D'Amico, F.

Gouteux, Jean-Paul

Kounda Gboumbi, J-C.

Noutoua, L.

Horizon / Pleins textes

Acta Tropica, 5 1(1992)163-166 
0 1992 Elsevier Science Publishers B.V. All rights reserved 0001-706X/92/$05.00 
ACTROP 00214 
Short Communication 
163 
Glossina fuseìpes fuscìpes and Glossina palpalis 
palpalis as joint vectors of sleeping sickness in the 
focus of Nola-Bilolo in the Central African 
Republic 
J.P. Gouteuxa, F. D’Amico”, J.C. Kounda Gboumbib, L. Noutouab 
and C. Baillyb 
“ORSTQM, Centre QRSTOM de Bangui, and ’D.M.P.G.E., Bangui, Central Afiican Republic 
(Received 10 December 1991; accepted 26 February 1992) 
Key words: Glossina palpalis palpalis; Glossina fuscipes fuscipes; Nola-Bilolo trypanosomiasis focus; 
Central African Republic; Trypanosomiasis 
The largest focus of human (gambian) trypanosomiasis in the Central African 
Republic is the Sangha-M’Baere focus (formerly Haute Sangha), also known as the 
Nola-Bilolo focus (Desfontaines et al., 1988; Bailly et al., 1990). The focus is situated 
in the south-west of the Central African Republic, between Cameroon and the 
Congo. The north is bordered by the Mambéré-Kadei and Lobaye rivers. It is a 
wooded region (semi-deciduous forest). The focus is culrently facing an epidemic 
upsurge. In January 1991, 109 new cases were notified, and 836 immunologically 
suspect cases were identified with the Testryp CATTR. 
Although the Central African Republic is situated in the Glossina fuscipes fuscipes 
zone, the presence of G. palpalis palpalis in the region of Nola has been known since 
1948 where a few specimens were captured (Grejbine, in Maillot, 1953). Maillot 
(1961) has since confirmed this, particularly near the Kadeï and Sangha rivers. 
G. palpalis palpalis is also marked, rather imprecisely, near Nola, on Finelle’s maps 
of Glossina distribution in Central African Republic (Finelle et al., 1963). No data 
were collected on the entomological situation in the Nola-Bilolo focus. No reliable 
entomological surveys have been carried out more recently. Reports on the most 
recent vector control trials with traps refer only to G. fuscipes fuscipes (Lancien , 
et al., 1985; Noutoua, 1985, 1986). This paper presents the first result of a 3-month 
tsetse trapping investigation in this reviving focus. 
The focus lies either side of the road from Nola to Yokadouma in Cameroon. 
Eleven villages were investigated (Carombois, Mekara, Kaolo, Bindjo, Nkouala, 
M’Poyo, Bilolo, Abogui, Domissili, Anam, Ziendi) in January, February and March 
., 
Correspondence address: J.-P. Gouteux, Centre Orstom de Bangui, B.P. 893, Bangui, Central African 
Republic. 
- ___ - ------ 
i- -- 
Fonds Documentaire ORSTQM 
Cote : 9.k-lleA?2 Ex: L 
164 
1991 (end of the dry season). The survey was carried out in each village by trapping 
the tsetse flies in the main biotopes. From 4 to 15 bipyramid traps (Gouteux, 1991 
were used continuously for 10 to 25 days. The flies were collected from the traps at 
least once a week. All the collected Glossina were preserved in alcohol for further 
laboratory examination. The male genitalia were mounted and the species determined 
in the Bangui ORSTOM laboratory according to the method of Machado (1954). 
A joint screening survey was carried out in January 1991 by the teams of the No. 3 
Health Region (Berberati) and the trypanosomiasis programme (Bangui). During 
this survey 109 new cases presenting trypanosomes in lymph nodes were detected, 
among these 107 reside in the 73 villages from Nola to Cameroon frontier. A total 
of 1663 Glossiria belonging to the G. palpalis group were captured in the study area. 
None belonged to the G. fitsca group. The examination of the male genitalia demon- 
strated that both subspecies, Glossina palpalis palpalis and G. firscipes firscipes. were 
present in the focus. The inter-species frontier passes through Anam and Domissili 
villages, where both species co-exist. According to the results of the January 1991 
screening survey (Table 1 1. both species were effective vectors of sleeping sickness, 
and moreover the vectorial abilities appear not to be significantly different = 
0.98). G. palpalis palpalis is the vector from Nola to Siemho, G. j'itscipes~fit.wipe.s at 
Ziendi and in the remainder of the focus. Both species may be involved in transmis- 
sion at Anam and Domissili. 
Relict tsetse jj) popirlatioizs arid endemic .foci 
The existence of relict pockets of G. palpalis paIpali.7 may be of particular epidemio- 
logical interest. Indeed, the tsetse ecology and vector ability vary greatly according 
to the species. Maillot (1961) underlined the rale of local races on the maintenance 
of endemic foci, especially when they occur at the geographical limits of the distribu- 
tion area of the species. This situation applies to the G. palpalis palpulis population 
in this region. G. palpcdis palpalis is normally a coastal species in Central Africa. 
The isolated populations of the Nola region are thus at the eastern limit of the 
species. It is of interest to note that the greater part of this focus is situated within 
one of these relict G. palpalis pockets. This seems to confirm the observation made 
by Maillot (1961). 
The high Glossina densities in the coffee plantations had already been noted in Bilolo 
during the preliminary trapping trials (Noutoua. 1985, 19863. However, the species 
TABLE 1 
Comparison of sleeping sickness prevalence rate, according to the species present in the Nola-Bilolo focus 
(excluding Nola City and the two villages with mixed species) 
Species (vector) T+ Number of Prevalence 
patients rate ( ' 0 )  
165 
TABLE 2 
Tsetse distribution 
The apparent densities per trap (AD) are expressed as the number of flies per trap per day (-, no datum). 
i 
Species Village Mean AD per biotope 
AD 
village coffee cassava bathing 
G. p .  palpalis 
G. p .  palpalis 
+ 
G. f. fuscipes 
G.f .  fuscipes 
Carambois 
Mekara 
Bindjo 
Kaolo 
Nkouala 
M'Poyo 
Bilolo 
Abogui 
Domissili 
Anam 
Ziendi 
0.21 
0.18 
0.41 
1 .o0 
0.93 
10.66 
4.58 
0.66 
0.78 
0.38 
5.04 
0.03 
0.00 
0.10 
1 .O6 
0.53 
0.30 
0.66 
0.10 0.34 
0.02 0.41 
1.25 0.15 
1.00 .- 
1.23 0.69 
24.78 4.00 
8.13 1.00 
0.78 0.60 
0.71 0.35 
0.65 1.20 
1.08 4.39 
0.35 
0.33 
0.55 
1.42 
2.44 
- 
- 
1.06 
0.30 
18.54 
was misidentified, since G. fuscipes fuscipes alone was incriminated (Lancien et al., 
1985). At M'Poyo, G. palpalis palpalis presents densities 4-times higher in the coffee 
plantations near the villages than near the water (cassava setting sites and washing 
or bathing areas), whereas in Ziendi G. fuscipes fuscipes presents densities 12-times 
higher near the backwaters than in the coffee plantations (Table 2). Thus, at least in 
the dry season, the principal man-fly contact points appear to differ according to 
the species. 
To our knowledge, this sleeping sickness focus is the first in which two vector 
species, G. p .  palpalis and G.f. fuscipes, are involved. This raises questions regarding 
parasite-vector relationships and their reciprocal adaptation. It thus seems necessary 
to conduct more thorough entomological and parasitological studies in the Nola- 
Bilolo focus, in order to understand the original features of the epidemiological 
situation and to break the transmission by especially adapted and effective vector 
control. 
References 
Bailly, C., Yaya, M. and Roungou, J.B. (1990) La trypanosomiase humaine en République Centrafricaine. 
Historique - Epidemiologie - Actualité. Bull. O.C.E.A.C. 93, 12-16. 
Desfontaine, M, Rongou, J.B., Ngembi, E., Kanda, P., Baquillon, G. and Limbassa, J. (1988) Lutte 
contre la trypanosomiase humaine en République Centrafricaine. Inter-Fac Afrique, 7, 1 1-14. 
Finelle, P., Itard, J., Yvore, P. and Lacotte, R. (1963) Répartition des glossines en R.C.A. Etat actuel 
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n 


Glossina fuscipes fuscipes and Glossina palpalis palpalis as joint vectors of sleeping sickness in the focus of Nola-Bilolo in the Central African Republic

Glossina fuscipes fuscipes and Glossina palpalis palpalis as joint vectors of sleeping sickness in the focus of Nola-Bilolo in the Central African Republic

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