Infection of white rat peritoneal macrophages with Toxoplasma gondii, (Coccidia: Sarcocystidae) after Trypanosoma lewisi (Kinetoplastida: Trypanosomatidae) infection

Peritoneal macrophages from Wistar rats, inoculated and non-inoculated with 10(6) T. lewisi trypomastigotes, were cultured and infected with 10(6) T. gondii tachyzoites. Multiplication rates of this parasite were studied after 1, 24 and 48 h of infection but there were not significant differences between the number of parasites found inside of macrophages coming, either from T. lewisi infected or non infected rats. On the other hand, in vivo studies of Toxoplasma multiplication inside peritoneal macrophages, showed that there is an increase of parasite number in cells from T. lewisi infected rats, as compared with those macrophages from non infected rats. This effect was statistically significant and was more evident after four days of infection. Therefore, it has been demonstrated that in vivo, but not in vitro T. lewisi infections, causes an important decrease of the natural resistance to T. gondii of the white rats, which is manifested by the major invasion and multiplication of the parasite inside of peritoneal macrophages.     

Rat liver glucose-6-phosphate dehydrogenase isozymes: influence of infection with Trypanosoma

Glucose-6-phosphate dehydrogenase (G6PD) changes were studied in livers of rats inoculated with Trypanosoma lewisi, Trypanosoma rhodesiense, Trypanosoma congolense and Trypanosoma brucei. Marked increases in G6PD were directly related to the degree of parasitemia. No essential differences in G6PD levels were seen in animals inoculated with physiological saline when compared with uninoculated controls. Elevation of G6PD was observed only from day 10 to 20 in rats inoculated with T. lewisi. After day 20, the G6PD levels were not statistically significant from those of uninoculated controls. Liver G6PD levels were increased as early as day 3 post-inoculation and continued up to the time of death in rats inoculated with T. brucei, T. rhodesiense and T. congolense.     

Iron metabolism in Trypanosoma lewisi infection: serum iron and serum iron-binding capacity.

Progressive changes in iron levels, total iron binding capacity and hematocrit values in sera of rats infected with Trypanosoma lewisi are described. The host dietary group were: (1) complete or full complement; (2) iron-deficient, and (3) pair-fed or calorically restricted. The hematocrit values of T. lewisi-infected rats given the various diets were not significantly different from those of the controls. The decrease in total iron binding capacity (TIBC) of rats inoculated with T. lewisi and fed complete and pair-fed diets ranged up to 15% over uninfected controls. TIBC levels in rats fed an iron-deficient diet and inoculated with T. lewisi ranged up to 32% over uninfected controls. TIBC levels of deficient infected rats were significantly different from the controls from day 90 to infection to the end of the observation period. Serum iron (SI) values of non-infected rats regardless of dietary regimen showed significantly higher values than T. lewisi-infected animals between days 95 and 120. The average SI value, for this period, in adequately fed control rats was 204 +/- 7 microgram/100 ml as compared to 172 +/- 5 microgram/100 for trypanosome-infected rats. SI levels of rats on a pair-fed diet and infected with T. lewisi decreased to 17% over uninfected controls. SI levels of animals on an iron-deficient diet and infected with T. lewisi decreased up to 76% over uninfected controls.     

Prevalence of Trypanosoma lewisi in Rattus norvegicus from Belo Horizonte,State of Minas Gerais,Brazil

From April 1984 to March 1985, a Trypanosoma lewisi prevalence of 21.7% was found in 429 Rattus norvegicus trapped in Belo Horizonte, State of Minas Gerais, Brazil. The infection rates were higher in male and young rats and could be attributed to ecological and behavioral factors. T. lewisi was observed in rats measuring between 60 and 250 mm. Data about monthly T. lewisi infections throughout the year are presented for the first time in Brazil, with the highest prevalences observed in the warm-rainy season (October to March).     

室内条件下莱氏猛叩甲对松墨天牛和黄粉虫的捕食能力

【目的】本研究旨在明确莱氏猛叩甲Tetrigus lewisi老熟幼虫分别对黄粉虫Tenebrio molitor和松墨天牛Monochamus alternatus末龄幼虫和蛹的捕食量的差异,评估莱氏猛叩甲的捕食能力,为松墨天牛M.alteratus的有效治理找到潜在的高效生物防治因子。【方法】于2014年11月在浙江富阳昌东村马鞍山砍下松墨天牛虫害木,通过林间野外调查,明确松墨天牛和莱氏猛叩甲的发生情况;将野外采集到的莱氏猛叩甲幼虫带回室内,分别饲喂黄粉虫和松墨天牛的末龄幼虫和蛹,每天记录捕食量,确定莱氏猛叩甲的捕食能力。【结果】野外调查中,我们在松墨天牛幼虫蛀食的坑道中发现了莱氏猛叩甲幼虫和松墨天牛幼虫被取食后的残体;在采集到1 094头松墨天牛幼虫的危害木内,共采得莱氏猛叩甲末龄幼虫36头,约为松墨天牛幼虫数量的3%。室内捕食实验表明,5 d内莱氏猛叩甲捕食黄粉虫幼虫总量为3.2头,平均每天捕食约0.6头,而捕食松墨天牛幼虫总量为8.0头,平均每天捕食约1.6头,莱氏猛叩甲对松墨天牛的总捕食量显著高于对黄粉虫幼虫的总捕食量(P0.0001);4 d内莱氏猛叩甲捕食黄粉虫蛹总量为5.6头,平均每天捕食约1.4头,而捕食松墨天牛蛹总量为7.8头,平均每天捕食约2.0头,莱氏猛叩甲对松墨天牛蛹的捕食量显著高于黄粉虫蛹(P=0.028)。回归分析还表明,莱氏猛叩甲幼虫的捕食量不受叩甲个体大小的影响。【结论】莱氏猛叩甲普遍分布在松墨天牛发生区,同时发现松墨天牛被取食后的残体,表明莱氏猛叩甲是松墨天牛的捕食性天敌。莱氏猛叩甲均能捕食黄粉虫和松墨天牛的幼虫和蛹;相比于捕食黄粉虫,莱氏猛叩甲对松墨天牛的幼虫和蛹具有更好的捕食效率,具有很好的生物防治前景,是未来松墨天牛治理潜在高效生物防治因子。     

Trypanosoma lewisi-induced immunosuppression: the effects on alveolar macrophage activities against Cryptococcus neoformans

The immunosuppressive effect of Trypanosoma lewisi infection on alveolar macrophage (AM) activities against Cryptococcus neoformans was studied in an animal model. Two groups of rats were treated with T. lewisi and killed after 4 (4d-rats) and 7 days (7d-rats), respectively. A third group not given T. lewisi, served as control. AM were challenged in vitro with C. neoformans. Phagocytosis was assessed with a fluorescence method. Superoxide anion production was evaluated with the nitroblue tetrazolium (NBT) test. The survival of cryptococci was estimated by counting colony-forming units. The numbers of detached AM from culture plates were determined using a Bürker chamber. The NBT response, adhesion to plate surface and killing activity, but not the phagocytosis of AM from 4d-rats were significantly impaired compared to control or 7d-rats. Thus, T. lewisi causes transitory immunosuppressive effects on AM activities. This rapid T. lewisi immunosuppression model may be useful to study new approaches to anticryptococcal therapy.     

Trypanosoma lewisi Infections in Normal Rats and in Rats Treated with Dexamethasone

SYNOPSIS. Administration of dexamethasone to rats infected with Trypanosoma lewisi resulted in the development of exceedingly large populations of trypanosomes which were fatal to their hosts. The elevated levels of parasitemia in treated rats early in infections were thought not to be a result of an increased reproductive rate. However, trypanosomes in treated rats 2 days postinfection did have a higher coefficient of variation in total length and a greater percentage of dividing forms than those observed from infected rats which were not given the drug. The course of infection may be markedly altered not only in intensity but also in length by this corticosteroid. It is suggested that dexamethasone administered at the levels recorded to rats infected with T. lewisi inhibits the production of ablastin and trypanocidal antibodies.     

Effect of Holothurin on Trypanosoma lewisi Infections in Rats

SYNOPSIS. Crude holothurin from the Bahamian sea cucumber Actinopyga agassiz , inoculated intraperitoneally into rats with Trypanosoma lewisi infection, altered the host-parasite relationship. The effect was measured by a study of parasite population during infections. Rats treated with holothurin prior to and simultaneously with an infection of trypanosomes had lower parasitemias than controls. A higher level of parasitemia was observed in treated after infection with trypanosomes. Both dosage and timing appeared to have been important parameters of the observed effect. The reticuloendothelial system is suspected to play a role in these findings.     

Antibody to fibrinogen/fibrin products (Anti-F) in malaria, babesiosis, and trypanosomiasis of rodents.

Antibody to fibrinogen/fibrin related products (Anti-F) was stimulated during the course of Plasmodium chabaudi, Babesia rodhaini, and Trypanosoma lewisi infections in rats. Titers of this autoantibody remained elevated in serum from rats that had recovered from each of the infections. Column chromatographic studies indicated that Anti-F was a 19S globulin, possibly IgM. During acute infections high titers of Anti-F were associated with elevated titers of cold-active hemagglutinin (CAH) and immunoconglutinin (IK) and all were associated with anemia and elevated parasitemia. Titers of Anti-F and IK, but not CAH, remained elevated in serum of recovered rats. The presence of Anti-F indicated that the coagulation system had been activated during each infection to release fibrinogen/fibrin-related products (FRP) to serve as antigen(s) for Anti-F. Since IK is antibody to the third component of fixed complement, it could be assumed that complement fixing antigen-antibody complexes were also present during the acute stage of each infection. The possibility that complexes of FRP and Anti-F could have contributed to anemia in each infection is discussed.     

Infection by trypanosomes in marsupials and rodents associated with human dwellings in Ecuador

Small mammals trapped in domestic and peridomestic environments of rural Ecuador were screened for trypanosome infection by direct microscopy and hemoculture. Identification of species of trypanosomes was then performed by morphological characteristics and by polymerase chain reaction (PCR) assays. Of 194 animals collected, 15 were positive for infection (7.73%). Eight (4.12%) were infected with Trypanosoma cruzi (1 of 33 Didelphis marsupialis; 7 of 61 Rattus rattus). Eleven R. rattus (18.03%) harbored T. lewisi, 5 of which presented mixed infections with T. cruzi. Additionally, 1 of 3 Oryzomys xanthaeolus was infected with T. rangeli. No trypanosome infection was detected in Philander opossum (n = 1), Mus musculus (n = 79), Rattus norvegicus (n = 8), Akodon orophilus (n = 4), Sigmodon peruanus (n = 3), or Proechimys decumanus (n = 2). Many of the isolates belong to T. cruzi, the causative agent of Chagas disease, and R. rattus had the highest prevalence. Because of its abundance in the study areas, this species is considered an important reservoir for Chagas disease. This is the first report of T. lewisi and T. rangeli in Ecuador. This study is also the first to describe natural mixed infections of T. cruzi-T. lewisi.     

Susceptibility of spiny rats (Proechimys semispinosus) to Leishmania (Viannia) panamensis and Leishmania (Leishmania) chagasi

The role of Proechimys semispinosus as reservoir of Leishmania (Viannia) panamensis on the Colombian Pacific coast was experimentally evaluated. The susceptibility to L. chagasi also was assessed to determine the utility of this rodent as a model for studying reservoir characteristics in the laboratory. Wild-caught animals were screened for natural trypanosomatid infections, and negative individuals were inoculated intradermally (ID) in the snout or feet with 10(7) promastigotes of L. panamensis. L. chagasi was inoculated intracardially (10(7) promastigotes) or ID in the ear (10(8) promastigotes). PCR-hybridization showed that 15% of 33 spiny rats were naturally infected with L. Viannia sp. Animals experimentally infected with L. panamensis developed non-ulcerated lesions that disappeared by the 7th week post-infection (p.i.) and became more resistant upon reinfection. Infectivity to sand flies was low ((1/2)0-(1/4)8 infected/fed flies) and transient, and both culture and PCR-hybridization showed that L. panamensis was cleared by the 13th week p.i. Animals inoculated with L. chagasi became subclinically infected and were non-infective to sand flies. Transient infectivity to vectors of spiny rats infected with L. panamensis, combined with population characteristics, e.g., abundance, exploitation of degraded habitats and high reproductive rates, could make them epidemiologically suitable reservoirs.     

Experimental congenital toxoplasmosis in Wistar and Holtzman rats

Congenital toxoplasmosis was evaluated in Wistar and Holtzman rats using two strains of Toxoplasma gondii isolated in Brazil. Pregnant rats were inoculated by subcutaneous or intraperitoneal routes with 10(6) or 8 x 10(6) tachyzoites of N strain (virulent for mice) and by subcutaneous or oral routes with 10(2) or 1.2 x 10(3) cysts of P strain (avirulent for mice). The tissues of rat pups born from these rats were bioassayed for T. gondii infection. T. gondii was not observed in the pups born from rats inoculated with N strain. In the animals inoculated with P strain, congenital toxoplasmosis occurred in 22.8% (Wistar rats inoculated with 10(2) cysts by the subcutaneous route), 11.4% (Wistar rats inoculated with 10(2) cysts by the oral route), 21.2% (Wistar rats inoculated with 1.2 x 10(3) cysts by the oral route) and 2.9% of fetal infection (Holtzman rats inoculated with 10(2) cysts by the oral route). None of the pups born from chronically infected mother were infected with T. gondii.     

Elicitation of the reproduction-inhibiting antibody ablastin by serum exoantigens of Trypanosoma lewisi

Serum exoantigens of Trypanosoma lewisi were collected 5 days after infection from immunocompetent (untreated) rats and rats immunosuppressed by treatment with either hydrocortisone acetate or dexamethasone. Normal rats were then immunized with pooled, whole exoantigen-containing serum from 1 of these 3 sources plus alum as an adjuvant, and the immune sera produced were tested individually. All contained agglutinating (trypanocidal) antibodies to both antigenic variants of T. lewisi, but only about two-thirds showed precipitating activity with exoantigens in gels. More importantly, however, when these antisera were thoroughly adsorbed with living trypanosomes (from immunocompetent hosts) to remove agglutinating antibody only and then tested for ablastic activity in vitro, all showed significant (P less than 0.01) reproduction-inhibiting activity, comparable to that shown by ablastic serum collected from rats that experienced a natural infection. Antisera from control rats similarly immunized with normal rat serum were negative in all antibody tests. The exoantigens of T. lewisi are, therefore, a complex mixture of immunogens that are related to the known immune responses to the parasite and can elicit the formation of ablastic antibody with the same biological properties as that produced during a natural infection.     

Trypanosoma (Megatrypanum) saloboense n. sp. (Kinetoplastida: Trypanosomatidae) parasite of Monodelphis emiliae (Marsupiala: Didelphidae) from Amazonian Brazil

Trypanosoma (Megatrypanum) soloboense n. sp., is described in the Brazilian opossum Monodelphis emiliae (Thomas, 1912) from primary forest in the Salobo area of the Serra dos Carajás (6 degrees S, 50 degrees 18' W) Pará State, North Brazil. Two morphologically different trypomastigotes were noted. Slender forms, regarded as immature parasites, have a poorly developed undulating membrane adhering closely to the body: large, broad forms with a well developed membrane are considered to be the mature trypomastigotes and have a mean total length of 71.2 microm (62.4-76.2) and a width of 6.1 (5.0-8.0). Infections studied in two opossums were of very low parasitaemia. The large size of T. (M.) saloboense readily distinguishes it from the two previously described members of the subgenus Megatrypanum of neotropical marsupials, T. (M.) freitasi Régo et al., 1957 of Didelphis ozarae and D. marsupialis, and T. (M.) samueli Mello, 1977 of Monodelphis domesticus, which measure only 49.0-51.5 microm and 42.4 microm respectively. No infections were obtained in hamsters inoculated with triturated liver and spleen from one infected M. emiliae, or in laboratory mice inoculated with epimastigotes from a blood-agar culture. No division stages could be detected in the internal organs or the peripheral blood.     

Trypanosoma lewisi: stage-specific surface antigens and exoantigens recognized by monoclonal antibodies

The stage-specific expression of surface antigens by Trypanosoma lewisi was investigated using monoclonal antibodies directed against this parasite. Hybridomas secreting monoclonal antibodies were produced by the fusion of SP2/0-Ag 14 mouse plasmacytomas with spleen cells from rats infected previously with the Taliaferro strain of T. lewisi. Additivity enzyme-linked immunosorbent assays and indirect immunofluorescent antibody tests indicated the determinant recognized by monoclonal antibody TL40.3 (IgM) was different from those recognized by monoclonal antibodies TL40.1 (IgA), TL40.2 (IgM), and TL40.6 (IgG2 alpha). Monoclonal antibody TL40.3 agglutinated trypanosomes collected 3 days after parasite inoculation while monoclonal antibodies TL40.1, TL40.2, and TL40.6 agglutinated trypanosomes collected 6 days after inoculation. Since agglutinin titers against trypanosomes from irradiated (700 rad from a 60Co source) and nonirradiated rats were similar, expression of the antigens recognized by the monoclonal antibodies appeared to be independent of the immunological state of the host and the morphology of the parasite. The reproduction of T. lewisi in in vitro trypanostatic assays was inhibited only when the monoclonal antibodies were present in concentrations greater than or equal to those needed to agglutinate the trypanosomes. Monoclonal antibodies TL40.1 and TL40.3, but not TL40.2 and TL40.6, agglutinated erythrocytes collected later in the infection from irradiated, infected rats. None of the monoclonal antibodies agglutinated erythrocytes from nonirradiated, infected rats, from irradiated, noninfected rats or from nonirradiated, noninfected rats. This suggests that immunocompetent rats may make blocking antibodies against the exoantigens recognized by monoclonal antibodies TL40.1 and TL40.3.     

Flow cytometric analysis of immunoglobulin and complement component C3 on the surface of Trypanosoma lewisi

We have reinvestigated whether surface immunoglobulin (sIg) on Trypanosoma lewisi is antibody directed toward parasite antigen by using flow cytometry to analyze parasites stained with fluoresceinated F(ab')2 fragments of antibodies to rat IgG and IgM. We have confirmed that IgG antibody to the parasites is present both in the serum of rats and on the surface of parasites between the fourth and twentieth days of infection, that the amount of sIg per cell increases as the infection progresses, and that considerably more IgG is present on parasites harvested from intact rats than on those from rats that had been immunosuppressed by whole body gamma-irradiation. In addition sIgM was detected on trypanosomes from intact, but not on parasites from irradiated rats. We have also made two observations suggesting that not all sIg is specific antibody made in response to T. lewisi. First, a low but significant amount of sIgG was detected on parasites throughout infection in irradiated rats; no sIgM was detected on these parasite. Second, when parasites harvested from immunosuppressed rats were incubated in normal rat serum, the amount of both sIgG and sIgM detected by flow immunofluorescence increased. Parasites harvested from intact animals bound IgM but not IgG from normal rat serum. These results suggest either that natural antibody to the trypanosomes is present in the serum of uninfected rats or that some rat immunoglobulins bind to structures on the trypanosome surface in ways that do not depend on usual antigen-antibody interactions. Finally, flow immunofluorescence was also used to detect complement component C3 on the surface of both intact and trypsinized bloodstream forms harvested from intact or immunosuppressed rats. The amount of sC3 per cell did not increase until late in the infection and consequently did not correlate with the increase of sIgG. Therefore, T. lewisi avoids destruction by the immune system although immune effector molecules, IgG, IgM, and C3, are on its surface.     

Prevalence of Toxoplasma gondii in rats (Rattus norvegicus) in Grenada, West Indies

Cats are important in the natural epidemiology of Toxoplasma gondii, because they are the only hosts that can excrete environmentally resistant oocysts. Cats are infected with T. gondii via predation on infected birds and rodents. During 2005, 238 rats (Rattus norvegicus) were trapped in Grenada, West Indies, and their sera along with tissue samples from their hearts and brains were examined for T. gondii infection. Antibodies to T. gondii were assayed by the modified agglutination test (MAT, titer 1:40 or higher); only 2 (0.8%) of 238 rats were found to be infected. Brains and hearts of all rats were bioassayed in mice. Toxoplasma gondii was isolated from the brain and the heart of only 1 rat, which had a MAT titer of 1:320. All of 5 mice inoculated with the heart tissue, and the 5 mice inoculated with the brain tissue of the infected rat remained asymptomatic, even though tissue cysts were found in their brains. Genetically, the isolates of T. gondii from the heart and the brain were identical and had genotype III by using the SAG1, SAG2, SAG3, BTUB, and GRA6 gene markers. These data indicate that rats are not important in the natural history of T. gondii in Grenada.     

A method for the assay of ablastin in the serum of rats infected with Trypanosoma lewisi.

This paper describes a simple quantitative assay for albastin, a factor present in the serum from rats infected with Trypanosoma lewisi, which prevents the division of the parasite. The assay measures in vitro the inhibition of the incorporation of 3H-TdR into the DNA of T. lewisi in the presence of serum from infected animals. Utilising this method, one can measure the titre of albastin in a particular serum sample and the time and duration of its appearance in the circulation of infected rats.     

Suppressor and protector factors derived from Trypanosoma lewisi.

Trypanosoma lewisi is a specific protozoan blood parasite of rats. Normal rats infected 2 h after treatment with plasma from day 8 irradiated (8.5 Gy) infected rats had significantly higher parasitaemia; in contrast, animals infected 7 days post-plasma treatment were significantly protected. Trypanolytic and ablastic antibodies could be demonstrated in the serum of normal rats treated with the plasma; the trypanolytic antibodies were stage-specific. Suppression of normal rat splenocyte responses to Con A and lipopolysaccharide (LPS) stimulation were also observed in the presence of different protein concentrations of whole lysate from epimastigote forms. The suppression by mitogen Con A was ablated by the addition of exogenous IL 2, or by washing cells incubated with the lysate prior to mitogen stimulation. These results indicate that immunoregulatory factors are present in the plasma of rats infected with T. lewisi, and the effect of these factors can be demonstrated in vitro with whole parasite lysate. The restoration of normal splenocyte responses to Con A by addition of exogenous IL 2 or by washing cells suggests that the suppressor factor(s) act(s) on the T cells by inhibiting their proliferation and IL 2 production, and the continued presence of these products is essential in the maintenance of suppression.     

Blood and intestinal parasites of squirrels (Rodentia: Sciuridae) in Amazonian Brazil

We report the result of an examination for blood and intestinal protozoa in 12 specimens of the red squirrel Sciurus spadiceus (Rodentia: Sciuridae) from Birroque, municipality of Placido de Castro, state of Acre, Brazil. No parasites were detected in thin, Giemsa-stained blood films of the animals, but culture of the blood of three in Difco B45 medium blood-agar slants gave rise to isolates of epimastigotes. Inoculation of one isolate into laboratory mice resulted in the appearance of Trypanosoma cruzi-like trypomastigotes in their peripheral blood, and the other two isolates gave rise to transient infections with a T. lewisi-like parasite in inoculated mice and hamsters. The failure of the latter parasite to develop in the triatomine bug Rhodnius robustus suggests that it is probably not T. rangeli. This appears to be the first record of a T. lewisi-like trypanosome in neotropical squirrels. Oocysts of an Eimeria sp., were detected in the faeces of 10 animals (83.3%). The parasite develops in the epithelial cells of the intestine, where it may cause severe damage and sometimes results in death of the animal. No oocysts were detected in bile.