Ochanda, Horace (1994) Factors affecting the population dynamics of Theileria parva in rhipicephalid ticks. PhD thesis, University of Warwick.

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Abstract

A series of experiments were carried out to investigate some of the poorly understood
aspects of the life cycle of Theilefid parva in its rhipicephalid tick vectors. The first
series of experiments established that nymphae infected as larvae develop lower levels
of infection compared to adults infected as nymphae, while female ticks develop
higher infections than males. It was shown that the period of development of
sporoblasts into mature sporozoites took on average four days in the nyrnphal ticks
compared to five days in the adult ticks. Infection levels developing in different tick
instars or sexes appeared to be related to the number and position of type III salivary
gland acini. The second series of experiments established that there were considerable
differences in the vector competence of different stocks of Rhipicephalus
appendiculatus and R. zambeziensis for the transmission of Muguga and Boleni stocks
of Yheileria parva. Finally the study established that survival of infected R.
appendiculatus and the T parva they harboured was longer under quasi-natural
climatic conditions compared to all the laboratory conditions examined. Basically,
infection levels in the ticks did not affect the duration of survival of the ticks,
however, survival of the parasite appeared to be influenced by the intensity of
infection in the tick as the parasites diminished more rapidly in ticks having high
infections than in those having low infections. Nymphae and the parasites they
harboured survived for shorter periods compared to the adult ticks and their infections.
Data generated from these series of experiments will be used to develop quantitative
models of T parva dynamics in the tick vectors.
The relative importance of the factors influencing the levels of infection developing in
the tick vector were analysed statistically by the logistic and Poisson regression.
Factors found to play a significant role included tick instar or gender, tick stock,
parasite stock, the ambient climatic conditions in which infected ticks survived and the
day of tick repletion after infection of the bovine host. Individually, the bovine host or
its piroplasm parasitaernia were found to be poor predictors of infection levels
developing in the salivary glands of the tick vector. However, when piroplasm
parasitaernia was included in a model lacking the days post-repletion variable, the
bovine host factor became significant.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QL Zoology
Library of Congress Subject Headings (LCSH):	Theileria parva, Rhipicephalus, Virus-vector relationships, Invertebrates as carriers of disease
Official Date:	October 1994
Dates:	Date Event October 1994 Submitted
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Medley, Graham
Sponsors:	International Laboratory for Research on Animal Diseases (ILRAD)
Extent:	xiv, 197 p.
Language:	eng

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