1
|
Assessing the effect of insecticide-treated cattle on tsetse abundance and trypanosome transmission at the wildlife-livestock interface in Serengeti, Tanzania. PLoS Negl Trop Dis 2020; 14:e0008288. [PMID: 32841229 PMCID: PMC7473525 DOI: 10.1371/journal.pntd.0008288] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/04/2020] [Accepted: 07/13/2020] [Indexed: 11/19/2022] Open
Abstract
In the absence of national control programmes against Rhodesian human African trypanosomiasis, farmer-led treatment of cattle with pyrethroid-based insecticides may be an effective strategy for foci at the edges of wildlife areas, but there is limited evidence to support this. We combined data on insecticide use by farmers, tsetse abundance and trypanosome prevalence, with mathematical models, to quantify the likely impact of insecticide-treated cattle. Sixteen percent of farmers reported treating cattle with a pyrethroid, and chemical analysis indicated 18% of individual cattle had been treated, in the previous week. Treatment of cattle was estimated to increase daily mortality of tsetse by 5–14%. Trypanosome prevalence in tsetse, predominantly from wildlife areas, was 1.25% for T. brucei s.l. and 0.03% for T. b. rhodesiense. For 750 cattle sampled from 48 herds, 2.3% were PCR positive for T. brucei s.l. and none for T. b. rhodesiense. Using mathematical models, we estimated there was 8–29% increase in mortality of tsetse in farming areas and this increase can explain the relatively low prevalence of T. brucei s.l. in cattle. Farmer-led treatment of cattle with pyrethroids is likely, in part, to be limiting the spill-over of human-infective trypanosomes from wildlife areas. The acute form of sleeping sickness in Africa is caused by the parasite Trypanosoma brucei rhodesiense. It is transmitted by tsetse flies and can be maintained in cycles involving both livestock and wildlife as hosts. Humans are incidentally infected and are particularly at risk of infection near protected areas where there is both wildlife and suitable habitat for tsetse. In these regions, the tsetse vector cannot be eradicated, nor can infection be prevented in wildlife. Here we use field studies of tsetse and livestock in combination with mathematical models of tsetse population change and trypanosome transmission to show that use of pyrethroid-based insecticides on cattle–by farmers at the edge of protected areas–could be contributing to lowering the risk of sleeping sickness in Serengeti District, Tanzania. To our knowledge, our study is the first to report farmer-led tsetse control, co-incident with tsetse decline and relatively low prevalence of T. brucei s.l. in cattle.
Collapse
|
2
|
Blood meal sources and bacterial microbiome diversity in wild-caught tsetse flies. Sci Rep 2020; 10:5005. [PMID: 32193415 PMCID: PMC7081217 DOI: 10.1038/s41598-020-61817-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 02/28/2020] [Indexed: 12/02/2022] Open
Abstract
Tsetse flies are the vectors of African trypanosomiasis affecting 36 sub-Saharan countries. Both wild and domestic animals play a crucial role in maintaining the disease-causing parasites (trypanosomes). Thus, the identification of animal reservoirs of trypanosomes is vital for the effective control of African trypanosomiasis. Additionally, the biotic and abiotic factors that drive gut microbiome diversity in tsetse flies are primarily unresolved, especially under natural, field conditions. In this study, we present a comprehensive DNA metabarcoding approach for individual tsetse fly analysis in the identification of mammalian blood meal sources and fly bacterial microbiome composition. We analyzed samples from two endemic foci, Kafue, Zambia collected in June 2017, and Hurungwe, Zimbabwe sampled in April 2014 (pilot study) and detected DNA of various mammals including humans, wild animals, domestic animals and small mammals (rat and bat). The bacterial diversity was relatively similar in flies with different mammalian species DNA, trypanosome infected and uninfected flies, and female and male flies. This study is the first report on bat DNA detection in wild tsetse flies. This study reveals that small mammals such as bats and rats are among the opportunistic blood meal sources for tsetse flies in the wild, and the implication on tsetse biology and ecology needs to be studied.
Collapse
|
3
|
Lipoproteins from vertebrate host blood plasma are involved in Trypanosoma cruzi epimastigote agglutination and participate in interaction with the vector insect, Rhodnius prolixus. Exp Parasitol 2018; 195:24-33. [DOI: 10.1016/j.exppara.2018.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 08/14/2018] [Accepted: 09/23/2018] [Indexed: 01/30/2023]
|
4
|
Ahmed HA, MacLeod ET, Welburn SC, Picozzi K. Development of real time PCR to study experimental mixed infections of T. congolense Savannah and T. b. brucei in Glossina morsitans morsitans. PLoS One 2015; 10:e0117147. [PMID: 25738803 PMCID: PMC4349444 DOI: 10.1371/journal.pone.0117147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 12/18/2014] [Indexed: 11/18/2022] Open
Abstract
Tsetse flies are able to acquire mixed infections naturally or experimentally either simultaneously or sequentially. Traditionally, natural infection rates in tsetse flies are estimated by microscopic examination of different parts of the fly after dissection, together with the isolation of the parasite in vivo. However, until the advent of molecular techniques it was difficult to speciate trypanosomes infections and to quantify trypanosome numbers within tsetse flies. Although more expensive, qPCR allows the quantification of DNA and is less time consuming due to real time visualization and validation of the results. The current study evaluated the application of qPCR to quantify the infection load of tsetse flies with T. b. brucei and T. congolense savannah and to study the possibility of competition between the two species. The results revealed that the two qPCR reactions are of acceptable efficiency (99.1% and 95.6%, respectively), sensitivity and specificity and can be used for quantification of infection load with trypanosomes in experimentally infected Glossina morsitans morsitans. The mixed infection of laboratory Glossina species and quantification of the infection suggests the possibility that a form of competition exists between the isolates of T. b. brucei and T. congolense savannah that we used when they co-exist in the fly midgut.
Collapse
Affiliation(s)
- Heba A. Ahmed
- Division of Pathway Medicine, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
- Faculty of Veterinary Medicine, Zagazig University, Zagazig, Ash Sharqiyah, Egypt
| | - Ewan T. MacLeod
- Division of Pathway Medicine, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Susan C. Welburn
- Division of Pathway Medicine, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Kim Picozzi
- Division of Pathway Medicine, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
| |
Collapse
|
5
|
Goossens B, Mbwambo H, Msangi A, Geysen D, Vreysen M. Trypanosomosis prevalence in cattle on Mafia Island (Tanzania). Vet Parasitol 2006; 139:74-83. [PMID: 16574325 DOI: 10.1016/j.vetpar.2006.02.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 02/10/2006] [Accepted: 02/21/2006] [Indexed: 11/21/2022]
Abstract
During two consecutive surveys (February and August/Sept 2002), a total of 970 cattle from the cattle population of Mafia Island (United Republic of Tanzania) were blood-sampled. All blood samples were microscopically screened for the presence of trypanosomes and a portion of these were checked for antibodies with an Ab-ELISA and for the presence of trypanosomal DNA with PCR. Microscopic evidence of trypanosomes of the congolense group (sub-genus Nannomonas) was found in 0.8% of the animals (8/970) and in two cases the species identified was confirmed by PCR as Trypanosoma congolense savannah type. Non-pathogenic Trypanosoma theileri were detected in 3.2% (31/970) of the samples using the Dark Ground-Buffy Coat (DG-BC) technique. For survey 1 (S1), detection of antibodies (Ab-ELISA) against pathogenic trypanosomes indicated a seroprevalence of 14.2% (68/480). Of the samples, either DG positive or with a PCV lower then 25, examined by PCR, a total of 8.4% (5/59) (selected from 970 samples), were found positive for T. congolense. The low prevalence of pathogenic trypanosomes on Mafia Island is intriguing, especially in view of the omnipresence of the tsetse fly Glossina brevipalpis. Although the presence of detected trypanosomal antibodies does not necessarily indicate a current infection, the combination of serological/parasitological examinations and the results of the PCR do support this low prevalence of trypanosomosis in cattle. Despite the low prevalence, pathogenic trypanosomes are present on Mafia Island and possible reasons for this low infection rate, taking account of the relation between Glossina species present, transmission risk and trypanosomes found in cattle, are discussed also in view of a future appropriate intervention strategy.
Collapse
Affiliation(s)
- B Goossens
- European Food Safety Authority, BSE Unit, Largo N. Palli 5/A, I-43100 Parma, Italy.
| | | | | | | | | |
Collapse
|
6
|
Zongo I, Mbahin N, van den Abbeele J, De Deken R, van den Bossche P. Comparison of the infection rate of tsetse, Glossina morsitans morsitans, fed in vitro or in vivo. MEDICAL AND VETERINARY ENTOMOLOGY 2004; 18:64-66. [PMID: 15009448 DOI: 10.1111/j.1365-2915.2004.0474.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Studies were made of infection rates of trypanosomes in the tsetse fly Glossina morsitans morsitans Westwood (Diptera: Glossinidae) when maintained in vivo (rabbits) or in vitro on high quality, gamma-irradiated, sterile defibrinated bovine blood, obtained from the Entomology Unit of the International Atomic Energy Agency (IAEA). For both Trypanosoma congolense Broden and T. b. brucei Plimmer & Bradford, in vitro maintenance significantly reduced the proportion of flies that developed mature metacyclic trypanosome infections.
Collapse
Affiliation(s)
- I Zongo
- Veterinary Department, Institute of Tropical Medicine, Antwerp, Belgium
| | | | | | | | | |
Collapse
|
7
|
Aksoy S, Gibson WC, Lehane MJ. Interactions between tsetse and trypanosomes with implications for the control of trypanosomiasis. ADVANCES IN PARASITOLOGY 2003; 53:1-83. [PMID: 14587696 DOI: 10.1016/s0065-308x(03)53002-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Tsetse flies (Diptera: Glossinidae) are vectors of several species of pathogenic trypanosomes in tropical Africa. Human African trypanosomiasis (HAT) is a zoonosis caused by Trypanosoma brucei rhodesiense in East Africa and T. b. gambiense in West and Central Africa. About 100000 new cases are reported per year, with many more probably remaining undetected. Sixty million people living in 36 countries are at risk of infection. Recently, T. b. gambiense trypanosomiasis has emerged as a major public health problem in Central Africa, especially in the Democratic Republic of Congo, Angola and southern Sudan where civil war has hampered control efforts. African trypanosomes also cause nagana in livestock. T. vivax and T. congolense are major pathogens of cattle and other ruminants, while T. simiae causes high mortality in domestic pigs; T. brucei affects all livestock, with particularly severe effects in equines and dogs. Central to the control of these diseases is control of the tsetse vector, which should be very effective since trypanosomes rely on this single insect for transmission. However, the area infested by tsetse has increased in the past century. Recent advances in molecular technologies and their application to insects have revolutionized the field of vector biology, and there is hope that such new approaches may form the basis for future tsetse control strategies. This article reviews the known biology of trypanosome development in the fly in the context of the physiology of the digestive system and interactions of the immune defences and symbiotic flora.
Collapse
Affiliation(s)
- Serap Aksoy
- Department of Epidemiology and Public Health, Section of Vector Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | | | | |
Collapse
|
8
|
Masaninga F, Mihok S. Host influence on adaptation of Trypanosoma congolense metacyclics to vertebrate hosts. MEDICAL AND VETERINARY ENTOMOLOGY 1999; 13:330-332. [PMID: 10514061 DOI: 10.1046/j.1365-2915.1999.00151.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Affiliation(s)
- F Masaninga
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | |
Collapse
|
9
|
Nguu EK, Osir EO, Imbuga MO, Olembo NK. The effect of host blood in the in vitro transformation of bloodstream trypanosomes by tsetse midgut homogenates. MEDICAL AND VETERINARY ENTOMOLOGY 1996; 10:317-322. [PMID: 8994132 DOI: 10.1111/j.1365-2915.1996.tb00751.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Midgut homogenates prepared from Glossina morsitans morsitans, that had previously been fed on different host blood samples, were tested for their abilities to transform bloodstream Trypanosoma brucei into procyclic (midgut) forms in vitro. Compared to rat and goat blood samples, eland blood had the least capacity to support trypanosome transformation, whereas buffalo blood showed intermediate capacity. Fractionation of rat blood showed the importance of the cellular portion since both rat and eland red blood cells (RBCs) supported the process. Virtually no transformation was observed in rat and eland plasma or serum fractions. Suspending rat blood cells in eland plasma led to a reduction in parasite transformation rates. Further experiments showed that the RBC membranes were also capable of supporting the process. These results clearly show the important role played by blood, especially the red blood cells, in the transformation of bloodstream trypanosomes. In addition, the low transformation rates observed in eland blood is due to an inhibitory factor(s) present in the plasma fraction.
Collapse
Affiliation(s)
- E K Nguu
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | |
Collapse
|
10
|
Mihok S, Machika C, Darji N, Kang'ethe EK, Otieno LH. Relationships between host blood factors and proteases in Glossina morsitans subspecies infected with Trypanosoma congolense. MEDICAL AND VETERINARY ENTOMOLOGY 1995; 9:155-160. [PMID: 7787223 DOI: 10.1111/j.1365-2915.1995.tb00172.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Host blood effects on Trypanosoma congolense establishment in Glossina morsitans morsitans and Glossina morsitans centralis were investigated using goat, rabbit, cow and rhinoceros blood. Meals containing goat erythrocytes facilitated infection in G.m.morsitans, whereas meals containing goat plasma facilitated infection in G.m.centralis. Goat blood effects were not observed in the presence of complementary rabbit blood components. N-acetyl-glucosamine (a midgut-lectin inhibitor) increased infection rates in some, but not all, blood manipulations. Cholesterol increased infection rates in G.m.centralis only. Both compounds together added to cow blood produced superinfection in G.m.centralis, but not in G.m.morsitans. Midgut protease levels did not differ 6 days post-infection in flies maintaining infections versus flies clearing infections. Protease levels were weakly correlated with patterns of infection, but only in G.m.morsitans. These results suggest that physiological mechanisms responsible for variation in infection rates are only superficially similar in these closely-related tsetse.
Collapse
Affiliation(s)
- S Mihok
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | | | |
Collapse
|
11
|
Mihok S, Zweygarth E, Munyoki EN, Wambua J, Kock R. Trypanosoma simiae in the white rhinoceros (Ceratotherium simum) and the dromedary camel (Camelus dromedarius). Vet Parasitol 1994; 53:191-6. [PMID: 7975114 DOI: 10.1016/0304-4017(94)90182-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Trypanosoma simiae was identified as the cause of a disease outbreak in dromedary camels (Camelus dromedarius) introduced to Tsavo East National Park, confirming the susceptibility of camels to this pathogen. T. simiae was also isolated from a new host, the white rhinoceros (Ceratotherium simum) through xenodiagnosis with a susceptible tsetse species (Glossina morsitans centralis). A white rhinoceros showed some evidence of anaemia and lymphopaenia when harbouring T. simiae, but did not suffer any long-term health effects.
Collapse
Affiliation(s)
- S Mihok
- Livestock Pests Research Programme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | | | |
Collapse
|
12
|
Mihok S, Munyoki EN, Masaninga F, Ndegwa PN, Olubayo RO. Isolation of Trypanosoma spp. from wild tsetse flies through procyclic expansion in Glossina morsitans centralis. Acta Trop 1994; 56:25-37. [PMID: 8203293 DOI: 10.1016/0001-706x(94)90037-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Procyclic trypanosomes from wild tsetse flies were membrane-fed to Glossina morsitans centralis in order to develop an optimal technique for propagating field isolates. A 70% success rate was achieved in isolating Trypanosoma simiae and a variety of genotypes of T. congolense originating from G. pallidipes, G. brevipalpis and G. swynnertoni. Parasites matured into forms infective for mammals, and could be maintained by passage of gut forms to new groups of flies. In experiments with laboratory stocks, we also passaged immature gut infections of T. congolense and T. brucei from various tsetse species to G. m. centralis. The optimal technique was investigated for procyclic T. congolense through addition of various compounds to goat blood using G. m. centralis and G. m. morsitans as recipients. From these experiments, many approaches to procyclic expansion appeared possible. However, a simple and practical method based on the use of fresh goat blood for rapid feeding of G. m. centralis is recommended. Application of this technique should aid in the resolution of questions relating to the cryptic diversity of Nannomonas trypanosomes in diverse host and vector communities.
Collapse
Affiliation(s)
- S Mihok
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | | | |
Collapse
|
13
|
Olubayo RO, Mihok S, Munyoki E, Otieno LH. Dynamics of host blood effects in Glossina morsitans sspp. infected with Trypanosoma congolense and T. brucei. Parasitol Res 1994; 80:177-81. [PMID: 8036228 DOI: 10.1007/bf00932670] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The pattern of infection in Glossina morsitans morsitans and G. m. centralis membrane-fed on eland, buffalo or goat blood mixed with Trypanosoma congolense or T. brucei was studied from day 1 to day 10. Tsetse were initially permissive vectors, with most flies harbouring infections of 10(4)-10(5) parasites on day 3. However, after a second blood meal on day 3, flies cleared many infections, with G. m. morsitans clearing more infections than G.m. centralis. Infective feeds of goat blood consistently increased final infection rates by limiting the number of infections lost between days 3 and 6. In further experiments with G. m. morsitans only, this effect was replicated by feeding flies on erythrocytes but not on serum. These results suggest that compounds from some mammalian erythrocytes match the target specificity of G. m. morsitans midgut lectins and, hence, have a protective effect on trypanosome establishment in the fly.
Collapse
Affiliation(s)
- R O Olubayo
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | |
Collapse
|
14
|
Mihok S, Stiles JK, Mpanga E, Olubayo RO. Relationships between protease activity, host blood and infection rates in Glossina morsitans sspp. infected with Trypanosoma congolense, T. brucei and T. simiae. MEDICAL AND VETERINARY ENTOMOLOGY 1994; 8:47-50. [PMID: 8161844 DOI: 10.1111/j.1365-2915.1994.tb00383.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Midgut protease activity in Glossina morsitans centralis and G.m. morsitans, at 48 h post bloodmeal averaged 1.8IU of trypsin-like activity. These two tsetse subspecies differ in their susceptibility to trypanosome infection. Except for low levels in flies fed on waterbuck blood (0.7 IU), activity did not differ in flies fed a variety of host bloods (goat, pig, cow, buffalo, eland) and trypanosome species (Trypanosoma congolense, T. brucei, T. simiae). Protease activity was also not correlated with infection rates, despite large differences in infection rates among experiments. Nevertheless, addition of 0.06 M D(+)-glucosamine to parasitaemic blood resulted in a three-fold reduction in protease activity, coincident with a large increase in infection rate. This effect did not occur when parasites or D(+)-glucosamine were added alone to the bloodmeal, suggesting that the effect was due to metabolism of D(+)-glucosamine by parasites.
Collapse
Affiliation(s)
- S Mihok
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | | | | |
Collapse
|