Female (Fig. 1): Colour: scutum, basis capituli, coxae, distal parts of femur and proximal portions of tarsi and intervening articles are blackish brown, the remaining hard parts shading to yellowish-brown. (Dorsal aspect) Body (partly gorged) short and broad. Scutum about as long as broad, 0·87 × 0·85 mm., very slightly emarginated, with rounded scapular angles, antero-lateral borders almost straight, lateral angles situated at the anterior third of the length, posterior border rounded; cervical grooves deep, far apart, but slightly concave outwardly and slightly divergent, fading near the postero-lateral borders; surface glossy, somewhat rugose; punctations few, mostly fine. Capitulum with base roughly equilateral-triangular, short pointed cornua and sinuous dorsal ridge; porose areas not depressed, subcircular, near ridge, the interval less than their width and hollowed. Palps slender, article 1 small, articles 1–2 almost fused, broadest at the distal third of article 3 which is rounded distally; (Ventral aspect) hypostome club-shaped, 4|4 merging to 3|3 and 2|2 posteriorly where the median unarmed ridge broadens, teeth sharp, 12 per external file; basis capituli constricted where the short pointed recurved auriculae arise, posterior margin straight with rounded angles. Venter: vulva between coxae II; anal grooves form a small closed ring situate near the posterior border; spiracle ovoid, macula central. Legs slender; coxa I with short internal and stout external spur; stout external spurs on coxae II–IV progressively decreasing in size; trochanters with slight spurs; tarsus 4 tapering gradually, the distal pseudo-article about thrice as long as the basal; pads large but shorter than the claws.

In this paper we discuss several established and potential animal models for human parasitic infection, with a focus on rodent, pig and primate models and the nematodes Ascaris, Trichuris and Toxocara spp. Firstly, we discuss the relevance of choosing a suitable animal host to fit the particular study hypothesis, and the interaction between mathematical modelling and animal models. Secondly, we review the use of animal models for the study of nutrition-parasite interaction, evaluation of treatment and control strategies, and bacteria-parasite interactions. We show that rodent, pig and primate models are all very useful in parasitological research, and that each model has its limitations. However, based on recent experience with the pig-Ascaris and pig-Trichuris models, a more extensive use of the pig-parasite model is advocated, especially for the study of the interaction between human malnutrition and helminth infection, and congenital helminth infection.

Parasite transmission dynamics are fundamental to explaining the evolutionary epidemiology of disease because transmission and virulence are tightly linked. Horizontal transmission of microsporidian parasites, e.g. Nosema bombi, may be influenced by numerous factors, including inoculation dose, host susceptibility and host population heterogeneity. Despite previous studies of N. bombi and its bumble bee hosts, neither the epidemiology nor impact of the parasite are as yet understood. Here we investigate the influence N. bombi spore dosage (1000 to 500 000 spores), spore source (Bombus terrestris and B. lucorum isolates) and host age (2- and 10-day-old bees) have on disease establishment and the presence of patent infections in adult bumble bees. Two-day-old bees were twice as susceptible as their 10-day-old sisters, and a 5-fold increase in dosage from 100 000 to 500 000 spores resulted in a 20-fold increase in the prevalence of patent infections. While intraspecific inoculations were 3 times more likely to result in non-patent infections there was no such effect on the development of patent infections. These results suggest that host-age and dose are likely to play a role in N. bombi's evolutionary epidemiology. The relatively low levels of horizontal transmission success are suggestive of low virulence in this system.

Although there is an increasing understanding of the role of parasites in their host dynamics, accurate, quantitative estimates of parasite caused morbidity in wild animals are rare. Here, we examine the possible impact of 2 tick species (Ixodes ricinus, I. hexagonus) on the condition of the European hedgehog (Erinaceus europaeus). For this, we tested for correlations between blood parameters of 36 adult hedgehogs from an experimental population enclosed in a natural habitat and their tick infestation over a period of 8 months (March–October 2007). We found correlations between the tick infestation and the concentration of red blood cells, haemoglobin, haematocrit, MCH, MCHC, thrombocytes, lymphocytes and neutrophils. These results indicate that ticks can induce anaemia in the hedgehog. The peripheral blood characteristics and the erythrocyte indices characterize this anaemia as haemorrhagic and regenerative. During the course of our study the hedgehogs of our population showed below normal mortality but morbidity was found to be high resulting from the blood loss caused by the feeding activity of the ticks.

Transient changes in calcium (Ca2+) levels regulate a wide variety of cellular processes, and cells employ both intracellular and extracellular sources of Ca2+ for signalling. Praziquantel, the drug of choice against schistosomiasis, disrupts Ca2+ homeostasis in adult worms. This review will focus on voltage-gated Ca2+ channels, which regulate levels of intracellular Ca2+ by coupling membrane depolarization to entry of extracellular Ca2+. Ca2+ channels are members of the ion channel superfamily and represent essential components of neurons, muscles and other excitable cells. Ca2+ channels are membrane protein complexes in which the pore-forming α1 subunit is modulated by auxiliary subunits such as β and α2δ. Schistosomes express two Ca2+ channel β subunit subtypes: a conventional subtype similar to β subunits found in other vertebrates and invertebrates and a novel variant subtype with unusual structural and functional properties. The variant schistosome β subunit confers praziquantel sensitivity to an otherwise praziquantel-insensitive mammalian Ca2+ channel, implicating it as a mediator of praziquantel action.

This investigation quantifies some aspects of the parasite–host relationship between the digenean Microphallus piriformes and its intermediate host Littorina saxatilis, the rough periwinkle. M. piriformes has an abridged life-cycle with no free-living stages, metacercariae remain within host viscera. Noticeable differences in shell shape of parasitized and uninfected periwinkles were investigated. These differences in shell shape were defined by growth parameters of height, diameter and β angle. The relationship between these parameters was examined together with their impact on parasite reproduction. All 3 shape parameters were altered in periwinkles infected by M. piriformes. The alteration in β angle and height increased the available volume for parasites in the shell spire by about 12%. As metacercarial production per sporocyst has been shown to depend on host size, the increased volume enables considerable additional life-time reproduction by the parasite, of approximately 550–850 additional metacercariae in hosts of the usual size range. The form of gigantism found in this study is discussed in relation to previous concepts. It is suggested that gigantism in permanently castrated hosts is adaptive parasite manipulation of host physiology, favoured in parasites with abbreviated life-cycles, when host viability increases parasite transmission, and when an initially small host individual is infected.

If the deleterious effects of non-specific parasites are greater on vulnerable host species than on reservoir host species then exclusion of the vulnerable host through apparent competition is more likely. Evidence suggests that such a mechanism occurs in interactions between the ring-necked pheasant (Phasianus colchicus), the grey partridge (Perdix perdix), and their shared caecal nematode Heterakis gallinarum. Modelling of the system predicts that the reduced parasite impact on the pheasant compared to the partridge results in the force of infection transmitted from pheasants to partridges being sufficient to cause partridge exclusion. Since the parasite impacts are currently estimated from correlational work, controlled infections were conducted to experimentally compare the impact of H. gallinarum on the two hosts and verify cause and effect. While challenged partridges showed reduced mass gain, decreased food consumption, and impaired caecal activity, in comparison to controls, the only detectable effect of parasite challenge on the pheasant was impaired caecal activity. The impact of H. gallinarum on challenged partridges conforms with previous correlational data, supporting the prediction that parasite-mediated apparent competition with the ring-necked pheasant may result in grey partridge exclusion. However, the observed decrease in the caecal activity of challenged pheasants could imply that H. gallinarum may also have an impact on the fecundity and survival of pheasants in the wild, particularly if food is limiting. If this is the case, the associated decrease in the force of infection to which the partridge is exposed may be sufficient to change the model prediction from partridge exclusion to pheasant and partridge coexistence.

Mechanisms affecting patterns of vector distribution among host individuals may influence the population and evolutionary dynamics of vectors, hosts and the parasites transmitted. We studied the role of different factors affecting the species composition and abundance of Culicoides found in nests of the blue tit (Cyanistes caeruleus). We identified 1531 females and 2 males of 7 different Culicoides species in nests, with C. simulator being the most abundant species, followed by C. kibunensis, C. festivipennis, C. segnis, C. truncorum, C. pictipennis and C. circumscriptus. We conducted a medication×fumigation experiment randomly assigning bird's nests to different treatments, thereby generating groups of medicated and control pairs breeding in fumigated and control nests. Medicated pairs were injected with the anti-malarial drug Primaquine diluted in saline solution while control pairs were injected with saline solution. The fumigation treatment was carried out using insecticide solution or water for fumigated and control nests respectively. Brood size was the main factor associated with the abundance of biting midges probably because more nestlings may produce higher quantities of vector attractants. In addition, birds medicated against haemoparasites breeding in non-fumigated nests supported a higher abundance of C. festivipennis than the rest of the groups. Also, we found that the fumigation treatment reduced the abundance of engorged Culicoides in both medicated and control nests, thus indicating a reduction of feeding success produced by the insecticide. These results represent the first evidence for the role of different factors in affecting the Culicoides infracommunity in wild avian nests.

Prochilodus lineatus is a freshwater fish species found in South America. It is common in aquaculture, but few studies regarding diseases of this fish have been performed. This study presents data of the occurrence of Trichodina heterodentata Duncan, 1977, as well as the pathological alterations detected by light and scanning electron microscopy (SEM). Twenty 20-day-old larvae were harvested from an earth pond and examined. Larvae showed erratic swimming on the pond edges and some had a whitish tegument. Larval smears were either impregnated with silver nitrate or stained with Giemsa stain to observe the taxonomic features of the ciliates. Five larvae were fixed in formalin solution for histopathological analysis, and another five specimens were fixed in glutaraldehyde for SEM. All larvae were diagnosed with a severe infestation by trichodinid T. heterodentata. Histological sections showed discrete hyperplasia of the gill filaments with subepithelial oedema of the secondary lamellae. In the SEM, suction areas were observed on the skin, gill and eye; corrosion and ulceration of the fins were associated with the bacterial presence of cocci on the lesions. This is the first report of T. heterodentata in P. lineatus that is responsible for an acute disease that culminates in larval mortality.

The kinetics of low-level repeated infections of Nippostrongylus brasiliensis in the laboratory rat were studied.

The administration of five infective larvae each weekday to the rats produced an infection which was cumulative over 16 weeks and which did not produce an acute host immune response.

The repeated administration of 50 larvae/weekday produced a primary immune response after 14 days. This caused partial worm expulsion and the suppression of egg output but the resistance of these rats to reinfection was not as pronounced as that seen in classical laboratory infections where heavier but less frequent larval exposures are used. The secondary worms that established in these rats did not elicit an acute host immune response even when the worm burden was as high as 756 worms.

It is suggested that the kinetics of this type of infection more closely approximate those found under natural conditions than do those of a ‘classical’ laboratory infection.

We wish to thank Misses G. Merchant, L. Cleaver and J. Cobb for able technical assistance, and Dr B. M. Ogilvie (National Institute for Medical Research, Mill Hill, London) for her helpful comments and discussions.

A short account of the biology and life-cycle of Diplostomum spathaceum is given.

The morphology of the forebody is described in some detail. The lappets are well developed and function as organs of attachment as well as being reservoirs for the secretion from the forebody gland cells. The adhesive organ is variable in form and the muscles facilitating the movements are described in detail. Pressure changes in the excretory system are thought to assist in evaginating the adhesive organ.

The histochemical tests gave the following results. The phosphatases present in the adhesive organ and the forebody gland cells are of the acid variety, the alkaline phosphatase is only present in the cuticle, traces of it occur in the lappets and forebody gland cells. No leucine aminopeptidase activity was observed. The esterase present is either a pseudocholinesterase or a non-specific B-esterase. The presence of RNA is confined to areas of enzyme formation.

The in vitro studies confirmed the absence of alkaline phosphatase and the presence of acid phosphatase and esterase in the forebody. They also showed a secretion of acid phosphatase and esterase to the exterior of the parasite.

Diplostomum spathaceum has very little effect on the host mucosa, but some lysis of the host tissues in contact with the forebody and especially the lappets, is observed. The response of the host to the parasite is likewise very small.

The source of nutrients for D. spathaceum is believed to be the contents of the host alimentary tract, host mucus secretions and to a small extent disintegrated host tissues.

I am very grateful to Dr D. A. Erasmus for advice and encouragement during this study and to Professor J. Brough for his interest and for provision of excellent working facilities. The work was conducted during the tenure of a Rotary Foundation Scholarship for International Understanding and a grant from Nylands Nation (Helsingfors, Finland).

Endotoxin levels were measured in the blood and cerebrospinal fluid (CSF) of control individuals and 2 groups of patients with African sleeping sickness. Endotoxin levels were markedly elevated in the blood (infected groups mean endotoxin values 40·2 pg/ml and 53·8 pg/ml, compared to control 11·6 pg/ml, P < 0·0001 for both increases) and CSF (infected groups mean endotoxin values 45·8 pg/ml and 50·1 pg/ml compared to control 6·3 pg/ml, P < 0·0001 for both increases) of the patients. The levels were reduced 6 weeks following different drug treatments in the 2 groups (blood levels to mean 33·8·pg/ml and 28·5 pg/ml; CSF levels to 37·4 pg/ml and 27·0 pg/ml). The blood endotoxin values correlated with the CSF values before treatment (r = 0·74 and 0·57 for the 2 groups; P < 0·0001 for both) and after treatment (r = 0·57 and 0·56 for the 2 groups; P < 0·0001 for both). It is concluded that raised endotoxin equilibrates in the blood and CSF compartments, and may contribute significantly to the pathology of sleeping sickness.

The effects of each of the known platyhelminth neuropeptides were determined on muscle-strip preparations from the liver fluke, Fasciola hepatica. The activity of synthetic replicates of the C-terminal nonapeptide of neuropeptide F (NPF9, Moniezia expansa), and the FMRFamide-related peptides (FaRPs), GNFFRFamide, RYIRFamide, GYIRFamide and YIRFamide, were examined. Muscle-strip activity was recorded from 1 mm segments of muscle prepared from 28 to 32-day-old worms, using a photo-optic transducer system. None of the peptides (≤ 10 μM) altered baseline tension significantly; however, each of the peptides increased the amplitude and frequency of muscle contraction. The threshold for activity of each of the peptides examined was, respectively, 1 nM (RYIRFamide), 0·3 μM (GYIRFamide and YIRFamide), and 10 μM (GNFFRFamide and NPF9). All of the effects were reversible and repeatable, following wash-out. Muscle-strip integrity was tested following experimentation, using arecoline (10 μM) and high-K+ bathing medium (90 mM K+).

Young and old rediae of Parorchis acanthus Nicoll, from the digestive gland and gonad of Nucella lapillus (L.) have been described. The young redia has an anterior collar-like fold and mid-ventral birth papilla the movements of which are controlled by a special arrangement of muscles. The birth papilla is ‘solid’ but in older rediae is replaced by a pore. The pharynx is of fairly uniform size irrespective of the size of the redia and the intestine, in the young redia, is relatively muchlarger than in the older redia which facts suggest that relatively more food may be absorbed by the mouth in the young stage. The redia cavity develops as a slit in the central cell mass. As it enlarges the intestine remains close to the dorsal wall and developing embryos are carried, among the cells, towards the surface dropping into the cavity, later, to complete their development. Up to fifty-five cercariae may be present in a redia. Simple nervous and excretory systems are present.

The tegument consists of one layer; the surface bears numerous unusual branched microvilli. The syncytial protoplasm contains numerous electron dense mitochondria, vacuoles and granules. Half-desmosomes, not recorded for any other parasitic platyhelminth, occur fairly regularly on the lower limiting layer. Below the uninterrupted basement membrane are circular and longitudinal muscles and, lining the cavity, two or three layers of flattened cells containing numerous mitochondria, agranular and granular endoplasmic reticulum and Golgi complexes. Large lipid globules accumulate in the cells.

It is suggested that, in the older redia, active transport of nutrient materials through the tegument may take place.

1. An analysis has been made of the numbers and location of adult female Sarcoptes scabiei found on 886 men suffering from scabies

2. The average number of mites per man was 11·3. 52% of the cases had under six mites and only 3·6% over fifty.

3. 63% of the mites were found on the hands and wrists, 10·9% on the elbows, 9·2% on the feet, 8·4% on the genitals and 4% on the buttocks.

4. So-called ‘severe’ cases of scabies, showing widespread clinical symptoms, may have very few parasites, whereas cases with few symptoms may have large mite populations.

Adult forms of the pig whipworm, T. suis, are able to establish intimate contact with the host's tissues by the formation of a tunnel-like construction which covers a section of the thread-like oesophageal region. The extreme anterior oral end and the stouter posterior region are not covered and lie free in the lumen of the caecum. The attachment tunnel is composed of host mucosal cells and goblet cell secretion and its possible mode of construction is discussed. Host tissue not directly involved in tunnel formation appears unharmed by the presence of the parasite. T. suis is therefore not a serious pathogen under natural conditions.

It has been demonstrated that characteristic structures of the trichuroid oesophageal region, e.g. bacillary band and stichosome are metabolically active. The former penetrates the layered cuticle in the form of columnar protrusions originating in the hypodermis. Each hypodermal column represents a gland cell or bacifiary cell, which displays enzymic activity, e.g. acid phosphatase, non-specific esterase, glucose-6-phosphatase, succinate dehydrogenase, cytochrome oxidase and β-d-glucosidase. Its possible function at the host-parasite interface and in the metabolism of the whipworm is discussed. The layered cuticle is proteinaceous and enzymically inert.

Glandular activity is also displayed by the stichosome surrounding the capillary-like oesophagus. This evidence confirms earlier suggestions that the stichosome is a series of oesophageal glands.

Although the bacillary band may be involved in nutrient uptake the evidence obtained indicates that this is via the mouth which is favourably placed for the ingestion of mucoid material which was detected in the oesophagus. This may be subjected to preliminary hydrolysis by the enzymes present in the oesophagus and stichosome.

An axenic culture of Giardia was established from a sample of infected intestine obtained following autopsy of a sulphur-crested cockatoo (Cacatua galerita). The cockatoo recently captured in the wild and with good muscle tone died along with several other cage mates, apparently of an overwhelming, acute infection of Giardia. Trophozoites which established in the traditional, axenic Giardia medium (TYI-S-33 with supplementary bile) were morphologically identical to G. duodenalis. When outbred Quackenbush Swiss neonatal mice were infected with trophozoites a chronic infection was established and parasites were still present at 38 days post-inoculation. Weight gain by infected mice was reduced by 20%, thus mimicking failure-to-thrive syndrome in children, and maximum parasite load was more than 3-fold higher in comparison with other G. duodenalis strains. Analysis of the electrophoretic karyotype, rDNA and hybridization studies together with Giemsa- and trichrome-stained samples, and scanning electron microscopy indicated that the bird-derived Giardia belonged to the duodenalis group. This is the first report of infection of mammals with Giardia isolated from a bird. These data may have potentially serious implications for contamination of watersheds and establishment of zoonotic infections.

Comparisons of successful and failed attempts to eradicate livestock ticks reveal that the social context of farming and management of the campaigns have greater influence than techniques of treatment. The biology of ticks is considered principally where it has contributed to control of ticks as practiced on farms. The timing of treatments by life cycle and season can be exploited to reduce numbers of treatments per year. Pastures can be managed to starve and desiccate vulnerable larvae questing on vegetation. Immunity to ticks acquired by hosts can be enhanced by livestock breeding. The aggregated distribution of ticks on hosts with poor immunity can be used to select animals for removal from the herd. Models of tick population dynamics required for predicting outcomes of control methods need better understanding of drivers of distribution, aggregation, stability, and density-dependent mortality. Changing social circumstances, especially of land-use, has an influence on exposure to tick-borne pathogens that can be exploited for disease control.

The aim of this study was to construct risk maps for the presence of the dominant Leishmania infantum vector, P. perniciosus, and check its usefulness (a) to predict the risk of canine leishmaniasis and (b) to define effective leishmaniasis control measures. We obtained data for the presence/absence of P. perniciosus at 167 sampling sites in southern Spain, from which we also took a series of ecological and climate-related data. The probability of P. perniciosus presence was estimated as a function of these environmental variables and generated spatial risk maps. Altitude, land use and drainage hole features (with or without PVC piping) were retained as the only predictors for the distribution of this vector species. Drainage hole features in retaining walls, with or without PVC piping, produce significant variations in the probability of P. perniciosus presence, varying from 2·3 to 91·8% if PVC piping is absent and from 0·4 to 66·5% if all holes have PVC piping. It was concluded that the use of PVC piping in drainage holes could help to reduce leishmaniasis transmission.

Traditionally, the family Campulidae has been associated either with the family Fasciolidae, parasites of ruminants, or the Acanthocolpidae, parasites of fishes, based on morphological similarities. Since morphology does not seem to resolve clearly the problem of the relationships of campulids, we have used the sequences of the 18S rRNA gene of the campulids Zalophotrema hepaticum, Campula oblonga and Nasitrema globicephalae, the fasciolid Fasciola hepatica, the acanthocolpid Stephanostomum baccatum and the outgroup Schistosoma mansoni to infer a phylogeny. Maximum parsimony and neighbour-joining methods were applied. Both methods indicated that campulids are closer to acanthocolpids than fasciolids. In order to confirm this relationship, we generated a second phylogeny using all the partial sequences of the 18S published for trematodes: Lobatostoma manteri, Echinostoma caproni, Calicophoron calicophorum, Tetracerasta blepta, Gyliauchen sp. and Opistorchis viverrini, plus those mentioned above, and Dicrocoelium dendriticum. The aspidogastrean L. manteri was used as the outgroup. Results were identical to the first analysis. According to this and the most recent Digenean phylogeny, which considers campulids and acanthocolpids as sister groups, we suggest that a common origin for these 2 groups would imply a host-switching process. The life-cycle of acanthocolpids includes marine gastropods as first intermediate hosts, and fishes as second intermediate and definitive hosts. In this context, the hypothesis would be that trematodes whose cycle ended in fishes were able to switch to mammalian hosts.