The period 1875–1925 was remarkable in the history of parasitology partly because of the number of significant discoveries made, especially the elucidation of important life cycles, and partly because of the achievements of the clinicians and scientists who made these discoveries. What is remarkable is that so many of these individuals were Scots. Preeminent in this pantheon was Patrick Manson, who not only discovered the mosquito transmission of filarial worms but was instrumental in directly encouraging others to make significant discoveries in the fields of malaria, Guinea worm disease (dracunculiasis), onchocerciasis, loiasis and schistosomiasis and, indirectly, sleeping sickness and leishmaniasis. This chapter describes and discusses the contributions made by Douglas Argyll-Robertson, Donald Blacklock, David Bruce, David Cunningham, Robert Leiper, William Leishman, George Low, Patrick Manson, Muriel Robertson and Ronald Ross together with short biographical notes.

The determination of Hyalomma sp. is discussed. In the material examined from Palestine the genital aperture of the female, the cuticle in the proximity of the stigmata and the number of ‘tunnels’ in the anterior border of the scutum are characters which facilitate diagnosis.

Based on the ability of bacterial associates of entomopathogenic nematodes to produce antibiotic compounds on artificial media, it has been commonly accepted that Xenorhabdus sp. and Photorhabdus sp. inhibit a wide range of invading microorganisms in insects infected with Steinernema spp. or Heterorhabditis spp. Therefore, the question of whether antibiotic compounds produced by the primary form of bacterial symbionts associated mutualistically with S. carpocapsae and H. bacteriophora explain why insect carcasses do not putrefy but provide nutritional requirements for insect parasitic rhabditoid nematodes to complete their life-cycle was examined. Laboratory bioassays of anti-bacterial activity on nutrient agar and during parasitism in larvae of Galleria mellonella have confirmed earlier observations that in vitro colonies of the primary form of X. nematophilus and P. luminescens produced agar-diffusible antibiotic compounds of a broad spectrum of anti-bacterial activity; their role in parasitism seems doubtful, however. This hypothesis is supported by a low antibiotic potency of a limited spectrum of anti-bacterial activity throughout the life-cycle of the parasites, principally in Galleria infected with S. carpocapsae. Since the lack of putrefaction cannot be explained simply by antibiotic inhibition of contaminating bacterial microflora, other competition mechanisms must be operating in parasitized insects. I postulated that a rapid and massive colonization of the insect body by nematophilic bacteria creates unfavourable conditions for the growth and multiplication of bacterial (proteolytic) contaminators making the insect carcass decay-resistant. In the case of H. bacteriophora, low antibiotic activity at an early stage of parasitism could support the colonization by P. luminescens of the host.

VmCT1 is an antimicrobial peptide (AMP) isolated from the venom of the scorpion Vaejovis mexicanus with antimicrobial, anticancer and antimalarial activities, which the rational design with Arg-substitution has yielded AMPs with higher antimicrobial activity than VmCT1. Chagas is a neglected tropical disease, becoming the development of new antichagasic agents is urgent. Thus, we aimed to evaluate the antichagasic effect of VmCT1 and three Arg-substituted analogues, as well their action mechanism. Peptides were tested against the epimastigote, trypomastigote, amastigote forms of Trypanossoma cruzi Y strain and against LLC-MK2 mammalian cells. The mechanism of action of these peptides was evaluated by means of flow cytometry and scanning electron microscopy. VmCT1 presented activity against all three forms of T. cruzi, with EC50 against trypomastigote forms of 1.37 μmol L−1 and selectivity index (SI) of 58. [Arg]3-VmCT1, [Arg]7-VmCT1 and [Arg]11-VmCT1 also showed trypanocidal effect, but [Arg]11-VmCT1 had the best effect, being able to decrease the EC50 against trypomastigote forms to 0.8 μmol L−1 and increase SI to 175. Necrosis was cell death pathway of VmCT1, as well [Arg]7-VmCT1 and [Arg]11-VmCT1, such as observed by membrane damage in flow cytometry analyses and scanning-electron-microscopy. In conclusion, [Arg]11-VmCT1 revealed promising as a candidate for new antichagasic therapeutics.

Methionine adenosyltransferase (MAT) is an important enzyme for metabolic processes, to the extent that its product, S-adenosylmethionine (AdoMet), plays a key role in trans-methylation, trans-sulphuration and polyamine synthesis. Previous studies have shown that a MAT-overexpressing strain of Leishmania donovani controls AdoMet production, keeping the intracellular AdoMet concentration at levels that are compatible with cell survival. This unexpected result, together with the fact that MAT activity and abundance changed with time in culture, suggests that different regulatory mechanisms acting beyond the post-transcriptional level are controlling this protein. In order to gain an insight into these mechanisms, several experiments were carried out to explain the MAT abundance during promastigote cell growth. Determination of MAT turnover in cycloheximide (CHX)-treated cultures resulted in a surprising 5-fold increase in MAT turnover compared to CHX-untreated cultures. This increase agrees with a stabilization of the MAT protein, whose integrity was maintained during culture. The presence of proteasome inhibitors, namely MG-132, MG-115, epoxomycin and lactacystin in the culture medium prevented MAT degradation in both MAT-overexpressing and ‘mock-transfected’ leishmanial strains. The role of the ubiquitin (Ub) pathway in MAT down-regulation was supported using immunoprecipitation experiments. Immunoprecipitated MAT cross-reacted with anti-Ub antibodies, which provides evidence of a proteasome-mediated down-regulation of the leishmanial MAT abundance.

The fluid layer within the cuticle of the nematode Nippostrongylus brasiliensis contains haemoglobin. The absorbance spectra of the haemoglobins extracted from whole nematodes were measured spectrophoto-metrically and the spectra of cuticular haemoglobin in individual living nematodes was obtained by microdensitometry. Adult female nematodes were confined under cover-slips in oxygenated saline and measurements of optical density of a small area of the cuticular haemoglobin were taken at 10 sec intervals. The optical density decreased over a period of 4 min at 543 nm and increased at 553 nm indicating deoxygenation of the cuticular haemoglobin; irrigation with fresh saline restored the haemoglobin to its oxygenated state. This demonstrates that cuticular haemoglobin loads and unloads oxygen in the living animal. Isoelectric focusing showed that mature nematodes have haemoglobins which are isoelectric around pH 7·0 and at pH 9·8. Isolated cuticular fluid contained the haemoglobin which was isoelectric at pH 9·8, but no other haemoglobin, and immature adults, which do not have cuticular haemoglobin, contained only those haemoglobins which were isoelectric at pH 7·0. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and column chromatography showed that the molecular weight of the cuticular haemoglobin sub-unit is 16·9–17·5 × 103 Daltons and that the haemoglobin exists primarily as a tetrameric molecule with a molecular weight of 65–75 × 103 Daltons. The presence of cuticular haemoglobin may allow adult Nippostrongylus to exploit oxygen-deficient areas within the environment of the rat's intestine where it would otherwise be unable to survive for prolonged periods.

This study was designed to test the accessory function of macrophages after activation with products of Taenia multiceps coenuri. Activation was carried out by intraperitoneal injection of mice with coenurus fluid or protoscolex culture supernatant, and function was assessed by adding these macrophages in progressively increasing numbers to macrophage-depleted lymphocyte cultures transforming under the influence of plant mitogens or coenurus-fluid mitogen. In contrast to normal macrophages, which have a progressively enhancing action on the above reactions, parasite-activated macro-phages at similar concentrations were progressively inhibitory. However, low concentrations of the activated macrophages enhanced mitosis as well as, or better than, normal. Lymph node cells from injected mice showed abnormal response to macrophage-derived signals. In particular there was subnormal reaction to macrophages in the presence of coenurus mitogen. These results suggest that T. multiceps coenuri may survive in the host because of their ability to reduce effective interaction between lymphocytes and accessory cells.

Trematode transmission in aquatic habitats from molluscan intermediate host to vertebrate or invertebrate target host is typically undertaken by a free-living stage known as cercariae. Active locomotion by cercariae is a key aspect of the transmission process with the swimming speed potentially contributing to infection success. Individual cercarial species swim at different speeds but the significance of this to infection potential has not been determined. This study, using data from the scientific literature, investigates the role of swimming speed in relation to cercarial morphology, host-searching strategies and target host species. Larger cercariae swim faster than smaller ones with tail length being the principal factor controlling locomotion rates. Different cercarial morphotypes swim at different speeds, in particular, furcocercariae, with the exception of the schistosomes, being faster swimmers than mono-tailed cercariae. Host-searching behaviour has a significant influence on swimming speeds with ‘active-searching’ strategies swimming slower than those adopting ‘active-waiting’ or ‘prey mimcry’ strategies. Vertebrate-infecting cercariae swim faster than those infecting invertebrates with species targeting fish demonstrating the highest locomotion rates and those targeting arthropods the slowest speeds. The adaptions of individual cercarial swimming speeds to biological variables and their interactions with the physical processes of aquatic habitats are discussed.

Real-time PCR was used to study the duration and level of parasitaemia in mice immunized with immune-stimulating complexes (iscoms) containing recombinant NcSRS2, one of the immunodominant surface antigens of Neospora caninum. After challenge infection, blood was collected daily for 9 days. During this period the amounts of parasite DNA detected in immunized mice were significantly lower (P<0·001), and the duration of parasitaemia appeared to be shorter, than in non-immunized controls. Furthermore, the degree of parasitaemia seemed to correlate well with the amount of N. caninum DNA in the brain 3 weeks post-inoculation and with disease severity measured as changes in body weight. These results indicate that the protective immunity induced by the NcSRS2-iscoms was sufficient to reduce the level of parasitaemia, which probably reduced the number of parasites reaching the brain, and could be the reason for the reduction in brain parasite load and clinical symptoms. Furthermore, real-time PCR was found to be a sensitive means for rapid assessment of N. caninum in blood.

The junction between the gregarine trophozoite Nematocystis magna Schmidt and an epithelial cell of its earthworm host Lumbricus terrestris Muller consists of an extensive folding and meshing of the single trilaminar membrane bounding the host cell and the complex folded multilaminar limiting membrane of the trophozoite. They are separated by a structureless intercellular region of some 50 nm in width. Specialized communicating regions or permeable elements were not observed. Transport of a radioactive label across non-junctional and junctional membranes was demonstrated by using tritiated glucose. The attachment organelle of the trophozoite is shown to be capable of allowing metabolites to pass into the cell directly from the host tissue.

The structure and development of microgametocytes of Eimeria maxima from chicks killed during the 6th day of infection were examined using transmission and scanning electron microscopy. Initially, nucleoli disappear and the surface of the microgametocyte invaginates. This is followed by a condensation of the chromatin which then lies at the periphery of the nuclei. Concurrent with this, the flagella are formed and they project into the parasitophorous vacuole and internal invaginations. Eventually, the nuclei become more dense and are seen to protrude from the periphery of the gametocyte. The surface view of mature microgametocytes consists of a large number of closely packed flagella.

Two 8-week experiments were conducted to determine the relationships between nutritional stress and pathophysiological changes in male Holstein calves infected with Sarcocystis cruzi. Calves were infected by oral inoculation with 200000 S. cruzi sporocysts. In the first experiment weight gain reduction was greatest in inoculated calves during weeks 4 and 5 after inoculation. Feed intake was reduced during the 5th week. Erythrocyte count was reduced during week 5 and haemoglobin was reduced during week 6. The 24-h excretion of urinary and urea nitrogen from the inoculated calves was increased by treatment. In the 2nd experiment, both the feed-restricted and inoculated calves lost weight during weeks 4 and 5; feed intake was lower from week 5 to 8 inclusive. Urine volume from inoculated calves was lower during week 8. Lower urine excretions of sodium and potassium resulted from S. cruzi inoculation. There was a non-significant trend for higher urinary zinc excretion in the inoculated group during week 4. Urine nitrogen excretion from inoculated calves was higher during weeks 4 and 6; nitrogen excretion from the feed-restricted group was higher during week 6. The urinary excretion of 3-methylhistidine from the inoculated calves was higher during week 4 and excretion of guanine was higher during weeks 4, 5 and 8. S. cruzi has several specific pathophysiological effects on calves beyond those induced by nutritional stress.

The level of immunity to a percutaneous cercarial challenge with Schistosoma mansoni was assayed 4–6 weeks after immunization of mice with highly irradiated (20 krad.) cercariae or schistosomula. When immunization and challenge occurred through the same skin site, resistance, particularly that which occurred in the skin, was greater than that observed when immunization and challenge occurred in different sites. The enhanced resistance is believed to be due to localized changes in the skin; 4 weeks after exposure to irradiated cercariae, abdominal skin is characterized by a thickened epidermis, changes in the ground substance and a cellular infiltration of the dermis. A convenient mouse model is described in which one or both ear pinnae are exposed to irradiated cercariae and a percutaneous challenge is given via the abdomen, thus eliminating the effects of local skin changes. In this model, the majority of the challenge infection which succumbs to the immune response appears to be killed in the skin.

A DNA polymerase activity has been detected and characterized in crude extracts from tachzoites of Toxoplasma gondii. The enzyme has a sedimentation coefficient of 6·4 S, corresponding to an approximate molecular weight of 150000 assuming a globular shape. Like mammalian DNA polymerase α, the DNA polymerase of T. gondii was sensitive to N-ethylmaleimide and inhibited by high ionic strength. However, the enzyme activity was not inhibited by aphidicolin which is an inhibitor of mammalian DNA polymerases α, δ and ε and also cytosine-β-D-arabinofuranoside-5′-triphosphate which is an inhibitor of α polymerase. The activity was inhibited by 2′,3′-dideoxythymidine-5′-triphosphate which is an inhibitor of mammalian DNA polymerase β and γ. Magnesium ions (Mg2+) were absolutely required for activity and its optimal concentration was 6 mM. The optimum potassium (K+) concentration was 50 mM and a higher concentration of K+ markedly inhibited the activity. Activity was optimal at pH 8. Monoclonal antibodies against human DNA polymerase did not bind to DNA polymerase of T. gondii. Thus the T. gondii enzyme differs from the human enzymes and may be a useful target for the design of toxoplasmacidal drugs.

A polymerase chain reaction (PCR) based on the detection of the Lmet2 repeat sequence specific to members of the Leishmania donovani–complex is described. To improve PCR specificity, a post-PCR hybridization step is often performed but this usually involves an entirely new procedure with additional manipulations, expense and time. We have simplified this post-PCR hybridization by developing a strategy which includes the probe in the PCR and enables the hybridization to be performed automatically as part of the PCR programme. The hybrids are afterwards detected by capture in microtitre wells and colorimetric visualization. This method, which we have termed PCR-solution hybridization enzyme-linked immunoassay (PCR–SHELA), is rapid, able to detect less than 5 cultured parasites and is specific for parasites of the Leishmania donovani–complex. We also describe the application of PCR–SHELA to the detection of amastigotes in various tissues of infected laboratory animals.

We have previously reported that the mechanisms of neuromyopathic damage induced by Trypanosoma cruzi are mediated by T cells and are parasite-strain dependent. In the present study our aim was to determine whether the humoral response against muscle and nervous system is also parasite-strain dependent. Of the sera from mice infected with RA and CA-I T. cruzi strains, 93% reacted against antigens of the nervous system (sciatic nerve, spinal cord and brain). No differences in the ability to recognize heart antigens were found between RA (48%) and CA-I (63%) antisera. Reactivity against skeletal muscle was only relevant in anti-CA-I sera at 270 days post-infection. Each of the antisera assayed in Western blots developed a particular antigenic pattern, but 3 antigens in the nervous system of molecular weight 48, 60 and 70 kDa were detected by 42, 28 and 23% of the sera, respectively. On the other hand, deposits of IgG were observed at the interstitial matrix in sciatic nerve and as endomisial and sarcolemmal patterns in skeletal muscle by IFAT for both RA and CA-I antisera. Absorption of sera with parasite antigens did not abolish the autoreactivity. Our results suggest that major serum autoreactivity from T. cruzi-infected mice is not parasite-strain dependent and does not arise from molecular mimicry.

Metacercarial cysts of Bucephalus haimeanus occur throughout the liver of Pomatoschistus microps, greater concentrations being found around the gall bladder, blood vessels and periphery of the liver. The cyst wall is composed of three layers, an inner granular, middle vacuolated and outer nucleated layer. The inner layer consists of three zones, an inner zone of irregularly compacted, granular material; a middle densely compacted zone and an outer moderately compacted zone. Vacuoles of the middle layer vary in appearance and appear to be discharging their contents into the cyst cavity. The cells of the outer layer are flattened and elongated with elongate nuclei but no other distinct organelles. Occasionally at the outer edge of the cyst are electron-dense cells which are in the process of degeneration. Only small amounts of collagen and very few leucocytes are associated with the cysts.

The cyst wall is carbohydrate in nature containing some free aldehyde groups, galactogen and neutral mucosubstances. The inner layer appears to consist of mainly acidic mucopolysubstances and weakly acidic sulphomucins. Large amounts of protein, carbohydrate-protein complexes and DNA are also present within the cyst wall. Alkaline and acid phosphatases, ATPase, β-glucuronidase and N-acetyl-β-glucosaminidase were detected. The origin and function of the cyst wall is discussed.

Some of the reindeer (Rangifer tarandus) introduced into Scotland from Northern Sweden have become infested with the deer warble fly Hypoderma diana and the deer ked Lipoptena cervi.

Evidence is presented which suggests that the larvae of H. diana proceed to their final site on the back of the host by way of the neural canal, and in this way probably caused the deaths of two reindeer in the winter of 1953–4.

A detailed analysis is presented of the frequency with which various bands of spines occurred on second-stage larvae of H. diana. An analysis of the number of chitinous rings in the two posterior spiracles on second-stage H. diana larvae showed that in any individual larva the two numbers were not independently determined.

On reindeer L. cervi produced puparia in December.