Natural leishmanial infections among feral mammals in the Republic of Panama were studied in relation to gross skin alterations. Three dermatotropic species of Leishmania, L. braziliensis, L. mexicana and L. hertigi, isolated from 230 sylvatic animals of 5 mammalian orders were involved. In 205 (89%) of the cases there were no gross skin alterations. Cryptic infections of all three leishmanial species among wild animals were confirmed by culture and hamster inoculation. This type of infection was always present in the sloths, Choloepus hoffmanni and Bradypus infusatcus, infected with L. braziliensis and in the porcupine, Coendou rothschildi, infected with L. hertigi. Suggestive skin alterations were encountered in 10 (4%) of infected animals. Only 15 (7%) of infected animals exhibited typical leishmanial lesions. It was possible to correlate skin depigmentation with the course of leishmanial infection in one animal, a young kinkajou, Potos flavus.

We investigated the effects of PF4 on Ascaris suum somatic muscle cells using a 2 electrode current-clamp technique. PF4 is a FaRP (FMRFamide-related peptide), originally isolated from the free-living nematode Panagrellus redivivus. PF4 caused hyperpolarization and an increase in chloride ion conductance when it was applied to the muscle cells of the Ascaris body wall. The delay between the application of the peptide and the appearance of the response was measured and compared with that of gamma-amino butyric acid (GABA), a compound that directly gates ion channels, and with PF1, a FaRP that acts via an intracellular signal transduction mechanism. The PF4 and GABA delay times were not significantly different; they were 1·51±0·11 sec and 1·22±0·10 sec respectively. The delay following application of PF1, 3·75±0·51 sec, was significantly longer. The rapid response to PF4 is consistent with direct gating of a chloride ion channel, which has not been described elsewhere in the literature.

A description is given of the following three new trypanosomes from freshwater fishes: (1) Trypanosoma winchesiense sp.nov. of Mirror carp, Cyprinus carpio (variety), obtained in Essex, England; (2) T. batrachi sp.nov. of Clarias batrachus from India, and (3) T. danilewskyi var.nov. saccobranchi of Saccobranchus fossilis from India.

By means of conventional light microscopical and counting procedures, estimations have been made of the average number and size of ovarian balls from unfertilized and fertilized female Moniliformis dubius. The observations were made on worms recovered from experimental primary infections lasting 1, 2, 3, 4, 5, 8, 11, 14, 17 and 20 weeks in male rats. The number of ovarian balls rises to about 6300 per worm, with the maximum being attained more rapidly in unfertilized than in fertilized females. On average more ovarian balls were present in unfertilized than in fertilized females, but a marked decline in number occurred in both groups of worms towards the end of the experimental period. Similarly, on the basis of the area within the elliptical profiles of fixed ovarian balls, it appeared that those from unfertilized females were generally larger on average than those from fertilized worms.

In the winters of 1969 and 1970 a total of 64 rabbits was shot at 11 sites covering diverse climatic regions in the western, central and eastern districts of New South Wales. The ectoparasites of these rabbits were identified and counted. The flea Echidnophaga myrmecobii was most frequently found in western districts; the louse Haemadipsus ventricosus was prevalent in the central districts; the mite Listrophorus gibbus was very abundant on rabbits from the eastern districts, whilst the mite Cheyletiella parasitivorax was prevalent on rabbits from central and eastern districts.

The probable consequences of these variations are discussed in relation to their possible effects on the epidemiology of myxomatosis.

This investigation was carried out as part of the study of the biology of the wild rabbit undertaken by the Division of Wildlife Research, CSIRO, under the general supervision of Mr K. Myers. The author is indebted to P. Haycock and Miss S. Stephens for invaluable technical assistance. Messrs I. Parer, M. Stranger, G. Richards, H. Bults, J. Libke and P. Haycock shot the rabbit samples.

The clinical spectrum of Trichomonas vaginalis infection varies from asymptomatic to mild, moderate or severe vaginitis. Nitric oxide and other reactive nitrogen radicals produced by immune effector cells are important cytotoxic and cytostatic mediators against several microorganisms including parasites. In the present study, inducible nitric oxide synthase (iNOS) and reactive nitrogen intermediates (RNI) were determined in leucocyte cultures (stimulated with T. vaginalis in vitro) and vaginal washes (VWs) of 22 symptomatic and 20 asymptomatic T. vaginalis-infected and 20 healthy women by immunoblotting and Griess method respectively. The iNOS protein was detected in leucocytes and VWs of all the symptomatic and asymptomatic women, but was not detected in any of the samples from healthy women. Mean iNOS protein band intensity was significantly higher in leucocytes as compared to VWs (P<0·001) of both symptomatic and asymptomatic women and was also higher in leucocytes of asymptomatic as compared to symptomatic women (P<0·05). Mean RNI concentration was also significantly higher in leucocytes (P<0·01) and VWs (P<0·05) of asymptomatic as compared to symptomatic women, and was also higher in samples of infected as compared to healthy women (P<0·001). These results suggest that reactive nitrogen radicals may have a role in limiting T. vaginalis infection in asymptomatic women.

Nutritional support of patients with HIV or acquired immune deficiency syndrome (AIDS) has many similarities to other disease states in that the same nutritional products and techniques are used. Some patients with HIV, and many with AIDS without secondary infection, experience a metabolic milieu similar to patients with cancer cachexia. In providing dietary counselling to the HIV patient, we encounter many of the obstacles that must be overcome to improve nutrition in cancer: anorexia, gastrointestinal discomfort, lethargy, and poor nutrient utilization, which limit the ability for nutritional repletion. When a secondary infection is superimposed on HIV, patients resemble more highly catabolic trauma patients or patients in the intensive care unit (ICU), where, despite aggressive efforts to feed, there is usually a net nitrogen wasting leading to the more rapid development of cachexia. However, even in this setting, feeding will limit substantially net catabolism when compared to total starvation. Because the nutritional needs of HIV patients vary greatly, individual strategies have to be designed as the patient moves through the stages of disease. Patients are generally able to consume adequate nutrition either as regular food or dietary supplements during the latency period of viral replication. Once secondary infections become prevalent, artificial diets administered by tube or by vein may be required during the period of active secondary infections, with dietary supplements often helpful during more quiescent periods. Patients with HIV are among the most challenging for clinicians providing nutritional support. Knowledge from treatment of patients with other diseases may be useful, but more data must be gathered on the unique aspects of aetiology and treatment of the anorexia, malabsorption, and ultimate wasting associated with AIDS.

Previous articles in this volume have considered the whole question of parasite vaccines from the immunological point of view. A backcloth of general concepts (Roitt, 1989) and strategies in the viral area (Schild, 1989) precedes consideration of problems specific to parasite vaccines (Mitchell, G. F. 1989). This leads on to reviews of progress to date in the development of vaccines for leishmaniasis (Modabber, 1989), malaria (Mitchell, G. H. 1989) and schistosomiasis (Sher, 1989) and in the development and use of veterinary vaccines (Morrison, 1989). I have been asked in this final chapter to take one step back from all of this and provide the alternative, chemotherapeutic, perspective. The reasons for the request are particularly pertinent, though rarely stated: antiparasite drugs already exist; if parasite vaccines are in fact developed, the way these drugs are used and the whole question of whether or not new ones are required, will have to be reconsidered. It is also a timely one: it is clear that the whole concept of a series of vaccines for the control of parasitic diseases has been so well sold, some would say oversold, that it is impacting on the resolve within the pharmaceutical industry to undertake new chemotherapeutic developments, at a time when this is already under severe strain because of financial considerations (Gutteridge, 1987 a). Hence my title: Parasite vaccines versus anti-parasite drugs: rivals or running mates?. I will try to answer it by, in turn, addressing three key questions. Why are we attempting to develop parasite vaccines? Will we be successful? If we are, will there still be a need for chemotherapy?

Antigenic relationships of 4 stocks of Trypanosoma congolense from different parts of Africa were examined by immunofluorescence (IFAT) and neutralization tests. Antisera to each stock were obtained from rabbits infected with trypanosomes transmitted by Glossina morsitans. Trypanosomes for use as antigens were obtained from local skin reactions developing on rabbits infected with 2 of the stocks. Using the IFAT and antisera at end-point dilutions approximately 40% of the trypanosomes fluoresced strongly and a further 30% less intensely with homologous antisera, indicating antigenic heterogeneity among the trypanosomes developing in the skin. Using antisera at low dilutions some samples gave cross-reactions with trypanosomes of heterologous stocks, but at higher dilutions there were no cross-reactions with either of the antigens. The lack of cross-reactions at high antiserum dilutions was interpreted as indicating antigenic differences between the 4 trypanosome stocks. Using neutralization tests only homologous antisera reduced the infectivity of trypanosome suspensions. Overall, these observations indicated that there were at least 3 different strains of T. congolense among the 4 stocks examined.

1. Infestation of the kidney of M. sowerbii and A. reticulatus by unencysted brachylaemid metacercariae led to a widespread necrosis of the organ. The necrotic debris was ingested into the gut crura of the parasites.

2. M. sowerbii is considered to be a natural intermediate host of the parasite and A. reticulatus to be an unnatural host, because in A. reticulatus parasitization led to a host mortality closely related to the degree of infestation, whereas M. sowerbii withstood the damaging effects of parasitization until the parasites reached maturity.

3. In A. reticulatus the rate of ingestion of food and the rate of egg production were reduced during parasitization.

4. No further effects were observed in either host species.

5. The possibilities and difficulties of using unencysted metacercariae to control pests are discussed.

Morphological and physiological changes that occur during the rehydration of 2nd-stage infective larvae (L2) of Anguina agrostis are described. The first signs of motility, after 2 days of dehydration, were observed 0·5 h after rehydration and 90 % of the nematodes were moving within 15 h. Anabiotic A. agrostis were able to withstand repeated dehydration and rehydration. These procedures caused A. agrostis to accumulate large lipid droplets, which showed most clearly in the tail region. By means of a double labelling technique, it was shown that cuticle permeability of anabiotic L2 of A. agrostis initially increased slightly during rehydration. This was followed by a sharp decrease in permeability between 1 h and 8 h from the start of the experiment. A slower decline in permeability occurred between 8 h and 16 h and little further decrease occurred between 16 h and 24 h. The results are discussed in relation to the possible involvement of the epicuticle.

The mites of the subfamily Trombiculinae are of special importance since, in the larval form, they are reported from many countries to be a nuisance to human beings by the intense irritation caused by their bites. At least two species of these larvae are the acknowledged vectors of scrub typhus (OXK typhus, ‘tsutsugamushi’ or Japanese river fever). The nymph and adult mites are free living and are known to be predatory, feeding upon the collembola and also on the eggs of ants, mosquitoes and collembola. In the larval stage they are found as parasites on mammals, birds, snakes, lizards and frogs. They have also been recorded upon a scorpion and upon three families of grasshoppers.

A method is described for the isolation of high molecular weight DNA from females of potato cyst nematodes. Restriction enzyme analyses of repetitive DNA revealed 30 bands specific for Globodera rostochiensis and 8 bands specific for G. pallida. None of the repetitive DNA bands resolved was common to both species. Hybridization patterns, obtained with a DrosophilaβJ-tubulin probe, revealed 4 common bands, 3 bands specific for G. rostochiensis and 12 bands specific for G. pallida.

Neospora caninum is an apicomplexan parasite and the aetiological agent of bovine neosporosis, one of the main causes of reproductive failure worldwide. We have generated 2 independent transgenic knock-in clones, Nc-1SAG4c1.1 and Nc-1SAG4c2.1, that express the bradyzoite stage-specific protein NcSAG4 in the tachyzoite stage. These clones have similar growth rates in vitro as the wild-type (WT) strain Nc-1. Studies in a cerebral mouse model of infection revealed a slightly lower rate of detection of the transgenic strains in brains during the chronic phase of infection. However, a pregnant mouse model of infection revealed a reduction in the virulence of the Nc-1SAG4c1.1 strain despite the same tachyzoite expression of NcSAG4 and a similar anti-NcSAG4 response displayed by mice inoculated with Nc-1 SAG4c1.1 or Nc-1 SAG4c2.1 parasites. This behaviour may be related to the reduced ability of the Nc-1SAG4c1.1 parasites to invade host cells, which was observed in in vitro assays. The apparent reduction in persistence and the high growth rate of the transgenic strains, together with their constitutive expression of the protein NcSAG4, may be useful features for future immunoprophylaxis trials based on a safe live attenuated vaccine.

Aggregation is one of the distinctive features in parasite-host relationships, which has generally been studied at the level of host communities. Parasite aggregation at the infracommunity level may nevertheless be important for intraspecific interactions such as parasite mating success and opportunities for cross-fertilization. In the present paper, we studied the infracommunity aggregation of 3 highly abundant Dactylogyrus (Monogenea) species occurring on the gills of crucian carp (Carassius carassius). In line with the previous work on monogenean communities, we observed no competition between the species. At the species level, parasites were distributed unevenly on the gills showing aggregation in the majority of infracommunities. However, aggregation decreased with increasing parasite abundance, which supports the hypothesis that less aggregation may be needed to ensure successful mating when the distance to a potential mate decreases with increasing number of conspecifics. Lack of interspecific interactions, species specific site selection and the importance of study scale for aggregation patterns in dactylogyrids are discussed.

Parasites can evolve phenotypically plastic strategies for transmission such that a single genotype can give rise to a range of phenotypes depending on the environmental condition. State-dependent plasticity in particular can arise from individual differences in the parasite's internal state or the condition of the host. Facultative parasites serve as ideal model systems for investigating state-dependent plasticity because individuals can exhibit two life history strategies (free-living or parasitic) depending on the environment. Here, we experimentally show that the ectoparasitic mite Macrocheles subbadius is more likely to parasitize a fruit fly host if the female mite is mated; furthermore, the propensity to infect increased with the level of starvation experienced by the mite. Host condition also played an important role; hosts infected with moderate mite loads were more likely to gain additional infections in pairwise choice tests than uninfected flies. We also found that mites preferentially infected flies subjected to mechanical injury over uninjured flies. These results suggest that a facultative parasite's propensity to infect a host (i.e. switch from a free-living strategy) depends on both the parasite's internal state and host condition. Parasites often live in highly variable and changing environments, an infection strategy that is plastic is likely to be adaptive.

The adult cestode, Hymenolepis diminuta, is essentially anaerobic energetically. Carbohydrate dissimilation results in acetate, lactate and succinate accumulation with succinate being the major end product. Succinate accumulation results from the anaerobic, mitochondrial, ‘malic’ enzyme-dependent utilization of malate coupled to ATP generation via the electron transport-linked fumarate reductase. A lesser peroxide-forming oxidase is apparent, however, fumarate reduction to succinate predominates even in air. The H. diminuta matrix-localized ‘malic’ enzyme is NADP-specific whereas the inner membrane (IM)-associated electron transport system prefers NADH. This dilemma is circumvented by the mitochondrial, IM-associated NADPH→NAD+ transhydrogenase in catalyzing hydride ion transfer from NADPH to NAD+ on the IM matrix surface. Hydride transfer is reversible and phospholipid-dependent. NADP+ reduction occurs as a non energy-linked and energy-linked reaction with the latter requiring electron transport NADH utilization or ATP hydrolysis. With NAD+ reduction, the cestode transhydrogenase also engages in concomitant proton translocation from the mitochondrial matrix to the intermembrane space and supports net ATP generation. Thus, the cestode NADPH→NAD+ system can serve not only as a metabolic connector, but an additional anaerobic phosphorylation site. Although its function(s) is unknown, a separate IM-associated NADH→ NAD+ transhydrogenation, catalyzed by the lipoamide and NADH dehydrogenases, is noted.

Our present genetic data of Acanthocephala, especially the mitochondrial (mt) genomes, remains very limited. In the present study, the nearly complete mt genome sequences of Sphaerirostris lanceoides (Petrochenko, 1949) was sequenced and determined for the first time based on specimens collected from the Indian pond heron Ardeola grayii (Sykes) (Ciconiiformes: Ardeidae) in Pakistan. The mt genome of S. lanceoides is 13 478 bp in size and contains 36 genes, including 12 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs) and two ribosomal RNA genes (rRNAs). Moreover, in order to clarify the phylogenetic relationship of the genera Centrorhynchus and Sphaerirostris, and to test the systematic position of S. lanceoides in the Centrorhynchidae, the phylogenetic analyses were performed using Bayesian inference and maximum likelihood methods, based on concatenated nucleotide sequences of 12 PCGs, rRNAs and tRNAs. The phylogenetic results further confirmed the monophyly of the order Polymorphida and the paraphyly of the order Echinorhynchida in the class Palaeacanthocephala. Our results also challenged the validity of the genus Sphaerirostris (Polymorphida: Centrorhynchidae) and showed a sister relationship between S. lanceoides and S. picae (Rudolphi, 1819).

Schistosome infection is endemic in many Third World countries and affects an estimated 200 million individuals. Over the last few years, a number of investigations have focused on small molecule biomarkers of this infection. These studies were aimed at discovering key molecules relating to the life cycle of the parasite or deciphering metabolic change in the host during infection. In this review these studies are further divided into targeted approaches to find compounds and fingerprinting techniques i.e. metabonomics. A species-specific metabolite or group of biomarkers of the infection have yet to be discovered. For this reason a critical discussion contrasting with established diagnostic methods and future prospects are also provided.