Trials of olfactory attractants to enhance trap catches of Glossina fuscipes fuscipes (Diptera: Glossinidae) in the Jp Gouteux, F Blanc, D Cuisance, Frank d’Amico, A Kota Guinza

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Jp Gouteux, F Blanc, D Cuisance, Frank d’Amico, A Kota Guinza. Trials of olfactory attractants to enhance trap catches of Glossina fuscipes fuscipes (Diptera: Glossinidae) in the Central African Republic. Veterinary Research, BioMed Central, 1995, 26 (4), pp.335-340. ￿hal-00902357￿

HAL Id: hal-00902357 https://hal.archives-ouvertes.fr/hal-00902357 Submitted on 1 Jan 1995

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Trials of olfactory attractants to enhance trap catches of Glossina fuscipes fuscipes (Diptera: Glossinidae) in the Central African Republic

JP Gouteux F Blanc D Cuisance F D’Amico A Kota Guinza

1 ORSTOM, département de mathématiques appliquées, URA-CNRS 1204, IPRA-UPPA, avenue de l’Université, 64000 Pau, France; 2 Agence nationale de développement de l’élevage, ANDElFNEC, BP 1509, Bangui, Central African Republic; 3 CIRAD-EMVT, slc ORSTOM, BP 5045, 34032 Montpellier cedex 1, France

(Received 19 January 1995; accepted 2 May 1995)

Summary ― Host odours increased the trap catches of Glossina fuscipes fuscipes in breeding areas of the Central African Republic. The increase was significant with zebu urine (x 1.4) and the prin- cipal reptilian host, the monitor lizard (x 1.7). The greatest effect (x 4.2) was obtained for male G f fuscipes with zebu urine when the densities of were low (less than 5 males per trap per day). It seems that olfactory baits in urine could improve the control of G f fuscipes by trapping. Reptile odour contains attractants that should be identified.

Glossina fuscipes fuscipes / tsetse flies / trapping / host odours I reptile / zebu

Résumé ― Essais d’attractifs olfactifs (odeurs d’hôtes) pour améliorer la lutte par piégeage contre Glossina fuscipes fuscipes en République centrafricaine. Les essais réalisés en zone d’élevage de République centrafricaine sur G fuscipes fuscipes ont montré que l’addition d’un appât olfac- tif augmentait systématiquement les captures. Cette augmentation était significative avec l’urine de zébu (x 1,4) et avec le principal hôte reptilien, le varan (x 1,7). L’effet le plus important (x 4,2) a été obtenu pour les glossines mâles, avec l’urine de zébu, lorsque les densités des mouches étaient inférieures à 5 mâlesljlpiège. Ces essais suggèrent la possibilité d’utiliser des appâts olfactifs pour améliorer la lutte par piégeage contre ce vecteur et montrent en particulier la présence de principes attractifs dans l’odeur de reptile, qu’il serait intéressant d’identifier.

Glossina fuscipes fuscipes f tsé-tsé / piégeage / odeurs d’hôtes / reptile / zébu

* Correspondence and reprints INTRODUCTION as a priority. Since cattle urine is directly accessible and easy to use for Peul pas- toralists, the main breeders in Central Trapping is an ecologically preferable alter- African we tested this bait on G f native to the traditional techniques of tsetse Republic, fuscipes. control (ie ground or aerial spraying of ). It is a simple and cheap method To date, all the compounds tested on which can be used directly by the local zebu Glossina spp originated from mammals. breeders to protect their (Drans- However, riverine tsetse flies are oppor- field et al, 1990; Cuisance et al, 1992; Gou- tunistic in their feeding habits (Weitz, 1963), teux and Le Gall, 1992). Although the effec- so that mammals are not always their main tiveness of trapping is proven, improvements hosts. Indeed, in breeding areas of the Cen- to this technique are being sought, includ- tral African Republic, reptiles account for ing increasing the visual attractiveness of between 14 and 26% of the blood meals of the traps and the efficiency of the trapping G f fuscipes (Gouteux et al, 1994b). Given device (Challier et al, 1977; Gouteux et al, the small size of the reptiles, their low pop- 1981; Filledier etal, 1985; Gouteux and ulation density and their discreet mode of Sinda, 1990). Another method of improve- life, it has been suggested that reptiles ment is to add olfactory attractants to the attract the riverine tsetse by odour. Prelim- trap (Vale and Hargrove, 1979; Vale, 1980). inary trials were thus carried out to evalu- The addition of host odours (cattle urine or ate and compare the attraction of Gf sebum, chemical compounds) to traps has fuscipesto reptilian and mammalian odour. considerably improved the control of savanna tsetse (Morsitans group and Glossina longipennis) and is now well documented MATERIALS AND METHODS (Politzar and Merot, 1984; Vale et al, 1988; et al, 1990; Warmes, This is Kyorku 1990). Six trials (trials 1-6) were carried out, using the not, however, the case for the 2 riverine blue-black polyethylene bipyramid traps (Gou- tsetse flies of the Palpalis group, for which teux, 1991), with and without olfactory bait. In research on olfactory attractants has been trial 1, baited and non-baited traps were tested carried out (G palpalis and G tachinoides). simultaneously in pairs. This so-called ’compe- Although carbon dioxide and certain urine tition’ protocol has been used previously by Gou- teux and Lancien (1986) and Cheke and Garms components are attractive alone or in com- (1988). The experimental design of the other tri- bination for these riverine et species (Galey als was the latin square, sites x days x odours, of al, 1986; Merot et al, 1986; Cheke and size 6 (trial 2) or 4 (trials 3-6). For the competi- Garms, 1988), most of the chemicals have a tion protocol, the results were analysed by the t limited effect and some are even repellents test for comparison of the means for matched (Merot etal, 1988; Merot and Filledier, 1989; data. Each latin square was duplicated making Kupper et al, 1991). Trials of olfactory attrac- 2-6 independent square times, and the Tukey test for non-additivity (Dagnelie, 1978) was used tants have not yet been carried out on G f to check interaction (in the sense of Milliken and another riverine tsetse. Since the fuscipes, Graybill, 1972). In the case of non-additivity, the disappearance of G morsitans submorsitans latin square was rejected. If necessary, a trans- from the cattle breeding areas of the Cen- formation (log x + 1, or X112) was applied to tral African Republic (Gouteux et al, 1994a), ensure the normality of the distribution of the G f fuscipes is the main of livestock try- data. The analysis of variance was then carried out for all latin panosomiasis in this area. independent squares (Lellouch and Lazar, 1974). The Dunnet test (Dagnelie, The use of simple community level 1978) was used to compare baited and non- method of tsetse control is acknowledged baited traps. Study zones cages, 1 empty and 3 with , were hidden by covering them loosely with leaves. The cages were interchanged randomly each day. In trial 4 The 6 trials were carried out in the following the live animals were a young crocodile zones: Trials 1 and 2 (February 1991 ): Ban River, (Crocodilus niloticus), a monitor lizard (Varanus ’Zone of Yérémo agro-pastorale’ (ZAGROP) niloticus) and a snake (Pyton sebae). In trial 5, trials 3 (Bossembele); (December1991 ), (June a mammal (rabbit), a bird (chicken) and a reptile and 5 Gbal6 Zakai 1992) (July 1992): lake, (Ban- (monitor lizard). All the hosts were of comparable trial 6 Mbonou ’Com- gui); (June 1992): River, size except for the crocodile which was about mune d’elevage’ of Ouro-Djafoun (Bambari). twice the size of the others. Trial 6 was carried out The trials were carried out in forest galleries, in a cattle watering place. The protocol is therefore 3-4 and 11 km from the cattle watering places slighty different from trials 2 and 3; odour was (Ban River and Gba]6 lake, respectively) or at tested by placing successively in each trap a the watering place frequented daily by cattle sponge impregnated with water, zebu urine, dung (Mbonou River). The characteristics of these sites or sebum (’body odour’, obtained by rubbing the are given by Gouteux et al (1994b). sponge on the ’s body). The plastic traps were washed each time with soap.

Protocols RESULTS Trial 1. Competition protocol The total catches for each of the trials 1-6 Two fixed traps were placed 20 m apart near iso- were 4133 lated water-holes under the forest gallery. They respectively 233, 410, 940, 182, and 294 G 2 472 flies. were not visible from one another. A sponge was f fuscipes totalling placed on a waterproof plastic sheet under each The catches were systematically higher with trap. Each day, one was moistened with zebu the baited traps (except for zebu sebum) as urine and the with (test attractant) other water shown in table I. Significant results were The were (control). sponges alternated each day. produced in 4 experiments for 2 baits: zebu The experiment lasted 28 d and the catch was urine and the monitor lizard recorded daily. (trials 1-3) (trial 5). Compared to the controls, the number of G f fuscipes caught was multiplied by 1.4 Trial 2. Latin x squares (6 6) replicated in the presence of urine and 1.7 with the 3 times monitor lizard. During trial 3, when the tsetse was low 5 males Six traps were fixed at 6 capture sites, 25-100 m fly density (under per trap apart, along the forest gallery and at mutually per day) the attractant effect of urine for the invisible positions. Six sponges, 3 of which were male G f fuscipes was significant (F3-6 = impregnated daily with zebu urine (test attrac- 18.173, p < 0.0005) (table II). The number of tant) and 3 with water were ran- (controls) placed males caught was multiplied by 4.2. This domly each day under the traps, with one sponge was the trial in which there was a per trap. only sig- nificant difference in the fly sex ratio between the control and baited trap catches (x2 = Trials 5 and 6. Latin x 3, 4, squares (4 4) 8.72, p = 0.003). replicated 3, 2, 6 and 2 times respectively

The protocol for trial 3 was the same as for trial 2. Four sponges, 2 impregnated with urine (test DISCUSSION attractant) and 2 with water (controls), were inter- changed randomly each day. Trials 4 and 5 stud- The work ied the efficacy of odours from live animals, which present suffered from the gener- were placed singly in cages (100 x 50 x 50 cm), ally low density of G f fuscipes in the study 10-30 cm from the traps (1 cage per trap). The 4 area (Blanc et al, 1991 making it difficult to expose significant effects. Nevertheless a the monitor lizard. Because of their slow significant attractive effect was demon- metabolism, reptiles produced less C02 strated for zebu urine and the monitor lizard. than mammals or birds of the same weight. For other baits the results are generally con- Therefore specific components of reptile sistent with an attractive effect of the host odour are probably factors in the odour. attraction. Varanus sp is fairly common in This is the first demonstration of the . In the cattle breeding areas of the attractive effect of reptile odour, in this case Central African Republic, the monitor lizard provides 89% of the reptile blood meals useful comments and help in the final writing of taken by this fly (Gouteux et al, 1994b). the manuscript. This work was supported in part However, elsewhere crocodiles have often by the government of the Central African Repub- lic, Orstom (UR 41, Maladies infectieuses et para- been observed to be a host for G f major sitaires), World Bank-International Fund for Agri- fuscipes (Weitz, 1963; Van vegten, 1971). cultural Development (IFAD), European Fund for Hence trials with other reptile species, espe- Development (EFD) and Fonds d’aide et de cially with the crocodile, need to be con- cooperation (FAC), France. ducted.

The attractive effect of zebu urine was REFERENCES not significant in 1 trial (6) out of 4. This result may be due to the protocol. Indeed, some chemicals migrate into plastic and do Blanc F, Gouteux JP, Cuisance D, Pounekrozou E, N’Dokoué Le Gall F Étude de la not wash off, but still smell. The result could F, (1991) r6parti- tion des tsé tsé (Diptera: Glossinidae) en zone de also be related to the particular environment savane humide (R6publique centrafricaine). tvalu- of this trial at the cattle watering place. The ation de techniques de prospection entomologique. Trop Med Parasitol42, 127-130 presence of cattle excrement throughout Challier A, Laveissibre C the capture site may diminish the effective- Eyraud M, Lafaye A, (1977) Amelioration du rendement du piege biconique pour ness of the odour in the trap. However, this glossine (Diptera: Glossinidae) par I’emploi d’un cone needs to be verified by further trials in order inferieur bleu. 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