1. Oviposition by L. sericata has been induced on a moist clipped fleece by incorporating ammonium carbonate and indole, hence attraction is not completely dependent on some factor produced by the living animal.

2. Chemistry of attractants. A new method for determining small amounts of hydrogen sulphide is described. Larval excreta contains hydrogen sulphide but no indole or skatole. Following incubation the ammonia and sulphydryl contents of various natural attractants are markedly increased.

3. Field trials on sheep. 0·002% ethyl mercaptan in conjunction with 0·1% ammonium carbonate was able to induce oviposition by L. sericata. The mercaptan concentration could be reduced to 0·001%, providing 0·0001% hydrogen sulphide was present. 0·01% mercaptan and aqueous solutions of hydrogen sulphide alone are not attractive.

4. The results obtained support the hypothesis that attraction is the result of the breakdown of cystine, with the production of sulphur compounds, coupled with the presence of ammonium carbonate (or of some putrefactive material).

5. Chemical baits. During the period 17 August–21 September 1943, various combinations of ammonium carbonate, hydrogen sulphide and indole in conjunction with sheep wool proved to be attractants for females of L. caesar.

Hybrid proteins containing selected regions of the major surface antigens of the sporozoite and merozoite stages of Plasmodium falciparum were expressed in insect cells using baculovirus vectors. A recombinant protein containing the signal peptide from the precursor to the major merozoite surface antigens (PMMSA) fused to a fragment from the carboxy (C) terminus of the same gene was recognized by monoclonal antibodies specific for reduction-sensitive conformational epitopes within the C-terminal fragment, suggesting that correct disulphide cross-linking of cysteine residues within this region had occurred. Addition of 26 copies of the tetrapeptide repeat from the circumsporozoite protein (CSP) resulted in a protein recognized by anti-CSP antiserum as well as the conformation specific inonoclonal antibodies. Deletion of the C-terminal putative anchor sequence from both proteins resulted in secretion of protein in a fully soluble form antigenically indistinguishable from the anchor containing products. Correct conformation was not observed when the proteins were expressed as polyhedrin fusions without the signal peptide. These data indicate that the PMMSA signal peptide is recognized in insect cells and that correct assembly of disulphide cross-links is dependent upon targeting the protein to the endoplasmic reticulum.

Cystoisospora belli is a coccidian parasite of humans, with a direct fecal–oral transmission cycle. It is globally distributed, but mainly found in tropical and subtropical areas. Many cases of C. belli infections have been reported in patients with HIV, and in patients undergoing immunosuppressive therapy for organ transplants or those treated for tumours worldwide. Unsporulated or partially sporulated oocysts of C. belli are excreted in feces. When sporulated oocysts in contaminated water or food are ingested, asexual and sexual stages of C. belli are confined to the epithelium of intestines, bile ducts and gallbladder. Monozoic tissue cysts are present in extra-intestinal organs (lamina propria of the small and large intestine, lymph nodes, spleen, and liver) of immunosuppressed humans. However, a paratenic host has not been demonstrated. Cystoisospora belli infections can be persistent, lasting for months, and relapses are common; the mechanism of relapse is unknown. Recently, the endogenous stages of C. belli were re-examined and attention was drawn to cases of misidentification of non-protozoal structures in the gallbladder of patients as C. belli. Here, we review all aspects of the biology of C. belli, including morphology, endogenous stages, prevalence, epidemiology, symptoms, diagnosis and control.

More than 20 species of the entomopathogenic nematode Steinernema have been described; to date, all reproduce exclusively by cross-fertilization of male and female individuals. Steinernema sp. strain T87 from Indonesia was found to consist largely of self-fertile hermaphrodites. Progeny were produced by morphological females both in insects (Galleria mellonella) and in hanging drops of insect haemolymph inoculated with a single infective juvenile. Sperm were present in the oviduct of unmated morphological females. Approximately 1% of infective juveniles developed into males, and males were also present in the second generation where they constituted 1–6% of the population. Under the same conditions the related species Steinernema longicaudum strain CB2B displayed typical steinernematid reproduction: cross-fertilization and a 1:1 sex ratio. It is argued that the development of hermaphroditism in Steinernema sp. T87 represents convergent evolution with Heterorhabditis, the other major genus of entomopathogenic nematode.

Two groups of goldfish maintained at 20°C were experimentally infected with two different sized inocula of Trypanosoma danilewskyi. One group was inoculated with 380000 trypanosomes/fish and the other with 3800. Forty and 90% of the fish, respectively, survived. All surviving fish challenged 190 days post-infection were protected from re-infection. The plasma of these fish when inoculated into another group of fish also protected them from infection. Finally, trypanosomes incubated in vitro in immune plasma at 20°C for 2 h were not infective; however, incubations at 5°C or for 1 h were not as effective.

1. In an alkaline inorganic solution containing borate, no bacterial disintegration of tissues occurs in a week.

2. Survival is prolonged by adding sugars to this solution, but not by the addition of bile salt or peptone. Monosaccharides are more effective than disaccharides, and both may enter the worm through its body wall.

3. The effect of variations in certain physicochemical conditions was studied. Wide ranges of osmotic pressure, of the K/Naratio, and of the Ca/Na ratio, have little effect on the worms. The optimum pH is c. 8.4, and t h e optimum temperature c. 36° C. Approximately anaerobic conditions decrease the survival time.

4. The effect of various bactericides, bacteriostatics and anthelmintics upon the worm were investigated in a preliminary manner. Many bactericides are toxic, certain anthelmintics are not. Survival is prolonged by 1/5000 trypan blue.

5. A satisfactory medium for large-scale ‘culturing’ is: NaCl 150 mM., KC1 10 mM., CaCl2 1 mM., borax 6 mM., glucose 30 mM. (pH 8.6). In this the worms survive for c. 60 hr. at a temperature of 36° C.

We produced a recombinant protein from a cDNA library from muscle larvae of Trichinella spiralis which had proteinase inhibitory activity. The predicted amino acid sequence of the clone had an identity of only 30% to the serine proteinase inhibitors (serpins) from Caenorhabditis elegans or Brugia malayi. At the putative reactive region, however, the identity was about 50%. The recombinant protein expressed in Escherichia coli inhibited 82% of the activity of the serine proteinase (trypsin). Stage-specific expression of this protein was suggested from the following experiments. Antibody against the recombinant protein could stain proteins migrating at about 42 kDa (which is the expected size from the sequence) in crude extracts from newborn larvae and 18-day post-infection (p.i.) muscle larvae, but it failed to stain any proteins in crude extracts from 30-day p.i. muscle larvae. Production of mRNA transcript for the serpin gene was restricted largely to the newborn larvae and to 18-day p.i. muscle larvae. The antibody reacted with the stichocytes of the larvae at 18 days p.i., but did not react with the muscle larvae at 24 days and 30 days p.i.

Plasmodium knowlesi a simian malaria parasite is currently affecting humans in Southeast Asia. Malaysia has reported the most number of cases and P. knowlesi is the predominant species occurring in humans. The vectors of P. knowlesi belong to the Leucosphyrus group of Anopheles mosquitoes. These are generally described as forest-dwelling mosquitoes. With deforestation and changes in land-use, some species have become predominant in farms and villages. However, knowledge on the distribution of these vectors in the country is sparse. From a public health point of view it is important to know the vectors, so that risk factors towards knowlesi malaria can be identified and control measures instituted where possible. Here, we review what is known about the knowlesi malaria vectors and ascertain the gaps in knowledge, so that future studies could concentrate on this paucity of data in-order to address this zoonotic problem.

Following the recent description of microfilariae of a Cercopithifilaria sp. in a dog from Sicily, Italy, (herein after referred to as Cercopithifilaria sp. I), numerous skin samples were collected from dogs in the Mediterranean region. In addition to Cercopithifilaria sp. I (185·7 ± 7·2 μm long), microfilariae of 2 other species were identified, namely Cercopithifilaria grassii (651·7 ± 23·6 μm long) and a yet undescribed microfilaria, Cercopithifilaria sp. II (264·4 ± 20·2 μm long, with evident lateral alae). The morphological differentiation among the 3 species of dermal microfilariae was confirmed by differences in cytochrome c oxidase subunit 1 and ribosomal 12S sequences examined (mean level of interspecific pairwise distance of 11·4%, and 17·7%, respectively). Phylogenetic analyses were concordant in clustering these with other sequences of Cercopithifilaria spp. to the exclusion of Dirofilaria spp., Onchocerca spp. and Acanthocheilonema spp. Dermal microfilariae collected (n = 132) were morphologically identified as Cercopithifilaria sp. I (n = 108, 81·8%), Cercopithifilaria sp. II (n = 17, 12·9%), whereas only 7 (5·3%) were identified as C. grassii. Mixed infestations were detected in all sites examined. The great diversity of these neglected filarioids in dogs is of biological interest, considering the complex interactions occurring among hosts, ticks and Cercopithifilaria spp. in different environments.

In laboratory studies with 3 species of Calliphora more than half were shown to ingest eggs of Taenia hydatigena from the surface of clog faeces with a maximum of over 5000 eggs in 1 fly. Most eggs were voided within 48 h and between 38 and 48% of these eggs had lost their embryophores. In field studies carried out in the South Island of New Zealand, traps baited with dog faeces captured the following blowfly species in decreasing order of abundance: Hybopygia varia, Calliphora quadrimaculata, C. hortona and C. stygia. Peak numbers were trapped in January, February and March. Almost 25% of wild flies, caught after feeding for up to 3 mm on dog faeces naturally contaminated with taeniid eggs, had eggs in their intestine. When administered to lambs all 4 species of fly transferred infection. Lambs grazed in winter on plots near kennels that had housed dogs with patent infections of T. hydatigena acquired higher worm burdens than those grazed further away. The burdens were greater downwind of the prevailing wind. After removal of the dogs, blowflies caught in the vicinity contained taeniid eggs but the contents of pitfall traps did not. Blowflies, and to a much lesser degree the insects and dust caught on sticky traps during the presence of the dogs, transferred infection when administered to naive lambs.

Transstadial transmission of Theileria annulata with Hyalomma anatolicum anatolicum, H. dromedarii and H. marginatum isaaci, and Haemaphysalis bispinosa, Rhipicephalus haemaphysaloides haema-physaloides and Boophilus microplus was determined.

It was found that the infection was successfully transmitted by H. a. anatolicum from larva to nymph and nymph to adult in all attempts. When larvae were fed on an infected calf the succeeding adults transmitted the infection when the intervening nymphs fed on a rabbit (nonsusceptible host) but not when fed on a calf (susceptible host). Infective adult ticks transmitted the parasite during the first 24 h of feeding on a calf. When the feeding was interrupted after 24 h, and the tick transferred to another calf, the infection was transmitted to the latter as well.

H. dromedarii successfully transmitted the infection from larva to nymph and from nymph to adult.

Larvae of H. marginatum isaaci did not feed on calves but the infection was successfully transmitted from nymph to adult.

Haemaphysalis bispinosa, Rhipicephalus h. haemaphysaloides and Boophilus microplus did not transmit Th. annulata from larva to nymph to adult.

BALB/c mice were characterized as more resistant to infection with Heligmosomoides polygyrus (Nematoda) than C57BL/6 mice based on lower establishment and survival during a primary infection and stronger protection induced by an immunizing regime. It was hypothesized, therefore, that C57BL/6 mice would be more heavily infected than BALB/c mice when they lived together as a single population in a large indoor arena where transmission occurred through contact between the mice and damp peat trays where parasite eggs developed into larvae. Fifty female mice (including 5 infected mice) of each strain were placed in a 3.2 x 0.8 m arena. Net egg production and numbers of larvae acquired by sentinel mice of each strain were monitored every two weeks. The experiment was replicated twice. The results did not support the hypothesis. No difference was detected between strains of mice in the number of larvae acquired by sentinel mice during 24 h exposure periods, or in the numbers of worms present after 12 or 23 weeks. Net egg production was also comparable between strains. A hypothesis that the unexpected similarity of infection in the two strains was related to differences in rates of contact with the peat trays was not supported by preliminary data on mouse behaviour that revealed equal frequency of contact with peat trays between strains. A second hypothesis that continuous exposure to larvae led to similar infection levels in the two strains (in contrast to the controlled characterization experiments) was also unsupported. Mice were infected weekly with 10, 50 or 100 larvae for 5 or 10 weeks. Net egg production and numbers of worms were consistently higher in C57BL/6 than BALB/c mice. At this time it is not clear why infection in the two strains was virtually identical in the large arenas but clearly distinct in all controlled infection experiments.

Further investigations have been carried out on the nature of ‘host’ antigens associated with the adult worms of Schistosoma mansoni. These investigations show:

1. The ‘host’ antigens are not removed from the surface of the worms by thorough washing and prolonged incubation in Hanks's balanced salts solution. The antigens must be firmly bound or even incorporated at the surface.

2. Monkeys cannot be immunized against ‘mouse worms’ with mouse IgG immunoglobulins. Accordingly it is unlikely that the ‘host’ antigens are mouse anti-worm antibodies.

3. The ‘host’ antigens are certainly associated with the membranes of mouse erythrocytes. They may also be associated with the ‘soluble protein’ fraction of the erythrocytes.

4. Immunization with sheep erythrocytes failed to protect monkeys against challenge with ‘mouse’ worms. Therefore it is unlikely that the ‘host’ antigens are Forssman antigen.

5. The mouse ‘host’ antigens associated with ‘mouse’ worms are not major histocompatibility antigens. Consequently it is likely that they are species-specific mouse antigens.

1. Histochemical and biochemical studies have demonstrated the presence and distribution of phosphatases in Cysticercus tenuicollis and adult Moniezia expansa.

2. Biochemical tests have differentiated the following types of optimum phosphatase activity: Cysticercus tenuicollis, acid phosphatase, pH 5·0 (approx.); alkaline phosphatase, pH 10·0 (approx.); Moniezia expansa, acid plaosphatase, pH 5·5 (approx.); alkaline phosphatase, pH 7·0–8·0 and pH 10·0–11·0.

3. Attempts to locate the enzymes by normal histochemical methods were unsuccessful in the case of Cysticercus tenuicollis. In adult Moniezia, acid and alkaline phosphatase (both types) occurred in the cuticle. Alkaline phosphatase (pH 10·0–11·0) only was present in the tunicae enclosing the ovary, vitelline gland and testes. This enzyme was also the only one present in the interproglottidal glands, in the wall of the developing uterus and in the subcuticular cells.

4. Tests for all types of phosphatase activity showed that cuticular activity in Moniezia originated in the walls of an extensive branched system of channels. This system was demonstrable in the cuticle of fixed and unfixed material.

5. Incubation experiments with entire living Moniezia showed that substrates external to the body were capable of being broken down. Similar tests with Cysticercus tenuicollis showed that at least some of the alkaline phosphatase activity recorded by the biochemical tests was located in the cuticle.

The organization of Ascaris motoneurones and nervous system is summarized. There is an anterior nerve ring and associated ganglia, main dorsal and ventral nerve cords which run longitudinally, and a small set of posterior ganglia. Cell bodies of motoneurones are found in the ventral nerve cord and occur in 5 repeating ‘segments’; each contains 11 motoneurones. Seven morphological types of excitatory or inhibitory motoneurone are recognized.

Each Ascaris somatic muscle cell is composed of the contractile spindle; the bag region, containing the nucleus; the arm; and the syncytial region, the location of neuromuscular junctions. The resting membrane potential of muscle is approximately — 30 mV and shows regular depolarizing, Ca-dependent ‘spike potentials’ superimposed on smaller Na+- and Ca2+-dependent ‘slow waves’ and even slower ‘modulation waves’. The membrane shows high Cl- permeability. Adjacent cells are electrically coupled so that electrical activity in the cells is synchronized. Acetylcholine (ACh) and γ-aminobutyric acid (GABA) affect the electrical activity. Bath-applied ACh increases membrane cation conductance, depolarizes the cells, alters the frequency and amplitude of spike potentials and produces contraction. Bath-applied GABA increases Cl- conductance, decreases spike activity and causes hyperpolarization and muscle relaxation.

The extra-synaptic ACh receptors on the bag region of Ascaris muscle can be regarded as a separate subtype of nicotinic receptor. ACh and anthelmintic agonists (pyrantel, morantel, levamisole) produce a dose-dependent increase in cation conductance and membrane depolarization which is blocked by tubocurarine, mecamylamine but not by hexamethonium. The potency, of GABA agonists, with the exception of sulphonic acid derivatives, correlates with the vertebrate GABAa receptor. The potency of antagonists does not. Thus, bicuculline, securinine, pitrazepine, SR95531 and RU5135 are potent vertebrate GABAa antagonists but have little effect on GABA receptors. The potency order of the arylaminopyridazine GABA antagonists: SR95103, SR95132, SR42666, SR95133, SR95531, SR42627 and SR42640 at the Ascaris GABA receptors contrasts with that at vertebrate GABAa receptors. It has been suggested that the receptor is referred to as a GABAn receptor.

Patch-clamp studies show that ACh activates a non-selective cation channel which has a main conductance of 40–50pS and apparent mean open time of 1·3 ms; a smaller channel of 20–30 pS with a similar open-time is also activated. Pyrantel and levamisole also produce openings with similar conductances and open-times. GABA activates a Cl- channel with a main state conductance of 22 pS and an apparent mean open duration of 32 ms; conductance states of 10 and 15 pS are also seen. Piperazine similarly activates this channel but the mean open-time is shorter (14 ms). Ivermectin in high doses, is an antagonist which reduces the GABA channel conductance and Popen; it does, however, open ‘small’ Cl- channels when applied to the outside surface of membrane. These channels have a conductance of 9–15 pS and very long open times (> 100 mS). 5-HT does not have a direct effect on membrane potential or conductance but acts on cAMP levels and glycogen metabolism. Dopamine, octopamine and AF1 may act as neurotransmitters or neuromodulators.

The effects of mild to moderate infections of Trichuris trichiura on cognitive functions were investigated in Jamaican children aged 7 to 10 years. In all, 189 infected children and 100 uninfected classmates were studied. The infected children were randomly assigned to receive treatment (albendazole) or a placebo. All children were given cognitive tests on enrolment and 14 weeks later. These included verbal fluency (generation of ideas), digit span (working memory), number choice (speed of processing of visual stimuli), visual search (sustained attention) and a French Vocabulary test (paired-associate learning). At baseline, the infected children had lower scores than the uninfected ones in fluency (P = 0·01), search (P = 0·02) and French (P = 0·01). Treatment effects were examined among infected children and there was no significant treatment effect for any of the tests. However, there was a significant treatment by weight-for-age interaction in fluency (P < 0·05). The children with low weight-for-age (Z-score < – 1) improved with treatment while there was no improvement with treatment among the other children. We concluded that treatment of children with mild to moderate T. trichiura infections using albendazole produces little benefit in cognition if they are adequately nourished; however, undernourished children are more likely to benefit.

Up to the present time the polyhedral viruses of insects have been considered to be extremely specific in their infectivity, and cases of cross-infection, even between closely related species, were regarded as rare occurrences. Recently, however, we have recorded results which suggest that there is no such specificity of infection (Smith & Xeros, 1952). In the following paper we describe the results obtained in an extensive series of cross-inoculations among a heterogeneous collection of lepidopterous larvae, selected entirely at random. The results obtained appear at first sight to be compatible with one clear-cut explanation of straightforward cross-infections with differential multiplication of two different viruses in different hosts. Other complications, however, cannot be excluded and one or two possible situations are discussed later in the paper.

The infectivity and distribution of Echinostoma trivolvis were studied in male, conventional and congenitally athymic nude mice, each infected with 30 metacercarial cysts. In conventional mice, worm recoveries at 6 and 8 days post-exposure were58·3 and 54·0%, respectively. Worm recovery declined to 44·0% by day 10, to 4·3% by day 13, and 0% by day 17. In athymic mice, worm recoveries at 6 and 8 days post-exposure were 61·7 and 36·3%, respectively. Worm recovery declined to 27·7% by day 10, to 0·7% by day 13, and 0% by day 17. The distribution of worms demonstrated a posteriad migration over time in both groups. Kinetic changes in the number of goblet and mucosal mast cells in the upper ileum of mice infected with E. trivolvis were examined. In conventional mice, the number of goblet cells increased rapidly to reach a peak at day 13 and then declined gradually. The number of goblet cells in athymic mice also increased to reach a peak at day 13, and then declined rapidly. However, the number of goblet cells in athymic mice was always less than that inconventional mice. The mast cell number in infected conventional mice increased rapidly to reach a peak at day 17 and then declined. There was no increase in the mast cell number of infected athymic mice throughout the experiment. Whereas common pathological changes occurred in the intestines of both mice groups infected with echinostomes some ultrastructural differences were observed in the gut epithelial cells of conventional versus athymic mice.

One stock of each of Leishmania mexicana mexicana and L. m. amazonesis together with two stocks of L. braziliensis panamensis and L. b. braziliensis were tested for infectivity in inbred mouse strains Balb/c and CBA/H. The infectivity was compared with hamsters and the outbred CD1 mice. Balb/c mice were more susceptible than hamsters to L. mexicaba and L. braziliensis panamensis. Balb/c mice were not susceptible to L. b. braziliensis. CBA/H mice showed a low susceptibility to infection while CD1 mice showed an intermediate response

Leishmania (Viannia) braziliensis is a protozoan that causes mucocutaneous leishmaniasis, which is an infectious disease that affects more than 12 million people worldwide. The available treatment is limited, has side-effects or is inefficient. In a search for alternative compounds of natural origin, we tested the microbicidal activity of Piper aduncum essential oil (PaEO) on this parasite. Our data showed that PaEO had an inhibitory effect on the growth of L. braziliensis promastigotes with an IC50/24 h=77·9 µg mL−1. The main constituent (nerolidol: 25·22%) presented a similar inhibitory effect (IC50/24 h = 74·3 µg mL−1). Ultrastructural observation of nerolidol-treated parasites by scanning and transmission electron microscopies revealed cell shrinkage and morphological alterations in the mitochondrion, nuclear chromatin and flagellar pocket. Flow cytometry analysis showed a reduction in the cell size, loss of mitochondrial membrane potential, phosphatidylserine exposure and DNA degradation, which when associated with the morphological changes indicated that nerolidol induced incidental cell death in the L. braziliensis promastigotes. The results presented here indicate that nerolidol derivatives are promising compounds for further evaluation against Leishmania parasites.