A biological study of the fauna of sewage-treatment plants was pursued by the writer for two years, from June 1927, thanks to the generosity of the Grocers' Company. The programme laid down included a qualitative and quantitative survey of the fauna and a collection of data on such physico-chemical factors as hydrogen ion concentration and oxygen requirement, with a view to seeking correlations between the two groups of phenomena.

Conventional methods for percutaneous infection of rats using third-stage juveniles of Nippostrongylus brasiliensis which have been artificially stimulated to exsheath lead to highly variable, and relatively poor, establishment in the intestine. A new system has been developed in which larvae applied to the skin still remain partially sheathed, as they would be in nature. Cultures of the freeliving stages of the parasite contain an annulus of clear, colourless polythene film to which some of the third-stage juveniles attach. Rats are infected with an individually counted, exact dose applied to the skin on polythene. Using this technique (‘EDT20Nb’), consistently high values for the mean proportion of the dose that becomes established have been obtained, along with a variance well below the normally accepted level ( from a total of 73 rats in 12 separate assays). In particular, the added component of variance between assays in this study was insignificant, so that the probability of quantitative agreement in replicate experiments based on the method is high. It is recommended for an experimental design in which small numbers of parasites can be used.

Capillaria cadovulvata was first described in 1945 by Madsen who found that it occurred commonly in the caeca of adult pheasants, and occasionally among partridges in Denmark. It is recorded now from a grey partridge Perdix perdix in England, where it had set up pathological changes which had been the cause of death. Madsen does not mention the presence of any lesions in association with this parasite. Though this is the first record of the species in England, it may be more common, for the species of Capillaria are not always easy to differentiate without recourse to fairly high magnification. In view of this, and because of its pathogenic nature, it seems worth while recording its occurrence and the lesions that may follow its presence.

Chromosomes of Acanthocephalus lucii (Muller, 1776) were observed using conventional staining techniques. The number of chromosomes in females and in their developing eggs (2n = 8) as well as the mean (La) and relative length (Lr) of the chromosomes and the localization of the centromere (Ic) were determined. Peculiarities in the behaviour of the chromosomes are also described.

Description: The specimens were collected from three Bartailed Godwits shot in the winters of 1956 and 1957. The description below applies mainly to the first infestation found. There are certain differences between the infestations which are noted later. There were up to 150 individuals in each infestation, varying from immature worms consisting of a scolex and a few proglottides to mature strobilas containing some 300 segments and reaching a length of 75 mm. The maximum breadth of the strobila is 1·8 mm. The onset of maturity is accompanied by a marked increase in the breadth of the strobila and the mature proglottides are broader than long.

The aims of this study were to determine the frequency of egg shedding (percentage of egg-positive faecal samples) and faecal egg counts (FEC) over 13 months in two different breeds of ewes, both pregnant and non-pregnant, in a mountainous region of central Mexico. Additionally, the effect of ivermectin and albendazole treatments on FEC reduction was recorded. The study also aimed to relate temperature and rainfall to FEC. The gastrointestinal nematode (GIN) third-stage larvae genera recovered from both faeces and grassland pastures in a temperate region were also assessed. Faecal samples were collected from ewes at monthly intervals for 13 months to investigate the FEC population of GIN larvae, their concentration and genera in grass samples collected from grazed and rested pastures. Egg-shedding frequency ranged from 0 to 92% and FEC from 0 to 12,000 eggs per g faeces (epg), with counts in Suffolk higher than in Dorset ewes. The identified genera were Haemonchus, Trichostrongylus, Teladorsagia, Cooperia, Oesophagostomum, Bunostomum, Nematodirus and Strongyloides. Haemonchus and Trichostrongylus were the most common genera. The number of L3 was higher in grazing lands than in those at rest. The highest FEC were recorded in the dry season due to peripartum, but the highest L3 counts were recorded in the rainy season. The coexistence of species of different geographical distributions at this site may be because there is a confluence of Nearctic and Neotropical geographic regions; thus, despite the temperate climate, tropical species can be found. Additionally, this study suggests that increasing temperatures could favour the presence of different tropical GIN species together with typical temperate-zone GIN species.

Experimental co-infections of juvenile and pre-adult Pseudosuccinea columella with Calicophoron daubneyi and Fasciola hepatica (five miracidia of each digenean per snail) were carried out to determine the aptitude of this lymnaeid to ensure complete larval development of the former parasite, the latter or both. Snails infected with F. hepatica were found in the two groups of juveniles, i.e. 1 and 2 mm at exposure, and the four groups of pre-adults, i.e. 3–6 mm. The highest frequency of F. hepatica, i.e. 37.3%, was noted in the 4 mm group. Low frequencies were noted for C. daubneyi and co-infections of both digeneans in the 3, 4 and 5 mm groups. Two other groups of P. columella, measuring 3 and 4 mm at exposure, were also constituted to study the characteristics of these co-infections. Compared to controls infected only with F. hepatica, the frequency of this digenean infection and the mean number of metacercariae were significantly lower in co-infected snails, while the patent period was significantly shorter. In snails harbouring C. daubneyi only or both digeneans, lower values were noted for prevalence, the patent period and the number of metacercariae. Pre-adult P. columella (3–5 mm in shell height at exposure) were able to sustain larval development of C. daubneyi if they were co-infected with the sequence C. daubneyi +F. hepatica. Low values noted for the prevalence of C. daubneyi infection and the number of metacercariae would be in favour of a still incomplete adaptation between the snail population and the miracidial isolate.

To date, 34 species of the genus Homalometron (Apocreadiidae) have been described; five of them in Mexican fresh or brackish water fish, whereas five have been reported as parasites of members of the fish family Gerreidae. While sampling wildlife vertebrates during a field course of parasitology at the Los Tuxtlas Biological Station (Instituto de Biología, Universidad Nacional Autónoma de México) in Veracruz, specimens of digeneans were collected from the intestine of the stripped mojarra, Eugerres plumeri in Sontecomapan Lagoon. Specimens were studied morphologically and molecularly, and we discovered that they represented a new species of Homalometron. The new species is morphologically like the other four congeners in having three pairs of well-developed oral papillae on the oral sucker: Homalometron elongatum; Homalometron lesliorum; Homalometron carapavae; and Homalometron papilliferum. Here, we describe the newly discovered species, increasing our understanding about the parasite diversity of brackish water fishes of Mexico.

Fourteen species of parasitic worms recovered from Adenota kob thomasi (P. L. Sclater) in Uganda, Africa, are recorded.

The morphology of two tapeworms, Moniezia monardi Fuhrmann, 1931 and Avitellina buechneri sp. nov., is described in detail and discussed.

The strobila of an adult tapeworm represents a continual gradient of developmental stages from immature to gravid proglottids. The purpose of this study was to determine if organogenesis (as measured by the develop mental gradient) in tapeworms within a single host and among different hosts occurred at the same rates. Rats were infected with Hymenolepis diminuta and the tapeworms were recovered 20 days post-infection. The total number of proglottids in each worm was determined, and five “benchmarks” of organogenesis were quantified. The data demonstrated that organogenesis in worms from a single host occurred at a relatively constant rate, but that rates in tapeworms from different hosts were different.

Several years ago, thanks to a grant obtained from the British Council, I spent a fortnight in Oxford at the Bureau of Animal Population. During this stay, I was able to trap some small mammals in a wood near Oxford. Among these mammals were several water shrews, Neomys fodiens Schr., which were brought to Belgium to be put in the collection of the State Entomological Research Station.

Three new species of the genus Opistholebes (Opistholebetidae Fukui, 1929) are described from the small intestine of the globefish, Tetraodon viridipunctatus (Gunther) in India.

A key to the species of the genus Opistholebes Nicoll, 1915 is given.

Abdominal angiostrongyliasis is caused by Angiostrongylus costaricensis, the definitive and intermediate hosts of which are wild rodents and terrestrial molluscs, respectively. Humans are accidental hosts and can be infected by ingesting the third-stage (infective) larvae (L3). It remains unclear whether the number of L3 inoculated is related to lesion severity. Our aim was to analyse histopathological alterations in Swiss mice infected with different doses of A. costaricensis. Thirty-two mice were randomly divided into four groups (n = 8/group): uninfected, control mice; mice infected with a low dose (five L3); mice infected with an intermediate dose (15 L3); and mice infected with a high dose (30 L3). The frequency of intestinal thrombi, splenitis, eggs/larvae, hepatic infarction and acute pancreatitis differed among the groups, the last being considered a significant finding. We conclude that different infective doses alter the histopathological aspects of the infection in Swiss mice, those aspects being more pronounced at medium and high doses, with no effect on the development of the disease. This experimental model shows that the parasite life cycle can be maintained in Swiss mice through the inoculation of a low dose (five L3).

The effects of various concentrations of copper sulphate were studied on in vitro encystment of Echinostoma caproni in a Locke's–artificial spring water (ASW) (1:1) medium. Cercariae were killed in 10,000 mg l−1 CuSO4 in Locke's–ASW (1:1) within 24 h and extruded cystogenous material to produce an abnormal cyst wall. The ‘emergency response’ of encystment to high concentrations of copper reported for Parorchis acanthus cercariae did not occur in E. caproni. Concentrations of 1000 mg l−1 and 100 mg l−1 CuSO4 in Locke's–ASW (1:1) also killed the cercariae without encystment by 48 h. A concentration of 10 mg l−1 CuSO4 in Locke's–ASW (1:1) allowed for normal in vitro encystment within 48 h and these cysts were capable of excystation in a trypsin–bile salts medium.

This study assessed the in vitro anthelmintic (AH) activity of methanol and acetone:water leaf extracts from Annona squamosa, A. muricata and A. reticulata against Haemonchus contortus eggs. The egg hatch test was used to determine the effective concentrations required to inhibit 50% of eggs hatching (EC50). The role of polyphenols on AH activity was measured through bioassays with and without polyvinylpolypyrrolidone (PVPP). Methanolic extracts mainly caused the death of eggs at the morula stage (ovicidal activity). Meanwhile, acetone:water extracts caused egg-hatching failure of developed larvae (larvae failing eclosion (LFE) activity). The lowest EC50 values against H. contortus eggs were observed for the methanolic extracts from A. reticulata and A. muricata (274.2 and 382.9 µg/ml, respectively). From the six extracts evaluated, the methanolic extracts of A. muricata, A. reticulata and A. squamosa showed the highest ovicidal activity, resulting in 98.9%, 92.8% and 95.1% egg mortality, respectively. When the methanolic extract of A. squamosa was incubated with PVPP, its AH activity increased. Similarly, when acetone:water extracts of A. muriata and A. reticulata were incubated with PVPP, their LFE activity increased. Alkaloids were only evident in methanolic extracts, irrespective of PVPP incubation. The presence of acetogenins was not observed. In conclusion, methanolic extracts obtained from leaves of A. muricata, A. reticulata and A. squamosa showed ovicidal activity affecting the morula of H. contortus eggs, with minor LFE activity. Meanwhile, acetone:water extracts showed mostly LFE activity, with a lower proportion of ovicidal activity.

Macrogyrodactylus congolensis (Prudhoe, 1957) is one of six species of Macrogyrodactylus, all of which are endemic to Africa. This monogenean is a host-specific ectoparasite of the African sharptooth catfish, Clarias gariepinus (Burchell, 1822). It attaches to the host with a posterior haptor armed with sclerites. The specific morphology of sclerites is taxonomically significant and usually studied using light microscopy. The aim of the present study was to confirm the identification of macrogyrodactylid parasites using classic morphology (light microscopy of glycerine ammonium picrate mounted specimens) and molecular techniques (18S rDNA, ITS rDNA and cytochrome oxidase subunit 1 (COI) mtDNA). Additionally, the sclerites were accurately described with a technique not previously used for the genus, whereby haptoral sclerites were isolated by removing the encapsulating soft tissue with a digestion buffer and studied with scanning electron microscopy (SEM). Morphology and morphometry of studied specimens corresponded to available data for M. congolensis, confirming the identity of the parasite. All previous descriptions were summarized in a table and discrepancies discussed. Molecular analysis also confirmed the specimens to be M. congolensis, but ITS rDNA and COI mtDNA was more reliable than 18S rDNA in this regard. The isolation of haptoral sclerites and their study using SEM was successful, resolving the morphology of all sclerites. This study provided the first reconstruction of the haptor of a Macrogyrodactylus species following SEM analysis, as well as the first mtDNA for M. congolensis. Further study of isolated haptoral sclerites of other macrogyrodactylids is required to determine the full benefits of studying their isolated sclerites.

The microscaphidiid Hexangium sigani Goto & Ozaki, 1929 was found in the intestine of Siganus rivulatus, a siganid fish permanently resident in a lagoon within the mangrove swamps on the Egyptian coast of the Gulf of Aqaba. Intra-molluscan stages of this trematode (mother sporocysts, rediae and cercariae) were found in the gonads and digestive gland of Nassarius pullus (Gastropoda: Nassariidae), a common snail in the same lagoon. Consequently, the life cycle of H. sigani was elucidated under natural conditions: eggs are directly ingested by the snail; mother sporocysts and rediae reach maturity 5–7 and 16–17 weeks post-infection; rediae contain 18–26 developing cercariae; fully developed cercariae are monostome, without penetration glands, emerge from the snail during the night 18–19 weeks post-infection and rapidly encyst on aquatic vegetation (there is no second intermediate host); encysted metacercariae are not progenetic; 2-day-old metacercariae encysted on filamentous algae fed to S. rivulatus developed into fully mature worms 5–6 weeks post-infection. The cycle was completed in about 24 weeks. The intra-molluscan stages are very similar to those of Dictyangium chelydrae Stunkard, 1943, the only described intra-molluscan stages of any microscaphidiid. However, they are also similar to those of the family Mesometridae. The present study of H. sigani describes the first complete microscaphidiid life cycle, and implicitly supports the phylogenetic relationship of this family with the Mesometridae inferred from molecular phylogenetic studies.

Worms belonging to the genus Ascaris occur occasionally in the small intestine of sheep and lambs and have been reported both in Europe and America. They have been considered by some to belong to a distinct species, namely Ascaris ovis Rudolphi, and by others to be identical with Ascaris lumbricoides Linnaeus. The question of their specific identity is an interesting one and could not be considered as definitely settled one way or the other and though possibly the majority of helmin-thologists would subscribe to the view that the species is A. lumbricoides (vide Ransom 1911, p.25, and Ransom and Foster 1920, p. 30), others hold a different view; in fact Neuveu-Lemaire (1923) has recently published a paper in which he describes a single specimen of Ascaris from a goat as Ascaris ovis.

Immature and mature stages of the sheep amphistome Cotylophoron cotylophorum have been analysed histochemically for their lipids. Excretory ducts of the immature worms were the common sites for the accumulation of neutral lipids (triglycerides) and phospholipids which showed very sparse distribution at the corresponding sites in the adult. Phospholipids and lipoproteins observed in the tegument of the adult could not be seen in the immature form. Intestinal caecae of both forms showed the presence of diffused and granular lipids which were relatively less in the immature. The possible physiological significance of these differences in the lipid contents of the immature and mature forms has been discussed.

Haemonchus similis Travassos, 1914 is recorded from Fiji for the first time. The third stage infective larva of H. similis is briefly described. Attention is drawn to the similarity of this larva to that of H. contortus of sheep and some of the implications are discussed.