Adults of the family Simuliidae have been known in Europe for a very long time as very serious pests affecting both men and cattle, and there were many interesting legends, even up to the middle of the eighteenth century, explaining their origin from grottos in the mountains (Tömösváry). Fabricius (1784) for the first time found a Simulium pupa (probably that of S. venustum Say) and described it under the name Tipula sericea, but to Schönbauer (1795) we owe the discovery that the earlier stages (egg, larva and pupa) of Simulium (Kolumbatczer-Mücke) are to be found in running water.

Plasmodium falciparum causes the most severe form of malaria. Utilization of fatty acids in serum is thought to be necessary for survival of this parasite in erythrocytes, and thus characterization of the parasite fatty acid metabolism is important in developing a new strategy for controlling malaria. Here, we examined which combinations of fatty acids present in human serum support the continuous culture of P. falciparum in serum-free medium. Metabolic labelling and gas chromatography analyses revealed that, despite the need for particular fatty acids for the growth of intraerythrocytic P. falciparum, it can metabolize a broad range of serum-derived fatty acids into the major lipid species of their membranes and lipid bodies. In addition, these analyses showed that the parasite's overall fatty acid composition reflects that of the medium, although the parasite has a limited capacity to desaturate and elongate serum-derived fatty acids. These results indicate that the Plasmodium parasite is distinct from most cells, which maintain their fatty acid composition by coordinating de novo biosynthesis, scavenging, and modification (desaturation and elongation).

In order to assess the infection risk of alveolar echinococcosis among urban residents of Sapporo, the capital of Hokkaido, Japan, a survey was conducted on fox distribution in the urban area and on the prevalence of Echinococcus multilocularis among the foxes. The fox distribution, evaluated from fox footprints left on the snow in parks and woodlands, and from locations of fox carcasses recorded by the Sapporo municipality, was concentrated along the border of the urban area and in the southwestern part of the city, facing the mountain. Fox faeces were collected around active fox dens, and analysed by a coproantigen detection assay and parasite egg examination for the Echinococcus infection. Thirty-three out of 155 faeces were coproantigen positive. Coproantigen-positive faeces were collected from 11 den sites (57·9% of total den sites), and all except 1 were located in the urban fringe. A high intensity of taeniid eggs (>100 eggs per 0·5 g) containing faeces were also collected in the 3 sites of them. Although Echinococcus infection in rodents was not observed from the necropsy of 23 rodents captured around active fox dens, arvicolid rodents, a suitable intermediate host for E. multilocularis, were captured in the urban fringe. Therefore, the urban fringe offers suitable conditions in which the life-cycle of E. multilocularis could be maintained. Prompt measures to control echinococcus infection should be taken, even in urban areas.

Although artesunate, one of the potent derivatives of the qinghaosu family of drugs for treating falciparum malaria, is already in use in the field, its therapeutic protocol has only been developed empirically by hit-or-miss. A pharmacokinetic–pharmacodynamic (PK–PD) model, required for creating such a protocol, is not straightforward. Artesunate presents extremely fast pharmacokinetics. As a result the stage specificity of its action must be treated explicitly. Also, use of standard PK–PD modelling fails to explain the clinical results. Our PK–PD modelling of its activity leads us to the postulation of the existence of a novel effect: a small fraction of the parasites, as a result of chemotherapeutic pressure, become cytostatic, or ‘dormant’. At this stage, the parasite cycle is halted, making them unsusceptible to further dosing until wakening. This slows down the antimalarial activity of the drug, entailing either many frequent doses or an extended period of treatment and surveillance. Based on our modelling, we suggest a method for deciding on rational models of chemotherapy against falciparum malaria.

An account is given of an apparently undescribed virus disease. The virus appears spontaneously in the glasshouse affecting tobacco seedlings in the seed boxes. The symptoms on a number of hosts are described. The chief characteristic of the virus is its failure to become systemic in any host plant so far tested. It is, however, occasionally found in the roots of young tobacco plants, usually in the case of those naturally infected. Certain physical properties of the virus have been investigated. Its dilution end-point appears to be about 1:10,000; its longevity in extracted sap is about 20 days, the thermal death-point is 72° C. The virus shows a strong resistance to alcohol, remaining viable in 99 per cent, alcohol for 71 hours so far as tested.

It is not known how the virus is transmitted in nature, and no insect vector has as yet been identified.

The virus has been transmitted to healthy cowpeas by spraying them with a suspension of the virus by means of an atomiser.

By the Elford method of ultra-filtration the particle size is found to be 20–30μμ.

The virus is compared with that of the American tobacco ringspot, and methods of differentiating the two are indicated.

The course of primary infection with a hamster-adapted strain of Ancylostoma ceylanicum was studied in inbred DSN and randomly bred WO/GD and WO/CR hamsters. Infective larvae were administered orally and began to develop in the small intestine without embarking on a tissue migration. Only the occasional larva was detected in other organ sites. It was concluded that the developing larvae moulted on days 3–4 and again to the pre-adult stage about 9–11 days post-infection. Worm burdens in infected hamsters were stable for at least 11 weeks after infection. There was no sudden expulsive phase and some adult worms survived for over 200 days. Overall the sex ratio of worms in groups of hamsters killed concurrently was about 50% although occasionally the ratio was biased in favour of one sex in individual animals. The blood packed cell volume (PCV) was significantly depressed 2 weeks following infection and continued to decline until a point of stability was achieved 4–5 weeks post-infection. The PCV subsequently remained depressed throughout the period of observation. Infected hamsters lost weight if kept in groups, but not when housed in separate cages. Groups of animals which lost weight did not recover to normal values within 11 weeks of infection. It is suggested that this model of hookworm infection has scope for exploring aspects of the host-parasite relationship which the canine models cannot fulfill adequately.

Guppies (Lebistes reticulatis) exposed to doses as low as 25 cercariae of Diplostomum spathaceum for 30 min were consistently and significantly more susceptible to predation by brook trout (Salvelinus fontinalis) than uninfected controls. The increase in susceptibility to predation was correlated with a marked decrease in the activity of infected fish.

Genetic variation in susceptibility to pathogens is a central concern both to evolutionary and medical biologists, and for the implementation of biological control programmes. We have investigated the extent of such variation in Drosophila melanogaster, a major model organism for immunological research. We found that within populations, different Drosophila genotypes show wide-ranging variation in their ability to survive infection with the entomopathogenic fungus Beauveria bassiana. Furthermore, striking divergence in susceptibility has occurred between genotypes from temperate and tropical African locations. We hypothesize that this may have been driven by adaptation to local differences in pathogen exposure or host ecology. Genetic variation within populations may be maintained by temporal or spatial variation in the costs and benefits of pathogen defence. Insect pathogens are employed widely as biological control agents and entomopathogenic fungi are currently being developed for reducing malaria transmission by mosquitoes. Our data highlight the need for concern about resistance evolution to these novel biopesticides in vector populations.

The modified agglutination test (MAT) is one of the most commonly used tests for the detection of antibodies to Toxoplasma gondii in animal and human sera. The objective of the present study was to evaluate the diagnostic accuracy of the MAT and bioassay in free-range/backyard (FR) chickens (Gallus domesticus). Previously-published T. gondii test results from 2066 chickens from 19 countries were compiled for the present study. The frequency of isolation of T. gondii increased for MAT titres between 1:5 and 1:160, and ranged from 61 to 75% for antibody titres of 1:160, 1:320, and ⩾1:640. Twenty-three cats fed pooled hearts from a total of 802 FR seronegative (MAT, <1:5) chickens from several countries did not excrete oocysts, indicating a high negative predictive value of MAT because FR chickens would have been exposed to many microbes; cats are the most sensitive indicators of T. gondii infection in tissues and can excrete millions of oocysts after ingesting even a few bradyzoites. Of the 29 cats in this study, six cats, fed hearts pooled from 15–122 FR chickens, excreted oocysts; but these identifications were likely related to misidentification or prozone. Results of the present study support the validity of MAT for the detection of T. gondii infection in chickens.

Seroprevalence of Coxiella burnetii, the causal agent of Q fever in humans, was examined in wild brown rat populations from 4 Oxfordshire farmsteads (n = 127), 9 Somerset homesteads (n = 98), and 1 captive enclosure (n = 88) in the UK. Seroprevalence ranged between 7 and 53%, the lowest being within the captive population and the highest on dairy farmsteads with sheep present. This is the first reported investigation of C. burnetii in wild rats outside India. We suggest that the high Seroprevalence among rats (i) provides evidence that wild rats constitute an important reservoir for C. burnetii in the UK, and (ii) explains why cats, as frequent predators of rats, are so important in the epidemiology of this disease.

Significant levels of resistance against Schistosoma mansoai challenge were developed by mice exposed to highly irradiated (20 krad.) cercariae of the homologous species (53–67%), whereas vaccination with S. bovis, S. haematobiurn or S.japonicuni failed to confer significant levels of resistance (–5–12%), thus confirming the specificity ofthe immunizing procedure. Attempts to transfer resistance to naive recipients by injection of serum and of spleen or lymph node cells from donor mice vaccinated with highly irradiated cercariae were largely unsuccessful. However, significant levels of resistance could be transferred to mice by injection of serum from rabbits exposed to irradiated cercariae. Comparable levels of resistance were conferred by injection of serum at the time of challenge (34–69%) or 5–6 days later (31–56%). Tn contrast, sera from rabbits injected with solubleegg antigen or homogenized cercariae failed to confer protection upon recipient mice. Sera from vaccinated mice, vaccinated rabbits and antigen-injected rabbits all caused cell adherence to skin-transformed schistosomula hut neither the level of adherence nor the serum titre correlated with the ability to confer protection to mice.

The heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2–6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.

Following a brief introduction of recent advances in molecular and immunological technology for detection of persons and animals infected with Echinococcus multilocularis and an overview of the current situation of alveolar echinococcosis (AE) in Japan, perspectives on control options are discussed with reference to different epidemiological situations. AE is considered the most serious parasitic zoonosis in temperate and arctic regions of the northern hemisphere. The number of human cases differs drastically among regions. While high numbers of patients are apparently associated with high E. multilocularis prevalence in domestic dogs, e.g. in parts of Alaska and western China, the number of cases is moderate or low in areas where the parasite is mainly transmitted by wild canid species (e.g. in central Europe or temperate North America). However, the severity of the disease, the absence of curative treatment for most cases, the high cost of long-term chemotherapy and the anxiety caused for the population in highly endemic areas call for the development of preventive strategies even in regions where human AE is rare. Furthermore, in view of (1) drastically increasing numbers and infection rates of foxes involved in transmission of E. multilocularis, and (2) increasingly close contact between humans and foxes e.g. in Europe and Japan, there is considerable concern that AE incidences may in future increase in these regions. Control options depend on a variety of factors including the species of canid principally responsible for transmission and the socio-economic situation in the region. Where domestic dogs (stray or owned) are the principal hosts for E. multilocularis, control options can include those applicable to E. granulosus, i.e. reduction of the number of stray dogs, registration and regular preventive chemotherapy of owned dogs, and information campaigns for the population promoting low-risk behaviour for man and dogs. Where E. multilocularis is mainly transmitted by wild canids, the situation is far more difficult with preventive strategies still being in trial stage. Integrated control measures could include prevention information campaigns, restricting access of pet animals (dogs and cats) to rodents, chemotherapy of foxes on local or regional scales, and strategies to minimize contacts between people and foxes.

A multi-marker nuclear genotyping approach was performed on larval and adult specimens of Anisakis spp. (N = 689) collected from fish and cetaceans in allopatric and sympatric areas of the two species Anisakis pegreffii and Anisakis simplex (s. s.), in order to: (1) identify specimens belonging to the parental taxa by using nuclear markers (allozymes loci) and sequence analysis of a new diagnostic nuclear DNA locus (i.e. partial sequence of the EF1 α−1 nDNA region) and (2) recognize hybrid categories. According to the Bayesian clustering algorithms, based on those markers, most of the individuals (N = 678) were identified as the parental species [i.e. A. pegreffii or A. simplex (s. s.)], whereas a smaller portion (N = 11) were recognized as F1 hybrids. Discordant results were obtained when using the polymerase chain reaction–restriction fragment length polymorphisms (PCR–RFLPs) of the internal transcribed spacer (ITS) ribosomal DNA (rDNA) on the same specimens, which indicated the occurrence of a large number of ‘hybrids’ both in sympatry and allopatry. These findings raise the question of possible misidentification of specimens belonging to the two parental Anisakis and their hybrid categories derived from the application of that single marker (i.e. PCR–RFLPs analysis of the ITS of rDNA). Finally, Bayesian clustering, using allozymes and EF1 α−1 nDNA markers, has demonstrated that hybridization between A. pegreffii and A. simplex (s. s.) is a contemporary phenomenon in sympatric areas, while no introgressive hybridization takes place between the two species.

Infection with Toxocara canis is a common world-wide human helminthiasis, which rarely elicits central nervous system (CNS) impairment. A case-control study to investigate this discrepancy was carried out, in which the cases were 27 adult neurological inpatients for whom a definite aetiological diagnosis was lacking, and for whom positive immunodiagnosis of toxocariasis had been obtained, both in cerebrospinal fluid (CSF) and in serum. Two control groups were used. Controls were adult inpatients with other neurological diseases who had no evidence of T. canis infection of the CNS. Multivariate logistic regression analysis did not reveal any positive relation between case status and clinical signs. A significant association was observed between case status and an elevated CSF cell count. Rural residence, ownership of dogs, and dementia were shown to be risk factors for toxocaral infection of CNS. These results suggest that migration of T. canis larvae in the human brain does not frequently induce a recognizable neurological syndrome but is correlated with the association of several risk factors including exposure to dogs, a status possibly responsible for repeated low-dose infections.

High incidence of mycoses were found in the guts and malpighian tubes of Phlebokomus papatasi from the Jordan Valley and P. tobbi from Zakinthos, Greece. Infections with several different bacteria were also found in the guts of female P. tobbi. Fungi cultured from guts of laboratory reared P. papatasi that had similar mycoses were identified as Aspergillus scierotiorum and Saccharomyces cerevisiae. Fungi-infected laboratory reared P. papatasi were refractory to artificial infections with a Leishmania major strain specific to them. The crop contents of P. papatasi, where sugar meals are stored, demonstrated antibacterial activity against the following bacterial species in culture: Escherichia coli, Staphylococcus aureus, Shigella sonnei, Streptococcus group A and Pseudomonas aeruginosa. It is postulated that the bacteria-free gut normal to sandflies is effected by the bacterial inhibitor present in the crop.

The fine structure and organization of the nervous system of the miracidium is described. The central ganglion consists of a mass of nerve fibres with peripherally situated cell bodies. Tracts of fibres run outward from the central mass to the muscles of the body wall and to specialized endings. The individual fibres contain several types of inclusions and synapses are common in the neuropile.

Excluding the eyespots, four kinds of specialized nerve endings are described. Two of these types terminate at the body surface and bear ‘cilia’. The other two terminate internally, one type within the body wall and the other type laterally, slightly anterior to the central ganglion. It is suggested that the function of three of the types of ending might be sensory, detecting chemical and mechanical stimuli, and the direction of gravity. The function of the fourth type of ending is problematical but might be secretory.

I am most grateful to Dr A. Robards for use of electron microscope facilities and to Mrs J. Denison for technical assistance.

Trout collected from the Hanningfield Trout Farm in Essex, England, were found to be infected with Diplostomum spathaceum. Yearling rainbow trout were blinded with heavy infections of eyefluke, whereas brown trout of the same age carried one-tenth the number of flukes and were clear eyed. Both species were reared under identical conditions, in parallel rearing channels which received water from a common source. Samples showed that young fish exhibited a similar differential in their infestations, and that rainbow trout did not appear to be age-resistant. Laboratory infections produced by exposure of fish to suspensions of cercariae and injection of cercariae into the body cavity reflected the field results, indicating that ecological factors were not involved. Recovery of cercariae from host tissues, and histological observations of similar numbers entering both hosts, indicated that cercariae were able to survive penetration. Excised eye preparations were equally susceptible to infection. Two cm fry of both species were shown to be highly susceptible. Migration in brown trout took 3 h longer than in rainbow trout of the same size, many cercariae being found in the heart during this time. Two mechanisms of insusceptibility were suggested: (1) a greater impenetrability of brown trout tissues; (2) a disorientation of migrating cercariae in brown trout.

Two hybridomas secreting monoclonal IgM antibody to Schistosoma mansoni have been isolated following fusion of spleen cells from Balb/c mice immunized with living S. mansoni and NS1 myeloma cells. One monoclonal IgM antibody (WP66.4) mediated about the same level of passive protection against a challenge infection as immune serum from mice with a chronic S. mansoni infection. The other monoclonal antibody (WP66.2) did not give a significant level of passive protection. This result indicates that the effective monoclonal antibody recognizes an antigen which may be a valuable candidate for experimental vaccination. In vitro one monoclonal antibody (WP66.4) caused a much higher level of complement-dependent cytotoxicity than the other (WP66.2), suggesting a possible mechanism for the effect observed in vivo. With indirect immunofluorescence both monoclonal antibodies reacted with surface determinants on living S. mansoni schistosomula, adult worms and miracidia but these determinants were not detected on cercariae or lung schistosomula. Neither monoclonal antibody cross-reacted with S. haematobium schistosomula or Fasciola hepatica metacercariae, indicating a possible use for these reagents in differential diagnosis of S. mansoni infections.

Bovine besnoitiosis is caused by the largely unexplored apicomplexan parasite Besnoitia besnoiti. In cows, infection during pregnancy often results in abortion, and chronically infected bulls become infertile. Similar to other apicomplexans B. besnoiti has acquired a largely intracellular lifestyle, but its complete life cycle is still unknown, modes of transmission have not been entirely resolved and the definitive host has not been identified. Outbreaks of bovine besnoitiosis in cattle were described in the 1990s in Portugal and Spain, and later several cases were also detected in France. More cases have been reported recently in hitherto unaffected countries, including Italy, Germany, Switzerland, Hungary and Croatia. To date, there is still no effective pharmaceutical compound available for the treatment of besnoitiosis in cattle, and progress in the identification of novel targets for intervention through pharmacological or immunological means is hampered by the lack of molecular data on the genomic and transcriptomic level. In addition, the lack of an appropriate small animal laboratory model, and wide gaps in our knowledge on the host-parasite interplay during the life cycle of this parasite, renders vaccine and drug development a cost- and labour-intensive undertaking.