The transmission of mixed Trypanosoma brucei brucei/T. congolense infections by tsetse (Glossina morsitans morsitans)

Laboratory experiments and field observations clearly show that tsetse flies can be carriers of mixed trypanosome infections. Question remains how easy it is for the tsetse fly to acquire such a mixed infection during the first bloodmeal. This is of particular importance in the epidemiology of Trypanosoma brucei s.l., often a cryptic infection and difficult to transmit to non-teneral tsetse flies. To determine the transmission rate of T. brucei as part of a mixed infection, teneral Glossina morsitans morsitans were fed once on cattle with a mixed (Trypanosoma brucei brucei/Trypanosoma congolense) or single (T. brucei) infection. Of the 140 flies fed on animals with a mixed infection and examined 30 days later, 4 had a metacylic T. brucei infection, 29 a T. congolense infection and 13 a mixed T. brucei/T. congolense infection. There was no significant difference between the transmission rate of T. brucei as a single or as part of a mixed infection. The high proportion of mixed T.b. brucei/T. congolense infections was explained best by a model implying that if a fly is refractory to T. congolense, it is also refractory to T.b. brucei and vice versa. Hence, results suggest that the transmission of T.b. brucei is affected mainly by the vectorial capacity of flies and not by concurrent trypanosome infections in the host.     

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.     

The effects of experimental Trypanosoma (trypanozoon) (brucei) evansi infection on the fertility of male goats

The effects on the fertility of small East African male goats of intravenous infection with Trypanosoma (t) (b) evansi were studied. Six infected bucks developed erratic, low but persistent parasitaemia, the packed cell volume dropped gradually but significantly (p<0.001) and they became emanciated. Half of these bucks developed clinical orchitis. Two bucks died of the disease during the experiment.Semen from all the infected bucks deteriorated in quality and quantity and those with clinical orchitis became totally aspermic. Spermatozoal abnormalities and the number of dead spermatozoa rose significantly. Later in the disease, the testicles of the infected bucks atrophied. Histologically, the testicles from the infected animals became devoid of spermatozoa, the testicular blood vessels contained microthrombi and there was infiltration of inflammatory cells. Subsequently, diffuse calcification set in, with calcium deposits obliterating most of the seminiferous vesicles and ducts and also the epididymal ducts.     

伊氏锥虫、马媾疫锥虫、布氏锥虫、刚果锥虫的18S rDNA部分序列测定与系统发育关系

对伊氏锥虫（Trypanosoma evansi）：新疆株（XJCA）、湖北株（HBM）、云南株（YNB）、广东株（GDB2）；马媾疫锥虫（Trypanosoma equiperdum）、布氏锥虫（Trypanosoma brucei）、刚果锥虫（Trypanosoma congolense）提取基因组DNA，根据已报道的伊氏锥虫株18SrDNA基因序列设计合成引物，用PCR扩增了锥虫虫株基因组DNA,伊氏锥虫新疆株、湖北株、云南株、广东株、布氏锥虫、刚果锥虫均为373bp的片段；马媾疫锥虫为372bp的片段，PCR产物经电泳鉴定后用试剂盒回收纯化，纯化后PCR产物经连接、转化后测序，将测得的序列用DNAMAN软件分析并与国外已发表的相应序列进行了同源性比较，并绘制了系统发育进化树。结果与国外AJ009153、AJ223564、D89527株同源性达到99％～100％，与另外11株同源性75％。本研究为锥虫分子流行病学研究及分类研究打下基础。     

Evaluation of conventional odour attractants for Glossina brevipalpis and Glossina austeni (Diptera: Glossinidae) in South Africa

The components of the synthetic ox-odour used in Zimbabwe against Glossina pallidipes and G. m. morsitans were evaluated for the attraction of G. brevipalpis and G. austeni in South Africa. The Zim babwe mixture (Zim-mix), which consisted or acetone and a 1:4:8 mixture of 3-n-propyl phenol, 4-methyl phenol and 1-octen-3-ol, increased the catches of G. brevipalpis by c. 2.1-4.4 times compared to when no odours were used. One of the odour components, namely 3-n-propyl phenol, did not significantly increase the size of the catches. Acetone was an essential component for G. brevipalpis, especially during the warm and wet season when it acted synergistically with high doses of 1-octen-3-ol and 4-methyl phenol. The most attractive odour combination for G. brevipalpis was 1-octen-3-ol released at 2.3-9.1 mg/h with 4-methyl phenol at c. 15.5 mg/h and acetone at c. 350 mg/h. This combination increased the catches by another 2.3-2.8 times when compared to the Zim-mix and 10.1-12.3 times compared to 'no odour'. None of the odour components was attractive for G. austeni. None of the components was repellent for either species.     

Evaluation of coloured targets for the attraction of Glossina brevipalpis and Glossina austeni (Diptera: Glossinidae) in South Africa

Studies on the attractiveness of various coloured targets for Glossina brevipalpis and G. austeni in South Africa showed black and pthalogen blue (p.blue) combinations to be the most effective for both species. A 2 m wide (all targets 1 m high) black/p.blue/black (colour ratio 1:2:1) conformation caught nearly three times more G. brevipalpis and nearly five times more G. austeni than a 1.5 m wide black standard control target. For G. brevipalpis the black/p.blue/black (1:2:1) target should be at least 2 m wide in order to increase catches significantly while a 1.5-2.0 m wide target is optimal for G. austeni. The p.blue section of a 2 m black/p.blue/black target should not make up less than 20% of the total target width for either species. The most effective combination of practical target sizes and colour ratios were a 1.75 m wide black/p.blue/black (1:1.5:1) or 2 m wide target (1.5:1:1.5). Between 61-95% of G. brevipalpis and 34-90% of G. austeni that were attracted, settled first on the black section of black/p.blue targets (> 1 m wide). Further studies revealed that for G. brevipalpis only the black parts of the 2 m wide target need to be treated with insecticide, while the entire 1.75 m wide target should be treated. For G. austeni the total width of either target should be treated with insecticide since this species readily settles on both blue and black.     

Development of Trypanosoma congolense, T vivax and T brucei in the skin reaction induced in goats by infected Glossina morsitans centralis: a light and electron microscopical study

The development and distribution of Trypanosoma congolense, T vivax and T brucei in the skin of goats was examined after the animals were bitten by infected Glossina morsitans centralis. Following the tsetse bite, the trypanosomes in the skin multiplied, reaching maximum numbers when the skin reaction (chancre) of the host attained its maximum size. In goats infected with T vivax and T brucei, trypanosomes were observed circulating in the blood before the peak of the chancre, while in T congolense-infected goats microscopically detectable parasites were found in blood only during the decline of the chancre. In contrast to T vivax, large numbers of T congolense and T brucei parasites were found in the skin following tsetse-transmitted infection. Ultrastructural differences were observed in T congolense and T brucei indicating an intracutaneous transformation from metacyclic to blood stream forms. T congolense forms in the skin reactions had a well developed secretory reticulum, small mitochondria and lacked large lipid inclusions compared to metacyclic and blood stream forms. The intracutaneous forms of T brucei had smaller mitochondria, the glycosomes were of more uniform size and the rough endoplasmic reticulum was less developed than in metacyclic or blood stream forms.