Showing papers in "Parasitology in 1972"

Protein composition and protein synthesis in the surface membranes of Schistosoma mansoni

Abstract: Saponin treatment of cercariae and schistosomula alters the surface membrane so that it may be sheared from the organism and isolated as fragments by centrifugation. Saponin-calcium chloride treatment or freezing and thawing of adult worms removes the surface membrane, which can be washed from the bodies and collected by centrifugation. The small quantities of material available necessitated the development of a sensitive technique for detecting the proteins in the membranes. The surface membranes were radioiodinated after butan-1-ol extraction and electrophoresed in polyacrylamide gel. Adult surfaces prepared by the saponin-calcium chloride and by the freezing and thawing technique had identical protein components, detected as gel-cut profiles or in autoradiographs. The quantity of a rapidly migrating PAS-positive amido black negative component was greater in the surfaces prepared by saponincalcium chloride than in the frozen and thawed surfaces. This component contains lipid, some of which may be glycolipid. It was largely absent from the surface membranes of cercariae and schistosomula. Cercarial surface membranes contained a major protein component which was absent from the surface membranes of schistosomula. Otherwise the surface membranes of the cercariae were identical to those of the schistosomula in their protein components. The rate of incorporation of freshly synthesized protein per unit area of surface membrane of schistosomula was very low in the first 5 days in culture, after which there was a very rapid increase to a maximum rate on the 15th day. After this time, the rate of protein synthesis decreased to a low level at 26 days. In these studies the activity per unit area was measured and this would not be expected to vary greatly during growth. The biological significance of the observed variation in protein incorporation into the membrane is unclear.

Life cycle of a new echinostome from Egypt, Echinostoma liei sp.nov. (Trematoda: Echinostomatidae).

Abstract: A 37-spined Egyptian echinostome, Echinostoma liei sp.nov., is described in adult and larval stages. The parasite develops readily in the laboratory in chicks and ducklings, hamsters and rats. Its natural final host in or near irrigation ditches of the Nile delta involves the roof rat, Egyptian giant shrew and aquatic bird hosts. Developmental forms are described from infection of the NIH strain of Biomphalaria glabrata in the laboratory. B. alexandrina, is infected in the normal habitat in Egypt and contains both developmental stages in the heart or aorta and the hepatopancreas, and metacercariae encyst in the pericardium and kidney. E. liei sp.nov. is one of six very similar species characterized by 37 collar spines with a pattern of (3 + 2) corner spines in each lappet, six laterals on each side, and 15 dorsals in alternating rows; two pairs of dorsoventral and one small pair of ventro-lateral finfolds on the cercarial tail; and rodlike cystogenous material filling the cercarial encystation glands. In addition to distinctive intermediate-host specificity, differentiating characteristics of E. liei cercariae include presence of six sets of three flame cells each per side (total 36), seven oesophageal cells, eight penetration gland outlets on the dorsal lip of the oral sucker, and an absence of paraoesophageal gland cells as determined by intravital dyes. Significance of these and other cercarial traits is emphasized to aid in defining highly similar, but none the less distinct, sibling species.

The development of Hymenolepis diminuta in primary and secondary infections in mice.

Abstract: Over 90% of Hymenolepis diminuta cysts administered by stomach tube become established in CFLP, and Porton strains of mice. The rate of growth of single worm infections in terms of dry weight and length was determined. The rate of growth of H. diminuta in mice is slower than in rats even in worms only a few mm long. In most mice growth ceases abruptly on day 10±1 day when the worm is 4–30 cm long, destrobilation usually occurs leaving a scolex and neck often 0·5–2 mm in length. Destrobilated worms can survive for at least 47 days but little if any regrowth occurs unless the worms are surgically transplanted into rats or previously uninfected mice. Normal growth appears to be resumed within hours in both recipient hosts. The cause of destrobilation is probably not physiological; position of establishment and forward migration during growth of the worm in mice is similar to that in a rat. Destrobilation occurs well before the worm fills the small intestine lengthwise. Strong evidence of an immunological response being involved is given by the fate of a secondary infection given 22 and 28 days after the primary. Lower % recoveries were recorded in secondary infections killed 6–9 days later, and the worms were severely stunted. The various lines of evidence are discussed and it is concluded no reasonable doubt exists that H. diminuta is rejected by CFLP and Porton mice as a result of an immunological response.

Observations on the free-living stages of strongylid nematodes of the horse.

Abstract: Observations have been made on the development and survival of the free-living stages in faeces deposited out of doors at different times of year, and on the migration of infective larvae to the surrounding herbage. Laboratory experiments were performed to assist in the interpretation of the field observations. Studies were made on the rate of development to the infective stage in faeces kept at different temperatures. The rates at which eggs and larvae of Strongylus vulgaris, S edentatus, S. equinus and Trichonema nassatum developed on faecal-agar cultures at different temperatures were compared. Studies were also made on the effect of desiccation of faeces on the development and survival of the free-living stages. The results of these observations are discussed in relation to the development of herbage infestations on British pastures.

Ecological studies of larval ticks in South Africa (Acarina: Ixodidae).

Abstract: The distribution of larval ticks in relation to vegetation cover was studied on two coastal farms in the Port Alfred district of the Cape Province. The following five species were found: Boophilus decoloratus (Koch), Amblyomma hebraeum Koch, Ixodes pilosus Koch, Haemaphysalis silacea Robinson and Rhipicephalus evertsi Neumann. B. decoloratus predominated in short protected vegetation, I. pilosus and H. silacea in short covered vegetation and A. hebraeum in medium-to-tall protected vegetation. R. evertsi was collected in too small numbers to allow any correlation to be established. Both I. pilosus and H. silacea demonstrated activity peaks during the winter months. Microclimatic measurements indicated that larval ticks were not usually collected in microhabitats which experienced midday saturation deficits in excess of approximately 10 mm Hg. Behavioural studies on larval ticks climbing glass rods demonstrated the possible association of larvae with a definite vegetation height. The optimal vegetation heights were correlated with field data. The water balance of some tick species was studied and it was found that at 26 °C a relative humidity of 70% or more (i.e. above 7·53 mm Hg saturation deficit) was required by these larvae. Larvae lost water to the atmosphere at humidities lower than this value and took up water vapour from the atmosphere at values higher than 70% R.H. They were shown to be able to imbibe water through the mouthparts, and this possibly has survival value.

Ultrastructural studies on microfilariae (Nematoda: Filarioidea).

Abstract: The ultrastructural morphology of selected microfilariae from four genera is described and compared. 1. The sheath is composed of a thick layer of material not limited by membranes. 2. The cuticle is composed of a trilaminate membrane, a dense cortical layer and an inner fibrous layer. The outer leaflet of the trilaminate membrane is covered with a dense surface layer. 3. The hypodermis is formed of four components, and the outer membrane of each component is castellated. 4. Muscle cells are located in the four quadrants of the worm; each cell is divided into a contractile and a non-contractile region. Anterior muscle cells are probably involved in the movement of the hook. 5. A buccal capsule is situated at the anterior tip of the microfilaria; it is connected to the pharyngeal thead. The thread is already surrounded by the future oesophageal cells. It is not yet known whether these structures are functional in the microfilaria. 6. Three kinds of sensory organelle have been identified; they all contain modified cilia. The hook is associated with one of the amphids. 7. The excretory vesicle opens through a pore in the cuticle and is surrounded at its base by an elongate cell. The apparatus may possibly have an excretory, secretory or osmoregulatory function. 8. The inner body is composed of dense, granular material; it is already surrounded by the future intestinal cells. The inner body is thought to represent some kind of reserve material. 9. Apart from its size the G1 cell shows no unusual characteristics. 10. The anal vesicle opens through a pore in the cuticle and is surrounded at its base by the three R cells. The anal apparatus may be instrumental in the removal of waste materials, or it may be involved in some secretory activity.

Duration of immunity to East Coast fever (Theileria parva infection of cattle).

Abstract: Forty-five cattle, which had recovered from EOF and been kept free from reexposure to infection for periods of 1–43 months, were given a single uniform lethal challenge using a stabilate prepared from triturated infected ticks. All withstood the challenge which killed the five controls. There was an increase in the incidence of mild febrile reactions with time since last exposure to T. parva, indicating a gradual loss of immunity in the absence of reinfection. The duration of the immunity was not related to the severity of the initial reaction.We are indebted to our colleagues on the Immunological Research on Tickborne Cattle Diseases and Tick Control Project, with whom we designed and carried out the experiment.

Culture of Plasmodium falciparum in vitro: a subculture technique used for demonstrating antiplasmodial activity in serum from some Gambians, resident in an endemic malarious area.

Abstract: A technique is described for obtaining consistent reinvasion and multiplication of the erythrocytic stages of Plasmodium falciparum from humans in vitro. Subsequent to this, P. falciparum was subcultured through almost three cycles in vitro, during which multiplication of the parasite was obtained in the first but maintenance or only slight increase in numbers was obtained in the second subculture. The effect of sera from adult Gambians on the reinvasion of P. falciparum was measured in vitro both morphologically and by the incorporation of [14C]isoleucine into parasite protein and by the incorporation of [3H]adenosine into parasite DNA and RNA. Two sera reduced the amount of reinvasion.

The ecology of the free-living stages of Ostertagia circumcincta

Abstract: The development and survival of the eggs and larvae of O. circumcincta was studied by spreading the daily faecal output of a sheep over a 2 m square grass plot for 1 week. Observations were carried out for 3 years on material spread at 4-weekly intervals and broadly similar results were obtained in each year. Development time was long in eggs placed outside in January, February, March, November and December. Yields of larvae were small and all were dead within 5 months. During the rest of the year development time was about 2 weeks, yields of larvae were high and larvae survived until July or August of the following year. The significance of these findings in devising systems of grazing management to control parasitic gastroenteritis is discussed.

Trypanosoma (Schizotrypanum) dionisii of pipistrellus pipistrellus (chiroptera): intra- and extracellular development in vitro.

Abstract: A trypanosome identified as Trypanosoma (Schizotrypanum) dionisii Bettencourt & Franca, 1905, has been isolated from Pipistrellus pipistrellus (Chiroptera) in England. At least five out of eight P. pipistrelhis were infected. 2. In the blood of P. pipistrelhis, the parasite closely resembled T. (S.) cruzi. When grown in vitro in monophasic or diphasic media at 28°C, epimastigotes and trypomastigotes developed. The latter were of two types — very long, thin forms and less numerous shorter individuals. 3. The trypanosomes multiplied as amastigotes within HeLa and mouse L cells in vitro. After 6–9 days in HeLa cells at 37°C, they transformed into small trypomastigotes and emerged from the cells. Higher infection rates (up to about 4%) were obtained in cell cultures inoculated with flagellates from older monophasic cultures, which contained more of the long, slender trypomastigotes. 4. Trypanosomes also entered (or were phagocytosed by) up to 60% or more of mouse peritoneal macrophages in vitro. Multiplication occurred by binary and multiple fission of amastigotes in at least some of the parasitized macrophages and transformation into trypomastigotes was seen after 7 or more days at 37°C. Development in macrophages was less synchronous than in HeLa cells.

The effects of Fasciola hepatica on Lymnaea truncatula.

Abstract: Among the functional changes observed in L. truncatula infected with F. hepatica were those of growth, reproduction and mortality. For the first 3 weeks after infection there was no difference between the growth of infected and uninfected groups of snails. Thereafter there was a temporary accelerated growth which occurred between the fourth and seventh weeks after infection. The onset of this period of rapid growth in the different age groups of infected snails coincided with the time of migration of the rediae into the hepatopancreas. Of more significance was the influence of infection on the reproduction of the snail. There was a sharp decline in oviposition 2–3 weeks after infection, followed by a complete cessation of egg production at the end of the fifth week. Once oviposition ceased, it was not resumed and there was no self-cure. Contrary to general belief, infected groups of L. truncatula have been found to live longer than the uninfected controls. With isolated snails, however, there was a tendency for the uninfected snails to live longer than the infected ones. The possible interpretation of the discrepancies between isolated and mass cultured snails are discussed. The hepatopancreas and the gonad (ovotestis) were the two structures directly affected by the infection. Establishment of the rediae in the hepatopancreas invariably resulted in parasitic castration.

The development of single infections of Nematodirus battus in lambs.

Abstract: The course of single infections of Nematodirus battus was studied and the developmental phases of the fourth larval stage described. The third moult occurred between days 2 and 4 after infection and the fifth between days 8 and 10. The period of maximum larval penetration of the intestinal mucosa occurred around day 4 and most of the larvae had returned to the mucosal surface by day 6, during the middle of the fourth-stage. Some larvae remained deep in the mucosa and moulted to the fifth-stage in this site.The relationship between growth and morphological development was not constant and was different in worm populations from different sites. Some larvae grew very rapidly during the early fourth-stage and then entered a period of lethargus while continuing to develop sexually, while others grew and developed throughout the larval stage.The worms recovered from the second 30% of the small intestine were consistently smaller and less advanced morphologically than those from the first 30%. The worms in the posterior region of the small intestine were preferentially lost from the mucosa in the third- and fourth-stages between days 2 and 4 and from the mucosal surface as adults between days 12 and 16.

Trypanosoma cruzi--milk transmission of infection and immunity from mother to young.

Abstract: Trypanosomes are consistently present in the milk of lactating mice with primary phase T. cruzi infections (Peru strain). The infection is transmitted to the young, although rarely, mainly due to the difficulty of establishing infection via the oral route. Lactating females which had recovered from the primary phase of T. cruzi infection consistently transferred antibody to their young during suckling. The antibody in the serum of the young and milk of the mother was detectable by the indirect fluorescent antibody technique. In the case of the Peru strain the presence of antibody transferred to the young in this way correlated with very good protection against T. cruzi. Antibody transferred to the young was no longer detectable 6 weeks after birth. The indirect fluorescent antibody technique using bloodform antigen proved specific and highly sensitive throughout, giving prolonged and comparably high titres in mice infected with chronic and acute strains of T. cruzi.

The ultrastructure of the parasite-host interface of three tetraphyllidean tapeworms of the elasmobranch Raja naevus.

Abstract: Ultrastructural examination of the parasite-host interface of three tetraphyllidean cestodes of Raja naevus (sectioned attached to the intestine) indicates that while the strobilar tegument of each closely follows the typical cestode pattern that of the bothridia has several modifications probably associated with attachment. Microtriches similar to those of the strobilum are absent, although small spines on Echeneibothrium sp. and Phyllobothrium piriei and wart-like structures on Acanthobothrium quadripartitum bothridia are considered to represent the osmiophilic tips of specialized microtriches. The bothridia of the three species have no apparent function in the absorption of food but evidence suggests that the apical pad of the myzorhynchus of Echeneibothrium is specialized for the uptake of nutrients directly from the submucosa of the host intestine to which it is applied. Attachment and sensory roles by the myzorhynchus are also indicated. Echeneibothrium and P. piriei bothridia severely damage the host mucosal surface, while those of A. quadripartitum do little harm. This difference is probably associated with the size, mobility and mode of attachment of the cestodes. There are indications that the bothridia of Echeneibothrium upset the metabolism of mucosal cells in the attachment region. The tips of the strobilar microtriches of A. quadripartitum are shown to function in the attachment of the strobilum to the host mucosa, and in the protection of the microthrix proximal surfaces by a filtering action.

Effects of variations in temperature on infective larvae and their relationship to inhibited development of Obeliscoides cuniculi in rabbit.

Abstract: The relationship between changes in the temperature of storage of infective O. cuniculi larvae and the proportion that become inhibited in a subsequentinfection was studied. Prolonged storage at 5°C resulted in an initial inhibitionfollowed by acclimation to this temperature and subsequent normal developmentin the host. After acclimation to low temperature raising the temperature ofstorage produced no appreciable increase in the proportion of worms inhibited atthe early 4th stage. Maintenance of infective larvae at 15°C followed by a suddendecrease in storage temperature to 5°C resulted in rapid onset of inhibition. This inhibition was not reversed even after 25 days at the lower temperature. These temperature variations and the consequent pattern of arrested development werecompared to seasonal changes of spring and autumn occurring to nematode larvaeon pasture. An increase in the number of larvae given from 5000 to 15000 perrabbit had a slightly significant effect upon the proportion that remained inhibited. The need for careful assessment of the methods used for determining the extentof such inhibition is discussed.

Characteristics of parasite populations in endemic trichostrongylidosis.

Abstract: Worm counts, faecal egg counts and erythrocyte losses are recorded for lambs which were exposed on a naturally infected pasture for different periods in different years. After each exposure period the lambs were kept under conditions in which no further infection could occur; at varying times, usually after the infections had had time to maturo, the lambs were killed and examined. A detailed analysis of the results is given. It is concluded that the negative binomial distribution of worms among sheep within a flock is not a reflexion of the pasture distribution of infective stages but is the result of a combination of Poisson distributions, these distributions being generated by genetic subsets within the flock. There is a remarkable correlation between the numbers of Haemonchus present and the numbers of worms of the other genera. It is suggested that there are host-mediated common elements in the biomass regulating parameters of mixed trichostrongyle infections and that there is a resource-allocating device. Three main hypotheses are proposed. The hypotheses are: (1) The dimensional constraints on the host-parasite system are the results of various kinds of pace-setters or biological clocks. In each annual cycle the parent worms programme the rate of development through each generation. (2) The rate of development of the worms is tied stochastically or deterministically to the rate of senescence and death. (3) The rate of development and death for each trichostrongyle is set at the start of each season by a host factor which acts on a comparable area of the genome in each trichostrongyle. Methods of testing these hypotheses are discussed and the work related to other systems.

An analysis of the course of infection of Moniliformis dubius (Acanthocephala) in rats

Abstract: An analysis of the course of infection of mixed oral infections of 12 cystacanths of Moniliformis dubius in 174 male and 179 female Wistar rats has been undertaken. There was a marked decline in the average recovery rate of worms of both sexes from hosts of both sexes during the course of the infection. Female worms from both male and female rats showed, on average, a greater power of survival than male worms from the third period (10–13 weeks) onwards. Male rats were found to retain, on average, a greater number of worms of both sexes than female rats. We wish to thank Miss Susan Arnold and Mr David Barnard for excellent technical help.

The output of cercariae of Fasciola hepatica by Lymnaea truncatula and the distribution of metacercariae on grass

Abstract: It has been demonstrated that under normal laboratory conditions Lymnaea truncatula infected with Fasciola hepatica are not able to shed all their cercarial loads before their death. Cercariae are irregularly released over an extended period and considerable variations (4–1789) occur in their output.Laboratory studies have revealed that the green parts of grass (Dactylis glomerata) are preferred to the brown, dead parts by the cercariae of Fasciola hepatica for metacercariae formation. More cysts are formed on the lower surface of submerged leaves than on the upper surface.There is vertical zonation of metacercariae on grass in water. More cysts occur on the upper parts of submerged grass than on the lower parts.Vertical migration of cercariae after settling does not usually occur before cyst formation.The results are tabulated and discussed and correlated with conditio s in the field.This work was undertaken in the Department of Zoology, University of Bristol, Bristol, under the supervision of Dr H. D. Crofton, to whom I wish to express my gratitude.

Babesia pantherae sp.nov., a piroplasm of the leopard (Panthera pardus).

Abstract: A large Babesia species was found in a leopard (Panthera pardus) in Kenya. It was established in domestic cats but no other animal was found to be susceptible. The parasite has been compared with other piroplasms of felids and it was found to differ from them in some significant characters. It was established as a new species and named Babesia pantherae.We would like to thank Miss B. O. Vidler for her assistance, Dr S. F. Barnett for many helpful discussions and Professor N. D. Levine for pointing out the need for this description.The parasite was isolated when we were working at the East African Veterinary Research Organization at Muguga in Kenya and we are most grateful to that organization for facilities.