The effects of cercarial concentration and length of exposure on the infection of mice by St Lucian Schistosoma mansoni cercariae were investigated in a running-water habitat.

For all exposure times, mice exposed to cercarial concentrations from 2·5 to 40 cercariae per mouse acquired no infections. At higher concentrations, infection rates and worm burdens of mice increased in direct proportion to cercarial concentrations and exposure times. The highest infection rate (57·9 %) and worm burden (46 worms) were obtained in mice exposed for 256 mm to 1280 cercariae per mouse.

Cercarial concentrations are low in St Lucian running waters, a fact suggesting that the risk of persons becoming infected while fording, collecting domestic water, washing clothes and swimming in habitats with reasonable flows is very low. It appears that most infected individuals acquire a low worm burden over a rather long period of time.

The length of life at various humidities of unfed flies and of flies fed for 1 day and 6 days on diets of meat, sugar and water, sugar and water, meat and water, and water alone, is discussed. The continued feeding of flies on a diet of meat, sugar and water brings about a shortening of their life at all humidities when the flies are starved owing to their increased rate of metabolism. Flies fed on sugar and water are more resistant to humidity than flies fed on meat, sugar and water, and the females are more resistant than the males. Flies fed on meat, sugar and water lose weight more rapidly than flies fed on sugar and water.

High humidity is more favourable for growth of the ovaries than low humidity. Humidity has no effect on oviposition at temperatures of 10–35° C., but at 40° C. low humidity is unfavourable.

The ultrastructure of the formation of the first-stage cuticle within the egg of Trichostrongylus colubriformis is described. The first indication of cuticle formation was the formation of the epicuticle external to the epidermal plasma membrane. This becomes thickened to form the epicuticle of the fully formed cuticle. Microtubules and microfilaments associated with the epidermal plasma membrane were observed during the early phases of cuticle formation. The basal zone was secreted into the space between the epicuticle and the epidermal plasma membrane, followed by the formation of the cortical zone. The basal zone had a striated appearance during the earliest stages of its formation.

The four distinguished German men of science to whom the following biographical notes relate: Robert Koch (1843–1910), Paul Ehrlich (1854–1915), Emil von Behring (1854–1917), and Friedrich Loeffler (1852–1915), form a group of singular interest because of the relations that existed between them and the various problems to the solution of which they devoted their remarkable talents and energies. Each of them has left an indelible mark upon the annals of research and discovery in relation to infective diseases of man and animals, their etiology, prevention and cure. If it were at all possible to reckon up the sum of human and animal lives that they have saved from premature extinction through their collective efforts, direct and indirect, the total would attain gigantic proportions. Mankind should ever keep these men in grateful memory.

The energy requirement of pregnancy reflects a problem which contains a great deal of uncertainty. To supply the theoretical energy needs for the increases in maternal and foetal tissues and to cover the elevated basal metabolic rate involves an amount equivalent to an extra 250–300 kcal/day on average, but in real-life situations there is seldom a rise in dietary energy of a comparable quantity. Data from co-ordinated longitudinal studies in four countries, together with results from other published papers, show energy intakes increasing by only 100–150 kcal/day, and only in the third trimester. Although it is difficult to demonstrate, the probability is that there are energy savings in reduced physical activity which compensate for the larger energy needs.

Under the research programme of the U.S. Public Health Service, Communicable Disease Centre Activities, the parasitic fauna of rodents and insectivores of the United States are coming into the laboratories in great numbers, and it has been my good fortune to have had the opportunity to examine a fair number of the parasitic mites collected from a diversity of hosts.

On many occasions during the years 1921 and 1922 I devoted my leisure to collecting Cestode and other Helminth parasites from wild birds in the United and Central Provinces of India. A large proportion of the material collected consists of species already known but the remainder contains some new and interesting forms, and three of these I am describing in the present paper.

Various stages in the life cycle of Panopistus pricei are reported from Agriolimax agrestis. These are essentially the same as those reported by Krull from Zonitoides arboreus. The excretory system of a developing metacercaria is described.

This study addresses the humoral and cellular basis of specific acquired immunity in the guinea-pig irradiated vaccine model of schistosomiasis mansoni. Rodents vaccinated with 500 gamma-irradiated cercariae and then splenectomized 4·5 weeks later showed a 33% reduction in resistance to challenge as compared to vaccinated animals or vaccinated/sham splenectomized controls. Serum harvested from once vaccinated individuals conferred modest levels of resistance upon naive recipients in some experiments, but transfer was not achieved consistently. Serum from vaccinated and thrice boosted rodents (Vbbb) routinely transferred around 45% immunity, however, provided it was given in 4 ml aliquots on day 9 post-challenge; Vbbb serum thus transferred 50% of donor immunity. Interestingly, multiple doses of this protective serum given on and either side of day 9 did not enhance the protection achieved with a single 4 ml aliquot. Neither peripheral lymph node cells nor splenocytes from the polyvaccinated serum donors were able to transfer resistance to recipient guinea-pigs and they failed to augment the protection achieved with Vbbb serum. Food-pad testing revealed no correlation between delayed hypersensitivity responses and immunity to challenge in vaccinated guinea-pigs. Although polyvaccine guinea-pig serum successfully protected homologous recipients, it failed to protect mice when administered either at the time of challenge (the optimal schedule for transfer of polyvaccine mouse serum), or around day 9 (the optimal schedule for guinea-pigs). Similarly, guinea-pigs could not be protected with polyvaccine rat serum that conferred 75% resistance upon naive recipient rats.

In the following pages an attempt has been made to give a short summary of our knowledge of the Relapsing Fever of Tropical Africa, and also to include the results of my own experiments and observations on this disease. The literature on the subject is already somewhat considerable and widely scattered, therefore no apology is needed for bringing it together.

Most of the observations recorded in this paper would have been published in 1915, if my duties as a doctor and as an officer had not called me to the Army.

Using an age-fractionated RBC model, we investigated the in vitro sensitivity of artemether in β-thalassaemic RBC infected with the K1 and FC27 strains of Plasmodium falciparum and, to study the role of oxidant stress in modulating the sensitivity pattern, pro-oxidant (riboflavin) and antioxidant (vitamin E) agents were added to cultures in the presence of artemether. With the FC27 strain, the artemether IC50 doses in thalassaemic samples (whole blood and fractions) were significantly higher compared to equivalent normal RBC samples (P<0·05). However, with the K1 strain, such a significant difference was not demonstrable. The addition of vitamin E reduced the antimalarial effect of artemether in both the FC27 and K1 strains (P<0·0001). In contrast, the addition of riboflavin resulted in a significant increase in antimalarial activity (P<0·0001). This effect of the drug combinations was not influenced by the red cell type (P<0·0001) and there was no interaction between red cell type and drug type (P<0·0001). These findings show that reduced sensitivity to artemether occurs in whole blood and age-fractionated β-thalassaemic trait RBC. It appears that the RBC redox status does not influence the sensitivity to artemether.

A method of breeding and maintaining L. natalensis cultures in the laboratory is described.

The infection of snails with F. gigantica miracidia and the collection of metacercariae is discussed. The mean number of metacercariae arising from cercariae produced by each snail was 652·6, over a period of 8·2 days.

It is shown that after 3 months storage F. gigantica metacercariae are still viable when excysted in vitro by using artificial pepsin and trypsin enzymes.

The author wishes to express his thanks to Dr G. M. Urquhart of the Wellcome Laboratories for Experimental Parasitology, University of Glasgow, Veterinary Hospital, Bearsden Road, Bearsden, Glasgow, who has read through this paper and made the necessary corrections.

Information on the ultrastructural details of fertilization in filarial nematodes are still unavailable. Here we report new data on this process in Dirofilaria immits, the heartworm of dogs and cats. Electron microscopy allowed us to observe oocytes engulfing spermatozoa through an endocytosis-like process. We also observed spermatozoa inside the oocytes which still possessed their plasma membrane and which were clearly enveloped by a further membrane, likely derived from the endocytosis process. At this stage, at the interface between the sperm membrane and the endocytotic membrane (vacuolar space), we observed flocculent material in the proximity of the membranous organelles (MOs) of the sperm. In the proximity of the MOs, we also observed the enlargement of the vacuolar space. Other images showed the dissolution of the sperm membrane, and the release of nuclear masses and organelles in the egg cytoplasm. We did not observe the fusion of lysosomes to the endocytotic vacuoles. In addition, the lysis of the sperm organelles has never been observed inside the vacuoles containing the whole sperm. Thus we suggest that the degradation of the endocytotic and sperm plasma membranes is determined by material released by the MOs. Since we did not observe the entry of sperm into the oocytes by other mechanisms, we also suggest that endocytosis is the normal process used by the spermatozoon to get into the egg cytoplasm in D. immitis. Finally, during our observations of the seminal receptacle we did not observe any structure in the spermatozoa which could be interpreted as an intracellular bacterium. This is consistent with previous results indicating that the bacterium Wolbachia in filarial nematodes is not transmitted through the sperm.

A genomic library of Meloidogyne incognita Race 1 has been prepared in the bacteriophage λgt10 and screened for specific DNA sequences by hybridization with radio-isotope labelled total genomic DNA from a number of Meloidogyne species. One clone isolated (MR1#15), although not totally species specific, clearly showed preferential hybridization to M. incognita. Following subcloning and sequencing of the 255 bp insert, four stretches of the sequence corresponding to oligonucleotides of approximately equal length (~60 bp) were synthesized and examined for specificity. One of them, MR1#15.2, showed the necessary specificity to be used as a diagnostic tool.

New treatment strategies for schistosomiasis should be evaluated, since resistant strains to the only available drug, Praziquantel, have already been described. Thus, we demonstrated antiparasitic effects of ethanolic extracts of Jatropha gossypiifolia and Piper arboreum on cercariae and adult worms of Schistosoma mansoni. The bioassays were performed at 0–10 000 μg mL−1 concentration for 0–72 h. Adult worms were stained with carmine to assess external and internal damage. The chemical screening was performed using high-performance liquid chromatography. P. arboreum displayed the best cercaricidal effect, with a 100% reduction in viability in just 60 min. The extract of J. gossypiifolia was more effective against adult worms, with 100% viability reduction of male and female worms after 12 and 24 h, respectively. P. arboreum and J. gossypiifolia were equally effective in inhibiting the oviposition of S. mansoni (93% reduction) and causing damage to internal and external structures in adult worms. Flavonoids were identified in both the extracts and phenolic compounds and amides only in P. arboreum. Thus, for the first time, it was proven that ethanolic extracts of P. arboreum and J. gossypiifolia leaves are biologically active against cercariae and adult worms of S. mansoni in vitro.

During the summer months in Mesopotamia body-lice become extremely scarce on man, so much so that it may be difficult to find them even on men who are renowned for lousiness at other seasons of the year. When the nights become cold, as they often do rather suddenly towards the end of November, lice rapidly become numerous, this coinciding with the reissue of winter under-linen which has been stored through the summer in Ordnance dumps.

Quantitative paper chromatography and radioactive tracers were used to study the flux of alanine through the sporocysts of Cercaria emasculans in vitro. The following evidence indicates that simple diffusion is the main mechanism of permeation: (1) the sporocysts cannot accumulate alanine against a concentration gradient; (2) the concentration of alanine in the sporocysts is a direct linear function of the concentration of alanine in the external environment; (3) addition of 10−2 M glucose to the medium does not enhance permeation; (4) neither heat-killing the sporocysts nor treating them with 10−3 M iodoacetate slows the rate of permeation; (5) the Q10's for the permeation are similar to those to be expected in a process involving simple diffusion; (6) the amino acid molarities in the parasite and host tissues in vivo are strikingly similar. No utilization of alanine during the course of 3 h incubations could be detected by autoradiography.

The dynamic nature of the equilibrium between the sporocysts and the external environment is emphasized by the exchange of alanine that occurred even under isotonic conditions.

Fresh sporocysts leaked alanine and proline during 1 and 4 h incubations in vitro. The significance of this is not known.

The commencement and duration of haemolysis and the length of time the erythrocytes remain intact in engorged virgin and fertilized females and in male Ornithodoros savignyi were investigated by means of red cell antigens.

There were no differences between fertilized and unfertilized females, haemolytic tests were possible in both groups up to 120 h after engorgement.

In the male group haemolytic tests were possible only up to 24 h after engorgement.

In both female groups inhibition of the in vitro haemolysis could be observed until the fifth day, after feeding on a calf with erythrocyte mosaicism, indicating the loss or masking of antigens due to the damage of cell walls.

The authors wish to thank Dr G. Theiler for her interest and advice during this work.