Blood meal analysis of tsetse flies (Glossina pallidipes: Glossinidae) reveals higher host fidelity on wild compared with domestic hosts

Background: Changes in climate and land use can alter risk of transmission of parasites between domestic hosts and wildlife, particularly when mediated by vectors that can travel between populations. Here we focused on tsetse flies (genus Glossina), the cyclical vectors for both Human African Trypanosomiasis (HAT) and Animal African Trypanosomiasis (AAT). The aims of this study were to investigate three issues related to G. palldipes from Kenya: 1) the diversity of vertebrate hosts that flies fed on; 2) whether host feeding patterns varied in relation to type of hosts, tsetse feeding behaviour, site or tsetse age and sex; and 3) if there was a relationship between trypanosome detection and host feeding behaviours or host types. Methods: Sources of blood meals of Glossina pallidipes were identified by sequencing of the mitochondrial cytochrome b gene and analyzed in relationship with previously determined trypanosome detection in the same flies. Results: In an area dominated by wildlife but with seasonal presence of livestock (Nguruman), 98% of tsetse fed on single wild host species, whereas in an area including a mixture of resident domesticated animals, humans and wildlife (Shimba Hills), 52% of flies fed on more than one host species. Multiple Correspondence Analysis revealed strong correlations between feeding pattern, host type and site but these were resolved along a different dimension than trypanosome status, sex and age of the flies. Conclusions: Our results suggest that individual G. pallidipes in interface areas may show higher feeding success on wild hosts when available but often feed on both wild and domesticated hosts. This illustrates the importance of G. pallidipes as a vector connecting the sylvatic and domestic cycles of African trypanosomes.

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Blood meal analysis of tsetse flies (Glossina pallidipes: Glossinidae) reveals a reduction in host fidelity when feeding on domestic compared to wild hosts

10.1101/692053 ◽

2019 ◽

Author(s):

Manun Channumsin ◽

Marc Ciosi ◽

Dan Masiga ◽

Harriet Auty ◽

C. Michael Turner ◽

...

Keyword(s):

Host Species ◽

Glossina Pallidipes ◽

Domestic Animals ◽

Tsetse Flies ◽

Host Feeding ◽

African Trypanosomiasis ◽

Host Fidelity ◽

Mitochondrial Cytochrome B ◽

Single Host ◽

Wild Hosts

AbstractBackgroundBoth male and female tsetse flies, haematophagous insects, transmit trypanosomes between hosts and are the cyclical vectors for Human African Trypanosomiasis (HAT) and Animal African Trypanosomiasis (AAT). Trypanosomes responsible for AAT can be transmitted by tsetse between wild animals and livestock. However, the degree of connectivity between the sylvatic and domestic cycles is unknown. The objectives of this study were to investigate patterns of host feeding in relationship to trypanosome prevalence among Kenyan populations of G. pallidipes at the livestock-wildlife interface.Methodology/Principal FindingsSources of blood meals of Glossina pallidipes were identified by polymerase chain reaction amplification and sequencing of the mitochondrial cytochrome b gene and compared with previous characterization of trypanosome prevalence from the same flies. In the Nguruman region in southern Kenya, the majority (98%) of the 148 flies for which dominant hosts could be resolved fed on single host species and only a single fly had fed on a domestic host; intriguingly this was the only fly confirmed to have fed on cattle. In contrast, in the Shimba Hills region (South Coast), multiple host feeding was more common: 42% inside a fenced wildlife protected area, where 35% of dominant hosts were domestic animals or humans, compared with 62% from traps set along the border to an adjacent village, which was dominated by domestic hosts (77%). Across sites, 44% of flies tested positive for trypanosomes (28/50 domestic hosts; 78/193 wild hosts). Multiple Correspondence Analysis revealed strong correlations between feeding pattern, host type and site but these were resolved along a different dimension than trypanosome status.Conclusions/SignificanceOur results suggest that host fidelity when feeding on wild hosts in G. pallidipes could reduce risk of transmission of trypanosomes to domestic hosts in interface areas and emphasise the importance of considering vector behaviour when designing management interventions.Author SummaryTsetse flies are the main vectors transmitting trypanosomes, which cause disease in both humans and animals. Since tsetse flies feed on a wide range of vertebrate hosts, there is the potential for transmission between wild and domestic animals in regions where their ranges overlap. In this study, we used molecular methods to determine the hosts fed on by tsetse flies sampled from three sites in Kenya at the wildlife-livestock interface. In areas where wildlife dominated, tsetse tended to feed on single host species, whereas in areas with more domesticated animals, they tended to feed on multiple hosts. These results suggest either that tsetse flies get interrupted more while feeding on domestic hosts or that they prefer to feed on wildlife and so switch hosts more often when feeding on less desirable hosts. Using data from a previous study on the same samples, we found that trypanosome prevalence was not correlated with the type or number of hosts fed on. These results have important implications for understanding the risk of transmission between wildlife and livestock in regions bordering protected areas but the high host fidelity for wild hosts suggests that tsetse feeding preferences could reduce risks of disease transmission to livestock.

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Tsetse blood-meal sources, endosymbionts and trypanosome-associations in the Maasai Mara National Reserve, a wildlife-human-livestock interface

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0008267 ◽

2021 ◽

Vol 15 (1) ◽

pp. e0008267

Author(s):

Edward Edmond Makhulu ◽

Jandouwe Villinger ◽

Vincent Owino Adunga ◽

Maamun M. Jeneby ◽

Edwin Murungi Kimathi ◽

...

Keyword(s):

Blood Meal ◽

Glossina Pallidipes ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Buffalo ◽

African Trypanosomiasis ◽

African Trypanosomes ◽

Sodalis Glossinidius ◽

Vertebrate Hosts ◽

Blood Meals

African trypanosomiasis (AT) is a neglected disease of both humans and animals caused by Trypanosoma parasites, which are transmitted by obligate hematophagous tsetse flies (Glossina spp.). Knowledge on tsetse fly vertebrate hosts and the influence of tsetse endosymbionts on trypanosome presence, especially in wildlife-human-livestock interfaces, is limited. We identified tsetse species, their blood-meal sources, and correlations between endosymbionts and trypanosome presence in tsetse flies from the trypanosome-endemic Maasai Mara National Reserve (MMNR) in Kenya. Among 1167 tsetse flies (1136 Glossina pallidipes, 31 Glossina swynnertoni) collected from 10 sampling sites, 28 (2.4%) were positive by PCR for trypanosome DNA, most (17/28) being of Trypanosoma vivax species. Blood-meal analyses based on high-resolution melting analysis of vertebrate cytochrome c oxidase 1 and cytochrome b gene PCR products (n = 354) identified humans as the most common vertebrate host (37%), followed by hippopotamus (29.1%), African buffalo (26.3%), elephant (3.39%), and giraffe (0.84%). Flies positive for trypanosome DNA had fed on hippopotamus and buffalo. Tsetse flies were more likely to be positive for trypanosomes if they had the Sodalis glossinidius endosymbiont (P = 0.0002). These findings point to complex interactions of tsetse flies with trypanosomes, endosymbionts, and diverse vertebrate hosts in wildlife ecosystems such as in the MMNR, which should be considered in control programs. These interactions may contribute to the maintenance of tsetse populations and/or persistent circulation of African trypanosomes. Although the African buffalo is a key reservoir of AT, the higher proportion of hippopotamus blood-meals in flies with trypanosome DNA indicates that other wildlife species may be important in AT transmission. No trypanosomes associated with human disease were identified, but the high proportion of human blood-meals identified are indicative of human African trypanosomiasis risk. Our results add to existing data suggesting that Sodalis endosymbionts are associated with increased trypanosome presence in tsetse flies.

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Tsetse blood-meal sources, endosymbionts, and trypanosome infections provide insight into African trypanosomiasis transmission in the Maasai Mara National Reserve, a wildlife-human-livestock interface

10.1101/2020.04.06.027367 ◽

2020 ◽

Cited By ~ 1

Author(s):

Edward Edmond Makhulu ◽

Jandouwe Villinger ◽

Vincent Owino Adunga ◽

Maamun M. Jeneby ◽

Edwin Murungi Kimathi ◽

...

Keyword(s):

Blood Meal ◽

Vector Competence ◽

Glossina Pallidipes ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Buffalo ◽

African Trypanosomiasis ◽

Trypanosome Infection ◽

African Trypanosomes ◽

Blood Meals

AbstractBackgroundAfrican trypanosomiasis (AT) is a neglected disease of both humans and animals caused by Trypanosoma parasites, which are transmitted by obligate hematophagous tsetse flies (Glossina spp.). Understanding of AT transmission is hampered by limited knowledge on interactions of tsetse flies with their vertebrate hosts and the influence of endosymbionts on vector competence, especially in wildlife-human-livestock interfaces. We identified the tsetse species, their blood-meal sources, and the correlation between endosymbiont and trypanosome infection status in the trypanosome-endemic Maasai Mara National Reserve (MMNR) of Kenya.Methodology/Principal FindingsAmong 1167 tsetse flies (1136 Glossina pallidipes, 31 Glossina swynnertoni) collected from 10 sampling sites, 28 (2.4%) were positive by PCR for trypanosomes, majority (17/28) being Trypanosoma vivax. Blood-meal analyses based on high-resolution melting analysis of mitochondrial cytochrome c oxidase 1 and cytochrome b gene PCR products (n = 345) identified humans as the most common vertebrate host (37%), followed by hippopotamus (29.1%), African buffalo (26.3%), elephant (3.39%), and giraffe (0.84%). Trypanosome-infected flies had fed on hippopotamus and buffalo. Additionally, PCR analysis revealed that tsetse flies were more likely to be infected with trypanosomes if they were infected with the Sodalis glossinidius endosymbiont (P = 0.0022 Fisher’s exact test).Conclusions/SignificanceDiverse species of wildlife hosts may contribute to the maintenance of tsetse populations and/or persistent circulation of African trypanosomes in the MMNR. Although the African buffalo is known to be a key reservoir of AT, the higher proportion of hippopotamus blood-meals in trypanosomes-infected flies identified here indicates that other wildlife species may also be important to transmission cycles. No trypanosomes associated with human disease were identified, but the high proportion of human blood-meals identified are indicative of human African trypanosomiasis transmission risk. Furthermore, this work provides data showing that Sodalis endosymbionts can is associated with increased trypanosome infection rates in endemic ecologies.Author summaryHuman and animal African trypanosomiasis are neglected tropical diseases with potential to spread to new areas. Wild animals are important reservoirs for African trypanosomes and crucial in the emergence and re-emergence of AT. Vertebrate host-vector-parasite interactions are integral to trypanosome transmission. We investigated the vertebrate blood-meals and trypanosomes-endosymbionts co-infections in tsetse flies, which have been associated with reservoirs and vector competence, respectively, on AT transmission in Kenya’s Maasai Mara National Reserve. We identified tsetse fly diversity, trypanosome and endosymbiont infection status, and vertebrate blood-meal hosts to infer potential transmission dynamics. We found that Glossina pallidipes was the major tsetse fly vector and that Trypanosoma vivax was the main trypanosome species circulating in the region. Humans, hippopotamus, and buffalo were the most frequented for blood-meals. Buffalo and hippopotamus blood-meals were identified in trypanosome infected flies. Feeding of the flies on both humans and wildlife may potentiate the risk of the human trypanosomiasis in this ecology. Additionally, we found that the endosymbiont Sodalis glossinidius is associated with higher trypanosome infection rates in wild tsetse flies. These findings emphasize the importance of understanding the interaction of tsetse flies with vertebrate blood-meal sources and their endosymbionts in the transmission and control of AT.

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Insight into the Transmission Biology and Species-Specific Functional Capabilities of Tsetse (Diptera: Glossinidae) Obligate Symbiont Wigglesworthia

mBio ◽

10.1128/mbio.00240-11 ◽

2012 ◽

Vol 3 (1) ◽

Cited By ~ 59

Author(s):

Rita V. M. Rio ◽

Rebecca E. Symula ◽

Jingwen Wang ◽

Claudia Lohs ◽

Yi-neng Wu ◽

...

Keyword(s):

Transcriptional Regulation ◽

Host Species ◽

Tsetse Fly ◽

Sister Species ◽

Tsetse Flies ◽

Specific Gene ◽

Glossina Morsitans ◽

Content Type ◽

African Trypanosomes ◽

Species Specific

ABSTRACT Ancient endosymbionts have been associated with extreme genome structural stability with little differentiation in gene inventory between sister species. Tsetse flies (Diptera: Glossinidae) harbor an obligate endosymbiont, Wigglesworthia, which has coevolved with the Glossina radiation. We report on the ~720-kb Wigglesworthia genome and its associated plasmid from Glossina morsitans morsitans and compare them to those of the symbiont from Glossina brevipalpis. While there was overall high synteny between the two genomes, a large inversion was noted. Furthermore, symbiont transcriptional analyses demonstrated host tissue and development-specific gene expression supporting robust transcriptional regulation in Wigglesworthia, an unprecedented observation in other obligate mutualist endosymbionts. Expression and immunohistochemistry confirmed the role of flagella during the vertical transmission process from mother to intrauterine progeny. The expression of nutrient provisioning genes (thiC and hemH) suggests that Wigglesworthia may function in dietary supplementation tailored toward host development. Furthermore, despite extensive conservation, unique genes were identified within both symbiont genomes that may result in distinct metabolomes impacting host physiology. One of these differences involves the chorismate, phenylalanine, and folate biosynthetic pathways, which are uniquely present in Wigglesworthia morsitans. Interestingly, African trypanosomes are auxotrophs for phenylalanine and folate and salvage both exogenously. It is possible that W. morsitans contributes to the higher parasite susceptibility of its host species. IMPORTANCE Genomic stasis has historically been associated with obligate endosymbionts and their sister species. Here we characterize the Wigglesworthia genome of the tsetse fly species Glossina morsitans and compare it to its sister genome within G. brevipalpis. The similarity and variation between the genomes enabled specific hypotheses regarding functional biology. Expression analyses indicate significant levels of transcriptional regulation and support development- and tissue-specific functional roles for the symbiosis previously not observed in obligate mutualist symbionts. Retention of the genetically expensive flagella within these small genomes was demonstrated to be significant in symbiont transmission and tailored to the unique tsetse fly reproductive biology. Distinctions in metabolomes were also observed. We speculate an additional role for Wigglesworthia symbiosis where infections with pathogenic trypanosomes may depend upon symbiont species-specific metabolic products and thus influence the vector competence traits of different tsetse fly host species.

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Molecular characterization of pathogenic African trypanosomes in biting flies and camels in surra-endemic areas outside the tsetse fly belt in Kenya

10.1101/2020.06.18.156869 ◽

2020 ◽

Cited By ~ 1

Author(s):

Merid N. Getahun ◽

Jandouwe Villinger ◽

Joel L. Bargul ◽

Abel Orone ◽

John Ngiela ◽

...

Keyword(s):

Domestic Animals ◽

Trypanosoma Evansi ◽

Tsetse Fly ◽

16S Rrna Genes ◽

Rrna Genes ◽

Tsetse Flies ◽

Host Feeding ◽

Trypanosome Species ◽

African Trypanosomes ◽

Northern Kenya

AbstractBackgroundAfrican animal trypanosomosis is becoming prevalent beyond its traditionally defined geographical boundaries and is a threat to animals beyond the tsetse belts in and outside Africa. However, knowledge of infections with clinically important trypanosome species and their diversity among field-collected hematophagous biting flies and domestic animals is limited mainly to tsetse and their mammalian hosts in tsetse-infested areas. This study aimed to examine the presence of trypanosomes in both biting flies and domestic animals outside the tsetse belt in northern Kenya, potential mechanical vector species, and their host-feeding profiles.MethodsWe screened for pathogenic African trypanosomes in blood samples from domestic animals and field-trapped flies by microscopy and sequencing of internal transcribed spacer (ITS1) gene PCR products. We sequenced kinetoplast maxicircle genes to confirm Trypanosoma brucei detection and the RoTat 1.2 and kinetoplast minicircle genes to differentiate type-A and type-B Trypanosoma evansi, respectively. Further, we identified the hosts that field-trapped flies fed on by PCR-HRM and sequencing of 16S rRNA genes.ResultsHippobosca camelina, Stomoxys calcitrans, Tabanus spp., and Pangonia rueppellii are potential vectors of trypanosomes outside the tsetse belt in Marsabit County, northern Kenya. We identified Trypanosoma spp., including Trypanosoma vivax, T. evansi, T. brucei, and T. congolense in these biting flies as well as in camels (Camelus dromedarius). Trypanosomes detected varied from single up to three trypanosome species in H. camelina and camels in areas where no tsetse flies were trapped. Similar trypanosomes were detected in Glossina pallidipes collected from a tsetse-infested area in Shimba Hills, coastal Kenya, showing the wide geographic distribution of trypanosomes. Furthermore, we show that these biting flies acquired blood meals from camels, cattle, goats, and sheep. Phylogenetic analysis revealed diverse Trypanosoma spp. associated with variations in virulence and epidemiology in camels, which suggests that camel trypanosomosis may be due to mixed trypanosome infections rather than only surra (T. evansi), as previously thought.

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Slippery customers: How African trypanosomes evade mammalian defences

The Biochemist ◽

10.1042/bio03104008 ◽

2009 ◽

Vol 31 (4) ◽

pp. 8-11

Author(s):

Mark Carrington

Keyword(s):

Cell Biology ◽

Sub Saharan Africa ◽

Mammalian Host ◽

Tsetse Flies ◽

Insect Vector ◽

African Trypanosomiasis ◽

Long Distance ◽

African Trypanosomes ◽

Endemic Areas ◽

Sub Saharan

African trypanosomes are excellent parasites and can maintain an infection of a large mammalian host for months or years. In endemic areas, Human African Trypanosomiasis, also called sleeping sickness, has been largely unaffected by the advent of modern medicine, and trypanosomiasis of domestic livestock is a major restraint on productivity in endemic areas and is arguably the major contributor to the institutionalized poverty in much of rural sub-Saharan Africa1,2. A simple way of visualizing the effect of the livestock disease is to compare maps showing the distribution of livestock (www.ilri.org/InfoServ/Webpub/Fulldocs/Mappoverty/index.htm) and tsetse flies, the insect vector (www.fao.org/ag/AGAinfo/programmes/en/paat/maps.html): the lack of overlap is remarkable. Tsetse flies are only present in sub-Saharan Africa, and this probably restricted the spread of African trypanosomiasis until historical times. Livestock infections are now present in much of South Asia and South America, a product of long distance trade and adaptation of the trypanosomes to mechanical transmission3. The majority of research is on Trypanosoma brucei as this includes the human infective subspecies. This article provides a description of progress in the understanding the molecular details of how the trypanosome interacts with the mammalian immune system and how these studies have extended beyond this to fundamental aspects of eukaryotic cell biology.

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An update on the distribution of Glossina (tsetse flies) at the wildlife-human-livestock interface of Akagera National Park, Rwanda

Parasites & Vectors ◽

10.1186/s13071-021-04786-3 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Richard S. Gashururu ◽

Samuel M. Githigia ◽

Methode N. Gasana ◽

Richard Habimana ◽

Ndichu Maingi ◽

...

Keyword(s):

National Park ◽

Control Strategies ◽

Glossina Pallidipes ◽

Distribution Patterns ◽

Tsetse Flies ◽

Wet Season ◽

Chi Square ◽

Large Numbers ◽

Surrounding Areas ◽

Biconical Traps

Abstract Background Glossina (tsetse flies) biologically transmit trypanosomes that infect both humans and animals. Knowledge of their distribution patterns is a key element to better understand the transmission dynamics of trypanosomosis. Tsetse distribution in Rwanda has not been well enough documented, and little is known on their current distribution. This study determined the current spatial distribution, abundance, diversity, and seasonal variations of tsetse flies in and around the Akagera National Park. Methods A longitudinal stratified sampling following the seasons was used. Biconical traps were deployed in 55 sites for 6 consecutive days of each study month from May 2018 to June 2019 and emptied every 48 h. Flies were identified using FAO keys, and the number of flies per trap day (FTD) was used to determine the apparent density. Pearson chi-square (χ2) and parametrical tests (t-test and ANOVA) were used to determine the variations between the variables. The significance (p < 0.05) at 95% confidence interval was considered. Logistic regression was used to determine the association between tsetse occurrence and the associated predictors. Results A total of 39,516 tsetse flies were collected, of which 73.4 and 26.6% were from inside Akagera NP and the interface area, respectively. Female flies accounted for 61.3 while 38.7% were males. Two species were identified, i.e. G. pallidipes [n = 29,121, 7.4 flies/trap/day (FTD)] and G. morsitans centralis (n = 10,395; 2.6 FTD). The statistical difference in numbers was significant between the two species (p = 0.000). The flies were more abundant during the wet season (15.8 FTD) than the dry season (4.2 FTD). Large numbers of flies were trapped around the swamp areas (69.1 FTD) inside the park and in Nyagatare District (11.2 FTD) at the interface. Glossina morsitans was 0.218 times less likely to occur outside the park. The chance of co-existing between the two species reduced outside the protected area (0.021 times). Conclusions The occurrence of Glossina seems to be limited to the protected Akagera NP and a narrow band of its surrounding areas. This finding will be crucial to design appropriate control strategies. Glossina pallidipes was found in higher numbers and therefore is conceivably the most important vector of trypanosomosis. Regional coordinated control and regular monitoring of Glossina distribution are recommended. Graphic Abstract

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Detection ofTrypanosoma bruceiin Field-Captured Tsetse Flies and Identification of Host Species Fed on by the Infected Flies

Vector-Borne and Zoonotic Diseases ◽

10.1089/vbz.2007.0223 ◽

2008 ◽

Vol 8 (4) ◽

pp. 565-574 ◽

Cited By ~ 5

Author(s):

Satoru Konnai ◽

Hirohisa Mekata ◽

Raadan Odbileg ◽

Martin Simuunza ◽

Mwelwa Chembensof ◽

...

Keyword(s):

Host Species ◽

Tsetse Flies

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Comparative performance of traps in catching tsetse flies (Diptera: Glossinidae) in Tanzania

Onderstepoort Journal of Veterinary Research ◽

10.4102/ojvr.v83i1.1057 ◽

2016 ◽

Vol 83 (1) ◽

Cited By ~ 5

Author(s):

Imna I. Malele ◽

Johnson O. Ouma ◽

Hamisi S. Nyingilili ◽

Winston A. Kitwika ◽

Deusdedit J. Malulu ◽

...

Keyword(s):

Glossina Pallidipes ◽

Abundant Species ◽

Tsetse Fly ◽

Tsetse Flies ◽

Comparative Performance ◽

Control Programmes ◽

Fly Control ◽

Tsetse Fly Control ◽

Species Being ◽

Biconical Traps

This study was conducted to determine the efficiency of different tsetse traps in 28 sites across Tanzania. The traps used were biconical, H, NGU, NZI, pyramidal, S3, mobile, and sticky panels. Stationary traps were deployed at a distance of 200 m apart and examined 72 h after deployment. The results showed that 117 (52.2%) out of the 224 traps deployed captured at least one Glossina species. A total of five Glossina species were captured, namely Glossina brevipalpis, Glossina pallidipes, Glossina swynnertoni, Glossina morsitans, and Glossina fuscipes martinii. Biconical traps caught tsetse flies in 27 sites, pyramidal in 26, sticky panel in 20, mobile in 19, S3 in 15, NGU in 7, H in 2 and NZI in 1. A total of 21 107 tsetse flies were trapped, with the most abundant species being G. swynnertoni (55.9%), followed by G. pallidipes (31.1%), G. fuscipes martinii (6.9%) and G. morsitans (6.0%). The least caught was G. brevipalpis (0.2%). The highest number of flies were caught by NGU traps (32.5%), followed by sticky panel (16%), mobile (15.4%), pyramidal (13.0%), biconical (11.3%) and S3 (10.2%). NZI traps managed to catch 0.9% of the total flies and H traps 0.7%. From this study, it can be concluded that the most efficient trap was NGU, followed by sticky panel and mobile, in that order. Therefore, for tsetse fly control programmes, NGU traps could be the better choice. Conversely, of the stationary traps, pyramidal and biconical traps captured tsetse flies in the majority of sites, covering all three ecosystems better than any other traps; therefore, they would be suitable for scouting for tsetse infestation in any given area, thus sparing the costs of making traps for each specific Glossina species.Keywords: tseste; traps; densties; Glossina; mobile; stationary; Tanzania

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Aircraft Applications of Insecticides in East Africa. VI.—Applications of a coarse Aerosol containning DDT to control the Tsetse Flies, Glossina morsitans Westw., Glossina swynnertoni Aust. and Glossina pallidipes Aust.

Bulletin of Entomological Research ◽

10.1017/s0007485300029655 ◽

1954 ◽

Vol 45 (3) ◽

pp. 585-603 ◽

Cited By ~ 11

Author(s):

K. S. Hocking ◽

D. Yeo ◽

D. G. Anstey

Keyword(s):

Random Effects ◽

Glossina Pallidipes ◽

Tsetse Flies ◽

Glossina Morsitans ◽

Median Diameter ◽

Coarse Aerosol ◽

Savannah Woodland ◽

Mass Median ◽

Glossina Swynnertoni ◽

Mass Median Diameter

An experiment is described where applications of a coarse aerosol were made to savannah woodland containing the tsetse flies, Glossina moritans Westw., G. swynnertoni Aust. and G. pallidipes Aust.Seven applications were made, each at a nominal dosage of 0·25 lb. of technical DDT per acre and 0·25 gallons of solution per acre. The applications in any particular part of the treaed woodland covered an interval of 90 days, or rather more than two pupal periods.The coarse aerosol was produced by emitting the insecticidal solution under pressure through fine nozzles fitted to a boom. It had a mass median diameter of approximately 60 microns, and droplet dismeters varied from a few microns to approximately 200 microns.The population of G. pallidipes was so drastically reduced that it has subsequently dies out. The reduction of G. morsitans was approximately 95 per cent. The differences between the reductions are attributed mainly to differences between the ease with which the three species can be killed. It is pointed out that this is not necessarily equivalent to differences in susceptibility.Comparisons are made with previous experiments, and the different results of the various experiments are difficult to explian satisfactory. The increased cover in savannah areas during the leafy period may have reduced the effectiveness of the applications, and the total periods covered by the various series of applications were probably also important. Random effects, leading to ineffective treatments, may also be important.Costs are discussed.

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