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.     

Diminazene aceturate residues in the tissues of healthy, Trypanosoma congolense and Trypanosoma brucei brucei infected dogs

The tissue distribution and residue profile of diminazene aceturate was investigated in healthy dogs and in dogs infected with Trypanosoma congolense and Trypanosoma brucei brucei. The drug was administered at 3.5 mg/kg i.m. and tissue samples were taken post mortem from the animals at 48, 72, 120, 168 and 240 h after injection. The drug was distributed to various organs and tissues of the body with the highest concentrations occurring in liver and kidney. Higher drug levels were obtained in the tissues of healthy dogs compared with trypanosome infected animals except in the brain. The levels of residues in the healthy animals were significantly different (P less than 0.05) from those of the infected dogs. The drug residues were still detectable in the tissues of the animals 10 days after drug administration.     

Parasitaemia and clinical manifestations in Trypanosoma brucei infected dogs.

Four dogs were infected with Trypanosoma brucei (Mkar strain) while another four were used as uninfected controls. Two of the dogs showed acute disease and died in the first wave of parasitaemia on days 7 and 8 post infection (PI) while the other two died from the sub-acute disease on days 24 and 28 PI corresponding to the second wave of parasitaemia. In the first wave of parasitaemia there was a sharp decrease in the packed cell volume, red blood cell, haemoglobin, total leucocytes, eosinophil, neutrophil and lymphocyte values, but during the period of low parasitaemia there was a slight recovery of the values of total leucocytes and lymphocytes although these and the other values showed a continuous decrease during the second wave of parasitaemia. In contrast, there was a consistent monocytosis in both acute and sub-acute diseases. The general picture was that of loss of condition, anaemia, leucopenia, monocytosis, ocular impairment, elevated temperature, pulse and respiratory rates, the difference between the acute and sub-acute diseases being in the degree of intensity. The degree of anaemia noted and the circulatory disturbances associated with the infection could have caused the death of all the infected dogs.     

The pathogenesis of anaemia in goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei: use of the myeloid:erythroid ratio

The present study examined the development of anaemia in Small East African goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei. Experimental goats received a primary trypanosome challenge on day 0, treated with diminazene aceturate on day 49 and received a secondary trypanosome challenge on day 77 of the 136-day experiment. Both primary and secondary challenges were characterised by reduced peripheral erythrocyte counts, fall in packed cell volume (PCV), hypohaemoglobinaemia and reductions in the myeloid:erythroid ratios (M:E) compared with the uninfected goats. The progressive reduction in the M:E ratios denoted increased erythrogenesis in response to increased destruction of erythrocytes in blood by infecting trypanosomes or their products. The more rapid fall in M:E ratio in T. congolense infections shows that this parasite causes more severe clinical pathological effects in goats than T. brucei.     

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.     

The blood volumes and erythrokinetics of Ndama and Zebu cattle experimentally infected with Trypanosoma brucei.

The responses of susceptible Ndama and Zebu cattle to experimental infection with Trypanosoma brucei were compared using haematological, parasitological and radioisotopic methods. Animals of both breeds became anaemic, but this was more severe in the Zebu cattle, one of which died. Although the prepatent period was the same in animals of both breeds, the levels of the first and subsequent peaks of parasitaemia were higher in the Zebu. The anaemia was due to an accelerated rate of red cell break-down which was more marked in the Zebu cattle. Haemodilution was not a feature. There was no evidence of dyshaemopoiesis but iron reutilisation from degraded erythrocytes was impaired. The greater resistance of the Ndama to T brucei infection could not be attributed to the capacity of this breed to mount a more effective erythropoietic response than the Zebu.     

The relationship between dietary energy levels and the severity of Trypanosoma brucei infection in growing pigs

Growing pigs were placed on high, medium and low planes of dietary energy and were infected with a virulent strain of Trypanosoma brucei. During an 8-week period post-infection (p.i.), the respective liveweight gains by infected pigs on high, medium and low energy levels were 52.1, 21.2 and 38.5%, respectively, of the corresponding gains by non-infected control pigs. There was a fall in red blood cell values p.i. which worsened with decreasing energy levels. Leucocytosis was observed in all infected pig groups and was mainly due to lymphocytosis. By 6 weeks p.i., the lymphocyte count had returned to near normal values in pigs on high and medium energy levels, but was persistently high in those on a low energy level. Neutropaenia was observed in all infected pig groups and persisted until 8 weeks p.i. The results indicated that nutrition modulates the host response to infection with trypanosomes.     

Effects of postexsanguination vascular infusion of cattle with a solution of saccharides, sodium chloride, phosphates, and vitamins C, E, or C+E on meat display-color stability.

Grain-finished, high-percentage Charolais steers (n = 36) were selected for uniformity. Immediately after jugular vein exsanguination, 27 steers were infused at 10% of live weight via the carotid artery with a solution developed by MPSC, Inc. (St. Paul, MN) consisting of 98.52% water, 0.97% saccharides, 0.23% sodium chloride, and 0.28% phosphate blend plus either 500 ppm vitamin C (MPSC+C; n = 9), 500 ppm vitamin E (MPSC+E; n = 9), or 500 ppm vitamin C + 500 ppm vitamin E (MPSC+C+E; n = 9). Uninfused controls (CON) were exsanguinated conventionally. Carcasses were fabricated at 48 h postmortem. Longissimus thoracis (LT), psoas major (PM), and semimembranosus (SM) muscles were removed, vacuum-packaged, and stored at 2 degrees C until 14 d postmortem. Then, steaks 2.54 cm thick were sliced from the three muscles, placed on foam trays, and overwrapped with polyvinyl chloride film. Ground beef (GB) was formulated from the quadriceps femoris to contain 20% fat, mounded into 0.45-kg portions, placed on styrofoam trays, and wrapped with polyvinyl chloride film. Steaks were visually evaluated for uniformity and initial color on display d 0. Instrumental color measurements of L*, a*, b* and trained sensory panel color evaluations were obtained daily for 4 d (PM and GB) or 5 d (LT and SM) of display. No display time x treatment interaction existed for L*, a*, or b* values. The LT from CON cattle had more uniform color (P < 0.05) and was more cherry red than that from all infused cattle on d 0. Visual scores indicated that GB from MPSC+E cattle was more red (P < 0.05) than that from MPSC+C infused cattle throughout display, and GB from MPSC+E cattle was more red (P < 0.05) than that from CON cattle for the last 3 d of display. The vascular infusion solutions generally did not improve color or display-color stability of steaks, but the infusion solution with vitamin E did improve display-color stability of GB.     

The response of pigs experimentally infected with Trypanosoma brucei to isometamidium chloride therapy and the relation to nutrition.

Growing pigs were placed on feeds with high (Group A), medium (B) and low (C) dietary energy and were infected with a virulent stock of T. brucei. Eight weeks later, the infected pigs were treated with isometamidium chloride at 1 mg/kg live weight and all pigs were subsequently placed on a high energy diet to investigate their response to therapy. Clearance of T. brucei from blood was completed 72h after treatment. There was no evidence of relapsed infection up to eight weeks after treatment. Red blood cell parameters returned to normal four to six weeks after treatment with responses being fastest in Group A, B and C had gained about two-thirds of the live weight gains of their non-infected pair-fed controls. It appears that the retarded weight gain as a result of the infection persisted after therapy since drug-treated pigs did not gain as much weight as their non-infected controls.     

Suggested dosage rates of melarsoprol in the treatment of mice experimentally infected with Trypanosoma brucei gambiense

One group of BALB/c mice infected with a highly virulent strain of Trypanosoma brucei gambiense were treated intraperitoneally with three series of three injections (each injection of 10 mg/kg) of Mel-B separated by seven days of rest, while a second group was treated once by a single injection All the Mel-B treated mice in both experiments were negative for parasites when examined using either the wet blood film or buffy coat methods, but were intermittently PCR positive during the sampling period. We encourage the use of a repeat negative PCR test over a one month period in combination with corroborative clinical and parasitological investigation to be suggestive of cure in experimental animals previously infected with trypanosomosis. In view of the exorbitant costs of Mel-B and its extreme toxicity, we recommend that Mel-B be given as one course of two injections (each equivalent to 10 mg/kg) separated by 2 d of rest in experimentally infected rodent models.     

Effect of tetracycline administration on the efficacy of diminazene aceturate therapy and prophylaxis in Trypanosoma brucei infections of mice

The simultaneous administration, to Trypanosoma brucei infected mice, of rolitetracycline or oxytetracycline and diminazene aceturate appeared to have no effect on the initial trypanocidal action of the diminazene aceturate in that trypanosomes were cleared from the circulation. It also had no effect on the duration of the aparasitaemic period which follows diminazene aceturate treatment and the mice remained free of circulating trypanosomes for some time. However, if used prophylactically, relatively large amounts of tetracyclines (4 x 10 mg kg-1) administered with 40 mg kg-1 diminazene aceturate caused a reduction of the prophylactic period compared with those mice given only diminazene aceturate. This reduction in the prophylactic period is unlikely to have any practical significance in the combination diminazene aceturate/tetracycline treatment of domestic animals as diminazene aceturate is used therapeutically and not prophylactically in the control of trypanosomiasis.     

Spontaneous cure of domestic pigs experimentally infected by Trypanosoma brucei gambiense. Implications for the control of sleeping sickness

The existence of a pig reservoir for human African trypanosomosis (HAT) due to Trypanosoma brucei gambiense complicates the fight against this disease. This study, reports results obtained from pigs, which were inoculated with the blood of a person, suffering from HAT in Cameroon. The pigs were reared and kept in the shelter from all contact with Glossina, and monitored for 188 days. The seroconversion was checked by agglutination assays for trypanosomosis (CATT 1.3 and LATEX/T.b.gambiense). The parasitemia was measured by quantitative buffy coat method (QBC) and by polymerase chain reaction method (PCR). In addition, growth was recorded as well as blood counting and blood formulas. The results showed that the pigs were trypanotolerant and cure themselves in less than 6 months. It is concluded that sterilisation of this reservoir could be achieved by tsetse-control measures in 1 year. It confirms the strategy to complement screening and treatment of HAT with tsetse fly control measures.     

Effects of supplemental parenteral administration of vitamin E and selenium to Jerseys and Holsteins during the nonlactating period

OBJECTIVE: To determine effects of breed and supplemental administration of vitamin E and selenium (Se) during late gestation on circulating concentrations of these micronutrients in periparturient Jerseys and Holsteins. DESIGN: Randomized controlled clinical study. ANIMALS: 16 Jersey and 36 Holstein cows. PROCEDURE: Cows were allotted to blocks on the basis of breed and expected parturition date. Cows within blocks were randomly assigned to be given vitamin E or Se parenterally 3 to 4 weeks prior to anticipated parturition in a 2 x 2 factorial design. RESULTS: Results of ANOVA indicated Jerseys had higher blood concentrations of Se and lower serum concentrations of vitamin E than Holsteins at the end of lactation. Jerseys had higher blood concentrations of Se than Holsteins 3 to 4 weeks prior to parturition and at parturition. Selenium administration increased blood concentrations of Se at parturition. Administration of nutrients did not affect serum concentrations of vitamin E at parturition or 2 to 3 weeks after parturition or blood concentrations of Se 2 to 3 weeks after parturition. CONCLUSIONS AND CLINICAL RELEVANCE: Jerseys and Holsteins consuming rations of comparable Se content differ in blood concentrations of Se during the nonlactating period, suggesting breed-related differences in Se metabolism during late lactation and the nonlactating period. Parenteral administration of Se 3 to 4 weeks prior to anticipated parturition increased blood concentrations of Se at parturition; however, Se concentrations of both groups at parturition were considered within the reference range for clinically normal cattle.     

Interference in the establishment of tsetse-transmitted Trypanosoma congolense, T. brucei or T. vivax superinfections in goats already infected with T. congolense or T. vivax

An interference phenomenon that delays superinfection with a trypanosome species different from that used for the initial infection has been found to occur in goats. Following tsetse transmission of Trypanosoma brucei to goats already infected with T. congolense, there was a delay in chancre development, as well as in the appearance of T. brucei and anti-T. brucei antibodies in the blood when compared to previously uninfected goats. However, there was no delay in the establishment of a tsetse-transmitted superinfection with T. vivax in goats already infected with either T. congolense or in animals already infected with a different serodeme of T. vivax.     

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.