Efficacy of two commercial synthetic pyrethroids (cypermethrin and deltamethrin) on Amblyomma variegatum and Rhipicephalus microplus strains of the south-western region of Burkina Faso

Since 2011, period of the livestock invasion by the cattle tick Rhipicephalus microplus in Burkina Faso (BF), tick-control problems were exacerbated. Based on farmer’s reports, most commonly used commercial acaricides were found to be ineffective in Western South part of the country. To investigate the occurrence and extent of such acaricidal inefectiveness, we performed the standardized larval packet test (LPT) with commercial deltamethrin (vectocid) and cypermethrin (cypertop), on two cattle tick species, the native Amblyomma variegatum and the invasive R. microplus. The resistance ratios (RR) were computed with susceptible Hounde strain of Rhipicephalus geigyi as reference. The R. microplus population showed resistance to the two acaricides tested with the highest lethal concentration (LC) values, and diferent resistance ratios higher than 4 (deltamethrin: RR50=28.18 and RR90=32.41; cypermethrin: RR50=8.79 and RR90=23.15). In the contrary, A. variegatum population was found to be highly susceptible to acaricides tested with low lethal concentrations and resistance ratio values (deltamethrin: RR50=0.5 and RR90=0.48; cypermethrin: RR50=0.68 and RR90=0.79). These data demonstrate high synthetic pyrethroid resistance in R. microplus strain, leading to conclude that the acaricide inefectiveness in tick populations control remains a concern in BF.http://link.springer.com/journal/11250pm2022Veterinary Tropical Disease

Restricted Application of Insecticides: A Promising Tsetse Control Technique, but What Do the Farmers Think of It?

Restricted application of insecticides to cattle is a cheap and safe farmer-based method to control tsetse and the diseases they transmit, i.e. human and animal African trypanosomoses. The efficiency of this new control method has been demonstrated earlier but no data is available on its perception and adoption intensity by farmers. We studied these two features in Burkina Faso, where the method has diffused thanks to two development projects. The study allowed identifying three groups of farmers with various adoption intensities, of which one was modern and two traditional. The economic benefit and the farmers' knowledge of the epidemiological system appeared to have a low impact on the early adoption process whereas some modern practices, as well as social factors appeared critical. The quality of technical support provided to the farmers had also a great influence on the adoption rate. The study highlighted individual variations in risk perceptions and benefits, as well as the prominent role of the socio-technical network of cattle farmers. The results of the study are discussed to highlight the factors that should be taken into consideration, to move discoveries from bench to field for an improved control of trypanosomoses vectors

Prevalence of Trypanosoma and Sodalis in wild populations of tsetse flies and their impact on sterile insect technique programmes for tsetse eradication

The sterile insect technique (SIT) is an environment friendly and sustainable method to manage insect pests of economic importance through successive releases of sterile irradiated males of the targeted species to a defined area. A mating of a sterile male with a virgin wild female will result in no offspring, and ultimately lead to the suppression or eradication of the targeted population. Tsetse flies, vectors of African Trypanosoma, have a highly regulated and defined microbial fauna composed of three bacterial symbionts that may have a role to play in the establishment of Trypanosoma infections in the flies and hence, may influence the vectorial competence of the released sterile males. Sodalis bacteria seem to interact with Trypanosoma infection in tsetse flies. Field-caught tsetse flies of ten different taxa and from 15 countries were screened using PCR to detect the presence of Sodalis and Trypanosoma species and analyse their interaction. The results indicate that the prevalence of Sodalis and Trypanosoma varied with country and tsetse species. Trypanosome prevalence was higher in east, central and southern African countries than in west African countries. Tsetse fly infection rates with Trypanosoma vivax and T. brucei sspp were higher in west African countries, whereas tsetse infection with T. congolense and T. simiae, T. simiae (tsavo) and T. godfreyi were higher in east, central and south African countries. Sodalis prevalence was high in Glossina morsitans morsitans and G. pallidipes but absent in G. tachinoides. Double and triple infections with Trypanosoma taxa and coinfection of Sodalis and Trypanosoma were rarely observed but it occurs in some taxa and locations. A significant Chi square value (< 0.05) seems to suggest that Sodalis and Trypanosoma infection correlate in G. palpalis gambiensis, G. pallidipes and G. medicorum. Trypanosoma infection seemed significantly associated with an increased density of Sodalis in wild G. m. morsitans and G. pallidipes flies, however, there was no significant impact of Sodalis infection on trypanosome density.The Joint FAO/IAEA Insect Pest Control Subprogramme.https://www.nature.com/srepVeterinary Tropical Disease

Climate, cattle rearing systems and African Animal Trypanosomosis risk in Burkina Faso.

BACKGROUND: In sub-Saharan countries infested by tsetse flies, African Animal Trypanosomosis (AAT) is considered as the main pathological constraint to cattle breeding. Africa has known a strong climatic change and its population was multiplied by four during the last half-century. The aim of this study was to characterize the impact of production practices and climate on tsetse occurrence and abundance, and the associated prevalence of AAT in Burkina Faso. METHODOLOGY/PRINCIPAL FINDINGS: Four sites were selected along a South-north transect of increasing aridity. The study combines parasitological and entomological surveys. For the parasitological aspect, blood samples were collected from 1,041 cattle selected through a stratified sampling procedure including location and livestock management system (long transhumance, short transhumance, sedentary). Parasitological and serological prevalence specific to livestock management systems show a gradual increase from the Sahelian to the Sudano-Guinean area (P<0.05). Livestock management system had also a significant impact on parasitological prevalence (P<0.05). Tsetse diversity, apparent densities and their infection rates overall decreased with aridity, from four species, an apparent density of 53.1 flies/trap/day and an infection rate of 13.7% to an absence at the northern edge of the transect, where the density and diversity of other biting flies were on the contrary highest (p<0.001). CONCLUSIONS/SIGNIFICANCE: The climatic pressure clearly had a negative impact on tsetse abundance and AAT risk. However, the persistency of tsetse habitats along the Mouhoun river loop maintains a high risk of cyclical transmission of T. vivax. Moreover, an "epidemic mechanical livestock trypanosomosis" cycle is likely to occur in the northern site, where trypanosomes are brought in by cattle transhuming from the tsetse infested area and are locally transmitted by mechanical vectors. In Burkina Faso, the impact of tsetse thus extends to a buffer area around their distribution belt, corresponding to the herd transhumance radius

Distribution of biting flies along the climatic gradient in Burkina Faso.

<p>Sites are ordered by increasing annual rainfall from the left to the right. Boxplots present the median (bold line), quartiles (boxes), 95% confidence intervals (horizontal lines) and erratic values (dots).</p

Tsetse infection rates along the aridity gradient.

<p>Sites are ordered by increasing annual rainfall from the left to the right.</p

Parasitological and serological prevalences by trypanosome species according to cattle rearing systems and sites.

<p>Sites are ordered by increasing annual rainfall from the left to the right.</p><p><b>CRS:</b> Cattle rearing system; <b>St:</b> Short transhumance; <b>Lt:</b> Long transhumance; <b>Sed</b>: sedentary;</p>*<p>long transhumance not identified in this site;</p>**<p>short transhumance not identified in this site;</p><p><b><i>Tv</i></b>: <i>Trypanosoma vivax</i>; <b><i>Tc</i></b><i>: T. congolence</i>; <b><i>Tbb</i></b><i>: T. brucei brucei</i>; <b><i>T.spp</i></b>: all trypanosome species together.</p

Distribution of sampled animals in sites according to cattle rearing systems.

<p>Sites are ordered by increasing annual rainfall from the left to the right.</p><p>- Non identified cattle rearing system.</p

Apparent densities of mechanical vectors along the climatic gradient.

<p>Sites are ordered by increasing annual rainfall from the left to the right.</p