The main bugs are belonging to the Order Heteroptera, Family Cimicidae and Genus Cimex. They are hematophagous insects that have been living next to humans for thousands of years. They prick their host in his sleep with night-time manners and lucifuges (National Centre of Expertise on Vectors NCEV, 2015). The term bed bug refers  to  two globally known  species  for  their nuisance. They are: Cimex lectularius Linnaeus, 1758 and Cimex hemipterus Fabricius, 1803. In countries of Asia, America and Europe, these insects are a real public health problem. They are responsible for a numerous dermatological and allergic disorders they cause, ranging from a simple bite to generalized manifestations which can be linked to  an  urticaria. In  addition,  infestations  of entire buildings (collective dwellings, hotels, retirement homes, hospitals, etc.) have been reported in these countries (Delaunay et al., 2015). Fortunately, bed bugs do not yet present a risk of transmission of infectious agents. However, the degree of nuisance is such that many countries (France, Belgium, the United States, etc.) have made the control of these insects a priority. In Côte d'Ivoire, the bed bugs were repeatedly reported in the service reports of the National Institute of Public Hygiene (NIPH); but were never formally identified. In urban areas, particularly in Abidjan, recurring complaints due to the activity of these bed bugs were reported by the Vector Control Service (VCS) of the NIPH. The nuisance they cause is of increasing concern, including the distribution of infestations, the conditions of mattress infestations and the extent of infestations. However, finding solutions to these concerns will necessarily involve identifying the agents responsible for these infestations. Knowledge about the biology and ecology of bed bugs is unfortunately almost non-existent in Côte d'Ivoire.

The purpose of this preliminary study was to identify the species of bed bugs that were implicated in the reported home infestations, with a view to establishing the first tools for finding a suitable control.

Study area overview

This study was conducted in several cities of Côte d'Ivoire; country located in West Africa, in the intertropical wet zone of the earth, between the Tropic of Cancer and the Equator. Four study cities in the south of the country (Abidjan, Grand Bassam, Anyama and Agboville) and three collection sites in the center (Yamoussoukro and Bouaké) and in the west (Guiglo) served to collect the “bedbug” specimens studied (Figure 1).

Entomological surveys: capture of bed bugs

This was a cross-sectional survey that ran from August 2016 to February 2019.

Thus, in practice, the collection sites were visited only once, following a distress call indicating the probable presence of these insects. The sites visited were very diverse, including private homes, businesses, bus stations, hotels, places of worship, markets and hospitals. The method of collection consisted of searching during the day and by direct observation for signs of the presence of the bed bugs: eggs hatched or not, nymphs and brown molt skins, traces of blood on the sheets and excrement left. All places likely to harbor these insects, mainly mattresses, used clothing, used furniture and cracks in the wall, were carefully inspected. When these signs were visible, aerosol cans were used to flush out the bugs. After a few minutes of waiting, the dead or living insects were taken out of the hiding places and collected using an entomological clamp and kept in pill boxes containing 70% alcohol. Each pill box was labelled by sampling location and collection date. At the NIPH laboratory, the collected individuals were subjected to classical diagnostic techniques using binocular magnifying glass and dichotomous keys from Masini et al. (2019) and Benkacimi et al. (2020).

Data exploitation and analysis

Data was captured and organized from Microsoft Office Excel 2013. This spread sheet was used to calculate numbers and proportions of species observed. Fisher’s nonparametric test was performed using the statistical software SPSS version 25. It was used to compare the proportions of different species caught at collection sites. The significance threshold was set at 5% (p<0.05).

Following diagnosis, two species of bed bugs were identified (Figure 2a and b). These are C. hemipterus and C. lectularius. They were collected from all collection sites (Table 1). C. hemipterus and C. lectularius are very close morphologically, however, only the shape of the pronotum or medici neck can differentiate them.

A total of 1,114 bed bugs were sampled across even cities. Of the two species identified, C. hemipterus was the most frequent at the reported infestations, with 77.9% (n=868) and 22.1% (n=246) for C. lectularius (Table 2). Fisher’s test on the proportions of the two species revealed a highly significant difference (p<0.001) across all the cities investigated. In addition, C. hemipterus was the best represented species in each city. The proportions of this species recorded in Abidjan, Grand Bassam, Anyama, Agboville, Yamoussoukro, Bouaké and Guiglo were 77.1% (n=475), 78.1% (n=89), 71.7% (n=43), 75% (n=27), 83.9% (n=73), 77.3% (n=102) and 85.5% (n=59), respectively. A total of 46 harvests were conducted during this cross-sectional study (Table 2).

The bed bugs of the Family Cimicidae are very invasive hematophagous insects. Their geographical distribution has undergone major changes in connection with the globalization of trade, the movement of travellers and the anarchic urbanization of large cities. Of all the species of Cimicidae, C. hemipterus and C. lectularius are known worldwide for the nuisance they cause in human populations (Delaunay et al., 2011; Masini et al., 2019; Benkacimi et al., 2020).

C. hemipterus and C. lectularius, although present in Côte d'Ivoire, are very little known to scientists and the public. This is due to the lack of sufficient information on their bio-ecology but also because they are not vectors of pathogens to humans and animals. Although not vectors, laboratory studies revealed that these species host several infectious agents; these include bacteria (Bacillus anthracis, Mycobacterium leprae, Mycobacterium tuberculosis), parasites (Trypanosoma cruzi, Wuchereria bancrofti) and mushrooms (Aspergillus flavus) (Burton, 1963). However, the presence of C. hemipterus and C. lectularius in European, American and Asian continents, are a source of major concern (Balvín et al., 2014; Jourdain    et    al.,   2016).   The   considerable   financial resources allocated to vector control programmes, the innovation tools (heat treatment devices) and the new methods of control are all examples of the situation prevailing in some countries on these continents. The economic impact of infestations is very important but difficult to quantify for individuals, the hotel industry and the tourism sector (Davies et al., 2012; NCEV, 2015). Indeed, individuals must face the high cost of pest control, replacement of infested furniture, bedding and clothing. For the hotel industry, the costs are much higher due to the unoccupied rooms of the contaminated rooms. This may have repercussions on the tourism sector. This is a huge shortfall for these countries (Davies et al., 2012).

In this study, the importance of the collection cities (Abidjan, Grand Bassam, Anyama, Agboville, Yamoussoukro, Bouaké and Guiglo) gives an overview of the geographical distribution of the bed bugs present in Côte d'Ivoire and, on the other hand, reflects a worrying health situation. C. hemipterus and C. lectularius being highly invasive cosmopolitan species, their expansion could be caused by two types of displacement: active and passive. Active displacement is used to search for a blood meal as soon as individuals are present in the locality or in the infested sites. The second mode of movement requires the action of humans. Fortuitously, they transport the insects to new places located several kilometers away; when traveling, moving, bringing old furniture, books or second-hand items previously infested into one's home (Anastay et al., 2011; Delaunay et al., 2015). The latter is believed to be the main cause of the reported infestations.

C. hemipterus and C. lectularius are very close morphologically, however, only the shape of the pronotum or medici neck can differentiate them (Masini et al., 2019; Benkacimi et al., 2020). In this study, C. hemipterus (77.9%) was the most prevalent in the reported infestations. This reflects the ecological belonging of this species to the Ivorian territory, therefore to the tropical zone. Furthermore, it’s dispersal is currently spreading beyond tropical borders due to the globalization of trade, travel, and the anarchic urbanization of major metropolises. There also is a modification  of  C. lectularius  geographical  area.  Once restricted to temperate regions, this species has adapted to new territories in Africa (Federica et al., 2013; Zorrilla-Vaca et al., 2015). This is very well illustrated by its small proportion (22.1%) obtained during the various entomological surveys.

To date, there is no single method of struggle in the world that can overcome or eliminate bed bugs. Most vector control programs face enormous challenges, including population adherence, resistance to insecticides and resurgence of infestation sites (Davies et al., 2012; Morand, 2014).

Control of these insects is rarely achieved through a single approach. Only an integrated approach would be realistic. The collaboration between occupants, owners and pest controllers is therefore essential for an effective and parsimonious fight. Also, further investigation of sites of pest predilection and transfer of pests from one site to another could contribute to a more efficient and reasoned management.

This study identified two species of bed bugs: C. lectularius and C. hemipterus; with a relatively high population for the latter. In addition, the importance of C. hemepterus in relation to C. lectularius means that they are both present in all the cities visited. This situation indicates that they are present in the south, the center and the west of the country. In view of this distribution, it seems urgent to point out the importance that these species of bed bugs could represent if nothing is done to control them.

The authors have not declared any conflict of interests.

The data for this study were obtained from routine activities carried out by the vector control department of the National Institute of Public Hygiene.