The earliest stages found are groups of small bodies, 1·8 or 2·0μ in diameter. These groups are probably taken up by phagocytic cells and pass through the epithelium of the host into the connective tissue, where a cyst is formed by the host. Within the cyst the bodies grow. In many cysts there is a differentiation into two types: the larger, when mature, attain 40μ in size, are shaped like a pear, and contain at the broad end a chromatic rod. The small bodies reach 3Oμ in length, are also somewhat piriform, and contain two similar structures attached to their nuclei. In some cysts large bodies alone are found.

Development is periodic, the youngest stages being found from January to March and the parasites not reaching maturity until September–November.

Type species P. sociabile, with the features mentioned above: found near the ventral surface of the foot of Buccinum undatum.

Whole worm homogenates and excretory/secretory (E/S) products of adult Nippostrongylus brasiliensis significantly decreased the amplitude of contractions of segments of uninfected rat intestine maintained in an organ bath, with significantly larger volumes of E/S products being required to bring about a similar decrease to that caused by the whole worm homogenate. Boiled samples of homogenate and E/S products significantly decreased the amplitude of contractions of uninfected rat intestine, but larger volumes were needed than with unboiled samples. Frequency of contraction was unaltered by homogenates or E/S products. When electric eel AChE was injected into the lumen of segments of uninfected rat intestine maintained in an organ bath there was no significant decrease in the amplitude of contractions. These results suggest that substances present in the E/S products of N. brasiliensis significantly reduce the amplitude of contractions of uninfected rat intestine in vitro and that the biochemical holdfast responsible for this phenomenon may not be AChE.

The microsporidian Encephalitozoon cuniculi is an obligate intracellular parasite that develops asynchronously inside parasitophorous vacuoles. Spore differentiation involves the construction of a cell wall commonly divided into an outer layer (exospore) and a thicker, chitin-rich inner layer (endospore). The developmental patterns of protein deposition and mRNA expression for 2 different spore wall proteins were studied using immunocytochemical and in situ hybridization procedures with ultrathin frozen sections. The onset of deposition of an exospore-destined protein (SWP1) correlated with the formation of lamellar protuberances during meront-to-sporont conversion. No evidence for a release of SWP1 towards the parasitophorous vacuole lumen was obtained. An endospore-destined protein (EnP1) was detected early on the plasma membrane of meronts prior to extensive accumulation within the chitin-rich layer of sporoblasts. swp1 mRNA was preferentially synthesized in early sporogony while enp1 mRNA was transcribed during merogony and a large part of sporogony. The level of both mRNAs was reduced in mature spores. Considering the availability of the E. cuniculi genome sequence, the application of nucleic and/or protein probes to cryosections should facilitate the screening of various genes for stage-specific expression during microsporidian development.

The aim of this study was to evaluate the purine levels of lambs experimentally infected with Haemonchus contortus. A total of 12 healthy lambs were divided into two groups, composed of 6 animals each: Group A represented the healthy animals (uninfected), while in Group B the animals were infected with 15 000 larvae of H. contortus. Blood was drawn on days 15, 45 and 75 post-infection (PI) in order to perform the purine analysis (ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and uric acid) by high pressure liquid chromatography (HPLC) in serum. On day 15 PI a significant (P<0·05) increase in the levels of ATP and inosine was observed in the infected animals, unlike the levels of ADP, adenosine, xanthine and uric acid which were reduced. On day 45 PI a significant (P<0·05) increase in the ATP and xanthine levels in infected animals was observed, contrasting with reduced levels of ADP and uric acid. Finally, on day 75 PI an increase occurred in the levels of ATP, adenosine and hypoxanthine in infected lambs, concomitant with a reduction in the levels of ADP and uric acid (P<0·05). These changes in purine levels may influence the inflammatory process and the pathological events.

This paper provides the first detailed description of a Tetracapsuloides species, Tetracapsuloides vermiformis n. sp., with vermiform stages in the bryozoan host, Fredericella sultana, and its experimental transmission from F. sultana to Cyprinus carpio. The suitability of morphological, biological and 18S rDNA sequence data for discrimination between malacosporean species is reviewed and recommendations are given for future descriptions. Presently, malacosporean species cannot be differentiated morphologically due to their cryptic nature and the lack of differential characters of spores and spore-forming stages in both hosts. We examined biological, morphological and molecular characters for the present description and for revising malacosporean taxonomy in general. As a result, Buddenbrockia plumatellae was split into two species, with its sac-like stages being ascribed to Buddenbrockia bryozoides n. comb. In addition to ribosomal DNA sequences multiple biological features rather than morphological characters are considered essential tools to improve malacosporean taxonomy in the future according to our analysis of the limited traits presently available.

We investigated the involvement of nitric oxide in Schistosoma-induced liver injury. We found that inducible nitric oxide synthase mRNA became detectable in the liver at the onset of parasite egg laying and levels then increased as the eggs accumulated in the organ. Enzyme concentration and activity paralleled mRNA levels. The event was a direct effect of egg deposition, as it occurred in the liver after natural infection, or in the lungs after i.v. injection of the eggs. However, nitric oxide seems to have no direct effect on the eggs since in vitro assays showed that the nitric oxide donor SIN-1 did not alter the ability of the eggs to hatch. L-Arginine and L-NAME, a nitric oxide synthase inhibitor, were administered to infected mice in an attempt to increase or reduce nitric oxide production, respectively. Arginine had no effect on the disease, whereas the inhibitor led to a marked decrease of hepatic injury with, in particular, reduced fibrosis and decreased lipid peroxidation. In conclusion, not only is inducible nitric oxide synthase activity unlikely to exert an anti-microbicidal effect against the egg stage of S. mansoni but it might lead to deleterious effects in the liver and therefore contribute to the pathology.

Most of the nine species dealt with in this paper were collected before the outbreak of World War II. Library facilities in Ceylon, meagre enough even in normal times, were altogether unavailable during the war years owing to the removal of the Colombo Museum Library to safe areas inland. It was only after the library was brought back to Colombo at the beginning of 1947 that this paper could be got ready for publication. Hence it appears 10 years after the last contribution in the series.

In the previous paper it was concluded that those aged [ges ] 15 years of both sexes could comprise the indicator group for rapid epidemiological assessment (REA) of onchocerciasis in the Amazonian focus. This paper explores relationships between community microfilarial (mf) prevalence, intensity, and nodule prevalence in 20 Yanomami communities, that would allow identification of REA methods in the region. The mean nodule ratio (prevalence of nodules/prevalence of mf) was 0·54 when onchocercomata in the indicator group were considered. The Spearman correlation coefficient between mf and nodule prevalence was 0·686 (P = 0·001). Palpation of nodules had 92% specificity and 32% sensitivity when compared to skin-snipping for the diagnosis of onchocerciasis. The predictive value positive increased from 75% to 81% when the indicator group was used. A microfilarial prevalence > 75% in this group would be indicative of hyperendemic status in the village, between 30 and 75% of mesoendemicity, and < 30% of hypoendemicity. For the assessment of infection intensity, biopsies may be taken from the iliac crest for all endemicity levels. Five of the hyperendemic villages surveyed in this work had a community microfilarial load (CMFL) greater than 10 mf/skin snip; the remaining 5 had a CMFL between 5 and 9. These levels of infection merit high priority ivermectin treatment. In Latin America, communities at both moderate and severe risk are included in mass chemotherapy programmes (i.e. when mf prevalence is over 20%). Roughly, a nodule prevalence in the indicator group > 10% would suggest a community mf prevalence > 20% with a sensitivity of 85% and a specificity of 71%. A multiple linear regression model of the arc-sine transformed mf prevalence in the village (all ages) on nodule prevalence in those aged [ges ] 15 years and altitude of the village explained 72% of the variance. The model combining nodule and altitudinal information had a sensitivity of 92% and a specificity of 71% in comparison to an estimated mf prevalence of 21% or more. It is suggested that the usefulness of the REA methods proposed be assessed in other areas of the Amazonian onchocerciasis focus.

The series of egg envelopes around the acanthor in the mature egg of the palaeacanthocephalan, Polymorphus minutus, has been investigated with light and electron microscopy. An attempt has been made to characterize the macromolecules from which the envelopes are constructed using histochemistry, an analysis of stabilizing bond types and comparisons of envelope fine structure with that of other structural protein systems.The outermost envelope (I) of the mature Polymorphus egg is a fertilization membrane. It is produced by membrane-bounded inclusions in the cytoplasm of the unfertilized oocyte which discharge their contents into the extracellular space around the egg. Envelope II is composed largely of keratin, and its subzones consist of different packing arrangements of 8 nm diameter electron-lucid filaments in an electron-dense matrix. The electron microscopical appearances which this filamentous keratin can present due to section orientation artefacts are discussed. The innermost envelope (III) is 20–30 nm thick and highly corrugated. The spaces between envelopes I and II and between envelope III and the inner surface of envelope II contain material with a granular or fibrous ultrastructure. These spaces show histochemical evidence for the presence of acid mucopolysaccharides.

The infectivity and invasiveness of a single strain of Entamoeba histolytica to young rats has been studied over a period of 12 years. The virulence was slowly lost over a period of months or years of cultivation in vitro. After four to six liver passages, virulence was again established and again declined in culture. This was repeated on three occasions. Each time the strain lost virulence, the capacity to invade the mucosa was lost before the amoebae became non-infective to young rats. The duration of experimentally acquired virulence was progressively reduced after each succeeding series of liver passages.

Ethylene glycol bis (β-aminoethylether)-N,N,N,N-tetraacetic acid (EGTA) is a chelating agent capable of binding to positively-charged metal ions, including a calcium-ion (Ca2+). Here, we demonstrated the inhibitory effect of the chemical on the in vitro asexual growth of the equine protozoan parasites, Babesia caballi and Babesia equi. The growth of both B. caballi and B. equi was significantly inhibited in the presence of EGTA (IC50=1·27 and 2·25 mM, respectively). Under microscopical observation, increased percentages of extracellular merozoites in the total parasites were detected in both of the cultures treated with high concentrations of EGTA. In contrast, further addition of Ca2+ to the EGTA-treated cultures prevented the parasites from clearing and the percentages of extracellular merozoites from increasing. As for B. caballi, an invasion test using high-voltage pulsing proved that EGTA has an inhibitory effect to their erythrocyte invasion. These results suggest that Ca2+ is involved in erythrocyte invasion by equine Babesia parasites.

The interesting Note by Dr Sant' Anna, which precedes this paper, leads me to record some observations of a somewhat similar nature to those he has reported. My information is derived from three letters received from Africa, and from Dr Hindle.

Drug resistance is now a severe and increasing problem in trypanosomes, but molecular details of mechanisms of resistance are only beginning to unveil. There is urgent need to clearly elucidate the different mechanisms of drug resistance in trypanosomes in order to circumvent existing resistance problems and avoid emergence of resistance to the next generation drugs. In this study, we cloned and characterized a novel gene, TeDR40, whose expression is associated with resistance to berenil in Trypanosoma evansi. Expression analysis showed that the gene was at least 1000-fold upregulated in resistant parasites and the encoded protein appeared to have a ubiquitous cellular localization. To investigate the association of TeDR40 with berenil-resistance, we genetically modified wild-type berenil-sensitive T. evansi for inducible over-expression of the TeDR40 gene. Induction of over-expression of TeDR40 in T. evansi led to decreased (P<0·01) sensitivity to berenil. Our findings indicate a possible correlation between over-expression of a novel gene, TeDR40, and reduced sensitivity to berenil in an in vitro-cultured clonal line of T. evansi.

The morphology of the post-hatch moulting and developmental sequence of an amphimictic population of Rotylenchulus reniformis has been examined in living and fixed material. Under suitable conditions of temperature and in a moist environment the 2nd-stage larva (L2) undergoes a series of 3 moults and developmental changes which result in the formation of males and immature females. After hatching and prior to the start of the first of these moults (the second moult), there is a pre-moult period, usually of 3–5 days duration. The morphology of the entire moulting and developmental sequences, from L2 to just after the final moult, has been followed in single living specimens of a parasitic nematode using differential interference contrast optics, and sections cut through different stages have been observed under the transmission electron microscope. These moulting sequences (at 24 °C) take place at similar times in developing males and females. The second moult takes place on the second day after commencement of moulting, the third on the third or fourth days and the fourth and final moult on the sixth or seventh days, followed by further development over several days to give rise to the adult male and the immature female. The ultrastructure associated with some of the more obvious of these developmental changes is described and includes the morphology of the head region and cuticles of L2, L4, adult males and immature females, the oesophageal glands of the immature female and the copulatory spicules and spermatozoa of the male.

Observations have been made on the ultrastructure of objects identified as ovarian balls from female Moniliformis after 1, 3, 5, 7 and 9 days in the rat. Similar objects are present in the body cavity of female cystacanths from cockroaches. The ovarian balls from 1-day-old worms are formed of several cells which are enclosed within a surface coat. During development, the ovarian balls increase in size and cell number and the internal organization appears to become more complex. After 9 days of development in the rat, the surface coat of the ovarian balls can no longer be observed and microvilli are present. It also appears that the supporting syncytium has been formed by this time.

By employing a combination of sub-stage heating and supra-vital staining with eosin or neutral red it was found that viable and non-viable hydatid scolices could be distinguished microscopically. Using this technique a study of the effect of heat in vitro on hydatid scolices has shown that death resulted from exposures at 50° C. for 70 min. and at 55° C. for 30 min.

Experiments on the effect of boiling in destroying the contents of fertile cysts embedded in sheep liver showed that when offal was added directly to boiling water destruction of scolices was complete after 40 min. boiling. When the infected liver was placed in cold water brought to the boil, scolex death was assured only after 30 min. subsequent boiling.

Ultra-violet radiations of 2537 A. did not kill scolices under the conditions adopted. Although this wave-length would apparently be ineffective as a scolicicidal agent in surgery of the human hydatid cyst, irradiation of hydatid fluid containing scolices might offer a simple method for initial sterilization of scolex culture media.

The author wishes to acknowledge many helpful suggestions and loan of the Hanovia lamp by Dr G. M. Richardson of the Virus and Immunology Research Department, Otago Medical School.

1. Anagrus atomus (L.) Hal. is a mymarid parasite of the eggs of Erythro-neura pallidifrons Edwards.

2. The parasite is parthenogenetic, at any rate for the greater part of the year.

3. Two larval stages are described.

4. More than one egg may be laid in a single host egg and these eggs may hatch, but only one of the Anagrus larvae reaches maturity.

5. The development of Anagrus atomus takes about sixteen days.

6. The species is multi-voltine.

Chagasic cardiopathy has become one of the most frequent causes of heart failure and sudden death, as well as one of the most common causes of cardio-embolic stroke in Latin America. The myocyte response to oxidative stress involves the progression of cellular changes, primarily targeting the mitochondria and modifying therefore the energy supply. In this paper we analysed the effect of the infection of mice with 2 different strains of Trypanosoma cruzi (Tulahuen and SGO Z12) in the chronic indeterminate stage (75 days post-infection), upon the structure and function of cardiac mitochondria. The structural results showed that 83% of the mitochondria from the Tulahuen-infected mice presented an increase in their matrix and 91% of the mitochondria from the SGO Z12-infected group showed a reduction in their diameter (P < 0·05). When the Krebs cycle and mitochondrial respiratory chain functionality was analysed through the measurement of the citrate synthase and complexes I to IV activity, it showed that their activity was altered in all cases in a similar manner in both infected groups. In this paper we have demonstrated that the chronic indeterminate phase is not ‘silent’ and that cardiac mitochondria are clearly involved in the genesis and progression to the chronic chagasic cardiopathy when different factors alter the host-parasite equilibrium.

Codon usage of Crytosporidium parvum was compared with those of other Eimeriorina Toxoplasma gondii and Eimeria tenella and revealed a biased use of synonymous codons with a preference for NNU (40·0%) and NNA (33·4%). There was no close resemblance of the codon usage of C. parvum to T. gondii (correlation coefficient, r = 0·14) or E. tenella (r = 0·14) but it was similar to Entamoeba histolytica (r = 0·75) and Plasmodium falciparum (r = 0·5). Analysis of the codon usage in homologous gene sequences (actin, β-tubulin) also failed to reveal a close relationship between C. parvum and T. gondii or E. tenella. The low usage codons in C. parvum were most frequently used codons in T. gondii and E. tenella. These observations are consistent with 18S rRNA sequence analysis which shows no close relationship of Cryptosporidium with other Eimeriorina (Sarcocystis, Toxoplasma and Eimeria) and questions the validity of the current classification of C. parvum.

The morphology of the mucosal surface of samples from the small intestine of young protein-deficient pigs was examined by scanning electron microscopy. Three pigs had been infected with Ascaris suum for at least 58 days while 1 had remained uninfected; all pigs were housed and maintained under the same conditions, at the same time. The tissue samples collected at post mortem examination from pigs which contained A. suum showed varying degrees of villous atrophy and fusion. In addition, unusual small craters and as yet unidentified objects were observed at the surfaces of the enterocytes of Ascaris-infected pigs. These changes in mucosal morphology were not seen in the tissue taken from the uninfected pig. The possible association between the mucosal lesions and lactose maldigestion in young, protein-deficient pigs infeceted with A. suum is discussed.