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Bovine trypanosomiasis is a significant health concern for livestock intensification in Côte d'Ivoire. This study aimed to determine the prevalence and distribution of pathogenic trypanosomes and identify the most infected cattle breed in northern Côte d'Ivoire. We examined 700 cattle and found that polymerase chain reaction (PCR) was more sensitive (12.3%) than microscopic observation (5.6%). Among the trypanosome species detected in naturally infected cattle, Trypanosoma vivax was 7.3%, Trypanosoma simiae tsavo was 6.7%, and Trypanosoma congolense was 0.4%. The overall prevalence of trypanosome infection in all cattle breeds was 12.3%, while the prevalence in individual breeds was 14.8%, 7.3%, 10.6%, and 12.3% for N'Dama, Baoule, Zebu, and Mere breed, respectively. The infected animals had low packed cell volume, influencing the prevalence. Our findings indicate that bovine trypanosomes are prevalent in Côte d'Ivoire, and their prevalence varies by region and breed. These pathogens include T. vivax, T. simiae tsavo, and T. congolense.

African trypanosomoses, whose pathogens are transmitted by tsetse flies, are a threat to animal and human health. Tsetse flies observed at the military base of the French Forces in Côte d'Ivoire (FFCI base) were probably involved in the infection and death of military working dogs. Entomological and parasitological surveys were carried out during the rainy and dry seasons using "Vavoua" traps to identify tsetse fly species, their distribution, favorable biotopes and food sources, as well as the trypanosomes they harbor. A total of 1185 Glossina palpalis palpalis tsetse flies were caught, corresponding to a high average apparent density of 2.26 tsetse/trap/day. The results showed a heterogeneous distribution of tsetse at the FFCI base, linked to more or less favorable biotopes. No significant variation in tsetse densities was observed according to the season. The overall trypanosomes infection rate according to microscopic observation was 13.5%. Polymerase chain reaction (PCR) analyses confirmed the presence of Trypanosoma vivax and T. congolense forest type, responsible for African animal trypanosomosis. Our findings suggest that there is a risk of introduction and transmission of T. brucei gambiense, responsible for human African trypanosomiasis, on the study site. This risk of transmission of African trypanosomes concerns not only the FFCI base, but also inhabited peripheral areas. Our study confirmed the need for vector control adapted to the eco-epidemiological context of the FFCI base., (© Y.J.R. Konan et al., published by EDP Sciences, 2023.)

Background: Work to control the gambiense form of human African trypanosomiasis (gHAT), or sleeping sickness, is now directed towards ending transmission of the parasite by 2030. In order to supplement gHAT case-finding and treatment, since 2011 tsetse control has been implemented using Tiny Targets in a number of gHAT foci. As this intervention is extended to new foci, it is vital to understand the costs involved. Costs have already been analysed for the foci of Arua in Uganda and Mandoul in Chad. This paper examines the costs of controlling Glossina palpalis palpalis in the focus of Bonon in Côte d'Ivoire from 2016 to 2017., Methodology/principal Findings: Some 2000 targets were placed throughout the main gHAT transmission area of 130 km2 at a density of 14.9 per km2. The average annual cost was USD 0.5 per person protected, USD 31.6 per target deployed of which 12% was the cost of the target itself, or USD 471.2 per km2 protected. Broken down by activity, 54% was for deployment and maintenance of targets, 34% for tsetse surveys/monitoring and 12% for sensitising populations., Conclusions/significance: The cost of tsetse control per km2 of the gHAT focus protected in Bonon was more expensive than in Chad or Uganda, while the cost per km2 treated, that is the area where the targets were actually deployed, was cheaper. Per person protected, the Bonon cost fell between the two, with Uganda cheaper and Chad more expensive. In Bonon, targets were deployed throughout the protected area, because G. p. palpalis was present everywhere, whereas in Chad and Uganda G. fuscipes fuscipes was found only the riverine fringing vegetation. Thus, differences between gHAT foci, in terms of tsetse ecology and human geography, impact on the cost-effectiveness of tsetse control. It also demonstrates the need to take into account both the area treated and protected alongside other impact indicators, such as the cost per person protected., Competing Interests: The authors have declared that no competing interests exist. Author Jean-Baptiste Rayaisse was unable to confirm their authorship contributions. On their behalf, the corresponding author has reported their contributions to the best of their knowledge.

Glossina palpalis palpalis remains the major vector of sleeping sickness in Côte d'Ivoire. The disease is still active at low endemic levels in Bonon and Sinfra foci in the western-central part of the country. In this study, we investigated the impact of a control campaign on G. p. palpalis population structure in Bonon and Sinfra foci in order to adapt control strategies. Genetic variation at microsatellite loci was used to examine the population structure of different G. p. palpalis cohorts before and after control campaigns. Isolation by distance was observed in our sampling sites. Before control, effective population size was high (239 individuals) with dispersal at rather short distance (731 m per generation). We found some evidence that some of the flies captured after treatment come from surrounding sites, which increased the genetic variance. One Locus, GPCAG, displayed a 1000% increase of subdivision measure after control while other loci only exhibited a substantial increase in variance of subdivision. Our data suggested a possible trap avoidance behaviour in G. p. palpalis. It is important to take into account and better understand the possible reinvasion from neighboring sites and trap avoidance for the sake of sustainability of control campaigns effects. Unlabelled Image • In Côte d'Ivoire HAT foci, Glossina palpalis palpalis show relatively important effective population size and modest dispersal before control. • Genetic data analyses show that flies captured after control partly (at least) come from surrounding sites. • One allele at Locus GPCAG displayed a 328% allele frequency increase after control. • This locus (GPCAG) seems associated to resistance to control, by a mechanism which remains to be identified. [ABSTRACT FROM AUTHOR]

A raster or grid-based Geographic Information System with data on tsetse, trypanosomiasis, animal production, agriculture and land use has recently been developed in Togo. The area-wide sampling of tsetse fly, aided by satellite imagery, is the subject of two separate papers. This paper follows on a first paper, published in this journal, describing the generation of digital tsetse distribution and abundance maps and how these accord with the local climatic and agro-ecological setting. Such maps when combined with data on the disease, the hosts and their owners, should contribute to the knowledge of the spatial epidemiology of trypanosomiasis and assist planning of integrated control operations. Here we address the problem of generating tsetse distribution and abundance maps from remotely sensed data, using a restricted amount of field data. Different discriminant analysis models have been applied using contemporary tsetse data and remotely sensed, low resolution data acquired from the National Oceanographic and Atmospheric Administration (NOAA) and Meteosat platforms. The results confirm the potential of satellite data application and multivariate analysis for the prediction of the tsetse distribution and abundance. This opens up new avenues because satellite predictions and field data may be combined to strengthen and/or substitute one another. The analysis shows how the strategic incorporation of satellite imagery may minimize field collection of data. Field surveys may be modified and conducted in two stages, first concentrating on the expected fly distribution limits and thereafter on fly abundance. The study also shows that when applying satellite data, care should be taken in selecting the optimal number of predictor variables because this number varies with the amount of training data for predicting abundance and on the homogeneity of the distribution limits for predicting fly presence. Finally, it is suggested that in addition to the use of contemporary training data and predictor variables, training and predicted data sets should refer to the same eco-geographic zone.

The purpose of this study was to classify the risk for transmission of African human trypanosomiasis (sleeping sickness) according to population and settlement densities in four different areas of Zoukougbeu, Cote d'Ivoire, where the exact location of cases reported since 1990 is known. Epidemiological risk indexes were calculated from entomological data obtained from three surveys and analyzed with respect to presence of patients and occupancy rate in each area. Results indicated that there was a risk of transmission near the village of Bahigbeu II where the population density is between 30 and 40 inhabitants per km2 and settlement density is 4 per km2. There was also a risk in less inhabited areas such as Ouatigbeu where the population density is less than 30 inhabitants per km2 and dwelling density less than 4 per km2. In fact, cases are regularly reported in Ouatigbeu but never in Bahigbeu II. Based on these findings, we conclude that, while land occupancy can be considered as a risk factor for sleeping sickness, other factors such as human mobility must be taken into account to characterize risk areas and predict outbreaks.

The epidemiological risk of human African trypanosomiasis transmission was evaluated from entomological parameters (apparent trap density, female teneral rates, daily survival rates, proportion of human feeds) of tsetse (Glossina palpalis palpalis) populations in the town of Daloa, Côte d'Ivoire. High tsetse densities were found in the town outskirts, where the calculated risk of transmission was greatest. Environmental changes brought about by urbanization did not result in the disappearance of tsetse, or the interruption of sleeping sickness transmission. The few cases of sleeping sickness detected (32) in the years 1990-95 indicated that transmission was unrelated to tsetse density.

Collections of Glossina with a biconical trap have been made for 6 years in the forest area of Daloa in Côte d'Ivoire. Three species of Glossina have been identified in the village of Batéguédéa II as well as in the plantations and gallery forests. They are: G. palpalis, G. pallicera and G. nigrofusca. G. palpalis was predominant in the village in 1984, representing 74% of the collection, while the G. pallicera and G. nigrofusca types are more common in plantations and gallery forest. In 1987, 3 years after the first observation, G. palpalis was the most common species in each of the three biotopes. G. palpalis was even more common in 1990, following a decline in the population of G. pallicera and G. nigrofusca in the village (0.2% for G. pallicera; 0.8% for G. nigrofusca) and the plantations (0.7% for G. pallicera; 1.3% for G. nigrofusca). However, these two species were still found in small numbers in the gallery forest.

As part of a study on livestock productivity under trypanosomosis risk in the region of Boundiali, northern Côte d'Ivoire, 21 herds of cattle (N'Dama, Baoulé and Zebu crosses) and 20 flocks of Djallonké and Djallonké x Sahel sheep were monitored monthly for body weight, packed red cell volume and trypanosomal parasitaemia over various periods between January 1984 and December 1992. A tsetse control campaign using biconical traps impregnated with alpha-cypermethrin started in December 1987. Tsetse control reduced the relative tsetse density by over 95% between 1988 and 1992, and this was associated with reductions in the prevalence of Trypanosoma congolense over the same period of over 90% both in sheep and cattle. Average reductions in the prevalence of T. vivax were lower, on average 68% in adults and 85% in young animals. Attempts were made in the design of the study to allow comparisons between controlled and uncontrolled areas; however, there were too many confounding and uncontrollable factors to allow such comparisons to be made. It was necessary, therefore, to compare data collected from all herds and flocks before and after the intervention, with the consequential difficulties in accounting for uncontrollable year-to-year variations in factors affecting trypanosome prevalence in livestock.

An index of epidemiological risk was developed for the foci of human African trypanosomiasis (HAT) in the forest zone of Côte d'Ivoire, based on the following characteristics of Glossina palpalis palpalis populations: daily survival rate, apparent density of teneral males and females, and frequency of human-fly contact. The index agreed well with HAT prevalence. It varied according to ethnic groups and with seasonal changes in agricultural activities and fell rapidly to zero following the start of an anti-vector control campaign. Further studies in different biogeographical zones are desirable in order to substantiate the validity of the index.

This paper gives the results of a tsetse fly research program in the preforested area of Ivory Coast. The main investigation tool was the Challier-Laveissière's biconical trap. The ecodistribution, resting and pupal sites of the principal tsetse species, G. palpalis, G. pallicera and G. nigrofusca were described in the T. b. gambiense sleeping sickness focus of Vavoua. Population dynamics, host preferences, activity cycles were compared between tsetse populations in plantations and village surroundings. Man-fly contact was of high intensity where human habitat is scattered in plantations but in village tsetse flies used to feed mainly on pigs. Resettlement of scattered populations can be considered as a preventive measure against sleeping sickness transmission. Experiments on tsetse flies control by insecticides along edges, associated with insecticidal impregnated screens, were considered as promising.

After preliminary studies on the ecodistribution of Glossina palpalis s.l. in the sleeping sickness focus of Vavoua (Ivory Coast) trials with screens impregnated with decamethrine were carried out. Artificial supports for insecticide present several advantages: less pollution, less costly, simplicity, facility of use by local personnel, possibility of re-use, integration with other methods. On the other hand, its action based on the attraction of flies which come into contact with the screen is relatively slow, particularly in obtaining a complete interruption of reproduction. The technique is compared with other control methods as the use of biconical traps and selective spraying along borders. Its action can be improved by the addition of attractive host odours or sex pheromones.

Recent estimates of the costs of detection and treatment and vector control for human trypanosomiasis are summarized and the main factors influencing their levels discussed. In order to proceed to an economic analysis a benefit unit is defined as equivalent to one year's infection avoided due to the control strategy for one person. Different monetary values could be assigned to this unit and it has the advantage of being easily integrated into epidemiological models, being represented by the difference in prevalence with and without control. A simple spreadsheet-based economic model was developed to analyse the relative economic performance of the two control strategies in terms of the cost per benefit unit obtained. The results demonstrate the sensitivity of the economic performance of each strategy to the epidemiological assumptions made, especially with respect to the existence of an animal reservoir and the evolution of the disease situation in the absence of control. They point to the need to integrate economic and epidemiological models in order to evaluate control options.

Tsetse control trials were carried out in forest zone of Côte d'Ivoire with biconical traps. Some of the traps were impregnated with deltamethrin (1, 2 g per trap) and others were not. Results show a rapid and effective action of the treated supports. In nine days, the tsetse population had been reduced by 85% on the treated supports and by 60% on the non treated supports. After one month, a rapid decrease of the efficacy of the treated traps was observed. The fall in the effectiveness (more masked in the treated traps) was certainly due to heavy rains (875 mm) which caused an important increase in growth of vegetation.

A review of literature of the previous and recent evidence of potential animal reservoir hosts of gambiense sleeping sickness is given. A highly endemic sleeping sickness area in the Ivory Coast is described together with an area of recent low endemicity in southwestern Upper Volta. These areas were surveyed as part of a study on the significance of any potential animal reservoir of the disease. The results are described in detail in subsequent papers.

The entomo-epidemiological studies carried out from 1980 to 1985 in the human trypanosomiasis focus at Bouaflé (Ivory Coast) were designed to estimate the main epidemiological parameters related to G. palpalis palpalis, the sleeping sickness vector in the zone considered. This paper defines the mathematical relationships which can exist between these parameters leading to the production of a simple model enabling estimates to be made of the incidence of human trypanosomiasis caused by T.b. gambiense in this focus. The model predicted a mean annual incidence of 1.50% in the Bouaflé focus. In the zones with high pig densities which were characterised by high densities of tsetse flies with weak anthropophily, the model predicted an incidence of 1.22%. However, a disease incidence of 1.76% was estimated for zones where domestic pigs were absent or at low density and characterised by low densities of tsetse flies with strong anthropophily. The author also emphasizes the relationships between mathematical models and realities in the field and the usefulness of these models to the field worker in planning control campaigns.