Experiments describe the use of ethanediol to store Onchocerca microfilariae in liquid nitrogen. The technique involves a 2-stage incubation of the parasites at 37 °C and 0 °C in ethanediol, before rapid cooling to − 196 °C. Viability has been assessed by motility, by migration in a proxy host and by development to the infective stage in the insect vector. A total of 71–79% of the cryopreserved microfilariae was shown to be viable compared to unfrozen controls. The technique is simple, inexpensive and very effective when compared to previous cryopreservation procedures for microfilariae and should be particularly suited for use under field conditions.

The levels of erythrocyte membrane sialic acid from 17 patients with Plasmodium falciparum malaria and 1 with Plasmodium vivax malaria, in Papua New Guinea, have been compared with 9 uninfected controls. The amounts of radioactivity incorporated into the major erythrocyte glycoproteins by the periodate/NaB3H4 or galactose oxidase plus neuraminidase/NaB3H4 methods were unchanged by malaria infection. The electrophoretic mobilities of these proteins also were unaffected. Several new glycoprotein bands with molecular weights (mol. wt) of 160000, 89000, 46000, 42000 and 33000 Daltons were labelled on the surface of erythrocytes from infected individuals; however, none of these bands appeared in all malarious samples. Sialic acid levels on the erythrocyte membrane were also measured by exhaustive neuraminidase treatment and quantitative assay of released sialic acid. The amount of sialic acid was raised in 1 infected individual, within the normal range for Europeans in 4 others, and below this range with 3 patients. Apparently, extensive removal or modification of sialic acid on the surface of uninfected erythrocytes does not occur in human malaria, in contrast to the results obtained in earlier studies with the lethal murine malarias.

The development of T cell reactivity toward schistosomula during murine Schistosoma mansoni infection has been studied using an adaptation of the in vitro lymphocyte proliferation assay in which the response is elicited by exposure to living schistosomula. The reactivity measured in this system was shown to be a T lymphocyte function and to require the presence of adherent cells. This assay may therefore provide a new method for analysis of basic interactions between host cells and schistosomula. Lymph node cell responses were observed in two phases, the first of which appeared during the second week after infection, reflecting the immunogenicity of schistosome larval forms. A later, more pronounced response appeared during the chronic stage of infection, where sensitization appeared to be stimulated primarily by ongoing exposure to adult worms, rather than eggs. Lung-stage and skin-stage larvae elicited a similar degree of thymidine uptake by cells from chronically infected mice. Intact skin-stage larvae and particulate fractions provoked greater proliferation than soluble larval constituents, indicating that the lymphocyte response is directed in large part toward determinants which remain associated with the schistosomula during culture. However, the presence of major histocompatibility complex products on the membrane of lung-stage schistosomula did not influence the presentation of larval antigens to sensitized lymphocytes. The implications of these findings in immunity to schistosomiasis are discussed.

125I-labelled, isolated variable surface glycoproteins (VSGs) of Trypanosoma b. brucei bind both homologous and heterologous anti-VSG sera and binding to heterologous antisera may be blocked by other unlabelled VSGs (Barbet & McGuire, 1978). This paper presents results which suggest that oligosaccharide residues have importance in the antigenic structure of VSG cross-reacting determinants. The ability of VSG to bind heterologous anti-VSG sera was destroyed by periodate oxidation but not by extensive proteolysis. A VSG glycopeptide fragment was isolated from two different VSGs, which blocked by 100 % the binding of VSG to heterologous anti-VSG sera and therefore contained the cross-reacting determinants. The native glycopeptide fragment was resistant to digestion with trypsin, pronase or leucine aminopeptidase and prolidase. We also show that a VSG synthesized in the reticulocyte lysate cell-free system was not immunoprecipitated by heterologous anti-VSG sera in contrast to the same VSG labelled by metabolic incorporation of [35S]methionine in vivo.

In 1977, a parasitological survey was undertaken of stool samples collected from 335 people from 5 villages in semi-arid regions of peninsular India. Stools, which were collected from various individuals in a stratified sample of 40 matched households from each village, were examined by standard diagnostic procedures. Eggs of Ascaris lumbricoides and protozoan cysts, which were identified on morphological grounds as belonging to Entamoeba spp., were most common. Other protozoan cysts were considered to be those of Balantidium coli, and eggs of hookworm and Hymenolepis nana were also observed in some of the stool specimens. The prevalence of parasitic infections varied between villages. The village with the highest prevalence of Ascaris (70%) appeared to have the greatest demands made on its meagre drinking-water supply. This village is located in a dry, windy and dusty region and it is speculated that, in addition to well-established transmission mechanisms, the villagers may be exposed, perhaps through contamination of uncovered drinking-water wells and inhalation, to wind-borne Ascaris eggs. In 1967, a WHO Expert Committee Report on the Control of Ascariasis pointed out that information on the frequency of dust-borne infection with Ascaris in man was inadequate.

Incubation of adult Schistosoma mansoni at 37 °C in chemically defined media caused the shedding of variable amounts of the parasite's tegument. In phosphate-buffered saline, pH 7·4, 37% of 125I-labelled wheat germ agglutinin which was attached to the schistosome surface was released within 5 min. When the released material was collected by centrifugation at 55000 g for 1 h, the pellet was seen to consist of components of the parasite tegument and contained 1% of the parasite protein and 6·2% of the 5′-AMPase activity. By monitoring the release of the gut enzyme, haemoglobinase, it was shown that predominantly tegumental material was released under these conditions. The material released from the parasite was separated by discontinuous sucrose gradient centrifugation into 4 major fractions and it was shown that a material banding at low density was highly enriched in vesicles of parasite outer membrane. Major polypeptides of apparent molecular weights 135000, 110000, 90000, 65000, 47000 and 40000 and glycoproteins of apparent molecular weights 135000, 120000, 65000, 63000 and 30–40000 were identified in this fraction. Comparison of the distribution of 5′-AMPase activity and the contents of each fraction as revealed by ultrastructural examination showed that this enzyme is a good marker for the tegumental outer membrane.

Haemonchosis is an acute problem in India. Three species of Haemonchus occur. These are H. contortus (Rudolphi, 1803) which occurs in sheep, goat, cattle, buffalo and other ruminants; H. longistipes Railliet && Henry, 1909 occurring in camels and H. similis Travassos, 1941 in cattle. Seasonal fluctuation of H. contortus occurs, with infection being more frequent in autumn ≻ summer ≻ winter ≻ spring, and infection in sheep and goats has been reported to be 100 %. Various aspects of haemonchosis have been investigated. However, the fundamental and the most challenging areas in Haemonchus research remain almost untouched. In order to forecast the development of haemonchosis, epidemiological studies should be undertaken on the prevalence, distribution and seasonal incidence of the worm to understand the effects of climatological factors like rainfall, humidity and temperature. The sparse and inadequate studies of metabolism need to be extended to other areas of Haemonchus biochemistry to provide additional possibilities for exploration of hostparasite differences. Clinical haemonchosis in sheep, goats and other ruminants should be studied in order to calculate losses caused by mortality and the cost of anthelmintic medication. Most anthelmintics are expensive, and are not easily available to our farming community, therefore a search for many more indigenous anthelmintics (such as Wopell, Krimos, Sonex etc) must be made. Detailed knowledge of the mode of action and route of entry of anthelmintics at the molecular level could also be beneficial, particularly when the strains of H, contortus have been identified as resistant to some anthelmintics. The prospects of producing a vaccine against H. contortus should be explored. Attempts in this field have already been made by overseas workers (see Clegg && Smith, 1978) and in India too, work has been undertaken at Kerala (Sathianesan, personal communication). Therefore, because of its economic importance and wide distribution, H. contortus provides fascinating research material particularly in the warmer regions of the world.

Between August 1978 and July 1979, freshwater gastropods were collected at monthly intervals from 9 different non-lacustrine habitats in the Mwanza region of Tanzania. Of a total of 11708 gastropods representing 14 species, 1748 (14–9%) were infected with trematode sporocysts and/or rediae. Altogether 38 morphologically distinguishable ‘species’ of cercariae were recovered (13 furcocercous, 10 xiphidiocercaria, 6 echin-ostome, 4 cystophorous, 3 gymnocephalous and 2 amphistome species), 22 of which did not conform to previously described African species. The majority (63–8%) of all mature infections were xiphidiocercariae. Biomphalaria pfeifferi, B. sudanica and Ceratophallus natalensis each yielded 11 species of cercariae. Lymnaea natalensis had the highest overall prevalence of infection (36–9%). Cercaria guttera from L. natalensis accounted for 20–4% of all recovered trematode infections and C. blukwa from Biomphalaria accounted for 18–4% of all infections; the high prevalence of these two xiphidiocercariae may alter the transmission patterns of Fasciola gigantica and Schistosoma mansoni, respectively. S. mansoni was recovered from both B. sudanica (22 of 2393 infected) and B. pfeifferi (79 of 1913 infected); S. haematobium (or related species) was recovered from Bulinus (Physopsis) nasutus (50 of 1503 infected) and to a lesser extent from B. (P.) africanus (6 of 186 infected). The findings are discussed in relation to the biological control of trematode diseases in Tanzania.

Three populations of small wild British rodents were studied by capture–recapture methods over a period of 3 years, a fourth group was studied for 1 year and a fifth was sampled annually for 4 years. Blood smears were taken from 3 species of rodents: the woodmouse A podemus sylvaticus, the bank vole Clethrionomys glareolus (and an island sub-species C.g. skomerensis) and the short-tailed vole Microtus agrestis. The smears were examined microscopically. Four genera of haemoparasites Babesia, Hepatozoon, Trypanosoma and Grahamella were detected. Babesia was absent from C.g. skomerensis, Hepatozoon was rarely found in A. sylvaticus and M. agrestis and Trypanosoma was rare in A. sylvaticus. More males were infected than females but the difference was only statistically significant for the infection with Hepatozoon in adult C.g. skomerensis. Infections with Babesia and Hepatozoon were more prevalent in adult animals and infections with Trypanosoma were more prevalent in younger individuals. Only in C.g. skomerensis was there a significant difference between age classes in the prevalence of infection with Grahamella – there being more adults infected. Concurrent infections were detected, Hepatozoon being the parasite most commonly involved. The prevalence of infections was found to be approximately proportional to the number of animals known to be alive, regardless of the season.

The effects of prednisolone were investigated in C57B1/6 mice infected with Strongyloides ratti. In primary infections, the numbers of adult worms in the small intestine and larvae in the stools were increased and there was a slight delay in the spontaneous expulsion of worms. In secondary infections, there was an initial suppression of acquired resistance, with larvae appearing normally in the stools on the 5th day after infection. This was followed, however, by a rapid development of resistance and expulsion of worms over the next few days. Prednisolone treatment did not alter fecundity in primary or secondary infections. There was no evidence of autoinfection in control or corticosteroid-treated animals. Prednisolone abrogated innate resistance to infection in C3H mice. It is concluded that prednisolone probably facilitated infection by non-specific mechanisms as well as by suppressing specific acquired immunity.

The fluid layer within the cuticle of the nematode Nippostrongylus brasiliensis contains haemoglobin. The absorbance spectra of the haemoglobins extracted from whole nematodes were measured spectrophoto-metrically and the spectra of cuticular haemoglobin in individual living nematodes was obtained by microdensitometry. Adult female nematodes were confined under cover-slips in oxygenated saline and measurements of optical density of a small area of the cuticular haemoglobin were taken at 10 sec intervals. The optical density decreased over a period of 4 min at 543 nm and increased at 553 nm indicating deoxygenation of the cuticular haemoglobin; irrigation with fresh saline restored the haemoglobin to its oxygenated state. This demonstrates that cuticular haemoglobin loads and unloads oxygen in the living animal. Isoelectric focusing showed that mature nematodes have haemoglobins which are isoelectric around pH 7·0 and at pH 9·8. Isolated cuticular fluid contained the haemoglobin which was isoelectric at pH 9·8, but no other haemoglobin, and immature adults, which do not have cuticular haemoglobin, contained only those haemoglobins which were isoelectric at pH 7·0. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and column chromatography showed that the molecular weight of the cuticular haemoglobin sub-unit is 16·9–17·5 × 103 Daltons and that the haemoglobin exists primarily as a tetrameric molecule with a molecular weight of 65–75 × 103 Daltons. The presence of cuticular haemoglobin may allow adult Nippostrongylus to exploit oxygen-deficient areas within the environment of the rat's intestine where it would otherwise be unable to survive for prolonged periods.

Large numbers of Theileria parva sporozoites were separated from Rhipicephalus appendiculatus adult ticks by filtration and were then concentrated by centrifugation. The sporozoites were incubated at 37 °C with leucocytes from 6 cattle of Bos indicus and B. taurus types. Giemsastained smears and living preparations under interference contrast microscopy were used to follow the course of the infection of the leucocytes with sporozoites. Sporozoites were seen to attach rapidly to about 25% the leucocytes which they penetrated. After penetration by the sporozoites the morphology of the cells changed to show an increase in cytoplasm and an enlargement of the Golgi apparatus, with which the parasite appeared to become associated. The early intracellular or preschizont stages resembled Babesia parasites. From day 3, the parasite showed the typical morphology of the macroschizont of T. parva. Multiple infections were frequent and up to 8 schizonts were observed arranged around the Golgi apparatus. Multiply infected cells did not survive in culture but some of the cells infected with a single parasite divided to produce 2 infected daughter cells and infected lymphoblastoid cell lines were established in all 21 attempts.

The adenosine nucleotide and adenylate energy charge values of Nematospiroides dubius and Trichostrongylus colubriformis maintained in vitro under aerated and under near-anoxic conditions have been measured. Maintenance of the nematodes in both conditions had an adverse effect on their energy metabolism, but in comparing these effects it was found that the changes were more significant in those nematodes maintained in near-anoxic conditions and that the changes were more apparent in male nematodes. The smaller changes in the energy charge values of female worms, particularly N. dubius where there was no difference between worms in aerated conditions and those in near-anoxic conditions, were explained by the presence of eggs in the nematodes. At no time did the energy charge of nematodes in near-anoxic conditions fall below 0·50 but, whereas nematodes in aerated conditions were able to continue moving throughout the experiment, those in near-anoxic conditions stopped moving during the first 3 h. It is suggested that in the absence of sufficient oxygen the nematodes were able to maintain their energy charge above 0·50 by removal of AMP from the adenylate pool, resulting in the depletion of their total adenylate. The changes in the energy charge and behaviour of the nematodes are related to the survival of the nematodes in the oxygen-deficient environment which they inhabit in vivo.

The moulting behaviour of nymphal Rhipicephalus appendiculatus from the laboratory colony and 3 field strains from Kenya was greatly influenced by constant temperatures between 18 and 37 °C but was not significantly different for the 4 tick strains. Six batches of R. appendiculatus (Muguga laboratory) nymphs which had engorged on cattle parasitaemic with 4 stocks of Theileria parva (Kiambu 4, Kiambu 5, Muguga and Mbita 4) isolated in Kenya were incubated at constant temperatures between 18 and 37 °C during their pre-moult and post-moult periods. The Theileria infections in the salivary glands of the resultant adult ticks were assessed by staining with Feulgen's stain. Two stocks (Muguga and Kiambu 5) developed their highest infections in ticks incubated at 28 °C while the other two (Kiambu 4 and Mbita 4) developed their highest infections at 23 °C. Constant temperatures of 18, 33 and 37 ° C were detrimental to the development of salivary gland infections. Temperature influenced the rate of development and numbers of the earlier Theileria stages in the ticks. Engorged nymphal ticks incubated for 4 days at 37 °C during their pre-moult period developed lower infections than ticks exposed at 4 °C for 4 days.

Investigations of nematode hatching have concentrated on the parasitic forms, especially on synchronization between host and parasite life-cycles which, in some species, is so close that the parasite is dependent on the host for the hatching stimulus. Research into nematode hatching reflects the artificial separations created throughout nematology by defining research groups and their activities in terms of the host; consequently, useful comparisons between hatching of plant and animal parasitic nematodes have been few. With the increasing use by geneticists of nematodes as model animals and the interest in them by neuro-physiologists, molecular biologists and others, we hope that such distinctions will be lessened.

Guinea pigs acquired resistance to the feeding of immature Amblyomma americanum ticks after a single infestation. The initial larval and nymphal feedings resulted in cumulative mortalities of 27·2 and 28·9%, respectively. The second and third larval infestations yielded cumulative mortalities of 50·5 and 52·4%, compared to 18·9 and 24·4% cumulative mortality from controls. Second and third nymphal feedings resulted in 75·7 and 73·4%, and ticks from controls exhibited 36·6 and 34·7% cumulative mortality. The development of host resistance adversely affected tick feeding and resulted in abnormally coloured ticks and a protracted moulting period with a marked decrease in moulting ability. Histological examination of tick feeding sites on guinea pigs challenged twice revealed greater cavity and lesion sizes in hosts fed upon by nymphs than larvae. The primary cell type within these feeding sites were basophils at 12 h post-attachment, but by 72 h post-attachment eosinophils were dominant. The upper epidermal layer adjacent to both larval and nymphal feeding ticks had accumulations of basophils with a few eosinophils. Lymphocytes may have been involved in the resistance response because local lymph nodes in resistant hosts were much larger than in uninfested and singly infested hosts. Some of these nodes had secondary germinal centres.