Pathology of experimental Trypanosoma evansi infection in rabbits.

Histopathological examination of tissue sections from the organs of rabbits experimentally infected with Trypanosoma evansi revealed evidence of a vigorous immunological response. Changes in the spleen, lymph nodes, vulva, eyelids and ears indicated a protective immune response, but changes in the kidneys, lungs and heart were destructive in nature and capable of causing sudden death of the host. Hepatic damage capable of interfering with the host's immune response was also observed. The presence of many parasites in the vulval tissue calls for further investigation into the possibility of sexual transmission of T. evansi.     

Human Trypanosoma evansi infection linked to a lack of apolipoprotein L-I

Humans have innate immunity against Trypanosoma brucei brucei that is known to involve apolipoprotein L-I (APOL1). Recently, a case of T. evansi infection in a human was identified in India. We investigated whether the APOL1 pathway was involved in this occurrence. The serum of the infected patient was found to have no trypanolytic activity, and the finding was linked to the lack of APOL1, which was due to frameshift mutations in both APOL1 alleles. Trypanolytic activity was restored by the addition of recombinant APOL1. The lack of APOL1 explained the patient's infection with T. evansi.     

Experimental Trypanosoma evansi infection in the goat. II. Pathology

Infection of male goats aged 8-10 months with 5000 or 50 000 organisms of a Mindanao strain of Trypanosoma evansi was observed over a period of 90 days. The infection induced clinical disease which was lethal, especially at the higher dose rate. Lesions were more acute in goats that received the higher dose. Gross and microscopical changes were not pathognomonic, except in the presence of demonstrable trypanosomes. At necropsy, a combination of lymphadenopathy, splenomegaly, hepatomegaly, testicular enlargement, anaemic signs and consolidation of the anterior lobes of the lungs was suggestive of surra. Testicular changes, especially aspermia, indicated probable infertility. The cytopathology of the lungs, liver, intestine, kidneys, testes, bone marrow, brain and other organs was immunological in nature, characterized by mononuclear infiltration of interstitial tissues, with minor cellular damage and the presence of trypanosomes. B- and T- cell responses were observed in the lymphatic system, but the findings indicated immunosuppression in the lymph nodes, spleen and bone marrow during the third month after infection. Exudative inflammatory changes were mild. It is suggested that the cytopathology of most haemophilic trypanosomal infections is predominantly an immunological process.     

Experimental Trypanosoma evansi infection in the goat. I. Clinical signs and clinical pathology

A strain of Trypanosoma evansi isolated from an equine case of surra in Mindanao, Philippines was used to infect intravenously two groups (A and B) of five male goats aged 8-10 months. Animals of groups A and B received 5000 and 50 000 trypanosomes, respectively, and five further animals (group C) served as uninfected controls. Four of the 10 infected goats died 8-78 days after inoculation. Group C goats gained weight (mean 22.8 g/day) while infected goats in groups A and B lost weight (means of 21.4 and 45.0 g/day, respectively). Parasitaemia fluctuated regularly between peaks and troughs, with repeated periods of about 6 days during which no trypanosomes were detected in the blood. Clinical signs and clinico-pathological changes in infected goats were not pathognomonic in the absence of parasites in the blood, and leucocytosis was not a reliable indicator of infection. It was concluded that in endemic areas fluctuating fever, progressive emaciation, anaemia, coughing, testicular enlargement and diarrhoea are suggestive of surra; confirmation, however, may necessitate examination of blood every few days for trypanosomes, and possibly other diagnostic tests.     

Ticks (Acari: Ixodidae) associated with wild animals in the Pantanal region of Brazil

This paper describes the identification of ticks from wild animals of the Pantanal region in Brazil as part of a comprehensive study about established and emerging tick-host relationships and related pathological aspects. Eighty-one animals were captured (representing 13 species, six orders), and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), Amblyomma parvum Arag?o, Amblyomma pseudoconcolor Arag?o, Amblyomma scalpturatum Neumann, Amblyomma nodosum Neumann, Amblyomma ovale Koch, and Amblyomma tigrinum Koch. Dragging from grasslands yielded negative results compared with the high concentration of ticks that were collected from leaves in the forests.     

Trypanosoma evansi infection on levels of copper, iron, and zinc in the plasma of rats

This study aimed to assess plasma concentrations of copper, iron, and zinc during the course of acute Trypanosoma evansi experimental infection in rats. Fifty male Wistar rats were randomly distributed into seven groups: three trypanosome-infected groups (T2, T4, and T6; n?=?10 animals per group) and four uninfected controls (C0, C2, C4, and C6; n?=?5 animals per group). Animals from trypanosome-infected groups were intraperitoneally injected with 10⁶ trypanosomes/animal. Blood samples were collected by cardiac puncture before infection (day 0; group C0) or on the second (C2 and T2), fourth (C4 and T4), and sixth (C6 and T6) day postinfection. Parasitemia and hematological evaluation were performed to assess the progression of the disease in animals. The difference between groups (control and infected) was evaluated on the same day postinfection. Plasma copper concentration increased in T4 and T6 groups (P?<?0.001) compared with the control group. Plasma iron concentration decreased only in group T2 (P?<?0.001). There was no significant difference in the plasma zinc concentration between groups. This study therefore demonstrates that high plasma copper concentration and depression in iron concentration is part of the acute phase response in rats infected with T. evansi.     

Multinuclear forms in a dyskinetoplastic strain of Trypanosoma evansi in mice

The production of short stumpy and multinuclear trypanosomes in a Chinese strain of dyskinetoplastic Trypanosoma evansi maintained in rabbits and mice is described. Production of multinuclear trypanosomes was increased following passage through a reptile (gecko), in which the trypanosomes did not multiply, and transfer back to mice. The multinuclear trypanosomes showed more nuclei than flagella indicating that disruption of the normal cell cycle had taken place and not simply inhibition of cleavage. A Chinese kinetoplastic T. evansi treated similarly rarely produced stumpy or multinuclear forms.     

Changes in peripheral blood lymphocyte subpopulations and parasite-specific antibody responses in Trypanosoma evansi infection of sheep

This paper reports on changes in the lymphocyte composition of the peripheral blood in sheep infected with Trypanosoma evansi. In addition, parasite-specific IgG₁ and IgM antibody responses were monitored using a double-sandwich enzyme-linked immunosorbent assay (ELISA) technique. Eight sheep were infected with 2 × 10⁶ T. evansi TREU 2143. The infection was characterised by chronicity and ended in self-cure in two of the sheep. These two sheep were designated group A, whereas the other six sheep, which remained parasitaemic until treated, were designated group B. Analysis of the peripheral blood lymphocytes (PBLs) by indirect immunofluorescence staining and flow cytometry revealed significant alterations in the numbers of T- and B-cell subsets detected in all infected sheep. In group A, whereas the numbers of CD8⁺ cells decreased, CD4⁺ cells showed marginal decreases, remaining at or above pre-infection figures and resulting in increase in the CD4:CD8 ratio. In group B, CD8⁺ cells showed few marginal decreases, being at or above pre-infection figures most of the time, whereas CD4⁺ cells decreased significantly from day 26 post infection (p.i.) such that the CD4:CD8 ratio decreased. Infection also resulted in significant increases (P < 0.001) as of day 26 p.i. in circulating B-cells in group B as shown by the numbers of sIg⁺, CD45R⁺, CD1⁺ and major histocompatibility complex (MHC) II⁺ cells. The increases, however, were moderate and biphasic in group A. T. evansi-specific IgM and IgG₁ antibody isotypes were detected in all infected sheep, but their levels were significantly higher in group A than in group B (IgM P <0.05; IgG₁ P <0.01). In addition, although an initially higher level of IgM response was subsequently replaced by a higher level of IgG₁ response in group A, this was never the case in group B until after drug treatment. Received: 16 May 1998 / Accepted: 17 June 1998     

Thrombocytopenia and increased clotting time in rats acutely infected by Trypanosoma evansi

The aims of this study were to evaluate clotting disturbances in the acute infection by Trypanosoma evansi in rats and to investigate two possible causes. To address this issue, 21 2-month-old male rats were separated into three groups with seven animals each. The control group (group I) was composed of non-infected animals and group II was composed of 14 T. evansi-infected animals. This group was subdivided into two homogeneous groups. Animals from group II-a and from group II-b were euthanized at days 3 and 5 post-inoculation (PI), respectively. Hematological parameters were evaluated for monitoring of the disease. Infected animals showed anemia and leukocytosis 3 days PI and a significant decrease was observed in platelet count at days 3 and 5 PI. The prothrombin time (PT) and activated partial thromboplastin time (aPTT) were longer in the infected groups. The averages of the megakaryocyte count significantly increased (P < 0.05) in group II-b (5 days PI). Splenomegaly was observed in all T. evansi-infected rats at necropsy. Based upon the results, it is concluded that the acute infection by T. evansi in rats causes thrombocytopenia and longer prothrombin and activated partial thromboplastin times. In response to the thrombocytopenia, an increased number of bone marrow megakaryocytes were observed in the infected rats. Thus, the decrease in circulating platelets may be a consequence of splenic sequestration.     

The effect of samorin (isometamedium chloride) on Trypanosoma evansi infection in mice.

Samorin (isometamedium chloride) was effective against T. evansi in mice given in single i.p. doses of 1 to 10 mg/kg. The administration of 40 mg/kg of samorin or above caused rapid death of mice and there were severe haemorrhages, degeneration and congestion in the liver, heart and kidney. The lesions in the liver and kidney were accompanied with reduced activities of ATP-ase, 5-nucleotidase, succinic tetrazolium reductase and glucose-6-phosphatase.     

Glutathione and iron at the crossroad of redox metabolism in rats infected by Trypanosoma evansi

The aim of this study was to evaluate the changes in hematological and biochemical parameters of blood during acute Trypanosoma evansi infection in Wistar rats. The end points studied were hematologic parameters, red blood cell fragility, iron content, and glutathione and lipid peroxidation levels. Forty-eight animals were infected with trypomastigotes and distributed into five groups according to the level of parasitemia. Twelve non-inoculated animals were used as control. Parasitemia increased progressively, reaching highest scores at 15 days post-inoculation. At this point, several deleterious effects were observed such as an increase in iron content, in osmotic fragility, and in lipid peroxidation index, while glutathione decreased drastically. These changes were highly correlated to parasitemia (p?<?0.0001) and among each other (p?≤?0.001). Hematological indices (Hb, packed cell volume (PCV), red blood cells (RBC), and mean corpuscular hemoglobin concentration) were also correlated to parasitemia (p?≤?0.0003) but failed to correlate to the other variables. Along with increase in iron, RBC fragility produced a decrease in RBC, PCV, and Hb, but not in mean corpuscular volume. Decrease in glutathione was negatively correlated to the end products of lipid peroxidation, clearly indicating the establishment of a pro-oxidant condition. The results show that the infection causes hematological impairments, increases iron and osmotic fragility, along with marked oxidative stress in red blood cells of rats inoculated with T. evansi.     

Failure of protection induced by a Brazilian vaccine against Brazilian wild rabies viruses

Summary.  This report shows that the SMB vaccine currently used in Brazil for human immunisation provides different degrees of protection in mice, depending on the rabies virus strain used as challenge. Using the NIH and Habel potency tests to evaluate the protective activity of rabies vaccine, we observed that vaccinated mice showed a higher resistance to a challenge with a fixed rabies virus (CVS – Challenge Virus Strain). The vaccine potency using the Habel or NIH tests was respectively > 6.4 (log 10) and 1.0 (Relative Potency-RP) when the fixed rabies virus was used for challenge, and from 2.9 to 4.3 (log 10) or 0.13 to 0.8 (RP) when different wild rabies viruses were used for challenge. The presence of virus neutralising antibodies (VNA) could not explain the differences of susceptibility after vaccination, since sera of vaccinated animals had similar VNA levels against both fixed and wild strains before virus challenge (respectively, 5.6 ± 0.24 and 5.0 ± 0.25 IU/ml of VNA against the fixed rabies virus and the 566-M strain of wild rabies virus in sera of mice vaccinated with 0.2 units of vaccine). Only cell-mediated immunity parameters correlated with the protection induced by vaccination. The IFN_γ titers found in sera and brain tissues of animals challenged with CVS strain were higher (from 36.7 ±  5.7 to 293.3  ±  46.2 IU/ml) than those found in mice challenged with 566-M virus strain (from 16.7 ± 5.8 to 36.7 ± 5.8). The proliferation index of spleen cells obtained with CVS stimulation reached a maximal value of 15.1 ± 0.7 while spleen cells from vaccinated mice stimulated with 566-M virus failed to proliferate. The implications of these data in human protection by vaccination are discussed. Received October 13, 1997 Accepted April 3, 1998     

Genetic characterization and phylogenetic analysis of Trypanosoma evansi in Iranian dromedary camels

Whole blood samples were collected from 117 male clinically healthy Camelus dromedarius aged between 6 months to 18 years from several farms in Yazd Province of Iran. Trypanosoma evansi-affected camels were detected by Giemsa-stained blood smears, and the positive blood samples (4 out of 117) were submitted to PCR examination and phylogenetic analysis. Basic Local Alignment Search Tool data of the obtained complete internal transcribed spacer (ITS) sequences revealed that they corresponded to those of T. evansi, Thailand cattle isolate (AY912276) with the homology of 99 %. Both phylogenetic trees generated by ITS1 and complete ITS were unable to clearly show inter- and intraspecific genetic diversity of Trypanosoma spp. isolates. The phylogenetic tree inferred from the ITS2 nucleotide sequences (569 bp) clearly showed the genetic diversity of the parasites. Phylogenetic and molecular analyses of this region showed that two distinct genotypes of T. evansi in Iranian dromedary camels are present. In contrast to the ITS1 and ITS2 regions, multiple alignment of the nucleotide sequence of the 5.8S rRNA showed a high degree of sequence conservation during evolution in various Trypanosoma spp.     

Futile import of tRNAs and proteins into the mitochondrion of Trypanosoma brucei evansi

Trypanosoma brucei brucei has two distinct developmental stages, the procyclic stage in the insect and the bloodstream stage in the mammalian host. The significance of each developmental stage is punctuated by specific changes in metabolism. In the insect, T. b. brucei is strictly dependent on mitochondrial function and thus respiration to generate the bulk of its ATP, whereas in the mammalian host it relies heavily on glycolysis. These observations have raised questions about the importance of mitochondrial function in the bloodstream stage. Peculiarly, akinetoplastic strains of Trypanosoma brucei evansi that lack mitochondrial DNA do exist in the wild and are developmentally locked in the glycolysis-dependent bloodstream stage. Using RNAi we show that two mitochondrion-imported proteins, mitochondrial RNA polymerase and guide RNA associated protein 1, are still imported into the nucleic acids-lacking organelle of T. b. evansi, making the need for these proteins futile. We also show that, like in the T. b. brucei procyclic stage, the mitochondria of both bloodstream stage of T. b. brucei and T. b. evansi import various tRNAs, including those that undergo thiolation. However, we were unable to detect mitochondrial thiolation in the akinetoplastic organelle. Taken together, these data suggest a lack of connection between nuclear and mitochondrial communication in strains of T. b. evansi that lost mitochondrial genome and that do not required an insect vector for survival.     

High incidence of rhinovirus infection in children with community-acquired pneumonia from a city in the Brazilian pre-Amazon region

Community-acquired pneumonia (CAP) is the leading cause of child death worldwide. Viruses are the most common pathogens associated with CAP in children, but their incidence varies greatly. This study investigated the presence of respiratory syncytial virus (RSV), adenovirus, human rhinovirus (HRV), human metapneumovirus (HMPV), human coronavirus (HCoV-OC43 and HCoV-NL63), and influenza A virus (FluA) in children with CAP and the contributing risk factors. Here, children with acute respiratory infections were screened by pediatrics; and a total of 150 radiographically-confirmed CAP patients (aged 3 months to 10 years) from two clinical centers in Sao Luis, Brazil were recruited. Patient's clinical and epidemiological data were recorded. Nasopharyngeal swab and tracheal aspirate samples were collected to extract viral nucleic acid. RSV, adenovirus, rhinovirus, FluA, HMPV, HCoV-OC43, and HCoV-NL63 were detected by real-time polymerase chain reaction. The severe CAP was associated with ages between 3 and 12 months. Viruses were detected in 43% of CAP patients. Rhinovirus infections were the most frequently identified (68%). RSV, adenovirus, FluA, and coinfections were identified in 14%, 14%, 5%, and 15% of children with viral infection, respectively. Rhinovirus was associated with nonsevere CAP (P = .014); RSV, FluA, and coinfections were associated with severe CAP (P < .05). New strategies for prevention and treatment of viral respiratory infections, mainly rhinovirus and RSV infections, are necessary.     

Ultrastructural alterations in the adrenal gland cortex of mice experimentally infected with a Venezuelan isolate of Trypanosoma evansi

The ultrastructural study of adrenal gland from mice experimentally infected with Trypanosoma evansi, in addition to intravascular and intracellular trypanosomes, showed different degrees of cortical cell alterations and capillary wall modifications. Beside its biological scope, these results suggest a role for the adrenal cortex to partake in Surra's etiopathogenesis and describe for the very first time a T. evansi intracellular stage.     

The role played by sympatric collared peccary (Tayassu tajacu), white-lipped peccary (Tayassu pecari), and feral pig (Sus scrofa) as maintenance hosts for Trypanosoma evansi and Trypanosoma cruzi in a sylvatic area of Brazil

The Brazilian Pantanal has been considered one of the richest and most diverse wetland ecosystems in the world. It is occupied by cattle ranching, and a variety of wildlife species share the same habitats with domestic livestock. We investigated infections of Trypanosoma evansi and Trypanosoma cruzi in the sympatric suiformes-collared peccary (Tayassu tajacu), white-lipped peccary (Tayassu pecari), and feral pig (Sus scrofa) by parasitological, serological, and molecular tests. Additionally, we evaluated the health status of both positive and negative suiformes by hematological and biochemical parameters. The results show that peccaries and feral pigs play an important role on the maintenance of both T. evansi and T. cruzi in the Brazilian Pantanal. Health impairment was observed only in the white-lipped peccary infected with T. evansi. Despite presenting low T. evansi parasitemia, all infected white-lipped peccaries displayed low hematocrit values and marked leucopenia. The hematological values showed that the T. evansi infection is more severe in young white-lipped peccaries. The presented data show that feral pigs and peccaries are immersed in the transmission net of both trypanosome species, T. cruzi and T. evansi, in the Pantanal region.