Babesia vesperuginis is described from blood of two species of British bat: Pipistrellus pipistrellus and Myotis myslacinus. Reticulocytes appeared significantly elevated in blood films of P. pipistrellus infected with B. vesperuginis compared with uninfected laboratory-maintained bats or apparently uninfected wild-caught bats. Infected captive bats had significantly enlarged spleens. B. vesperuginis was transmitted by inoculation of infected blood to 5 uninfected captive P. pipistrellus. The course of infection followed a pattern of a rising parasitaemia accompanied by a rise in reticulocytes, followed by a fall in parasitaemia to low (<0·1%) or undetectable levels. When sacrificed, the Babesia-infected bats had significantly lowered blood haemoglobin, significantly raised white blood cell counts and enlarged spleens compared to uninfected bats. Attempts to transmit the parasite to irradiated and athymic ‘nude’ mice by inoculation of infected blood were unsuccessful. The experimental results and observations of infected wild bats indicate the potential pathogenicity of B. vesperuginis to bats. It is likely that the vector of B. vesperuginis is Argas vespertilionis because no Ixodid ticks were found on P. pistrellus.

A comparative isoenzyme study between a natural population of Echinostoma caproni and 2 strains of E. caproni and E. togoensis, maintained for a long time in the laboratory led to the following conclusions. (1) The natural E. caproni population showed polymorphism of associated PGM and GPI genotypes. Some zymograms were identical to those of experimental strains. Allelic frequencies show that the natural population is panmictic according to the Hardy-Weinberg equilibrium. (2) The laboratory strains were monomorphic, and interbreeding produced double-heterozygous F1 progeny, identical to those of the natural population.

Eimerian sporozoites can be recovered from intestinal washings after oral administration of oocysts to chickens but suspensions of sporozoites are usually prepared in the laboratory by incubation of sporocysts or fractured oocysts in vitro, at body temperatures, with relatively high concentrations of trypsin and bile salts. Since these agents affect membrane structure, the surface membrane of proteins of Eimeria tenella sporozoites excysted in vivo and in vitro have been compared. Surface radio-iodination followed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) showed that more 125I was incorporated into polypeptides on sporozoites excysted in vivo than on sporozoites excysted in vitro. The 125I-polypeptide profile of sporozoites excysted in vivo was more resistant to subsequent incubation with pure trypsin than that of sporozoites excysted in vitro, but incubation with bile salts resulted in the loss of some iodinated polypeptides from both preparations of iodinated sporozoites. Reaction with combinations of crude trypsin and bile salts led to the lysis of sporozoites. The method of excystation had no effect on the reaction of convalescent chicken serum with Western blots of sporozoites but the results of immunofluorescent staining carried out with mouse monoclonal antibodies indicated that the structure of the cell surface was altered and some antigenic determinants were lost from sporozoites excysted in vitro. In contrast, neither the infectivity of sporozoites determined in vivo, nor their invasion of cultured cells was changed by the method of excystation.

The tegumental surface of Schistosoma margrebowiei as viewed by scanning electron microscopy is described. Both spined and unspined tubercles were found on the dorsal and dorso-lateral surfaces of sexually mature (in copula) male worms. Unpaired males lacked spined tubercles and the development of the spines is considered to occur only when worms are in copula. The females lack tubercles. The importance of tubercle structure in the identification of schistosome species and the effect of sexual maturity on their development is discussed.

In some Biomphalaria glabrata–Schistosoma mansoni combinations snails are susceptible to infection as juveniles, but have variable susceptibility as adults. These snails become non-susceptible at the onset of egg-laying and typically revert to susceptibility in old age. Certain stocks of B. glabrata have the capacity to form amoebocytic accumulations in the atrium, and this ability is under genetic control. The atrial amoebocytic accumulations are transitory, typically appearing at onset of egg-laying and disappearing after a few months. A snail stock which has genetic tendencies for both adult variable susceptibility and atrial amoebocytic accumulations was studied. An association between the time of occurrence of adult non-susceptibility and atrial accumulation is revealed as snails never became infected with S. mansoni when amoebocytic accumulations were present. Developing parasites, however, were not necessarily encapsulated and destroyed by amoebocytes. Some sporocysts were able to delay development until the amoebocytic accumulations disappeared. The timing of atrial amoebocytic accumulations and resulting transient non-susceptibility in this host-parasite combination could influence snail population dynamics.

A laboratory life-cycle of Schistosoma bovis was established in order to study the host-parasite relationship in immunologically intact and T-cell deprived mice. Normal mice were found to have ‘self-cured’ their S. bovis infections almost completely by 10 weeks after cercarial administration, and there was no evidence of self-cure by day 79 in T-cell deprived animals, Thus, groups of deprived mice autopsied between 9 and 11 weeks after infection were invariably found to have greater worm burdens and a greater total number of eggs in the liver than comparably-infected normal mice. However, liver egg counts/worm pair were similar in the two types of host, and differences between normal and deprived mice with respect to total S. bovis egg counts in the intestine were also not consistently in the same direction in all experiments. Faecal egg counts were always less in deprived mice than in normal mice, even in an experiment in which the deprived mice had a significantly higher intestinal tissue egg count than the normal control group. The results are discussed in relation to the better known S. mansoni/mouse host-parasite relationship.

Normal and T-cell deprived mice have been compared in their response to infection with Schistosoma bovis. The deprived mice survived longer than comparably infected, immunologically intact controls, despite an increased longevity of the adult S. bovis worms in the former animals giving rise to higher tissue egg densities. The reduced pathology in deprived mice was due to inhibition of T-cell dependent granuloma formation around tissue-bound schistosome eggs, with concomitantly decreased tissue disruption as evidenced by smaller spleens and lower circulating transaminase concentrations. These observations on S. bovis contrast with the greater morbidity and earlier mortality induced by S. mansoni in T-cell deprived mice, the latter due to an hepatotoxic potential of S. mansoni eggs that is expressed in the absence of the host immune response. The absence of hepatocyte damage around S. bovis eggs in deprived mice indicates that this schistosome lacks such a toxin, and this could explain why during S. bovis infection synthesis of the two acute-phase proteins, complement C3 and serum amyloid P-component (SAP) here seemed less T-dependent than has previously been found during S. mansoni infection of mice. In a time-course experiment the hypergammaglobulinaemia induced by S. bovis, and the specific IgG antibody response against egg antigens were significantly T-cell dependent during the early stages of patency. Similarly, in most experiments assayed once between 9 and 11 weeks after S. bovis infection, deprived mice had significantly reduced hypergammaglobulinaemias, and reduced specific IgM and IgG antibody responses against both worm and egg antigens.

Uric acid is the most important constituent in the urine of insects. Infective metacyclic forms of the stercorarian trypanosomes are produced in the rectum of their insect vector and are thus in contact with uric acid. Using a culture system which permitted the growth of the insect stages of Trypanosoma musculi, we studied the influence of uric acid on the metacyclogenesis of this parasite. When added to the culture, uric acid enhanced the production of metacyclic forms. Furthermore, it rendered these trypanosomes highly infective by the oral route. It is suggested that uric acid may play an important role on the metacyclogenesis of T. musculi.

Teneral male Olossina morsitans centralis, G. austeni, G. palpalis palpalis, G. p. gambiensis, G. fuscipes fuscipes, G. tachinoides and G. brevipalpis were fed on the flanks of Boran calves infected with Trypanosoma vivax stock ILRAD 2241 isolated from a cow in Likoni, Kenya; stock ILRAD 2337 isolated from a cow in Galana, Kenya; stock ILRAD 1392 isolated from a cow in Nigeria; or, stock EATRO 1721 isolated from G. m. submorsitans in Nigeria. The tsetse were fed on the infected hosts for 24 days and were then dissected to determine the infection rates. In G. m. centralis and G. brevipalpis, the mature infection rates of T. vivax from Kenya were 61·1 %, and 75·3% for ILRAD 2241, and 36·2% and 58·2% for ILRAD 2337, respectively. In G. austeni and in the four palpalis group of tsetse, the rates for these two stocks were very low and ranged from 0% in G. p. palpalis to 1·8% in G. austeni for ILRAD 2241 and from 0% in G. f. fuscipes to 5% in G. tachinoides for ILRAD 2337. In contrast, the hypopharyngeal infection rates of T. vivax from Nigeria were quite high in all the 7 tsetse species and sub-species. They ranged from 55·5% in G. austeni to 919% in G. p. gambiensis for ILRAD 1392, and from 71·4% in G. austenei to 97·1 % in G. brevipalpis for EATRO 1721. It is suggested that successful establishment of T. vivax infection in a particular tsetse species could depend on the biochemical characteristics of its attachment sites in the food canal and the efficiency of bloodstream trypomastigotes of a particular T. vivax stock to attach to such sites and undergo complete development to meta-trypanosomes in the hypopharynx of the vector.

The dominant repetitive deoxyribonucleic acid (DNA) sequence in the genome of a clone of Trypanosoma (Nannomonas) simiae has been identified and cloned as a recombinant plasmid. The recombinant plasmid was used in hybridization analyses of DNA samples obtained from various trypanosome species and subspecies. The results indicated that the T. simiae repetitive DNA sequence hybridized with DNA derived only from T. simiae; it did not hybridize with DNA derived from clones or stocks of T. congolense, or from any other trypanosome species examined. A preliminary characterization of the cloned DNA sequence and its use in the identification of T. simiae of similar genotypes are presented.

The class-specific antibody responses of 3 strains of mice (C57/Bl10, BALB/C and CBA/N) known to vary in their ability to control the microfilaraemia which follows the subcutaneous transplantation of adult female Dipetalonema viteae has been investigated. The 3 mouse strains showed significant variation (a) in total levels of immunoglobulins and (b) in ability to recognize individual radio-isotope-labelled antigens as measured by coprecipitation. Within each mouse strain it was noted that antigens could vary with respect to the nature of the isotype of the antibody response which they elicited. Furthermore, by comparing results obtained from class-specific coprecipitation with surface ELISA it was found that a similar variation between responses to individual epitopes was also likely. No differences were observed in the humoral response of the 3 mouse strains which could explain the known resistance of the C57/B110 strain; reasons for this are discussed.

Chronic primary infections with Heligmosomoides polygyrus (Nematospiroides dubius) are still relatively poorly documented, particularly in relation to the role of host resistance in limiting worm survival. In the present work the duration of infection with H. polygyrus was studied in CFLP mice given doses of infective larvae ranging from 50 to 500 L3. The least heavily infected (50 L3) group ceased egg production earliest (week 36) whereas eggs were still detected in the faeces of mice given 500 larvae in week 42. At autopsy (week 42) mice given 50 larvae had virtually lost their entire worm burden with 5 out of 11 mice still harbouring a single worm each. However, all the mice in the group given 500 larvae were still infected, the highest worm burden being 93. The concentration of serum IgGl and specific antibody was highest in mice given 500 larvae, but sera taken from mice with declining worm burdens 19–38 weeks post-infection did not contain detectable host-protective antibody. During the course of infection in CFLP mice, H, polygyrus sustained irreversible changes in its capacity for subsequent survival. Thus, adult worms transferred to naive mice 2, 7, 14, 30 or 36 weeks post-infection did not live longer than worms of a comparable age in the respective donor group. In contrast, primary infection worms taken from jirds in which expulsion is usually completed by 6 weeks post-infection, re-established in mice and survived considerably longer than in the group of donor jirds. These results were discussed in relation to the possible interactions between parasite senility and immunomodulation, and host resistance in limiting primary infections with H. polygyrus in mice and jirds.

The nematode Trichinella spiralis is able to modulate the antibody response, as measured by the plaque-forming cell (PFC) technique, to three thymus-dependent (TD) antigens: (1) a heterologous antigen unrelated to the parasite (sheep red blood cells (SRBC)); (2) an antigenic fraction, rich in phosphorylcholine (PC), obtained from T. spiralis (FCpl) and (3) a heterologous antigen unrelated to the parasite, but sharing the PC epitope with the FCpl fraction (PC-KLH). During the life-cycle of the parasite in BCF1 mice, two opposing immunomodulating activities occur: (1) an immuno-potentiating activity in mice infected during the intestinal and larval migratory stages, for all three antigens, and (2) a carrier-specific immunosuppressive response in mice infected and immunized with the FCpl fraction during the muscle phase of the life-cycle. The anti-PC PFC response of these mice is dependent on the infection dose and decreases from day 35 post-infection (p.i.) until at least day 85 p.i.. The factor responsible for the stimulating effect observed during this stage is the presence of migratory larvae in the host. All the foregoing seems to indicate that T. spiralis can use specific suppression mechanisms to aid in its own survival.

Taenia cestodes were obtained from 5 different definitive host species in Kenya and 175 different samples were examined by classical morphological methods and by isoenzyme analysis using isoelectric focusing in agarose. Gels were stained for 17 different enzymes and 3 of these were used in the construction of isoenzyme profiles. The samples fell into 25 zymodemes, and no zymodeme contained more than 1 species of Taenia, indicating that isoenzyme analysis can reliably be used for the identification of species of this genus.

Relationships between ascariasis and lactose digestion and between ascariasis and food transit time from mouth to caecum were investigated in young children from Chiriqui Province, Republic of Panama. The breath hydrogen method was used in both studies. Ascaris-infected children showed a significantly poorer degree of lactose digestion following a test oral load than uninfected children. Recovery of the capacity of the children to digest lactose was still not fully complete for at least 3 weeks following anthelmintic treatment. On average, the mouth-to-caecum transit time was similar in infected and uninfected children, but among the Ascaris-infected children the transit time tended to be shorter in relation to the intensity of infection. Evidence from a cross-sectional survey indicated that ascariasis was significantly associated with reduced plasma vitamin A and carotenoid concentrations. This relationship remained after controlling for a range of socio-economic variables. Ascaris-infected children were frequently found to have lower haematocrits and blood haemoglobin concentrations than uninfected children, but these relationships could not be attributed to ascariasis alone.

An epidemiological survey of intestinal parasitic infections was conducted in a sample of 203 children aged 3–5 years from a semi-urban and a rural community in Chiriqui, Panama, in 1983–4. On the basis of stool examinations, the prevalences of Ascaris lumbricoides, Trichuris trichiura, hookworm, Giardia intestinalis, Entamoeba spp. and Strongyloides stercoralis were found to be 27, 34, 14, 15, 5 and 4% respectively. The results from children from the two communities were compared. Polyparasitism occurred significantly more often in rural than semi-urban children. Following anthelmintic treatment with levamisole, the numbers of A. lumbricoides passed/child were recorded and the frequency distribution of the parasite was observed to be highly aggregated with a variance to mean ratio of 10·2. For A. lumbricoides, relationships between worm burden, worm biomass and egg production were investigated. In the data analysis, an attempt was made to explore the influence of numbers of male worms on egg production. The results are compared with those obtained during other recent studies on the epidemiology of A. lumbricoides infection in other countries.

Malnutrition and helminth infection are amongst the most prevalent chronic conditions affecting human health globally. It is estimated that parasitic helminths infect more than 1 billion people, and that more than 2 million clinical cases occur each year (Peters, 1978; Walsh, 1984). Estimates of the incidence of clinical malnutrition suggest that between 5 and 8 million cases occur annually. In many parts of the developing world malnutrition and infection conjointly are the most serious health problem in children, acting as primary or more often as secondary factors in mortality (Puffer & Serrano, 1973). The impact on health is exacerbated because both conditions are chronic, are most common in growing children and, most importantly, tend to occur together in the same individuals (Pawlowski, 1984; Chandra & Newberne, 1977).