Acetylcholine is the major endogenous classical neurotransmitter in the central and peripheral nervous system of trematodes and mammals. This study investigates the effects of cholinergic drugs on muscle activity in the amphistome, Gastrothylax crumenifer. In the present investigation, acetylcholine (10− 7–10− 3 m) did not produce any marked effect, whereas carbachol (10− 7–10− 3 m) elicited a concentration-dependent decrease in amplitude, baseline tension and frequency of contractions as compared to the control. Nicotine (10− 7–10− 3 m) produced a significant decrease in the amplitude and frequency of spontaneous muscular activity in a concentration-dependent manner, as compared to control amplitude (0.5 ± 0.01 g) and frequency (58.5 ± 3.45 per 5 min). However, the baseline tension was also reduced significantly by 10− 3 m nicotine. Atropine (10− 7–10− 3 m) elicited a concentration-dependent increase in amplitude and baseline tension, whereas there was no significant effect on the frequency of the spontaneous contractions of rumen flukes. These observations indicate that G. crumenifer has an inhibitory cholinergic system and that the inhibitory activity of nicotine is more pronounced than that of carbachol or acetylcholine.

The complete gene encoding an immunodominant antigen of Dirofilaria immitis was isolated from a Charomid 9–36 genomic DNA library. This genomic DNA clone termed ‘Dg2’ was characterized by restriction mapping, DNA sequencing of the 5′ flanking region, the exon/intron boundaries and the polyadenylation addition site. The Dg2 with 4872 bp in length consisted of five exons interspersed with four introns. These exons reveal a single open reading frame followed by a long 3′ non-coding region of 1383 bp. The open reading frame of 969 bp encodes a polypeptide of 322 amino acids with a molecular weight of 34,400. The ATG translation initiation codon starts 22 nucleotides downstream from the 5′ end of the first exon. The polyadenylation signal sequence, AATAAA, is located at the 3′ end of the last exon. The transcription initiation site was determined by primer extension technique. S1 nuclease mapping analysis demonstrated that the primary transcript derived from Dg2 is synthesized in microfilariae but not in male or female adult worms. The result suggests that the stage-specific expression of Dg2 is regulated at the level of primary transcript.

A 30 kDa antigen was characterized as a hydrophobic polypeptide containing 16 amino acids and evaluated as a potential candidate vaccine against infection by Schistosoma mansoni. CD1 albino mice immunized at 0, 14, and 21 days with 25 or 50 μg of the 30 kDa antigen per mouse with and without alum developed high levels of IgG antibodies (predominantly IgG2a and IgG2b isotypes). When immunized mice were infected with 200 S. mansoni cercariae, the highest protection levels (61% and 65% reduction in worm burden in two separate experiments) were obtained using the 50-μg antigen without alum adjuvant. The granuloma size decreased to 10%, a non-significant level in mice immunized using alum adjuvant. The results demonstrate the ability of the 30 kDa antigen with and without alum adjuvant to protect mice against S. mansoni infection.

A total dose of 30 gm. of phenothiazine, given as tablets in one dose of 15 gm. and three of 5 gm. to three goats and six sheep known to be worm-free, had no effect on the weights of the animals in comparison with equal numbers of worm-free controls, over a period of 15 weeks from the first dose.

It is concluded that weights can validly be used as a criterion of anthelmintic efficacy; they not only constitute an obvious economic criterion, but also are statistically more sensitive than egg-counts when subjected to analysis of covariance.

The earlier work of this Institute on phenothiazine in lambs (Peters et al, 1941; J. Leiper et al, 1941) using egg-counts, worm-counts, and lamb-weights as criteria of anthelmintic efficacy, has revealed conflicting results as between one criterion and another. Thus, the lowest dosage rate used (0·15 gm. per Kg.) led to a reduction in the egg-count, whilst even the highest rate (1 gm. per Kg.) led to no reduction in the worm-count: by an irony of chance the worm-counts were lowest in the untreated controls in both experiments. In the first experiment weights were not affected by the drug, and in the second the only significant effect was a set-back in those lambs given tablets. Numerous other workers have reported increased weights due to the drug, in long-term experiments; ours were too short in duration to show such increases, yet the danger of reinfestation precluded any extension of the time, the lambs being kept outside on infective pastures. The most obvious explanation of the egg- and worm-count results appears to be that the drug has a temporary inhibiting effect on egg-laying, which would presumably return to normal in a few weeks; but here again a prolonged experiment increases the liability to reinfestation.

These being the relevant circumstances, the present experiment was designed to take account of them in the following ways. In the first place the lambs were kept inside throughout the experiment, their stalls being cleaned out thoroughly twice a week to obviate reinfestation.

The development of Schistosoma margrebowiei in hamsters, mice and gerbils has been studied following infection by cercariae obtained from laboratory-infected Bulinus natalensis. The rate is compared with that of other schistosome spp. and found to be very fast. In vitro development was slower and did not proceed beyond the closed-gut stage.

In an experiment previously reported (1941) we were able to show little anthelmintic effect against the gastro-intestinal nematodes of sheep after using phenothiazine powder in single doses up to 0·3 gm. per Kg. body weight. In view of our experience and its contrast with that of many" other workers, we felt it desirable to test a much larger dose, to compare it with another brand of the drug, and (because of the very large variation in worm burden from lamb to lamb) to use not less than four lambs in each treatment group.

Accordingly, 12 lambs from a flock known to be naturally infested were purchased last November, and these were divided at random into three groups as follows: A, untreated controls; B, given compressed 5 gm. tablets of phenothiazine (recently placed on the market by a well-known firm) at the rate of 5 gm. per 5 Kg. body weight; and C, given phenothiazine powder in water as a drench, at the same dosage rate, with the addition to each dose of 1 gm. sodium glycocholate as a wetting agent. This powder was from the same batch as that used in our previous experiment. In each case the full amount was given as a single dose.

The same three criteria of efficacy were used as before: three eggcountings and lamb-weighings before and after treatment, and post mortem worm-counts. Eggs were counted by the same modified McMaster technique, the individual counts representing the eggs in 0·005 gm. of faeces, but on this occasion only three cells were counted per sheep per day.

Androgens have been shown to exert a cysticidal effect upon Taenia crassiceps, an experimental model of cysticercosis. To further inquire into this matter, the Taenia crassiceps model was used to evaluate the expression of several proteins after testosterone (T4) and dihydrotestosterone (DHT) in vitro treatment. Under 2-D proteomic maps, parasite extracts were resolved into approximately 130 proteins distributed in a molecular weight range of 10–250 kDa and isoelectrical point range of 3–10. The resultant proteomic pattern was analysed, and significant changes were observed in response to T4 and DHT. Based on our experience with electrophoretic patterns and proteomic maps of cytoskeletal proteins, alteration in the expression of isoforms of actin, tubulin and paramyosin and of other proteins was assessed. Considering that androgens may exert their biological activity in taeniids through the non-specific progesterone receptor membrane component (PGRMC), we harnessed bioinformatics to propose the identity of androgen-regulated proteins and establish their hypothetical physiological role in the parasites. These analyses yield a possible explanation of how androgens exert their cysticidal effects through changes in the expression of proteins involved in cytoskeletal rearrangement, dynamic vesicular traffic and transduction of intracellular signals.

It has been known for many years that the stem eelworm, Anguillulina dipsaci, can be carried in or upon the seeds of a number of different plants. Kühn (1858) originally found the parasite in the diseased seed heads and seed of the teasel or fuller's thistle. Bos (1888) discovered the worms in the flowers of the onion, Allium Cepa, and found in one case 3 per cent. of the seeds were infected. Godfrey (1924) found infestations of the parasite in the flower heads of cat's-ear, Hypochoeris radicata, and dandelion, Taraxacum officinale, and discovered in both hosts that living worms occurred within the seed coats. He also obtained diseased seedlings by sowing infected seed of both hosts. Hodson (1926) reported the occurrence of the parasite in quiescent form beneath the pales of oats harvested from fields badly affected with “tulip root” and obtained small numbers of infected seedlings by sowing such seed. The number of such cases was, however, so small that he considered their occurrence might be accidental. Robertson (1928) investigating “tulip root” in oats, found the parasite in the panicles of affected plants giving rise to abortive flowers. In a number of oat grains from distorted panicles he found small numbers of the parasite between the glumes and pales and between the pales and the kernel and was able to show that after storage for a few months the worms could be revived by soaking the grains in water. He did not pursue his studies to the extent of obtaining diseased seedlings from such infected seed. Cobb (1929) found samples of seed of red clover and lucerne, as cleaned by commercial processes, yielded the parasite in a living condition when soaked in water.

The specimens used for this study were obtained from two collections of helminths sent to the Commonwealth Institute of Helminthology for identification. The first was made by Dr. R. Sachs in his survey of parasitic infestation of wild herbivores in the Serengeti region, Tanzania and the second by Dr. L. D. Fay in a veterinary survey of game animals in Kenya.

The susceptibility of rats to Hymenolepis nana (Cestoda) and the chemotherapeutic response of anti-cestode drugs was studied during egg-induced and cysticercoid-induced infections. In cysticercoid-induced infection, the percentage of infected animals and the number of mature worms were significantly more than in egg-induced infection. The former mode of transmission required more drug to clear the parasites. These differences have been discussed on the basis of immunity engendered in the definitive host by the developing larvae.

A new species of amphistome cercaria from Planorbis exustus in Cachar District, Assam, is described.

Feeding experiments with the encysted cercariae to two calves and a pig proved negative.

Trichinosis is a disease which is characterised by profound absolute and relative variations in the leucocyte ratios of the circulating blood, more particularly a marked eosinophilia, and in moderate cases, concurrent neutrophilia (van Someren, 1938). It is obvious that these changes in the peripheral blood are the outcome of disturbances in the development of the precursor cells of the haemopoietic system, especially in the bone marrow; the lymphocytogenic tissue in the spleen and lymph glands does not appear to be so markedly activated, except in very severe cases or late in the course of the disease.

Bisphosphonates have been proposed as pharmacological agents against parasite and cancer cell growth. The effect of these compounds on helminthic cell viability and acellular compartment morphology, however, has not yet been studied. The effects of different types of bisphosphonates, namely etidronate (EHDP), pamidronate (APD), alendronate (ABP), ibandronate (IB) and olpadronate (OPD), and their interaction with amiloride, 1,25-dihydroxycholecalciferol (D3) and proline were evaluated on a cell line derived from bovine Echinococcus granulousus protoscoleces (EGPE) that forms cystic colonies in agarose. The EGPE cell line allowed testing the effect of bisphosphonates alone and in association with other compounds that could modulate calcium apposition/deposition, and were useful in measuring the impact of these compounds on cell growth, cystic colony formation and calcium storage. Decreased cell growth and cystic colony formation were found with EHDP, IB and OPD, and increased calcium storage with EHDP only. Calcium storage in EGPE cells appeared to be sensitive to the effect of amiloride, D3 and proline. Proline decreased calcium storage and increased colony formation. Changes in calcium storage may be associated with degenerative changes of the cysts, as shown in the in vitro colony model and linked to an adenosine triphosphate (ATP) decrease. In conclusion, bisphosphonates could be suitable tempering drugs to treat cestode infections.

The structure of the normal coenurus of M. glomeratus is described and some observations have been made on its powers of budding and vegetative growth and reproduction. It is suggested that only a small area of the cyst has the power of growth and development and that budding and daughter cyst formation is an action which attempts to stave off old age and sterility. It has been found possible to cause new growths and infections by the transplantation of certain elements to new hosts. Some remarks are made on the occurrence of abnormalities in a coenurus cyst.

Clinostomidae is a diverse family of digenean parasitizing fish-eating birds as adults and fishes as metacercariae. The species composition, within the genus Clinostomum has been steadily increasing in recent years. In Argentina, four named species of Clinostomum have been documented, accompanied by four metacercariae representing distinct genetic lineages whose adults have not been identified. This study focused on examining clinostomids in three fish species – Australoheros scitulus (ASI), Cichlasoma dimerus (CDIM), and Pimelodella laticeps (PLA) – at various localities in Argentina. We conducted both morphological and molecular characterizations of the Clinostomum metacercariae collected from these fish species. Molecular phylogenetic analyses using COI mtDNA were performed to determine the placement of these metacercariae within the clinostomid phylogenetic tree. Clinostomum ASC represents a distinct lineage, morphologically distinguishable from other sequenced metacercariae due to its body shape (widest anteriorly and becoming slender towards the posterior end); this lineage was found to be closely related to C. caffarae. While Clinostomum CDIM and Clinostomum PLA exhibited morphological differences, they clustered together genetically with metacercariae reported in previous studies as Clinostomum L3 and Clinostomum CVI. This outcome, coupled with a low genetic distance (0 to 3%), suggests that they are conspecific with metacercariae found in fish across Mexico, Costa Rica, and Argentina. In light of the extensive diversity of fish species in Argentine freshwater ecosystems (over 500 species), and considering the relatively constrained extent of prior investigations, the anticipation of unearthing additional Clinostomum species or lineages is plausible.

Parasitic ‘turbellarians’ are known from various animals such as echinoderms, crustaceans, annelids, bivalve and gastropod molluscs. So far, however, no ‘turbellarians’ have been reported from cephalopods. In this paper we report a parasitic ‘turbellarian’ from the giant Antarctic octopus, Megaleledone setebos. We dissected two specimens of M. setebos caught in the Ross Sea (Antarctica) and found numerous worms in their intestine and liver. The worms were spherical or oblong and had two morphologically different poles. The frontal pole bears a small conical protrusion containing large elongated pear-shaped frontal glands and large polygonal cells. The ducts of the frontal glands open terminally to form the frontal organ. The caudal pole has an opening shaped as a folded tube connected by the genital pore with a common genital atrium, which continues into a canal with a muscular sheath. The worms were identified as ‘turbellarians’ from the family Notenteridae (Fecampiida). This family contains only one species, Notentera ivanovi, reported from the gut of a polychaete at the White Sea. The worms that we found in the gastrointestinal tract of the octopuses were morphologically similar to N. ivanovi but differed from it in several important respects. Phylogenetic analysis based on 28S rDNA gene showed that the newly found worm clustered together with other fecampiids in a highly supported clade and was closely related to N. ivanovi. On the basis of these morphological and molecular data, we described a new species, Octopoxenus antarcticus gen. nov., sp. nov. (Fecampiida: Notenteridae), establishing a new genus to accommodate it and provided an updated diagnosis of the family Notenteridae. This is the first report of a parasitic ‘turbellarian’ from a cephalopod mollusc.

Climate change is expected to affect parasitic nematodes and hence possibly parasite–host dynamics and may have far-reaching consequences for animal health, livestock production, and ecosystem functioning. However, there has been no recent overview of current knowledge to identify how studies could contribute to a better understanding of terrestrial parasitic nematodes under changing climates. Here we screened almost 1,400 papers to review 57 experimental studies on the effects of temperature and moisture on hatching, development, survival, and behaviour of the free-living stages of terrestrial parasitic nematodes with a direct life cycle in birds and terrestrial mammals. Two major knowledge gaps are apparent. First, research should study the temperature dependency curves for hatching, development, and survival under various moisture treatments to test the interactive effect of temperature and moisture. Second, we specifically advocate for more studies that investigate how temperature, and its interaction with moisture, affect both vertical and horizontal movement of parasitic nematodes to understand infection risks. Overall, we advocate for more field experiments that test environmental effects on life-history traits and behaviour of parasitic nematodes in their free-living stages under natural and realistic circumstances. We also encourage studies to expand the range of used hosts and parasitic nematodes because 66% of results described in the available studies use sheep and cattle as hosts and 32% involve just three nematode species. This new comprehension brings attention to understudied abiotic impacts on terrestrial parasitic nematodes and will have broader implications for livestock management, wildlife conservation, and ecosystem functioning in a rapidly warming climate.

Podocotyle is a genus of marine opecoelid digeneans that parasitize a wide variety of fish as adults. We present the first phylogenetic analysis of several Podocotyle isolates using nuclear 28S rDNA and mitochondrial cox1 DNA regions. New sequences were obtained for Podocotyle specimens from fish caught in the Sea of Okhotsk and the White Sea. Based on morphological and molecular data, eight Podocotyle lineages of species rank were revealed. However, this diversity is poorly formalized within the current taxonomic model of the genus. As a result, we identified Podocotyle cf. angulata, Podocotyle cf. atomon, Podocotyle cf. reflexa, Podocotyle atomon of Sokolov et al., 2019, Podocotyle sp. of Denisova et al., 2023, Podocotyle sp. 1, Podocotyle sp. 2 and Podocotyle sp. 3. We also highlight the unresolved question of the life cycles of representatives of Podocotyle whose intramolluscan stages parasitize the intertidal snails Littorina spp.

Nematoda of the genus Echinocephalus Molin, 1858 include species from the Gnathostomatidae family, the adult stages of which parasitize the stomach and spiral intestine of elasmobranchs as their final hosts. In the present study, we describe Echinocephalus spinosus n. sp. found parasitizing the spiral valve of the freshwater stingray Potamotrygon motoro from the Tapajós River, in the Amazon Basin, in the state of Pará, Brazil. In the study we performed morphological (light and scanning electron microscopy) and molecular (small subunit ribosomal ribonucleic acid (SSU rDNA) and mitochondrial cytochrome c oxidase I sequencing) analyses. E. spinosus n. sp. is only the second species of the Echinocephalus genus described from a strictly freshwater environment. The SSU rDNA based phylogenetic analyses showed Echinocephalus clade as a sister lineage of Gnathostoma, and that the new species arises as a sister to Echinocephalus cf. pseudouncinatus. Time-calibrated phylogenetic analysis revealed that the origin of the freshwater Echinocephalus coincides with the recently proposed origin of the freshwater host potamotrygonin stingray, namely the late Oligocene to early Miocene, when the western Amazon was dominated by the Pebas wetlands, an epicontinental marine/freshwater system.