Trypanosomes are consistently present in the milk of lactating mice with primary phase T. cruzi infections (Peru strain). The infection is transmitted to the young, although rarely, mainly due to the difficulty of establishing infection via the oral route. Lactating females which had recovered from the primary phase of T. cruzi infection consistently transferred antibody to their young during suckling. The antibody in the serum of the young and milk of the mother was detectable by the indirect fluorescent antibody technique. In the case of the Peru strain the presence of antibody transferred to the young in this way correlated with very good protection against T. cruzi. Antibody transferred to the young was no longer detectable 6 weeks after birth. The indirect fluorescent antibody technique using bloodform antigen proved specific and highly sensitive throughout, giving prolonged and comparably high titres in mice infected with chronic and acute strains of T. cruzi.

Two new species of the genus Hoplopleura are described from two closely related species of the genus Mus. H. ramgarh sp.nov. was found parasitizing Mus platythrix Bennett, 1932, in the Western Himalayan region in North India and in the Western Ghats in Peninsular India. H. sinhgarh sp.nov. was found parasitizing a species of the genus Mus, closely related to M. platythrix, and occurring sympatrically with it. The exact taxonomical status of this rodent species is still under investigation. The occurrence of two distinct species of lice on closely related sympatric populations of these mice has given an indication of their being two distinct taxa, a fact later supplemented by some consistent but not easily delineable skin and skull characters.

Groups of R. appendiculatus ticks infected with T. parva were irradiated at doses varying from 0 to 32 krad and then applied to rabbits; 3 and 4 days later their salivary glands were removed, processed and examined. Increasing doses of irradiation resulted both in a decreased infection rate of ticks and a decrease in the number of parasite masses observed in infected ticks. No normal parasite masses were seen after doses of 4 krad or above.

(1) Simulium ornatum larvae were regularly collected from the River Lea (Hertfordshire) and from Tilling Bourne (Surrey) during 1967–9. Preliminary surveys revealed no parasitism in pupal and adult stages of S. ornatum but several parasites, some common, occurred in the Simulium larvae. These were studied by dissection, smears and histologically. (2) Microsporida were well represented by two genera - Thelohania and Plistophora. Infection rates never exceeded 9% of larvae. Spore measurements statistically evaluated from different larval infections justified recognition of five species of Thelohania (T. minuta sp.nov., T. bertrami sp.nov., T. canningi sp.nov., T. simulii sp.nov., and T. avacuolata sp.nov.), and two species of Plistophora (P. tillingbournei sp.nov. and P. leasei sp.nov.). (3) Intra-epithelial organisms of the larval gut wall, referred to provisionally as Microsporidan-like bodies, caused light infections. (4) With the exception of the slight Microsporidan-like infections, all species of Microsporida were found parasitizing the fat body of the larva, causing its disintegration. Delay in larval growth and pupation occurred, followed by death. (5) Seasonal cycles of abundance of infection were related to summer and overwintering populations of Simulium larvae. (6) Transmission of infection was attempted by exposing apparently uninfected wild-caught Simulium larvae to spores of Thelohania but no evidence of active infection being established in the exposed larvae was obtained. (7) Although the pathogenic Microsporida taken in this study must have exerted control on natural larval densities, too little is known of their biology, mode of transmission or methods of culture to envisage their development, for biological control of simuliids, at present.

Some monocystids of British earthworms are widely distributed, occurring in hosts which were collected from different parts of the country, whereas others are localized or irregularly distributed. Only nine of the 45 monocystids identified from British earthworms have been reported from similar hosts collected from France, Germany and Sweden. Fourteen others occur in similar hosts collected from one or two of the continental countries and the remaining 22 monocystids appear to be completely absent from continental earthworms.

Saponin treatment of cercariae and schistosomula alters the surface membrane so that it may be sheared from the organism and isolated as fragments by centrifugation. Saponin-calcium chloride treatment or freezing and thawing of adult worms removes the surface membrane, which can be washed from the bodies and collected by centrifugation. The small quantities of material available necessitated the development of a sensitive technique for detecting the proteins in the membranes. The surface membranes were radioiodinated after butan-1-ol extraction and electrophoresed in polyacrylamide gel. Adult surfaces prepared by the saponin-calcium chloride and by the freezing and thawing technique had identical protein components, detected as gel-cut profiles or in autoradiographs. The quantity of a rapidly migrating PAS-positive amido black negative component was greater in the surfaces prepared by saponincalcium chloride than in the frozen and thawed surfaces. This component contains lipid, some of which may be glycolipid. It was largely absent from the surface membranes of cercariae and schistosomula. Cercarial surface membranes contained a major protein component which was absent from the surface membranes of schistosomula. Otherwise the surface membranes of the cercariae were identical to those of the schistosomula in their protein components. The rate of incorporation of freshly synthesized protein per unit area of surface membrane of schistosomula was very low in the first 5 days in culture, after which there was a very rapid increase to a maximum rate on the 15th day. After this time, the rate of protein synthesis decreased to a low level at 26 days. In these studies the activity per unit area was measured and this would not be expected to vary greatly during growth. The biological significance of the observed variation in protein incorporation into the membrane is unclear.

The ultrastructure of the normal caecum of chickens and of chickens infected with Trichomonas gallinarum has been investigated. In infected caeca some villi and crypts of LieberkÜhn appear normal whereas others show marked changes in structure of the epithelial cells. The most obvious changes are loss of microvilli and glycocalyx and an increase in number of vesicles which stain metachromatically with Azur II. T. gallinarum has been detected between epithelial cells and in the lamina propria. Bacteria often, but not always, accompanied the protozoa in the tissues.

Ultrastructural examination of the parasite-host interface of three tetraphyllidean cestodes of Raja naevus (sectioned attached to the intestine) indicates that while the strobilar tegument of each closely follows the typical cestode pattern that of the bothridia has several modifications probably associated with attachment. Microtriches similar to those of the strobilum are absent, although small spines on Echeneibothrium sp. and Phyllobothrium piriei and wart-like structures on Acanthobothrium quadripartitum bothridia are considered to represent the osmiophilic tips of specialized microtriches. The bothridia of the three species have no apparent function in the absorption of food but evidence suggests that the apical pad of the myzorhynchus of Echeneibothrium is specialized for the uptake of nutrients directly from the submucosa of the host intestine to which it is applied. Attachment and sensory roles by the myzorhynchus are also indicated. Echeneibothrium and P. piriei bothridia severely damage the host mucosal surface, while those of A. quadripartitum do little harm. This difference is probably associated with the size, mobility and mode of attachment of the cestodes. There are indications that the bothridia of Echeneibothrium upset the metabolism of mucosal cells in the attachment region. The tips of the strobilar microtriches of A. quadripartitum are shown to function in the attachment of the strobilum to the host mucosa, and in the protection of the microthrix proximal surfaces by a filtering action.

A description is given of a Babesia-like parasite found in the erythrocytes of two Cercopithecus pygerythrus monkeys probably from East Africa. Morphologically it seems identical with a parasite found by Mayer (1934) in Macaca irus monkeys from Java and named by him Entopolypoides macaci. On the other hand, the present African type differs from the Javan one in that it does not readily infect M. irus or M. mulatta monkeys; and it might well be named provisionally E. macaci (cercopitheci). Morphologically, the early forms are fine rings with a large vacuole but the more mature parasites form several fine long processes which are best seen under phase-contrast illumination. The cycle in the erythrocytes probably ends by division into four new parasites and it takes 3 days to quadruple the number. There is no synchronicity, such as occurs with malaria. The parasite was passed by syringe into Erythrocebus patas, Papio papio and Cercocebus galeritus monkeys in which it produced a light parasitaemia if they were intact, or an intense one (up to 70% erythrocytes parasited) if they were splenectomized. In both cases the bouts of parasitaemia are prolonged for weeks, and they may continue with relapses apparently for years. A light transient infection was produced in one splenectomized Macaca mulatta and in one out of two intact M. irus monkeys, but not in one M. arctoides (splenectomized), one Cebus albifrons, one C. apella, two Aotus trivirgatus and two Pan troglodytes (one splenectomized). Apparently the parasite readily infected African lower primates, hardly infected Asiatic ones, and did not infect American ones. Even in susceptible splenectomized monkeys, in which it produced prolonged intense parasitaemia, the parasite causes little pathogenic effect beyond a moderate anaemia. Attempts were made to transmit it through Rhipicephalus sanguineus, Dermacentor andersoni, Ornithodoros (sp.), Ornithonyssus bacoti and Aedes aegypti but they were unsuccessful. Probably the vector is an Ixodid tick. Chemotherapeutically the parasite was sensitive to a babesicidal compound, Imidocarb (3,3′-bis-(2 imidazolin-2yl) carbanilide) and to primaquine but not to chloroquine, pyrimethamine, pentamidine, Berenil or homidium.

Cortisone, methotrexate and anti-lymphocyte serum were all found to suppress the rejection by SPF CFLP male mice of H. diminuta, which normally occurs between days 9 and 12. Worms continued to grow in mice given immunosuppressants and matured on days 16–18 as they would in a rat, by which time they stretched from the stomach to, and sometimes into, the caecum. Worms in mice given methotrexate ceased to grow after day 16, but this was believed to be due to the deterioration of the host's intestine wall; in mice receiving cortisone growth was faster than normal and worms continued to increase in size until the end of the experiments on days 20–24. The mouse/H. diminuta system is discussed, emphasizing that, as far as is known, H. diminuta (which has no hooks) has no close contact with the tissues and that this is a case of a mammal responding against an organism living freely in the lumen.

The third-instar larval cuticles of Hypoderma bovis and H. diana and the puparial cuticle of H. bovis are described. The observations on and the descriptions of these cuticles are compared with the work of Enigk & Pfaff (1954) on H. bovis larval cuticle. The cuticles of the Hypoderma species are compared with the typical dipteran larval cuticle described by Dennell (1946) for Sarcophaga and found to approximate very closely to this basic pattern. In view of this it has been necessary to revise the terminology of the cuticular layers as originally described by Enigk & Pfaff for Hypoderma bovis. A description of the puparial cuticle and its specialized structure and the histological appearance of the pupal suture or line of weakness is given.

In chickens kidney-cell culture gametogony of E. tenella usually occurs in a limited number of selected cells in the form of nests of gametocytes. Some cells contain only macrogametocytes, others only microgametocytes and some cells contain both sexes together. Mixed nests of gametocytes are evidence for genetic sex determination. By using PAS staining the origin of macrogametocytes and microgametocytes can be retraced to the merozoites and schizonts of the last generation, which are differentiated by this technique.

The growth of Hymenolepis microstoma in weanling (21–23 days old) and adult (> 10 weeks old) rats has been investigated. Growth proceeded normally until the worms were about 9 days old. They then destrobilated, leaving only the scolex attached to the duodenum or bile duct. In only 1% of the rats did growth of the worms continue beyond 10 days and these large worms caused the bile ducts of their hosts to become distended. Immuno-suppressants had no effect on the growth of the worms, and tests suggested that there was no serological reaction to infection. It was concluded that the rat is a poor host for Hymenolepis microstoma but that it is not completely refractory.

A survey in Busoga District, Uganda, where an outbreak of sleeping sickness was detected, has yielded an infection rate with T. brucei subgroup in G. fuscipes of 4.8%. Isolation of the infected flies was by feeding of the flies on mice, followed by trituration and inoculation of a suspension of the triturated flies into mice. The mice were treated with cyclophosphamide to reduce the immune response. The percentage infection as determined by inoculation of triturate was 4.1%, whilst that by feeding on mice was 1–8%. Amongst the 19 strains of T. brucei subgroup isolated, four were identified as T. rhodesiense by the BIIT method.

Six species of South African parasitic copepods belonging to the family Chondracanthidae were restudied. A redescription was given of Acanthochondria lepidionis, Ghondracanthus colligens and Ch. neali. Ch. lophii reported by Barnard (1955a) is actually a new species; it was named Ch. barnardi and redescribed. Ch. congiopodi Barnard, 1955, is conspecific with Ch. tuberculatus Nordmann, 1832. A redescription of this species was given based on Barnard's collection. Ch. merluccii was only mentioned and not redescribed.

No external signs of activation of cystacanths in the alimentary tract were observed until 25 min after oral ingestion. Peak percentage evagination was observed after 60 min. Activation and establishment of cystacanths were never found in the ventriculus or anterior to it, but several crushed specimens were found in the ventriculus, which is a mechanical hazard to the parasite. Infections established by cannulation at the yolk-stalk are greater than infections produced by ingested parasites; thus the ventricular environment does not need to be experienced by the freed cystacanth for activation to take place.

The initial pattern of oogenesis after a feed is similar for mated and unmated A. persicus. The peak number of mature oocytes within the females occurred on the seventh day at 30 °C. Both groups ovulated but only mated females oviposited. At the end of the first week the mature eggs of unmated females began to undergo dissociation and resorption. The early onset of this process seems to exclude the presence of unlaid eggs as a factor inhibiting ovarian maturation. Many more eggs matured within the mated than the unmated female. After oviposition, the ovaries appear as in the unfed virgin except oocytes are fewer. When the male was mated consecutively to the 7–8th virgin female, there was a decrease in the number of eggs laid. This indicates that the male factor(s) effecting oogenesis and oviposition act on a quantitative rather than an ‘all or none’ basis. To determine whether a female was effectively mated, the ampulla must be checked for sperm. The reason for this is that the spermiophore capsules may be resorbed or may lack sperm. Spermless spermiophores enhanced fecundity but did not effect oviposition. There was evidence of mechanical influence on oocyte maturation when beads were introduced into the vagina of A. persicus. An increase in the number of beads increased the number of mature oocytes. Chemical influence on oogenesis was demonstrated by injection of male gland complex into the body cavity of unmated females.