The effect of temperature on the behaviour of the infective larvae of Trichostrongylus colubriformis has been investigated. Larvae acclimatized at 3°C or 20°C respond to sudden or gradual increases in temperature by coiling. Increased temperature may indicate a risk of exposure to desiccation and elicits a behavioural response which optimizes survival. Larvae are straight when inactive; coiling is an active response to specific stimuli. Larval activity is initiated by exogenous stimuli. Mechanical disturbance is a major stimulus, the response being affected by changes in temperature. Larvae acclimatized at 3°C or 20°C show a peak of activity at temperatures between 15 and 25°C.

A total of 65 enzymes in the 8 European pathotypes of the potato cyst nematodes Globodera pallida and G. rostochiensis were examined by isoelectric focusing (IEF) for possible polymorphic variants which may aid rapid pathotype recognition. Quantitative variation was seen with glucose oxidase (EC 1.1.3.4), with high levels of this enzyme present in G. rostochiensis Ro3. Mannose phosphate isomerase (EC 5.3.1.8) also varied between the pathotypes with G. rostochiensis Ro4 and Ro5 differing from the other pathotypes in the relative absorbance of some bands. Phosphoglucomutase was examined on a narrow-range pH gel and additional differences to those described previously were detected.

Mice pre-treated with Corynebacterium parvum and later challenged with Plasmodium vinckei become infected but do not die whereas control mice do. When pre-treated mice were challenged with 1, 10, 1 × 102, 1 × 104, 1 × 105 or 1 × 106 parasites, the pre-patent periods correlated directly with the number of parasites injected, but the subsequent parasitaemias reached similar levels. This suggests that parasite killing, resulting from pre-treatment with C. parvum, is not triggered until the parasite load has reached a particular threshold. The injection of alloxan monohydrate, which brings about the release of toxic oxygen inter mediates thought to be involved in non-specific immunity, has little effect on P. vinckei infections until the parasitaemia is relatively high. This indicates that oxygen-mediated parasite killing also does not occur until the parasitaemia has reached a particular threshold. It is suggested that it is only at relatively high parasitaemias that the factors involved in parasite killing are able to enter the infected red blood cells.

A Previous paper (Bishop, 1932) dealt with the cultivation of a Hexamita sp. found in the horse-leech (Haemopis sanguisugae = Aulastomum gulo). The present paper deals with the morphology and method of division of the Hexamita above referred to, which I now name H. gigas n.sp. Dobell (1909) gave a detailed history of the nomenclature of the genus, and Wenyon (1926) has dealt with the same subject and given a list of the then known species and their hosts. Two species have since been described: H. pulcher, by Becker (1926), from the caecum of the ground squirrel Citellus tridecemlineatus, and Octomitus (= Hexamita) pitheci described and figured by da Cunha and Muniz (1928) from the intestine of Macacus rhesus. Apart from the two species (Hexamita nodulosa and H. inflate) described by Dujardin (1841) from stagnant water, and in which he saw but six flagella, a single species only has been described hitherto from a non-vertebrate host. This species, Octomitus (= Hexamita) periplanetae, a small flagellate 5–8 μ in length, from the gut of the cockroach, was described by Bělař (1916); a similar flagellate from the gut of Blatta orientalis has been found by me.

Trypanosomatid parasites possess 2 distinct iron-containing superoxide dismutases (Fe-SODs) designated SODA and SODC, both of which are targeted to their mitochondria. In contrast to SODAs that carry typical mitochondrial transit peptides, SODCs have highly unusual mitochondrial targeting signals. Our analyses clearly show that these pre-sequences are bipartite possessing a signal peptide-like domain followed by a transit peptide-like domain. Consequently, they resemble N-terminal extensions of proteins targeted to multi-membrane plastids, suggesting that trypanosomatids once contained a eukaryotic alga-derived plastid. Further support for this hypothesis comes from striking similarities in length, hydropathy profile, and amino acid composition of SODC pre-sequences to those of Euglena and dinoflagellate plastid proteins. To account for these data, we propose that the Trypanosomatidae initially possessed a gene encoding a mitochondrial Fe-SOD with a classical mitochondrial transit peptide. Before or after plastid acquisition, a gene duplication event gave rise to SODA and SODC. In a subsequent evolutionary step a signal peptide was linked to SODC, enabling its import into the plastid. When the trypanosomatid plastid subsequently was lost, natural selection favoured adaptation of the SODC N-terminal signal as a mitochondrial transit peptide and re-targeting to the mitochondrion.

The genus Onchocotyle was named by Diesing in 1850 with O. appendiculatum (Kuhn 1829) as type. Cerfontaine (1900) reviewed the history of the group and revised the genus. He named the subfamily Onchocotylinae, containing three genera: Squalonchocotyle, Acanthonchocotyle (subsequently regarded by Monticelli (1903) as a synonym of Onchocotyle) and Rajonchocotyle. He discarded the older generic name of Onchocotyle, and placed the group in the group in the family Octocotylidae. Poche (1925) placed it in the family Polystomatidae Gamble (1896). Fuhrmann (1931) lists the group in the suborder Polyopisthocotylinea, family Onchocotylidae.

A simple but efficient apparatus for harvesting nematodes migrating from their insect hosts is described. Infected host larvae are supported, in contact with water, on a nematode-permeable diaphragm resting in the mouth of a large funnel. A battery of funnels can be connected in series and their water-level maintained by a common constant-level device.

When, in 1917–18, I made a microscopic examination of freshwater snails at Potchefstroom, Transvaal, I found 10 per cent, of the examples of Isidora schackoi Jickeli infested with eye-spotted cercariae which Dr E. C. Faust recognised as amphistomes. Some shells which I collected from the same pools and considered to be immature examples of Isidora schackoi have been identified as Sericima. It is possible that the two species are identical. I found Isidora forskali at Cato Manor, outside Durban, infested with amphistomes, and confirmed this observation by isolating similar cercariae from the same freshwater snail on the Umgeni flats. I have obtained examples of Isidora forskali from Amanzimtoti, Isipingo, Clairwood, Umhl-a-tazana, Cato Manor, Inchanga station, Umgeni, Tongaat, Nonoti, Umzindusi, at Pietermarizburg, Lourenço Marques and Beira. These places constitute several new localities for the species and no Isidorae had previously been recorded from Beira. This mollusc is common in small shallow spruits and is often attached to small plants or water-lily leaves. It is seldom more than 10 mm. in length.

Laboratory bred DSN hamsters were exposed to varying doses of infective larvae of Ancylostoma ceylanicum (orally) or Necator americanus (percutaneously) and were autopsied at times which corresponded to a period immediately before cessation of growth of worms or soon afterwards. A total of 829 (404 male and 425 female) A. ceylanicum and 1582 (781 male and 801 female) N. americanus were measured. At worm burdens of fewer than 100, the length of A. ceylanicum appeared to increase with infection intensity and no evidence was found that growth was retarded under crowded conditions. In an experiment comparing directly low (mean worm burden = 22) and heavy infections (mean worm burden = 180) significant negative associations between both weight and width, and worm burden were detected, but length again increased with worm burden. In contrast, 5 experiments with N. americanus indicated negative relationships between measures of worm size (length, width, wet and dry weight) and worm burden. It was concluded that N. americanus is subject to regulation by density-dependent processes within the host while A. ceylanicum is not sensitive to the same degree.

1. The biology, as studied under laboratory conditions, of O. savignyi is very similar to that of O. moubata.

2. Females may oviposit over 400 eggs, of which at least 60 per cent, may be fertile; parthenogenesis does not occur.

3. An increase in temperature of 8° C. (from 22° C.) decreases the longevity of the female from 775 to 358 days, i.e. by 45 per cent.; an increase of 7° C. (from 30° C.) reduces the period required for the production of third stage nymphs by 26 per cent. At 30° C., the mean minimum periods required for metamorphosis are 60 days for males and 73 days for females (cf. O. moubata, 36 days for males and 45 days for females). Reproduction was inhibited at 37° C.

4. Moisture is an unfavourable factor, decreasing the vitality of the individual at each stage of growth.

5. Changes in external anatomy undergone during development are similar to those already described for O. moubata.

1. Mepacrine has a damaging action upon both vegetative forms and cysts of Giardia intestinalis. The action upon the former is rapid; but the action upon the cysts is gradual, and it takes 4 days of incubation in a 0·06% mepacrine suspension before all normal cysts disappear. The degeneration of cysts is accelerated by raising the concentration of mepacrine to which they are exposed.

2. Mepacrine produces a characteristic degeneration of the cyst which can be seen both in vitro and in vivo. This appearance develops gradually. In affected cysts the wall appears unaltered; but the protoplasm becomes shrunken and yellow, occupying only a small part of the internal cyst space. Whether shrunken or not, protoplasm stained by mepacrine is probably too much injured to survive, although the intense yellow colour makes it difficult to demonstrate eosin staining.

3. When parasites showing the characteristic abnormality are seen in the faeces they should be recognized as degenerate cysts, and further specimens should be examined before the patient is pronounced free from infection.

4. The usual method of treating a Giardia infection with mepacrine in a dosage of 0·05–0·3 gm. daily according to age, given by mouth for 6 days successfully eradicates the parasite, which is killed in both cystic and vegetative stages, but this dose is near to the minimum effective and neither time nor dosage can safely be reduced if a reliable cure is wanted.

5. Caustic soda destroys the whole cyst fairly rapidly, while a detergent had a damaging action on the protoplasm. Alkaline detergent solutions may therefore be recommended for the cleansing of infected utensils and premises. Dettol and Lysol kill cysts within 30 min. (judged by eosin staining), and 1% solutions of these disinfectants appear as effective as 5%. Utensils should be left to soak in the disinfecting solution since some cysts are slower to be affected than are others.

6. Cysts of Giardia are fairly resistant to acid, and up to 50% of them survived 4 hr. incubation in hydrochloric acid at a concentration of 0·26 gm.%, which corresponds to the upper limit of normal human gastric acidity (Harrison, 1947).

7. The cysts were damaged in different ways by different substances. In some cases the cyst was unchanged in appearance and yet rendered susceptible to eosin staining, in others the nuclei alone stained with eosin. Sometimes the protoplasm shrank within an intact cyst wall, and sometimes the wall was attacked directly.

8. In each sample of faeces studied in these experiments the Giardia cysts present appeared to be of unequal vitality, since, whatever the test substance to which they were exposed, and whatever form of degeneration developed, some cysts were affected hours or days before others showed any changes. It is conjectured that the age of the parasite since encystment may influence its resistance to damage.

Grateful acknowledgements are made to the practitioners and Medical Officers who co-operated in the following-up of cases of Giardiasis after they had been treated by mepacrine.

Separation of pig slurry into solid and liquid fractions is gaining importance as a way to manage increasing volumes of slurry. In contrast to solid manure and slurry, little is known about pathogen survival in separated liquid slurry. The viability of Ascaris suum eggs, a conservative indicator of fecal pollution, and its association with ammonia was investigated in separated liquid slurry in comparison with raw slurry. For this purpose nylon bags with 6000 eggs each were placed in 1 litre bottles containing one of the two fractions for 308 days at 5 °C or 25 °C. Initial analysis of helminth eggs in the separated liquid slurry revealed 47 Ascaris eggs per gramme. At 25 °C, egg viability declined to zero with a similar trend in both raw slurry and the separated liquid slurry by day 308, a time when at 5 °C 88% and 42% of the eggs were still viable in separated liquid slurry and raw slurry, respectively. The poorer survival at 25 °C was correlated with high ammonia contents in the range of 7·9–22·4 mm in raw slurry and 7·3–23·2 mm in liquid slurry compared to 3·2–9·5 mm in raw slurry and 2·6–9·5 mm in liquid slurry stored at 5 °C. The study demonstrates that at 5 °C, A. suum eggs have a higher viability in separated liquid slurry as compared to raw slurry. The hygiene aspect of this needs to be further investigated when separated liquid slurry is used to fertilize pastures or crops.

Host behavioural modification by parasites is a common and well-documented phenomenon. However, knowledge on the complexity and specificity of the underlying mechanisms is limited, and host specificity among manipulating parasites has rarely been experimentally verified. We tested the hypothesis that the ability to infect and manipulate host behaviour is restricted to phylogenetically closely related hosts. Our model system consisted of the brain-encysting trematode Euhaplorchis sp. A and six potential fish intermediate hosts from the Order Cyprinodontiformes. Five co-occurring cyprinids were examined for naturally acquired brain infections. Then we selected three species representing three levels of taxonomic relatedness to a known host to experimentally evaluate their susceptibility to infection, and the effect of infection status on behaviours presumably linked to increased trophic transmission. We found natural brain infections of Euhaplorchis sp. A metacercariae in three cyprinids in the shallow sublittoral zone. Of the three experimentally exposed species, Fundulus grandis and Poecilia latipinna acquired infections and displayed an elevated number of conspicuous behaviours in comparison with uninfected controls. Euhaplorchis sp. A was able to infect and manipulate fish belonging to two different families, suggesting that ecological similarity rather than genetic relatedness determines host range in this species.

Malaria remains one of the most devastating diseases. Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection resulting in high mortality and morbidity worldwide. Analysis of precise mechanisms of CM in humans is difficult for ethical reasons and animal models of CM have been employed to study malaria pathogenesis. Here, we describe a new experimental cerebral malaria (ECM) model with Plasmodium berghei ANKA infection in KunMing (KM) mice. KM mice developed ECM after blood-stage or sporozoites infection, and the development of ECM in KM mice has a dose-dependent relationship with sporozoites inoculums. Histopathological findings revealed important features associated with ECM, including accumulation of mononuclear cells and red blood cells in brain microvascular, and brain parenchymal haemorrhages. Blood–brain barrier (BBB) examination showed that BBB disruption was present in infected KM mice when displaying clinical signs of CM. In vivo bioluminescent imaging experiment indicated that parasitized red blood cells accumulated in most vital organs including heart, lung, spleen, kidney, liver and brain. The levels of inflammatory cytokines interferon-gamma, tumour necrosis factor-alpha, interleukin (IL)-17, IL-12, IL-6 and IL-10 were all remarkably increased in KM mice infected with P. berghei ANKA. This study indicates that P. berghei ANKA infection in KM mice can be used as ECM model to extend further research on genetic, pharmacological and vaccine studies of CM.

The effect was compared in CBA mice of adding Corynebacterium parvum, saponin, and Bordetella pertussis to living or killed Trypanosoma cruzi (Y strain) epimastigote vaccines on the induction of protective immunity against subcutaneous (s.c.) challenge with blood trypomastigotes. The addition of C. parvum to a low dose of T. cruzi vaccine, which alone was non-protective, generated a greater degree of protection than did saponin or B. pertussis. C. parvum alone increased resistance to infection to a variable and usually weak extent. The addition of C. parvum to larger doses of T. cruzi vaccine, which were themselves sufficient to elicit some degree of protection, improved resistance when the challenge was given 1 or 12 weeks after immunization, but lowered it at 3 weeks. It is concluded that the comparative efficacy of adjuvants for T. cruzi vaccines needs to be assessed on 3 parameters: (1) the dose of antigen, (2) the dose of adjuvant and (3) the time interval between immunization and challenge.

On many occasions during the years 1921 and 1922 I devoted my leisure to collecting Cestode and other Helminth parasites from wild birds in the United and Central Provinces of India. A large proportion of the material collected consists of species already known but the remainder contains some new and interesting forms, and three of these I am describing in the present paper.

During my stay at the Zoological Station of Wimereux, Pas de Calais, France, in August 1934, I made a special study of Protozoa parasitic in marine fishes. The examination of ten specimens of young Raia batis revealed a coccidial infection in two individuals, measuring about 25 cm. in length. In one of these the mucus in the terminal portion of the intestine contained a few unsegmented spherical oocysts, with diameters from 24 to 28μ. Sections of different portions of the intestine and of the liver failed to exhibit any stages of schizogony or gametogony, evidently owing to the fact that there was a single infection at the end-phase. However, the second skate showed very numerous unsegmented oocysts in the posterior portion of the alimentary canal (Pl. I, fig. 1). This specimen provided material for the morphological study and biological observations which follow.