Modelling the effects of temperature change on the dynamics of tsetse flies and trypanosomiasis disease transmission

Mthombothi, Zinhle Emily (2018-03)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT : Global temperatures have increased over recent decades. This is expected to have an impact on vector-borne diseases, raising questions such as: Will the increased temperature result in changing disease prevalence? How will vector populations be affected in terms of their density and distribution? It has been suggested that African trypanosomiasis, a zoonotic disease transmitted by tsetse flies, will exhibit increased incidence, and expand its geographical range, due to increasing temperatures. This project uses mathematical modelling to assess the impact of temperature change on tsetse fly population dynamics. Understanding these impacts could help us understand how trypanosomiasis transmission dynamics will be affected by global warming. We develop a temperaturedependent ordinary differential equations (ODE) model to model the growth in the numbers of pupal and adult tsetse. We fit the model to data on the number of tsetse flies (Glossina pallidipes Austen) on Antelope Island, Zimbabwe, between 5 February 1980 and 29 December 1981, estimated using mark recapture. The findings from this project concur with previous studies suggesting that temperature is the most important factor determining the growth of tsetse populations. There appears, however, to be another factor, cycling annually, approximately in phase with the Normalised Difference Vegetation Index (NDVI), which also influences the survival of adult flies. Our findings show that minor changes in temperature have a big impact on tsetse population growth rates. In conclusion, our model suggests that high temperatures could give rise, at least, to local extinctions of tsetse populations.

AFRIKAANSE OPSOMMING : Temperature het wêreldwyd oor die afgelope dekades toegeneem. Dit sal na verwagting ’n impak op vektor-oordraagbare siektes hê, wat tot vrae lei soos: Sal die verhoogde temperature verandering in die voorkoms van siektes tot gevolg bring? Hoe sal vektorbevolkings geraak word in terme van hul digtheid en verspreiding? Daar is voorgestel dat die voorkoms van Afrika-trypanosomiasis, ’n zoönotiese siekte wat deur tsetsevlieë oorgedra word, sal toeneem en die geografiese omvang daarvan sal uitbrei as gevolg van toenemende temperature. Hierdie projek gebruik wiskundige modellering om die impak van temperatuurverandering op tsetsevlieg-bevolkingsdinamika te bepaal. Deur hierdie verband te verstaan, kan ons help om te beskryf hoe die oordrag-dinamika van trypanosomiasis deur globale verwarming beïnvloed sal word. Ons ontwikkel ’n temperatuurafhanklike gewone differensiaalvergelyking (ODE) model om die groei in die aantal pupale en volwasse tsetsevlieë te modelleer. Ons gebruik data van aantal tsetsevlieë om die model te pas. Hierdie data, van die spesie Glossina pallidipes Austen, is versamel op Antelope-eiland, Zimbabwe, tussen 5 Februarie 1980 en 29 Desember 1981, deur gebruik te maak van die "mark recapture" metode. Die bevindinge van hierdie projek stem ooreen met vorige studies wat daarop dui dat temperatuur die belangrikste faktor is in die toename in tsetse populasies. Daar blyk egter nog ’n jaarlikse sikliese faktor te wees, ongeveer in fase met die genormaliseerde verskil in plantegroei indeks (NDVI), wat ook die oorlewing van volwasse vlieë beïnvloed. Ons bevindinge toon dat geringe temperatuurveranderinge ’n groot impak het op tsetse-bevolkingsgroeikoerse. Ten slotte stel ons model voor dat hoë temperature ten minste tot plaaslike uitwissings van tsetsebevolkings kan lei.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103510
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