The present paper deals mainly with some new species of cestodes collected from birds commonly occurring in and near Nagpur, C.P., India.

In the Samoan Islands, in the South Pacific, one frequently sees horses and donkeys disfigured by large tumours. These occur on the pasterns and fetlocks, and occasionally between the eye and the nostril, but never on other parts of the body. They are often multiple, and they cause much inconvenience because of their size; many of them are larger than the animal's hoof (Plate XXIII).

I wish to thank the Society for inviting me to give the Introductory Talk in this Symposium. It is going to centre around what might be called ‘epitope specific’ immunization and I want to draw your attention to a number of factors which will be bound to affect any new approach to the development of vaccines. To begin with, it is now clear that complex antigens, such as those associated with parasites, present many different epitopes to the immune system. These epitopes are ‘seen’ by different cell types using different receptors and epitope recognition can activate a number of different effector systems.

A strain of Plasmodium gallinaceum has been treated for 10 weeks with sulphadiazine (5 mg./20 g.) in the presence of p-aminobenzoic acid in doses (0·5 mg./ 20 g.) inhibiting the sulphadiazine. No resistance to paludrine or to sulphadiazine has developed.

On 28. viii. 1932 seven specimens of Graffilla gemelipara Linton 1910 were found by Miriam Rothschild on the body inside the mantle cavity of a specimen of Cardium edule from Millbrook, Plymouth.

Though only taken previously in America and on a different host, Modiolus plicatulus, Linton's excellent figure leaves no doubt that these specimens belong to the same species.

Numerous specimens of a trematode which has proved to be a new species were collected from the kidneys of 'Ular sawa’ (Python reticulatus) at Alor Star and at Kedah, Malaya, by Mr G. B. Purvis, F.R.C.V.S. One batch comprises about 350 specimens, another one more than 150, and the entire collection of five batches exceeds 600 specimens. For this new species the name Styphlodora elegans is proposed. Mr Purvis also collected a single specimen of what seems to be a second new species from the stomach of the python at Alor Star, and for this the name Styphlodora compactum is proposed. Type specimens of the two new species are lodged in the British Museum (Natural History), London.

Cysticercus tenuicollis as metacestode of Taenia hydatigena is the most prevalent taeniid species in livestock. Eighty-eight C. tenuicollis samples were collected from sheep (n = 44) and goats (n = 44) of the northern Iran from 2015 to 2016. The isolated parasites were characterized by morphometric keys. The DNA of the larval stage was extracted, amplified and sequenced targeting mitochondrial 12S rRNA and Cox 1 markers. A significant difference in larval rostellar hook length was observed in 12S rRNA haplotypes. Analysis of molecular variance of 12S rRNA indicated a moderate genetic diversity in the C. tenuicollis isolates. The pairwise sequence distance of C. tenuicollis showed an intra-species diversity of 0.3–0.5% and identity of 99.5–100%. Using the 12S rRNA sequence data we found a moderate genetic difference (Fst; 0.05421) in C. tenucollis isolates collected from livestock of the northern and southeastern regions of Iran. We concluded that the genetic variants of C. tenuicollis are being undoubtedly distributing mostly in different parts of Iran. Further studies with a larger number of T. hydatigena isolates collected from various intermediate and definitive hosts are needed to study this evolutionary assumption and also to determine the apparent genetic differences observed in the studied regions.

Huff & Gambrell (1934), and Gambrell (1937) observed that, when Plasmodium cathemerium was passaged from canary to canary for a long period, by inoculation of blood from acutely infected birds, the number of gametocytes produced in each infection gradually decreased, though in two strains only did they disappear completely.

The course of a primary Necator americanus infection was studied in the lungs and small intestines of syngeneic mice. Following percutaneous infection no difference in initial larval establishment in the lungs was found between male BALB/c, NIH or B10.G mice. However, significant differences in the subsequent kinetics of infection were demonstrated between the BALB/c and NIH strains. Lung worm burdens declined more slowly in NIH mice than in BALB/c strain. Surprisingly, however, a greater proportion of larvae remaining in the lungs of BALB/c mice, 9 days p.i., were trapped than in NIH mice. Nevertheless, establishment in the small intestines of the BALB/c strain was consistently greater than in NIH mice. Host immunosuppression resulted in increased larval retention in the lungs of both the BALB/c and NIH strains as well as in the small intestines of BALB/c mice. Treatment with hydrocortisone acetate did not increase intestinal worm burdens in NIH mice. The data presented suggest that, in this complex, dynamic model system, designation of ‘susceptible’ and ‘resistant’ strains is inappropriate. The factors underlying the observed strain differences in resistance to infection are discussed.

Infection in mice (BALB/cABom) with the intestinal trematode Echinostoma caproni had a negative influence on pregnancy. The effect of the infection set in immediately following implantation (day 5 of pregnancy) resulting in fewer foetuses being present in infected mice on day 9 than in the controls. Ovulation, fertilization of eggs, and implantation itself were obviously not impaired. The infected mice had significantly lower serum progesterone levels on day 5 of pregnancy than the non-infected controls. It is speculated that the progesterone levels in the infected female mice were too low to secure early post-implantation gestation.

Trichinella spiralis is the nematode causative agent of trichinellosis, an intestinal and tissular parasitosis. Even though an early diagnosis during the intestinal phase is essential to limit the infection in humans, to date, there are no available tests to achieve this goal. Based on the immune response generated by the host's intestinal mucosa, the aim of this work was to develop ELISAs to assess the presence of coproantigens (CAgs), coproantibodies (CAbs) and faecal immune complexes in stool samples of 18 individuals belonging to different outbreaks that have arisen in Argentina. By the methodologies developed in this work it was found that anti-muscle larva excretory-secretory products (ML-ESP) CAbs were detected in 89% of the samples analysed regardless of the time p.i. Anti-ML-ESP IgA, IgG, IgE and IgM were detected in 56%, 56%, 28% and 22% of the individuals respectively. Those samples negative for anti-ML-ESP total immunoglobulins proved positive for anti-adult worm-ESP CAbs. No CAgs were detected in any of the samples. The results obtained in this work indicate that the intestinal immune response in human trichinellosis is featured by all the isotypes of specific immunoglobulins. Furthermore, the detection of antibodies in stool samples, in either the free or complexed form, could be applied to confirm early human trichinellosis.

A morphological and histochemical study has been made of atresia in oocytes in the ovarian balls of an acanthocephalan (Centrorhynchus corvi). Growing oocytes and mature oocytes have been observed to undergo atresia. With the start of atresia, the nuclear and cytoplasmic components are observed to be greatly altered. The atretic oocytes develop abnormal aggregations of cell components, which contain proteins, phospholipids and lipoproteins. It is suggested that the cellular products of degenerating oocytes are gradually absorbed by the supporting syncytium. The atresia of growing oocytes is greater in uninseminated than in inseminated females, which indicates that in the absence of a mating stimulus atresia occurs more frequently.

The acephaline gregarine, Gonospora varia Léger, from the coelomic cavity of the Polychaete worm Audouinia (Cirratulus) tentaculatus (Montagu) exhibits an interesting phenomenon, in which the life-history of the parasite is closely bound up with the sexual cycle of the host. It is characteristic of the acephaline gregarines that they are, for the most part, inhabitants of the coelom, and, as a consequence, frequently live in very close association with, if not actually parasitic on, the reproductive cells themselves. The familiar Monocystis from the seminal vesicles of the earthworm is an example which is at once called to mind. So, in the case of gregarines such as Gonospora, it is a common feature for them to spend the greater part of their existence free in the body cavity among the host's genital products. Naturally, they are reliant on the host's method of expulsion of the ova or spermatozoa for the dispersal of their spores. We therefore find that the periodic annual spawning of the worm is accompanied by a corresponding periodicity in the life-history of the parasites, which probably results in the reproductive bodies of both parasites and host being expelled together. In this point there seems to be a somewhat greater degree of specialisation than in Monocystis, where it is generally accepted that the spores are shed only on the death of the earthworm, either naturally or as the prey of some bird.

The role of Mycobacterium w (Mw) vaccine as an immunomodulator and immunoprophylactant in the treatment of mycobacterial diseases (leprosy and pulmonary tuberculosis) is well established. The fact that it shares common antigens with leishmanial parasites prompted its assessment as an immunostimulant and as an adjunct to known anti-leishmanials that may help in stimulating the suppressed immune status of Leishmania donovani-infected individuals. The efficacy of Mw vaccine was assessed as an immunomodulator, prophylactically either alone or in combination with anti-leishmanial vaccine, as well as therapeutically as an adjunct to anti-leishmanial treatment in L. donovani-infected hamsters, representing a chronic human Visceral Leishmaniasis (VL) model. Similarly, its efficacy was also evaluated in L. donovani-infected BALB/c mice, representing an acute VL model. The preliminary studies revealed that Mw was ineffective as an immunostimulant and/or immunoprophylactant in hamsters infected with L. donovani, as estimated by T-cell immunological responses. However, in the BALB/c mice-VL model it appeared as an effective immunostimulant but a futile prophylactic agent. It is therefore inferred that, contrary to its role in managing tuberculosis and leprosy infections, Mw vaccine has not been successful in controlling VL infection, emphasizing the need to find detailed explanations for the failure of this vaccine against the disease.

The route of migration of Cercaria X within the host snail, Lymnaea stagnalis, has been demonstrated by means of serial sections and a method of numerical assessment of the distribution of cercariae in the various tissues and organs of the body.

The main pathway along which migrating cercariae travel is the blood system, which differs from the route in the fish second intermediate host. The cercariae enter the main visceral haemocoel by rupture of the wall of the digestive gland and from there enter the main venous vessels deploying through the rectal sinus, sub-renal sinus, lung and heart. The cercariae travel from the heart via the mantle arteries to localize in the mantle sinuses prior to emergence.

The inner surface of the mantle, and in particular its leading edge, is the main site of emergence, and escape of cercariae is, in the final stages at least, an active process. It is suggested that passage of parasites in the blood stream is partly active.

Migration and subsequent emergence is probably facilitated by the activity of the oral cap of spines, the general activity of the cercaria and the activity of the oral and ventral suckers.

A tissue response to the presence of cercariae in the blood vessels and tissues of the mantle is evident, the cells responsible for this being, possibly, actively phagocytizing amoebocytes of the mollusc's blood. The swellings in the epidermis of the mantle in heavy infections may be the result of an accumulation of these cells.

Grateful acknowledgement is expressed to Professor J. Brough for the facilities and encouragement provided during the course of this study. This work was carried out during the tenure by A. J. Probert of a D.S.I.R. Research studentship.

The pathogens Plasmodium juxtanucleare and chicken anaemia virus (CAV) are easily transmitted and potentially harmful to chickens. In this study, we established an experimental model to investigate the effects of avian malaria caused by P. juxtanucleare in white leghorn specific-pathogen-free (SPF) chicks previously immunosuppressed with CAV. Parasitaemia, haematological variables and clinical and pathological parameters were determined in four different experimental groups: chicks coinfected by CAV and P. juxtanucleare strain (Coinfected group), chicks exclusively infected by CAV (CAV group) or P. juxtanucleare (Malaria group) and uninfected chicks (Control group). Our data demonstrated that P. juxtanucleare parasitaemia was significantly higher in the Coinfected group. Furthermore, haematological parameters, including the RBC, haematocrit and haemoglobin concentration were significantly reduced in coinfected chicks. In agreement with the changes observed in haematological features, the mortality among coinfected chicks was higher compared with animals with single infections. Clinical analysis indicated moderate changes related to different organs size (bursa of Fabricius, heart and liver) in coinfected birds. The experimental coinfection of SPF chickens with P. juxtanucleare and CAV may represent a research tool for the study of avian malaria after CAV immunosuppression, enabling measurement of the impacts caused by different pathogens during malarial infection.

Vector systematics research is being transformed by the recent development of theoretical, experimental and analytical methods, as well as conceptual insights into speciation and reconstruction of evolutionary history. We review this progress using examples from the mosquito genus Anopheles. The conclusion is that recent progress, particularly in the development of better tools for understanding evolutionary history, makes systematics much more informative for vector control purposes, and has increasing potential to inform and improve targeted vector control programmes.

To determine the involvement of the actin cytoskeleton in macrogametocyte growth and oocyst wall formation, freshly purified macrogametocytes and oocysts were stained with Oregon Green 514 conjugated phalloidin to visualize F-actin microfilaments, while Evans blue staining was used to detect type 1 wall forming bodies (WFB1s) and the outer oocyst wall. The double-labelled parasites were then analysed at various stages of sexual development using three-dimensional confocal microscopy. The results showed F-actin filaments were distributed throughout the entire cytoplasm of mature Eimeria maxima macrogametocytes forming a web-like meshwork of actin filaments linking the type 1 WFBs together into structures resembling ‘beads on a string’. At the early stages of oocyst wall formation, F-actin localization changed in alignment with the egg-shaped morphology of the forming oocysts with F-actin microfilaments making direct contact with the WFB1s. In tissue oocysts, the labelled actin cytoskeleton was situated underneath the forming outer layer of the oocyst wall. Treatment of macrogametocytes in vitro with the actin depolymerizing agents, Cytochalasin D and Latrunculin, led to a reduction in the numbers of mature WFB1s in the cytoplasm of the developing macrogametocytes, indicating that the actin plays an important role in WFB1 transport and oocyst wall formation in E. maxima.

Parasite infection in young animals can affect host traits related to demographic processes such as survival and reproduction, and is therefore crucial to population viability. However, variation in infection among juvenile hosts is poorly understood. Experimental studies have indicated that effects of parasitism can vary with host sex, hatching order and hatch date, yet it remains unclear whether this is linked to differences in parasite burdens. We quantified gastrointestinal nematode burdens of wild juvenile European shags (Phalacrocorax aristotelis) using two in situ measures (endoscopy of live birds and necropsy of birds that died naturally) and one non-invasive proxy measure (fecal egg counts (FECs)). In situ methods revealed that almost all chicks were infected (98%), that infections established at an early age and that older chicks hosted more worms, but FECs underestimated prevalence. We found no strong evidence that burdens differed with host sex, rank or hatch date. Heavier chicks had higher burdens, demonstrating that the relationship between burdens and their costs is not straightforward. In situ measures of infection are therefore a valuable tool in building our understanding of the role that parasites play in the dynamics of structured natural populations.