The cutaneous cellular reactions associated with aquisition of resistance by cattle to Hyalomma anatolicum anatolicum feeding were investigated by comparing the nature and sequence of cellular events at H.a. anatolicum feeding sites following primary and tertiary infestations. Cattle acquired resistance to H.a. anatolicum feedings after a single infestation. The resistance was manifested by a significant reduction in the mean weight of engorged females and mean weight of egg mass produced, failure to lay eggs and sometimes death of ticks in situ. The acquisition of resistance corresponded with pronounced epidermal vesiculation and a significant change in the nature of the cellular infiltrate at tick feeding sites indicating the development of cutaneous hypersensitivity. On primary infestation the cellular infiltrate was dominated by neutrophils (43–71%) followed by mononuclear cells (25–35%). Basophil and eosinophil infiltration in small numbers was noticed for the first time at 72 and 144 h, respectively, post-primary infestation. Unlike primary infestation, the dermal infiltrate on tertiary infestation, 24 h after attachment, was characterized by infiltration of basophils (6%) and eosinophils (3%) and a marked degranulation of mast cells and basophils. Basophils showed a consistent increase in absolute as well as relative numbers as the feeding advanced. They were the second most abundant cell types after neutrophils (48–68%) at 72 h (16%), and 144 h (23%). Eosinophils (3–9%) and mononuclear cells also showed a significant increase in their mean numbers as compared with primary infestation. There was a progressive decrease in the number of detectable mast cells following tick infestation and they were significantly lower post-tertiary infestation, compared to primary infestation. These results suggest that the pharmacological mediators released by degranulation of mast cells and basophils are perhaps the major effectors of resistance in cattle to H.a. anatolicum.

Laboratory hamsters (Mesocricetus auratus) were infected with Echinostoma revolutum (Trematoda). Hamsters developed marked and sometimes fatal echinostomiasis. Clinical signs included progressive unthriftiness, watery diarrhoea and weight loss. Packed cell volume, haemoglobin and red blood cell counts increased in those animals with severe diarrhoea. No increase in eosinophils was noted in peripheral blood smears. Examination of tissues of infected animals showed wide individual variations related to the intensity of infection. The histopathological responses of hamsters to the parasite showed erosion of intestinal villi with lymphocytic infiltration being the primary response. Periportal lymphocytic infiltration and focal hepatic necrosis were observed in livers from some infected animals. The findings of this study are discussed in terms of variations in pathogenicity of E. revolutum and as a model for the study of echinostomiasis.

Excretions and secretions (E–S) were collected from a series of developmental stages of Litomosoides carinii maintained in vitro. Measurement of the protein content of E–S obtained from each stage indicates that the rate of production of E–S varies enormously during development of the worm. E–S was iodinated using both Iodogen and the Bolton and Hunter Reagent and was also biosynthetically labelled by incubating worms in the presence of [35S]methionine and [3H]leucine. Attempts to biosynthetically label E–S of mature worms and microfilariae with [3H]glucose were unsuccessful. Examination of radio-isotope labelled E–S by SDS–PAGE revealed that some components were sex specific and that the differences in total E–S production during development were due to the existence of both stage-specific components and components whose rate of release varied during parasite maturation. Antigenic characterization of E–S, carried out by immunoprecipitation in combination with SDS–PAGE, indicated that E–S consists of immunogenic components, a molecule which is probably a non-immunogenic parasite product, and host albumin. The implications of these findings for the construction of diagnostic tests to detect products of human filarial parasites are discussed.

The primary larva of the porocephalid pentastomid Subtriquetra subtriquetra, which infects the nasopharynx of Caiman sclerops, is uniquely free-living. Eggs hatch within the nasal passages and the emergent larvae can remain infective to the fish intermediate host for 4–5 days. During this period larvae exhibit very stereotyped behaviour, alternating between a characteristic stationary ‘fishing’ posture and very brief periods of movement. Larval activity increases significantly at 3 days, probably effecting dispersal to a more favourable site for host invasion. Host location is passive and invading larvae penetrate to the swim-bladder where subsequent larval development, which involves 7 moults, occurs. All 8 larval stages are freely mobile in the swim-bladder and possess hooks. Sensilla, disposed in characteristic patterns, are present throughout development, increasing in number to the infective stage; the majority of sensilla are located on sensory papillae.

Experiments to investigate the linked metabolism of L-serine and L-alanine by Moniliformis moniliformis in vitro were carried out by incubating adult worms aerobically for 3 h at 37 °C in Tyrode’s solution containing L-[U-14C]alanine and other amino acids. When present in the medium alone, alanine was totally removed by the worms and metabolized almost entirely to ethanol and a compound identified as carbon dioxide. When present in the medium with serine and no other amino acids, alanine was largely metabolized as before but additional alanine, believed to originate from serine, was excreted. The same results were obtained with serine and 16 other amino acids in the incubation medium.

Monthly samples of the leeches Erpobdella octoculata, Glossiphonia complanata and Helobdella stagnalis were taken over a two-year period from an eutrophic, English lake to detect metacercariae of the trematode, Apatemon gracilis. In each cohort of each of the three leeches, prevalence was low in young individuals, rose to a peak in autumn/winter, and then declined until the cohort had almost died out; in E. octoculata and H. stagnalis a final brief increase occurred. Mean intensity and relative density values followed a similar seasonal pattern of change to that of prevalence in these last two species, but in G. complanata values fluctuated irregularly with no distinct pattern. The frequency distribution of the parasite in G. complanata was highly over-dispersed, but less so in the other two species. Infected E. octoculata reached sexual maturity. The parasite reduced egg production in G. complanata and H. stagnalis, but only by maximum values of 2·5 and 9% respectively. This reduction in fecundity is low compared to the subsequent high mortality, at 95% or more, of newly recruited young from as yet unidentified causes. Parasite-related host mortality was difficult to assess in young leeches, but there was some evidence for its occurrence in older leeches of E. octoculata and H. stagnalis. However, this is unlikely to play a prominent role in the control and regulation of lacustrine leech populations.

Cultured metacyclic forms of Trypanosoma congolense display a characteristic repertoire of metacyclic variable antigen types (M-VATs) similar to that exhibited in vitro in the tsetse fly. There appeared to be no change in expression of M-VATs in cultures of two stocks of T. congolense even after several passages, cryopreservation or long-term cultivation in vitro. Metacyclic forms transformed into mammalian forms when transferred to cultures of bovine aorta endothelial cells and whilst one stock retained expression of M-VATs without change even after 4 months, the other stock underwent antigenic variation within 14 days of transfer. Analysis of the M-VAT composition of mammalian forms of this stock using monoclonal antibodies showed that although the proportion of mammalian forms expressing certain M-VATs declined considerably, trypanosomes expressing one M-VAT increased proportionally to comprise 50 % of the population. In contrast, only small changes were seen in antigen expression in cultures of metacyclic trypanosomes from which mammalian-form cultures were derived. It was possible to produce in vitro, loss and reacquisition of variable antigen surface coat, similar to the differentiation process occurring when bloodstream trypanosomes are ingested by the tsetse fly and eventually develop into metacyclic forms.

Female Tenebrio molitor infected with metacestodes of Hymenolepis diminuta exhibit elevated concentrations of female-specific proteins in their haemolymph and the origin of these has been investigated. Following a 4 h in vitro incubation with [14C]leucine, fat bodies from non-infected females secreted 13 times more protein than those from females 12 days post-infection. A comparison of the uptake in vivo of radio-isotope labelled amino acids by ovaries from non-infected and infected beetles of various ages revealed no differences; however, a 51·5% decrease in protein sequestration was detected in females 12 days post-infection. Electrophoresis of homogenates of radio-isotope labelled ovaries demonstrated that the majority of label was associated with vitellin sub-units. It is suggested that the decrease in vitellogenin sequestration associated with infection results in an increase in the haemolymph concentration of these proteins despite a concomitant reduction in their secretion by fat bodies. Both fat body synthesis and ovarian sequestration are under juvenile hormone control and it is proposed that metacestodes of H. diminuta may cause a reduction in the concentration of this hormone in the intermediate host.

An instrument for measuring the motility of larval and adult nematodes is described along with an analysis of its use as a tool to analyse drug action on these parasites. Motility was detected from larval parasites of Nippostrongylus brasiliensis and Ascaris suum in the absence and presence of various anti-nematodal drugs. These agents produced, within 48 h, a significant decrease in larval parasite motility. The instrument was also capable of detecting the motility of Caenorhabditis elegans, adult female Brugia pahangi and their response to anti-nematodal drugs. The design of the instrument allows us to accurately measure motility in a single sample within 60 sec.

An in vitro anthelmintic primary screen in which the effects of compounds on the aggregation response of newly moulted adult worms of Trichostrongylus colubriformis was monitored is described. Representatives of all the major classes of the anti-trichostrongyle anthelmintics all inhibited worm aggregation completely when present in the culture medium either at or at less than micromolar concentrations. The screen proved highly selective for these broad-spectrum agents, much higher concentrations of the narrower spectrum anthelmintics, active only against blood-sucking nematodes, trematodes and/or cestodes, having little or no effect on this response. This in vitro assay, based solely on the occurrence or absence of worm aggregation following the final moult in culture, proved very easy to interpret rapidly and accurately. It can be recommended therefore for the primary mass screening of synthetic compounds or natural products for intrinsic activity against the trichostrongylid helminths of ruminants.

Protoscoleces of Echinococcus granulosus were incubated in a 10 μm solution of monensin and their viability and the ultrastructure of their tegument were monitored over a 36 h period. The earliest effects of the lonophore, apparent within 15 min, involved a degree of cisternal swelling of the tegumentary Golgi complexes. Swelling became more pronounced with time and cytons eventually contained numerous large electron-lucent vesicles. Residual bodies indicative of autophagy were observed in the cytons and distal cytoplasm from 1 h onwards. All movement of protoscoleces ceased after 1 h and the surface of the soma subsequently became folded, possibly suggesting spastic paralysis. Later, vacuoles and large cytoplasmic blebs were observed in the distal cytoplasm and viability dropped rapidly after 12 h. All protoscoleces were dead at 36 h. The potential of monensin as an in vivo protoscolicidal agent is discussed.

Faecal blood loss was measured during Nippostrongylus brasiliensis infection in the DA rat using 51Cr-labelled red blood cells (r.b.c.s). In an initial study, faecal blood loss was measured on day 7 of primary infection with 3000 larvae administered subcutaneously (s.c), and found to be 0·03 ml/24 h in uninfected animals and 0·14 ml/24 h in infected animals. In a further experiment, blood loss was measured on the day before infection and for 13 days after primary s.c. infection with 5000 larvae. Faecal blood loss was 0·05 ml/24 h or less until day 3, began to rise from day 5, reached a peak of 0·51 ml/24 h on day 8, and fell until day 13. This was closely associated with the rise and fall of the pooled faecal egg count. Direct worm count confirmed a high worm burden on day 7 and expulsion by day 14. The effect of the worm burden on the haemoglobin concentration (Hb) was measured in a further experiment and showed a fall in Hb with a mean worm burden of 726 compared to that of 47 or 284 worms. The study concluded that there is minimal background blood loss in uninfected rats but that infection with N. brasiliensis is a cause of intestinal blood loss and this is associated with a fall in Hb concentration that is dependent on the worm burden.

Isometric tension recordings and the single sucrose-gap technique were used to record mechanical and electrical activity from Grillotia erinaceus metacestodes in vitro. Both complete preparations and those cut longitudinally (to allow access of the bathing medium to the region of the somatic muscle) showed spontaneous contractions of frequency ≃ 1/min in Hanks’ Balanced Salt Solution (HBSS) at 13 °C. Changing the pH, temperature or osmolarity of the HBSS did not improve the activity but rather abolished it at extremes of these variables, so confirming the adequacy of the experimental environment for further work. The neurotoxin tetrodotoxin (TTX; 3 × 10−6 M) failed to abolish or modify these spontaneous contractions although excitatory and inhibitory responses to 5-hydroxytryptamine (5-HT) and acetylcholine (ACh) respectively were demonstrated. Electrical recordings showed that spontaneous contractions were mediated by slow membrane depolarizations upon which spike-like potentials were often superimposed. 5-HT was shown to mediate its excitatory effect via membrane depolarization and an increase in the frequency of both slow depolarization and spikes. In contrast, inhibition by ACh was accompanied by membrane hyperpolarization and loss of all regenerative electrical activity. Electric field stimulation of the preparation using a range of stimulus parameters failed to demonstrate a functional motor innervation to the somatic muscle.

Isometric tension recordings and the single sucrose-gap technique were used to record mechanical and electrical activity of somatic muscle from G. erinaceus metacestodes in vitro. Praziquantel (≥ 10−6 M) raised baseline tension and largely abolished spontaneous fluctuations in tension. The effect of the drug was critically dependent on the presence and availability of calcium in the bathing medium. In calcium-free solution or in the presence of manganese or lanthanum (10 mm) praziquantel failed to induce a rise in baseline tension. Electrical recordings of somatic muscle activity showed the action of praziquantel to be accompanied by membrane depolarization and loss of slow depolarizations and spikes. Tegumental membrane potential, as measured by microelectrodes, was not affected by the drug. These results suggest that in vitro praziquantel causes contraction of the somatic muscle of G. erinaceus by membrane depolarization and influx of extracellular calcium.

The development and hatching of Ancylostoma ceylanicum and Ancylostoma tubaeforme eggs in a range of potentially inimical solutions has been examined using time-lapse video micro-recording techniques. In all compounds tested the larvae developed to the active pretzel stage. The inception of activity resulted in an increase in shell permeability to water and small molecules. In anthelmintics of molecular weight (Mr) 400 development continued normally until about the time that control eggs hatched, when there was a marked decrease in larval activity and eclosion did not occur. The addition of a low Mr surface-active agent potentiated the effect of the anthelmintic and caused larval activity to be lost earlier. The calcium inhibitor lanthanum chloride affected larval development rather than eclosion. Large Mr compounds did not affect either development or hatching and the results suggest that the egg-shell may act as a form of sieve, allowing the essential oxygen to reach the developing larva while excluding large potentially dangerous molecules. No appreciable differences were found between the two species of hookworm examined.

A comparative study has been made of the progress in the control of ovine echinococcosis caused by Echinococcus granulosus and the ovine cysticercoses caused by Taenia hydatigena and T. ovis in New Zealand. The methods of control included an educational and a dog-dosing programme. In the Styx field trial, the Otago/Southland Surveillance Programme and the national control programme, E. granulosus declined towards extinction. In contrast, this same control effort transformed the cysticercoses from hyper-endemic to endemic status with focal epidemics. In this unstable state, the density-dependent constraint was negligible and superinfection occurred.

The life-cycle of Haemonchus contortus, a pathogenic stomach nematode of sheep, is typical of those of the other members of the superfamily Trichostrongyloides, all of which require a period of development outside the definitive host. Classically, gravid H. contortus, known as strictly oviparous, releases her eggs into the abomasal lumen. The eggs are passed out in the faeces in which they hatch into the 1st-stage larvae and then develop into the infective 3rd-stage larvae. We have developed a method to study the fate of eggs within gravid worms. Using this procedure, we have shown that H. contortus may also exhibit viviparity with apparently normal development from the egg to the 4th larval stage taking place within the gravid female maintained in vitro. On the basis of these observations we speculate that viviparity might occur in vivo with consequent autoinfections; if so, this might explain some puzzling clinical and epidemiological features of haemonchosis, as well as the incomplete efficacy of current control measures.

Golden hamsters infected with Spirometra erinacei plerocercoids develop a hypertriglyceridaemia characterized by an increase in very low-density lipoprotein. Acyl-CoA synthetase activity, the rate of fatty acid synthesis in the liver and triglyceride production studies showed that the activation and synthesis of fatty acid and production of triglyceride in plerocercoidinfected hamsters were not significantly different from the controls. Lipase activity in post-heparin plasma was found to be suppressed in plerocercoid-infected golden hamsters. The presence of plerocercoids also resulted in a significant reduction in serum thyroxine, but the hypertriglyceridaemia associated with plerocercoid infection was not reversed by injecting the infected hamsters with 2 μg/ day doses of L-thyroxine. The levels of serum immunoreactive insulin in plerocercoid-infected hamsters were not significantly different from the controls. We conclude that the hypertriglyceridaemia, associated with plerocercoid infection in hamsters, results predominantly from a suppression of triglyceride degradation, and that the suppression of lipase activity is probably not the result of hypothyroidism or the lack of insulin, but the result of secretion of growth hormone-like substances.

Adult Wuchereria bancrofti were recovered from infected Presbytis cristatus monkeys and radio-isotope labelled extrinsically with 125I and in vitro with [35S]methionine. 125I labelling of the surface of adult W. bancrofti permitted a comparison between the major surface antigens of this species and those from the related lymphatic filariae, Brugia malayi and B. pahangi. All species bear a prominent Mr 29 000 surface antigen but among the differences observed were the strongly labelled molecules with Mr 58 000 and 67 000 in W. bancrofti which are extremely faint in the Brugia species. The [35S]methionine label was effectively incorporated into somatic parasite proteins in vitro although it was not possible to identify any secreted proteins in this way. The antigenicity of these products was investigated using a variety of sera from homologous and heterologous infections and the immunoprecipitation patterns highlighted particular differences between somatic proteins of male and female worms. One secreted antigen was detected, however, by virtue of its phosphorylcholine epitopes, in the culture medium of mixed adult worms; medium from male W. bancrofti adults was negative although homogenates of either sex of adult W. bancrofti were strongly positive in the same system.

The actinomycete, Pasteuria penetrans, is a specific endoparasite of various plant-parasitic nematodes. When parasitizing the root-knot nematode (Meloidogyne javanical) the nematode's capacity to reproduce is destroyed and feeding on and stimulation of the plant host are unaffected even though the bulbous body of the female nematode becomes filled with spores. Parasitism by the actinomycete does not alter the rate of growth in the early stages of nematode development although the non-parasitized female grows more rapidly than the parasitized one for a short time immediately after the final moult. Pasteuria did not invade or inactivate the anterior oesophageal region of the female Meloidogyne or influence the morphology of the giant cells induced by these nematodes in their hosts' roots. The influence of this parasite on the developmental physiology of its nematode host is discussed.