominant species found in the bass sampled. Incidences of infection for this parasite were generally greater than 95% regardless of location. A pronounced seasonal cycling pattern in the intensity of infection was noted in both thermal regions. Significant differences, however, in the mean density of N. cylindratus per host in fish taken from the heated area as compared with unheated areas were noted. Turnover in the acanthocephalan population was measured by following the percentage of individuals less than 2 mm long. Fall proved to be the most intense parasite recruitment season, followed by maturation of parasite and subsequent loss from the fish host. The principal factors responsible for the seasonal incidence and intensity patterns are considered to be changes in the fish feeding behaviour and annual temperature regimes.

Eimeria maxima: a comparison of two laboratory strains with a fresh isolate

Abstract: Oocysts of the Weybridge and Houghton strains of Eimeria maxima and a fresh field isolate were similar and measured on average 30·9 × 22·4 μm. The Weybridge strain and the field isolate produced similar pathogenic effects in 6-week-old chickens, high doses causing 50–80% mortality and severe weight loss. The Houghton strain was slightly less pathogenic and few birds died but more oocysts were produced. With each strain, a single dose gave complete immunity to a light challenge with the homologous strain. Two or 3 immunizing doses gave complete immunity to a heavy homologous challenge but were not sufficient to protect against heterologous challenge.

Schellackia landauae sp.nov. (Eimeriorina: Lankesterellidae) in the Brazilian lizard Polychrus marmoratus (Iguanidae): experimental transmission by Culex pipiens fatigans

Abstract: A new haemogregarine, Schellackia landauae sp.nov., is described in the Brazilian lizard Polychrus marmoratus (Linn) from Para State, north Brazil. Sporozoites are found principally in the red blood cells (84%) in the peripheral blood but also occur in lymphocytes and monocytes. Experimental transmission to three uninfected P. marmoratus was achieved after feeding them with laboratory-bred Culex pipiens fatigans which had engorged on an infected lizard 14 days previously. The cycle of development in the small intestine of P. marmoratus takes approximately 30 days: schizogony, gametogony and fertilization of the macrogametocytes is in the epithelial cells of the gut, with zygotes penetrating the lamina propria, where the mature oocysts develop. Living oocysts average 14·3 × 13·3 μm, and are approximately 10·0 μm as seen in histological sections. During the period of intestinal development, the parasite also undergoes asexual multiplication within cells of the spleen and liver by a process which appears to be endodyogeny. The exact time required before the first invasion of the peripheral blood by the sporozoites remains to be ascertained, but is some time within 30–45 days after the lizard ingests the infected mosquitoes. Morphology of the sporozoite in the vertebrate host is variable and depends on the host cell occupied; there may be 1 or 2 refractile bodies. Reduction or fusion of these to a single refractile body in those sporozoites within the gut cells of the infected mosquito suggests that the bodies may represent some form of energy source that is used up during this latent phase in the insect vector. Accumulation of sporozoites takes place in the reticulo-endothelial cells of the viscera, in particular the pigmentladen cells of the liver and lung. Attempts to infect other species of lizards, Tropidurus torquatus (Iguanidae) and Ameiva ameiva (Teiidae) failed.

The isolation and characterization of a Babesia from red deer (Cervus elaphus).

Abstract: On three occasions, antibody positive blood from wild red deer produced overt infections with Babesia when inoculated into splenecto-mized red deer. One of the deer also became infected with Eperythrozoon sp. Babesia divergens, B. capreoli and the Babesia of red deer are morphologically similar and the marginal position of the parasites in the host cell is characteristic. Babesia were not seen and no antibody was formed in five out of six splenectomized bovine calves which were injected with parasitaemic red deer blood. Two of these calves when challenged with B. divergens were fully susceptible. A transient infection with the deer Babesia may have occurred in the sixth calf since antibody was detected and the animal resisted challenge with B. divergens.In indirect fluorescent antibody tests there was little or no difference in the titre of sera from naturally or experimentally infected cattle and deer when reacted with B. divergens or the red deer Babesia antigens. Despite their similarities, specific status for B. divergens and the red deer Babesia is probably justified; at present there is insufficient evidence to justify separation of the red deer Babesia from B. capreoli.

A study on snail location by Fasciola hepatica using radioisotopically labelled miracidia.

Abstract: A number of common freshwater molluscs were exposed to Fasciola hepatica miracidia labelled in vivo with radioselenium. Radioactivity was rapidly incorporated in all lymnaeid species tested (L. stagnalis, L. tomentosa and L. truncatula) whereas no radioactivity could be demonstrated in non-lymnaeid pulmonate species (Aplexa hypnorum, Physa acuta, Physa fontinalis, Anisus vortex, Gyraulus albus and Planorbis planorbis) or in the prosobranchs Valvata cristata and Valvata piscinalis. However, the prosobranchs Bithynia leachii, Bithynia tentaculata and Potamopyrgus jenkinsi showed a slow but significant uptake of radioactivity which was presumably explained by uptake of labelled miracidia through a 'filter-feeding' mechanism. Sphaerium corneum, a true filter-feeder, showed a similar course of uptake of radioactivity.