Glossina Palpalis Research Articles

Predicted distribution and movement of Glossina palpalis palpalis (Diptera: Glossinidae) in the wet and dry seasons in the Kogo trypanosomiasis focus (Equatorial Guinea)

The aim of this study was to predict the distribution and movement of populations of the tsetse fly, Glossina palpalis palpalis (Diptera: Glossinidae), in the wet and dry seasons and to analyze the impact of the use of mono-pyramidal traps on fly populations in the Kogo focus in 2004 and 2005. Three Glossina species are present in Kogo: Glossina palpalis palpalis, major HAT vector in West-Central Africa, Glossina caliginea, and Glossina tabaniformis. The apparent density (AD) of G. p. palpalis clearly fell from 1.23 tsetse/trap/day in July 2004 to 0.27 in December 2005. A significant reduction in the mean AD for this species was noted between seasons and years. The diversity of Glossina species was relatively low at all the sampling points; G. p. palpalis clearly predominated over the other species and significantly dropped as a consequence of control activities. The predictive models generated for the seasonal AD showed notable differences not only in the density but in the distribution of the G. p. palpalis population between the rainy and dry season. The mono-pyramidal traps have proven to be an effective instrument for reducing the density of the tsetse fly populations, although given that the Kogo trypanosomiasis focus extends from the southern Equatorial Guinea to northern Gabon, interventions need to be planned on a larger scale, involving both countries, to guarantee the long-term success of control.

Tsetse control in cattle from pyrethroid footbaths

In Burkina Faso, we assessed the efficacy of treating cattle with a footbath containing aqueous formulations of pyrethroids to control two tsetse-fly species, Glossina tachinoides Westwood, 1850 (Diptera, Glossinidae) and Glossina palpalis gambiensis Vanderplank 1949. Legs were the most targeted parts of the body for tsetse-fly blood meals: 81% (95% CI: 73, 89) for G. tachinoides and 88% (81, 95) for G. palpalis. The in-stable efficacy of footbath treatments was compared with manual full spraying with a 0.005% alphacypermethrin (Dominex, FMC, Philadelphia, USA) formulation (250 mL versus 2 L). The proportions of knocked-down flies were the same with footbath and full spray but the latter was more protective against fly bites. In field use, the efficacy of both methods should be similar given the recommended treatment frequency: 3 days for footbath versus 7 days for full spray. Among 96 cattle drinking at the same water point in Dafinso (Burkina Faso), 68 (71%) were treated with a footbath containing a 0.005% deltamethrin formulation (Vectocid, CEVA SA, Libourne, France). We observed the effect of this live-bait technique on the one hand on released cohorts of reared, irradiated flies, and on the other hand on wild tsetse flies. In both cases, the footbath treatment was associated with a reduction of the apparent fly density probably related to an increased mortality.

Cyclical transmission of Trypanosoma brucei gambiense in Glossina palpalis gambiensis displays great differences among field isolates

Six sets of teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were fed on mice infected with six different isolates of Trypanosoma brucei gambiense (each mouse was infected with one of the isolates), previously isolated from patients in the sleeping sickness focus of Bonon, Côte d’Ivoire and in Makoua, Congo. All the tsetse flies were dissected 42 days post-infection and midgut and salivary glands were examined for trypanosomes by microscopical examination. No infection was observed with the reference stock whereas each of the five recently isolated trypanosome isolates was able to infect tsetse flies, with rates of infection varying between 9.7 and 18.2% depending on the isolate. Three isolates displayed only immature infections with 9.7, 17.3 and 18% of the flies showing trypanosomes in their midgut. One isolate gave both immature (12.1%) and mature infections (6.1%). Finally, the last isolate involved only mature infections in 9.7% of the Glossina species examined. These substantial differences in the cyclical transmission of T. b. gambiense in the same fly species could have important implications for the epidemiology of the transmission of Human African Trypanosomiasis.

Vector Competence of Glossina palpalis gambiensis for Trypanosoma brucei s.l. and Genetic Diversity of the Symbiont Sodalis glossinidius

Tsetse flies transmit African trypanosomes, responsible for sleeping sickness in humans and nagana in animals. This disease affects many people with considerable impact on public health and economy in sub-Saharan Africa, whereas trypanosomes' resistance to drugs is rising. The symbiont Sodalis glossinidius is considered to play a role in the ability of the fly to acquire trypanosomes. Different species of Glossina were shown to harbor genetically distinct populations of S. glossinidius. We therefore investigated whether vector competence for a given trypanosome species could be linked to the presence of specific genotypes of S. glossinidius. Glossina palpalis gambiensis individuals were fed on blood infected either with Trypanosoma brucei gambiense or Trypanosoma brucei brucei. The genetic diversity of S. glossinidius strains isolated from infected and noninfected dissected flies was investigated using amplified fragment length polymorphism markers. Correspondence between occurrence of these markers and parasite establishment was analyzed using multivariate analysis. Sodalis glossinidius strains isolated from T. brucei gambiense-infected flies clustered differently than that isolated from T. brucei brucei-infected individuals. The ability of T. brucei gambiense and T. brucei brucei to establish in G. palpalis gambiensis insect midgut is statistically linked to the presence of specific genotypes of S. glossinidius. This could explain variations in Glossina vector competence in the wild. Then, assessment of the prevalence of specific S. glossinidius genotypes could lead to novel risk management strategies.

Genetic and Morphometric Evidence for Population Isolation of <I>Glossina palpalis gambiensis</I> (Diptera: Glossinidae) on the Loos Islands, Guinea

Allele frequencies at four microsatellite loci, and morphometric features based on 11 wing landmarks, were compared among three populations of Glossina palpalis gambiensis (Diptera: Glossinidae) in Guinea. One population originated from the Loos islands separated from the capital Conakry by 5 km of sea, and the two others originated from the continental mangrove area close to Dubreka, these two groups being separated by approximately 30 km. Microsatellites and wing geometry data both converged to the idea of a separation of the Loos island population from those of the mangrove area. Although occasional contacts cannot be excluded, our results support the hypothesis of the Loos population of tsetse flies being a completely isolated population. This situation will favor a sequenced intervention against human African trypanosomosis and the possibility of an elimination of tsetse from this island.

The tsetse fly Glossina palpalis palpalis is composed of several genetically differentiated small populations in the sleeping sickness focus of Bonon, Côte d’Ivoire

Glossina palpalis is the main vector of human African trypanosomosis (HAT, or sleeping sickness) that dramatically affects human health in sub-Saharan Africa. Because of the implications of genetic structuring of vector populations for the design and efficacy of control campaigns, G. palpalis palpalis in the most active focus of sleeping sickness in Côte d’Ivoire was studied to determine whether this taxon is genetically structured. High and statistically significant levels of within population heterozygote deficiencies were found at each of the five microsatellite loci in two temporally separated samples. Neither null alleles, short allele dominance, nor trap locations could fully explain these deviations from random mating, but a clustering within each of the two samples into different genetic sub-populations (Wahlund effect) was strongly suggested. These different genetic groups, which could display differences in infection rates and trypanosome identity, were composed of small numbers of individuals that were captured together, leading to the observed Wahlund effect. Implications of this population structure on tsetse control are discussed.

Insemination, pregnancy and abortion rates in a population of <i>Glossina palpalis palpalis</i> (robineau-desvoidy) at a relict forest in the Southern Guinea Savanna, Nigeria

The female populations of Glossina palpalis palpalis were surveyed at the relict forest of River Kajim, Manchok, Nigeria with the objective of determining rates of fertility, types of reproductive losses and the constraints responsible for the reproductive losses. Nullipars constitutes 21.7% of the 272 females dissected. 80.2% of the 213 pars were at different stages of pregnancy; 32.5% had eggs and 20.3%, 17.5% 9.9% had 1st, 2nd and 3rd-instar larvae in their uteri, while 42 pars had empty uteri. Mean monthly pregnancy rates were 70.2 ± 0.03% (57.1%-100%), highest in the peak wet season (34.5%) (July-September) and low in both warm wet (10.6%) (October) and hot dry (11.8%) (February-March) seasons. Virgin females were generally scarce. Abortion, insemination failure and ovular blockage were the common reproductive abnormalities in the population, totaling 9.9%. The results indicate that nutritional and physical stress were the likely constraints to optimum productivity.Keywords: insemination, pregnancy, reproductive abnormality, G. p. palpalis, Southern Guinea SavannaTropical Veterinarian Vol. 23(1) 2005: 25-31

A phyto‐sociological analysis of the distribution of riverine tsetse flies in Burkina Faso

In Burkina Faso, Glossina palpalis gambiensis Vanderplank and G. tachinoides Westwood (Diptera: Glossinidae) are the main cyclic vectors of trypanosomiasis. The vegetation type along river banks is an important factor determining the distribution and abundance of these tsetse. The following work investigated the relation between the plant species present (including the disturbance level) and tsetse distribution and abundance, using three ecotypes, described by P.C. Morel in 1978. These were the Guinean, Sudano-Guinean and Sudanese gallery forests. In the Mouhoun River basin, these three ecotypes are found successively from upstream to downstream. Berlinia grandiflora, Syzygium guineense and Cola laurifolia and finally Acacia seyal and Mitragyna inermis were the best indicators for the Guinean, Sudano-Guinean and Sudanese gallery forest ecotypes, respectively, as suggested by Morel. However, other species such as Pterocarpus santalinoides and Mimosa pigra were not ecotype specific. Trap catches confirmed that G. palpalis and G. tachinoides are predominant in Guinean and Sudanese gallery forests, respectively, and that both species are well represented in the Sudano-Guinean ecotype. Tsetse densities dropped significantly in disturbed Sudano-Guinean and Sudanese gallery forest sites. However, this was not the case for both species in Guinean or for G. tachinoides in half-disturbed Sudanese gallery forest sites, confirming their high resilience to human-made changes. The importance of a detailed consideration of riverine ecotypes when predicting tsetse densities is discussed.

Sodalis glossinidius (Enterobacteriaceae) and Vectorial Competence of Glossina palpalis gambiensis and Glossina morsitans morsitans for Trypanosoma congolense Savannah Type

Sodalis glossinidius is an endosymbiont of Glossina palpalis gambiensis and Glossina morsitans morsitans, the vectors of Trypanosoma congolense. The presence of the symbiont was investigated by PCR in Trypanosoma congolense savannah type-infected and noninfected midguts of both fly species, and into the probosces of flies displaying either mature or immature infection, to investigate possible correlation with the vectorial competence of tsetse flies. Sodalis glossinidius was detected in all midguts, infected or not, from both Glossina species. It was also detected in probosces from Glossina palpalis gambiensis flies displaying mature or immature infection, but never in probosces from Glossina morsitans morsitans. These results suggest that, a) there might be no direct correlation between the presence of Sodalis glossinidius and the vectorial competence of Glossina, and b) the symbiont is probably not involved in Trypanosoma congolense savannah type maturation. It could however participate in the establishment process of the parasite.

Trypanosomose Humaine Africaine: transmission urbaine dans le foyer de Bonon (Côte d'Ivoire)

Human African trypanosomiasis (HAT) is a vector-borne parasitic disease which has often been considered a rural disease. Population increases in African countries have entailed the spread of urban centres, creating favourable conditions for the appearance of new epidemiological conditions. In Cote d'Ivoire, HAT transmission has been described in the surroundings of towns such as Daloa or Sinfra. In the focus of Bonon, located in central-western Cote d'Ivoire, a medical survey detected 96 patients. The sites visited by the patients every day were geo-referenced and the routes between them recorded. In parallel, an entomological survey of the patients' daily locations enabled the collection of data on the vector. In Bonon, we observed urban cases and tsetse (Glossina palpalis) feeding on men. Trypanosoma brucei gambiense was identified in both man and vector; thus all conditions for possible intra-urban trypanosomosis transmission were met. The consequences of this are discussed regarding the problem of diffusion of the disease.

Increased expression of unusual EP repeat-containing proteins in the midgut of the tsetse fly ( Glossina) after bacterial challenge

Proteins containing a glutamic acid–proline (EP) repeat epitope were immunologically detected in midguts from eight species of Glossina (tsetse flies). The molecular masses of the tsetse EP proteins differed among species groups. The amino acid sequence of one of these proteins, from Glossina palpalis palpalis, was determined and compared to the sequence of a homologue, the tsetse midgut EP protein of Glossina m. morsitans. The extended EP repeat domains comprised between 36% ( G. m. morsitans) and 46% ( G. p. palpalis) of the amino acid residues, but otherwise the two polypeptide chains shared most of their sequences and predicted functional domains. The levels of expression of tsetse EP protein in adult teneral midguts were markedly higher than in midguts from larvae. The EP protein was detected by immunoblotting in the fat body, proventriculus and midgut, the known major immune tissues of tsetse and is likely secreted as it was also detected in hemolymph. The EP protein was not produced by the bacterial symbionts of tsetse midguts as determined by genome analysis of Wigglesworthia glossinidia and immunoblot analysis of Sodalis glossinidius. Bacterial challenge of G. m. morsitans, by injection of live E. coli, induced augmented expression of the tsetse EP protein. The presence of EP proteins in a wide variety of tsetse, their constitutive expression in adult fat body and midguts and their upregulation after immunogen challenge suggest they play an important role as a component of the immune system in tsetse.

X-chromosome mapping experiments suggest occurrence of cryptic species in the tsetse fly Glossina palpalis palpalis

Using flies from colonies of Glossina palpalis palpalis (Robineau-Desvoidy, 1830) (Diptera: Glossinidae) that originated in Nigeria and Bas-Zaire, the two microsatellite loci Gpg19.62 and Gpg55.3 have been added to the X-chromosome map, thus increasing to seven the number of loci mapped on that chromosome. During the mapping and other crossing experiments, sterile F1 and backcross males were found. Similarities between the patterns of sterility found in the present study and those occurring during hybridization of some subspecies of tsetse suggest that the nominal taxon G. p. palpalis may contain cryptic taxa. Differences in the width of the postgonite head of males from the two colonies were consistent with this suggestion.

A peridomestic population of the tsetse fly Glossina palpalis palpalis Robineau-Desvoidy, 1830 (Diptera: Glossinidae) at Kontagora town, Niger state, Nigeria

The present article considers some aspects of a peridomestic population of the tsetse fly Glossina palpalis palpalis Robineau-Desvoidy, 1830 in Kontagora, Nigeria. This situation characterizes an abnormal behaviour of the vector, and it is of significant epidemiological importance. Data on the ecology of this species were collected in 1995 and 1999. The results indicated that the species exists during both dry and wet seasons; approximately 30.0% of the catches were gorged with blood giving a MHS of 2.4, indicating a well-nourished population. Dissection of inseminated pars indicated pregnancy rates of approximately 30.0% and 70.0% in the dry and wet seasons and the presence of all 4 stages of pregnancy, suggesting that breeding occurs at both seasons. Longevity of flies was approximately 16 days in dry season and 25 days in the wet season. Overall results indicated that vector/host contact was high and the fly population has adapted and actively breeding in the area. Trypanosome infection rates of 18.2% consist of 1 brucei-type and 5 vivax-type infections. The public health implications of the close proximity of the wild natural reservoir hosts of the human T. b. gambiense Dutton, 1902 parasites at the Kainji Wild Life park is discussed.

Mixed infections of trypanosomes in tsetse and pigs and their epidemiological significance in a sleeping sickness focus of Côte d'Ivoire

In a sleeping sickness focus of Côte d'Ivoire, trypanosomes were characterized in humans, pigs and tsetse using various techniques. Out of 74 patients, all the 43 stocks isolated by KIVI (Kit for In Vitro Isolation) appeared to belong to only one zymodeme of Trypanosoma brucei gambiense group 1 (the major zymodeme Z3). The only stock isolated on rodents belonged to a different, new, zymodeme (Z50), of T. b. gambiense group 1. From 18 pigs sampled in the same locations as the patients, PCR showed a high proportion of mixed infections of T. brucei s. l. and T. congolense riverine-forest. Zymodemes of T. brucei s. l. from these pigs were different from those found in humans. From a total of 16 260 captured tsetse (Glossina palpalis palpalis), 1701 were dissected and 28% were found to be infected by trypanosomes. The most prevalent trypanosome was T. congolense riverine-forest type, followed by T. vivax, T. bruceis. l. and T. congolense savannah type, this latter being associated to the forest type of T. congolense in most cases. Mixed infections by 2 or 3 of these trypanosomes were also found. Use of a microsatellite marker allowed us to distinguish T. b. gambiense group 1 in some of the mature infections in tsetse. Differences in infection rates and in trypanosome genotypes according to the host might indicate that the pig may not be an active animal reservoir for humans in this focus.

Mitochondrial diversity analysis of Glossina palpalis gambiensis from Mali and Senegal

West African riverine tsetse populations of Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) were investigated for gene flow, inferred from mitochondrial diversity in samples of 69 flies from Senegal and 303 flies from three river drainages in Mali. Four polymorphic mitochondrial loci were scored. Mean haplotype diversities were 0.30 in Mali, 0 in Senegal and 0.18 over both Mali and Senegal. These diversities estimate the probabilities that two randomly chosen tsetse have different haplotypes. Substantial rates of gene flow were detected among flies sampled along tributaries belonging to the river basins of the Senegal, Niger, and Bani in Mali. There was virtually no gene flow between tsetse in Senegal and Mali. No seasonal effects on gene flow were detected. The implications of these preliminary findings for the implementation of area-wide integrated pest management (AW-IPM) programmes against riverine tsetse in West Africa are discussed.

The Macrocyclic Lactone "Spinosad," a Promising Insecticide for Tsetse Fly Control

The susceptibility of tsetse flies (Diptera: Glossinidae), Glossina palpalis gambiensis (Vanderplank), and G. m. morsitans (Westwood) to topically applied spinosad, a mixture of insecticidal molecules from the actinomycete Saccharopolyspora spinosa, is almost as high as to deltamethrin. However, susceptibility to spinosad does not differ significantly between teneral and gravid flies, contrary to deltamethrin. Spinosad might be a promising candidate for future tsetse control by the sequential aerial technique.

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method

A study of host preference in tsetse flies using a modified heteroduplex PCR-based method is described. Domestic and wild animal blood samples were collected to extract the corresponding reference DNAs. In Campo (south Cameroon), tsetse flies (mainly Glossina palpalis palpalis) were trapped and 41 bloodmeals were collected. All reference DNAs and 37 bloodmeal DNAs (90.7%) were successfully amplified and hybridised. Twelve bloodmeals (32.4%) were of human origin, 13 (35.4%) were from Sitatunga ( Tragelaphus spekei) (an antelope) while 12 (32.4%) were not identified using our set of reference DNAs. The results confirmed the occurrence of frequent contacts between wild animals and this population of tsetse flies.

Determination of sleeping sickness transmission risk areas from trypanosome infection rates of tsetse flies in Daloa, Côte. d'Ivoire

A study was carried out for four years in the forest area of Daloa in Cote d’Ivoire to assess the rate of trypanosome infection in tsetse, and thereby the trypanosomiasis infection risk. In different Glossina biotopes, 18,908 Glossina palpalis palpalis were caught with Vavoua traps and were dissected. The most widespread species of trypanosomes infecting the Glossina was Trypanosoma congolense (7.63%) followed by T. vivax (4.50%). Trypanosoma brucei, the trypanosome responsible for animal and human African trypanosomiasis (HAT), was found only in 34 of the tsetse flies collected, and it had a very low infection rate (0.18%). Although infected tsetse flies were captured in all habitats examined, the infection rate was relatively higher along footpaths (0.44%), in farms (0.20%) and around forested water springs (0.27%) compared to the edge of villages (0.06%) and forest borders (0.05%). Among the 34 tsetse flies infected with T. brucei, only 0.05% had parasites exclusively in their salivary glands. Our results suggest that footpaths, plantations of coffee and cocoa and forested water springs are potential biotopes where the risk of infection by T. brucei is most important. The anthropophily of Glossina associated with the high number of parasites in these sites could be the reason for the disease is endemic in Daloa today. In our study, female Glossina were infected more frequently with trypanosomes (0.14%) than males (0.04%) and generally, females lived longer than males. It is likely that the longevity of females, which carry parasites, is the major cause for the endemicity of HAT in this locality.

A cross-sectional epidemiological survey of bovine trypanosomosis and its vectors in the Savelugu and West Mamprusi districts of northern Ghana

The epidemiology of bovine trypanosomosis was investigated in two districts (Savelugu and West Mamprusi) of Northern Ghana with different land use and environmental characteristics. The land use intensity and environmental change was suspected to be higher in the Savelugu District. A cross-sectional entomological survey conducted along the White Volta river and its tributaries confirmed the presence of only Glossina palpalis gambiensis and G. tachinoides. The challenge index as measured by the product of tsetse density and tsetse infection rate was much higher in the West Mamprusi (19.6) than in the Savelugu district (4.7). A total of 1013 cattle (508 in Savelugu and 505 in West Mamprusi) were bled from a random selection of 16 villages in the Savelugu District and 13 villages in the West Mamprusi District. Blood samples were examined for trypanosomes by the buffy coat technique (BCT). Blood samples that were positive in the BCT or negative in the BCT but with packed cell volume (PCV) values below 21 were further tested with a polymerase chain reaction for trypanosomal DNA. Plasma samples of all cattle were serologically tested with an indirect ELISA for trypanosomal antibodies. The parasitological and serological prevalence of bovine trypanosomoses was significantly higher in West Mamprusi (16 and 53%, respectively) than in Savelugu District (8 and 24%, respectively). An evaluation of animal health at the village herd level, using PCV as an index of anaemia, provided various epidemiological scenarios prevalent in the entire study area.

Inhibition of the DNA amplification of trypanosomes present in tsetse flies midguts: implications for the identification of trypanosome species in wild tsetse flies.

The present study was carried out in order to investigate if there was really a failure of PCR in identifying parasitologically positive tsetse flies in the field. Tsetse flies (Glossina palpalis gambiensis and Glossina morsitans morsitans) were therefore experimentally infected with two different species of Trypanosoma (Trypanosoma brucei gambiense or Trypanosoma congolense). A total of 152 tsetse flies were dissected, and organs of each fly (midgut, proboscis or salivary glands) were examined. The positive organs were then analysed using PCR. Results showed that, regardless of the trypanosome species, PCR failed to amplify 40% of the parasitologically positive midguts. This failure, which does not occur with diluted samples, is likely to be caused by an inhibition of the amplification reaction. This finding has important implications for the detection and the identification of trypanosome species in wild tsetse flies.