This work investigated the mechanical transmission of Trypanosoma vivax by Stomoxys calcitrans to cattle in a region without a cyclic vector. The study involved two experiments, one with calves experimentally infected with T. vivax, in the acute phase of trypanosomosis (Experiment 1) and the other in the chronic phase (Experiment 2). In both experiments, two transmission methods were used with flies that had not fed for 24 h or had never fed: (i) Method 1: flies released freely in cattle pens (≈3,300 flies/pen for 10 days); and (ii) Method 2: flies placed in a feeding chamber (12 flies/animal). To develop Method 1 in the two experiments (acute and chronic phases), T. vivax-positive animals were kept with T. vivax-negative animals. Periodically, the Brener method, Woo method, blood smears, cPCR, ELISA, IFAT, and Imunoteste® were performed to detect T. vivax in the animals. We also recorded the animals’ head tossing and hoof stomping and the number of flies near the pens’ inner walls. Subsequently, biological testing was performed using lambs. For Method 2 in both experiments, flies inside the feeding chamber first fed on T. vivax-positive animals and later on negative animals. In both experiments and methods, we examined the flies for the presence of T. vivax through blood smears and cPCR of the proboscis and abdomen. In Experiment 2 (chronic phase), a test was conducted to determine how long trypomastigotes forms could survive on the blood of animals with different levels of parasitemia. None of the animals (calves and lambs) became infected with T. vivax or showed antibodies against it. During the evaluation period, the animals in the presence of the flies exhibited more hoof stomping and head tossing compared to those without flies (control). Additionally, there was an increase in the number of flies in the pens during the experiment. Only in Experiment 1 (acute phase) were T. vivax trypomastigotes and DNA found in the abdomen of the flies but not in the proboscis. In Experiment 2 (chronic phase), higher concentrations of trypomastigotes per milliliter of blood were associated with a shorter the lifespan of this stage of the parasite. In conclusion, under the variable conditions of the experiments (hosts, number of flies, and level of parasitemia), S. calcitrans was unable to mechanically transmit T. vivax to cattle.

这项工作研究了在没有循环载体的地区，间日锥虫通过Stomoxys calcitrans向牛的机械传播。该研究涉及两项实验，一项是在锥虫病的急性期（实验 1），用实验性感染间日锥虫的小牛进行实验，另一项是在慢性期（实验 2）。在这两个实验中，对24小时未进食或从未进食的苍蝇使用了两种传播方法：（i）方法1：在牛栏内自由释放苍蝇（约3,300只苍蝇/栏，10天）； (ii) 方法 2：将苍蝇放入饲养室（12 只苍蝇/动物）。为了在两个实验（急性期和慢性期）中开发方法1，将间日疟原虫阳性动物与间日疟原虫阴性动物一起饲养。定期使用 Brener 法、Woo 法、血涂片、cPCR、ELISA、IFAT 和 Imunoteste® 检测动物体内的间日疟原虫。我们还记录了动物的摇头和蹄踏以及围栏内壁附近的苍蝇数量。随后，用羔羊进行了生物学测试。对于两个实验中的方法2，饲养室内的苍蝇首先喂食间日疟原虫阳性动物，然后喂食阴性动物。在这两种实验和方法中，我们通过血涂片和鼻部和腹部的 cPCR 检查果蝇是否存在间日疟原虫。在实验2（慢性期）中，进行了一项测试以确定锥鞭毛体形式可以在具有不同寄生虫血症水平的动物的血液中存活多长时间。没有动物（牛犊和羔羊）感染间日疟原虫或表现出针对它的抗体。 在评估期间，与没有苍蝇的动物（对照）相比，有苍蝇存在的动物表现出更多的跺蹄和摇头行为。此外，实验期间围栏内的苍蝇数量有所增加。仅在实验 1（急性期）中，果蝇腹部发现了间日疟原虫锥鞭毛体和 DNA，但在其长鼻中未发现。在实验 2（慢性期）中，每毫升血液中较高浓度的锥鞭毛体与该阶段寄生虫的寿命较短有关。总之，在不同的实验条件（宿主、苍蝇数量和寄生虫血症水平）下， S. calcitrans无法将间日疟原虫机械传播给牛。