Pathogenesis of Trypanosoma brucei infection in deer mice (Peromyscus maniculatus): light and electron microscopic studies on erythrocyte pathologic changes and phagocytosis

Light microscopic and scanning and transmission electron microscopic studies demonstrated that Trypanosoma brucei EATRO 110 produced several alterations in RBC structure including microspherocytes, schistocytosis, vacuolation, doughnut-cell formation, and keratocytosis. Mature RBC and reticulocytes were constantly observed to adhere firmly to trypanosomes in heart blood and in blood vessels of the testes, heart, liver, and kidney, as well as in the sinuses and pulp cords of the spleen. Adhesion of RBC to trypanosomes was also observed by light microscopy in thin blood films. Except for a few platelets that adhered to trypanosomes, other blood cells were not involved. Minute pores were sometimes observed on the RBC membrane at the point of adhesion to the trypanosome, but effects were not seen on the parasite. Erythrophagocytosis was marked in the spleen and to a lesser extent in the liver; mature RBC, as well as reticulocytes, were engulfed. Erythrophagocytosis was presumed to arise from the mechanical injury to RBC, the damage caused by the adhesion phenomenon and the hyperactivity of the enormously enlarged spleen.     

Immunosuppression in experimental trypanosomiasis: effects of Trypanosoma equiperdum on the pathogenesis of influenza virus infection in deer mice (Peromyscus maniculatus)

The effects of Trypanosoma equiperdum infections on the immunological and pathological responses of deer mice (Peromyscus maniculatus) to influenza virus exposure were investigated. Mice carrying a 5 week trypanosome infection along with an age- and sex-matched trypanosome-free control group were simultaneously exposed to influenza Ao (WSN) virus. T. equiperdum infection significantly (P less than 0.01) converted a sub-lethal virus attack into a fatal pneumonic process in a small proportion of animals. In addition, the trypanosome caused a reduction (p less than 0.1) in virus replication on PID 1 and 2, accompanied later by a tendency towards virus persistence in the lungs of affected mice. This tendency was manifested by a log reduction in virus titres between PID 2 and 4 and PID 4 and 6 in the lungs of trypanosome-infected mice, compared to 2 log drops over the same periods in the lungs of control mice. T. equiperdum infection also significantly (p less than 0.001) depressed serum and pulmonary neutralizing antibody titres to influenza virus.     

Pathogenesis of experimental vesicular stomatitis virus (New Jersey serotype) infection in the deer mouse (Peromyscus maniculatus)

The pathogenesis of vesicular stomatitis virus (VSV) infection has not been investigated previously in native New World rodents that may have a role in the epidemiology of the disease. In the present study, 45 juvenile and 80 adult deer mice (Peromyscus maniculatus) were inoculated intranasally with VSV New Jersey serotype (VSV-NJ) and examined sequentially over a 7-day period. Virus was detected by means of immunohistochemistry and in situ hybridization in all tissues containing histologic lesions. Viral antigen and mRNA were observed initially in olfactory epithelium neurons, followed by olfactory bulbs and more caudal olfactory pathways in the brain. Virus also was detected throughout the ventricular system in the brain and central canal of the spinal cord. These results support both viral retrograde transneuronal transport and viral spread within the ventricular system. Other tissues containing viral antigen included airway epithelium and macrophages in the lungs, cardiac myocytes, and macrophages in cervical lymph nodes. In a second experiment, 15 adult, 20 juvenile, and 16 nestling deer mice were inoculated intradermally with VSV-NJ. Adults were refractory to infection by this route; however, nestlings and juveniles developed disseminated central nervous system infections. Viral antigen also was detected in cardiac myocytes and lymph node macrophages in these animals. Viremia was detected by virus isolation in 35/72 (49%) intranasally inoculated juvenile and adult mice and in 17/36 (47%) intradermally inoculated nestlings and juveniles from day 1 to day 3 postinoculation. The documentation of viremia in these animals suggests that they may have a role in the epidemiology of vector-borne vesicular stomatitis.     

A soluble immunosuppressor substance in spleen in deer mice infected with Trypanosoma brucei.

A soluble substance that blocks B-cell response was extracted from spleen of deer mice (Peromyscus maniculatus) chronically infected with Trypanosoma brucei. Immunosuppressor activity of this substance was demonstrated by plaque-forming cell assays of spleen cells from Swiss/Webster mice inoculated with sheep red blood cells and simultaneously given the suppressor substance, and of spleen cell cultures treated with sheep red blood cells and suppressor substance. Studies by light and electron microscopy of spleen of immunosuppressed Swiss/Webster mice showed that the suppressor substance blocks germinal center formation and prevents plasma cell differentiation in the red pulp cords.     

DL-alpha-difluoromethylornithine (DFMO)-Berenil combination: therapeutic and prophylactic activity against Trypanosoma brucei brucei infection in mice.

The therapeutic and prophylactic activity of difluoromethylornithine (DFMO) (2% in drinking water for 4 days) and Berenil (7 mg/kg live weight intraperitoneally) combination was investigated in mice infected with Trypanosoma brucei brucei. Using a previously described mouse model of the African trypanosomosis of the central nervous system, it was demonstrated that the combination was curative and acted synergistically. However, if used prophylactically it had no advantage over Berenil alone.     

Effect of anti-ganglioside antibody in experimental Trypanosoma brucei infection in mice

The effect of antibody against ganglioside antigen on Trypanosoma brucei parasites was examined in vitro and in vivo using anti-ganglioside GM1 (AGM-1) monoclonal antibody. The antibody showed complement-dependent cytotoxicity against T. brucei with mouse complement. Furthermore, mice given AGM-1 were challenged intraperitoneally with T. brucei. Although all non-treated control mice died within six days after infection, all of AGM-1-injected mice had survived by six days post-infection. These data suggest that antibody against ganglioside antigen on T. brucei has potential in protection against T. brucei infection.     

Effects of infection with Trypanosoma brucei brucei on different trimesters of pregnancy in ewes.

The effects of Trypanosoma brucei brucei infection during the first, second or third trimesters of pregnancy in 13 ewes were studied. All infected ewes were anaemic with the anaemia being most severe, moderate and least in ewes infected in the second, third and first trimesters, respectively. Weight loss occurred in all infected ewes but was most severe in ewes infected in the third trimester. Three of the four ewes infected in the first trimester died without aborting while one aborted and later died. Of the four ewes infected in the second trimester, three died without aborting while one lambed and later died. In the third trimester ewes, one aborted, two lambed and all three later died while one died without aborting. None of the lambs was viable. The control ewe lambed normally. The infection resulted in 16.7% abortion, 100% death and 33.3% neonatal deaths. This study demonstrates that T. brucei brucei has a devastating effect on pregnancy irrespective of the trimester of infection.     

Genital lesions in experimental chronic Trypanosoma brucei infection in rams.

Rams inoculated intravenously with Trypanosoma brucei developed scrotal oedema and a nonsuppurative granulomatous periorchitis resulting in testicular degeneration, atrophy, calcification and sclerosis. The tunica vaginalis was the seat of an intense granulomatous inflammation and focal necrosis, which extended to the epididymis and spermatic cord. Lesions in the seminal vesicles were suggestive of diminished testosterone production even though Leydig cells were discernible in the sclerotic testicular intertubular tissue. In areas where there was inflammation or focal necrosis, there was also extravascular localisation of trypanosomes. It is suggested that genital lesions in human sleeping sickness may have a similar pathogenetic mechanism involving tissue localisation of the trypanosomes and associated inflammatory and degenerative changes.     

Flurbiprofen and immunosuppression of Trypanosoma brucei infection in the goat

Goats infected with Trypanosoma brucei and treated with the non-steroidal anti-inflammatory agent flurbiprofen, showed a marked increase in parasitaemia, followed in one of the four goats by death. The in vitro response to mitogens of peripheral blood lymphocytes and separated T- and B-lymphocytes from healthy goats treated with flurbiprofen was normal when compared with non-treated animals. T. brucei-infected goats, not treated with flurbiprofen, showed a marked immunosuppression which was mainly localized in the B-enriched lymphocyte fraction. A combination of T. brucei infection and treatment with flurbiprofen led to even more suppression, because the T-lymphocyte function was also suppressed. It is concluded that flurbiprofen first causes a rise in the parasitaemia and that this high parasitaemia is responsible for the observed immunosuppression.     

Pathogenicity of Trypanosoma brucei brucei in experimentally infected pigs.

An experimental infection of 4-to 5-month old pigs with a stock of Trypanosoma brucei brucei resulted in a high parasitaemia, anorexia, pyrexia and a decline in the packed cell volume by one third. Nervous sign of circling and wobbling of the hind legs occurred in one of the pigs which at necropsy revealed a very severe meningo-encephalitis and the presence of trypanosomes in the brain. These results confirm that T. b. brucei might cause a severe disease in pigs.     

Haematology of experimental Trypanosoma brucei gambiense infection. II. Erythrocyte and leucocyte changes.

Chronic Trypanosoma b. gambiense infection of rabbits induced mild anaemia which was initially macrocytic normochromic, but became later microcytic hypochromic. Moderate anisocytosis and poikilocytosis were evident from 14 days post infection (p.i.). Nucleated red cells which were observed prior to the infection (normal feature of rabbits) declined in number as the infection progressed. Leucocytosis with neutrophilia, eosinophilia, monocytosis and terminal lymphopaenia were also observed. The main changes in the morphology of leucocytes were the presence of atypical lymphocytes as well as increased levels of band neutrophils in the peripheral circulation. It is concluded that the main erythrocytic and leucocytic changes in the T.b. gambiense infection were mild anaemia which was terminally microcytic hypochromic and transient leucocytosis due to neutrophilia and monocytosis.     

Some plasma biochemical changes in experimental Trypanosoma brucei infection of Sokoto Red goats.

Plasma biochemical changes were studied for 8 consecutive weeks in Sokoto Red goats experimentally infected by intravenous route injection of 1.6 x 10(7) Trypanosoma brucei. The strain 8/18 was highly infective. The mean packed cell volume significantly decreased from 1 to 8 weeks post-infection (PI) at P < 0.05. During this period, the mean plasma total bilirubin concentrations significantly increased (P < 0.05). The mean plasma direct and indirect bilirubin concentrations significantly increased from 2 to 8 weeks PI (P < 0.05). The mean plasma albumin concentrations did not vary significantly (P > 0.05), but the mean total plasma proteins and mean plasma globulin concentrations significantly increased between 5 and 8 weeks post infection (P < 0.05). There were no significant changes in the mean plasma bicarbonate, creatinine and cholesterol concentration (P > 0.05).     

Comparative efficacy assessment of pentamidine isethionate and diminazene aceturate in the chemotherapy of Trypanosoma brucei brucei infection in dogs

The chemotherapeutic efficacy of diminazene aceturate (Berenil)--a standard veterinary trypanocide and pentamidine isethionate (PMI)--a human trypanocide was compared in dogs experimentally infected with Trypanosoma brucei brucei. Also, the activities of the drugs on some serum liver enzymes were evaluated before and after treatment to ascertain the relative safety of the drugs. Fifteen local dogs (mongrels) were used for the study. Three of the dogs were uninfected controls, and twelve were infected with a stock of T. brucei brucei. Three of the infected dogs were untreated controls, three were given diminazene aceturate (DA) at 7 mg/kg body weight intramuscularly (i/m), another three received pentamidine isethionate (PMI) at 4 mg/kg i/m on days 14, 17, 19, 27, 29, and 31 post infection (PI) and the remaining three dogs were also given same dose of PMI on days 14, 16, 18, 20, 22, 24 and 26 PI. Both trypanocides effectively cleared the parasites from the blood of the infected treated dogs. However, the infection subsequently relapsed at day 42 PI in one of the dogs in the DA treated group which later died at day 70 PI. Relapse infection was not recorded with the PMI treated groups although two dogs died in the PMI treated group II (treatment at days 14, 17, 19, 27, 29, and 31 PI) without showing relapsed parasitaemia. The packed cell volume (PCV), red blood cell (RBC) count, and haemoglobin (Hb) level which decreased significantly following infection, were reversed by the trypanocidal treatment. The reversal in the red cell values was faster in the PMI treated groups than in the DA treated group. The serum alkaline phosphate (SAP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels increased following infection and drug administration. The increase in the enzyme levels was greater in the DA treated groups than PMI treated groups. It was thus concluded that PMI given at 4 mg/kg i/m at days 14, 16, 18, 20, 22, 24, and 26 PI constituted a safe and efficient trypanocide and exhibited a superior trypanocidal action than DA in T. brucei brucei infected dogs.