Intestinal infections with parasitic worms are wide-spread in the Tropics. It is estimated that half the population of the World is infected with hookworms. Infection is propagated by contamination of the soil with the bowel discharges which contain the eggs of these parasites and prevention depends upon the adoption of a system of sewage carriage which ensures the safe disposal of the distribution of these eggs. The various methods of sewage disposal now operating in British Guiana and elsewhere in the tropics are adaptations, with few or no alterations, of schemes originally introduced to meet conditions prevailing in temperate climates. Prior to the visit of the Filariasis Commission of the London School of Tropical Medicine to British Guiana in 1921 the fate of the eggs of the hookworm and of other parasites in the system has not been scientifically studied.

Serine dehydratase was found to be five times more active than threonine dehydratase in the liver-fluke Fasciola indica. The latter was not affected by L-isoleucine. Optimum pH for both enzymes was found to be 9.0 in tris-universal buffer. Seven metallic ions tested did not accelerate the enzyme activity, but produced different effects on two enzymes. Two different enzymes probably exist for the two aminoacids, L-threonine and L-serine.

Incidence of mating pairs in 40 worm infections in 5 week old female CBA mice increased up to day 30 post infection. By this time, and thereafter until the experiment ended on day 70, approximately 60% of the worm population occurred as mating pairs. Mating began during the ontogenetic migration of the worms. There was no difference between the percentage of worms mating in the more highly populated anterior sections of the small intestine as compared to the less densely populated more posterior sections. Significantly more female than male worms were recovered between days 8 and 20 post infection (p<0.02 to 0.001) and there was a significant decline in overall recoveries during the experimental period (r = −0.77, p<0.01). Low intensity infections, with 4 to 16 worms per mouse, demonstrated that a larger percentage of worms in the infection were mating at an earlier time post infection than in the 40 worm infections. Ontogenetic migration was reduced in low intensity infections because the initial distribution of worms was more restricted.

In March 2011, a predator killed 33 hooded grebes, Podiceps gallardoi Rumboll (Podicipedidae), a critically endangered species, in a nesting colony at El Cervecero Lake, Santa Cruz Province, Argentina. The viscera of ten birds were examined for helminths. Two new species of Trematoda were recovered from the intestines. The plagiorchid Plagiorchis patagonensis n. sp. is mainly characterized by the larger size of the oral sucker relative to the ventral sucker, and by the distribution of the vitellarium in two lateral fields, confluent between the caecal bifurcation and the ventral sucker. The echinostomatid Euparyphium tobianum n. sp. is mainly characterized by possessing a head collar with 37–39 spines (4 angle spines on each ventral lappet, 4 lateral spines in a single row on each side, and 21–23 dorsal spines in a double row). An unidentified cestode, a tetramerid nematode and a notocotylid trematode were also recovered from the birds. This is the first record of helminths parasitizing the hooded grebe.

Lake Teletskoye (West Siberia, Russia) is inhabited by a sympatric pair of whitefish, with each member of the pair being characterized by different feeding habits. Coregonus lavaretus pidschian (Gmelin, 1789) is a large ‘benthivorous’ form, while C. l. pravdinellus (Dulkeit, 1949) is a small ‘planktivorous’ form. Fish were collected from the end of August to the middle of September in 2017 and 2019–2020 in the north part of Lake Teletskoye. For the ‘benthivorous’ form the prevalence, intensity and abundance of T. crassus ranged from 22.4% to 51.9%, 1.9–2.8 and 0.4–1.3, respectively, whereas the same indices for the ‘planktivorous’ form ranged from 94.7% to 97.5%, 4.2–4.8 and 4.0–4.7, respectively. The level of prevalence of infection and abundance of T. crassus in muscle was relatively stable among studied years for both forms. The level of prevalence was higher in the years 2019 and 2020 than in 2017 for the ‘benthivorous’ form, whereas for the ‘planktivorous’ form this index did not change during the studied years. For the first time, a partial sequencing of the cox1 gene (593 bp) for T. crassus was sequenced. All 15 plerocercoids of T. crassus were represented by four haplotypes.

Many important studies on resistance reversion, anthelmintic efficacy and, especially, new molecules with antiparasitic effects are performed in laboratories using gerbils (Meriones unguiculatus) as the experimental model. This study aimed to evaluate the use of corticosteroids (dexamethasone and methylprednisolone acetate) in gerbils experimentally infected with different doses of infective larvae (sheathed or exsheathed) of Haemonchus contortus. In the first experiment, 28 gerbils were divided into seven groups infected by 2–6 × 103 larvae, with or without immunosuppression using corticosteroids. In the second experiment, eight gerbils were divided into two groups infected by 2 × 103 sheathed or exsheathed larvae. For the third assay, seven immunosuppressed gerbils were infected with 2 × 103 sheathed larvae and were killed 15 days post infection (PI). The highest number of parasites was recovered from methylprednisolone-immunosuppressed animals. We observed red and white blood cell alterations and biochemical parameters in infected animals that had undergone immunosuppression with methylprednisolone. We highlight that in the first and second experiments a satisfactory number of worms was recovered using sheathed larvae and immunocompetent animals. When exsheathed larvae were used, the number of worms recovered was unsatisfactory. A considerable larval burden was recovered from immunosuppressed gerbils 15 days PI, and body weight did not influence establishment of larvae.

Fifteen female ICR mice, 6–8 weeks old, were each exposed to 25 metacercarial cysts of Echinostoma caproni. To determine the effects of withholding food on survival, size and distribution of E. caproni in ICR mice, two groups of five each were maintained without food for 1 day (group A) or 2 days (group B) prior to necropsy. Group C consisted of five mice maintained with food for the duration of the experiment. All mice were necropsied at 12 days postinfection. There was no significant difference in worm survival, body area or distribution between group A and C or group B and C mice. The results of this experiment show that short-duration removal of food has no effect on worm survival, size or distribution of E. caproni adults in the small intestine of the ICR mouse.

For many years it has been recognised that the nematode, Anguillulina dipsaci, is a major pest of narcissus, and growers and scientific workers alike are familiar with the presence of damaged and discoloured tissues within the bulbs, accompanied by swelling and distortion of the foliage, which are, prior to the death of the bulb, associated with attack by this pest. Certain other nematodes are sometimes responsible for somewhat similar injury to the bulbs, and in 1932 Steiner & Buhrer published a short account of those nematodes which have, on occasion, been found within and apparently been responsible for the diseased condition of narcissus bulbs in U.S.A.

The efficacy of eight anthelmintics against Ancylostoma caninum larvae in the skeletal muscles of mice was evaluated. Levamisole (5 × 40 mg kg), thiabendazole (5 × 400mg kg), oxfendazole (5 × 100mg kg), albendazole (5× 1OOmg kg), flubendazole (5 × 200 mg kg), benacil (5 × 200 mg kg) and phenacizole (5 × 200mg kg) showed marked larvicidal activity (98 to 99%). Sch 18099 did not show larvicidal activity even at 5×400 mg kg.

The following collection of Cestodes has been brought together by Prof. A. S. Pearse, of the Duke University, Durham, N.C., during a sojourn in Nigeria for the purpose of studying the parasites of rodents and insectivores.

The existence of adult Schistosoma haematobium worm proteins (Sh31/32) homologous to the diagnostic Sm31/32 of S. mansoni is shown. Sm31/32 and Sh31/32, adsorbed on nitrocellulose and kept dry on the bench before immunoblot analysis, were antigenically stable for at least 4 years including storage for 17 months in tropical climates. The antigens react with patient sera in the absence of defined buffers under rather simple conditions (“humid chamber blot”). The results add to the use of these antigens for serodiagnosis of schistosomiasis in endemic areas.

Paruterina quelea sp. nov. is described, and brief details given of P. zambicnsis Mettrick, 1960, and P. pentamyzos Mettrick, 1960. Details of all the species at present in the genus Paruterina are listed.

Re-descriptions are given of Metroliasthes lucida Ransom, 1900, and Biuterina rectangula Fuhrmann, 1908.

This study shows that some cercariae of S. haematobium and S. mansoni die during penetration of mouse or hamster skin.

Approximately 30–38% of cercariae of both species die in mouse skin and 14–16% die in hamster skin. The greater number of cercariae which die in the skin of mice seems to account for the higher yield of adult worms recovered in hamsters. Adult worm recoveries from animals infected with S. haematobium were, however, only about half the worm recoveries from hosts infected with S. mansoni.

Acquired immunity to Nematospiroidcs dubius was studied in the jird. It was found that a primary infection comprising one or two worms was highly immunogenic and the animals were resistant to challenge infection. Abbreviated infections in which the adult worms were eliminated by treatment with pyrantel also elicited strong resistance to challenge indicating that larval parasites as well as adults were involved in acquired immunity. A small proportion of adult worms completed their development in immune jirds and was recovered 11 days after the challenge infection. However, these worms were rapidly eliminated and few survived to day 16. Trickle infections in which the jirds were exposed to very low numbers of worms at regular intervals were unsuccessful in prolonging the duration of a primary infection. It was concluded that theremarkable sensitivity of the jird to infection with N. dubius should enable small quantities of fractionated parasite derived material to be screened for immunogenicity in this host.

Six new nematode species of Dorylaimida are described from soil around roots of cotton plant in Uttar Pradesh, India : Discolaimium mazhari, D. upum, Aporcelaimellus heynsi, A. indicus, Leptonchus capitatus and Amphidelus novus. Keys to the species of the genera Discolaimium Thorne, 1939 and Aporcelaimellus Heyns, 1965 have also been provided.

PCR-RFLP techniques have been used to characterize wild and laboratory isolates of the trichostrongyle nematode Heligmosomoides polygyrus from the wood mouse Apodemus sylvaticus and the laboratory mouse Mus musculus respectively. Both isolates can be distinguished by eight endonuclease digestions of the ITS region of the rDNA repeat namely, Alu I, Dde I, Hpa II, Hae III, Hinf I, Hha I, Pvu II and Sal I. In two of the digests, Hinf I and Rsa I, a minor polymorphism was observed in the wild isolate of H. polygyrus which has been cultured in laboratory-bred A. sylvaticus for several generations when compared with H. p. polygyrus from wild A. sylvaticus. A minor polymorphism was also identified in further wild isolates of H. polygyrus collected from A. sylvaticus in a field site in Egham, Surrey. However no evidence of polymorphism was observed in the laboratory isolate of H. polygyrus from the CD1 strain of M. musculus and the laboratory-bred A. sylvaticus. Reasons for this are discussed and further studies on the population genetics of H. polygyrus are suggested.

Two new species of the genus Oochoristica Lühe, 1898 from Australian dasyuried marsupials are described and their affinities discussed. The new species are O. antechini sp. nov. from Antechinus macdonnellensis and O. eremophlia sp. nov. from Antechinus rosamondae.

Paragonimus ohirai-infected rats were treated with cyclosporin A (CyA) at different times during the course of infection. CyA (5×80 mg/kg) affected the worm recovery, growth and maturation rates of P. ohirai with respect to control values. This tendency was most remarkable in animals treated 15 days and more after infection with CyA (groups B, +15 to +19 days; C, +25 to +29; D, +35 to +39 and E, +45 to +49). In group A (0 to +4), however, the drug did not affect markedly the growth and maturation of worms, although it significantly lowered worm recovery rates. CyA administration also affected normal migration of P. ohirai in the highly susceptible host (rat), when the drug was administered during the peritoneal and/or liver phase of infection. Thus, in this P. ohirai/rat model, CyA significantly reduced worm recovery rates, and affected the growth, maturation and migration of the worms depending on the time of administration.

The prophylactic and curative effects of praziquantel and oxamniquine on a Saudi Arabian strain of Schistosoma mansoni in MF-1 mice were assessed. The drugs were administered orally. At 240 mg/kg praziquantel, there was a reduction of 89·1% in adult worm recovery and a marked reduction in tissue deposited eggs. The reduction in adult worm recovery after dosing with 50 mg/kg oxamniquine was 89·2%. At low doses (40 mg/kg praziquantel and 30 mg/kg oxamniquine) administered at 11 days, 5 days and 3 h before and 5, 21 and 49 days after infection, the reduction in adult worm recovery was 0·0%, 65·1%, 58·8%, 33·6%, 0·0% and 76·0% for praziquantel and 0·0%, 66·0%, 60·0%, 41·3%, 10·8% and 79·0% for oxamniquine. Numbers of lung schistosomula and the size of hepatic granulomata were also reduced.

Shelled acanthors (=eggs) of two isolates of Moniliformis moniliformis (Acanthocephala) were tested for their capacity to respond to a hatching stimulus in vitro and for their retention of infectivity to a natural intermediate host (Periplaneta americana). The shelled acanthors were stored for more than 120 weeks (Australian isolate) and for 104 weeks (Texan isolate) together with rat faeces in an incubator maintained at 22·2±0·1°C. In both cases, infectivity to P. americana was shown to have been retained. In vitro tests of the hatching response were carried out on many occasions during this period of faecal storage. Shelled acanthors continued to respond and no differences were detected either between isolates or within an isolate through time.