A controlled study was carried out to determine the effect of some known anti-filarial drugs on the pattern of emergence of Onchoccrca volvulus microfilariae from skin snips into saline. The results show that before treatment, 81·7 to 92·1% of microfilariae emerge in all the groups within 24 hours. The differences between the groups were not significant. After treatment with oral diethylcarbamazine, metrifonate and topical diethylcarbamazine (DEC) the percentage of microfilariae emerging from the snips dropped significantly to 48·4,560 and 60·1 respectively, whereas no significant change occurred following treatment with levamisole (88·1%) and yeast tablets (89·1%). A pair-wise comparison of the post-treatment microfilarial emergence in all the groups showed statistically significant differences when (i) oral DEC is compared to levamisole, topical DEC and yeast, (ii) metrifonate is compared to levamisole and yeast and (iii) topical DEC is compared to yeast. It is suggested that microfilariae which fail to emerge from snips after treatment are those that have been killed or paralysed by the action of the drugs. The study has thus established that drug action in vivo is one of the factors which affects the proportion of microfilariae which emerge from skin snips and provides an additional parameter for measuring the antimicrofilarial potential of drugs in clinical chemotherapeutic trials.

The biochemical composition of the metacercariae of Clinostomum complanatum is: free glucose 0·516% of wet wt (2·14% of dry wt), glycogen 4·39% of wet wt (18·30% of dry wt), protein 8·7% of wet wt (36·23% of dry wt), lipids 8·64% of wet wt (35·96% of dry wt), RNA 0·08% of wet wt (0·335% of dry wt) and DNA 0·035% of wet wt (0·145% of dry wt). The pattern of glucose uptake, glucose leakage and effect of starvation on the glycogen content is similar to that reported for adult digeneans. Lactic and pyruvic acids (1·478 and 0·019μimol/g wet wt/h respectively) were found in the incubates, suggesting the presence of an active carbohydrate metabolism. Protein and lipid metabolism are also discussed briefly.

1. Investigations were made of the effect of various procedures in raising or lowering the microfilaria count of Pacific type Wuchereria bancrofti in the peripheral blood.

2. Raising the body temperature in the early morning was followed by a moderate fall in the counts. Breathing increased oxygen, or reduced oxygen (hypoxia) or increased carbon dioxide, or the ingestion of sodium bicarbonate produced no consistent and significant changes in the count. Ingestion of glucose (in one volunteer) was followed by a small rise in the count. Muscular exercise was followed by a fall in the count, which is interpreted as probably being a response to a lower concentration of oxygen in the venous blood returning to the lung.

3. It has not been possible to identify the physiological components of the circadian rhythm of the human body which entrain the cycle of these microfilariae. Attempts to obtain evidence incriminating the stimuli described above have been unsuccessful.

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.

Plots of pastureland with well grown herbage provided a more favourable environment for the survival and development of the free-living stages of Oesophagostomum dentatum in faeces during warm dry weather than did plots with short herbage. This was because well grown herbage gave better protection against the unfavourable effects of dryness than did short herbage. There was no significant difference between the plots during cool wet weather.

The effect of oxyclozanide, hexachlorophene, nitroxynil, rafoxanide and diamphenethide on malate dehydrogenase activity of homogenates of Fasciola gigantica, Fasciolopsis buski and Paramphistomum explanatum was investigated. The ratio of oxaloacetate reduction to malate oxidation in homogenates of Fasciola gigantica, Fasciolopsis buski and P. explanatum was 4·5:1, 3·6:1 and 5·2:1 respectively. Oxyclozanide and rafoxanide at 10−3 M inhibited enzyme activity by 100% in homogenates from all three species while hexachlorophene at 10−3M also caused 100% inhibition in homogenates from Fasciola gigantica and P. explanatum but only 65% of malate oxidation in Fasciolopsis buski homogenates. Nitroxynil at 10−3M produced 60% inhibition in F. buski homogenates yet had little effect at this concentration on preparations from the other species. Little inhibition was seen with diamphenethide, even at high concentrations. Rapid death of Fasicola gigantica and P. explanatum resulted in vitro when 10−3M oxyclozanide, hexachlorophene, nitroxynil or rafoxanide, were added to the incubation medium. Fasciolopsis buski was killed by 10−3M oxyclozanide but at this concentration the remaining compounds only caused reduced activity. Assay of malate dehydrogenase following drug treatment in vitro failed to show any appreciable reduction in enzyme activity in Fasciola gigantica and P. explanatum but oxyclozanide and hexachlorophene produced inhibition in Fasciolopsis buski. The mode of action of these compounds is discussed.

The major organs, other than lymphatics, of jirds (Meriones unguiculatus) with prepatent and chronic patent infections of Brugia pahangi were studied by standard histological, electron microscopical and fluorescent antibody techniques. Changes observed and not previously described in detail or in large numbers of animals are reported. Multifocal non-suppurative interstitial nephritis was observed in 4% of animals with patent infections of 163 days duration and in 69% of animals with patent infections of 274 days duration. Glomerular changes were not observed in kidneys of any animals infected with B. pahangi. The occurrence of large granulomata composed of lymphocytes, macrophages, eosinophils and giant cells in the liver and smaller granulomata in the spleen correlated with patency of infections but microfilariae or worm antigens were not observed in these areas. Amyloid deposits were demonstrated in the spleens of 4% of animals with patent infections of 163 days duration and in 38% of animals with patent infections of 274 days duration but were not seen in uninfected animals of the same age or animals receiving only challenge inoculations of 28 days duration.

The utility of human filarial serum immunoglobulin (FSI) in detecting circulating antigen in filarial sera was studied by counter Immunoelectrophoresis (CIEP) and the indirect haemagglutination test (IHAT). CIEP was found to be better than IHAT. 23 out of 30 sera from persons with microfilaraemia and one of 30 clinical cases of filariasis, but none of the normal sera or sera from those with helminths other than filariae, showed the presence of circulating filarial antigen in CIEP. FSI was fractionated by DEAE- Sephadex A-50 column chromatography and the antibody active in CIEP was found to be IgG in nature.

Histochemical techniques were used to study the chemical composition of Mehlis’ gland secretion in Ceylonocotyle scoliocoelium. The results suggest the secretion to be lipoproteinous in nature, containing several hydrolytic and oxidative enzymes. In tests for nine hydrolytic enzymes only seven were detected in relation to gland cells, ihe two enzymes not showing any reactivity being glucose-6-phosphatase and 5-Nucleotidase. Alkaline phosphatase and ATPase have been associated with the permeability and transport of precursors of synthetic material from the surrounding parenchyma and with eliminating the waste products from the gland: ACPase in (i) generating a favourable milieu in the gland for the synthesis of secretory material and (ii) in regulating secretion and its over production; TPPase in elaborating the secretion, esterases in the metabolism of the gland. Intense SDH and MAO activities were related to high synthetic activity of the gland cells. Phenol oxidase—a key enzyme involved in tanning was absent.

In each month for one year 30 perch. Perca fluriutilis L., 1758. were examined for infection with Acanthocephalus lucii (Müller. 1776): 7·78°, of the population was infected with a mean intensity of 2·61 worms/infected fish. No seasonality of occurrcncc of maturation was observed owing to limited data. In older fish the incidence and intensity of infection was greater than in younger specimens. The parasite was significantly over-dispersed within the perch population, k = 00395...P(x2 = 9·07)>0·05. All specimens of A. lucii were found in the third quarter of the intestine from the pyloric caeca to the rectum. Evidence is presented in favour of mutual exclusion between A. lucii and the cestode Proteocephalus percae (Müller, 1780) and the nematode, Camallanus lacustris (Zoega, 1776).