The fourth-stage larvae and adults of Ascaris suum were studied as they developed in the pig intestine from 11 to 22 days after infection. This is a period of rapid growth, in which both sexes increase approximately ten-fold in body length. Further examination of females showed the length increase to be positively allometric with respect to body diameter. The genital primordium in early fourth stage is at the same relative position along the length of the body as it is in the newly hatched larva. During development from fourth stage to adulthood the greater growth of the posterior part of the worm causes the relative position of the developing vulva to shift anteriad.

Studies were made of the fate of irradiated cercariae of Schistosoma mansoni, during their migration as schistosomula in the definitive host, by direct recovery of intact schistosomula from the skin and lungs and of adult worms from the liver of infected mice. Gamma radiation (6000 r) inhibited the migration and maturation of S. mansoni schistosomula to the adult stage. Penetration of irradiated cercariae into host skin proceeded normally and the first site of damage was in the lungs, but the majority of irradiated schistosomula were probably destroyed in the liver. The efiects of gamma radiation compared with those of ultra-violet radiation on cercariae of S. mansoni are discussed.

Allocreadium sudanensis sp. nov. is described from a cyprinid fish (Barbus bynni) from the White Nile in the Sudan. The new species is compared with other related species of Allocreadium.

A key for identification of five African species of the genus Allocreadium is given.

The present material was collected by the senior author in January, 1969 from the intestine of a cyprinid fish, Barbus bynni (Forskal), caught from the White Nile at Rabag near Kosti (about 200 miles to the south of Khartoum) in the Sudan. Eighteen trematodes, collected from a single infected fish, were fixed in hot 70% alcohol. Examination of these specimens in whole mounts stained in aceto-alum carmine and in sectioned material revealed that they belong to a hitherto unknown species of trematodes belonging to the genus Allocreadium, Looss (1900) which is described here as Allocreadium sudanensis sp.

Adult trematodes identified as Galactosomum ussuriense Oshmarin, 1963 were recorded from the intestine of Sterna hirundo and Larus brunnicephalus from Visakhapatnam, India. The occurrence of metacercaria of this species in inshore and offshore fishes is discussed in relation to the ecology of the snail intermediate host.

Female ICR mice, 5 to 6 weeks old, were exposed by stomach tube to 25 metacercarial cysts of Echinostoma caproni per mouse. At 14 days post-exposure, mice were fed by stomach tube clorsulon (1000 mg/kg, 25 mg/kg, 500 mg/kg and 100 mg/kg) or rafoxanide (50 mg/kg, 25 mg/kg and 5 mg/kg) dissolved in dimethy lsulphoxide (DMSO) carrier and mebendazole (1000mg/kg and 500 mg/kg) or arprinocid (100 mg/kg and 50 mg/kg) suspended in a2:1 polyethylene glycol (PEG)/DMSO carrier. All drugs were obtained from Meerck In. (Rahway, New Jersey, USA) and only single dose regimes were used. Experimentally infected mice that served as controls received either DMSO or 2:1 PEG/DMSO carriers or were not given the carrier. Mice were necropsied 15v, 16, 18 and 20 days post-exposure to worms. Doses of 100 mg/kg of clorsulon and 50 mg/kg of rafoxanide were 100% effective in eliminating the echinostomes on day 1 post-administration of the anthelmintics. Mebendazole and arprinocid were ineffection in eliminating worms at 1 or 2 days post drug daministration.

C-banding has been performed on Dictyocaulus filaria using both original and modified techniques. The karyotype is reported based on C band observations. The existence of large heterochromatic blocks appears to be the cause of the low chiasmata frequency.

The long-term infection with Schistosoma mansoni (Gezira strain—Sudan) was studied in the Nile rat (Arvicanthis niloticus) to investigate the ‘self cure’ phenomenon. The results indicated that while a considerable number of worms and eggs were still recovered by week 28 post-infection, elimination of some of the worms occurred by week 20.

A new species of filarial worm, Paronchocerca mansoni, a cardiac parasite of Pica pica sericea (Gould) and Cyanopica cyana interposita Hartert, is reported from Peking, China. The thread-like adults of both species taper towards anterior and posterior ends. The cuticle exhibits superficial rugae, with multiple transverse striations underneath. The lipless mouth is surrounded by 4 paired submedian papillae and one lateral pair of amphids. The posterior end of the body is curved ventrad; the post-anal region is short. The male measures 17 mm. long and 0·14 mm. in diameter; the female, 35·8 mm. long by 0·23 mm. in diameter. In both sexes the anterior muscular oesophagus is short, the posterior glandular portion much longer. In the male, there are two pairs of pre-anal and one pair of post-anal papillae, likewise one pair of subterminal caudal papillae. There are neither caudal alae nor gubernaculum. The longer left spicule and the shorter right one have distinct species-characteristic morphological patterns. In the female, the vulva opens approximately 2·0 mm. from the anterior end. The microfilariae are sheathless; immature ones preponderate in heart blood; mature ones, present in heart blood and exclusively in circulating blood, measure 147 to 184 by 6·0 to 6·5 microns.

The feasibility of infecting laboratory rabbits experimentally with the ovine nematode Nematodirus spathiger was examined. Eight-week-old rabbits were dosed either with 5000 or with 17 000 third-stage larvae and killed on days 10, 21 or 42 post-infection. With the lower dose, 20 to 40% of the inoculum were recovered at necropsy. Similar values were recovered at necropsy. Similar values were observed with the 17 000 dose on days 10 and 21 post-infection, but on day 42 the worm population was residual (0·6%). With both dose levels, during the course of infection, the worm populations were mainly composed of fourth-stage larvae and worm egg excretion was low. N. spathiger mainly inhabited the proximal jejunum. The results were compared with N. spathiger infection in sheep to assess the usefulness of the rabbit as an experimental model for Nematodirus infection.

A new Indian species of Paraphelenchus is described and compared with P. basili Das, 1960, also from India, and with other known species of the genus.

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.

The isoenzymatic pattern of glucose 6-phosphate dehydrogenase (abbreviation G6PD) from Ascaris suum has been studied by vertical polyacrylamide gel (PAGE) and horizontal starch gel electrophoresis. After polyacrylamide gel electrophoresis, two stained zones could be identified. One corresponded to tetrazolium oxidase activity; since this zone was stained even in the absence of glucose 6-phosphate (G6P), non-specific staining could be detected. In the other zone of activity, seven regularly-spaced bands were identified by staining in the presence of G6P and NADP as substrates. By using starch gel electrophoresis, different electrophoretic patterns for G6PD have been observed in the muscular sac, intestine and reproductive system from A. suum. The existence of three different alleles of G6PD in the same individual suggests the existence of at least two genes for this enzyme.

Bilharziasis is unquestionably one of the major parasitic diseases of Southern Africa where both the urinary and intestinal forms occur. When it presents in the classical form, the diagnosis either from the clinical or laboratory viewpoint is seldom a major problem; but when, as so often happens, the presenting features have little in common with the accepted text-book descriptions of the disease, diagnosis becomes a matter of considerable difficulty.

1. The influence of diets having different protein values on the schistosomicidal effect of Ambilhar has been investigated in mice.

2. Mice placed on these diets throughout the period of infection and then treated, reached differently. Low protein diets produced fewer and smaller worms which were more susceptible to the drug.

3. Mice maintained on an adequate diet were shifted to diets of varying protein values a few days before treatment. In these, drug treatment was more satisfactory in animals fed the high protein regimen.

4. Female worms were more affected by drug treatment than the males.

Episthmium everardi sp.n. is described from a bird, Pitangus sulfuratus, from Trinidad, W.I. It differs from all other species in the genus in having 20 circumoral spines, each 20 to 22 long, and in the shape of the body, which is attenuated at its anterior end.

The difference in the final shape of the cyst of H. rostochiensis and H. schachtii is shown to be due to patterns of growth during cyst development. The greatest change of form takes place during the first 6 days for H. rostochiensis and the first 12 days for H. schachtii. The principal difference between the cyst shape in the two species is due to the greater increase in length in relation to breadth of the growing H. schachtii cyst. Premature tanning, due to environmental factors, is shown to affect final cyst form.

Part of the cestode fauna of ten hyraxes captured in Kenya was studied.

The species of hyrax were Procavia habessinica Hemprich and Ehrenberg and Heterohyrax syriacus Schreber.

One hundred and five cestodes were fixed, stained, mounted and examined. Descriptions of specimens, including measurements, are recorded in text and figures.

The normal ultrastructure of the abomasal fundic glands in sheep is described and compared with those of sheep infected experimentally with T. axei. Alterations were observed in mucous, mucous neck and zymogen cells and the results are compared with a similar study in normal and infected calves.

Thiamine pyrophosphatase and nucleoside diphosphatase have been studied histochemically in Raillietina (Raillietina) johri. Thiamine pyrophosphatase activity has been observed in the tegument, subtegumental muscle, subtegumental cells, medullary parenchyma, excretory canal and various reproductive structures like testes, ovary, vas deferens, spermatozoa and vitellaria. Eggs exhibit moderate enzyme activity. Various nucleoside diphosphates have been found to be hydrolyzed by thiamine pyrophosphatase. CaC12, MgC12 and MnC12 each activated the enzyme at a final concentration of 6 mM whereas cysteine, reduced glutathione and PCMB inhibited the enzyme activity at a final concentration of 10 mM, 10 mM and 20mM, respectively. KCN and NaF had no effect on the enzyme staining at concentration as high as 50 mM and 30 mM, respectively. Possible roles of the enzyme in the parasite have been discussed.