A study on African animal trypanosomosis in four areas of Senegal.

In Senegal, several areas provide great potential for agriculture and animal production, but African animal trypanosomosis (AAT) is one of the major constraints to the development of more effective livestock production systems. A study was conducted to assess the current situation of AAT in this country. Surveys were carried out between June 2011 and September 2012 in four different areas: Dakar, Sine Saloum, Kedougou region and Basse Casamance in several animal species: dogs (152), donkeys (23), horses (63), sheep (43), goats (52) and cattle (104), distributed in the four sites. Molecular tools (PCR) indicated 3.4% positive animals including dogs, donkeys, a goat and cattle. The savannah type of Trypanosoma congolense Broden, 1904 (53% of positive cases) and the forest type of T. congolense (subgenus Nannomonas Hoare, 1964) were predominant. Trypanosoma vivax Ziemann, 1905 (subgenus Duttonella Chalmers, 1918) was only present in one animal and no trypanosome of the subgenus Trypanozoon Lühe, 1906 was found. Half of the positive cases were detected in Sine Saloum, where T. congolense savannah-type was predominant, and the other half in Basse Casamance, where T. congolense forest-type was predominant; no cases were found in Dakar or in the Kedougou region. A high risk of infection in dogs with T. congolense savannah-type was shown in Sine Saloum, requiring prevention and control of dogs in this area. The involvement of tsetse flies in the transmission of T. congolense in Sine Saloum and Basse Casamance is discussed.

The Trypanosoma brucei gambiense secretome impairs lipopolysaccharide-induced maturation, cytokine production, and allostimulatory capacity of dendritic cells.

Trypanosoma brucei gambiense, a parasitic protozoan belonging to kinetoplastids, is the main etiological agent of human African trypanosomiasis (HAT), or sleeping sickness. One major characteristic of this disease is the dysregulation of the host immune system. The present study demonstrates that the secretome (excreted-secreted proteins) of T. b. gambiense impairs the lipopolysaccharide (LPS)-induced maturation of murine dendritic cells (DCs). The upregulation of major histocompatibility complex class II, CD40, CD80, and CD86 molecules, as well as the secretion of cytokines such as tumor necrosis factor alpha, interleukin-10 (IL-10), and IL-6, which are normally released at high levels by LPS-stimulated DCs, is significantly reduced when these cells are cultured in the presence of the T. b. gambiense secretome. Moreover, the inhibition of DC maturation results in the loss of their allostimulatory capacity, leading to a dramatic decrease in Th1/Th2 cytokine production by cocultured lymphocytes. These results provide new insights into a novel efficient immunosuppressive mechanism directly involving the alteration of DC function which might be used by T. b. gambiense to interfere with the host immune responses in HAT and promote the infectious process.

The bacterial flora of tsetse fly midgut and its effect on trypanosome transmission.

The tsetse fly, Glossina palpalis is a vector of the trypanosome that causes sleeping sickness in humans and nagana in cattle along with associated human health problems and massive economic losses. The insect is also known to carry a number of symbionts such as Sodalis, Wigglesworthia, Wolbachia whose effects on the physiology of the insect have been studied in depth. However, effects of other bacterial flora on the physiology of the host and vector competence have received little attention. Epidemiological studies on tsetse fly populations from different geographic sites revealed the presence of a variety of bacteria in the midgut. The most common of the flora belong to the genera Entrobacter (most common), Enterococcus, and Acinetobacter. It was a little surprising to find such diversity in the tsetse midgut since the insect is monophagous consuming vertebrate blood only. Diversity of bacteria is normally associated with polyphagous insects. In contrast to the symbionts, the role of resident midgut bacterial flora on the physiology of the fly and vector competence remains to be elucidated. With regard, Sodalis glossinidius, our data showed that flies harbouring this symbiont have three times greater probability of being infected by trypanosomes than flies without the symbiont. The data delineated in these studies under score the need to carry out detailed investigations on the role of resident bacteria on the physiology of the fly and vector competence.

Population genetics of Trypanosoma brucei gambiense, the agent of sleeping sickness in Western Africa.

Human African trypanosomiasis, or sleeping sickness caused by Trypanosoma brucei gambiense, occurs in Western and Central Africa. T. brucei s.l. displays a huge diversity of adaptations and host specificities, and questions about its reproductive mode, dispersal abilities, and effective size remain under debate. We have investigated genetic variation at 8 microsatellite loci of T. b. gambiense strains isolated from human African trypanosomiasis patients in the Ivory Coast and Guinea, with the aim of knowing how genetic information was partitioned within and between individuals in both temporal and spatial scales. The results indicate that (i) migration of T. b. gambiense group 1 strains does not occur at the scale of West Africa, and that even at a finer scale (e.g., within Guinea) migration is restricted; (ii) effective population sizes of trypanosomes, as reflected by infected hosts, are probably higher than what the epidemiological surveys suggest; and (iii) T. b. gambiense group 1 is most likely a strictly clonally reproducing organism.

Bacterial diversity associated with populations of Glossina spp. from Cameroon and distribution within the Campo sleeping sickness focus.

Tsetse flies were sampled in three villages of the Campo sleeping sickness focus in South Cameroon. The aim of this study was to investigate the flies' gut bacterial composition using culture-dependent techniques. Out of the 32 flies analyzed (27 Glossina palpalis palpalis, two Glossina pallicera, one Glossina nigrofusca, and two Glossina caliginea), 17 were shown to be inhabited by diverse bacteria belonging to the Proteobacteria, the Firmicutes, or the Bacteroidetes phyla. Phylogenetic analysis based on 16S rRNA gene sequences indicated the presence of 16 bacteria belonging to the genera Acinetobacter (4), Enterobacter (4), Enterococcus (2), Providencia (1), Sphingobacterium (1), Chryseobacterium (1), Lactococcus (1), Staphylococcus (1), and Pseudomonas (1). Using identical bacterial isolation and identification processes, the diversity of the inhabiting bacteria analyzed in tsetse flies sampled in Cameroon was much higher than the diversity found previously in flies collected in Angola. Furthermore, bacterial infection rates differed greatly between the flies from the three sampling areas (Akak, Campo Beach/Ipono, and Mabiogo). Last, the geographic distribution of the different bacteria was highly uneven; two of them identified as Sphingobacterium spp. and Chryseobacterium spp. were only found in Mabiogo. Among the bacteria identified, several are known for their capability to affect the survival of their insect hosts and/or insect vector competence. In some cases, bacteria belonging to a given genus were shown to cluster separately in phylogenetic trees; they could be novel species within their corresponding genus. Therefore, such investigations deserve to be pursued in expanded sampling areas within and outside Cameroon to provide greater insight into the diverse bacteria able to infect tsetse flies given the severe human and animal sickness they transmit.

Trypanosoma brucei s.l.: Microsatellite markers revealed high level of multiple genotypes in the mid-guts of wild tsetse flies of the Fontem sleeping sickness focus of Cameroon.

To identify Trypanosoma brucei genotypes which are potentially transmitted in a sleeping sickness focus, microsatellite markers were used to characterize T. brucei found in the mid-guts of wild tsetse flies of the Fontem sleeping sickness focus in Cameroon. For this study, two entomological surveys were performed during which 2685 tsetse flies were collected and 1596 (59.2%) were dissected. Microscopic examination revealed 1.19% (19/1596) mid-gut infections with trypanosomes; the PCR method identified 4.7% (75/1596) infections with T. brucei in the mid-guts. Of these 75 trypanosomes identified in the mid-guts, Trypanosoma brucei gambiense represented 0.81% (13/1596) of them, confirming the circulation of human infective parasite in the Fontem focus. Genetic characterization of the 75 T. brucei samples using five microsatellite markers revealed not only multiple T. brucei genotypes (47%), but also single genotypes (53%) in the mid-guts of the wild tsetse flies. These results show that there is a wide range of trypanosome genotypes circulating in the mid-guts of wild tsetse flies from the Fontem sleeping sickness focus. They open new avenues to undertake investigations on the maturation of multiple infections observed in the tsetse fly mid-guts. Such investigations may allow to understand how the multiple infections evolve from the tsetse flies mid-guts to the salivary glands and also to understand the consequence of these evolutions on the dynamic (which genotype is transmitted to mammals) of trypanosomes transmission.

Tsetse flies, trypanosomes, humans and animals: what is proteomics revealing about their crosstalks?

Human and animal African trypanosomoses, or sleeping sickness and Nagana, are neglected vector-borne parasitic diseases caused by protozoa belonging to the Trypanosoma genus. Advances in proteomics offer new tools to better understand host-vector-parasite crosstalks occurring during the complex parasitic developmental cycle, and to determine the outcome of both transmission and infection. In this review, we summarize proteomics studies performed on African trypanosomes and on the interactions with their vector and mammalian hosts. We discuss the contributions and pitfalls of using diverse proteomics tools, and argue about the interest of pathogenoproteomics, both to generate advances in basic research on the best knowledge and understanding of host-vector-pathogen interactions, and to lead to the concrete development of new tools to improve diagnosis and treatment management of trypanosomoses in the near future.

Exocytosis and protein secretion in Trypanosoma.

BACKGROUND: Human African trypanosomiasis is a lethal disease caused by the extracellular parasite Trypanosoma brucei. The proteins secreted by T. brucei inhibit the maturation of dendritic cells and their ability to induce lymphocytic allogenic responses. To better understand the pathogenic process, we combined different approaches to characterize these secreted proteins. RESULTS: Overall, 444 proteins were identified using mass spectrometry, the largest parasite secretome described to date. Functional analysis of these proteins revealed a strong bias toward folding and degradation processes and to a lesser extent toward nucleotide metabolism. These features were shared by different strains of T. brucei, but distinguished the secretome from published T. brucei whole proteome or glycosome. In addition, several proteins had not been previously described in Trypanosoma and some constitute novel potential therapeutic targets or diagnostic markers. Interestingly, a high proportion of these secreted proteins are known to have alternative roles once secreted. Furthermore, bioinformatic analysis showed that a significant proportion of proteins in the secretome lack transit peptide and are probably not secreted through the classical sorting pathway. Membrane vesicles from secretion buffer and infested rat serum were purified on sucrose gradient and electron microscopy pictures have shown 50- to 100-nm vesicles budding from the coated plasma membrane. Mass spectrometry confirmed the presence of Trypanosoma proteins in these microvesicles, showing that an active exocytosis might occur beyond the flagellar pocket. CONCLUSIONS: This study brings out several unexpected features of the secreted proteins and opens novel perspectives concerning the survival strategy of Trypanosoma as well as possible ways to control the disease. In addition, concordant lines of evidence support the original hypothesis of the involvement of microvesicle-like bodies in the survival strategy allowing Trypanosoma to exchange proteins at least between parasites and/or to manipulate the host immune system.

Excreted/secreted proteins from trypanosome procyclic strains.

Trypanosoma secretome was shown to be involved in parasite virulence and is suspected of interfering in parasite life-cycle steps such as establishment in the Glossina midgut, metacyclogenesis. Therefore, we attempted to identify the proteins secreted by procyclic strains of T. brucei gambiense and T. brucei brucei, responsible for human and animal trypanosomiasis, respectively. Using mass spectrometry, 427 and 483 nonredundant proteins were characterized in T. brucei brucei and T. brucei gambiense secretomes, respectively; 35% and 42% of the corresponding secretome proteins were specifically secreted by T. brucei brucei and T. brucei gambiense, respectively, while 279 proteins were common to both subspecies. The proteins were assigned to 12 functional classes. Special attention was paid to the most abundant proteases (14 families) because of their potential implication in the infection process and nutrient supply. The presence of proteins usually secreted via an exosome pathway suggests that this type of process is involved in trypanosome ESP secretion. The overall results provide leads for further research to develop novel tools for blocking trypanosome transmission.

Development and application of an antibody-ELISA to follow up a Trypanosoma evansi outbreak in a dromedary camel herd in France.

An outbreak of trypanosomosis was observed for the first time in metropolitan France in October 2006, when five camels were proved to be infected by Trypanosoma evansi using parasitological methods. The parasite was isolated and used to produce a soluble antigen for antibody-enzyme linked immunosorbent assay (ELISA) in a protocol derived from a method previously developed for sheep and humans but using protein A conjugate. The animals were treated on three instances, alternatively with melarsomine hydrochloride and quinapyramine and followed up on a monthly basis for 2 years with various diagnostic techniques including parasitological, serological and DNA-based methods. Initially, five animals were detected as being positive using ELISA with 83.3% concordance to parasitological tests. Immediately after the first treatment, parasites and DNA disappeared in all animals; antibody levels decreased regularly until ELISA became negative 3-4 months later. Ten months after the first treatment, parasites and antibodies were detected again in one of the camels previously found to be infected. A retrospective study indicated that the weight of this animal had been underestimated; consequently, it had received underdosages of both trypanocides. However, since hypotheses of re-infection or relapse could not be fully substantiated, it is not known whether the ELISA results for this animal were true- or false-negative over a 7-month period. The study confirmed the value of this ELISA using protein A conjugate to detect antibodies directed against T. evansi in camels and the need to use several diagnostic techniques to optimize detection of infected animals. A warning is raised on surra, a potentially emerging disease in Europe.

Virulence and pathogenicity patterns of Trypanosoma brucei gambiense field isolates in experimentally infected mouse: differences in host immune response modulation by secretome and proteomics.

Human African trypanosomiasis is characterised by an important clinical diversity. Although Trypanosoma brucei gambiense field stocks isolated from patients in the same focus did not exhibit apparent genetic variability, they showed marked differences in terms of virulence (capacity to multiply inside a host) and pathogenicity (ability of producing mortality) in experimental murine infections. Two strains exhibiting opposite pathogenic and virulence properties in mouse were further investigated through their host-parasite interactions. In vitro, parasite bloodstream forms or soluble factors (or secretome) from both strains induced macrophage arginase as a function of their virulence. Arginase expression, a hallmark of macrophage alternative activation pathway, favours trypanosome bloodstream forms development. Moreover, a comparative proteomic study of the trypanosome stocks' secretomes evidenced both a differential expression of common molecules and the existence of stock specific molecules. This highlighted the potential involvement of the differential expression of the same genome in the diverse infectious properties of trypanosomes.

Genetic characterisation of Trypanosoma brucei s.l. using microsatellite typing: new perspectives for the molecular epidemiology of human African trypanosomiasis.

The pathogenic agent of human African trypanosomiasis (HAT) is a trypanosome belonging to the species Trypanosoma brucei s.l. Molecular methods developed for typing T. brucei s.l. stocks are for the most part not polymorphic enough to study genetic diversity within T. brucei gambiense (T. b. gambiense) group 1, the main agent of HAT in West and Central Africa. Furthermore, these methods require high quantities of parasite material and consequently are hampered by a selection bias of the isolation and cultivation techniques. In this study, we evaluated the potential value of microsatellite markers (eight loci) in the genetic characterisation of T. brucei s.l. compared to the multi-locus enzyme electrophoresis reference technique. Stocks isolated in Ivory Coast and reference stocks were used for this purpose. Microsatellite markers were shown to be polymorphic enough to evidence the existence of genetic diversity within T. b. gambiense group 1 and to show the existence of mixed infections. Furthermore, they were able to amplify trypanosome DNA directly from field samples without the usual culturing stages. While the ability of microsatellite markers to detect mixed infections in such field samples is currently being discussed, they appear to be useful to study the parasite population's geographical structure and may provide new insight into their reproductive mode, a topic that is still under debate. Thus, use of microsatellite markers will contribute to the study of the influence of parasite genetics in the diversity of responses to HAT and may contribute to the improvement of HAT molecular diagnosis.

Towards understanding the presence/absence of Human African Trypanosomosis in a focus of Côte d'Ivoire: a spatial analysis of the pathogenic system.

BACKGROUND: This study aimed at identifying factors influencing the development of Human African Trypanosomosis (HAT, or sleeping sickness) in the focus of Bonon, located in the mesophile forest of Côte d'Ivoire. A previous study mapping the main daytime activity sites of 96 patients revealed an important disparity between the area south of the town- where all the patients lived- and the area north of the town, apparently free of disease. In order to explain this disparity, we carried out a spatial analysis of the key components of the pathogenic system, i.e. the human host, the tsetse vector and the trypanosomes in their environment using a geographic information system (GIS). RESULTS: This approach at the scale of a HAT focus enabled us to identify spatial patterns which linked to the transmission and the dissemination of this disease. The history of human settlement (with the rural northern area exploited much earlier than the southern one) appears to be a major factor which determines the land use pattern, which itself may account for differences found in vector densities (tsetse were found six times more abundant in the southern rural area than in the northern). Vector density, according to the human and environmental context in which it is found (here an intense mobility between the town of Bonon and the rural areas), may explain the observed spatial differences in HAT prevalence. CONCLUSION: This work demonstrates the role of GIS analyses of key components of the pathogenic system in providing a better understanding of transmission and dissemination of HAT. Moreover, following the identification of the most active transmission areas, and of an area unfavourable to HAT transmission, this study more precisely delineates the boundaries of the Bonon focus. As a follow-up, targeted tsetse control activities starting north of Bonon (with few chances of reinvasion due to very low densities) going south, and additional medical surveys in the south will be proposed to the Ivoirian HAT control program to enhance the control of the disease in this focus. This work also shows the evolution of HAT regarding time and environment, and the methodology used may be able to predict possible sleeping sickness development/extinction in areas with similar history and space organization.

Identification of Trypanosoma brucei circulating in a sleeping sickness focus in Côte d'Ivoire: assessment of genotype selection by the isolation method.

Genetic studies of Trypanosoma brucei have been mainly based on rodent inoculation (RI) for isolation of trypanosome strains. However, Trypanosoma brucei gambiense is difficult to grow in rodents. The development and use of the Kit for In Vitro Isolation (KIVI) of trypanosomes has led to a better isolation success. However, some authors report a genetic monomorphism in T. b. gambiense, and the extensive use of the KIVI was suspected as being responsible for this low genetic diversity. In the present work, trypanosome stocks were isolated from both humans and pigs in an active sleeping sickness focus in Côte d'Ivoire. Two methods were simultaneously used for this purpose: KIVI and rodent inoculation. None of the human stocks grew in rodents. Some of the stocks originating from pigs could be isolated with both methods. Each of these stocks (from the same pig) showed a different isoenzymatic pattern according to the isolation method used. All the human stocks identified belonged to the major zymodeme 3 of T. b. gambiense group 1, whereas the stocks isolated from pigs belonged to a new group of zymodemes even if they were genetically closely related. These observations may have significant implications when analysing the population structure of T. brucei, and also raise again the question of the importance of the animal reservoir in Human African Trypanosomiasis (HAT).

Genetic variability within Trypanosoma brucei gambiense: evidence for the circulation of different genotypes in human African trypanosomiasis patients in Côte d'Ivoire.

For 23 Ivoirian patients infected by Trypanosoma-brucei gambiense, isolation and genetic characterization using PCR and microsatellite primers were performed (in 1996-99) using 2 different isolates (A and B) from each patient. When using TBDAC 1/2, 7 genotypes were observed, and DNAs A and B for 2 patients were different. This might be the first evidence of the presence of 2 different genotypes of T. b. gambiense group 1 in the same patient.

PCR identification of Trypanosoma lewisi, a common parasite of laboratory rats.

Trypanosoma (Herpetosoma) lewisi is a trypanosome of the sub-genus Herpetosoma (Stercoraria section), parasite of rats (Rattus rattus and Rattus norvegicus) transmitted by fleas. T. lewisi has a stringent species specificity and cannot grow in other rodents such as mice. Rats are infected principally by oral route, through contamination by flea faeces or ingestion of fleas. Trypanosoma lewisi infections in rat colonies can interfere with research protocols and fleas of wild rats are often the source of such infections. Currently, diagnosis of T. lewisi in rats is performed by microscopic observation of stained blood smears. In the course of a research project at CIRDES, a T. lewisi infection was detected in the rat colony. In this study we evaluated PCR primer sets for their ability to diagnose multiple species of trypanosomes with a single amplification. We show that the use of ITS1 sequence of ribosomal DNA provides an efficient and sensitive assay for detection and identification of T. lewisi infection in rats and recommend the use of this assay for monitoring of T. lewisi infections in rat colonies.

[Contributions and limits of the diagnosis of human African trypanosomiasis]. / Apports et limites du diagnostic de la trypanosomiase humaine africaine.

Human African trypanosomiasis, or sleeping sickness, is still a worrying problem in Africa. Sleeping sickness is a disease for which a systematic monitoring is necessary, particularly for the trypanosomiasis caused by Trypanosoma brucei gambiense, which is characterized by a long asymptomatic stage. In the absence of specific clinical signs, mass screening of populations remains the only way to control the disease and to avoid its spreading. The lack of sensitivity and specificity of the diagnosis tests classically used led to the development of molecular tools. PCR amplification of parasite specific sequences has considerably improved the diagnostic of the parasitic infection, the stage diagnosis as well as the post-therapeutic follow-up. But there are limits with a use in routine and research is still necessary to make PCR a real tool for control of sleeping sickness.

Population genetics of Trypanosoma brucei circulating in Glossina palpalis palpalis and domestic animals of the Fontem sleeping sickness focus of Cameroon.

BACKGROUND: Human African Trypanosomiasis is still a public health threat in Cameroon. To assess Trypanosoma brucei strains circulating in the Fontem sleeping sickness focus, we conducted a genetic structure study using microsatellites to assess genotypes circulating in both tsetse flies and domestic animals. METHOD: For this study, pyramidal traps were set up and 2695 tsetse flies were collected and 1535 (57%) living flies were dissected and their mid-guts collected. Furthermore, blood samples were collected from 397 domestic animals (pigs, goats, sheep and dogs). DNA was extracted from midguts and blood samples, and specific primers were used to identify trypanosomes of the subgenus Trypanozoon. All positive samples were genetically characterized with seven microsatellite markers. RESULTS: Seventy five (4.7%) midguts of tsetse flies and 140 (35.2%) domestic animals were found infected by trypanosomes of the subgenus Trypanozoon. The genetic characterization of 215 Trypanozoon positive samples (75 from tsetse and 140 from animals) revealed a genetic diversity between Trypanosoma brucei circulating in tsetse and domestic animals. Of these positive samples, 87 (40.5%) single infections were used here to investigate the population genetics of Trypanosoma brucei circulating in tsetse and domestic animals. The dendrogram illustrating the genetic similarities between Trypanosoma brucei genotypes was subdivided into four clusters. The samples from tsetse belonged to the same cluster whereas the samples from domestic animals and espcially pigs were distributed in the four clusters. CONCLUSION: Pigs appeared as the animal species harboring the highest number of different Trypanosoma brucei strains. They may play an important role in the propagation of different genotypes. The FST values revealed a sub structuration of Trypanosoma brucei according to hosts and sometimes villages. The data obtained from this study may have considerable importance for the understanding of the transmission and the spread of specific genotypes of Trypanosoma brucei.

Secreted proteases of Trypanosoma brucei gambiense: possible targets for sleeping sickness control?

Human African trypanosomiasis (HAT) is caused by trypanosomes of the species Trypanosoma brucei and belongs to the neglected tropical diseases. Presently, WHO has listed 36 countries as being endemic for sleeping sickness. No vaccine is available, and disease treatment is difficult and has life-threatening side effects. Therefore, there is a crucial need to search for new therapeutic targets against the parasite. Trypanosome excreted-secreted proteins could be promising targets, as the total secretome was shown to inhibit, in vitro, host dendritic cell maturation and their ability to induce lymphocytic allogenic responses. The secretome was found surprisingly rich in various proteins and unexpectedly rich in diverse peptidases, covering more than ten peptidase families or subfamilies. Given their abundance, one may speculate that they would play a genuine role not only in classical "housekeeping" tasks but also in pathogenesis. The paper reviews the deleterious role of proteases from trypanosomes, owing to their capacity to degrade host circulating or structural proteins, as well as proteic hormones, causing severe damage and preventing host immune response. In addition, proteases account for a number of drug targets, such drugs being used to treat severe diseases such AIDS. This review underlines the importance of secreted proteins and especially of secreted proteases as potential targets in HAT-fighting strategies. It points out the need to conduct further investigations on the specific role of each of these various proteases in order to identify those playing a central role in sleeping sickness and would be suitable for drug targeting.

Chemoprophylaxis and treatment of African canine trypanosomosis in French military working dogs: a retrospective study.

African trypanosomosis is a major threat to livestock production in sub-Saharan Africa. Although the disease mainly concerns cattle, dogs can also be infected by Trypanosoma spp. transmitted by tsetse flies. Between 1997 and 2003, the parasite Trypanosoma congolense was identified in French military dogs sent to Africa. On infected dogs, the diagnosis was made during the mission or just after the return to France, depending on when the symptoms appeared. The high incidence and mortality rate among these dogs led veterinarians of the French Health Service to implement a systematic chemoprophylaxis beginning in 2004. Between 2004 and 2011, the chemoprophylaxis was carried out on more than 400 military dogs. The protocol of chemoprophylaxis relies on the use of isometamidium chloride (Trypamidium(®), Merial). The drug has been used successfully at the dosage of 1mg/kg body weight by deep intramuscular injection, every two or three months. In addition, dogs are given collars impregnated with deltamethrin (Scalibor(®), MSD Animal Health). Isometamidium chloride was also used successfully in the treatment of military dogs infected with T. congolense, with a full recovery and without any relapses.