Immature Parasites Research Articles

The effect of corticosteroid therapy on infection with Toxocara canis in dogs.

Three, six-month-old dogs were infected with 2,000 eggs of Toxocara canis. Three weeks after infection 15 immature adult parasites were found in the intestine of the dog which had been treated with high doses of corticosteroids (2 ml of Opticortenol S given every four days) while no parasites were found in the intestine of the dog treated with repeated injections of 0.3 ml Opticortenol S or in the untreated control dog. The increased susceptibility to infection with T. canis in the dog treated with high doses of corticosteroids was associated with a decrease in in vitro lymphocyte responsiveness to the mitogen concanavalin A and pokeweed mitogen and with a complete suppression of the eosinophilia that was seen 10 days after infection in the untreated control dog.

FACTORS AFFECTING FACULTATIVE DIAPAUSE OFMICROCTONUS VITTATAE(HYMENOPTERA: BRACONIDAE)

In Manitoba, first-stage larvae ofMicroctonus vittataeMues. overwinter in diapausing adults of two rape-infesting chrysomelids,Phyllotreta cruciferae(Goeze) andPhyllotreta striolata(F.). The parasite larvae resume their development in May after the hosts have finished overwintering, and mature parasite larvae emerge and spin cocoons from which adults emerge late in May and during June. Usually there are four parasite generations each year; most of the larvae in the first three generations are non-diapausing, whereas most first-stage larvae of the fourth generation develop briefly and then enter diapause in September or October and overwinter. Early attempts to propagateM.vittataefor laboratory studies were unsuccessful because most of the immature parasites either died or entered diapause. Preliminary tests suggested that, as in some other parasite species (Saunders 1965; McNeil and Rabb 1973; Anderson and Kaya 1974), the photoperiod at which the parasites were propagated influenced the incidence of diapause. The following three experiments examined this hypothesis and attempted to identify rearing conditions that would prevent diapause or limit its incidence inM.vittatae.

The effect of γ-irradiation on Fasciola gigantica infectivity to hamsters

The effect of Cobalt-60 irradiation at graded doses on the infectivity of Fasciola gigantica metacercariae was studied in hamsters. Since no worm was recovered from the hamster liver when the metacercaria was irradiated at doses above 4 krad, it was concluded that only irradiation beyond this level sufficiently attenuated Fasciola gigantica metacercaria enough to prevent immature parasites from getting into the liver.

Impact of a Methyl Parathion Spray Program on the Alfalfa Weevil 1 Parasite, Bathyplectes curculionis2 , in Pennsylvania 3

A 4-yr study determined the impact of methyl parathion, as commonly used against the alfalfa weevil, on the alfalfa weevil parasite Bathyplectes curculionis in Pennsylvania. The 1st generation of B. curculionis each spring coincided with the peak alfalfa weevil larval population and produced the greatest number of parasitized larvae. Each year the insecticide treatment significantly reduced the number of immature and adult parasites. The parasite-host ratio also declined relative to that in the unsprayed area. One week after spraying, each year, the numbers of immature parasites were reduced 93.2–100%. This reduction over the total period between spray and harvest ranged between 84.6 and 95.3%. In addition, the number of nonparasitized host weevil larvae also declined to near undetectable levels, consequently, reducing the oviposition potential for any adult parasites surviving in the sprayed area. The number of parasite larvae in the methyl parathion area declined significantly during the 3-yr spray program. During the 4th yr, when no spray was applied, B. curculionis larval populations increased in both the sprayed and unsprayed areas. However, the population in the sprayed area remained significantly lower than that in the unsprayed area indicating that B. curculionis populations did not fully recover following 3 yr of insecticide stress. The reduction in parasite numbers during this study was accompanied by a 9x increase in the weevil larval population. It is apparent that alfalfa weevil management schemes which do not judiciously integrate insecticide programs with B. curculionis biology can greatly reduce this parasite's potential.

Gametocyte and gamete development in Plasmodium falciparum.

The ultrastructural organization of the mature gametocytes ofPlasmo­dium falciparumisolated from the peripheral circulation of naturally in­fected Gambians is examined and compared with immature forms obtained from the peripheral circulation of a chloroquine treated patient. The latter are recognized as the stage 2 and 3 developmental forms (Hawking, Wilson & Gammage 1971Trans. R. Soc. trop. Med. Hyg. 65, 549-559) observed by light microscopy and are distinguished in the electron microscope by three characters; (i) they do not fill the host cell, (ii) they contain few, if any, osmiophilic bodies, (iii) they possess an extensive subpellicular tubule system. Maturation (capacitation) of these immature parasites takes many days and is followed by an extended period of maturity during which the gametocytes will exflagellate. Mature macro- and microgametocytes have numerous characters in common with the gametocytes of avian and reptilian Plasmodiidae, namely a tripartite pellicle, cristate mitochondria, a comparatively high density of osmiophilic bodies in the macrogametocyte, cytostomal feeding, Golgi body, and persistent nucleolus in the female gametocyte. These similarities together with the unexpected nuclear changes detected in macrogametogenesis suggest thatP. falciparumis best considered as pre-dating the ‘malariae’ and ‘vivax’ groups and not as having evolved from them. Light microscopy, scanning and transmission electron microscopy and videotape analyses of gamete formation were undertaken. Nuclei in the mature gametocytes are Feulgen negative but upon activation rapidly become Feulgen positive. The gametes also are Feulgen positive. The crescentic parasites swell to become large spherical cells and escape from the host cell by osmotic or enzymic activity. The microgametocyte undergoes three mitotic divisions during which the chromosomes are sequenti­ally reduced in number such thatca. 7 are incorporated into each gametic nucleus. The microtubule organizing centre (m. t. o. c.), which in the mature gametocyte is associated with the intranuclear body, is attached to the centriolar plaque of the first division spindle. There it differentiates into kinetosomes which act as foci for the polymerization of axonemes. The kinetosomes and axonemes remain attached to the centriolar plaques during division and are segregated synchronously with the genome at each division. Subsequently one axoneme enters each haploid gamete at exflagellation. Exflagellation is accompanied by a significant reduction in microgametocyte volume which is associated with an increase in density of the cytoplasm. The female gametocyte does not decrease in volume but undergoes nuclear changes in which a single pole of an intranuclear spindle is detected. Comparisons are made with macrogametogenesis in avian malarial parasites from which it is suggested that this spindle, if not half of a normal mitotic spindle, is an atavistic trait. The possibility of a meiotic gametic division is discussed but discounted. The activity pattern of the microgamete was found to be similar to that of other malarial parasites, with states of high and low activity or immobility. High activity, which results in rapid movement through the medium, is produced by long wavelength (12 μm), low amplitude (1.1μm) waves generated atca. 12 waves per second; low activity, which results in contorted gyrating on the spot, is produced by long wavelength (14.1), high amplitude (2.3) waves produced atca1 wave per second. Following an initial period of continuous activity the gamete usually alter­nates between high and low activity states. Subsequent low activity and immobility is in turn followed by death. Microgamete activity was pro­foundly affected by the plasma of some patients, presumably as a result of the antigametocyte antibodies present. The microgamete contains a single axoneme, at one end of which lies the kinetosome with the juxtakinetosomal sphere and granule. It is this end which emerges first from the parental gametocyte. A single nucleus is centrally located in many microgametes although 23% are anucleate.

The occurrence of Sphaerostoma bramae (Digenea: Allocreadiidae) in the roach from the Worcester-Birmingham canal.

Two hundred roach (Rutilus rutilus) were examined over a twelve-month period to provide information concerning the occurrence of Sphaerostoma bramae. Infection levels were high during the autumn and winter and at this time of year the parasite population was composed almost exclusively of immature parasites. Maturation was rapid in the spring but was accompanied by a decrease in the infection level. In late summer, after egg-laying, losses due to the death of spent parasites began to be replaced by the recruitment of immature parasites and this recruitment reached its peak in the autumn and winter. The annual cycle of occurrence and maturation is discussed in relation to fluctuating environmental variables and the feeding behavior of the roach.

Parasitism of the Scale Insect, Fiorinia externa (Homoptera: Diaspididae), by Aspidiotiphagus citrinus (Hymenoptera: Eulophidae) in a Hemlock Forest: Density Dependence

The spatial distributions of the scale insect, Fiorinia externa Ferris (Homoptera: Diaspididae) and its parasite, Aspidiotiphagus citrinus (Craw.) (Hymenoptera: Eulophidae), on Eastern hemlock, Tsuga canadensis (L.) Carr., were studied during 1976 in a mixed conifer-hardwood forest in Westport, Conn. The highest numbers of adult female scales and immature parasites occurred in the lower crown (0–4 m above ground) where 49 and 70% of the total number of each were collected, respectively. The upper crown (9–12 m) supported the least numbers (19 and 6% of the total scale and parasites, respectively). Percent parasitism of 2nd-instar females by A. citrinus was significantly correlated with the density of F. externa females on branches collected within the crown and from the lower crowns of 30 trees sampled in May and Sept. Increases from May–Sept. in percent parasitism were significantly correlated with increases in scale density over the period, indicating that A. citrinus responds density-dependently to changes in host population levels. The density-dependent response of A. citrinus to F. externa within the crown and among trees indicates the potential value of the parasite as a biological control agent of a most destructive insect pest of hemlock in parts of the northeast United States.

Plasmodium falciparum gametocytes: the effect of chloroquine on their development

Asexual erythrocytic parasites of Plasmodium falciparum are killed by chloroquine, whilst mature gametocytes are not. The gametocytes of P. falciparum take 10 days to develop to maturity and their sensitivity to chloroquine during this time was studied in vitro to investigate when the switch from susceptibility to insusceptibility occurred and to compare the responses of asexual and immature sexual parasites to the drug. 45 to 50% of asexual parasites and immature gametocytes less than one day old survived in 0.1n. mols of chloroquine per ml but 0.3n. mols of drug per ml was lethal to both. Chloroquine at 1.0n mols per ml was lethal to developing gametocytes during their first six days of growth probably due, at least in part, to the drug disorganizing the parasite's digestion of host erythrocyte haemoglobin. The drug clumped the pigment of developing gametocytes. Only immature gametocytes in the final stage of development (stage 4) survive in high chloroquine concentrations.

Suppression of malaria infection by oxidant-sensitive host erythrocytes.

DEFICIENCY of the red cell enzyme, glucose-6-phosphate dehydrogenase (G-6-PD), predisposes erythrocytes to oxidant-induced haemolysis and is thought to protect humans against severe malaria infection. We have already shown that the malaria parasite exerts an oxidant stress on infected red cells and suggested that premature lysis of malaria infected erythrocytes might occur in G-6-PD deficient humans1, thus limiting the severity of infection by enforcing the release of immature parasites incapable of propagating the infection2.

Experimental Ascaris suum infection in the pig. Population kinetics following low and high levels of primary infection in piglets

Groups of piglets 20 to 28 days of age were dosed with 50 or 10 000 Ascaris suum eggs. The pigs were sacrificed from day 16 post infection onwards and worms present in the intestine were counted. Large numbers of immature parasites were recovered initially following the 10 000 egg dose, but the numbers decreased rapidly with the and worms were not found in pigs examined in the late prepatent phase. All pigletts infected with 50 eggs were found to harbour worms and the infection reached patency. The high level infections resulted in an eosinophil response which reached maximum values during the second week after infection. The low level infections which resulted in patency were not followed by any significant eosinophil response.

Anaerobic Excretion of Fermentation Acids by Hymenolepis diminuta during Development in the Definitive Host

Succinic, acetic, and lactic acids are the major anaerobic fermentation acids excreted in vitro by Hymenolepis diminuta. In parasites recovered from immature (6-day) infections in white rats that were fed ad lib. in the dark for 12 hr, approximately equal amounts of succinic and lactic acids, and less acetic acid, were excreted. In the succeeding 12-hr period of fasting in the light, production of succinic and acetic acids from endogenous glycogen reserves was unaffected, whereas that of lactic acid decreased markedly. The pattern was different in parasites recovered from 10and 14-day infections, in that quantitative differences in acid excretion during feeding and fasting periods were not observed, lactic acid production was relatively small, and succinic acid constituted about half of the total excreted acids. An active pyruvate decarboxylase enzyme complex presumably accounted for the formation of acetate from pyruvate. The existence of lactate dehydrogenase, and a phosphoenolpyruvate carboxykinase leading to succinate production were already known. A calculation of the carbon content of excreted acids in terms of ,moles phosphoenolpyruvate carbon/mg protein showed that the rates of excretion of fermentation acids in 6and 14-day infections did not differ. Succinic, acetic, and lactic acids comprise most of the total fermentation acids excreted in vitro by Hymenolepis diminuta recovered from patent (15 day) infections in rats (Fairbairn et al., 1961). It is known that phosphoenolpyruvate is a key intermediate in the formation of these acids since it reacts with carbon dioxide in the presence of phosphoenolpyruvate carboxykinase and GDP or IDP to form oxaloacetate and thence succinic acid, and is also converted to pyruvate by pyruvate kinase (Bueding and Saz, 1968) and hence to L(+) lactate by lactate dehydrogenase (Walkey and Fairbairn, 1973). Acetic acid is presumably formed by oxidative decarboxylation of pyruvate, although the existence of this enzyme complex has not been studied. Different isoenzymes of L(+) -lactate dehydrogenase occur in the anterior regions of the mature tapeworm strobila or in immature (6 day) parasites, and in infective eggs obtained from mature proglottids (Walkey and Fairbairn, 1973). Similar observations have been made on pyruvate kinase (Carter and Fairbairn, unpublished). There is reason to believe, therefore, that quantitative differences in the forReceived for publication 11 February 1974. * This work was supported by Grants AI-08491 and 5 TOI AI-226 from the NIH, Bethesda, Maryland 20014. t Present address: The Wellcome Research Laboratories, Beckenham, Kent BR3 3BS, England. mation and excretion of succinic, acetic, and lactic acids may exist in different regions of the strobila, or in parasites at different stages of development in the definitve host. This is not surprising, as the strobila of H. diminuta contains hundreds of proglottids representing all stages of continuous growth and differentiation. In the present investigation we have compared the in vitro anaerobic excretion of succinic, acetic, and lactic acids by H. diminuta recovered from infected rats after 6 and 14 days, respectively, and have demonstrated the decarboxylation of pyruvate by a pyruvate decarboxylase enzyme complex. MATERIALS AND METHODS In order to make possible a comparison of the present experiments with other recently completed experiments (Carter and Fairbairn, unpublished), white, male Sprague-Dawley rats (Holtzman strain) weighing about 150 g each were infected with 30 cysticercoids of H. diminuta injected into the stomach through a catheter. After ensuring that all cysticercoids had been delivered from the catheter, the rats were caged in pairs and maintained on a 12 hr light-12 hr dark daily photoperiod. Food (commercial pellets) was provided only during the dark half of the cycle, from 8:00 PM to 8:00 AM. Rats harboring parasites to be recovered on the 10th or 14th day after infection were maintained in this manner. When parasites were to be recovered after infection for 6 days the procedure was the same except that greater numbers of rats were infected, each with 300 to 500 cysticercoids, in order that sufficient weight of tissue would be available for

Seasonal Sequence of Parasitism of Unaspis yanonensis : (KUWANA) (Homoptera:Diaspididae)

The seasonal sequence of parasitism of Unaspis yanonensis (KUWANA) was investigated in Kagoshima and Fukuoka prefectures in 1970-72. In Kagoshima during the first generation of the scale the parasitism by the dominant parasite, Aspidiotiphagus citrinus (CRAW), was very low but it gradually increased through the second generation and reached the maximum level of parasitism during the third generation of its host. However, parasitism by A. citrinus was again very low in the first generation of the host the following year. Such discontinuity was due to poor adaptability of this indigenous parasite to the invader. A.citrinus could not successfully overwinter in this scale, i.e., the immature parasites died within the over-wintering host during the months of January to March. But it may be able to do so in other diaspine scales such as Aonidiella aurantii (MASKELL), Aonidiella taxus LEONARDI and Quadraspidiotus perniciosus (COMSTOCK). The first generation of U. yanonensis was in the susceptible stage at a time between the first and second appearance of A. citrinus. Thus, the parasite scarcely had a chance to attack the scale. In Fukuoka the parasitism was very low throughout the year because the host scale had only two generations a year.

Diamphenethide—a new fasciolicide active against immature parasites

AbstractDiamphenethide is the result of a search for a fasciolicide effective against immature parasites. The history of its development is followed from the active but toxic 4‐tert‐butoxyacetanilide (II) through the progressively more active and less toxic 4‐allyloxyacetanilides to di‐[2‐(4‐acetamidophenoxy)ethyl] ether, diamphenethide (VII). Evidence is presented that the activity and good therapeutic index of VII depend on deacylation to (probably) the di‐amino analogue (VIII) by liver de‐acylases, which occurs in the liver parenchyma infected by the immature fluke. Structure‐activity relationships against immature Fasciola gigantica in mice show that the acetyl group is about the correct size for maximum effectiveness, that ring‐substitution is generally very unfavourable, and that central polymethylene bridges longer than ethylene lead to lower activity or greater toxicity. The effects of functionalised central chains are shown, and a selection of activities against F. hepatica in sheep is given.

The pathogenicity of Nematodirus battus in weaned and unweaned laboratory rabbits.

The dosing of rabbits with 300 000 or 500 000 larvae of Nematodirus battus produced. pathogenic effects in some rabbits similar to nematodiriasis in lambs. The clinical symptoms observed were diarrhoea, listlessness, anorexia and weight loss. Fourth-stage larvae were responsible for the onset of diarrhoea about one week after infection but immature fifth-stage worms and adult parasites may also have been pathogenic. Several of the clinically affected rabbits died, the others usually recovered during the fourth week of infection. There was no direct relationship between the occurrence of clinical symptoms and the size of the worm populations recovered at death or slaughter.Comparison of two groups of weaned and unweaned rabbits showed that suckled rabbits were less susceptible to the establishment of N. battus infections and possibly to the effects of parasitism.

The translocation of herbicide from bean (Viciafaba) to broomrape (Orobanche crenata)

SUMMARYApplication of 14C‐labelled 2,4‐D to bean plants parasitized by broomrape led to a concentration of the herbicide in the immature parasite that was up to fourteen times that in the bean root. Not all substances are translocated in this way. 22Na in sodium chloride was not moved in significant amounts away from the site of application, but sucrose was found to be translocated to the parasite.Application of 2,4‐D,2,4,5‐T, N.A.A. and D.N.P. to mature Orobanche under field conditions had little effect.2,4‐D is not considered a suitable herbicide for the control of Orobanche in bean crops because of the high sensitivity of the host of this compound. It is thought, however, that the application to the host of a systemic herbicide which becomes concentrated in the parasite to a toxic level could well be an efficient way of controlling this type of parasite.

Effect of Bacillus thuringiensis and Carbaryl on an Elm Spanworm Egg Parasite Telenomus alsophilae12

Immature stages of Telenomus alsophilae Viereck, an egg parasite of the elm span worm, Ennomos subsignarius (Hubner), were unaffected by field application of Bacillus thuringiensis Berliner and carbaryl in early June. Immature parasites were killed when the host’s eggs were dipped in 0.2 lb/gal of carbaryl 7 days before adult emergence.

Serum enzyme alteration of mice exposed to schistosomiasis mansoni

1. 1. Serum lactate dehydrogenase, malate dehydrogenase, sorbitol dehydrogenase, isocitrate dehydrogenase, and glutamate-pyruvate transaminase activity were studied in mice after infection with 200 or 2500 Schistosoma mansoni cercariae. 2. 2. Significant alterations were observed in all enzymes studied in the sera of infected mice. 3. 3. A significant, transient increase in the serum levels of all enzymes studied was observed during the third or fourth week after cercarial exposure, the time at which immature parasites were migrating through the lung, heart, and liver. Mice exposed to 2500 cercariae died at this stage. Mice exposed to only 200 cercariae died during the eighth week, the time of final maturation of the schistosomes in the mesenteric veins of the host and egg deposition in the liver. This stage was characterized by a second increase in the serum levels of all enzymes studied. 4. 4. No significant changes were observed in the serum levels of albumin, total protein, or bilirubin during the course of these studies.

Pathological effects of oxyuriasis in the laboratory mouse.

In mice with oxyuriasis a slight inflammatory reaction occurs in the colonic mucosa. Adult Aspicularis tetraptera can penetrate the colon, thus causing inflammation and a granulomatous reaction in and outside the intestinal wall. Immature parasites can occur in the colonic glands and in the propria mucosa.

Studies on Emetine, an ‘Acute’ Fasciolicide

Emetine hydrochloride is an effective ‘acute’ fasciolicide when administered to mice, rats and sheep infected with Fasciola hepatica. Analogues of emetine arc less active (tested in mice). The drug is effective against the immature parasites in the liver tissue, but not against the immature and adult parasites in the bile ducts. In a small experiment in sheep, removal of the‘immature’ liver tissue fluke with emetine hydrochloride terminated the parasite eosinophilia and anaemia and inhibited the development of liver damage.

Antigens of Plasmodium Gallinaceum

SummaryExplasmodial antigens of Plasmodium gallinaceum were analyzed electrophoretically and found to consist of two fractions. Fluorescein-labeled antibody against explasmodial antigen was used to stain erythrocytes from chickens acutely infected with P. gallinaceum. In erythrocytes containing immature parasites, fluorescence was confined to the parasites only, whereas in erythrocytes containing mature schizonts, diffuse fluorescence of the entire erythrocyte was observed. The FA reaction was prevented by treatment of erythrocytes with nonconjugated anti-explasmodial globulin before treatment with conjugated globulin.In vitro exposure of erythrocytes from chickens acutely infected with P. gallinaceum to hyperimmune explasmodial serum resulted in agglutination and lysis of infected erythrocytes, which resulted in liberation of the parasite. Inoculation of freed parasites in susceptible chickens resulted in P. gallinaceum infection.Antibody to explasmodial antigen enhanced in vitro phagocytosis of normal chicken erythrocytes by mouse reticuloendothelial cells. Indirect evidence of similar in vivo activity of this antibody was also obtained.