A method is described for the isolation of high molecular weight DNA from females of potato cyst nematodes. Restriction enzyme analyses of repetitive DNA revealed 30 bands specific for Globodera rostochiensis and 8 bands specific for G. pallida. None of the repetitive DNA bands resolved was common to both species. Hybridization patterns, obtained with a DrosophilaβJ-tubulin probe, revealed 4 common bands, 3 bands specific for G. rostochiensis and 12 bands specific for G. pallida.

The suitability of motility indices and tetrazolium-based colorimetric assays for the determination of the viability of adult Onchocerca volvulus after in vitro exposure to potential macrofilaricides has been examined. Experimentation showed that both techniques could be applied to adult O. volvulus, although the variability between individual worms necessitated the use of large experimental groups. The potential of using cut anterior tips of female O. volvulus for screening was also investigated. These were shown to give reasonably consistent motility indices, and drug effects were discernible even after 72 h in vitro culture. Application of these viability criteria to studies on the short-term in vitro survival of intact male and female O. volvulus incubated in Eagles MEM plus serum, under 5% CO2 in air, showed this medium to be suboptimal with a greater than 50 % loss of worm viability within 144 h of nodulectomy. Males isolated by the collagenase technique were shown to be significantly less viable than dissected males, by both motility indices and tetrazolium reduction. The results highlight the need to use either dissected males, or in the case of females, the need to minimize exposure to collagenase solution. A possible mechanism for selecting a more uniformly viable female worm population is discussed. Examination of the in vitro effects of CGP 20376 using these viability criteria/assay systems showed some delayed suppression of worm motility, but after 120 h in vitro CGP 20376 was not macrofilaricidal against male or female O. volvulus. Male worms were also implanted subcutaneously into gerbils. Treatment of these animals with CGP 20376, with autopsy 2 weeks later, resulted in a small macrofilaricidal effect (28% worm death). Some reduction in the motility of living worms recovered from CGP 20376-treated gerbils was also evident. Good survival of control worms recovered 2 weeks post-implantation suggests that male O. volvulus might survive longer subcutaneously. The prospects for undertaking meaningful drug evaluations against O. volvulus in vitro (and in vivo in rodents) is therefore promising, but because of parasite availability will probably be limited to those compounds which have shown potential in other filarial test systems.

An epidemiological survey of intestinal helminthiases was conducted on 766 primary school children aged 5–16 years from Ile-Ife, Nigeria. On the basis of stool examinations, the prevalence of Ascaris lumbricoides, Trichuris trichiura, hookworm and Strongyloides stercoralis was 88·5, 84·5, 33·1 and 3% respectively. Intensity of infection was measured indirectly by egg counts for each species of helminth and also by counting worms passed after chemotherapy in the case of A. lumbricoides. The influence of host age and sex on infection levels was assessed. Relationships between the intensities of A. lumbricoides, T. trichiura and hookworm in individual children were identified. After anthelmintic treatment with levamisole, the frequency distribution of A. lumbricoides per host and the relationship between parasite fecundity and worm burden were investigated.

Comparison of glycolysis in Brugia pahangi and Onchocerca volvulus by C nuclear magnetic resonance (NMR) spectroscopy showed that the former organism is predominantly a lactate fermenter and the latter resembles more closely the metabolism of a mixed acid fermenter producing lactate, succinate, acetate, ethanol, formate and carbon dioxide. Both organisms synthesize glycogen as a storage carbohydrate. Glutaminolysis in both organisms proceeds by the δ-aminobutyrate shunt to produce succinate which is then further metabolized to acetate and carbon dioxide as end-products.

Groups of cattle were immunized with 10−2 dilutions of sporozoite stabilates of Theileria parva lawrencei derived from African buffaloes either alone or in combination with Theileria parva parva derived from cattle and concomitant treatment with either long or short-acting formulations of oxytetracyline. At 90 or 120 days after infection, uninfected Rhipicephalus appendiculatus nymphal ticks were applied to individual immunized cattle and the resultant adults ticks were applied to individual susceptible cattle. Theilerial infection developed from ticks fed on 6 out of 11 animals investigated for evidence of a carrier state. Two additional animals were shown by cell-culture isolation to have persistent theilerial infections. Nine cattle infected with the parasites from carrier animals were treated with parvaquone and 7 recovered. These recovered cattle were then challenged with the original immunizing stabilates at 10° dilution together with the original immunized and carrier cattle. Six out of 7 cattle which had recovered from carrier-derived infection succumbed to this challenge and died but none of the original immunized cattle showed theilerial reactions. When a carrier-derived sporozoite stabilate was used to challenge cattle immune to the original immunizing parasite, they proved to be immune. Cattle immune to the carrier-derived parasites were all immune to challenge with the original parasite. A monoclonal antibody profile aginst T. parva schizonts isolated by cell culture from samples of the experimental animals did not appear to be sensitive enough to determine the antigenic differences between the carrier-derived parasite and the original immunizing parasite. Indications are that the carrier state is not likely to produce new antigenic strains which would be dangerous to immunized cattle.

A survey was carried out to determine values for the prevalence and intensity of infection of intestinal helminths in children living in Cocle Province, Republic of Panama. The data set consisted of the results of microscopic examinations (modified Kato Katz technique) of stool samples collected in November 1987 from 661 children attending primary schools in 4 communities in the province. The overall prevalences of Ascaris lumbricoides, hookworm and Trichuris trichiura infections were found to be 18·2, 12·0 and 27·5% respectively. There were significant differences between the infection prevalence values for children attending the different schools, but not with respect to age or sex. Positive associations were detected between particular pairs of infections and these were most evident when Trichuris trichiura was involved. The data revealed evidence of a positive association between siblings at one school only for each helminth infection.

Seven and 56-day-old Hymenolepis diminuta were exposed to complement by incubation in 50% normal rat serum (NRS) in modified Hanks' saline. Ultrastructural studies revealed that the scolex/neck region remained relatively intact whilst in the strobila region microthrix denudation and loss of distal cytoplasm were observed. When complement-mediated damaged worms were incubated in vitro in 50% heat-inactivated normal rat serum (hiNRS) plus M199 or implanted into the duodenum of NMRI mice repair occurred, although destrobilated parasites were only found in vivo. The regions undergoing repair contained tegumental protrusions, vesicles, large electron-lucent areas and large quantities of lipid. Microtriches were formed parallel to the parasite surface and were raised into a perpendicular position. It is suggested that the regenerative process exhibited after complement-mediated damage does not mimic totally the embryological development of the surface layer.

A comparison of feeding and breeding performance was made between a laboratory strain (LS) and two freshly collected field strains (FS1, FS2) of Rhipicephalus appendiculatus. The LS had been cultured for over 30 years on tick-susceptible rabbits. When fed on susceptible rabbits LS produced smaller eggs and unfed larvae, nymphs and adults than those of FS. Eggs and larvae from females engorged on cattle were larger than those from females engorged on rabbits. LS and FS females engorged on susceptible hosts were of similar weight, but the FS females were twice as heavy as LS females when tick-resistant hosts were used. A higher proportion of LS ticks than of FS ticks engorged on susceptible hosts, but a lower proportion on resistant hosts. Thus on susceptible hosts LS showed a higher reproduction efficiency than FS, but a lower one than FS on resistant hosts. The proportional reductions of engorged weights and numbers feeding successfully on resistant hosts were significantly lower for LS than FS ticks. Cross-resistance was low between LS and FS. Although all strains were affected by host resistance, it was concluded that the field strains were better adapted to withstand resistance than the laboratory strain.

Weight and length profiles are presented of 3505 Ascaris worms recovered after mass anthelmintic treatment of a human community in January 1984 and, after an 11 month period of reinfection, in November 1984. Male and female worms recovered after reinfection were significantly heavier and longer than those expelled after initial treatment (P < 0·0001). Multiple regression models were employed to examine variability in parasite size. A positive influence of host body weight on the weight of parasites recovered in January, but not in November, was observed. No negative relationship was recorded at either date between worm size and the total number of worms harboured, even after controlling for host weight. Striking host age-related variability was observed in the distribution profile of weights and lengths of individual worms recovered in January. Children harboured predominantly smaller worms before initial treatment, while adults expelled mainly heavy worms. In contrast, worms expelled by both children and adults after reinfection were heavier and more homogeneous in size, particularly within the relatively heavily infected group. These patterns argue against a primary role for density- dependent or acquired resistance mechanisms in determining the size of Ascaris in humans. However, the results are consistent with a hypothesis initially suggested by Jung (1954) that established worms may inhibit the development of newly acquired Ascaris larvae, perhaps regulating their own abundance.