History. Trypanosomes have been cultured from the blood of cattle in many parts of the world; in Germany, Denmark, Greece, Holland, France, Russia, Japan, the Philippines, Siberia, Algeria, Tunis, the United States and Brazil. But in only a few cases have the actual parasites been found in the circulating blood. From the scanty literature at my disposal, but especially from the Sleeping Sickness Bulletin, I find that the following observers have found and described the trypanosomes in the blood.

Nematodes of the superfamily Rhabditoidea are usually free-living; however, a few species appear to be definitely parasitic. The Nematode described in this paper belongs to the latter group. It was found in large numbers in the small intestine of one of two bats, Lasiurus borealis, captured September 15th, 1932, in the vicinity of Washington, D.C. Additional specimens of this species of bat were not obtained for examination. Two specimens of each of two other species of bats, Eptesicus fuscus and Nycticeius humeralis, collected from the same locality were negative for this parasite. The Nematode is a member of the family Cylindrogasteridae Chitwood 1933, and appears to be congeneric with Longibucca vivipara Chitwood 1933, found in the wall of the stomach of a South American snake, Pseudoboa cloelia.

Non-random assemblages have been described as a common pattern of flea co-occurrence across mainland host species. However, to date, patterns of flea co-occurrence on islands are unknown. The present work investigates, on one hand, whether the decrease in the number of species on islands affects the pattern of flea co-occurrence, and on the other hand, how the cost of higher flea burdens affects host body mass. The study was carried out in the Canary Islands (Spain) using null models to analyse flea co-occurrence on Rattus rattus and Mus musculus. Results supported aggregation of flea species in Mus but not in Rattus, probably due to the relationship between abundance and both prevalence and intensity of infection of the main flea species parasitizing Mus. In addition, heavy individuals of both rodent species showed the highest flea burdens as well as higher species richness, probably due to the continued accumulation of fleas throughout life and/or immunological resistance mechanisms. Whatever the mechanisms involved, it is clear that co-occurrence and high parasite intensities do not imply a detrimental biological cost for the rodents of the Canary Islands.

Jameson (1926) has described from the caeca of cattle a ciliate belonging to the family Isotrichidae to which he has given the name Buxtonella sulcata. The most prominent character of this ciliate is a dorsal ridge running in a wide sweeping curve from one end of the body to the other with a groove running down the middle. Other characters of importance are a peculiar indentation near the mouth and the not uncommon occurrence of the macronucleus in two separate rounded portions. Roundish oval cysts of this ciliate, 80 to 100 microns in length by 60 to 80 microns in width, were also found by him.

The variability within schistosome populations was explored using mixed populations of cercariae from multimiracidial snail infections and individual clones of Schistosoma mansoni cercariae obtained from monomiracidial snail infections. We investigated the heterogeneity between different clones of S. mansoni with respect to infectivity and metabolism. One difference between clones of cercariae was found in the recovery of adult worms from Balb/C mice. Recovery of adult worms was greater after infections with a mixed population than with a clonal population. To investigate some biochemical features of individuals in clones or mixed populations, the uptake of [35S]methionine into individual parasites and their membrane proteins was measured. Isoelectric focusing of a soluble membrane fraction: the frozen–thawed supernatant extracted from individual clones, showed the presence of proteins of isoelectric point between 7.2 and 8.2 in all clones. These proteins were less labelled with [35S]methionine in the clones than in the mixed population. It was concluded that basic proteins are synthesized by all clones and in the mixed population but at different rates. Differences in the rate of incorporation of [35S]methionine into the surface membranes of schistosomula and adult worms derived from individual clones are reported. In addition, a direct correlation between the percentage of recovery of adult worms from mice infected with individual clones of S. mansoni and the rate of incorporation of [35S]methionine into schistosomula of these particular clones was observed. It is suggested that the high rate of metabolism shown by an individual clone may account for the enhanced survival of the cercariae derived from that clone during penetration of the skin and migration through the vertebrate host. In order to examine individuals in a population of schistosomula, from a clone or mixed population, the lysosome-specific fluorescent probe LysoTracker DND-99 was used to label the parasites and quantitative fluorescent measurements were made on individual parasites. There were significant differences between clones and a mixed population. Furthermore, the variation between individuals from a mixed population was greater than from that in any clone, just as was found in the infectivity studies. Freshly transformed schistosomula of individual clones labelled with the LysoTracker DND-99 showed less variations in the quantitative uptake of the dye within a single clone when compared to the mixed population. We conclude that for any biochemical and biological parameter, a population of cercariae consists of individuals showing a wide range of values, with a much greater range in a mixed population. This variability is likely to have great relevance for infectivity of the final host and the efficacy of drugs and the immune system.

Two attempts to transfer immunity against N. muris to rats using the lymph node and spleen cells from actively immunized donors were unsuccessful. Experiments showed that the rats were sufficiently inbred, that the transfer technique was satisfactory, and that the donors were adequately immunized. The rats' competence as donors for adoptive transfer was demonstrated with sheep red cells as antigen. The adoptive transfer of immunity against sheep red cells was successful in recipients whose donors had sheep red cells only and no N. muris. There was no detectable transfer of immunity against N. muris or sheep red cells to recipients whose donors had received both.

We are very grateful to Miss Kathleen O'Brien for technical assistance, to Professor P. B. Medawar, F.R.S., for his help and advice and to Dr E. J. Delorme for showing us Professor M. F. A. Woodruff's skin-grafting technique.

Cestodes collected from birds of El Recreo, Zelaya, Nicaragua are reported. Sacciuterina mathevossiani sp.nov. from Rhamphocaenus rufiventris is the only species in the genus with 32 rostellar hooks, each 22–24 μm long, and with 5–9 testes. Angularella beema (Clerc, 1906) Strand, 1928, from Iridoprocne albilinea, is partially redescribed. Also reported are Dilepis undula (Schrank, 1788) Weinland, 1858, from Turdus grayi; Anomotaenia mutabilis (Rudolphi, 1819) Baer et Bona, 1960, from Florida caerulea; Ophiovalipora lintoni (Olsen, 1937) Coil, 1950, from Butorides viriscens; Hymenolepsis pellucida Fuhrmann, 1906, from Ramphocelus paserinii and Gymnostinops montezuma; and Raillietina (R). maplestonei Southwell, 1930, from Amazona autumnalis. All are new records for Nicaragua.

Thanks are expressed to Dr Thomas R. Howell, University of California who, assisted by Mr John Zeiger, collected and identified the hosts. The collecting of birds was supported in part by a grant to Dr Howell from the University of California Association in Tropical Biogeography. Gratitude is also expressed to Dr W. H. Coil, University of Kansas, who examined some of the specimens and offered helpful suggestions, and to Miss Dorothy B. Segal, Beltsville Parasitological Laboratory, for checking the records on Angularella.

1. The parasitization of the slugs Milax sowerbii and Agriolimax reticulatus by a brachylaemid trematode in an area in Durham, during the period 1949–53, is described. Evidence is given that M. sowerbii is a natural intermediate host of the parasite.

2. Seasonal fluctuations in the incidence of infestation are described, including the fluctuations in the incidence of the four developmental stages of the metacercariae. Primary (spring) and secondary (autumnal) infestations of the molluscs are described.

3. The implications of an unexplained decline in parasite density during 1953 are noted.

4. A life history for the parasite, involving a small mammal as the vertebrate host, is postulated.

The foundation of an Institute for Research in Parasitology in Cambridge is an achievement worthy of being recorded in some detail since it affords a recognition of the value of a branch of biological science that cannot but gratify all who have gained an insight into the deep significance of the many problems which parasitology presents when viewed from the standpoint of pure science.

Mathematical modelling provides an effective way to challenge conventional wisdom about parasite evolution and investigate why parasites ‘do what they do’ within the host. Models can reveal when intuition cannot explain observed patterns, when more complicated biology must be considered, and when experimental and statistical methods are likely to mislead. We describe how models of within-host infection dynamics can refine experimental design, and focus on the case study of malaria to highlight how integration between models and data can guide understanding of parasite fitness in three areas: (1) the adaptive significance of chronic infections; (2) the potential for tradeoffs between virulence and transmission; and (3) the implications of within-vector dynamics. We emphasize that models are often useful when they highlight unexpected patterns in parasite evolution, revealing instead why intuition yields the wrong answer and what combination of theory and data are needed to advance understanding.

Dinobdella ferox is the most reported and studied leech species parasitizing mammalian mucus membranes. However, our knowledge of D. ferox during parasitizing and its effects on hosts has remained limited. To investigate the behaviour of D. ferox in the parasitic period and the subsequent host symptoms, the author was infested voluntarily with three juvenile leeches under regularly-conducted examinations of complete blood count (CBC) and nasal endoscopy (NE). After the first head protrusion of the parasitizing leech at the host nostril, the occurrence of bleeding-related symptoms decreased and ceased completely weeks before the end of the parasitic period. Negligible impacts of the parasitizing leech on the host were shown by CBCs, and a parasitizing leech was able to hide from NE despite being so large it at times protrudes out of the host nostril. Finally, parasitizing D. ferox were coaxed to emerge at the nostril by water only after their first head protrusion, indicating that non-invasive removal of parasitizing D. ferox before head protrusion might be difficult. Through the voluntary infestation, the full documentation of behaviours of D. ferox in the parasitic period and host symptoms shown in this study will promote better diagnoses and treatments of nasal leech infestation.

A Babesia divergens merozoite antigen was purified by affinity chromatography using a monoclonal antibody. Silver staining of SDS-PAGE gels revealed 2 bands of Mr 50–60 kDa and Mr 24–29. It is proposed that the Mr 24–29 kDa band represents the native protein and that it is complexed, perhaps as a dimer or perhaps to host protein to give the Mr 50–60 kDa band. Peptide analysis of the antigen followed by Western blotting with the monoclonal antibody revealed only an Mr 20–24 kDa band. After affinity purification the antigen was precipitated with acetone and inoculated subcutaneously, together with complete Freund's adjuvant, into gerbils. Two inoculations were given 3 weeks apart, after which the immunized animals and a group of control animals were challenged with 5 × parasitized red cells from a virulent microaerophilus stationary phase (MASP) culture of an homologous strain of B. divergens. Parasitaemias rose rapidly in control animals and all were dead by the fifth day. Two of the vaccinated animals survived the challenge. Parasitaemias in the remaining two rose slowly but both animals succumbed on the seventh day. Western blotting of merozoites and of the purified antigen, using sera from the surviving animals showed strong reactivity with the Mr 24–29 kDa band.

A comparison was made between 14-day-old populations of Nematodirus battus from single infections and from those which developed concurrently with Haemonchus contortus from the day of infection and from days 5 and 10 after infection. The numbers of Nematodirus fell with decreasing length of exposure to Haemonchus and were negatively correlated with the numbers of Haemonchus. The percentage of the populations of Nematodirus in the adult stage and the mean worm lengths fell with increasing length of development with Haemonchus, the lowest values being found in infections which developed concurrently with the abomasal worm for the full 14 days (days 0–14). Mean Nematodirus worm lengths were negatively related to abomasal pH and Na+ levels in populations which were concurrent with Haemonchus for the last 9 days (days 5–14) and for the full 14 days of development studied. Nematodirus egg capacity also fell with exposure to Haemonchus, but was lower in the worm populations exposed for the last 9 days than in those exposed for 14 days. Egg capacity was related to abomasal electrolyte levels in populations which had developed concurrently with Haemonchus for the last 9 days and for the full 14 days. Significant differences between the population parameters of Nematodirus from the proximal and middle third of the small intestine were only found in the single Nematodirus infections and in those which were concurrent with Haemonchus for the last 4 days (days 10–14). The differences in the populations of Nematodirus were related to the probable changes in alimentary conditions affected by the different periods of concurrent infections of Haemonchus. It was suggested that the alimentary changes may have caused the loss of adult Nematodirus and have influenced the growth, development and reproductive capacity of the intestinal worm by acting upon the fourthand fifth-stage larvae.

Sheep which had been either previously infected with O. circumcincta or maintained worm-free, were surgically prepared with separated fundic pouches and abomasal cannulae and subsequently infected with 20000 O. circumcincta larvae three times weekly.

A reduction in food intake and increases in total acid output from the pouches and plasma pepsinogen levels were evident in both groups of sheep 4 days after repeated infections commenced; effects which increased in severity after 12 or more days. Except for a transient period of slight failure, previously infected sheep retained the capacity to acidify their abomasal contents whereas previously worm-free sheep lost this capacity. These changes were reversed between 2 and 7 days after treatment with thiabendazole (88 mg.kg−1).

Secretory capacity of the fundic pouches was tested with histamine (40 μg.kg−1), the histamine antagonist (burimamide 8mg.kg−1) and atropine (100 μg kg−1). Ostertagiasis reduced or abolished the stimulatory effects of histamine. An increase in secretion volume and acid output was obtained after food was freshly provided, even though as little as 25 gm was consumed. Atropine and burimamide both caused a profound decrease in pouch secretion and acid output.

These data are consistent with the hypothesis previously stated that in ostertagiasis the hypersecretion from fundic pouches is due to increased levels of circulating gastrin.

The larvae and puparia of Limnophora exurda are to be found in tufts of wet moss or liverworts in or near small waterfalls.

The larvae are carnivorous and exhibit the characteristic morphological characters of carnivorous anthomyid larvae.

Cell cycle progression is a question of fundamental biological interest. The coordinated duplication and segregation of all cellular structures and organelles is however an extremely complex process, and one which remains only partially understood even in the most intensively researched model organisms. Trypanosomes are in an unusual position in this respect – they are both outstanding model systems for fundamental questions in eukaryotic cell biology, and pathogens that are the causative agents of three of the neglected tropical diseases. As a failure to successfully complete cell division will be deleterious or lethal, analysis of the cell division cycle is of relevance both to basic biology and drug design efforts. Cell division cycle analysis is however experimentally challenging, as the analysis of phenotypes associated with it remains hypothesis-driven and therefore biased. Current methods of analysis are extremely labour-intensive, and cell synchronization remains difficult and unreliable. Consequently, there exists a need – both in basic and applied trypanosome biology – for a global, unbiased, standardized and high-throughput analysis of cell division cycle progression. In this review, the requirements – both practical and computational – for such a system are considered and compared with existing techniques for cell cycle analysis.

The nematode worms discovered by Mr Shipley in the swim-bladder of Trout belong to the species Cystidicola farionis, first described by Fischer, and considered by him to represent a new and distinct type in nematode structure for which he proposed the generic name Cystidicola. Later writers refused to accept the new genus and included it in various other groups (see Synonymy, p. 190). In accordance with an old nomenclatural practice the proposed generic name was adopted as the specific name in place of that originally given, thus Cystidicola farionis became, for Rudolphi, Spiroptera cystidicola. From a detailed examination of the various characters of C. farionis I have come to the conclusion that Fischer was correct in creating a new genus for the new forms, and I therefore propose the reinstatement of the abandoned name Cystidicola. It is also in accordance with modern nomenclatural ruling that the original specific name farionis should be adopted in place of cystidicola.

For parasites in natural systems, the most common pattern of spatial distribution is aggregation among hosts. The main causes of such aggregation are variable exposure of hosts to parasites and heterogeneity in host susceptibility. The objective of this study was to determine if there are differences in the aggregation pattern of two species of ectoparasitic flies between the Pantanal and Cerrado regions of Brazil on the bat Artibeus planirostris. We collected the ectoparasites from bats captured between 2002 and 2017 with mist nets in 21 sites in the Pantanal and 15 sites in the surrounding plateaus. The results showed that the aggregation of ectoparasitic flies in Pantanal was more pronounced than in Cerrado. The discrepancy aggregation index (D) of the bat fly Megistopoda aranea was 0.877 in Pantanal and 0.724 in Cerrado. The D values of Aspidoptera phyllostomatis was even higher, with 0.916 and 0.848 in the Pantanal and Cerrado, respectively. Differences in the shelters used may be the main factor shaping variation in aggregation, since the Pantanal does not have rock formations, with only foliage, crowns and hollow tree trunks. These differences likely affect host exposure to the parasites, leading to an increase in parasite aggregation.

Chagas disease (CD) is caused by the intracellular protozoan parasite Trypanosoma cruzi and affects more than 10 million people in poor areas of Latin America. There is an urgent need for alternative drugs with better safety, broader efficacy, lower costs and shorter time of administration. Thus the biological activity of viniconazole, a chloroaryl-substituted imidazole was investigated using in vitro and in vivo screening models of T. cruzi infection. Ultrastructural findings demonstrated that the most frequent cellular damage was associated with plasma membrane (blebs and shedding events), Golgi (swelling aspects) and the appearance of large numbers of vacuoles suggesting an autophagic process. Our data demonstrated that although this compound is effective against bloodstream and intracellular forms (16 and 24 μ m, respectively) in vitro, it does not present in vivo efficacy. Due to the urgent need for novel agents against T. cruzi, the screening of natural and synthetic products must be further supported with the aim of finding more selective and affordable drugs for CD.