Prototheca richardsi, an unpigmented heterotrophic alga, causes growth inhibition in amphibian larvae and has proved refractory to culture in Vitro. P. richardsi replication is dependent on regular passaging through tadpole digestive systems; uptake of thymidine by free-living Prototheca cells and incorporation into DNA are very low by comparison with leucine uptake and incorporation into protein, but DNA synthesis is detectable in cells isolated from tadpole intestines. DNA replication was elicited 6–8 h after ingestion in protothecans fed to tadpoles and subsequently re-isolated from them, providing that the tadpoles were fed subsequent to the ingestion. It appears that passaging through tadpole intestines provides an essential stimulus to maintaining an active cell division cycle in P. richardsi.

At the request of Prof. G. H. F. Nuttall, F.R.S., the writer has attempted to put together a few notes on methods found useful in obtaining well-preserved specimens for helminthological purposes. Of the large number of methods that have been recommended for the various groups by different authorities, only a limited selection can be given, and preference is given, where possible, to those which are comparatively simple and can be employed in the field or under the limited conditions of a field laboratory, while at the same time experience has shown them to give sufficiently good results for ordinary purposes.

In conclusion, the following comments may prove suggestive:

Out of fifty-five vials of the Chinese cestodes from Charadriiform birds, fifteen have not been determined definitely, owing to the poorly preserved condition and to insufficient material for detailed study, such as Pe 510, Pe 517, Pe 526, Pe 529, Pe 552 b, Pe 588, Pe 593, Pe 1466, Pe 735 c, Pe 1431 d, Pe 760, Pe 144 b, Pe 151, Pe 848 and Pe 841 d.

In this paper, seven species are described as new, namely, Amoebotaenia fuhrmanni, A. pekinensis, Monopylidium guiarti, Choanotaenia joyeuxi, Haplo-paraxis sinenis, Fuhrmanniella clerci, and Gyrocoelia fausti.

The present study indicates, to a certain extent, that the Chinese fauna of the avian cestodes is more or less related to that of the Ural, Australia, Egypt and Europe.

Pe 848 is an interesting tapeworm recorded from the liver of Totanus calidris. Owing to the poor preservation, the strobilae can not be examined, but its incomplete rostellar hooks, larger 0·0234 mm., and smaller 0·0216 mm. shown in Fig. 54, are characteristic.

Trypanosoma brucei is unusually reliant on mRNA-binding proteins to control mRNA fate, because its protein-coding genes lack individual promoters. We here focus on three trypanosome RNA-binding proteins. ZC3H22 is specific to Tsetse fly forms, RBP9 is preferentially expressed in bloodstream forms; and DRBD7 is constitutively expressed. Depletion of RBP9 or DRBD7 did not affect bloodstream-form trypanosome growth. ZC3H22 depletion from procyclic forms caused cell clumping, decreased expression of genes required for cell growth and proliferation, and increased expression of some epimastigote markers. Apart from decreases in mRNAs encoding enzymes of glucose metabolism, levels of most ZC3H22-bound transcripts were unaffected by ZC3H22 depletion. We compared ZC3H22, RBP9 and DRBD7 RNA binding with that of 16 other RNA-binding proteins. ZC3H22, PUF3 and ERBP1 show a preference for ribosomal protein mRNAs. RBP9 preferentially binds mRNAs that are more abundant in bloodstream forms than in procyclic forms. RBP9, ZC3H5, ZC3H30 and DRBD7 prefer mRNAs with long coding regions; UBP1-associated mRNAs have long 3′-untranslated regions; and RRM1 prefers mRNAs with long 3′or 5′-untranslated regions. We suggest that proteins that prefer long mRNAs may have relatively short or degenerate binding sites, and that preferences for A or U increase binding in untranslated regions.

The present study characterized the biological function of the asparaginyl peptidase legumain-1 (LEG-1) of the bovine lungworm Dictyocaulus viviparus and its suitability as a recombinant vaccine against dictyocaulosis. Quantitative real-time PCR and immunoblot analysis revealed LEG-1 to be almost exclusively transcribed and expressed in parasitic lungworm stages. Immunohistochemistry localized the enzyme in the parasite's gut, which was confirmed by immunoblots detecting LEG-1 in the gut as well as male testes. LEG-1 was recombinantly (rLEG-1) expressed in the yeast Pichia pastoris and subsequently analysed in activity assays for its enzyme functions and substrate specificity. For sufficient functionality, rLEG-1 needed trans-activation through D. viviparus cathepsin L-2, indicating a novel mechanism of legumain activation. After trans-activation, rLEG-1 worked best at pH 5·5 and 35–39 °C and cleaved a legumain-specific artificial substrate as well as the natural substrates bovine collagen types I and II. In a clinical vaccination trial, rLEG-1 did not protect against challenge infection. Results of in vitro characterization, transcription pattern and localization enhance the presumption that LEG-1 participates in digestion processes of D. viviparus. Since rLEG-1 needs trans-activation through a cathepsin, it is probably involved in an enzyme cascade and therefore remains interesting as a candidate in a multi-component vaccine.

Three species of two-clawed Mallophaga have heretofore been recorded from South American mammals. Concerning one of these species, Menopon extraneum Piaget, nothing is known aside from the information included in the original description and, judging from this and the accompanying figure, it appears not to differ from the usual type of bird-infesting members of this group. The other two species have each been made the type of a genus and these two genera have been considered by Harrison as representing a well-marked family, the Trimenoponidae.

Scientific evidence strongly suggests that parasites are directly or indirectly associated with carcinogenesis in humans. However, studies have also indicated that parasites or their products might confer resistance to tumour growth. Plasmodium protozoa, the causative agents of malaria, exemplify the ambivalent link between parasites and cancer. Positive relationships between malaria and virus-associated cancers are relatively well-documented; for example, malaria can reactivate the Epstein-Barr Virus, which is the known cause of endemic Burkitt lymphoma. Nevertheless, possible anti-tumour properties of malaria have also been reported and, interestingly, this disease has long been thought to be beneficial to patients suffering from cancers. Current knowledge of the potential pro- and anti-cancer roles of malaria suggests that, contrary to other eukaryotic parasites affecting humans, Plasmodium-related cancers are principally lymphoproliferative disorders and attributable to virus reactivation, whereas, similar to other eukaryotic parasites, the anti-tumour effects of malaria are primarily associated with carcinomas and certain sarcomas. Moreover, malarial infection significantly suppresses murine cancer growth by inducing both innate and specific adaptive anti-tumour responses. This review aims to present an update regarding the ambivalent association between malaria and cancer, and further studies may open future pathways to develop novel strategies for anti-cancer therapies.

The aim of the study was to investigate the effect of a low-level primary infection of Schistosoma japonicum on a challenge infection in pigs. Groups of pigs were given either light or heavy primary infections and heavy challenge infections 14 weeks later. One group of pigs served as a challenge control group. Challenge infection superimposed on the heavily infected pigs did not result in increased worm burden, faecal and tissue egg counts or IgG levels. In contrast, the challenge infection established fully when superimposed on the light primary infections. However, neither faecal egg counts nor the IgG levels increased, and the amount of liver pathology, as judged by septal fibrosis, did not increase either, as compared to the challenge control group. These results suggest that pigs are not able to mount an effective anti-worm response to reinfection when the primary infection is low. However, some modulation of the infection takes place, possibly as a result of an anti-embryonation effect. Collagen content in the liver was found to be relatively insensitive as a marker for liver pathology, as judged using portal and septal fibrosis as a criteria.

In previous studies, ultrastructural observations revealed a large number of gap junctions (GJs) in the neck and immature proglottid tissues of Taenia solium tapeworms. In these helminths, cytoplasmic glycogen sacs are connected by numerous discrete GJs to other cells throughout the maturing strobilar tissue. Discontinuous sucrose gradients were used to purify membrane fractions containing GJs, which were identified by ultrastructural analysis. A trans-membrane peptide sequence from a highly conserved innexin region was used to construct a 20-amino acid synthetic peptide and used to raise polyclonal antibodies in rabbits that recognized both a 55 and a 67 kDa protein in a Western blot of the GJ-enriched pellet. Immunohistochemistry of larval and adult worm sections incubated with antiserum to the synthetic peptide and a secondary anti-rabbit IgG bound to fluorescein, revealed strong binding to the tegumentary surface of the worm, as well as patchy fluorescent areas in the parenchyma. The results indicate that both the tegument of cysticerci and adult T. solium contain innexin-rich membranes, which may function as a tegumentary transport system for small molecules.

Attempts to repeat the isolation of an ecdysone-like steroid from Biomphalaria glabrata revealed that some of the manipulations described by Muftic (1969) were physically impossible to repeat. With modified procedures no ecdysone-like steroid was found. The original publication gives scant attention to certain experimental details. Some sections of the text bear very close resemblance to earlier publications by different authors. The amount of substance claimed to have been isolated, and the long survival period claimed for Schistosoma mansoni larvae in vitro, are claims which, amongst others, seem highly unlikely a priori. All attempts to contact Muftic have proved to be futile. It is suggested that the paper is, at least in part, erroneous and that any future reference to it should clearly indicate its suspected invalidity.

Despite these results, it is considered likely that future investigations will demonstrate physiological roles for steroids in snails.

I wish to acknowledge the stimulating communications of Drs E. L. Hansen, M. Voge, R. E. Thorson, C. S. Richards, J. N. Kaplanis, G. Nace, R. Monroe, and of E. Chernin, who first brought this matter to my attention. Theanalytical steroid work could not have been done nor interpreted without the considerable time and effort willingly given by Drs F. Kohen and R. Counsell of the University of Michigan College of Pharmacy. My snail populations were supplemented with snails from the tanks of Mrs B. Caveny. Technical help was given by E. Perisho, G. Lindsay and P. LoVerde. Financial support was kindly provided by Dr J. B. Burch. This investigation was supported in part by the United States-Japan Cooperative Medical Science Program administered by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, Department of Health, Education and Welfare, grant N.I.A.I.D. AI-7364, and in part by NSF grant GB-29315. Improvements were made to the first draft of the manuscript after it was critically read by Drs E. L. Hansen, F. Kohen, M. Voge, E. Chernin, R. E. Thorson and J. N. Kaplanis.

The cidal properties of some phenolic, halogenated diphenyl, salicylanilide, benzimidazole and diaminophenoxyalkane anthelmintics, against 6-week-old worms of Fasciola hepatica were assessed in vitro. In a conventional fluke culture medium containing RPMI 1640, supplemented with serum with or without rabbit erythrocytes or pink-ghosts, only the halogenated diphenyl and salicylanilide compounds showed activity at concentrations equal to or less than 100 μm. However, when basal, serum and cell-free RPMI 1640 was used, all compounds other than diamphenethide were highly active, their minimum lethal concentrations being some 25–125 times lower under these conditions. The inclusion of rabbit liver microsomes in the basal culture medium resulted in diamphenethide exhibiting cidal activity equivalent to that seen when its free-amine active metabolite was assayed. The possibility that the activity of many of these compounds was masked in vitro because of their serum binding properties is discussed. Recommendations are made that in vitro screens for new fasciolicides should be carried out in serum-free medium and that additional replicates containing mammalian liver microsomes and liver cytosolic extracts be included as means for the metabolic activation of certain otherwise undetectable prodrugs.

Reinfection of the insects Tenebrio molitor and Schistocerca gregaria by the Eugregarines Gregaria polymorpha and G. garnhami respectively is not caused by the retention of the gametocyst and the release of sporocysts inside the gut. The gametocyst has to pass out from the insect gut, dehisce, and the sporocysts have to be ingested in order for reinfection to occur. Thus it is possible to stop reinfection by preventing the host from ingesting sporocysts. The development of spore ducts on the gametocyst of G. garnhami is inhibited if the gametocysts are prevented from leaving the hindgut of the locusts.

I would like to thank Professor L. H. Finlayson for his advice for many helpful discussions.

A sizeable proportion of households is forced to share single long-lasting insecticide treated net (LLIN). However, the relationship between increasing numbers of people sharing a net and the risk for Plasmodium infection is unclear. This study revealed whether risk for Plasmodium falciparum infection is associated with the number of people sharing a LLIN in a holoendemic area of Kenya. Children ⩽5 years of age were tested for P. falciparum infection using polymerase chain reaction. Of 558 children surveyed, 293 (52.5%) tested positive for parasitaemia. Four hundred and fifty-eight (82.1%) reported sleeping under a LLIN. Of those, the number of people sharing a net with the sampled child ranged from 1 to 5 (median = 2). Children using a net alone or with one other person were at lower risk than non-users (OR = 0.29, 95% CI 0.10–0.82 and OR = 0.47, 95% CI 0.22–0.97, respectively). On the other hand, there was no significant difference between non-users and children sharing a net with two (OR = 0.88, 95% CI 0.44–1.77) or more other persons (OR = 0.75, 95% CI 0.32–1.72). LLINs are effective in protecting against Plasmodium infection in children when used alone or with one other person compared with not using them. Public health professionals should inform caretakers of the risks of too many people sharing a net.

This paper records two new species of Amplicaecum from Malayan amphibians for which the following names are proposed: Amplicaecum communis sp.nov. and A. sandoshami sp.nov. A. communis is a common parasite in a number of Malayan amphibians, but A. sandoshami has been found only in Megophrys sp.

Genome sequencing has greatly contributed to our understanding of parasitic protozoa. This is particularly the case for Cryptosporidium species (phylum Apicomplexa) which are difficult to propagate. Because of their polymorphic nature, simple sequence repeats have been used extensively as genotypic markers to differentiate between isolates, but no global analysis of amino acid repeats in Cryptosporidium genomes has been reported. Taking advantage of several newly sequenced Cryptosporidium genomes, a comparative analysis of single-amino-acid repeats (SAARs) in seven species was undertaken. This analysis revealed a striking difference between the SAAR profile of the gastric and intestinal species which infect mammals and one species which infects birds. In average, total SAAR length in gastric species is only 25% of the cumulative SAAR length in the genome of Cryptosporidium parvum, Cryptosporidium hominis and Cryptosporidium meleagridis, species infectious to humans. The SAAR profile in the avian parasite Cryptosporidium baileyi stands out due to the presence of long asparagine repeats. Cryptosporidium baileyi proteins with repeats ⩾20 residues are significantly enriched in regulatory functions. As postulated for the related apicomplexan species Plasmodium falciparum, these observations suggest that Cryptosporidium SAARs evolve in response to selective pressure. The putative selective mechanisms driving SAAR evolution in Cryptosporidium species are unknown.

Before describing my further results in the treatment of canine piroplasmosis by aniline dyes, I desire to mention some earlier experiments, carried out by Italian investigators whose papers have until recently escaped my attention. The results of the Italian experiments are cited in considerable detail with a view to making it unnecessary for other workers to refer to the original papers which may be difficult of access. It is well to note that the authors in question give very little information concerning their experiments; thus Memmo, Martoglio and Adani are satisfied with giving mere clinical notes, whilst Levi della Vida omits a number of essential data from his protocols.

The modern history of the group of parasites of which this paper relates begins with the unfortunate publication on the same day—December 28th, 1899—of two simultaneous revisions of the Trematoda by Looss and Lühe, which has led to endless confusion and difficulties of nomenclature. In the present instance both writers described new genera under the same name—Telorchis—placing in each somewhat similar assemblages of species, yet not sufficiently close in character to be accepted as synonymous genera; at the same time each writer wisely selected a type species and thereby rendered the task of unravelling this knot in systematics very easier. The position will be at once apparent on comparing the two descriptions, and in order to facilitate this I have rearranged the translated clauses of each so that they appear in the same order:

A laboratory strain of Eimeria acervulina was found to develop in the caeca when large numbers of excysted sporozoites were injected into that organ. Both schizonts and gametocytes were formed, but parasitization of the caeca was never heavy and did not increase with serial passage. The infection was not increased by the simultaneous injection of betamethasone.

Populations of Pseudodiplorchis americanus infecting the desert toad, Scaphiopus couchii, have previously been shown to be remarkably stable from year to year, despite wide variation in conditions promoting invasion. The present study aimed to document the survival of both first-year and pre-existing adults under controlled laboratory temperatures. First-year worm survival in experimentally infected toads was shown to be very high for the first 5 months after migration to the definitive site, and there was no difference in survival at 25 °C or 15–20 °C. There was also no density-dependent survival during the same period: 20% of worms were recovered from the host urinary bladder, irrespective of initial intensities. After the first 5 months, there was a progressive loss of worms in toads maintained at 25 °C but not at 15–20 °C. Pre-existing adult populations were shown to be virtually identical to those under natural conditions for the first 4 months after toad capture. Following this, at 25 °C, populations declined and no pre-existing adults were recovered after 11–14 months. There was no such loss of pre-existing adults at 15–20 °C for up to 14 months. A diurnal temperature cycle of 20–34 °C (simulating temperatures during the desert summer) did not lead to a significant loss of worms. These observations suggest that during one annual cycle in the desert, when temperatures remain above 20 °C for less than 6 months, most adult worms established in the host urinary bladder will survive to the next transmission opportunity. However, the similar longevity of first-year and pre-existing adults in laboratory maintained toads shows that loss of worms cannot be due solely to parasite ageing. Temperature-dependent survival of P. americanus is suggestive of a host immune response. Low temperatures, which inhibit parasite growth and development, are essential for the survival of P. americanus.

On comparing the figures it will be observed that all the specific characters of Tetrophthalmus titan (A in all figures) closely resemble those of T. subtitan (B in all figures), and that these two species constitute one group; also that the specific characters of T. africanus (C in all figures) closely resemble those of T. australis (D in all figures), and that these species belong to another group, which must also include T. chilensis.

Judged by their parasites, the Ethiopian pelican, Neopelecanus rufescens, is more closely allied to both the Australian pelican, Catoptropelecanus conspicilatus, and the South American species, Pelecanus thagus, than it is to either Pelecanus onocrotalus or Metapelecanus roseus, both of which also occur in the Ethiopian region. Moreover, if the parasites throw any light on the phylogeny of their hosts, thagus cannot remain in the genus Pelecanus along with onocrotalus if the genera Neopelecanus, Metapelecanus and Catoptropelecanus are to remain valid.