Tick species infesting cattle in the central region of Burkina Faso: Presence of Rhipicephalus microplus less than ten years after its first identification in the Southwest part of the country.

Ticks are among the most important vectors for medical and veterinary importance in African countries, representing thus an obstacle for development and improvement of livestock production. The central part of Burkina Faso is an arid region which has a low diversity of tick species and in which Rhipicephalus microplus has been absent. This study aimed to examine ticks infesting cattle within this region, focusing on the peripheral area of Ouagadougou. Tick sampling was undertaken monthly on 30 selected cattle in the state breeding station of Loumbila, from June 2017 to February 2018. Morphological identification was carried out based on previous established keys and catalogue. A total of 1,076 ticks belonging to four genera and seven species were collected. Amblyomma variegatum (50.5%) was the most abundant species followed by Hyalomma rufipes (27.4%), Hyalomma truncatum (13.7%), Rhipicephalus decoloratus (4.5%), Hyalomma impressum (2.4%), Rhipicephalus microplus (1.5%), and Rhipicephalus sanguineus sensu lato (0.1%). The results suggested a decrease of A. variegatum and Hyalomma spp. load compared to data collected in 1996 from the same study area. Presence of R. microplus and R. decoloratus has been highlighted in the studied area for the first time. This finding highlights the relevance of regular investigations on tick species infesting livestock utilizing collaboration with different stakeholders.

Modelling habitat suitability of the invasive tick Rhipicephalus microplus in West Africa.

Ticks have medical and economic importance due to their ability to transmit pathogens to humans and animals. In tropical and sub-tropical countries, tick-borne diseases (TBD) are among the most important diseases affecting livestock and humans. The fast spread of ticks and TBD requires a quick development and application of efficient prevention and/or control programs. Therefore, prior investigations on TBD and related vectors epidemiology, for instance, through accurate epidemiological models, are mandatory. This study aims to develop models to forecast suitable habitat for Rhipicephalus microplus distribution in West Africa. Tick occurrences were assembled from 10 different studies carried out in six West African countries in the past decade. Six statistical models (maximum entropy in a single model and generalised linear model, generalised additive model, random forest, boosted regression tree and support vector machine model in an ensemble model) were applied and compared to predict the habitat suitability of R. microplus distribution in West Africa. Each model was evaluated with the area under the receiver operating characteristic curve (AUC), the true skill statistic (TSS) and the Boyce index (BI). The selected models had good performance according to their AUC (above .8), TSS (above .7) and BI (above .8). Temperature played a key role in MaxEnt model, whereas normalised difference vegetation index (NDVI) was the most important variable in the ensemble model. The model predictions showed coastal countries of West Africa as more suitable for R. microplus. However, some Sahelian areas seems also favourable. We stress the importance of vector surveillance and control in countries that have not yet detected R. microplus but are in the areas predicted to host suitable habitat. Indeed, awareness-raising and training of different stakeholders must be reinforced for better prevention and control of this tick in these different countries according to their status.

Models for Studying the Distribution of Ticks and Tick-Borne Diseases in Animals: A Systematic Review and a Meta-Analysis with a Focus on Africa.

Ticks and tick-borne diseases (TTBD) are constraints to the development of livestock and induce potential human health problems. The worldwide distribution of ticks is not homogenous. Some places are ecologically suitable for ticks but they are not introduced in these areas yet. The absence or low density of hosts is a factor affecting the dissemination of the parasite. To understand the process of introduction and spread of TTBD in different areas, and forecast their presence, scientists developed different models (e.g., predictive models and explicative models). This study aimed to identify models developed by researchers to analyze the TTBD distribution and to assess the performance of these various models with a meta-analysis. A literature search was implemented with PRISMA protocol in two online databases (Scopus and PubMed). The selected articles were classified according to country, type of models and the objective of the modeling. Sensitivity, specificity and accuracy available data of these models were used to evaluate their performance using a meta-analysis. One hundred studies were identified in which seven tick genera were modeled, with Ixodes the most frequently modeled. Additionally, 13 genera of tick-borne pathogens were also modeled, with Borrelia the most frequently modeled. Twenty-three different models were identified and the most frequently used are the generalized linear model representing 26.67% and the maximum entropy model representing 24.17%. A focus on TTBD modeling in Africa showed that, respectively, genus Rhipicephalus and Theileria parva were the most modeled. A meta-analysis on the quality of 20 models revealed that maximum entropy, linear discriminant analysis, and the ecological niche factor analysis models had, respectively, the highest sensitivity, specificity, and area under the curve effect size among all the selected models. Modeling TTBD is highly relevant for predicting their distribution and preventing their adverse effect on animal and human health and the economy. Related results of such analyses are useful to build prevention and/or control programs by veterinary and public health authorities.

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 ineffectiveness, 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 different 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 ineffectiveness in tick populations control remains a concern in BF.

Cross border transhumance involvement in ticks and tick-borne pathogens dissemination and first evidence of Anaplasma centrale in Burkina Faso.

In West Africa, cross-border transhumance, also called seasonal migration, is known to be a very important animal production strategy, as it involves about 70 to 90% of cattle. In spite of the cattle movements, some strategic areas of transhumance remain poorly explored regarding ticks and their associated pathogens investigations. The purpose of this study is to evaluate the involvement of transhumance in the spread of cattle ticks and associated pathogens in Burkina Faso (BF) and Benin (BN), in a context of speedy invasion of West African livestock by Rhipicephalus microplus. A longitudinal survey was performed on 210 cattle from BF, monitored for ticks and tick-borne pathogens (TBP) during one seasonal transhumance. The first sampling coded "T0BF" took place in eastern BF, at the transhumance departure. A second sampling "T1BN" was carried out in northern BN, the transhumance arrival zone. A third sampling "T2BF" was done at the return of cattle in eastern BF. Ticks were morphologically identified and TBP detected with reverse line blot hybridization (RLB) assay. A total of 1027 ticks (7 species), 1006 ticks (11 species) and 1211 ticks (9 species) were respectively found at T0BF, T1BN and T2BF. Some species were collected at the three times of sampling without any significant difference in their relative abundances. However, other tick species appeared only at T1BN and/or T2BF. The TBP species found at the three points surveyed were Theileria annulata, Theileria mutans, Theileria velifera, Babesia bigemina and Anaplasma marginale. The most prevalent was T. mutans with 166/210 (79%), 159/210 (75.7%) and 78/210 (37%) cattle positive respectively at T0BF, T1BN and T2BF. Anaplasma centrale was evidenced with 0.5% and 0.9% respectively at T0BF and T2BF. To our knowledge, this represents its first report in the study area. Overall, the TBP prevalences were significantly lower at T2BF, highlighting the effect of tick populations changes induced by transhumance combined with the seasonal variation influence.

Cattle ticks and associated tick-borne pathogens in Burkina Faso and Benin: Apparent northern spread of Rhipicephalus microplus in Benin and first evidence of Theileria velifera and Theileria annulata.

Babesiosis, theileriosis, anaplasmosis, and heartwater are tick-borne diseases that threaten livestock production in sub-Saharan Africa including Burkina Faso and Benin. For over a decade, these two bordering countries have been facing an invasion of the livestock by the tick Rhipicephalus microplus, a major vector for babesiosis, accidentally introduced in Benin in 2004. The molecular identification of tick-borne pathogens in this border area is of particular interest due to animals seasonal migration between the two countries. In this survey, epidemiological features of ticks and tick-borne pathogens in cattle were investigated to compare the eastern Burkina Faso, corresponding to a seasonal migration departure zone, and the northern Benin, which represents a seasonal migration arrival zone. Ticks and peripheral blood were collected from a total of 946 cattle in the two areas. Ticks were morphologically identified and the DNA samples from bovine blood and ticks were analysed by Reverse Line Blot (RLB) hybridization process. A total of 2856 ticks were collected on 490 cattle in Burkina Faso, eight tick species were identified, while 3583 ticks were collected on 456 cattle in North Benin with nine tick species identified. The invasive tick, R. microplus was not found in eastern Burkina Faso, but its spread farthest north in Benin is reported. Six tick-borne pathogen species were found in cattle blood both in eastern Burkina Faso and in northern Benin. Ranked in decreasing order of overall prevalences, they are: Theileria mutans (91.1%), Theileria velifera (77.8%), Babesia bigemina (10.9%), Anaplasma marginale (4.2%), Babesia bovis (3.3%), and Theileria annulata (1.8%). To the best of our knowledge, this survey represents the first report of T. velifera and T. annulata in the region. Overall, the TBP prevalences were significantly higher in northern Benin than in eastern Burkina Faso, indicating a higher parasitological risk in this area.

First tick and tick damage perception survey among sedentary and transhumant pastoralists in Burkina Faso and Benin.

BACKGROUND: Transhumance, a main ancestral animal production strategy of the West African Countries (WAC), can favour the spread of vectors and vector-borne diseases within and/or across countries. Transhumance has been implicated in such spread as well as that of related tick-borne diseases (TBD). METHODS AND PRINCIPAL FINDINGS: Using a questionnaire survey and statistical modelling, this study explores the perception of herders about ticks and TBD in cattle, their practices in tick control and the social groups involved in cattle farming in eastern Burkina Faso (46 random herds) and in the northern Benin (44 random herds). Results show that most of the herders (79%) are from the Fulani social group. The principal and secondary activities of herders are respectively cattle farming and agriculture. The mean age of pastoralists is between 40 and 50 years depending on the province of origin and 60% of the surveyed herds practice internal or transboundary transhumance. Herders have a clear knowledge of different genus of ticks except the genus Rhipicephalus. Their knowledge of TBD is very limited. These results also reveal that herders in Benin use less acaricides treatment calendar compared with those in Burkina Faso. Transhumant pastoralists (i.e. transhumant cattle farmers) plan more acaricide treatment and have more cows with lost teats (i.e. tick damage) than the sedentary ones. In addition, amitraz appears to be the main acaricide compound used by herders for tick control (68%) but its use is inappropriate and its source is frequently the unregulated market. CONCLUSIONS AND SIGNIFICANCE: All of these findings can induce acaricide resistance especially as the inefficacy of amitraz against Rhipicephalus (Boophilus) microplus has already been reported in previous studies. Such results would help to elaborate suitable strategies of control and prevention of ticks and TBD in Burkina Faso and Benin.

First digital characterization of the transhumance corridors through Benin used by cattle herds from Burkina Faso and associated risk scoring regarding the invasion of Rhipicephalus (Boophilus) microplus.

BACKGROUND: Livestock plays a key role in the macro-economy of West Africa and provides livelihoods for millions of people. The main cattle rearing strategy in West Africa is pastoralism, including transhumance, that is a seasonal migration of cattle with their herders. This adaptive strategy aims to optimize livestock access to water and pastures. However, it can favour pathogens and vectors transboundary spread. The aim of this study was to highlight firstly, the corridors and grazing areas used by Burkina Faso transhumant cattle herds going to Benin; secondly, the characteristics of departure and arrival areas of transhumance; and thirdly, the risk score related to introduction and spread of the invasive tick species, Rhipicephalus (Boophilus) microplus, in free areas. METHODS AND PRINCIPAL FINDINGS: Therefore, GPS devices were given to 27 herders to monitor a full transhumance season between East Burkina Faso and North Benin. The analysis of 14,966 spots generated by the GPS devices revealed four main corridors and five main grazing areas used by cattle herds during transhumance. Statistical analysis of normalized difference vegetation index (NDVI), rainfall and temperature data, highlighted significant differences between departure and arrival areas. NDVI and rainfall are significantly higher in Benin than Burkina Faso, whereas temperature is significantly lower. Additionally, using biotic and abiotic parameters, a risk scoring was developed to predict the presence of Rhipicephalus (Boophilus) microplus at municipality level. CONCLUSIONS AND SIGNIFICANCE: The better vegetation, temperature and rainfall conditions during the dry seasons in Benin attract cattle herds from Burkina Faso. The invasiveness and adaptability of Rhipicephalus (Boophilus) microplus added to the frequent stays of transhumant herds in infested areas suggest its potential introduction and establishment in free areas soon. Moreover, frequent intrusions of the transhumant cattle in the wildlife reserves are another risk of vectors and pathogen exchange between domestic and wild animals.