Innate and acquired resistance to African trypanosomiasis

A novel approach for identification of zoonotic trypanosome utilizing deep metric learning and vector database-based image retrieval system

Trypanosomiasis, a significant health concern in South America, South Asia, and Southeast Asia, requires active surveys to effectively control the disease. To address this, we have developed a hybrid model that combines deep metric learning (DML) and image retrieval. This model is proficient at identifying Trypanosoma species in microscopic images of thin-blood film examinations. Utilizing the ResNet50 backbone neural network, a trained-model has demonstrated outstanding performance, achieving an accuracy exceeding 99.71 % and up to 96 % in recall. Acknowledging the necessity for automated tools in field scenarios, we demonstrated the potential of our model as an autonomous screening approach. This was achieved by using prevailing convolutional neural network (CNN) applications, and vector database based-images returned by the KNN algorithm. This achievement is primarily attributed to the implementation of the Triplet Margin Loss function as 98 % of precision. The robustness of the model demonstrated in five-fold cross-validation highlights the ResNet50 neural network, based on DML, as a state-of-the-art CNN model as AUC >98 %. The adoption of DML significantly improves the performance of the model, remaining unaffected by variations in the dataset and rendering it a useful tool for fieldwork studies. DML offers several advantages over conventional classification model to manage large-scale datasets with a high volume of classes, enhancing scalability. The model has the capacity to generalize to novel classes that were not encountered during training, proving particularly advantageous in scenarios where new classes may consistently emerge. It is also well suited for applications requiring precise recognition, especially in discriminating between closely related classes. Furthermore, the DML exhibits greater resilience to issues related to class imbalance, as it concentrates on learning distances or similarities, which are more tolerant to such imbalances. These contributions significantly make the effectiveness and practicality of DML model, particularly in in fieldwork research.

Current Treatments to Control African Trypanosomiasis and One Health Perspective

Human African Trypanosomiasis (HAT, sleeping sickness) and Animal African Trypanosomiasis (AAT) are neglected tropical diseases generally caused by the same etiological agent, Trypanosoma brucei. Despite important advances in the reduction or disappearance of HAT cases, AAT represents a risky reservoir of the infections. There is a strong need to control AAT, as is claimed by the European Commission in a recent document on the reservation of antimicrobials for human use. Control of AAT is considered part of the One Health approach established by the FAO program against African Trypanosomiasis. Under the umbrella of the One Health concepts, in this work, by analyzing the pharmacological properties of the therapeutic options against Trypanosoma brucei spp., we underline the need for clearer and more defined guidelines in the employment of drugs designed for HAT and AAT. Essential requirements are addressed to meet the challenge of drug use and drug resistance development. This approach shall avoid inter-species cross-resistance phenomena and retain drugs therapeutic activity.

Livestock pathology in the central African region: some epidemiological considerations and control strategies

Disease consistently features among the major constraints of livestock production in the central African region, orchestrating important economic losses. This article reviews livestock diseases of economic importance, including foot-and-mouth disease, trypanosomosis and dermatophilosis in cattle, peste des petits ruminants and gastrointestinal helminthosis in sheep and goats, and Newcastle disease in poultry. Some aspects of epidemiology such as pathogen identification, prevalence and risk factors are examined in the light of research findings in the region. Control tools such as vaccines, chemotherapeutic or prophylactic agents, and protocols developed for their efficient use are also reviewed. Constraints to the effective use of these tools have been identified as mostly due to institutional insufficiencies and measures for improvement have been proposed. These include the promotion of private professional veterinary services endowed with greater responsibility in animal health care, creation and promotion of community-based animal health care units in areas of marginal professional coverage, and adoption of a regional approach to the control of diseases of economic importance.

Response of Trypanosoma vivax and Trypanosoma congolense in zebu cattle in North Cameroon to prophylactic treatment with two formulations of isometamidium

We tested the efficacy of two formulations of isometamidium in a tsetse-infested farm in North Cameroon from 20 August 2000 to 5 January 2001. A total of 90 adult cattle were used in three groups of 30 each corresponding to two treated and one untreated control. Drug efficacies were evaluated in terms of reduction of parasite incidence in the host's blood, maintenance of packed-cell volume (PCV) and weight gains. Both drugs reduced the incidence of parasites even though re-infections 2 weeks after treatment were common. PCV values were similar in both treated groups but higher than in the untreated control. Body weight changes followed a similar trend with the control losing weight from a mean of 427+/-119kg at the beginning to 398+/-93kg in 4 months. Weights increased from 375+/-76 and 396+/-110 to 396+/-69 and 418+/-112kg in the Veridium and Trypamidium groups, respectively. Efficacy was similar between the two formulations of isometamidium in the prophylaxis of bovine trypanosomosis. However, the presence of parasites in some animals barely 2 weeks after treatment suggested that either infections were not cleared or residual drug effects were not sufficient to prevent re-infections.

Serum resistance-associated protein blocks lysosomal targeting of trypanosome lytic factor in Trypanosoma brucei

Trypanosoma brucei brucei is the causative agent of nagana in cattle and can infect a wide range of mammals but is unable to infect humans because it is susceptible to the innate cytotoxic activity of normal human serum. A minor subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I (apoA-I), apolipoprotein L-I (apoL-I), and haptoglobin-related protein (Hpr) provides this innate protection against T. b. brucei infection. This HDL subfraction, called trypanosome lytic factor (TLF), kills T. b. brucei following receptor binding, endocytosis, and lysosomal localization. Trypanosoma brucei rhodesiense, which is morphologically and physiologically indistinguishable from T. b. brucei, is resistant to TLF-mediated killing and causes human African sleeping sickness. Human infectivity by T. b. rhodesiense correlates with the evolution of a resistance-associated protein (SRA) that is able to ablate TLF killing. To examine the mechanism of TLF resistance, we transfected T. b. brucei with an epitope-tagged SRA gene. Transfected T. b. brucei expressed SRA mRNA at levels comparable to those in T. b. rhodesiense and was highly resistant to TLF. In the SRA-transfected cells, intracellular trafficking of TLF was altered, with TLF being mainly localized to a subset of SRA-containing cytoplasmic vesicles but not to the lysosome. These results indicate that the cellular distribution of TLF is influenced by SRA expression and may directly determine the organism's susceptibility to TLF.

Insight into the mechanism of trypanosome lytic factor-1 killing of Trypanosoma brucei brucei

It has been known for almost a century that normal human serum can lyse the extracellular blood parasite Trypanosoma brucei brucei. This process is a result of a non-immune killing factor in human sera known as trypanosome lytic factor (TLF). In this work, we demonstrate that killing of T. b. brucei by trypanosome lytic factor-1 (TLF-1) in vitro is inhibited by the lipophyllic iron chelator, LI, the lipophyllic antioxidant DPPD, and the protease inhibitors antipain and E64. Thus TLF-1 killing likely requires iron, oxidants, and serine and cysteine proteases. Furthermore, we demonstrate that TLF-1 mediated lysis causes measurable peroxidation in T. brucei lipids via a reaction that is inhibited by DPPD, weak bases, and human haptoglobin. We hypothesize that TLF-1 lysis requires intracellular factors within the trypanosome including high intracellular H2O2 and high polyenoic lipid concentrations, lysosomal acidification and proteases, and intracellular iron sources. The data presented supports the hypothesis that the combination of these factors with TLF-1 inside the lysosome results in lysosomal membrane breakdown, release of the lysosomal contents, and subsequent autodigestion of the cell.