Cytokine responses to Leishmania infection begin very early in infection, and differ between susceptible and resistant mice. Susceptibility to chronic Leishmania infection has been associated with increased haematopoiesis. To analyse the effect that acute infection with L. major has on bone-marrow haematopoiesis in susceptible (BALB/c) and resistant (CBA) mice, we enumerated erythroid progenitors and granulocyte-monocyte progenitors 3 days after infection. We found that haematopoiesis was stimulated in BALB/c mice infected with L. major, while haematopoiesis was inhibited in CBA mice. We found that this effect could be partially explained by cytokine production: interleukin-4 was involved in stimulation of BALB/c haematopoiesis and tumour necrosis factor-α was involved in inhibition of CBA haematopoiesis. Our conclusions are that haematopoietic changes occur shortly after L. major infection, and may be related to disease outcome.

The host contact network structure results from the movement and behaviour of hosts (e.g. degree of sociability; vagility and greater or lesser fidelity of shelters), which can generate heterogeneity in the transmission of parasites and influence the parasitic burden of individual hosts. In the current study, we tested the hypothesis that the burdens of Gigantolaelaps oudemansi mites are related to the characteristics of the transmission networks of individuals of Oecomys paricola, a solitary rodent. The study was carried out in a savannah habitat in north-eastern Brazil. In the dry season, the rodent network presented sub-groups of rodent individuals interacting with each other, whereas in the wet season, no modules were formed in the network. Mite burden was positively related to the number of connections that an individual host had with other host individuals in the dry season. The pairwise absolute difference between the mean mite burdens among individual rodents was negatively correlated with the similarities of node interactions. No relationships were observed during the wet season. There was a higher heterogeneity of mite burden among hosts in the dry season compare to that in the wet season. In solitary species, spatial organization may show seasonal variation, causing a change in the opportunities of host contacts, thereby influencing the transmission and dispersion of their ectoparasite burdens.

Medicinal plants have been the focus of several studies due to their nematicide properties which can be used to control nematodes in sheep. No study has examined the morphological effects of Cymbopogon citratus on nematodes. Thus, this study evaluated the chemical composition, nematicidal activity and effects of C. citratus extracts on the morphology of eggs and infective larvae (L3) of sheep. Aqueous and methanolic extracts and fractions of C. citratus were obtained and analysed in vitro. The C. citratus extracts were effective against Haemonchus spp. and Trichostrongylus spp. larvae and eggs. Ten fractions were obtained from C. citratus, six of which had high ovicidal activity at 1000 μg mL−1, and two fractions had high activity at all tested concentrations. The phytochemical analysis identified the presence of compounds such as terpenoids, various ketones, esters, and fatty acids. The ultrastructural analysis showed deformations of the cuticle and wilting along the body of the nematodes at all concentrations. The muscular layer, intestinal cells and the mitochondria profile showed damage compared to the typical pattern. Ultra-thin sections of eggs treated with methanolic fractions of C. citratus presented modifications. This study showed the biological activity and effects of C. citratus on the gastrointestinal nematodes in sheep.

1. In accordance with the views held by Chatton and Alilaire (1908) and by Roubaud (1909), I have seen that a true trypanosome-stage occurs in the life-history of Crithidia calliphorae. These try-panosomes have an undulating membrane and cannot be considered as herpetomonads with their blepharoplasts situated behind the nucleus and a completely internal flagellum (Woodcock), nor are they herpetomonads with the flagellum bent back along the body of the cell (Mackinnon). This existence of a trypanosome stage in the life-history of Crithidia is quite comprehensible if we consider that in many cases true Trypanosomata are changed into Crithidiae when they pass from the blood into the gut of an invertebrate host (T. gambiense, T. lewisi, Schizotrypanum cruzi, etc.).

2. There is no sharp difference between the genera Crithidia and Herpetomonas. In Crithidia calliphorae forms may be observed without any trace of an undulating membrane (Diagram I, Fig. 1); in Herpetomonas calliphorae such an organellum may be sometimes present (Diagram IX, Fig. 4).

Still I think that it is not permissible to throw these two genera together, as, generally speaking, an undulating membrane is present in Crithidia and absent in Herpetomonas.

3. Herpetomonas is often biflagellate, even when no signs of cellular division are present and the flagellates multiply less actively than in monoflagellate stocks. Still I agree with Patton that this biflagellate condition is too inconstant to permit of its being recognized as of generic significance.

4. The structure of the blepharoplast of Herpetomonas is distinctly like that of a nucleus, with peripheral chromatin and one or more central granules. It is true that the behaviour of these granules during the division is not so regular as that of the karyosomes of real nuclei, nevertheless, I think that the aspect of the blepharoplast of H. calliphorae is a strong argument in favour of Schaudinn's, and also Minchin's, view that this organellum must be regarded as a specialized nucleus (kinetonucleus).

5. The flagellum of Crithidia calliphorae is constructed in the same way as that of Trypanosoma lewisi: a basal granule is present and the new flagellum is formed by the production of a new flagellar root by fission of the basal part of the old flagellum. In Herpetomonas calliphorae a basal granule (at the base of the flagellum) and a marginal granule (at the point where the flagellum reaches the surface of the cell and becomes free) are present. The part of the flagellum situated between these two granules is the rhizoplast. The marginal granule first divides; then follows the fission of the rhizoplast and basal granule; lastly, from the marginal granule a new flagellum grows out, so closely entangled with the old one that it often seems as if the production of the new flagellum occurs exclusively by fission.

6. The extranuclear chromatoid granules of H. calliphorae consist of volutin. They are numerous during the preflagellate stage and disappear gradually during the flagellate stage; in the post-flagellate stage they are few in number or altogether absent.

This behaviour suggests that volutin in H. calliphorae may act as a sort of nutritive reserve-substance. In degenerating individuals the volutin granules become extremely numerous, an abnormal condition observed also in Trypanosomata (“ volutinosis ”). Consequently volutin seems to play the double part of a nutritive substance, and product of degeneration; this, however, likewise holds for many other nutritive substances (fat, glycogen, etc.).

7. The blepharoplast of H.'calliphorae shows cyclical changes. During the formation of the post-flagellate stages the achromatic substance is lost and only the chromatic portion remains. The blepharoplast is smallest at this period. The preflagellate stages possess a larger blepharoplast, and this organellum reaches its maximum dimensions during the flagellate stage. I am not able to say whether or not these cyclical changes have any special importance; perhaps they have something to do with the regulation of the normal relation between nucleus and protoplasm.

8. H. calliphorae was observed by me only in the gut of the fly and does not seem to be transmitted hereditarily, as is the case in Crithidia melophagia (Swingle, 1909; Porter, 1910).

Observations have been made on the survival of unfed rat-fleas, both newly hatched and wild-caught, under controlled conditions of temperature and relative humidity, and further observations on oviposition, hatching of eggs and emergence of adults under the same conditions.

The results show that, of the three sets of conditions employed, a temperature of approximately 20° C. and relative humidity of about 100 per cent. are the most favourable for survival of adults, hatching of eggs and production of a further generation of adults. The two other sets of conditions (temperatures of 15 and 30° C., with relative humidities of 60 and 100 per cent. respectively) are entirely unsuitable for the breeding of the species of fleas used.

At 20° C. and relative humidity 100 per cent. the whole pre-adult life of Xenopsylla brasiliensis and X. cheopis is, on the average, approximately 8–9 weeks, the minimum being 6 weeks. The female in both species is shown to have a distinctly shorter larval and pupal life than the male.

The lymph system of Zygocotyle lunatum consists of a pair of longitudinal vessels dorsal and slightly medial to the intestinal caeca with branches to various body organs. On the basis of the lymph system and host relationships of the type genus Zygocotyle, the diagnosis of the sub-family Zygocotylinae as modified by Bhalerao to contain Stunkardia dilymphosa must be revised.

A comparison of feeding and breeding performance was made between a laboratory strain (LS) and two freshly collected field strains (FS1, FS2) of Rhipicephalus appendiculatus. The LS had been cultured for over 30 years on tick-susceptible rabbits. When fed on susceptible rabbits LS produced smaller eggs and unfed larvae, nymphs and adults than those of FS. Eggs and larvae from females engorged on cattle were larger than those from females engorged on rabbits. LS and FS females engorged on susceptible hosts were of similar weight, but the FS females were twice as heavy as LS females when tick-resistant hosts were used. A higher proportion of LS ticks than of FS ticks engorged on susceptible hosts, but a lower proportion on resistant hosts. Thus on susceptible hosts LS showed a higher reproduction efficiency than FS, but a lower one than FS on resistant hosts. The proportional reductions of engorged weights and numbers feeding successfully on resistant hosts were significantly lower for LS than FS ticks. Cross-resistance was low between LS and FS. Although all strains were affected by host resistance, it was concluded that the field strains were better adapted to withstand resistance than the laboratory strain.

Nine out of thirty-three specimens of the common shrew Sorex araneus, caught at Rosta in north Norway in August 1953, were found to be infected with Grahamella (Rickettsiales). Nine specimens of Clethrionomys rutilus, nine of Microtus oeconomus ratticeps and one of M. agrestis, caught at the same time and place, were found to be free of Grahamella. No other blood parasites were found in any of the animals examined.

Records by other authors of Grahamella in a variety of hosts are reviewed. The parasite is known to occur in mammalian hosts only: identifications of it in non-mammalian hosts can be discarded. Host specificity, tacitly assumed by most authors, is not proven, and therefore most of the specific names bestowed on Grahamella in different hosts are of doubtful validity. The morphology of the parasite varies little from host to host; and there is little evidence to show that its pathogenic effect on any host is serious. Grahamella has been cultured by a few authors: variations in characters of these cultures may be more reliable criteria for recognition of different species of Grahamella.

These small mammals were collected while I was a member of the University of Edinburgh Expedition to Arctic Norway, 1953. I wish to thank all who were concerned, in particular Dr D. M. Steven, with whom I did the trapping. The rest of the work was done during the tenure of a Research Studentship awarded by the Agricultural Research Council. I also wish to thank Dr P. Tate for his advice and his criticisms of the manuscript.

A score of these large amphistomes were found in the collection made by Dr P. L. LeRoux, to whom we wish to express our gratitude for the privilege of examining them, and to Professor J. J. C. Buckley for his interest in the work. The characteristically large posterior sucker and its muscular structure places this amphistome in Nasmark's Gigantocotyle.

The following descriptions relate to a new species of Ixodes, to a new variety of Ixodes loricatus, to new species of Amblyomma and Rhipicephalus

Since writing our recent review (Markham, Smith & Lea, 1942) on the sizes of viruses and the methods employed in their estimation, another virus has been added to the list of those concerning which we have concordant information by so many different methods that conclusions as to the size and shape and degree of hydration can be drawn with some confidence. This is the Shope rabbit papilloma virus, electron micrographs of which have been published by Sharp, Taylor, Beard & Beard (1942), and for which data on diffusion, sedimentation, density and viscosity have been published by Neurath, Cooper, Sharp, Taylor, Beard & Beard (1941). These data may be worked up by the formulae given in our review, and this note will serve to illustrate the convenience of our formulae for such purposes.

1. The larva and nymph of Rhipicephalus pulchellus are described for the first time and comments are made on the degree of variation in structure seen amongst adults of a single generation.

2. Information on various aspects of the biology of this tick and on classification is given.

The choniostomatids parasitic on Crustacea have been exhaustively studied by Hansen. To the six genera and forty-three species he had described in 1897, he added a new genus and three more species in 1904, and seven more species in 1923. Scott (1904, 1905, 1907) described seven more species, Fraenkel (1915) three new species, Monod (1930) one, and Blake (1929) two. In 1929, however, Connolly described a new genus Choniosphaera and its type species C. cancrorum, from parasites found on American crabs Cancer amoenas, C. irroratus and C. borealis. In the present paper a new species Choniosphaera indica, parasitic on the edible crab Neptunus sanguinolentus of Madras, is described.

In this paper the history is given of the maintenance away from man of certain strains of T. rhodesiense originally isolated from man in Tanganyika Territory.

In a memoir recently published, Salvin-Moore and Breinl state that when Trypanosoma gambiense is examined in the blood “it does not seem possible to detect any true dimorphism or trimorphism.” “The three forms often described and alluded to as distinct, consequently appear to be arbitrarily chosen examples in a continuous series of dimensions.” It has always seemed to me very remarkable that the great differences in form and structure, no less than in size, between the slender, ordinary, and stumpy forms of T. gambiense, differences noted by all competent observers, should have been denied by two authors who claim for their methods of technique a superiority over those employed by all other investigators.

Our observations on a large number of recently dead or dying grouse impels us to believe that in many cases death is primarily caused by the presence of parasitic worms, either Cestodes or Nematodes in various parts of the alimentary canal.

Laboratory rodents vaccinated with highly irradiated cercariae of Schistosoma mansoni develop significant levels of specific acquired resistance yet effect challenge elimination in different organs. Mice and guinea-pigs are at opposite ends of the spectrum in this respect since, in our hands, vaccinated mice kill challenge parasites in the skin whereas vaccinated guinea-pigs kill challenge parasites predominantly in the liver. To determine whether this phenomenon is host-dependent (site) or parasite-dependent (stage), we have transferred worms harvested from mice or guinea-pigs into vaccinated recipient guinea-pigs. The results show that mouse-derived 5-day lung worms and 9-day liver worms that are essentially refractory to vaccine resistance in mice are indeed susceptible to vaccine resistance in guinea-pigs. Identical levels of susceptibility were recorded for lung-stage larvae introduced via the foot vein so as to experience lung and liver mechanisms, or via the mesenteric vein to bypass the lung, thereby confirming that vaccine resistance in guinea-pigs operates in the liver. Mouse worms and guinea-pig worms exhibited equivalent levels of susceptibility at all stages of development. Thirteen-day-old larvae from either donor species were on the border-line of vulnerability, while 20-day-old worms were totally refractory to vaccine immunity in guinea-pigs. These data show that vaccine immunity in different rodent species is a site-dependent, rather than a stage-dependent phenomenon. There is, however, an upper age limit of schistosome vulnerability which is common to worms harvested from different donor species.

After treatment with arsenophenylglycin the number of trypanosomes in an infected animal immediately begins to decrease, and the parasites disappear from the peripheral circulation 6—7 hours after the time of injection, the short stumpy forms being the last to degenerate.

One of the first changes noticed in the trypanosomes after treatment is the rounding up of their posterior extremities caused by the retraction of the protoplasm behind the kineto-nucleus. Meanwhile the tropho-nucleus becomes filled with granules of volutinose, which are extruded into the cytoplasm and pass along the axial filament towards the anterior extremity of the body. In dividing forms the granules form two longitudinal rows, being distributed along the two axial filaments. Finally, the granules lose their regular arrangement and become scattered throughout the cytoplasm, being more abundant, however, at the anterior end.

The kineto-vacuole, when present, enlarges considerably and may become filled with chromatic substance derived from the kineto-nucleus.

The axial filament begins to degenerate soon after treatment, often breaking up into a row of granules. Occasionally, however, chromatic substance from the kineto-nucleus passes along the axial filament, and it then appears as a thick black band extending along the middle of the cell eventually to the anterior extremity. Subsequently it breaks up into granules which dissolve in the cytoplasm of the cell.

Chromatic bodies are given off from the kineto-nucleus both before and after treatment and do not seem to be a characteristic feature of degeneration.

Sometimes the tropho-nucleus completely disappears before the cytoplasm breaks up into fragments, but at other times it preserves its form long after all other parts of the trypanosome, with the exception of the flagellum, have disappeared. These free nuclei resemble the “latent bodies” described by Salvin-Moore and Breinl, but as they, along with the fragments of cytoplasm, granules etc., are ingested by the leucocytes, it seems possible that they are merely one of the results of degeneration and not part of the life-cycle of this parasite.

These investigations have been carried on partly with the aid of a grant from the Tropical Diseases Research Fund (Colonial Office).

1. The development of exo-erythrocytic parasites of Plasmodium gallinaceum is more rapid and intense in chicks inoculated with blood from birds heavily infected with exo-erythrocytic parasites than in those inoculated with blood from birds in which no exo-erythrocytic parasites can be found.

2. If parasitized blood from a bird heavily infected with exo-erythrocytic parasites is inoculated intravenously into a normal bird and withdrawn 24 hr. later, it produces infections in normal birds characterized by a slow development of exo-erythrocytic parasites.

3. The proportion of birds which survived after inoculation with P. gallinaceum and daily treatment with suppressive doses of quinine, mepacrine or pamaquin, was greater when the inoculum was derived from donors in which no exo-erythrocytic parasites could be found (48%) than in those inoculated with blood from donors in which exo-erythrocytic parasites 'were numerous (15). No birds inoculated with parasitized blood from donors heavily infected with exo-erythrocytic parasites were sterilized of their infections by the action of the drugs, whereas in eleven out of sixty-six of the birds inoculated with parasitized blood from birds in which no exo-erythrocytic parasites could be found the infections were eradicated by the drugs.

4. Blood-inoculated infections of P. gallinaceum may in some cases be eradicated by short courses of treatment with mepacrine, quinine or pamaquin.

5. Whereas blood-inoculated infections of P. gallinaceum derived from donors in which no exo-erythrocytic parasites could be found were sometimes eradicated by prophylactic treatment with quinine, mepacrine or pamaquin, it was not possible to eradicate the infections by curative treatment with similar doses of these drugs.

6. The difference in type of infection produced by parasitized blood from birds in which no exo-erythrocytic parasites could be found at the time of withdrawal of the blood and those in which exo-erythrocytic parasites were plentiful appears to be due to the presence of exo-erythrocytic parasites in the circulating blood of the latter type of donor.

7. Sterilization by the action of quinine, mepa-crine or pamaquin of blood-inoculated infections from donors in which no exo-erythrocytic forms could be found, appears to depend upon whether the erythrocytic parasites are killed before they can become converted into exo-erythrocytic forms.

8. No evidence has been obtained of the intensification of development of exo-erythrocytic parasites by the suppression of erythrocytic parasites with drugs.