The lymph system of three amphistome parasites from buffaloes, Gigantocotyle explanatum, Gastrothylax crumenifer and Srivastavaia indica was studied using light microscope histochemistry and electron microscopy. In each case the system comprised a single pair of main longitudinal vessels which gave rise to numerous sub-dividing lateral branches. Although the finer lymph channels associated with most internal systems, they did not penetrate the basement membrane of any organ. The lymph vessels were delimited by a unit membrane and separated from adjacent cells by interstitial material. The lymph fluid consisted of an amorphous proteinaceous, lipid-rich matrix, containing naked nuclei and granules of various sizes. Complexes of endoplasmic reticulum were frequently associated with the nuclei. No distinct Golgi bodies or mitochondria were evident. The granules noted throughout the lymph morphologically resembled autophagosomes and lysosomes. Autophagy within the lymph system presumably mobilizes amino acids for subsequent transport to tissues undergoing active protein synthesis. The lymph channels displayed an intimate relationship with the general parenchyma. In particular, numerous protrusions of lymph occurred into the cytoplasm of certain specialized parenchymal cells surrounding the pharynx. Within these ‘juxtapharyńigeal’ cells autophagic degradation of sequestered lymph cytoplasm apparently occurred. In the three species of amphistome studied, the lymph system appears to function in storage and mobilization of amino acids and possibly lipids. It may also serve to distribute other small molecules throughout the body. The detection of haemoglobin in the lymph system of G. crumenifer and S. indica, but not in Gigantocotyle explanatum, suggests a further role in oxygen storage and transport.

A vaccination trial in golden hamsters with UV-irradiated infective larvae of Ancylostoma ceylanicum was attempted. One oral vaccination of hamsters with 100 infective larvae irradiated by means of UV-tube (390 nm) at different time intervals induced the development of resistance. As the time exposure of irradiation was increased, there was a corresponding decrease in the subsequent worm establishment. A high level of protection afforded by larvae irradiated for 15min UV-exposure was recorded giving 99·0% and 95·0% worm reduction against the challenge doses of 100 and 1000 normal larvae respectively. There was no marked difference in worm establishment in hamsters vaccinated either orally or subcutaneously, followed by oral challenge. In the vaccinated hamsters, the manifestations of resistance at 15 min UV-exposure were shown by marked reduction in worm establishment and highly reduced epg in pellets with significantly higher blood haemoglobin levels compared with those given normal larvae as vaccine and challenge controls.

The BALB/C mouse infected with Brugia pahangi has been evaluated as a model for the selection of filaricidal compounds with activity against immature worms. Mice were infected by the intraperitoneal inoculation of 50 infective larvae and candidate compounds were administered by the intraperitoneal (i.p.), subcutaneous or oral route once daily from day 4 to day 8 post infection. Animals were examined on days 29 to 32 post infection. Variation in the larval recoveries from undrugged mice within and between experimental groups limited the value of drug assessments based upon percentage worm recoveries. The infection rate of undrugged mice was 85% over-all, range 60 to 100%. Using the infection rate of drugged v. undrugged animals as the criterion of activity the test has been evaluated with a series of standard nematicidal compounds.. Lcvamisolc and the benzimidazole carbamatcs, mebendazole, flubendazole and fenbendazole given i.p. at lOmg/kg daily were active in this screen whilst DEC, DEC-N-oxidc, ivcrmcctin, amoscanatc, mctrifonatc and suramin were inactive at the dosages tested. No retardation of growth or morphological abnormalities were observed in worms from the drugged mice.

Inbred jirds (Meriones unguiculatus) were divided into three groups; each animal in two of the groups was infected with 30 infective larvae (L3) of Litomosoides carinii. When these infections were patent, the jirds of one of the two infected groups plus those of the third group were injected with 30 L3 L. carinii each. All animals were killed either on day 14 or 24 after the second infection for the recovery, enumeration and measurement of all worms and developing larvae. Challenge larvae were stunted (smaller) and fewer than control larvae. Additionally, fewer challenge larva were recovered on day 14 than on day 24, indicating that migration to the pleural cavity was retarded.

Oxidative deamination of various biogcnic monoamines by Ascaridia galli monoaminc oxidase (MAO) was blocked by different mammalian MAO inhibitors, namely, iproniazid, trans-PcP, nialamide and pargyline and the blockade was observed to be time as well as concentration dependent. The binding of inhibitors with chick ascarid MAO was of the irreversible type and the nature of the inhibition was competitive. Pargyline showed lowest I50 (8µM) and K1 (12µM) values. Chlorgyline and deprenyl at 100µM concentration inhibited MAO by about 60 and 40% respectively, indicating the presence of both type A and type B MAO in A. galli.

The susceptibility of various mammals to infection with Fasciolopsis buski has been studied. Mice, rats, monkeys and dogs were completely refractory. Guinea-pigs were only partially susceptible. However, young rabbits (6 to 8 weeks old) were found to be susceptible and can be used as an animal model for experimental work on this parasite.

The immunological responses in hamsters during treatment with mebendazole against Ancylostoma ceylanicum are studied. Indirect haemagglutination (IHA) counterimmunoelectrophoresis (CIEP), passive cutaneous anaphylaxis (PCA), foot pad swelling for immediate (ITH) and delayed (DTH) types of hypersensitivities were employed for measuring the responses. Serum antibody which was 1:32 before treatment increased to the maximim of 1:512 (control 1:128) on the 10th day and it declined subsequently. The CIEP test was positive for 10 days and then became negative. The PCA test was positive throughout the observation period both in the treated and untreated groups. Foot pad swelling for ITH and DTH responses were comparatively more prominent than in the untreated control up to the 20th day and then both decreased simultaneously. The immunological responses remained prominent for a longer period and decreased more slowly in the untreated control group.

Magnacercous cercariae with heavily pigmented tails and possessing a pair of eyespots and seven pairs of penetration glands, some of which are para vesicular, were found to develop in the prosobranch gastropod, Cerithium coralium collected from a brackish water locality at Bheemunipatnam, A. P. India. The cercariae developed into metacercariae of Galactosomum ussuriense in the viscera of the fish Therapon jarbua. Successive stages in the development of metacercaria from the cercaria were followed. Natural infections with metacercariae were found in T. jarbua, Valamugil cunnesius and Megalops cyprinoides. The definitive host of G. ussuriense in the present area of investigation is still not known. This represents the second account of part of a life-cycle in the genus Galactosomum.

Mastomys natalensis wcrc infected percutancously with 250 cercariae of Schistosoma mansoni and treated effectively with 5 x 50 mg amoscanatc/kg body-weight 12–16 (1), 28–32 (10,56–60 (111) and 101–105 days p.1. (IV) respectively. Levels of reaginic antibodies (RAb) and homocytotropic IgG antibodies (GAb) were assessed by passive cutaneous anaphylaxis tests (PCA) and compared with those in infected, untreated animals. In untreated animals RAb were first detected in the 6th week p.i. Maximum titres around 1:80 were reached after 100 days. High levels persisted until the end of the experiment 185 days p.i. RAb did not develop after treatment I. After treatmcnt 11 only low PCA titres occurred. After treatment 111 the time course was similar to the controls but levels were reduced. Treatment IV did not interfere with the occurrence of specific RAb.

In the case of GAb, independent of any treatment, after a first peak of PCA titres in the 5th week either a negative pattern or only very low titres were found in week 7. In untreated infected Mastomys GAb levels increased thereafter to maximum titres of about 1:80 at day 70. Later than 100 days p.i. relatively constant titres were observed. The second rise of antibody levels did not occur after early treatment. After treatment 11 only low transient titres developed. Animals treated in the early patcncy (III) showed reduced PCA titres and were negative at the end of the observation period. Treatment given 101 to 105 days pi. rather enhanced the development of GAb.

The comparative efficiency of the percutaneous and per-oral routes of infection was studied in goats experimentally infected with Schistosoma bovis. The heaviest infection was obtained by the percutaneous route, but a relatively high parasite load was also achieved by the per-oral route, i.e., where goats were allowed to drink a cercarial suspension, volume of 0·9 to 1·7 litre per animal. Studies using radio-isotopically labelled cercariae were designed to clarify the cercarial penetration sites following uptake by drinking. Radioactivity could be demonstrated in the outer lips, buccal cavity, oesophagus and the reticulum, omasum and rumen. Highest counts were recorded in outer lips, reticulum and rumen constituting 41·2, 22·1 and 20·6%, respectively, of total radioactivity recovered. It is concluded that the per-oral infection route may play a larger role than hitherto anticipated in infection of ruminants, and possibly also in other mammals, with schistosomes. The epidemiological implications of the present findings are discussed.

Following chronic retinol (vitamin A) deprivation leading to exhaustion of liver vitamin A reserves below 50 I.U. per liver hamsters were fed diets either deficient in (“Rd”: 250 I.U.A/kg in experiment I, 1000 I.U.A/kg in experiment II) or enriched with retinol (“Rw”: 10000 I.U.A/kg in experiment I and II). After 4 weeks some of the animals (36 in experiment I, 30 in II) were infected with 150 3rd-stage larvae of D. viteae, while clean animals were kept as controls. The retinol status, the immune response (indirect fluorescent antibody test: IFAT) and parasitological parameters were examined up to 8 (experiment I) and 12 weeks (experiment II) post infection (p.i.). Rd hamsters had levelling off of weight gain or weight loss, severely deficient retinol levels in serum and liver, and high mortality. Weight gain was less in infected than in uninfected hamsters, and the capacity of infected Rw animals to restore liver retinol was significantly lower than that of uninfected Rw animals. IFAT titres were similar in Rd and in Rw animals, but microfilaraemia was significantly enhanced at 8 and 10·5 weeks p.i. in Rd hamsters. While the number of worms recovered from Rd and Rw hamsters was similar, there was a significant increase in the ratio of female to male worms in Rd hamsters. Rd hamsters in experiment I produced 3·3 times the worm mass per 100 g body-weight than Rw hamsters. Also, the average mass per female worm was significantly higher in Rd than in Rw hamsters, and this parameter was negatively correlated with the liver retinol concentration in experiment I (r=−0·89). Retinol deficiency has a marked effect on growth and fertility of D. viteae in hamsters.

Flubendazole given orally at 50mg kg to mice inoculated with 50, 250 or 500 larvae of Angiostrongylus cantonensis showed almost complete larvicidal effect, irrespective of the worm burden.

The anthelmintic effects of anti-tapeworm drugs, bithionol, paromomycin sulphate, flubendazole and mebendazole on immature and mature Hymenolepis nana in mice were compared. Immature worms were not affected by paromomycin sulphate or flubendazole administered for 12 consecutive days (days one to 12 after infection) at lOOmg/kg/day but 48% and 100% of H. nana were eliminated from mice by bithionol and mebendazole respectively, at the same dosage regimen. Bithionol, paromomycin sulphate, flubendazole and mebendazole given at 100 mg/kg/day for five consecutive days (days 12 to 16 after infection) eliminated 32%, 29%, 36% and 100% of mature worms respectively. 10 and 20 mg of mebendazole/kg/day for five consecutive days (days 12 to 16 after infection) had little effect on mature worms whereas 50 and 100 mg/kg/day for the same period eliminated 99% and 100% of mature worms, respectively. ED50 of mebendazole in the elimination of mature H. nana was 14 or 15 mg/kg/day for five days from the reduction in dry weight or in number of worms recovered respectively. The effects of mebendazole given 2 to 4 days, 8 to 10 days or 13 to 15 days after infection at lOOmg/kg/day were compared. Very low, if any, activity of the drug given 2 to 4 days after infection was seen, whereas the drug given 8 to 10 days or 13 to 15 days after infection eliminated 84% and 86% of H. nana respectively.

The in vivo efficacy and ultrastructural effects of mitomycin C were determined against alveolar hydatid disease in experimentally infected animals and compared to mebendazole treatment. Mitomycin C inhibited tne mean cyst mass of treated versus control animals by 84·1% which was statistically significant at the α=0·01 level. Mebendazole given daily inhibited the mean cyst mass by 80·1%, while mebendazole administration on the same treatment schedule as that used for mitomycin C inhibited the mean cyst mass by 74·4% Ultrastructurally, mitomycin C was not observed to affect the tegumental microtriches (microvilli) or ine microtubular system. However, an increase in the number and accumulation of round to oval electronaense vesicles was observed within the subtegument. These inclusion bodies became vacuolated, osequently degenerated, and formed myelin-like figures. Mitomycin C, like mebendazole, was only cystistatic in its effects on the cyst stage of Echinococcus multilocularis as evidenced by the growth of treated cyst material following inoculation into helminth-free animals.

Time lapse video micro recording techniques have been used to investigate the development and eclosion of Ancylostoma ceylanicum and A. tubaeforme eggs under a range of temperature and osmotic conditions. Over the range 15 to 35°C increasing temperature resulted in decreased development time, the hyperbolic form of the curve being similar to that found by other workers. The adoption of a developmental parameter to mark the start of timing provided more reproducible results than previously reported. Osmotic stress in the range 0·600 mOsM/kg provided by a number of inorganic salts and organic sugars increased hatching time but did not greatly reduce the percentage that hatched. There was no correlation between the ionic composition of the solution and its effect on the eggs. Solutions of EDTA, carbonates and iodides markedly reduced hatching. Behavioural studies of the pre-hatched larvae suggested that the eggs were permeable and susceptible to osmotic and ionic changes early in their development and well before they were ready to hatch. No appreciable differences were found between the two species of hookworm investigated.

Laboratory investigations were designed to study the influence of temperature, pH and oxygen tension on the growth of Arthrobotrys oligospora, a nematode-trapping microfungus. Experiments were performed to evaluate the potential role of A. oligospora in destroying third-stage larvae of Cooperia spp. on agar plates and in cattle faeces. The fungus had a growth rate optimum at 23°ree;C and pII 6. Anaerobic cultivation for 23 hours at 23°ree;C and 39°ree;C inhibited fungal growth, but it did not destroy the fungus, which regained growth upon a subsequent shift to aerobic conditions at 23°ree;C. Under experimental conditions in petri-dishes containing agar, the nematode-trapping efficiency of the fungus was striking in that 100% of a population of third-stage larvae of Cooperia spp. was captured within three days of the experiment. The trapping efficiency in faeces was shown to depend upon the inoculation level. At a concentration of approximately 2500 conidia per g faeces, 99% of the larvae were destroyed. The possibilities of using nematode-trapping fungi in controlling animal-parasitic nematodes arc discussed.

The migration and distribution of Ancylostoma caninum larvae in the tissues of chickens, infected orally with 1,000 larvae, were studied. Larval yield at necropsy from different organs after digestion with artificial gastric juice revealed a 62·9% recovery four hours after inoculation, followed by a sharp decline to 5·4% at 72 hours. Larvae were found in the heart within four hours, the lungs within eight hours and the liver within 12 to 18 hours but no larvae were recovered from the spleen, kidney or brain. Migration in the muscles of head, neck, thorax and abdomen was detected at 12 hours and was maximal at 36 hours. The establishment of patent infection in the definitive host was studied by feeding infected chicks to hookworm-free pups (one chick/pup) 48 hours, 7 days and 14 days after infection. The mean worm burden at necropsy was highest (15) in the pups fed with chicks 48 hours after infection and was three and nil in the other groups respectively.

Chemotaxonomic patterns in the distribution of amino acids of Hymenolepis palmarum (Jouri, 1956) and other hymenolepidids revealed the common presence of β-aminoisobutyric acid, lysine, phcnylalaninc and tyrosine but 3,4 dihydroxyphenylalanine and norleucine were exclusive to H. palmarum. Both qualitative and quantitative differences in amino acids have been recorded.