Previous studies of mating interactions between schistosome species from different evolutionary lineages in mice showed that mating is not random: heterospecific pairs form but, given the choice, the preference is for homospecific partners. Mating competition and change of mate were also demonstrated. Schistosoma mansoni is a medically important parasite of humans belonging to a different evolutionary group from S. margrebowiei, a parasite of bovines of veterinary importance. Experiments were designed to investigate the mating behaviour of these two species in mice. Analysis of the data showed a preponderance of intraspecific pairs over interspecific, demonstrating a specific mate preference system for both species. The existence of mating competition between these species was indicated. Males of both species were able to actively compete for paired females by pulling them away from their partners, thus effecting a change of mate. Overall, neither species appeared to be competitively dominant to the other, and the data suggest that where this is the case in sequential infections, the most successful species in terms of worm return and ability to form pairs will be the first species to infect the host.

1. T. axei eggs in sheep faeces hatch at a temperature of 38° C. and a relative atmospheric humidity of 29%, but all of the larvae are dead 96 hr. after the initiation of the exposure. Eggs kept in faeces at −7° C. are killed within 96 hr.

2. Eggs do not hatch while under water but remain viable for 20 days under 15 mm. of water at temperatures ranging from 11 to 28° C. Under natural conditions the longevity would in all probability be influenced by such factors as depth of water, amount of decomposing organic debris, etc., which determine the amount of available oxygen present.

3. Completely embryonated eggs in sheep faeces possess a high resistance to drying. It is apparent that ranges and pastures in California cannot be freed of eggs by keeping suitable hosts off them during a single dry season, because the eggs can survive desiccation for a period exceeding the dry season. It is possible, however, that if the eggs were directly exposed to the rays of the sun they might be killed.

4. The non-infective larvae of T. axei are very much less resistant to desiccation than are the eggs. The population of non-infective larvae would, however, under the more common natural conditions, normally attain the infective stage before succumbing to desiccation.

5. Infective larvae lived for more than 104 days at a temperature of 38° C. and a relative atmospheric humidity of 29%. At −7° C. they were alive at the end of 25 days but were dead on the thirty-ninth day. It is believed that under natural conditions such larvae would not be exterminated by high temperatures. At low temperatures the usual covering of snow might sufficiently protective to prevent death.

6. T. axei infective larvae survived 230 days' submergence in 5 mm. of water at room temperature in diffused daylight. Direct sunlight appears have some lethal effect. The amount of oxygen available in the water appears to determine to a considerable degree the longevity of the larvae. Under natural conditions infective larvae can survive even greatly prolonged flooding.

7. The survival of infective larvae to desiccation is dependent upon the actual degree of dryness attained. Larvae dried on glass slides at room temperature ranging from 17 to 27° C. with a relative atmospheric humidity of from 35 to 51% survived up to 16 days after the initiation of exposure.

8. Different investigators have obtained different results in studying the longevity of infective larvae in soil. The writers believe that the infective larvae do not spend much time on soil or migrate through it unless to escape some unfavourable environmental factor such as particularly high or low temperatures or desiccation, or unless they are accidentally washed into it during heavy rainfall.

9. No evidence of phototropic behaviour was observed. It is believed that vertical migration up vegetation is caused by a negatively geotropic reaction which may be conditioned or altered at times by stronger external stimuli resulting from extreme temperatures, bright sunlight, low atmospheric humidity, etc.

10. It is believed that the seasonal incidence of trichostrongylosis on irrigated ladino clover pastures in California is determined by acquired resistance, age resistance, or both.

11. A mixture of a 1% solution of 40% nicotine sulphate and 1% copper sulphate appears to be a more efficient anthelmintic against T. axei than a straight 1% copper sulphate solution. Changing from green feed to hay or rendering hay available along with green feed may possibly have a therapeutic effect. Spontaneous recovery, so far as clinical symptoms are concerned, from an acute trichostrongylosis, without the administration of a drug or changing the diet, seems to be common, if not the rule, in the majority of lambs in an infected band.

1. Studies have been made of carbohydrate metabolism in Fasciola gigantica during starvation and these are compared with data available about carbohydrate metabolism in F. hepatica.

2. In F. gigantica the glycogen content before starvation was 5·4% of f.w. or 25·35% of D.W. of tissue, and the glycogen content after starvation was 3·5% of F.W. or 16·29% of D.W. of tissue.

3. The medium in which F. gigantica was incubated was analysed for lactic acid as one of the end products of glycogen consumption. The lactic acid given out in a period of 2 hr. was 0·46% of F.W. or 2·18% of D.W. of tissue.

I wish to thank Professor K. Sahai for his generous help in the preparation of this manuscript.

Many medically important diseases of man are caused by blood-sucking arthropods which serve as vectors for a wide range of viral, bacterial, protozoal and nematode infections (Table 1). Furthermore, serious economic losses are caused by the numerous arthropod parasites which infect domesticated animals (for examples, see Table 2). Among these the ixodid hard ticks are particularly important and it has been estimated that the global cost of hard tick infections is $7000 million per annum (F.A.O., 1984). Not surprisingly, there have been strenuous efforts to control infections caused by arthropods.

Our study aimed at examining the phylogenetic position of the newly-found Setaria nematodes obtained from the red deer (Cervus elaphus) based on sequences of the mitochondrial cytochrome c oxidase subunit 1 (COX-1). Alignment and phylogenetic analyses, as well as SEM microscopic analysis, revealed the presence of two Setaria species: S. cervi and S. tundra. Setaria tundra was noted in only one individual, a calf of the red deer, while S. cervi was observed in three stages, two hinds and one calf of the red deer. According to our knowledge, it is the first case of S. cervi in the red deer in Poland confirmed in molecular studies and also the first case of S. tundra infection in the red deer.

An analysis of natural infections of Toxocara mackerrasae in Rattus fuscipes trapped in rain forests in south-eastern Queensland is given and Hydromys chrysogaster is listed as a new host.

T. mackerrasae larvae in egg-infected mice are incapable of somatic migration but some complete development to the young adult stage can occur entirely within the alimentary tract. T. mackerrasae is capable, in low numbers, of developing to maturity in experimentally infected Rattus spp.

The work was financed by grants from the University of Queensland and the National Health and Medical Research Council of Australia. I wish to thank Professor J. F. A. Sprent for his criticisms and suggestions during the preparation of this text.

Individual animals are often infected not only by different parasite species, but also by multiple genotypes of the same parasite species. Genetic relatedness among parasites sharing a host is expected to modulate their strategies of resource exploitation, growth and virulence. We experimentally examined the effects that genetic diversity and infection intensity had on host mortality, infectivity and growth of the marine trematode Maritrema novaezealandensis in amphipod hosts. The presence of 2 versus 1 parasite genotype during infection did not influence subsequent host mortality, had different effects on infectivity among genotypes and did not influence growth or variation in parasite growth. Density-dependent growth reductions revealed that the number of parasites infecting a host was more important than their genetic relatedness. Temperature, host size, and host sex influenced the degree to which density-dependent factors affected parasite growth. Our results suggest that the effects of parasite relatedness vary among parasite genotypes in this trematode species, and reveal that many factors play an important role during parasite development and transmission.

The kinetoplast DNA (kDNA) of kinetoplastidae was the first mitochondrial DNA (mtDNA) to be discovered, and with its unusual network structure, consisting of more than 104 catenated DNA circles, it is without equal in nature. Analysis of networks from various genera (reviewed by Borst & Hoeijmakers (1979a) and Englund (1980)) has shown that they always consist of two components: mini-circles and maxi-circles (see Table 1). The mini-circles are the major component and deterraine the size and sliape of networks. They vary in size between 1 and 3 kilo-base pairs (kb = 1000 base pairs (bp)), they are heterogeneous in sequence, their sequence evolves rapidly and their function is not yet known. The maxi-circles, on the other hand, are homogeneous in sequence, their sequence is conserved and they probably represent the counterpart of mtDNA in other organisms.

Ten larval Cestodes, eight from aquatic and two from terrestrial hosts, have been described. Of these, eight species are new, and in the case of Cysticercus “A,” both larva and adult are new. By direct animal experiment the life-histories of three forms have been definitely established, while by careful comparison of the hooks of the scolex two larvae have been related to known adults. Cysticercus Hymenolepidis setigerae, previously recorded only from Copepods, is described here from an Ostracod host.

Effect of the parasite on the host. It is difficult to estimate the effect of Cestode larvae parasitic in Invertebrata, especially in the smaller forms such as the Entomostraca. In the latter, I have found that the intestine and musculature suffer most, and that the reproductive organs remain unattacked. The same remarks also hold for Oligochaete hosts. Dady (1901) considers that the influence of these cystic stages on their hosts is considerable, particularly on the musculature, sexual organs and intestine, and that death of the host may follow. Lindner (1921) states that little or no harm is done to Ostracods by the presence of tapeworm larvae, and also that the ovary of the female remains unattacked. The same author considers that, among the Entomostraca, destruction of the intestine occurs only in Copepods, the body cavity of Ostracods being so roomy that a harming of the intestine by growth of the parasite is unlikely. Schmidt (1894) finds that for Cysticercus Hymenolepidis anatinae, the host, Cypris ovata, was not particularly affected.

Chagas disease is a serious parasitic infection caused by Trypanosoma cruzi. Unfortunately, the current chemotherapeutic tools are not enough to combat the infection. The aim of this study was to evaluate the trypanocidal activity of benznidazole-loaded microparticles during the acute phase of Chagas infection in an experimental murine model. Microparticles were prepared by spray-drying using copolymers derived from esters of acrylic and methacrylic acids as carriers. Dissolution efficiency of the formulations was up to 3.80-fold greater than that of raw benznidazole. Stability assay showed no significant difference (P > 0.05) in the loading capacity of microparticles for 3 years. Cell cultures showed no visible morphological changes or destabilization of the cell membrane nor haemolysis was observed in defibrinated human blood after microparticles treatment. Mice with acute lethal infection survived 100% after 30 days of treatment with benznidazole microparticles (50 mg kg−1 day−1). Furthermore, no detectable parasite load measured by quantitative polymerase chain reaction and lower levels of T. cruzi-specific antibodies by enzyme-linked immunosorbent assay were found in those mice. A significant decrease in the inflammation of heart tissue after treatment with these microparticles was observed, in comparison with the inflammatory damage observed in both infected mice treated with raw benznidazole and untreated infected mice. Therefore, these polymeric formulations are an attractive approach to treat Chagas disease.

A n.gen. and n.sp. of a yeast-like micro-organism—Adlerocystis ornithodori—is described. This micro-organism is probably a symbiote of sperm cells of Ornithodoros tholozani. Another species, A. parkeri n.sp., is found in O. parkeri.

Adlerocystis sp. were also found in O. coriaceus, O. nicollei, O. erraticus, and O. savignyi.

The earliest stage of development of A. ornithodori was observed in the posterior lobe of the complex of accessory genital glands of the male, where it has the shape of a round cell. It is spindle-shaped when attached to the mature sperm in the spermatophore.

The development of A. ornithodori from a round cell to an elongated spindle-shaped organism, in vitro in the spermatophore, as well as in vitro, is described.

We wish to thank Dr W. Burgdorfer, the Rocky Mountain Laboratory, Mr R. Garcia, University of California, and Mr A. Avivi, the Israeli Institute of Biology, who provided ticks, as well as Mr E. B. Kennedy for taking the microphotographs and Mr N. Shultan from the Elyahu and Rosa Wunsch Electron Microscopy Laboratory for the electron micrograph, both from the Hebrew University Hadassah Medical School, Jerusalem.

Syngamus trachea, the gape nematode, has been used as a model to study the chemosensory function of amphids. Extracellular electrophysiological recordings were performed directly on amphids. The amphids were stimulated by blood serum from a host bird and by D-tryptophan. The spike frequency produced by the amphid increased significantly after the application of the serum and the application of D-tryptophan. Two types of amphidial neurones responded to the presence of the stimuli. These extracellular recordings have verified the chemosensory function of the amphids.

The egg-shell of Hammerschmidtiella diesingi and Aspiculuris tetraptera reduces the rate of water loss from the egg when exposed to desiccation. Staining of the enclosed larva by acid fuchsin and the collapse of eggs exposed to desiccation indicate that the permeability barrier is heat labile. This suggests that the lipid layer is the main permeability barrie of the shell. The complex structure of the uterine layers has a similar morphology to the respiratory structures of the chorion of some insect eggs. Reflections from the shell, the rate of embryonic development under various conditions and the penetration of lead ions indicate that the shell does not trap a layer of air when immersed in water and the uterine layers cannot, therefore, function as a plastron network. Calculations indicate that if diffusion is limited to the pores in the external uterine layer, the area available for gaseous exchange is reduced by 85·5% in H. diesingi, 95·6% in A. tetraptera and 96·8% in Syphacia obvelata. It is suggested that the uterine layers of oxyurid egg-shells function in a similar fashion to the pores in bird egg-shells and the aeropyles in the chorion of insect egg-shells which do not possess plastron networks. These structures reduce water loss from the egg whilst ensuring an adequate supply of oxygen for embryonic development.

Echinococcus granulosus is an important zoonotic parasite that is distributed worldwide. The EG95 vaccine was developed to assist with control of E. granulosus transmission through the parasite's livestock intermediate hosts. The vaccine is based on a recombinant antigen encoded by a gene which is a member of a multi-gene family. With the recent availability of two E. granulosus draft genomes, we sought to map the eg95 gene family to the genomes. We were unable to map unequivocally any of the eg95 gene family members which had previously been characterized by cloning and sequencing both strands of genomic DNA fragments. Our inability to map EG95-related genes to the genomes has revealed limitations in the assembled sequence data when utilized for gene family analyses. This study contrasts with the expectations expressed in often high-profile publications describing draft genomes of parasitic organisms, highlighting deficiencies in currently available genomic resources for E. granulosus and provides a cautionary note for research which seeks to utilize these genome datasets.

A preparation highly enriched in tegument membranes from adult worms has been used to probe rodent responses to schistosome surface antigens. All exposure regimes in mice stimulated levels of anti-tegument IgG, measurable by ELISA. Plateau levels of circulating antibody attained were similar after mixed-sex and male-only infections, and vaccination with tegument membranes. Female-only infections and exposure to irradiated cercariae stimulated lower levels of anti-tegument antibody. Responses in rats were similar, but occurred more rapidly, probably due to the large initial parasite exposure. Although both mice and rats could be stimulated to produce high levels of anti-tegument antibody by multiple vaccination, consistent protection against a challenge was not obtained. Paradoxically, rats and mice vaccinated with irradiated cercariae developed low levels of antibody to tegument membrane antigens but were highly resistant to challenge. It was concluded that, in the range of sera examined, antibody responses to schistosome tegument membranes did not correlate with the immune status of the host.

The present paper is a further instalment of the Reports on the Molteno Institute collection, of which Parts I–III, dealing with the Ascaridae, Heterakidae, Oxyuridae, Camallanidae, etc., were published in this Journal by Dr H. A. Baylis in 1923. The history of the collection has been dealt with by that writer, and the following report on the Trichostrongylidae and Strongylidae is presented in as nearly as possible the same form as that of the preceding parts, consisting of a list of determinations of the material, together with notes on the less well-known forms and full descriptions of the new species. As in Parts I–III, the numbers attached to each set of specimens are the serial numbers given to the original tubes at the Molteno Institute.

A new trematode, Burnellus trichofurcatus, is described from South Australia from the freshwater catfish, Tandanus tandanus. It appears to have affinities with Monodhelmis Dollfus, 1937 and Mehratrema Srivastava, 1939, but is probably most closely related to Tandanicola Johnston, 1927 (Fellodistomatidae: Tandanicolinae). It is assigned to the Fellodistomatidae Nicoll, 1909, as emended by Cable (1953). Cercaria trichofurcata Johnston & Angel, 1940 is shown to be the larval stage. The cyst stage is omitted from the life cycle, with infection of the catfish occurring directly, probably by mouth. Further comments on developmental stages are given. The sporocyst is not branched, as described by Johnston & Angel (1940). The miracidium of Tandanicola bancrofti is reported, and the life history of this species is discussed. The genus is named for Dr R. H. Burnell in recognition of his help, over a number of years, in collecting animals used in these life history studies.

I would also like to acknowledge information and help given me by Dr J. C. Pearson, of the University of Queensland, and information on fish given me by Mr C. J. M. Glover, of the South Australian Museum.

Woodcock (1910) discovered a trypanosome naturally occurring in the blood of British sheep. This finding was confirmed by Behn (1911, 1912) in Germany. In both cases the authors did not give any description of the parasite, which was seen by them only in single cases, and they failed to cultivate the trypanosomes.

1. A ciliate occurring in the caecum of about 25 per cent, of the cattle that were examined at Jeanerette, Louisiana, is herein classified as Buxtonella sulcata Jameson (1926) and it is proposed that it be removed from the Class Aspirigera, Family Isotrichidae, and included in the Class Spirigera, Order Heterotrichida.

2. The ciliate is characterised by the position of the cytostome near the permanently open cytopyge and within the peristome which continues from the cytostome around the oral end of the body to the extreme aboral end which during locomotion is anterior.

3. The infections were detected in slaughtered animals by examining faecal material in Syracuse watch glasses under the binocular microscope, this method of faecal diagnosis having advantages over the smear method.

4. By the administration of Epsom salts the ciliates may be obtained from living cattle.

5. A pipette is described and figured for the isolation of Protozoa.

6. Death of Buxtonella sulcata in an unfavourable environment occurred by disruption of the endoplasm through the cytostome.

7. Buxtonella sulcata disappeared from faecal material at room temperature more quickly than balantidia from the pig, but withstood manipulation under the microscope better than the balantidia.

8. The passage of an individual between two obstructions suggested a means of intercellular tissue penetration by ciliates.

9. The oral plug and the centralised neuromotor system described and figured by McDonald in Balantidium coli could not be differentiated by the writer, but McDonald's other morphological observations on the above ciliates were confirmed.

The ultrastructure of the macrogamete and developing oocyst of Eimeria maxima (Weybridge strain) was examined in the intestinal cells of chicks fed 3 different anticoccidial drugs. Amprolium at 125 p.p.m., arprinocid at 35 p.p.m. and dinitolmide at 250 p.p.m. caused considerable morphological abnormality and incomplete development of the wall-forming bodies of Type 2 (WFB II), which did not appear able to participate in oocyst wall formation. The wall-forming bodies of Type 1 (WFB I) were able in each case to participate in oocyst wall formation although amprolium and dinitolmide produced morphological abnormalities in them. In birds medicated with dinitolmide, the outer layer of the oocyst wall was formed initially at opposite poles of the macrogame tes rather than as a uniform layer. Other abnormalities resulting from drug treatment are reported and some evidence that intravacuolar tubules may be formed by the parasite pellicle is presented.