1. An increase in resistance to metachloridine of more than 100-fold was obtained within a few weeks in a strain of Plasmodium gallinaceum treated with gradually increasing doses of the drug and maintained in young chicks by blood-inoculation at intervals of 2–3 days.

2. There was no evidence that the rapid development of resistance arose by the selection of highly resistant individuals present in the normal population.

3. Two strains of P. gallinaceum passaged through chicks treated with 0·025 mg. doses of the drug gradually became resistant to greater concentrations than that to which they had been exposed, though their growth rate decreased when they were inoculated into birds receiving higher doses of the drug.

4. In both strains maintained in birds treated with 0·025 mg. doses of the drug, resistance reached a maximum beyond which it did not increase.

5. Cross-resistance tests failed to show any relationship in mode of action between meta-chloridine and pamaquin, mepacrine, quinine or chloroquine. A strain of P. gallinaceum, highly resistant to metachloridine, showed slight resistance to sulphadiazine, sulphapyridine and sulphathiazole, but none to sulphanilamide or proguanil.

We are indebted to the Cyanamid Products Ltd., London, for the gift of the Folvite used in these experiments.

Natural populations of 3rd-stage Nematodirus battus larvae were present on pastures in North Wales throughout the year; highest numbers were present in late spring, with smaller peaks occurring in autumn. Inter-site variation was observed in the timing and magnitude of these peaks. Hatching on experimental plots occurred 2 months to 2 years following deposition of eggs. Intraspecific and inter-site variation occurred in the timing, and inter-site variation occurred in the magnitude, of the mass hatch on upland and lowland experimental plots. Arrested 4th-stage N. battus were recovered from Welsh Mountain lambs. Percentage arrest and number of arrested worms was greatest during winter and early spring. The prevalence and intensity of N. battus infection in 1-, 2- and 3-year-old Welsh Mountain ewes was low. The plasticity exhibited in the parasite's life-history is discussed in relation to potential changes in the epidemiology of nematodiriasis.

Eupelmella vesicularis Retz. was found in certain parts of Hungary infesting cocoons of Diprion sertifer Geoff. already parasitized by a primary parasite, Microplectron fuscipennis Zett. It was never found in the absence of this chalcid.

Experiments showed that Eupelmella confined itself almost exclusively to Microplectron as a host, easily detecting the presence of larvae or pupae of this parasite within the cocoons of the saw-fly host, but neglecting eggs.

A single egg is laid per cocoon and the larval Eupelmella eats from 10 to 20 Microplectron larvae or pupae, and finally kills all the remaining living parasites within the cocoon before pupating.

The egg and larva show interesting structural adaptations for this mode of life.

Reproduction is parthenogenetic and no males are known.

Several factors combine to make this insect a dangerous enemy of Microplectron capable of seriously impairing its efficiency. These are: its selective ability, its destructive powers, its rapid rate of increase due to the parthenogenetic habit, and its ability to establish itself and survive on small numbers of the prey, for the same reason.

Monthly data collected during 1993 in the Vaccarès lagoon (Rhône Delta, France) were used to investigate the influence of the trematode Aphalloïdes cœlomicola on the survival of the common goby Pomatoschistus microps, which acts both as second intermediate and definitive host. Prevalence of the parasite did not increase with fish size in either sex. Mean abundance and variance to mean abundance ratio gave evidence that the trematode could have an impact on host mortality. Gonad weight of parasitized females was reduced and the parasite seemed to provoke a gonadal regression above a certain parasitic biomass. Fecundity and egg diameters did not differ between parasitized and unparasitized females, we thus hypothesize that the energy content of eggs (composition in lipids and proteins) was probably modified as an adaptation to energy losses. Prevalence of infection in males compared to females and influence of the parasite on host survival and reproductive effort are discussed.

1. Several behaviouristic and physiological differences distinguish the two species Trichogramma semblidis and T. evanescens (tabulated on p. 514).

2. There are no true intermediates between the two forms of the male T. semblidis, but intermediate types are simulated by degenerate individuals of small size produced by starvation.

3. Among 1740 males reared from eggs of Sialis and 1847 reared from eggs of moths, there were only nineteen exceptions to the rule that the apterous form emerges from the former and the winged form from the latter.

4. The ability of T. semblidis to produce its apterous male can remain latent through as many as sixty-four generations reared on Sitotroga and yet find its full expression immediately when the parasite is reared on Sialis.

5. Several other species of Neuroptera have been parasitized, but Sialis lutaria remains the only known host that regularly elicits the apterous form.

6. T. semblidis is capable of arrhenotokous parthenogenesis. The statement that the species includes thelytokous strains requires corroboration.

Obesity is the main causal factor for metabolic syndrome and chronic systemic inflammation, which impacts on immune function and increases susceptibility to pathogens. Here, we investigated the effect of obesity on the outcome of visceral leishmaniasis caused by Leishmaniasis infantum chagasi. C57BL/6 mice fed with high-sugar and butter diet (HSB) showed a significant increase in body weight, adiposity index and morphological changes in adipocyte. To investigate the consequences of obesity on the specific immunity against Leishmania, both control and HSB diet groups were infected with 107L. infantum chagasi promastigotes in the eighth-week after diet started and euthanized 4 weeks later. HSB-diet fed mice exhibited a significantly higher parasite burden in both liver and spleen compared with control- diet group. Gonadal adipocyte tissue from HSB-diet mice showed increased TNF-α, IL-6 and leptin and diminished IL-10 production compared with control. Cytokines production analysis in the spleen and liver from these animals also demonstrated higher production of IFN-γ, TNF-α, IL-6 and nitric oxide and diminished production of IL-10 and TGF-β, which correlate with inflammatory foci and the cell hyperplasia observed. Taken together, obesity can interfere with responses to pathogen-derived signals and impair the development of protective anti-Leishmania immunity.

1. A Heteromita species, probably Heteromita globosa, is described and the methods of culture and observation are detailed.

Heteromita globosa is a flagellate with a karyosome nucleus. The karyosome body is an achromatic structure. The chromatin lies on or around the periphery of the karyosome as a narrow diffuse layer and is also distributed upon the inner side of the nuclear membrane. There are two unequal flagella which arise from two blepharoplasts which are situated close together at the anterior end of the body. The blepharoplasts are connected with the nuclear membrane by fine rhizoplasts.

2. The division, encystation and excystation of the flagellates are described from living and stained material. The nuclear division is characterised by a well-developed spindle and the chromatin is arranged in an equatorial plate at the metaphase. The blepharoplasts play the part of centrosomes in the division of the nucleus.

3. The normal division in the living state takes 7 to 15 minutes. The blepharoplasts can be seen to separate, the nuclear space becomes hyaline and ceases to refract in the characteristic way, the space elongates, the blepharoplasts each with the flagellum attached come to lie at opposite poles of the elongating organism and a second flagellar rudiment can be seen to arise at each end alongside of the original one. The nuclei can be observed to reconstruct and the protoplasmic body draws apart rapidly, leaving a narrow protoplasmic junction which breaks through and the two daughter individuals separate.

4. A process of delayed division was observed. If after the division of the nucleus and the drawing apart of the main bulk of the protoplasm the actual breaking of the narrow junction between the two daughters fails to take place immediately, there seems to be no means of effecting this actual separation until the occurrence of a new nuclear division.

In the course of a few hours, usually 3 to 6, a second division occurs and each nucleus undergoes mitosis and the creature splits into four daughters.

The double individuals may encyst and when they emerge they do so as a single binucleate protozoan equipped with a double flagellar apparatus.

5. Syngamy has not been observed.

The worm burden distributions of a macrofilarial nematode, Ochoterenella digiticauda, and a gastroenteric digenean, Mesocoelium monas, were examined in a naturally infected population of Bufo marinus from Jamaica. Both parasite species had over-dispersed distributions which were well described by the negative binomial probability model (k = 0·35 for 0. digiticauda; and k = 0·59 for M. monas). The intensity distributions of the two parasites were uncorrelated: there was no significant association between the intensity (whether absolute or relative) of infection of either parasite in individual hosts. It is suggested that different, and parasite species-specific, factors of the host interaction are involved in generating the separate distributions of the two parasite species.

Amongst parasitic platyhelminthes three Microsporidia are named from cestodes and seven from trematodes. Those in cestodes are Nosema helminthorum Moniez, 1887, Glugea ghigii Guyenot & Naville, 1924 (= Nosema (Plistophora) ghigii Guyenot, Naville & Ponse, 1925) and Stempellia moniezi Jones, 1942. Those in trematodes are Nosema distomi Lutz & Spendore, 1908, Nosema legeri Dollfus, 1912, Nosema echinostomi Brumpt, 1922, Nosema (Plistophora) spelotremae Guyenot, Naville & Ponse, 1925, Glugea encyclometrae Guyenot & Naville, 1924 (= Nosema (Plistophora) encyclometrae Guyenot, Naville & Ponse, 1925), Glugea ghigii Guyenot, Naville & Ponse, 1924 (= Nosema (Plistophora) ghigii Guyenot, Naville & Ponse, 1925) and Nosema dollfusi Sprague, 1964. Other species are recorded but not named.

Although Filaria volvulus was first described by Leuckart IA 1893, very little was known or taught of this particular nematode when, ten years later, I became a goverament official in Northern Nigeria. While other members of the Filaridae have received a good deal of attention during the present decade, Filaria volvulus seems to have been comparatively ignored. I am inclined to think, however, that this Filaria is far more common in certain parts of Africa than is generally supposed; and, by publishing the cases that have come under my notice, I hope that something may be added to our knowledge of the obscure disease it causes and that other workers will become interested in the subject. Up to the present time I have seen five cases, and ali of these carne under observation at Lokoja—a large government station in Northern Nigeria, situated at the confluence of the Niger and Benue rivers. To my knowledge this is the first time that cases of Filaria volvulus have been reported from Northern Nigeria.

From 24 May to 4 July 1961 about 12,000 roach, Rutilus rutilus (L.), died in a lake at Brynmill Park, Swansea, South Wales. Even this high figure may be an underestimate of the actual mortality rate as it is based entirely on extractions of dead fish from the surface waters by members of the Brynmill and District Angling Club, who used landing nets from the shore only, although at fairly regular intervals. The daily counts of dead roach are represented on a histogram (Text-fig. 1). It is also of interest that in the early summer of 1961 large numbers of roach succumbed in other regions of the British Isles; about 30,000 died in the River Trent, Derbyshire, and 3000 in the lake in St James's Park, London. Newspaper reports in both localities attributed the cause to a deficiency of oxygen. For the outbreak in South Wales, however, similar reports suggested that ‘white spot disease’ caused by the ciliated protozoan Ichthyophthirius was responsible for the mortality.

Having during the last few years been particularly interested in the Nematode parasites of horses and donkeys I was very pleased to find a tube containing Strongyles from the zebra among some material recently forwarded to me by Professor G. H. F. Nuttall, F.R.S. These worms formed part of a collection of Helminths from Nairobi, British East Africa, which had been sent for identification by Mr R. Eustace Montgomery, Director of the Nairobi Veterinary Pathological Laboratory.

Townsend (1935) has described the egg of Synthesiomyia nudiseta and recorded the interesting fact that the larva forms a cocoon. The larval stages and the puparium do not appear to have been described. That this species was not among the larvae of some unknown muscids described by Banks (1912) is evident from the figures of the-posterior spiracles. The present communication provides an account of all the early stages.

Host metabolic changes have been observed to affect Schistosoma mansoni egg production, worm survival and morphology. We examined worms recovered from streptozotocin-induced diabetic mice by morphometric and morphological analysis through brightfield and confocal laser scanning microscopy. Tegument thickness was slightly smaller and changes in the reproductive organs were observed in 23–30% and consecutively 88–100% of the worms. The testicular lobes had a large diminution of cells in one or more of the lobes, which was associated with a lack of spermatozoids in the seminal vesicle. Ovaries were atrophied, manifested by a complete or large reduction in oocytes but other parts of the reproductive system like the vitelline glands were mainly unaffected. Streptozotocin (STZ) instead of hyperglycaemia caused the degeneration since worms from mice injected with a non-diabetogenic dose, or with nicotinamide to prevent diabetes showed the same alterations. The drug did not affect worm survival or pairing. We conclude that STZ, an alkylating agent that provokes chromosome and DNA damage, changes the morphology of ovaries and testicular lobes in S. mansoni worms in vivo. This is the first report of STZ action in helminths and we suggest that STZ affects oogenesis and spermatogenesis and might cause sterilization of schistosomes.

Experimental studies of parasite transmission are essential for advances in basic and applied parasitology. A survey of the results of published experiments can identify the determinants of both variation among studies in experimental design and of parasite infection success. Here, analyses are conducted on data compiled from a total of 106 metacercarial infection experiments (35 on Echinostomatidae, 37 on Fasciolidae, 34 on other trematodes) obtained from 83 studies. All of these involved experimental oral infection of individual definitive hosts by a single known dose of metacercariae under controlled conditions. Across these studies, the metacercarial dose used (i) was typically about 10 times higher than the average natural dose that could be acquired by feeding on intermediate hosts (for taxa other than Fasciolidae), and (ii) showed a positive relationship with the body mass of the definitive host, although this relationship was only significant for Fasciolidae. Although the chosen dose was rarely justified, the larger the definitive host, the more metacercariae it received. Among Echinostomatidae and Fasciolidae, there was also a significant dose-dependent effect on infection success: the higher the dose used in an experiment, the smaller the proportion of metacercariae recovered from the host. This effect was mitigated by definitive host body mass, with infection success being generally lower in larger definitive hosts. For Echinostomatidae, the taxonomic identity of the definitive host also mattered, with metacercariae achieving higher infection success in mammals than in birds. The present findings suggest that the design of experimental infection studies requires greater consideration if their results are to yield useful biological insights.

Young chickens given an infection of 5000 oocysts of E. maxima were highly resistant when they were given a 2nd dose 3 weeks later. Immunity in these fowls was not apparent when they were again infected 10 weeks after the 2nd infection. The same fowls given a final dose 26 weeks after the 3rd infection became heavily infected. These observations suggest that immunity developed to this infection is short-lived, and this finding is discussed in relation to the duration of acquired immunity to E. tenella infection in the fowl and E. stiedae infection in the rabbit.

The microaerophilous stationary phase system (MASP) was introduced in 1980 and successfully used as a standard technique for Babesia bovis and B. bigemina in vitro culture. The percentage of serum in the medium and the dependence on specific serum donors have been recognized as important constraints both for immunochemical studies and for the logistics of culture routine. In the present study the supplementation of RPMI 1640 with hypoxanthine at a concentration between 50 and 200 μM has enabled patterns of growth of B. bovis and B. bigemina to be achieved comparable to the standard technique with a simultaneous reduction of serum concentration from 40% to 5%. With hypoxanthine-supplemented medium it was possible to either replace the bovine serum from a specific donor with horse serum or use commercial adult bovine serum or foetal calf serum at 10%. When the serum replacement media Albumax II and GF21 were used, the growth of both B. bovis and B. bigemina markedly decreased after 3×72 h cycles. However, when these species were cultivated in culture flasks previously coated with cells from a murine peritoneal lavage, continuous parasite growth was achieved.

1. The paper describes an experimental study on the effect of atmospheric humidity upon Rhadnius. The work was carried out on fasting males of known age, kept at 23° C. at different relative humidities; the proportion of water was determined after the lapse of definite periods of time. The normal male contains 30 per cent. of dry matter.

2. Taking the results after 42 days' starvation, at 30, 60 and 90 per cent. humidity, the weight of each group of bugs has fallen to 50 per cent. of what it was at the start of the experiment. Those kept in damp air have lost dry matter and water in the same proportion, so that the percentage of dry matter after starvation is still 30 per cent. of the total weight. Those kept in drier air lose more water but oxidise less dry material, so that the proportion of solids rises during starvation: in those kept at 30 per cent. relative humidity the proportion of solids rises to 39 per cent. The figures for insects kept at 0 per cent. humidity are consistent, but it is not possible to obtain them beyond the 32nd day.

3. Death is probably due to a rise in the concentration of the body fluid and not to the exhaustion of food material. This is shown by the fact that the exhaustion of solid matter is actually less in dry air than in moist, though mortality is only observed among the bugs kept in dry air.

Using indirect immuno- and enzyme-cytochemical techniques, interfaced with confocal scanning laser microscopy and standard optical microscopy, neuronal pathways have been demonstrated in whole-mount preparations of the unpaired diporpae and freshly paired juvenile stages of Eudiplozoon nipponicum (Monogenea: Diplozoidae). All 3 main classes of neuronal mediators, cholinergic, aminergic and peptidergic, were identified throughout both central and peripheral elements of a well-differentiated orthogonal nervous system. Neural mapping revealed considerable overlap and similarity in staining of the nervous systems of the diporpa and adult worm. The main differences in the diporpa relate to the innervation of the temporary ventral sucker and dorsal papilla, structures which are unique to the larva and which enable fusion between worms but then disappear. Branches from the longitudinal nerve cords innervate these structures and appear to be involved in the process of somatic fusion, probably giving rise to the inter-specimen connections that later link the 2 central nervous systems in paired adult parasites. In the hindbody, there is extensive haptoral innervation associated with the developing clamps and small central hooks. Reactive neuronal components were found associated with the early stages of clamp development prior to connections being made with the extrinsic adductor muscle bundles. The muscle systems of the diporpa and juvenile stages comprise a lattice-like arrangement of circular, longitudinal and diagonal fibres that make up the body wall, together with buccal suckers, haptoral clamps and associated adductor muscles, and the transient ventral sucker. All have obvious importance to diporpae when they migrate over the gill and undertake body contact, torsion and fusion during the process of pairing. Behaviour during the pairing of diporpae is described.

The humoral immune response of roach (Rutilus rutilus) to cercariae of the digenean trematode, Rhipidocotyle fennica, was studied. Antibodies against R. fennica were found in wild roach in lakes where fish are infected by the parasite. Antibody levels were higher in sera collected in September than in sera collected in June, due to infection of R. fennica during the late summer. In experimental aquarium studies, roach immunized with homogenized cercariae produced antibodies against R. fennica. An especially strong response was elicited by infecting fish with living cercariae emerging from infected clams. The specificity of the antibodies, as shown in Western blots, was different between fish immunized with homogenized cercariae and those fish infected with living cercariae. The specificity and amount of antibodies depended on the route of immunization. The challenge experiment with R. fennica indicated that previous infection of fish gives some protection against R. fennica.