Because of its ability to cany diseases, the sheep tick should be classed as one of the most important ectoparasites of British sheep. No reason for the differences between individual susceptibility to infestation has been found.

Commercial arsenical dips are excellent acaricides, but give little protection from reinfestation, and are no better than watery solutions of sodium arsenite at the same concentrations of arsenic. In the work reported, addition of derris to the commercial dip did not improve it.

Coal-tar fractions which were tested were of little value in tick control, and five finely divided inert powders were not acaricidal.

D.D.T. and B.H.C. give promise of being of real value in controlling ticks; since the former is not effective against sheep scab, it is suggested that future research on anti-tick dips be confined to preparations containing B.H.C., the γ content of which is probably about as effective as D.D.T. against ticks when used at a 5 times greater dilution. Two commercial dips containing B.H.C. were found to be of little value.

A method of anti-tick treatment which involves walking sheep through a shallow bath of dip holds great promise.

Treatment of pastures with D.D.T. appeared to have no effect upon the tick population, and neither D.D.T. nor B.H.C. was effective against ticks when administered to sheep per os.

By stocking a pasture with sheep which were dipped sufficiently often to prevent any female tick from engorging, the tick population was almost completely eradicated in one year. Sheep which were born in the pasture in April 1948, and remained there until October 1949, were not dipped during 1949 and, as far as is known, were not at any time infested by ticks. Pastures from which all sheep were excluded gradually lost their tick populations, but a few ticks remained at the end of 3 years. This may be because, in the main enclosure, almost every tick would have an opportunity of attaching on a dipped sheep, and would be killed; in the unstocked enclosures, lack of opportunity to attach on sheep would result in a larger number of ticks infesting wild animals and so a few ticks would be carried over from year to year. This result is unlikely to have any practical application at present, because ridding a small area (e.g. a farm or a valley) of ticks would result in the sheep of that area losing their immunity to tick-borne diseases, and re-introduction of ticks might bring disastrous results. Also, it should be pointed out that work quoted in the text gives the result of an attempt at eradication in one county of Britain. Among other things, the fact that cattle, hare, and deer were absent immediately prohibits application of the results to many other areas of Great Britain. However, it appears that, in the absence of hare and deer, it might be possible to rid an area of ticks by adequate treatment of domestic animals.

It is a pleasure to acknowledge the helpful advice received from Dr H. H. Green of the Veterinary Laboratory at Weybridge, during the course of this work. The work was carried out under the auspices of a coordinating committee of the Agricultural Research Council and is published by permission of that Council, and of the Veterinary Laboratory of the Ministry of Agriculture.

Monoclonal IgM rheumatoid factor-like anti-globulins were produced by in vitro stimulation of naive BALB/c spleen cells with lipopolysaccharide, and by hyperimmunization of mice with merozoites of Plasmodium falciparum, followed by fusion of the spleen cells to mouse myelomas. In vitro, these anti-globulins augmented the inhibitory effects of P. falciparum-specific polyclonal mouse sera and monoclonal IgG1 and IgG2b antibodies by binding to Fc fragments of IgG molecules attached to blood-stage parasites. In some instances, the presence of anti-globulins correlated with an increase in the number of schizonts which failed to disperse merozoites. In other cases, parasitaemia remained low in the absence of the schizont inhibition phenomenon, suggesting that anti-globulins contribute to host cell protection not only by agglutinating merozoites, but also by increasing the density of the antibody coat surrounding the parasites, thus interfering with parasite receptor-erythrocyte ligand interactions. The anti-globulins were not inhibitory when added to parasite cultures containing IgG not specific for P. falciparum. These results may help explain the function of IgM anti-globulins found at elevated serum levels in some patients with malaria or other chronic infectious diseases.

The humidity reaction of the larvae of Xenopsylla cheopis Rothsch. was studied in an air-chamber with a 0–100% relative humidity gradient.

Highly significant differences (P < 0·001) between the reactions in the various R.H. ranges was found. The most preferred relative humidity along this gradient was 100%. Relatively few larvae were collected at each R.H. in the range between 0 and 90% R.H.

The reaction of the larvae under the experimental conditions was seen to be of orthokinetic type.

The purpose of this work has been to identify and describe the immature forms of those species of tachinids which have occurred as parasites of Pierisrapae and P. brassicae at the Imperial College Field Station, Slough, Bucks.

The influence of temperature and salinity on miracidial longevity and miracidial infectivity of the digenean, Himasthla militaris, has been examined. At 14, 25 and 30 °C the half-life of the miracidia was 1200, 630 and 420 min respectively, and infection of the first intermediate host, Hydrobia ventrosa, only occurred at 25 and 30 °C, for both temperatures 52% became infected. In the range 2·1 to 34‰ (2·1, 4·2, 8·5, 17 and 34‰) the miracidia had a minimal and maximal half-life of 60 and 630 min in water with a salinity of 2·1 and 17‰ respectively, while the infection of the snail host was possible only in water with a salinity of 8·5 and 17‰.

In 1892 P. J. van Beneden described and figured among some caligids from Africa and the Azores a new genus and species to which he gave the name Pupulina flores. He claimed to have found both sexes of the new parasite, but acknowledged that he had described as male and female of his species two copepods which had previously been designated by different names. They were found upon the same host, a devil-fish, and he believed that they were of the same species. In this, however, he was mistaken, for the specimen he described as the male was really a young female of an entirely different species. Owing to this mistake, together with the very imperfect description of both sexes, Bassett-Smith in 1899 denied the validity of the new genus and transferred Beneden's species to the well-known genus Lepeophtheirus. Following this lead the present author placed it in a key to the species of Lepeophtheirus published in 1905, and it has remained there up to the present time.

In the last twenty-five years, since it was realized that the control of flock infections was more important than the treatment of individuals with patent infections, there has been an increasing interest in the use of anthelmintic drugs. As might be expected there has been a wide search for the most effective chemicals and considerable research into the best methods of administration, and as a consequence of this many workers have been engaged in devising methods of testing the efficiency of various compounds.

When I first began to think about this presentation I flirted with the idea of reversing the title to read: ‘Immunologists as Parasites’. I could clearly see some of the sectional headings such as ‘The Spreading Cancer of Tumour Immunology’ and ‘Does the International Immunology Scene represent an IDIOT-ype–Anti-IDIOT-ype network’?. But although this might have been fun it would certainly have been unfair to those immunologists who are currently working on Parasite Immunology, a very difficult and demanding field.

Taenia multiceps is a cestode (family Taeniidae) that in its adult stage lives in the small intestine of dogs and other canids. The metacestode, known as Coenurus cerebralis, is usually found in the central nervous system including brain and spinal card in sheep and other ruminants. The presence of cysts typically leads to neurological symptoms that in the majority of cases result in the death of the animal. Coenurosis could cause high losses in sheep farms because the disease commonly affects young animals. A total of 20 C. cerebralis isolates collected from naturally infected sheep in Mardin province of Turkey were characterized through the polymerase chain reaction and sequencing of a fragment of cytochrome c oxidase subunit 1 (CO1) gene. The results showed that the CO1 gene sequences were highly conserved in C. cerebralis isolates. Phylogenetic analysis based on partial CO1 gene sequences revealed that C. cerebralis isolates were composed of three different variants.

It has been observed that fluorescent membrane-impermeant molecules can enter the cercariae as they penetrate mouse skin. The hypothesis to be tested was that such molecules, which included Lucifer Yellow and a variety of fluorescent dextrans, entered the parasite through the nephridiopore and excretory tubules as well as through the surface membrane. FITC-labelled poly-L-lysine (molecular weight 10 kDa), added at 4°C during syringe transformation, was found to enter the nephridiopore and labelled the excretory bladder and sometimes the excretory tubules. This finding indicates that macromolecules (10 kDa) can enter the nephridiopore. It was found that linoleic acid (a normal constituent of skin) greatly stimulated uptake of Lucifer Yellow and dextrans into the excretory/subtegumental region of 2-h-old schistosomula. This correlated with an increased uptake of membrane-impermeant propidium iodide at 37°C. Since increased uptake of propidium iodide occurs when membranes become permeable, the surface membrane could also be a pathway of transport of the membrane-impermeant molecules into the schistosomulum.

(1) The marked peculiarity in infection of Decapod Crustacea by certain parasites is the alteration of the sexual characters of the hosts (castration parasitaire of Giard). This has a twofold nature, viz.:—

(a) Sterility. In both sexes gonads dwindle and may entirely abort.

(b) Assumption of characters of other sex. In the male the external characters proper to the female are assumed in greater or less degree. The testis is transformed into a hermaphrodite gland, either while still infected by the parasite (incipient hermaphroditism of hermit crabs) or when freed from its influence (ripe ovotestis in spider crab). The reverse effects are not found in the female.

(2) This phenomenon occurs throughout the Invertebrata, but though sterility is a frequent consequence, the alteration of sex characters is never so definite as in the Crustacea. Analogous observations on parasitism in the Vertebrata have not been made.

(3) In the Insecta, parasitism appears to influence caste production. Grassi suggested that the sterility of soldiers and workers in Termites is due to protozoan parasites. In ants a giant caste is known (mermithergates) always harbouring a nematode worm.

Juvenile female Litomosoides sigmodontis secrete a protein (Juv-p120) highly modified with dimethylethanolamine (DMAE). In an attempt to establish the source of this decoration worms were pulsed with [3H]-choline and [3H]-ethanolamine and the radio-isotope labelled products analysed. Both isotope labels were successfully taken up by the worms, as demonstrated by labelling of phospholipids with [3H]-choline, being predominantly incorporated into phosphatidylcholine and [3H]-ethanolamine into phosphatidylethanolamine. Isotope labelling of phosphatidylethanolamine was particularly striking with the worms taking up ~30 times as much labelled ethanolamine as choline. It was possible to detect faint labelling of Juv-p120 with [3H]-ethanolamine after prolonged exposure periods but, unlike the situation with the phospholipids, it was much more readily labelled with [3H]-choline. When pulsing with [3H]-ethanolamine it was also possible to detect isotope-labelled phosphatidylcholine, which may ultimately account for the low levels of labelling of Juv-p120. Overall our results raise the previously unconsidered but intriguing possibility that in L. sigmodontis, choline may be the precursor of DMAE.

The material used for the following description consisted of three worms obtained from the intestine of the oystercatcher, Haematopus ostralegus occidentalis Neumann, shot near Aberystwyth. This is the first record of a protogynous tapeworm from Britain. In the whole of the Cestoda the protogynous condition is known only in four other genera, namely, Progynotaenia Fuhrmann (1909), with six species, and Proterogynotaenia Fuhrmann (1911), Leptotaenia Cohn (1901) and Gynandrotaenia Fuhrmann (1936, 1936a), each with a single species. The six known species of the genus Progynotaenia have been recorded from Egypt and the White Nile, Proterogynotaenia rouxi Fuhrmann from the Aru Islands off the coast of New Guinea, Leptotaenia ischnorhyncha (Lühe) from the Mediterranean and Gynandrotaenia stammeri Fuhrmann from Germany.

Copepods belonging to the genus Lamippe live in the gastrovascular cavity of several alcyonarian genera. Eighteen species of these copepods are known (Zulueta, 1911), nineteen if the variety L. rubra decolor Zulueta 1908 is raised to species rank as suggested by Heegaard (1949). Each species is highly preferential in its choice of a host. Only one species is known to parasitize more than a single species of coelenterate, namely L. rubicunda (Olsson, 1869) which lives in two species of Alcyonium.

This investigation was commenced by one of us (J. A. I.) in 1910 and carried on for three and a half years. Our purpose was to determine as accurately as possible the percentage of appendices operated on for appendicitis which contained intestinal parasites. The results of a study of 100 unselected cases are given below.

Exclusion of magnesium ions from resealed ghosts or their extraction from intact human red cells by means of an ionophore results in a reversible drop in susceptibility to invasion by Plasmodium falciparum merozoites in vitro. Resealed ghosts, containing magnesium-ATP and diluted cytosol, are invaded with high efficiency only when the original hypotonic lysis is carried Out in the presence of magnesium ions. This effect is not related to the loss of membrane-associated constituents when magnesium ions are absent. Ghosts containing calcium ions, together with the protective agent, flunarizine, were essentially resistant to invasion; this effect is again at least partially reversible. A possible explanation of these phenomena is that entry of the merozoite may be inhibited by breakdown of the host cell phospholipid asymmetry, with the appearance of aminophospholipids at the outer cell surface.

Haemozoin is a by-product of haemoglobin digestion by intraerythrocytic malaria parasites, which induces immunologic responses on different tissues, including endothelial cells. In the present paper, the incubation of human microvascular endothelial cells with haemozoin significantly inhibited MTT reduction, a measure of cytotoxicity, without increasing the release of cytoplasmic lactate dehydrogenase. Moreover, haemozoin did not induce apoptosis or cell cycle arrest nor decreased the number of live cells, suggesting that cells viability itself was not affected and that the inhibition of MTT reduction was only apparent and probably due to accelerated MTT-formazan exocytosis. After 30 min of MTT addition, a significant increase in the % of cells exocytosing MTT formazan crystals was observed in haemozoin-treated cells compared with control cells. Such an effect was partially reversed by the addition of genistein, an inhibitor of MTT-formazan exocytosis. The rapid release of CXCL-8, a preformed chemokine contained in Weibel–Palade bodies, confirmed that haemozoin induces a perturbation of the intracellular endothelial trafficking, including the exocytosis of MTT-formazan containing vesicles. The haem moiety of haemozoin is responsible for the observed effect. Moreover, this work underlines that MTT assay should not be used to measure cytotoxicity induced by haemozoin and other methods should be preferred.

This work introduces new morphological and molecular information on the filaroid nematode Setaria cervi (Rudolphi, 1819) obtained from 13 infected game ungulates out of 96 dissected. The hosts comprised the following: a single moose (Alces alces), ten red deer (Cervus elaphus) and two sika deer (Cervus nippon) originating from the western and northern regions of the Czech Republic. Based on the complete sequences of the gene encoding mitochondrial cytochrome c oxidase subunit 1 (cox1), all 20 females and four males belonged to the species S. cervi. We detected three developmental female stages (adult fertile females, juvenile L5 females and L4 female larvae) differing in size and some morphological traits as the subtle structure of peribuccal crown and shape and features of tail knob. Such differences were described in detail for the first time. The phylogenetic relationships within the family Onchocercidae have been evaluated using new information on the cox1 sequence of S. cervi (maximum likelihood method, GTR + I + G model). In accordance with the latest phylogenetic studies, the present analysis confirmed the ancient separation of the subclass Setariinae from the remaining two onchocercid lineages Dirofilariinae and Onchocerinae.