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 cDNA clone encoding a full length putative collagen has been isolated in a screen of a mixed stage Globodera pallida expression library. Comparison of the deduced amino acid sequence of this molecule with other collagens suggests it is a cuticular collagen and a member of the col-8 subfamily of collagen genes. Northern blots show the gene is expressed specifically in gravid, adult females of the parasite as compared to second (invasive) stage juveniles and virgin females. Preliminary immunocytochemical studies indicate this collagen is present in areas other than the cuticle; these findings and the potential functional role of this collagen are discussed.

We recovered larval trombiculid mites (i.e. chiggers), vectors of scrub typhus, from small mammal hosts in Taiwan, and compared the relative degree of engorgement (RDE) of the dominant chigger (Leptotrombidium imphalum) from different hosts. Naturally occurring chiggers recovered from Rattus losea and Bandicota indica were 1·4x and 1·3x as engorged as those from Apodemus agrarius. Within each host species, RDE was negatively related to chigger loads, but was mostly unrelated to gender or to body or reproductive condition of hosts. We documented significant variation in chigger engorgement both within and among host species; to the extent that RDE is a proxy for fitness, this contradicts predictions of the Ideal Free Distribution (IFD) that the per capita fitness of vectors should be similar among hosts. Failure to meet predictions of the IFD may reflect the limited mobility of chiggers, which consequently must be less selective in the hosts on which they feed. Further disease control efforts should consider vector feeding success in addition to vector abundance and may be able to capitalize on the unsuitability of certain hosts in supporting disease vectors.

A microsporidian infecting the skeletal muscle of hybrid jundiara (Leiarius marmoratus × Pseudoplatystoma reticulatum) in a commercial aquaculture facility in Brazil is described. Affected fish exhibited massive infections in the skeletal muscle that were characterized by large opaque foci throughout the affected fillets. Histologically, skeletal muscle was replaced by inflammatory cells and masses of microsporidial developmental stages. Generally pyriform spores had a wrinkled bi-layer spore wall and measured 4·0 × 6·0 µm. Multinucleate meronts surrounded by a simple plasma membrane were observed. The polar filament had an external membrane and a central electron dense mass. The development of sporoblasts within a sporophorous vesicle appeared synchronized. Ultrastructural observations and molecular analysis of 16S rDNA sequences revealed that the microsporidian was Pleistophora hyphessobryconis. This study is the first report of a P. hyphessobryconis infection in a non-ornamental fish.

Rats were fed on two deficient diets and were infected with N. brasiliensis larvae. They were autopsied at times ranging from 18 hours to 17 days after infection. The effect of the diets on worm burden, sex ratio of the worms and size of larvae and of worms were noted. Significantly more larvae reached the lungs and intestine in rats fed on glucose and filter paper (G.F.P.) and low protein (L.P.) diets than in controls, the highest numbers coming from G.F.P. rats. Neither the migration rate nor the development of the worms was accelerated by the deficient diets. G.F.P. and control rats lost larvae soon after their arrival in the intestine. Adult worms were lost from rats on the deficient diets before they were lost in significant numbers by controls; this was not due to the initially larger worm burdens in the former rats. G.F.P. and control rats lost the bulk of their infections by 17 days; L.P. rats retained about 50% of the worm burden they had on the fourth day. The effect of the deficient diets on the migratory and adult phase of N. brasiliensis, and on susceptibility and resistance is discussed.

This work was done during the tenure of a Science Research Council Studentship. My thanks are due to Dr E. T. B. Francis for his helpful and critical supervision, and to Professor I. Chester Jones, in whose Department the work was carried out, for the facilities he provided.

Few workers have studied the amino acid requirement of larval Digenea in vivo. Cheng (1963) conducted a study of three species of parasites, each from a different host, and suggested that both free and bound host amino acids act as food sources. His assumptions are based on the disappearance of free amino acids from the sera of infected molluscs and the qualitative similarities between parasite and host with respect to both free and bound amino acids. Negus (1968), working on Turritella communis infected with the sporocysts of Cercaria doricha, described an almost identical qualitative composition of both the free amino acid pools and the hydrolysates of host gonad and parasite tissue. He was of the opinion that this was not coincidental. Considerable quantitative similarities between the free amino acids were also evident. Read, Rothman & Simmons (1963), in discussing cestode metabolism and membrane transport, proposed that it is the molar ratios of amino acids in the host which are important to the parasite and that the amino acid requirement may be more subtle than a simple need for certain components. Indeed, they suggest that this may form one basis for physiological host specificity.

1. The character of the scolex, the long filamentous neck and the morphology of the proglottids are features which justify the establishment of a new genus, Penetrocephalus, to accommodate the pseudophyllid species P. ganapatii (= Both-riocephalus ganapatii (Rao, 1954), B. penetratus (Subhapradha, 1955)) from the marine teleost Saurida tumbil Bloch, off Waltair, Bay of Bengal.

2. The anatomy of the female reproductive system is described in detail, and a preliminary interpretation of the histochemistry of egg-shell formation is given.

3. On the basis of histochemical tests it is suggested that Mehlis's gland, which surrounds the cellular ootype, secretes a phospholipid-like material which may aid in the release of shell precursors from the vitelline cells, but it does not form part of the shell. It appears also to be responsible for the synthesis of PAS-positive yolky matter found in these cells in the egg capsule. The functions of Mehlis's gland in helminths are discussed.

4. In a majority of helminths where the egg-shell is a quinone-tanned protein, it is considered that it is solely if not entirely derived from shell globules in the vitelline cells.

The biggest threat to the war on malaria is the continued evolution of drug resistance by the parasite. Resistance to almost all currently available antimalarials now exists in Plasmodium falciparum which causes the most suffering among all human malaria parasites. Monitoring of antimalarial efficacy and the development and subsequent spread of resistance has become an important part in the treatment and control of malaria. With recent reports of reduced efficacy of artemisinin, the current recommended treatment for uncomplicated malaria, there is urgent need for better methods to recognize and monitor drug resistance for effective treatment. Molecular markers have become a welcome addition to complement the more laborious and costly in vitro and in vivo methods that have traditionally been used to monitor drug resistance. However, there are currently no molecular markers for resistance to some antimalarials. This review highlights the role of the various genetic and genomic approaches that have been used in identifying the molecular markers that underlie drug resistance in P. falciparum. These approaches include; candidate genes, genetic linkage and genome-wide association studies. We discuss the requirements and limitations of each approach and use various examples to illustrate their contributions in identifying genomic regions of the parasite associated with antimalarial drug responses.

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 main components of the schistosome tegument were found to be neutral glycoprotein and phospholipid; a small quantity of glycolipid was observed in the male dorsal tegument. The tegument can be differentiated from other schistosome tissues on the basis of enzyme content; three hydrolytic enzymes were shown to be specifically localized in the tegument: alkaline phosphatase, adenosine triphosphatase and indoxyl esterase. It is suggested that these enzymes could be used as intrinsic markers for tegument structures. The subtegumental cells appear to be the major sites of biosynthetic activity since they contain large amounts of RNA and mitochondrial enzymes.

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.

A re-examination of the haptoral sclerites forming the clamps, or ‘armoured suckers’, in Diclidophoroidea shows that they can be grouped into four main types, representing lines of evolution from what is here regarded as the primitive, or more generalized, form of clamp, that of the family Mazocraeidae. It has been shown that the form of the clamp skeleton must be regarded as of primary importance in the classification of the superfamily, since not only is it correlated with certain diagnostic characters of the soft parts of these worms, but it is usually fully developed some time before these parts make their appearance. Due attention has not always been paid to the detail of the clamps in systematic works, so that the position of some forms must remain uncertain until they can be redescribed. Owing to the sclerites often being twisted bars, curving through three dimensions, with the primary bars often jointed or fused, the appearance of different types of clamp is at first sight highly complex. The difficulty of interpreting them is increased by their being semi-transparent, and appearing of different shapes when viewed from various angles. These obscurities disappear when they are regarded as modifications of the fundamental plan found in Mazocraës and its allies.

Two new species of coccidia, Eimeria gourai sp. nov. from the Victoria crowned pigeon (Goura victoria Fraser) and Eimeria duculai sp.nov. from the Torres Strait imperial pigeon (Ducula spilorrhoa Gray) have been described. Eimeria gourai oocysts are spherical to sub-spherical in shape, measure 20·0 (19·0–22·0) × 20·0 (18·0–21·0) μm and are devoid of micropyle and oocyst residuum. Elongate sporocysts are 12·0 × 5·5 μm, and contain a granular residuum. Eimeria duculai oocysts are broadly ovoid with an inconspicuous micropyle at the narrower end. They are 28·0 (26·0–31·0) × 25·0 (23·0–27·0) μm in size, without residuum but with a membrane-bound polar granule. The elongate sporocysts are 15·5 × 7·2 μm, with prominent Stieda body and granular, membrane-bound residuum. The morphological characteristics of the known coccidian oocysts from birds of the avian order Columbiformes are reviewed.

Several recombinant Trypanosoma cruzi proteins previously isolated were used as antigens to analyse antibody specificities present in sera from human infections. Some parasite proteins such as SAPA (Shed Acute Phase Antigen) are antigenic early after infection. Others, like antigens 1 and 30, are antigenic mainly during the chronic phase of the infection. To understand why different proteins are antigenic at different periods of infection, specificities of antibodies present in the sera of infected mice were compared with the antigens expressed by parasites collected directly from blood. Parasites collected during the acute parasitaemia peak expressed not only antigen SAPA, but also antigens 1 and 30. However, only antibodies against SAPA were frequently observed during the early period and also in the chronic phase of murine infection. Long-lasting antibodies against SAPA were detected regardless of the mouse and parasite strains used. Furthermore, all 8 recombinant clones detected in a T. cruzi expression library with pooled sera from acutely infected mice were homologous to the SAPA gene. These results show that even though parasites from the acute parasitaemia peak in mice may express simultaneously several proteins known to be antigenic, only antibodies against SAPA were consistently detected.

The faeces of five elands (Orias canna syn. Taurotragus oryx) from Ascania Nova (Ukraine) were examined after concentration by Darling's method. Coccidial oocysts were found in the faeces of one of the animals. The oocysts were 21–24μ in length and 15–19μ. in breadth, with an average size of 21·1×17·8 The largest measured 24×19μ and the smallest 21×15μ The shape-index was 1:0·71–0·85, with an average of 1:0·85.

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.

Thirty-five lambs (14 weeks old), the progeny of Border Leicester rams mated with Border Leicester × Merino ewes were divided at random into two groups. Seventeen lambs received 3500 Haemonchus contortus larvae at weekly intervals (weekly group) and 18 lambs received 500 larvae each day (daily group). The dosage was decreased to 1400 and 200 larvae respectively after 8 weeks.

The daily infection with a small number of larvae induced a severe anaemic condition with the blood picture falling to 7% PCV; 2% Hb conc. and 1·6m/mm3 RBC count in 78 days. The anaemia with weekly dosing of larvae was less severe with equivalent figures of 10–12% PCV; 4% Hb conc and 3·6m/mm3 RBC count.

Two phases were observed in the changes in the sodium (Na+e) and potassium (K+e) electrolyte concentrations. In the first phase (K+e) increased and (Na+e) decreased, while in the second phase both electrolytes increased. The influx of young red blood cells into the circulation is considered as the factor responsible for these changes.

When infected with equal numbers of eggs of Amplicaecum robertsi normal male mice harboured more larvae than normal females. Treatment of the mice with thiouracil and thyroxine eliminated the differences between the sizes of the worm populations shown between the sexes in normal mice.

Thiouracil treatment increased the susceptibility of mice to A. robertsi infection, but caused a stunting of the larvae. Thyroxine treatment had no effect on the host–parasite relationship.

It is suggested that the differential ability of the larvae to hatch, penetrate the tissues of the host and migrate to the liver in thiouracil- and thyroxine-treated mice was responsible for the differences in the sizes of the larval populations observed.

This investigation was carried out during the tenure of a Senior Research Fellowship from the Wool Research Board of Australia. I should like to thank Professor J. F. A. Sprent for his continued interest and Mr C. Wilkinson for his careful assistance.

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.