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A Survey of the Species Composition, Distribution and Relative Abundance of Tsetseflies (Diptera: Glossinidae) of Adjumani District, North Western Uganda

Essay 2013 22 Seiten

Medizin - Sonstiges

Leseprobe

TABLE OF CONTENTS

ABSTRACT

LIST OF TABLES

LIST OF ACRONYMS

INTRODUCTION

MATERIALS AND METHODS

RESULTS AND DISCUSSIONS

GENERAL RECOMMENDATIONS: The benefits and the future

CONCLUSION

BIBLIOGRAPHY

ABSTRACT

Adjumani District, located in the northwestern part of Uganda, has had a long history of tsetse and trypanosomiasis. However, tsetse control methods and operations in the district were being guided by mere number and location of sleeping sickness cases treated in Adjumani Hospital and complaints of tsetse infestation received from the villages, without reference to precise knowledge of the particular tsetse species present, their distribution and relative abundance. It was thought that only one riverine tsetse fly species existed in the district. Accordingly only one tsetse control method of tsetse trapping using insecticide treated pyramidal traps meant for riverine tsetse was being promoted in the district. A systematic tsetse survey was therefore planned to establish the particular tsetse species present in the district. 7 locations (parishes) were first selected for a preliminary area-wide tsetse survey, basing on number and location of sleeping sickness cases treated in Adjumani Hospital. The preliminary survey was then carried out in the 7 selected locations (parishes) to determine trapping sites. 10 pyramidal traps were deployed at a distance of 250m apart along river banks in each village in the location, and checked (milked) after 72 hours (3 days). A total of 220 pyramidal traps were used. Six locations found to have tsetse flies were considered as study locations. Two villages were selected as trapping sites in each of the 6 study locations on the basis of high baseline fly trapping density (FTD) or species complexity, giving a total of 12 trapping sites. FTD was calculated as the number of flies caught per trap per day. Routine trapping in the trapping sites took 6 months from April to September 2002. Three pyramidal traps and 3 biconical traps were deployed, spaced 50m apart in each trapping site to catch adult tsetse flies, and checked after every 24 hours (1 day), once a week, giving a total of 24 samples for each trapping site. Tsetse fly species caught were identified using external morphological features. The survey revealed that at least 3 different species of tsetseflies exist in the district: Glossina fuscipes fuscipes, G. morsitans, and G. pallidipes. G. f. fuscipes was the most abundant species distributed in all the 6 parishes and 12 trapping sites with an average fly trapping density (FTD) of 1.765, followed by G. m. submorsitans found in Maaji-Sinyanya-Ofu Village in Ukusijoni Parish, Okawa Village in Palaro Parish and Pakwinya Village in Odu Parish with an average FTD of 0.174 and the least abundant species being G. Pallidipes confined to Maaji-Sinyanya-Ofu Village in Ukusijoni Parish, with an average FTD of 0.0308. In total 1,570 tsetse flies were caught during the survey period which disaggregated into 635 males (40%), 935 females (60%). There were 416 non-teneral male tsetse flies (26%) and 219 teneral male tsetse flies (14%), 637 non-teneral female tsetse flies (41%) and 298 teneral female tsetse flies (19%). During the survey period, a total of 41 Sleeping Sickness cases from the 6 study locations (parishes) was being treated in Adjumani Hospital, which disaggregated into 6 Sleeping Sickness stage I cases (1 male national 2.4%, 2 female nationals 4.8%, 3 male refugees and other people from Southern Sudan 7.3%, 0 female refugees and other people from Southern Sudan 00%), and 35 Sleeping Sickness stage II cases (6 male nationals 14.6%, 2 female nationals 4.8 %, 8 male refugees and other people from Southern Sudan 19.5%, 19 female refugees and other people from Southern Sudan 46.3%). This information on the three different tsetse species present and their distribution pattern in the district should now be used to guide choice of species specific tsetse control methods in future.

LIST OF TABLES

Table 1: The Tsetse Fly Survey Study Locations (Parishes) and Trapping Sites (Villages) in Adjumani District, April – September 2002

Table II: Results of Preliminary Tsetse Survey

Table 3: The Number of Tsetse Flies Caught per Site per Location, April – September 2002

Table IV: FTD per Site per Location, April – September 2002

Table 5: Monthly Tsetse Fly Age and Sex Distribution in Adjumani District, April – September 2002

LIST OF FIGURES

Figure 1: Species Composition, Distribution, and Relative Abundance of Tsetse Fly Species of Adjumani District, April – September 2002

Figure II: Monthly Tsetse Fly Catches in Adjumani from April to September 2002

Figure 3: Tsetse Species Identified from April to September 2002

Figure IV: Distribution of Sleeping Sickness Patients by Geographical Location and Stage of the Disease

Figure 5: Monthly Percentage Composition of Ugandan Nationals and Southern Sudanese Refugees among SS Patients Admitted in Adjumani Hospital from April to September 2002

LIST OF ACRONYMS

Abbildung in dieser Leseprobe nicht enthalten

INTRODUCTION

Adjumani District, formerly called East Moyo County of the neighbouring Moyo District, is located in north western Uganda, 2053”N to 3037”N and 31024”E to 3204”E in the west Nile Region, lying on the low plateau at an altitude of 9000-1500m above sea level (Rwabwoogo, 1998). It is bordered on the north and west by Moyo District, in the northeast by the Southern Sudan and on east and South by Gulu District and on the Southwest by Arua and Yumbe districts. The district has an area of 3,128 Km2 (Anonymous, 2002a-unpublished). Dratele (1999) suggested the established climate of the area comprising of two seasons –one rainy season (March –October) and dry season (November-March), although recently the rainfall pattern has become unreliable. There is also a short dry spell in the area in the month of June. The rainfall in the area would normally range from 750 to 1250mm per annum (Rwabwoogo, 1998). The district is general flat and hot especially during dry season (Anonymous, 2000a). It is blessed with a number of water bodies, namely rivers Itirikwa, Esia, Adidi, Tete, Surumu, Odraji and many other seasonal streams, and one forest reserve-Zoka forest (Dratele, 1999). The district is extensive savanna grassland with scattered woodlands and thickets (Rwabwoogo, 1998). The vegetation may be classed into woodlands, moist Combretum savanna and a mosaic of Butyrospemum savanna and dry Combretum savannas (Langdale-Brown, et al., 1964). It has a variety of wild animals such as buffaloes, antelopes, hippopotami, dikes, warthogs, baboons, monkeys, and crocodiles. The human population of Adjumani District by 2002 comprised Southern Sudan refugees and Ugandan nationals. The lot of refugees stood at 70,000 people compared to that of nationals, 130,000, totaling to 200,000 (Anonymous, 2002a-unpublished). Agricultural economic activities carried out in the district include fish farming, cultivation of crops such as simsim, maize, millet, soybeans, etc.; planting of trees such as neem and teak (Rwabwoogo, 1998; and Egadu, 2000-unpublished), rearing of livestock such as cattle, goats, sheep, poultry (Anonymous, 2002b-unpublished). By 2002, the district had 12 sub counties, 34 parishes, and 134 villages. Adjumani District is part of a bigger tsetse and trypanosomiasis bane, in Uganda and Africa in general. Sleeping sickness has been reported in 37 sub-Saharan African countries (Biryomumaisho, 2007; and Science Daily, 2012), including Uganda. According to MAAIF (2012), about 70% of Uganda is tsetse infested (140,000km2), including Adjumani District. The problem of tsetse and trypanosomiasis Adjumani District could have started time immemorial, but the first known recorded history dates back to 1912 when the Christian Missionaries first came to the area (Dratele, 1999). Tsetse and Sleeping Sickness broke-out originating from Boroli Village in Palaro Parish, Pakelle Sub County. The settlers there were forced to leave the place. The missionaries who settled in the neighboring Indriani Village were also forced to leave for Pakelle and Moyo and built missions in Pakelle and Moyo respectively, which stand up to today. Before this escape took place, the first priest in the place Reverend Father Molinario died and was buried in Indriani Village where a monument stands in the abundant place up to today (Drasi Saverio, pers.comm. 2002). Under the then British colonial government, an office for tsetse control was established in the area in 1940, headed by a man called Ogayi. The main methods used were bush clearing, live bait technology, and insecticide spraying on tree trunks and branches. A health centre was also set up in the area in 1945 and a medical team was deployed to treat Sleeping Sickness cases. With the tsetse control and medical teams both actively involved, the tsetse and Sleeping Sickness outbreak was brought under control in 1947 (Drasi Saverio, pers.comm. 2002). In 1968, after independence, tsetse control team was redeployed with the bush clearing and spraying sections to expand areas for human settlement and cultivation (Drasi Saverio, pers.comm. 2002). Since then Sleeping Sickness was only heard of but not seen by the young generation in the area until after 1980 (Drici Eusebio, pers.comm. 2002). The insurgency of 1980 forced many residents of the area to take refuge in Southern Sudan and those who never ran to Southern Sudan gathered in trading centers and churches, leaving the village vacant. The area was over grown by bush and encroached again by bush and wild animals. This gave an opportunity for the tsetse vector population to rise and spread to areas previously reclaimed. While in Southern Sudan people were exposed to high Sleeping Sickness infection. In 1986, many people returned from exile infected with trypanosomiasis in their blood and became exposed to the high number of tsetse flies already waiting in their home areas. The high number of tsetse flies helped to fasten the spread of Sleeping Sickness and this resulted into another epidemic in 1991. Medicine Sans Frontiers (MSF) France came in the district to reduce the provenience by mass screening of the community and treating the patients for Sleeping Sickness in September 1991 (MSF France, 1992; and COCTU, 1995). The Department of Entomology which was already operational in the area was also strengthened further to reduce the vector population. It mobilized the local leaders of high-risk areas and provided them with tsetse traps (Dratele, 1999). The situation eventually subsided. In 1996, yet another Sleeping Sickness epidemic was reported in the area (COCTU, 1996) which was later controlled. Between 1999 and 2001, the prevalence of trypanosomiasis in the district was observed to be on the rise again (Dratele, 1999 and MOH, 2001). The prevalence of bovine trypanosomiasis alone in the district stood at 36.4% (Dratele, 1999). From October 1999 to March 2000, a total of 64 Sleeping Sickness patients had been undergoing treatment in Adjumani Hospital, 13 of them (20%) were Southern Sudanese, 16 (25%) Southern Sudanese refugees living in various settlement camps in the district, and 35 (55%) were Ugandans from within Adjumani and Gulu districts (Anonymous, 2000b-unpublished). There was another outbreak of Sleeping Sickness reported in the area in 2001 (Mutumba-Lule, 2001). The situation was complicated by uncontrolled movement of Southern Sudanese refugees from and to the neighboring southern Sudan where trypanosomiasis had reached epidemic proportions (Hursey, 2001). Yet, there was no tsetse and trypanosomiasis control in Southern Sudan owing to the 20-year old civil war there by then. Health officials had warned that if the situation in Northwestern Uganda was not arrested, the disease could spread to other areas (Mutumba-Lule, 2001). It was even more worrying that there were increasing numbers of melarsoprol drug resistance among Sleeping Sickness patients reported in the area in 2001 (Barett, 2001). There was also corresponding increase in the numbers of the vector tsetse flies in the district recorded earlier in 2000 (Anonymous, 2000c-unpublished). Active (outreach) Sleeping Sickness sensitization and screening programmes by MSF (France) ended around the same time. All along it was thought that only one riverine tsetse fly species existed in the district. Accordingly only one tsetse control method of using insecticide treated pyramidal traps designed specifically to trap riverine tsetse was being promoted in the district. This, systematic, tsetse survey establishes the particular tsetse species present and their distribution patterns in the district, to inform the process of tsetse control planning, the choice of control methods to use, and stop wastage of resources.

Table 1: The Tsetse Fly Survey Study Locations (Parishes) and Trapping Sites (Villages) in Adjumani District, April – September 2002

Abbildung in dieser Leseprobe nicht enthalten

MATERIALS AND METHODS

The materials used include pyramidal traps, biconical traps, fly cages, Canada balsam, entomological boxes and pins, compound microscope, microscope slides and cover slips, naphthalene, labels, stationery, camera (Kodak), panga knives, ethyl acetate, and x10 hand lenses. 7 locations (Parishes) were selected for a preliminary area-wide tsetse survey, basing on number and location of Sleeping Sickness cases treated in Adjumani Hospital from October 1999 to march 2000 (Anonymous, 2000b-unpublished). The preliminary survey was carried out from July 2001 to January 2002 in the 7 selected locations (parishes) to determine trapping sites. 10 pyramidal traps were deployed at a distance of 250m apart along riverbanks in each village in the location, and checked (milked) after 72 hours (3 days). A total of 220 pyramidal traps were used. One location (parish) was found not to have tsetse flies and was dropped. The other six locations were found to have tsetse flies and were then considered as study locations. Two villages were selected as trapping sites in each of the 6 study locations on the basis of high baseline fly trapping density (FTD) or species complexity, giving a total of 12 trapping sites (Table 1). FTD is the number of flies caught per trap per day. Routine trapping in the trapping sites took 6 months from April 2002 to September 2002. Three pyramidal traps and 3 biconical traps were deployed, spaced 50 m apart in each trapping site to catch adult tsetse flies, and checked after every 24 hours (1 day), once a week giving a total of 24 samples for each trapping site. The tsetse flies caught were distinguished from other similar biting flies using the method described by FAO (1982a). Tsetse species caught were identified using external morphological features as described by Smart, et al. (1943), Nash (1969), FAO (1982a) and Cook (1996). Each species of tsetse identified were recorded against the trap number and type of vegetation from which it was collected. Vegetation in each trapping site has been described using the dominant woody species, trees and shrubs, following from Langdale-Brown, et al. (1964). Teneral and non-teneral flies were recognized using the method described by FAO (1982b). Tsetse flies caught were also sexed by observing the ventral surface of the genitalia under the microscope, as described by Nash (1969), and FAO (1982b); presence of hypopygium shows that the tsetse fly is male while the absence shows it is female. FTD was calculated for each trapping site, pooled for each study location and the whole district. Any tsetse fly caught, if still alive, was killed by using ethyl acetate, a method described by FAO (1982b). After having been killed with the killing agent, a number of each species identified was pinned using entomological pins as described by Service (1980) and placed in an entomological box for future reference. Important external diagnostic parts of each tsetse species identified were mounted on microscope slides using the method described by FAO (1982b), drawn and documented for training new tsetse control personnel and to help guide tsetse control personnel to easily identify tsetse species encountered in the field. Naphthalene was placed in the entomological box to prevent the specimens from being eaten by cockroaches, ants, mites and other scavengers and from attack by fungi. All specimens whether pinned in entomological box or mounted on microscope slides have been labeled with the data in pencil as described by Service (1980). Records of fly catches were used to assess the spatial distribution and relative abundance by number of tsetse species at each trapping site and location. Fly catch data were analyzed using the computer program of SPSS 10.1 for Windows. Catch data for female and male flies in each trapping site were analyzed separately. Fly catches were also compared between different trapping sites to assess location effects. Chi-square was used to analyze teneral males, non-teneral males, teneral females and non-teneral females. To compare relative abundance and distribution of the different tsetse species between study locations, each set of data from the traps at different trapping sites were pooled and compared between locations. Results in the following section have been presented in form of tables, graphs and charts.

RESULTS AND DISCUSSIONS

In the preliminary survey using pyramidal traps only, two tsetse fly species were identified: Glossina fuscipes fuscipes of Palpalis group and very few individuals of Morsitans species group (Table II). This provided the baseline information for selecting study locations (parishes) and trapping sites (villages).

Table II: Results of Preliminary Tsetse Survey

Abbildung in dieser Leseprobe nicht enthalten

Results of the systematic survey (Tables 3 and IV) indicate that 3 different tsetse fly species exist in Adjumani District, namely G. f. fuscipes, G. m. submorsitans, and G. pallidipes. Overall, out of the total of 1,570 tsetse flies caught during the survey period, G. f. fuscipes was the most abundant tsetse species distributed in all the 6 parishes and 12 trapping sites with a total of 1,401 individuals caught, giving an average fly trapping density (FTD) of 1.765; followed by G. m. submorsitans found in Maaji-Sinyanya-Ofu Village in Ukusijoni Parish, Okawa Village in Palaro Parish, and Pakwinya Village in Odu Parish with a total of 143 individuals caught, giving an average FTD of 0.174; and the least abundant species being G. pallidipes confined to Maaji-Sinyanya-Ofu Village in Ukusijoni Parish, with a total of only 26 individuals caught, giving an average FTD of 0.0308. Comparing between locations and trapping sites, the highest relative percentage composition of G. f. fuscipes was registered in Palaro Parish (approximately 32%), followed by Paridi Parish (approximately 22%), with the lowest (about 4%) being registered in Ataboo Parish (Figure 1). Although G. m. submorsitans was caught in Okawa Village in Palaro Parish and Pakwinya Village in Odu Parish, the relative percentage composition figures were very negligible in these villages and parishes, compared to that in Maaji-Sinyanya-Ofu Village in Ukusijoni Parish. It appeared to have confined itself again mainly to Maaji-Sinyanya-Ofu Village in Ukusijoni Parish. Ukusijoni Parish therefore had the highest tsetse species diversity. Possibly this distribution pattern of G. f. fuscipes, G. m. submorsitans, and G. pallidipes could have been influenced by the availability of local preferred food sources, as suggested earlier by FAO (1982b) and Minter (1996). Minter (1996) also pointed out that where there is no close contact with man and domestic animals, flies of the Palpalis group show a preference of feeding on large reptiles, such as monitor lizards and crocodiles. Probably this explains why G. f. fuscipes was caught along river courses where these reptiles are found. Species of the Morsitans group obtain most of their blood meals from the wild animals, especially Bovidae and Suidae, that roam the savanna (FAO, 1982b; and Minter, 1996). This could have been the reason for G. m. submorsitans and G. pallidipes all of Morsitans species group to be distributed far away from human settlements in Maaji-Sinyanya-Ofu, Odu, and Okawa villages where the abundance of these wild animals coming from the nearby Zoka Forest is higher. Nevertheless, G. m. submorsitans and G. pallidipes were still caught along the available river courses in those areas. All the three species of G. f. fuscipes, G. m. submorsitans, and G. pallidipes overlapped in Maaji-Sinyanya-Ofu Village in Ukusijoni Parish with no clear boundary while the 2 species of G. f. fuscipes and G. m. submorsitans overlapped in Odu Village in Odu Parish and in Okawa Village in Palaro Parish, also without clear boundary.

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Details

Seiten
22
Jahr
2013
ISBN (eBook)
9783668670969
ISBN (Buch)
9783668670976
Dateigröße
617 KB
Sprache
Englisch
Katalognummer
v212604
Institution / Hochschule
Atlantic International University – School of Science and Engineering
Note
A
Schlagworte
survey species composition distribution relative abundance tsetseflies diptera glossinidae adjumani district north western uganda

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Titel: A Survey of the Species Composition, Distribution and Relative Abundance of Tsetseflies (Diptera: Glossinidae) of Adjumani District, North Western Uganda