Fasciola tragelaphi sp.nov. from the bile ducts of a Tragelaphus spekei shot in the Chobe swamps of Rhodesia differs from other species of the genus in its very large size (10.2–12.0 cm long in fixed and mounted specimens), in the shape of its body and in the distribution and arrangement of the reproductive organs. The testes lie almost entirely in the posterior half of the body, well away from the female genitalia, which lie mostly in the anterior third of the worm. The ovary is always bilateral, and the coiled uterus runs in a straight line between the caeca to the genital atrium. A prepharyngeal pouch found in this species is compared with that found in other members of the genus Fasciola and in related genera.

We gratefully acknowledge the help given during the preparation of this paper by the staff of the Bureau, particularly Mr G. Dimmock for technical assistance. We would also like to thank Mr S. Prudhoe for reading the manuscript and offering useful advice, Mr B. Bracegirdle for producing the photograph of the whole worm reproduced in the Plate, fig. 1 and to Bechuanaland Hunters Ltd., particularly I. M. Henderson, for obtaining further specimens for examination.

Adult Rhipicephalus appendiculatus ticks, infected as nymphs by feeding them on an African buffalo harbouring Theileria lawrencei, were applied to the ears of rabbits.

Equal numbers of the feeding ticks were removed daily from rabbits and either dissected and processed so that parasites in their salivary glands could be examined morphologically and classified, or ground in Eagle's Minimal Essential Medium, to harvest parasites from the ticks in the resultant supernatant fluid. The infectivity of the supernatant fluid was tested by inoculation of aliquots into groups of susceptible cattle.

It was found that supernatant fluids produced from day 0 to day 2 fed ticks were uninfective to cattle but those produced from 3 to 9 days were infective. The most infective supernatant fluid was produced from 6 day fed ticks.

The reactions resulting in cattle were correlated with the number and morphology of parasites in sections of salivary glands and it was found that mature parasites coincided with infectivity of the supernatant fluid to cattle.

From the reactions in cattle inoculated with supernatant fluids from 5 and 6 day fed ticks it was concluded that this method of harvesting parasites was efficient.

Examination of the salivary glands of a representative sample of a T. lawrencei infected tick batch is a potential means of screening material for T. lawrencei stabilates.

In the present study, a recombinant aminopeptidase P (rTgAPP) from Toxoplasma gondii was expressed in Escherichia coli to evaluate its enzyme parameters. The rTgAPP showed strong activity against a synthetic substrate for aminopeptidase P at pH 8·0 with a Km value of 0·255 µm and a kcat value of 35·6 s−1. The overall catalytic efficiency (kcat/Km) of the rTgAPP was 139·6 × 105 M−1 s−1. The activity of rTgAPP was enhanced by the addition of divalent cations and inhibited by bestatin. Deletion of TgAPP gene in the parasite through a CRISPR/Cas9 system resulted in inhibition of growth indicating the importance of TgAPP. Thus our findings reveal that TgAPP is an active enzyme in T. gondii and provide an insight into the function of TgAPP.

The polystomatid Pseudodiplorchis americanus occupies a wider range of habitats and experiences more diverse physiological conditions than any other monogenean. It initially invades the respiratory system of an anuran, Scaphiopus couchii, and then migrates along the alimentary tract while the host is actively feeding, resulting in exposure to digestive enzymes and the surfactant action of bile. Whilst in the urinary bladder, parasites are exposed to wide osmotic fluctuations. This ultrastructural study reveals a set of adaptations unknown elsewhere in platyhelminth biology. During development within the respiratory tract, pre-migratory worms accumulate two types of electron-dense tegumental vesicle. Migration through the gut is accompanied by mass secretion of vesicles which appear to provide protection against digestion. Pre-migrants transferred experimentally to digestive fluids die within minutes unless they have received a specific cue which is responsible for triggering vesicle secretion. Migrants stimulated by this trigger factor can tolerate the same conditions for up to 8 h by continually releasing vesicles to form a protective surface coat. No specific structural adaptations were evident for survival in the lungs or bladder of the host.

To increase the existent genetic variability in cysteine proteases, a polymorphism study was performed in Haemonchus contortus by comparing 2 different strains of the parasite: North American (NA) and Spanish (SP) strains. For this purpose, the polymorphism of 5 previously reported genes (AC-1, AC-3, AC-4, AC-5 and GCP-7) were analysed by PCR–SSCP and sequencing procedures. Based on the SSCP results, a total of 20 different alleles were identified for the 5 loci assessed. Except locus AC-5, all the loci were polymorphic. Loci AC-1, AC-3, AC-4 and GCP-7 showed 5, 8, 2 and 4 alleles, respectively. The allelic frequencies ranged from 0·0070 to 0·8560 and were significantly different between strains. In addition, nucleotide diversity analyses showed a significant variation within and between strains. The variations in the nucleotide sequence of the different alleles were translated in some cases into changes in the amino acid sequence. Evidence of genetic variability in cysteine proteases from two different strains of H. contortus for the same set of genes had not been previously reported.

Factors governing the response of the Oriental rat flea, X. cheopis, to the white rat and to three murids were studied in an olfactometer.

Starved females aged 5–10 days were attracted to white rats, whereas starved younger females were repelled or indifferent. Starved males, 1–10 days old, were either indifferent or were repelled.

No clear-cut attraction of 7- and 8-day-old starved females towards the murids Meriones tristrami, Acomys dimidiatus and Microtus guentheri was observed.

Starved females increased their weight during the first 8 days of life by 12·0%, while starved males lost 2·2%. Females kept in a vessel with a white rat showed a 115·2% weight gain, while males under the same conditions gained only 18·8% (Table 5).

The authors wish to thank Dr F. G. A. M. Smit, of the British Museum (Natural History), Tring, Hertfordshire (England), for his valuable help in the preparation of the manuscript for this paper.

A fertile source of error in protozoology is to be found in the overlooking of the occurrence of mixed infections in a host. Two organisms, each independent of the other, may happen to coexist in the intestine of an insect or the blood of a vertebrate, the result being that the investigator may confuse stages in the life-cycles of parasites which are not related to each other. This source of error has led to unwarranted generalisations which have impeded scientific progress for years. Two examples at once come to mind—the trouble wrought by Schaudinn in 1904 in confusing the life-cycles of the protozoa found in the little owl, and the impediment put in the way of progress by the omission of certain workers to recognise that Crithidia grayi was not a part of the life-cycle of a trypanosome. The existence of mixed infections was overlooked in each case.

Non-specific immunostimulants were used in an attempt to protect baboons from infection by schistosomes. Subcutaneous vaccination with cord factor (4·50 mg) and muramyl dipeptide (4·56 mg) 6 days before percutaneous exposure to 3000 Schistosoma haematobium cercariae/baboon (c.p.b.) failed to protect naive baboons: baboons with a 7-month-old, 5000 c.p.b. S. haenzatobium primary infection had developed too strong a natural immunity to detect any protection attributable to vaccination. Subcutaneous vaccination with 0·4 ml of Bacillus Calmette-Guerin (BOG, 1–8 x 108 colony forming units7sol;ml) 4 days before exposure to 1000 c.p.b. S. mansoni gave a significant (38%) reduction in worm load compared with controls. However, vaccination with 0·8 (intramuscular) and 0·2 (intradermal) ml of BOG 11 days before exposure to S. mansoni 800 c.p.b. did not protect naive baboons, nor did it significantly reduce challenge worm recovery from baboons with a 13-week-old, 500 c.p.b. S. mansoni primary infection. Obvious pathology was seen at the site of vaccination in the first but not the second BCG experiment. These results partly support the findings in mice that non-specific macrophage and monocyte activators give partial protection against schistosome infections but they also illustrate that rodents and primates do not necessarily react identically. Hence, findings from rodent models should be extrapolated to man with some caution.

Recently (1927) I described a peculiar fungus parasitic on the fore-legs of a termite under the name Ectomyces calotermi n.g., n.sp. Unfortunately, I at the time overlooked a paper by Thaxter (1920), in which, among other fungus parasites of insects, he described the genus Termitaria which he founded for two species of a fungus parasitic on termites, and which appears to be the same as Ectomyces. I considered Ectomyces to be an Ascomycete; but Thaxter, who studied living material at different stages, says that the apothecial-like fructification arises by vertical proliferation from a primary pseudo-cellular layer of much branched and closely septate hyphae, some cells of which become modified and assume a chlamydospore-like appearance; and that the spores are successively abstricted as endo-conidia, and, in one species, are expelled through a terminal pore. Consequently, he considers it to be a Fungus Imperfectus of uncertain affinities, and apparently occupying an isolated position in the group Leptostromaceae.

The initiation of feeding of infected Rhipicephalus appendiculatus adults induces the rapid development of Theileria parva sporoblasts within the salivary gland acini leading to the production of numerous sporozoites which are inoculated into the mammalian host initiating infection. In this study the pattern of development, host cell specificity and emission of T. parva sporozoites within the salivary glands of heavily infected, 4-day fed adult R. appendiculatus ticks was examined. Infected acini were randomly distributed throughout the salivary gland. Sporozoite development within each gland was not synchronized and wide variation in the rate of parasite development, which correlated with the secretory activity of the individual acinus, was observed in all glands examined. Previous studies had shown that T. parva developed primarily in Type III ‘e’ cells. However, in heavily infected salivary glands sporogony and the emission of mature sporozoites also occurred in ‘c’ cells of Type II acini. Sporozoite emission from infected cells occurred by a process similar to apocrine secretion. The loss of the apical membrane of the infected cell allowed sporozoites free access to the lumen of the acinus and into the collecting ducts of the salivary gland. Sporozoite discharge was gradual since few parasites were found in the acinus valve or in the collecting ducts. Furthermore, the small size of the acinar valve aperature ensures that only small numbers of sporozoites can be released at any one time from an infected acinus.

Cutaneous leishmaniasis (CL) is a major health problem in many countries and its current treatment involves multiple parenteral injections with toxic drugs and requires intensive health services. Previously, the efficacy of a single subcutaneous injection with a slow-release formulation consisting of poly(lactide-co-glycolide) (PLGA) microparticles loaded with an antileishmanial 3-nitro-2-hydroxy-4,6-dimethoxychalcone (CH8) was demonstrated in mice model. In the search for more easily synthesized active chalcone derivatives, and improved microparticle loading, CH8 analogues were synthesized and tested for antileishmanial activity in vitro and in vivo. The 3-nitro-2′,4′,6′-trimethoxychalcone (NAT22) analogue was chosen for its higher selectivity against intracellular amastigotes (selectivity index = 1489, as compared with 317 for CH8) and more efficient synthesis (89% yield, as compared with 18% for CH8). NAT22 was loaded into PLGA / polyvinylpyrrolidone (PVP) polymeric blend microspheres (NAT22-PLGAk) with average diameter of 1.9 μm. Although NAT22-PLGAk showed similar activity to free NAT22 in killing intracellular parasites in vitro (IC50 ~ 0.2 μm), in vivo studies in Leishmania amazonensis – infected mice demonstrated the significant superior efficacy of NAT22-PLGAk to reduce the parasite load. A single intralesional injection with NAT22-PLGAk was more effective than eight injections with free NAT22. Together, these results show that NAT22-PLGAk is a promising alternative for single-dose localized treatment of CL.

Two single nucleotide polymorphisms (SNP TXNIP and SNP ARNT), both on chromosome 4, have been reported to be associated with roundworm (Ascaris suum) burden in pigs. In the present study, we selected pigs with two SNP TXNIP genotypes (AA; n = 24 and AB; n = 24), trickle-infected them with A. suum from 8 weeks of age until necropsy 8 weeks later, and tested the hypothesis that pigs with the AA genotype would have higher levels of resistance than pigs of AB genotype. We used different indicators of resistance (worm burden, fecal egg counts (FEC), number of liver white spots and A. suum-specific serum IgG antibody levels). Pigs of the AA genotype had lower mean macroscopic worm burden (2·4 vs 19·3; P = 0·06), lower mean total worm burden (26·5 vs 70·1; P = 0·09) and excreted fewer A. suum eggs at week 8 PI (mean number of eggs/g feces: 238 vs 1259; P = 0·14) than pigs of the AB genotype, as expected based on prior associations. The pigs were also genotyped at another locus (SNP ARNT) which showed a similar trend. This study provides suggestive evidence that resistant pigs may be selected using a genetic marker, TXNIP, and provides further support to the quantitative trait locus on chromosome 4.

The intrategumental pH in adult male Schistosoma mansoni as measured with pH-sensitive microelectrodes is between 7.0 and 7.2, a value about one pH unit more alkaline than expected for equilibrium. This value is maintained for at least 4 h after isolation in media buffered with Hepes or CO2/ with or without serum present. CCCP (1 μM) and FCCP (10 μM) cause rapid acidification. DNP (1 mM) and Na-orthovanadate (1 mM) acidify but also cause significant depolarization of the tegument. NH (20 mM) depolarizes and acidifies the tegument with no evidence of transient alkalinization. High K+ (25 mM) accelerates the acidification. Removal of the NH+4 causes a large transient further acidification with recovery requiring as long as 40 min. High K+ (25 mM) delays the early stage of the recovery. Presence of CO2/HCO in the incubation medium does not accelerate the recovery rate nor does SITS (100 μM) inhibit the recovery. Intrategumental Na+ is elevated after an acid load and amiloride (3 mM) as well as low Na+ medium interfere with recovery from the acid load indicating that a Na+–H+ exchanger may be present in the tegumental membrane.

The suitability of motility indices and tetrazolium-based colorimetric assays for the determination of the viability of adult Onchocerca volvulus after in vitro exposure to potential macrofilaricides has been examined. Experimentation showed that both techniques could be applied to adult O. volvulus, although the variability between individual worms necessitated the use of large experimental groups. The potential of using cut anterior tips of female O. volvulus for screening was also investigated. These were shown to give reasonably consistent motility indices, and drug effects were discernible even after 72 h in vitro culture. Application of these viability criteria to studies on the short-term in vitro survival of intact male and female O. volvulus incubated in Eagles MEM plus serum, under 5% CO2 in air, showed this medium to be suboptimal with a greater than 50 % loss of worm viability within 144 h of nodulectomy. Males isolated by the collagenase technique were shown to be significantly less viable than dissected males, by both motility indices and tetrazolium reduction. The results highlight the need to use either dissected males, or in the case of females, the need to minimize exposure to collagenase solution. A possible mechanism for selecting a more uniformly viable female worm population is discussed. Examination of the in vitro effects of CGP 20376 using these viability criteria/assay systems showed some delayed suppression of worm motility, but after 120 h in vitro CGP 20376 was not macrofilaricidal against male or female O. volvulus. Male worms were also implanted subcutaneously into gerbils. Treatment of these animals with CGP 20376, with autopsy 2 weeks later, resulted in a small macrofilaricidal effect (28% worm death). Some reduction in the motility of living worms recovered from CGP 20376-treated gerbils was also evident. Good survival of control worms recovered 2 weeks post-implantation suggests that male O. volvulus might survive longer subcutaneously. The prospects for undertaking meaningful drug evaluations against O. volvulus in vitro (and in vivo in rodents) is therefore promising, but because of parasite availability will probably be limited to those compounds which have shown potential in other filarial test systems.

1. After a general consideration of the host-parasite relations between E. histolytica and man, a case is made for the recognition of a commensal phase in the life history of this amoeba.

2. This view is supported by observations on the food habits of E. histolytica in chronic cases and carriers of human amoebiasis.

3. From these observations it is evident that from 30 to 100% of trophic amoebae in such cases have ingested bacteria derived from the contents of the large bowel.

Whilst engaged in the study of the life-histories of certain Nematode parasites of domestic animals, I have had the opportunity of examining the alimentary tracts of a number of sheep and lambs obtained from various localities in England during the last 12 months, and have thus been able to collect and identify a considerable number of the parasitic Nematodes which are found so abundantly in this situation.

Paragonimiasis is an important infectious disease in Chongqing, China. However, no epidemiological surveys of paragonimiasis have been carried out in Chongqing since it became a municipality in 1997. We conducted a retrospective case review of 683 patients who were referred to our laboratory and diagnosed as having paragonimiasis during 2010–2015. Patients were diagnosed with paragonimiasis based on immunodiagnostic tests in addition to clinical and laboratory findings. Patient data extracted from the epidemiologic form were analysed. The majority of patients were distributed on the east side of the Wujiang River, which belongs to the Three Gorges Reservoir region. Consumption of raw or undercooked freshwater crab or crayfish in the family Cambaridae was the main reason for infection. Notably, more than 50·0% of patients were diagnosed between March and July, indicating that serious clinical symptoms only appear approximately 6 months post-infection. Paragonimiasis remains a public health issue in Chongqing, and an epidemiological study of Paragonimus in the Three Gorges region is strongly recommended.

In July, 1927, Dr Kenneth Smith took a specimen of the Hippoboscid fly Ornithomyia avicularia on the window of a building at the Cambridge University farm. The fly was lethargic and easily captured, and, noticing that its abdomen was infested by some parasite, the captor kindly handed me the specimen.

Alteration of the free amino acid pool of Hymenolepis diminuta was observed following incubation of worms with a single exogenous amino acid in vitro, recovery from which depended upon the initial magnitude of alteration. The free amino acid pool of both rat small intestine and H. diminuta was rendered imbalanced after feeding a single dietary dose of proline. Recovery was more rapid in the host than in the parasite tissues. The quantitative dynamics of amino acid change with time were examined. The effects of amino acid variation upon the uptake and incorporation of lysine-C14 into worm protein were examined in vitro. Four amino acids altered lysine incorporation; aspartate stimulated incorporation while ornithine, arginine and histidine reduced variously the absolute amount of lysine uptake but produced relative stimulation of lysine incorporation. These data indicate that, in the system examined, short term variation of the free amino acid pool is unlikely to affect protein synthesis in H. diminuta. Data were obtained suggesting the possible occurrence of certain amino acid inter conversions in H. diminuta.

Patients with chronic Chagas' Heart Disease (cChHD) develop an antibody response that is suspected to be involved in the cardiac pathogenesis. The response against Trypanosoma cruzi ribosomal P proteins is of particular interest, as these antibodies can cross-react with host cardiac receptors causing electrophysiological alterations. To better understand the humoral anti-P response we constructed a single-chain variable fragment library derived from a cChHD patient. The variable heavy and light regions were amplified from bone-marrow RNA and subcloned into the vector pComb3X. The phage library was subsequently panned against T. cruzi ribosomal P2β protein (TcP2β). We obtained 3 different human recombinant antibodies that specifically reacted with TcP2β in ELISA and Western blots. Two of them reacted with the C-terminal region of TcP2β, peptide R13, as the recombinant autoanti-P antibodies from Systemic Lupus Erythematosus (SLE) patients. Interestingly, the third one was specific for TcP2β but did not recognize R13, confirming the specific nature of the anti-P response in Chagas disease. Neither sequence nor VH usage similarities between Chagas and SLE anti-P autoantibodies were observed. Herein, the first human mAbs against TcP2β have been obtained and characterized showing that the humoral anti-P response is directed against the parasite and does not include an autoimmune component.