Showing papers in "Acta Tropica in 1985"

Protective immunity and pathology induced by inoculation of mice with different subcellular fractions of Trypanosoma cruzi.

Abstract: Mice were immunized with subcellular fractions obtained by differential centrifugation from epimastigotes of Trypanosoma cruzi (Tulahuen strain). In a chronic model of Chagas' disease, they were challenged each with 25 bloodstream trypomastigotes. Non-immunized, non-challenged and non-immunized challenged animals were kept as controls. Among the challenged mice, those immunized with 105,000 g pellet (Mc) and 105,000 g supernatant (Cs) fractions presented positive xenodiagnosis, myocarditis and myositis similar to those shown by non-immunized challenged controls. The fractions enriched in flagella, the 5000 g pellet (P5) and the flagellar fraction (F) resulted in fewer animals with positive xenodiagnosis and in hosts partially protected from the development of myocarditis. In the absence of infection, Mc and Cs induced an intense myocarditis while F induced mild lesions similar to those found in the controls. P5 caused a myocarditis intermediate between that elicited by Mc and that in the controls. 50% of the animals immunized with Cs presented pathological electrocardiograms in the absence of challenge. The animals immunized with F and P5 and challenged were protected against the development of pathological electrocardiograms, whereas those immunized with Mc and Cs behaved like the non-immunized controls. The immunized, non-challenged animals presented anti-T. cruzi IgG antibodies, with titres which were lower than those shown by the immunized and challenged mice.--The results show the possibility of obtaining tissue lesions with antigenic preparations of T. cruzi in the absence of infection, and suggest that the mechanisms involved in the generation of myocarditis and electrocardiographic alterations are probably different, since these pathologies can be elicited by different subcellular fractions. Among the antigenic components of the parasite, the flagellar fraction gave the best immunoprotective properties, with little or no immunoaggressive effects.

The epidemiology of human and animal schistosomiasis in the Senegal River Basin.

Abstract: The results of four field surveys in Senegal are reported. 1. A snail survey in various parts of the Senegal River Basin, including the Senegal River, temporary rain-fed pools, swamps, irrigation canals and drains, ricefields and Lac de Guier was carried out. Three species of snails were commonly found: Bulinus guernei was the most common, occurring in permanent habitats, Bulinus senegalensis occurring in laterite pools in the eastern part of the Middle Valley, and also in the ricefields of Guede Chantier and Lampsar; B. forskalii was found in small numbers in Lac de Guier and Richard Toll. Three B. guernei were found to be naturally infected with S. bovis. Neither B. jousseaumei, B. globosus nor B. umbilicatus were found in our surveys. 2. A survey for urinary schistosomiasis was carried out in 100 villages (walo, near the Senegal River) and 11 villages (diere, away from the river) by delivering questionnaires in schools and by direct examinations of haematuria samples. The prevalence of haematuria varied between 0 and 33%. Generally, walos showed low rates of haematuria with the exception of Lampsar and Guede Chantier, and dieres showed higher rates of haematuria. 3. Examination of 400 cattle at the abattoir St. Louis, revealed a prevalence of 80% of schistosome infection. Two species were present, S. bovis and less commonly S. curassoni. Sometimes high worm burdens were seen, but lesions appeared to be minimal because of high ratio of male to female worms. 4. Examinations of 5722 sheep and 1752 goats in the abattoir, Dakar revealed an overall prevalence of 2.1%. Of the infected animals, 97.3% were infected with S. curassoni and 2.7% with S. curasonni and S. bovis. Laboratory snail infection experiments showed that S. curassoni is marginally compatible with B. senegalensis, but incompatible with B. guernei.

A study of the distribution of ciguatoxin in individual Caribbean fish.

Abstract: Ciguatera toxins were extracted from the tissues of 36 poisonous fishes including 9 dangerous species collected in the Caribbean. Toxicity assays were carried out in mice and the distinctive symptoms of ciguatera poisoning were observed. In a single fish, ciguatoxin was found in the blood, flesh, gonads, gills, heart, skin and bones. The concentration was highest in the viscera and in particular in the liver, kidney and spleen. The ratios of the toxin concentrations of the liver or viscera to that of the flesh were high and varied with the species suggesting that the toxin is stored in different ways in different fish. Subcellular fractionation of liver cells revealed that most of the ciguatoxin was attached to cytoplasmic proteins and that some toxin was probably bound to the membranes.

Seasonal variations in indoor resting Anopheles gambiae and Anopheles arabiensis in Kaduna, Nigeria.

Abstract: A longitudinal study in a guinea savanna area in Northern Nigeria showed that indoor resting samples consisted almost entirely of An. gambiae in the wet season, characterized by relatively lower temperature and higher relative humidity, whereas An. arabiensis predominated in the dry season, characterized by relatively higher temperature and lower relative humidity. A significant change was also observed in the frequency of polymorphic chromosomal inversions in the population of An. gambiae. The inverted arrangements 2Rbc, 2Rd and 2La were found more frequent in the dry season samples as compared to the wet season ones.

Studies on the ecology of Bulinus globosus, the intermediate host of Schistosoma haematobium in the Ifakara area, Tanzania.

Abstract: During a period of 2 years, the ecology of Bulinus globosus was studied in 8 habitats in two streams near Ifakara, SE-Tanzania. The relative Bulinus densities were followed monthly. Two different methods for estimating snail densities (man/time vs. palmleaf traps) gave comparable results. Bulinus densities were constantly low throughout the year in the stream, but they showed distinct seasonal fluctuations in adjacent pools, with a density-peak at the end of the small rainy season. B. globosus, identified by starch gel electrophoresis, was found to be the only intermediate host for urinary schistosomiasis in the investigated streams. A correlation of the Bulinus densities with several abiotic and biotic factors revealed that pH, temperature and conductivity had little effect on the Bulinus population, as they oscillated within the tolerated limits. No correlation of the distribution of B. globosus and other snail species was found. Rainfall patterns have a distinct influence on snail densities. They determine the duration of desiccation and affect the snails by fluctuations of the water level and by the fast increase of water velocity after heavy rains. B. globosus shows a clear predilection for the sedge Cyperus exaltatus as support for oviposition. It is also preferred as food and/or food-support. During the dry season, oviposition of B. globosus is concentrated in clearly defined sites ("breeding pockets"), which, due to the lowering of the water level, become isolated from the stream or retain only a small connection to it. These sites form important reservoirs of B. globosus, from where the snails are spread when the sites are flooded during the subsequent rainy season. The significance of these observations for control measures is discussed.

Trypanosomiasis 'risk' or 'challenge': a review.

Abstract: Definitions of the term 'challenge' as applied to the African trypanosomiases are reviewed. Data from one West and one East African site show simple linear relationships between the incidence of trypanosomiasis in both humans and animals, and either the amount of man-tsetse contact, or the Apparent Density of flies. Data from a number of East African sites are analysed and show a linear relationship between the mean Berenil Index of cattle and the logarithm of the challenge, where challenge is the simple product of Apparent Density and mean fly infection rate. Apparent Density is a more variable element of total challenge than is infection rate. The results of field studies are analysed to show that Berenil has a short prophylactic effect, lasting for about 22 days in cattle. When allowance is made for this effect there is a direct, apparently linear relationship between the daily probability of infection of cattle and total challenge, the latter varying over almost three orders of magnitude. Variations in tsetse fly density account for about 50% of the variability of Apparent Density. Hence the latter is a crude estimate of the former. Seasonal and density-related changes in the availability of flies to human catchers could account for the inadequacies of the fly-round technique in assessing fly density and/or challenge. Evidence at present available suggests that trypanotolerant cattle are more likely to be an economic alternative to drug-treated zebu at higher rather than lower challenge levels. Whether either type of animal could profitably be raised in areas of the highest challenge and without some form of tsetse control remains an open question.

In vitro cultivation of Trypanosoma congolense: the production of infective forms from metacyclic trypanosomes cultured on bovine endothelial cell monolayers.

Abstract: After transfer to bovine endothelial cell monolayers cultured in Eagle's minimal essential medium at 28 degrees C or 37 degrees C metacyclic trypanosomes of three cloned stocks of Trypanosoma congolense became morphologically similar to parasites found in the bloodstream of the vertebrate host The trypanosomes resumed division and grew in close association with the mammalian cells, which were essential for growth These dividing infective forms had the ability to cause local skin reactions and systemic infections when inoculated intradermally into rabbits Trypanosomes grown in medium supplemented with foetal calf serum (FCS) eventually differentiated into procyclic forms No such change occurred in medium supplemented with normal bovine serum If procyclic forms in FCS were allowed to continue their differentiation at 28 degrees C they eventually produced epimastigotes which gave rise to infective metacyclic trypanosomes once more It was thus possible to grow and maintain several different developmental stages of T congolense by varying culture conditions

Antibody response to experimental Trypanosoma rangeli infection and its implications for immunodiagnosis of South American trypanosomiasis.

Abstract: Differential immunodiagnosis of T. rangeli and T. cruzi infections in man poses a particular problem, not only because these parasites share antigenic determinants, as detected by immunofluorescence, but also because they have a similar geographical distribution, the same host range and often identical insect vectors. We show here that whereas mouse anti-T. rangeli sera have significant cross reactivity with T. cruzi by immunofluorescence, they are entirely specific when tested by ELISA, using apparently similar antigen preparations. Immunoprecipitation analysis detected relatively little cross-reactivity between heterologous antisera and parasite combinations. Intriguingly, immunization with T. rangeli epimastigotes was much more powerful than similar immunization with trypomastigotes, and the majority of the antibody was directed against a single polypeptide of apparent Mr 73kDa.

Pentastomiasis: case report of an acute abdominal emergency.

Abstract: A 34-year-old native women presented as an acute abdominal emergency at the Surgery Department, Missionary Hospital "Ad Lucem" in Banka-Bafang, Cameroon. She complained of colicky, epigastric abdominal pain, nausea, vomiting, constipation, and retention of flatus. At laparotomy, numerous small cystic nodules (3-8 mm in diameter) were noted in the mesentery and under the intestinal and parietal peritoneum. Histological examination of two of them revealed slightly enlarged mesenteric lymph nodes containing several parasitic pseudocysts. The parasites were diagnosed as well-preserved, encysted, Armillifer armillatus nymphs. Neither degenerative nor inflammatory granulomatous reactions were observed in the adjacent tissue. Two and a half years later, a similar attack of acute abdominal symptoms recurred. A radiological examination revealed several C-shaped or circular, dense opacities characteristic of calcified pentastomid nymphs. At laparotomy, local findings similar to those at the previous surgical examination were noted. Additionally, a few firm, whitish, calcified nodules were found in the mesentery and under the fibrous capsule of the liver.

Chick feeding test: a simple system to detect ciguatoxin.

Abstract: Chick poisoning induced by oral administration of toxic fish tissues or extracts gave rise to internal hypersalivation, decrease in weight and acute motor ataxia. Detoxification was low and repeated administration therefore led to toxin accumulation. Response of the chicken to liver feeding was roughly quantitative; so liver, which is the most potential toxic tissue, may be used for a preventive screening test in ciguatera-endemic areas.

Preliminary data on the genetic differentiation of Onchocerca volvulus in Africa (Nematoda: Filarioidea).

Abstract: Data are reported on the genetic structure of three Onchocerca volvulus populations, respectively from Mali (savanna), Ivory Coast (forest), and Zaire (forest gallery in savanna). Electrophoretic analysis, carried out on 25 gene-enzyme systems, has shown a remarkable genetic heterogeneity existing within O.volvulus. Zaire and West Africa populations appear chiefly differentiated at Mdh-1 and 6Pgdh loci, their average Nei's genetic distance being 0.11. In West Africa Nei's D found between the savanna and forest samples is 0.04. The savanna population from Zaire is more similar to the savanna one from Mali (D = 0.09) than to the forest one from Ivory Coast (D = 0.13). This appears mainly due to the loci Ldh and Hbdh (possibly linked), some alleles of which seem to be selected for in forest populations (Ldh110, Hbdh108), while others in the savanna ones (Ldh100, Hbdh100). The hypothesis that the discrepant epidemiological patterns of human onchocerciasis are related to intrinsic differences in the parasite seems supported by the obtained data. The differences in allele frequencies found at the reported loci appear strong enough to allow biochemical identification of O. volvulus populations from different geographic regions and different habitats.

A study of the biological characteristics of a hybrid line between male Schistosoma haematobium (Dar es Salaam, Tanzania) and female S. intercalatum (Edea, Cameroun).

Abstract: The viability of a hybrid between male Schistosoma haematobium (Dar es Salaam, Tanzania) and female S. intercalatum (Edea, Cameroun) was studied for up to the F7 hybrid generation and the biological characteristics of the hybrid were compared with those of each of the parental species. Using the total cercarial production/100 exposed snails/5 weeks value (TCP) as an index the hybrid miracidial infectivity to Bulinus forskalii (Kinshasa, Zaire), the host snail for S. intercalatum, remained comparable to that of S. intercalatum for up to at least the F5 generation and the TCP values for the hybrid/B. wrighti combination remained for up to the F7 generation intermediate between those of the parental species in B. wrighti. The hybrid also retained the infectivity for up to at least the F5 generation to B. globosus (Mazeras, Kenya), the host snail for S. haematobium, but the TCP values for the hybrid/B. globosus combination remained consistently lower than that of the S. haematobium/B. globosus combination. The hybrid cercarial infectivity to hamsters was for up to the F7 generation comparable to that of both parental species and the egg production capacity/worm pair/day of production of the F1 hybrid generation exceeded in both hamsters and mice that of both parental species. However, the egg production capacity subsequently decreased with that of the F3 to F6 generations in hamsters and with that of the F2 and F5 generations in mice being comparable to that of S. intercalatum. The pattern of distribution of eggs in tissue of hamsters of the F1 and F2 generations resembled that of S. haematobium and S. intercalatum, respectively, but the distributional pattern of the F3 to F6 generations deviated markedly from that of both the parental species and the preceding hybrid generations. The hybrid cercarial infectivity to mice and the pattern of egg distribution corresponded to that of S. intercalatum. The egg morphology of the P1 generation corresponded to that of S. intercalatum while that of the F1, F2 and F3 hybrid generations exhibited great polymorphism with a range of shapes through those of the parental species but with most eggs being intermediate in shape. However, the eggs of the F4 to F7 hybrid generations exhibited less polymorphism and resembled those of S. bovis in both size and shape.

Differential pathogenicity of Brugia malayi, B. patei and B. pahangi in immunodeficient nude mice.

Abstract: Immunodeficient nude mice chronically parasitized by subperiodic Brugia malayi developed an elephantoid appearance with persistent lymphoedema of limbs and massive lymphangiectasis of subcutaneous vessels containing viable adult worms. Removal of worms reversed the process. The syndrome was not caused by B. patei or B. pahangi and was not correlated with the presence or absence of microfilaremia. Histologic examination of elephantoid mice revealed dilated and tortuous lymphatics containing small nonobstructive lymph thrombi composed of small mononuclear cells and multinucleate giant cells. Draining lymph nodes were not enlarged or congested and mast cells in oedematous tissue were not degranulated. Analysis of lymph aspirated from dilated lymphatics showed increased total protein content: bacterial sepsis was not detected. This work suggests that viable adult B. malayi exert direct pathologic effects upon lymphatics and that this parasite is more pathogenic than related Brugia spp.

In vitro cultivation of Trypanosoma congolense: establishment of infective mammalian forms in continuous culture after isolation from the blood of infected mice.

Abstract: Bloodstream form trypomastigotes of four cloned stocks of Trypanosoma congolense from West Africa were successfully adapted to continuous in vitro culture at 28 degrees C using bovine aorta endothelial cell monolayers and Eagle's minimum essential medium supplemented with 20% normal bovine serum or foetal calf serum. The trypanosomes maintained in vitro morphologically resembled bloodstream forms and remained infective for vertebrate hosts. They also induced local skin reactions in rabbits and were therefore designated "mammalian forms", possibly resembling parasites which develop extravascularly in the vertebrate host following introduction of metacyclic trypanosomes into the skin by bites of tsetse flies. Mammalian forms of two stocks were allowed to transform to procyclic trypanosomes in order to obtain cultures producing epimastigote and metacyclic stages of T. congolense. Metacyclic trypanosomes produced in this manner were shown to be neutralized by antiserum raised in rabbits against the homologous trypanosome stock transmitted by tsetse flies.

A new defined medium for cultivating Leishmania promastigotes.

Abstract: A chemically defined medium to grow the promastigotes of 19 stocks of Leishmania is described. The medium was developed by making qualitative and quantitative modifications of the medium AR-103 devised for Trypanosoma cruzi. The new medium, designated as MD-29, can be used in studies on the nutritional requirements of promastigotes.

Urban transmission of urinary schistosomiasis in Dar es Salaam, Tanzania.

Abstract: A cross sectional survey for Schistosoma haematobium infections was undertaken in 12 primary schools in the city of Dar es Salaam. The prevalence in the schools ranged from 5.3 to 55.1%, with an overall prevalence of 19.3%. More males (23.5%) than females (15.0%) were infected, and the highest prevalence was recorded in the 11-16 year age group. Intensity of infection was high, ranging from 12 to 96 eggs/10 ml urine in individual schools. 26% of the infected excreted more than 50 eggs/10 ml urine, and high rates of haematuria and proteinuria were observed in infected children. Interviews indicated that the majority of the children had acquired their infection in the city. Malacological surveys showed two potential vectors, Bulinus (Physopsis) globosus and B. (Ph.) nasutus, to be common in Dar es Salaam. Laboratory and field findings confirmed that these two species were vectors of S. haematobium. Factors responsible for continued transmission in this urban environment are discussed.

Activation of the alternative complement pathway in normal human serum by Loa loa and Brugia malayi infective stage larvae.

Abstract: Infective stage larvae (L3) of Loa loa and Brugia malayi upon in vitro incubation with normal human serum activated the alternative complement pathway. C3 conversion products were detected on larval cuticles by eosinophil adherence and by immunofluorescence with C3c antiserum. No evidence for cuticle binding of IgG, IgA, IgM, Clq, or C4 was found by immunofluorescence. L3-induced C3 activation was inhibited by 10 mM EDTA but unaffected by 10 mM Mg++-EGTA. Human sera deficient in C2, C4, or C6 incubated with L3 resulted in C3 activation. However, sera treated with zymosan or heated for 1 h, 56 degrees C were unreactive with L3. Immunoelectrophoresis of fresh serum exposed to L3 for 1 h at 37 degrees C showed C3 cleavage products. The results indicate that these nematode L3 activate the alternative complement cascade via cuticular surface components. Larval viability was unaffected by complement activation or by adherence of eosinophils.

The probability of tsetse acquiring trypanosome infection from single blood meal in different localities in Kenya.

Abstract: The probability of tsetse, Glossina pallidipes, acquiring a trypanosome infection from a single blood meal was estimated in five localities on the Kenya coast which were selected for differences in habitat and host availability. The probability that one blood meal contained infective Trypanosoma congolense was 0.0077 in rural areas with domestic animals, 0.0019 in extensive areas of natural habitat with wild hosts and 0.0013 in an area with domestic animals under regular chemoprophylaxis. The respective probabilities for T. vivax were 0.0010, 0.0024 and 0.0021.

In vitro activity of the trypanocidal diamidine DAPI on animal-infective Trypanosoma brucei brucei.

Abstract: A mammalian feeder layer system for the continuous cultivation of infective bloodstream forms of Trypanosoma brucei brucei has been used for investigating the antitrypanosomal activity of the aromatic diamidine DAPI. The drug was active at concentrations which can be reached under physiological conditions. The minimum effective concentration was 0.05 micrograms/ml. Minimum exposure times required for antitrypanosomal activity were dependent on the drug concentrations. Furthermore, DAPI was found to cause toxic side effects on bovine fibroblast feeder layer cells at high drug concentrations (10 micrograms/ml), however, at low concentrations (1 microgram/ml), the drug acted selectively on trypanosomes. Both the reproducibility and the high sensitivity to drugs of the system make this assay a valuable technique for chemotherapeutic studies on trypanosomes.

Adsorption of Trypanosoma cruzi proteins to mammalian cells in vitro.

Abstract: It has previously been shown using immunological techniques that antigens from Trypanosoma cruzi adsorb to mammalian cells. Here we have used radioactively-labelled T. cruzi antigens to investigate the nature of the antigens bound. We have demonstrated that numerous T. cruzi polypeptides rapidly become adsorbed to mammalian cells in tissue culture. These polypeptides dissociate from the mammalian cells only at a slow rate. We found no indication that the binding of the polypeptides was mediated by the specific binding of any one protein.

Experimental infection of the domestic donkey (Equus asinus asinus) with a goat strain of Sarcoptes scabiei, and treatment with ivermectin.

Abstract: Donkeys were experimentally infected with Sarcoptes scabiei from goats, proving that this mite is not completely host specific. The lesions produced on the donkeys were characterized by extensive areas of alopecia, covered with thin crusts and bran-like scales. The skin had many excoriations but showed no cracks or fissures. Skin scrapings from the experimental lesions in donkeys contained numerous mites of all stages and skin sections showed severe histopathological changes, proving that the goat mites had become well established and were reproducing actively in experimental lesions. Treatment of the donkeys with ivermectin produced excellent and rapid cure.

Pharmacological studies on Salvia haematodes Wall.

Abstract: The aqueous extract of the root of Salvia haematodes has been investigated for its pharmacological actions on the cardiovascular and central nervous system. It was found to possess significant cardiotonic and anticonvulsant activities. It was not found toxic up to the dose of 5 g/kg given orally in order to evaluate its acute toxicity.

Site of resistance to Necator americanus in hamsters.

Abstract: Resistance to the development of human hookworm, Necator americanus was examined in 3- to 6-week-old young adult hamsters. Only 3% of N. americanus infective third stage larvae (NaL3) reached maturity in the intestines of young adults as opposed to as many as 60% in 2-day-old baby hamsters. This seemingly effective resistance prevailing in young adults was investigated in some detail. The skin, the first site of contact for the invading NaL3, was bypassed during the infection process. Completely in vitro exsheathed NaL3 (ExNaL3) were used, and young adult hamsters were infected parenterally, by-passing the skin. Even after exsheathing the larvae artificially before infection and by-passing the skin, no improvement was seen in the development of N. americanus in the intestines of young adults. Higher infection doses also did not increase the worm burden. Some of the factors limiting the development of parasites in young adults were examined. N. americanus were monitored in lungs and intestines during various intervals after infection. Similar parasite burdens were apparent in lungs of baby as well as young adult hamsters. In the intestines, a significantly lower burden of N. americanus was seen during various intervals in young adults compared to the baby hamsters. Moreover, N. americanus were expelled soon after reaching the intestine. This comparative monitoring revealed the intestine as the seat of resistance against the establishment of N. americanus in young adult hamsters.

Peripheral lymphadenopathy in Nigeria.

Abstract: An analysis of 294 enlarged peripheral lymph node biopsies in Ife, Nigeria, revealed that the underlying disease in 51.7% was chronic inflammation while malignant diseases accounted for 48.3%. The order of frequency of the lesions was reactive hyperplasia (29.3%), metastatic cancer (24.5%), malignant lymphoma (23.8%), tuberculosis (15.6%) and toxoplasmosis (3.7%). One-third of the metastases were of undetermined origin. The neck which accounted for 53% of the biopsies, was the most frequent site for tuberculous adenitis, toxoplasmic lymphadenitis, and malignancies. The axilla was involved in 15% of the cases and was the most common site for metastatic breast carcinoma. The inguinal lymph nodes were also involved in 24% of the cases and had the highest occurrence of melanoma, reactive hyperplasia and parasitic granuloma. The habit of bare-foot walking leading to repeated trauma and infection is implicated in the high incidence of inguinal node reactive hyperplasia. This study demonstrates that lymph node malignancies and chronic granulomatous infections present a problem of increasing diagnostic and therapeutic importance and furthermore, it emphasizes that physicians in Nigeria should consider toxoplasmosis in the differential diagnosis of peripheral lymphadenopathy.

Determination of the trypanocidal drugs homidium, isometamidium and quinapyramine in bovine serum or plasma using HPLC.

Abstract: Sensitive HPLC analytical methods for trypanocidal drugs in serum or plasma have been developed. The methods are suitable for the analysis of drugs that are widely used against animal trypanosomiasis at present, including Homidium bromide (Ethidium, Boots Company Ltd.), Homidium chloride (Novidium, May and Baker Ltd.), Isometamidium chloride (Samorin, May and Baker Ltd.), Quinapyramine chloride (Antrycide, ICI) and Quinapyramine sulphate (Trypacide, May and Baker Ltd.). The detection limits for various drugs range between 3 and 20 ng per ml of serum, when serum volumes up to 10 ml have been processed. These methods provide a significant improvement of sensitivity for Isometamidium over existing analytical procedures and represent new methods for analysis of Homidium and Quinapyramine.

Influence of the salmon mutant of Glossina morsitans morsitans on the susceptibility to infection with Trypanosoma congolense.

Abstract: Four phenotypes of a sex-linked, maternally influenced semi-lethal eye color mutant of Glossina morsitans morsitans Westwood were fed on Trypanosoma congolense Broden infected guinea pigs. Infection rates were evaluated 25 days later by means of dissection. Procyclic as well as mature infections were significantly more common among females with salmon-colored eyes (sal/sal) than among heterozygous (+/sal, phenotypically wild-type) females. A tendency was found for more mature infections among sal/Y males than among wild-type males. Similarly, females tended to be more infected than males with both procyclic and mature infections. These results indicate that the genotype of the fly, exemplified by the allele salmon, might influence the development of T. congolense in G.m. morsitans. A possible explanation for this phenomenon is discussed.

Trypanosoma cruzi amastigotes: development in vitro and infectivity in vivo of the forms isolated from spleen and liver.

Abstract: Trypanosoma cruzi amastigotes were isolated from liver and spleen of previously infected mice and purified in discontinuous gradients of Metrizamide and Percoll. The amastigotes were well preserved as judged by electron microscopy. The amastigotes were readily interiorized by macrophages and multiplied actively within these cells in vitro. However, their capacity of differentiation was hampered as estimated by the absence of trypomastigotes until day 6 of cultivation. The purified amastigotes were infective for mice but the onset of parasitemia was somewhat delayed and less intense when compared to mice infected with trypomastigotes.

Effect of vector on infectivity of Trypanosoma cruzi.

Abstract: A comparative study was carried out on the interaction between Triatoma infestans and bloodstream forms (BSF) of Trypanosoma cruzi isolates RA and UP, both lethal for mouse, and CA-I nonlethal for this host. Parasite duplication was readily detected in triatomes fed with CA-I, metacyclic (Mtc) differentiation reaching a maximum at an optimum ingestion level of 250 BSF/insect. Progress and differentiation proved much lower for RA, but reached intermediate values for the UP isolate. Assays for infectivity for each isolate after bug passage revealed a drop for the RA and UP, whereas for CA-I an increase was observed indicating that virulence of BSF and Mtc differs. Our results suggest that parasite selection by insect passage modulates infectivity of a given parasite population; however, virulence was independent of the absolute number of Mtc in the insect's feces.